WorldWideScience

Sample records for adaptive optics scanning

  1. Adaptive Optical Scanning Holography

    Science.gov (United States)

    Tsang, P. W. M.; Poon, Ting-Chung; Liu, J.-P.

    2016-01-01

    Optical Scanning Holography (OSH) is a powerful technique that employs a single-pixel sensor and a row-by-row scanning mechanism to capture the hologram of a wide-view, three-dimensional object. However, the time required to acquire a hologram with OSH is rather lengthy. In this paper, we propose an enhanced framework, which is referred to as Adaptive OSH (AOSH), to shorten the holographic recording process. We have demonstrated that the AOSH method is capable of decreasing the acquisition time by up to an order of magnitude, while preserving the content of the hologram favorably. PMID:26916866

  2. Adaptive optics scanning ophthalmoscopy with annular pupils.

    Science.gov (United States)

    Sulai, Yusufu N; Dubra, Alfredo

    2012-07-01

    Annular apodization of the illumination and/or imaging pupils of an adaptive optics scanning light ophthalmoscope (AOSLO) for improving transverse resolution was evaluated using three different normalized inner radii (0.26, 0.39 and 0.52). In vivo imaging of the human photoreceptor mosaic at 0.5 and 10° from fixation indicates that the use of an annular illumination pupil and a circular imaging pupil provides the most benefit of all configurations when using a one Airy disk diameter pinhole, in agreement with the paraxial confocal microscopy theory. Annular illumination pupils with 0.26 and 0.39 normalized inner radii performed best in terms of the narrowing of the autocorrelation central lobe (between 7 and 12%), and the increase in manual and automated photoreceptor counts (8 to 20% more cones and 11 to 29% more rods). It was observed that the use of annular pupils with large inner radii can result in multi-modal cone photoreceptor intensity profiles. The effect of the annular masks on the average photoreceptor intensity is consistent with the Stiles-Crawford effect (SCE). This indicates that combinations of images of the same photoreceptors with different apodization configurations and/or annular masks can be used to distinguish cones from rods, even when the former have complex multi-modal intensity profiles. In addition to narrowing the point spread function transversally, the use of annular apodizing masks also elongates it axially, a fact that can be used for extending the depth of focus of techniques such as adaptive optics optical coherence tomography (AOOCT). Finally, the positive results from this work suggest that annular pupil apodization could be used in refractive or catadioptric adaptive optics ophthalmoscopes to mitigate undesired back-reflections.

  3. Adaptive optics parallel near-confocal scanning ophthalmoscopy.

    Science.gov (United States)

    Lu, Jing; Gu, Boyu; Wang, Xiaolin; Zhang, Yuhua

    2016-08-15

    We present an adaptive optics parallel near-confocal scanning ophthalmoscope (AOPCSO) using a digital micromirror device (DMD). The imaging light is modulated to be a line of point sources by the DMD, illuminating the retina simultaneously. By using a high-speed line camera to acquire the image and using adaptive optics to compensate the ocular wave aberration, the AOPCSO can image the living human eye with cellular level resolution at the frame rate of 100 Hz. AOPCSO has been demonstrated with improved spatial resolution in imaging of the living human retina compared with adaptive optics line scan ophthalmoscopy.

  4. Adaptive optics parallel near-confocal scanning ophthalmoscopy.

    Science.gov (United States)

    Lu, Jing; Gu, Boyu; Wang, Xiaolin; Zhang, Yuhua

    2016-08-15

    We present an adaptive optics parallel near-confocal scanning ophthalmoscope (AOPCSO) using a digital micromirror device (DMD). The imaging light is modulated to be a line of point sources by the DMD, illuminating the retina simultaneously. By using a high-speed line camera to acquire the image and using adaptive optics to compensate the ocular wave aberration, the AOPCSO can image the living human eye with cellular level resolution at the frame rate of 100 Hz. AOPCSO has been demonstrated with improved spatial resolution in imaging of the living human retina compared with adaptive optics line scan ophthalmoscopy. PMID:27519106

  5. Digital adaptive optics line-scanning confocal imaging system

    Science.gov (United States)

    Liu, Changgeng; Kim, Myung K.

    2015-11-01

    A digital adaptive optics line-scanning confocal imaging (DAOLCI) system is proposed by applying digital holographic adaptive optics to a digital form of line-scanning confocal imaging system. In DAOLCI, each line scan is recorded by a digital hologram, which allows access to the complex optical field from one slice of the sample through digital holography. This complex optical field contains both the information of one slice of the sample and the optical aberration of the system, thus allowing us to compensate for the effect of the optical aberration, which can be sensed by a complex guide star hologram. After numerical aberration compensation, the corrected optical fields of a sequence of line scans are stitched into the final corrected confocal image. In DAOLCI, a numerical slit is applied to realize the confocality at the sensor end. The width of this slit can be adjusted to control the image contrast and speckle noise for scattering samples. DAOLCI dispenses with the hardware pieces, such as Shack-Hartmann wavefront sensor and deformable mirror, and the closed-loop feedbacks adopted in the conventional adaptive optics confocal imaging system, thus reducing the optomechanical complexity and cost. Numerical simulations and proof-of-principle experiments are presented that demonstrate the feasibility of this idea.

  6. Adaptive optics scanning laser ophthalmoscope imaging: technology update

    Directory of Open Access Journals (Sweden)

    Merino D

    2016-04-01

    Full Text Available David Merino, Pablo Loza-Alvarez The Institute of Photonic Sciences (ICFO, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain Abstract: Adaptive optics (AO retinal imaging has become very popular in the past few years, especially within the ophthalmic research community. Several different retinal techniques, such as fundus imaging cameras or optical coherence tomography systems, have been coupled with AO in order to produce impressive images showing individual cell mosaics over different layers of the in vivo human retina. The combination of AO with scanning laser ophthalmoscopy has been extensively used to generate impressive images of the human retina with unprecedented resolution, showing individual photoreceptor cells, retinal pigment epithelium cells, as well as microscopic capillary vessels, or the nerve fiber layer. Over the past few years, the technique has evolved to develop several different applications not only in the clinic but also in different animal models, thanks to technological developments in the field. These developments have specific applications to different fields of investigation, which are not limited to the study of retinal diseases but also to the understanding of the retinal function and vision science. This review is an attempt to summarize these developments in an understandable and brief manner in order to guide the reader into the possibilities that AO scanning laser ophthalmoscopy offers, as well as its limitations, which should be taken into account when planning on using it. Keywords: high-resolution, in vivo retinal imaging, AOSLO

  7. Adaptive optics scanning laser ophthalmoscope imaging: technology update.

    Science.gov (United States)

    Merino, David; Loza-Alvarez, Pablo

    2016-01-01

    Adaptive optics (AO) retinal imaging has become very popular in the past few years, especially within the ophthalmic research community. Several different retinal techniques, such as fundus imaging cameras or optical coherence tomography systems, have been coupled with AO in order to produce impressive images showing individual cell mosaics over different layers of the in vivo human retina. The combination of AO with scanning laser ophthalmoscopy has been extensively used to generate impressive images of the human retina with unprecedented resolution, showing individual photoreceptor cells, retinal pigment epithelium cells, as well as microscopic capillary vessels, or the nerve fiber layer. Over the past few years, the technique has evolved to develop several different applications not only in the clinic but also in different animal models, thanks to technological developments in the field. These developments have specific applications to different fields of investigation, which are not limited to the study of retinal diseases but also to the understanding of the retinal function and vision science. This review is an attempt to summarize these developments in an understandable and brief manner in order to guide the reader into the possibilities that AO scanning laser ophthalmoscopy offers, as well as its limitations, which should be taken into account when planning on using it.

  8. Adaptive optics scanning laser ophthalmoscope with integrated wide-field retinal imaging and tracking

    OpenAIRE

    Ferguson, R. Daniel; Zhong, Zhangyi; Hammer, Daniel X.; Mujat, Mircea; Patel, Ankit H.; Deng, Cong; Zou, Weiyao; Burns, Stephen A.

    2010-01-01

    We have developed a new, unified implementation of the adaptive optics scanning laser ophthalmoscope (AOSLO) incorporating a wide-field line-scanning ophthalmoscope (LSO) and a closed-loop optical retinal tracker. AOSLO raster scans are deflected by the integrated tracking mirrors so that direct AOSLO stabilization is automatic during tracking. The wide-field imager and large-spherical-mirror optical interface design, as well as a large-stroke deformable mirror (DM), enable the AOSLO image fi...

  9. Closed-loop optical stabilization and digital image registration in adaptive optics scanning light ophthalmoscopy.

    Science.gov (United States)

    Yang, Qiang; Zhang, Jie; Nozato, Koji; Saito, Kenichi; Williams, David R; Roorda, Austin; Rossi, Ethan A

    2014-09-01

    Eye motion is a major impediment to the efficient acquisition of high resolution retinal images with the adaptive optics (AO) scanning light ophthalmoscope (AOSLO). Here we demonstrate a solution to this problem by implementing both optical stabilization and digital image registration in an AOSLO. We replaced the slow scanning mirror with a two-axis tip/tilt mirror for the dual functions of slow scanning and optical stabilization. Closed-loop optical stabilization reduced the amplitude of eye-movement related-image motion by a factor of 10-15. The residual RMS error after optical stabilization alone was on the order of the size of foveal cones: ~1.66-2.56 μm or ~0.34-0.53 arcmin with typical fixational eye motion for normal observers. The full implementation, with real-time digital image registration, corrected the residual eye motion after optical stabilization with an accuracy of ~0.20-0.25 μm or ~0.04-0.05 arcmin RMS, which to our knowledge is more accurate than any method previously reported.

  10. Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

    OpenAIRE

    Zawadzki, RJ; Jones, SM; Pilli, S; Balderas-Mata, S; Kim, DY; Olivier, SS; Werner, JS

    2011-01-01

    We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was integrated into the previously described AO-UHR OCT instrument with minimal changes to the latter. This was done in order to ensure optimal performance and image quality of the AO- UHR OCT. In this d...

  11. Non-common path aberration correction in an adaptive optics scanning ophthalmoscope.

    Science.gov (United States)

    Sulai, Yusufu N; Dubra, Alfredo

    2014-09-01

    The correction of non-common path aberrations (NCPAs) between the imaging and wavefront sensing channel in a confocal scanning adaptive optics ophthalmoscope is demonstrated. NCPA correction is achieved by maximizing an image sharpness metric while the confocal detection aperture is temporarily removed, effectively minimizing the monochromatic aberrations in the illumination path of the imaging channel. Comparison of NCPA estimated using zonal and modal orthogonal wavefront corrector bases provided wavefronts that differ by ~λ/20 in root-mean-squared (~λ/30 standard deviation). Sequential insertion of a cylindrical lens in the illumination and light collection paths of the imaging channel was used to compare image resolution after changing the wavefront correction to maximize image sharpness and intensity metrics. Finally, the NCPA correction was incorporated into the closed-loop adaptive optics control by biasing the wavefront sensor signals without reducing its bandwidth.

  12. High-resolution adaptive optics scanning laser ophthalmoscope with multiple deformable mirrors

    Science.gov (United States)

    Chen, Diana C.; Olivier, Scot S.; Jones; Steven M.

    2010-02-23

    An adaptive optics scanning laser ophthalmoscopes is introduced to produce non-invasive views of the human retina. The use of dual deformable mirrors improved the dynamic range for correction of the wavefront aberrations compared with the use of the MEMS mirror alone, and improved the quality of the wavefront correction compared with the use of the bimorph mirror alone. The large-stroke bimorph deformable mirror improved the capability for axial sectioning with the confocal imaging system by providing an easier way to move the focus axially through different layers of the retina.

  13. Real-time blind deconvolution of retinal images in adaptive optics scanning laser ophthalmoscopy

    Science.gov (United States)

    Li, Hao; Lu, Jing; Shi, Guohua; Zhang, Yudong

    2011-06-01

    With the use of adaptive optics (AO), the ocular aberrations can be compensated to get high-resolution image of living human retina. However, the wavefront correction is not perfect due to the wavefront measure error and hardware restrictions. Thus, it is necessary to use a deconvolution algorithm to recover the retinal images. In this paper, a blind deconvolution technique called Incremental Wiener filter is used to restore the adaptive optics confocal scanning laser ophthalmoscope (AOSLO) images. The point-spread function (PSF) measured by wavefront sensor is only used as an initial value of our algorithm. We also realize the Incremental Wiener filter on graphics processing unit (GPU) in real-time. When the image size is 512 × 480 pixels, six iterations of our algorithm only spend about 10 ms. Retinal blood vessels as well as cells in retinal images are restored by our algorithm, and the PSFs are also revised. Retinal images with and without adaptive optics are both restored. The results show that Incremental Wiener filter reduces the noises and improve the image quality.

  14. Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging.

    Science.gov (United States)

    Zawadzki, Robert J; Jones, Steven M; Pilli, Suman; Balderas-Mata, Sandra; Kim, Dae Yu; Olivier, Scot S; Werner, John S

    2011-06-01

    We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was integrated into the previously described AO-UHR OCT instrument with minimal changes to the latter. This was done in order to ensure optimal performance and image quality of the AO- UHR OCT. In this design both imaging modalities share most of the optical components including a common AO-subsystem and vertical scanner. One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between two acquisition channels for direct comparison between retinal structures imaged by both modalities (e.g., photoreceptor mosaics or microvasculature maps). Because of differences in the detection scheme of the two systems, this dual imaging modality instrument can provide insight into retinal morphology and potentially function, that could not be accessed easily by a single system. In this paper we describe details of the components and parameters of the combined instrument, including incorporation of a novel membrane magnetic deformable mirror with increased stroke and actuator count used as a single wavefront corrector. We also discuss laser safety calculations for this multimodal system. Finally, retinal images acquired in vivo with this system are presented.

  15. Design of a Compact, Bimorph Deformable Mirror-Based Adaptive Optics Scanning Laser Ophthalmoscope.

    Science.gov (United States)

    He, Yi; Deng, Guohua; Wei, Ling; Li, Xiqi; Yang, Jinsheng; Shi, Guohua; Zhang, Yudong

    2016-01-01

    We have designed, constructed and tested an adaptive optics scanning laser ophthalmoscope (AOSLO) using a bimorph mirror. The simulated AOSLO system achieves diffraction-limited criterion through all the raster scanning fields (6.4 mm pupil, 3° × 3° on pupil). The bimorph mirror-based AOSLO corrected ocular aberrations in model eyes to less than 0.1 μm RMS wavefront error with a closed-loop bandwidth of a few Hz. Facilitated with a bimorph mirror at a stroke of ±15 μm with 35 elements and an aperture of 20 mm, the new AOSLO system has a size only half that of the first-generation AOSLO system. The significant increase in stroke allows for large ocular aberrations such as defocus in the range of ±600° and astigmatism in the range of ±200°, thereby fully exploiting the AO correcting capabilities for diseased human eyes in the future.

  16. Comparison of adaptive optics scanning light ophthalmoscopic fluorescein angiography and offset pinhole imaging.

    Science.gov (United States)

    Chui, Toco Y P; Dubow, Michael; Pinhas, Alexander; Shah, Nishit; Gan, Alexander; Weitz, Rishard; Sulai, Yusufu N; Dubra, Alfredo; Rosen, Richard B

    2014-04-01

    Recent advances to the adaptive optics scanning light ophthalmoscope (AOSLO) have enabled finer in vivo assessment of the human retinal microvasculature. AOSLO confocal reflectance imaging has been coupled with oral fluorescein angiography (FA), enabling simultaneous acquisition of structural and perfusion images. AOSLO offset pinhole (OP) imaging combined with motion contrast post-processing techniques, are able to create a similar set of structural and perfusion images without the use of exogenous contrast agent. In this study, we evaluate the similarities and differences of the structural and perfusion images obtained by either method, in healthy control subjects and in patients with retinal vasculopathy including hypertensive retinopathy, diabetic retinopathy, and retinal vein occlusion. Our results show that AOSLO OP motion contrast provides perfusion maps comparable to those obtained with AOSLO FA, while AOSLO OP reflectance images provide additional information such as vessel wall fine structure not as readily visible in AOSLO confocal reflectance images. AOSLO OP offers a non-invasive alternative to AOSLO FA without the need for any exogenous contrast agent.

  17. “Lucky Averaging”: Quality improvement on Adaptive Optics Scanning Laser Ophthalmoscope Images

    OpenAIRE

    Huang, Gang; Zhong, Zhangyi; Zou, Weiyao; Burns, Stephen A.

    2011-01-01

    Adaptive optics(AO) has greatly improved retinal image resolution. However, even with AO, temporal and spatial variations in image quality still occur due to wavefront fluctuations, intra-frame focus shifts and other factors. As a result, aligning and averaging images can produce a mean image that has lower resolution or contrast than the best images within a sequence. To address this, we propose an image post-processing scheme called “lucky averaging”, analogous to lucky imaging (Fried, 1978...

  18. Optimisation of the ion optical range adaptation method for tracking of moving tumours with scanned ion beams

    International Nuclear Information System (INIS)

    Currently an ion optical solution for beam tracking of moving targets with scanned ion beams is being investigated at GSI for the treatment of moving tumours, such as lung cancer. Beam tracking compensates target motion by adapting the lateral beam position as well as the beam range according to the motion parameters. Tracking of the lateral position is achieved via scanning magnets. For range adaptation the proposed ion optical solution uses an energy degrader with variable thickness inserted into the therapy beam line downstream of the synchrotron. By deflecting the particle beam via dipole magnets to different positions on the degrader, the range of the Bragg peak can be adjusted in real-time. Hence density changes due to organ motion can be compensated for each target spot during beam scanning. In order to reach a beam quality suitable for therapy with this method, systematic studies on the ion optical parameters have to be carried out. Different degrader designs (ramp or discrete step shaped), different materials (e.g. PMMA, graphite), as well as optimised degrader positions have been examined. The results of simulated beam profiles are presented.

  19. Optical Scanning Applications.

    Science.gov (United States)

    Wagner, Hans

    The successful use of optical scanning at the University of the Pacific (UOP) indicates that such techniques can simplify a number of administrative data processing tasks. Optical scanning is regularly used at UOP to assist with data processing in the areas of admissions, registration and grade reporting and also has applications for other tasks…

  20. High-resolution imaging of the retinal nerve fiber layer in normal eyes using adaptive optics scanning laser ophthalmoscopy.

    Directory of Open Access Journals (Sweden)

    Kohei Takayama

    Full Text Available PURPOSE: To conduct high-resolution imaging of the retinal nerve fiber layer (RNFL in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO. METHODS: AO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3-4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created. RESULTS: AO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001. RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001 CONCLUSIONS: AO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.

  1. High-Resolution Imaging by Adaptive Optics Scanning Laser Ophthalmoscopy Reveals Two Morphologically Distinct Types of Retinal Hard Exudates.

    Science.gov (United States)

    Yamaguchi, Muneo; Nakao, Shintaro; Kaizu, Yoshihiro; Kobayashi, Yoshiyuki; Nakama, Takahito; Arima, Mitsuru; Yoshida, Shigeo; Oshima, Yuji; Takeda, Atsunobu; Ikeda, Yasuhiro; Mukai, Shizuo; Ishibashi, Tatsuro; Sonoda, Koh-Hei

    2016-01-01

    Histological studies from autopsy specimens have characterized hard exudates as a composition of lipid-laden macrophages or noncellular materials including lipid and proteinaceous substances (hyaline substances). However, the characteristics of hard exudates in living patients have not been examined due to insufficient resolution of existing equipment. In this study, we used adaptive optics scanning laser ophthalmoscopy (AO-SLO) to examine the characteristics of hard exudates in patients with retinal vascular diseases. High resolution imaging using AO-SLO enables morphological classification of retinal hard exudates into two types, which could not be distinguished either on fundus examination or by spectral domain optical coherence tomography (SD-OCT). One, termed a round type, consisted of an accumulation of spherical particles (average diameter of particles: 26.9 ± 4.4 μm). The other, termed an irregular type, comprised an irregularly shaped hyper-reflective deposition. The retinal thickness in regions with round hard exudates was significantly greater than the thickness in regions with irregular hard exudates (P = 0.01 →0.02). This differentiation of retinal hard exudates in patients by AO-SLO may help in understanding the pathogenesis and clinical prognosis of retinal vascular diseases. PMID:27641223

  2. High-Resolution Imaging by Adaptive Optics Scanning Laser Ophthalmoscopy Reveals Two Morphologically Distinct Types of Retinal Hard Exudates

    Science.gov (United States)

    Yamaguchi, Muneo; Nakao, Shintaro; Kaizu, Yoshihiro; Kobayashi, Yoshiyuki; Nakama, Takahito; Arima, Mitsuru; Yoshida, Shigeo; Oshima, Yuji; Takeda, Atsunobu; Ikeda, Yasuhiro; Mukai, Shizuo; Ishibashi, Tatsuro; Sonoda, Koh-hei

    2016-01-01

    Histological studies from autopsy specimens have characterized hard exudates as a composition of lipid-laden macrophages or noncellular materials including lipid and proteinaceous substances (hyaline substances). However, the characteristics of hard exudates in living patients have not been examined due to insufficient resolution of existing equipment. In this study, we used adaptive optics scanning laser ophthalmoscopy (AO-SLO) to examine the characteristics of hard exudates in patients with retinal vascular diseases. High resolution imaging using AO-SLO enables morphological classification of retinal hard exudates into two types, which could not be distinguished either on fundus examination or by spectral domain optical coherence tomography (SD-OCT). One, termed a round type, consisted of an accumulation of spherical particles (average diameter of particles: 26.9 ± 4.4 μm). The other, termed an irregular type, comprised an irregularly shaped hyper-reflective deposition. The retinal thickness in regions with round hard exudates was significantly greater than the thickness in regions with irregular hard exudates (P = 0.01 →0.02). This differentiation of retinal hard exudates in patients by AO-SLO may help in understanding the pathogenesis and clinical prognosis of retinal vascular diseases. PMID:27641223

  3. Principles of adaptive optics

    CERN Document Server

    Tyson, Robert

    2010-01-01

    History and BackgroundIntroductionHistoryPhysical OpticsTerms in Adaptive OpticsSources of AberrationsAtmospheric TurbulenceThermal BloomingNonatmospheric SourcesAdaptive Optics CompensationPhase ConjugationLimitations of Phase ConjugationArtificial Guide StarsLasers for Guide StarsCombining the LimitationsLinear AnalysisPartial Phase ConjugationAdaptive Optics SystemsAdaptive Optics Imaging SystemsBeam Propagation Syst

  4. [Adaptive optics for ophthalmology].

    Science.gov (United States)

    Saleh, M

    2016-04-01

    Adaptive optics is a technology enhancing the visual performance of an optical system by correcting its optical aberrations. Adaptive optics have already enabled several breakthroughs in the field of visual sciences, such as improvement of visual acuity in normal and diseased eyes beyond physiologic limits, and the correction of presbyopia. Adaptive optics technology also provides high-resolution, in vivo imaging of the retina that may eventually help to detect the onset of retinal conditions at an early stage and provide better assessment of treatment efficacy.

  5. Solar tomography adaptive optics.

    Science.gov (United States)

    Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Dou, Jiangpei; Zhao, Gang

    2014-03-10

    Conventional solar adaptive optics uses one deformable mirror (DM) and one guide star for wave-front sensing, which seriously limits high-resolution imaging over a large field of view (FOV). Recent progress toward multiconjugate adaptive optics indicates that atmosphere turbulence induced wave-front distortion at different altitudes can be reconstructed by using multiple guide stars. To maximize the performance over a large FOV, we propose a solar tomography adaptive optics (TAO) system that uses tomographic wave-front information and uses one DM. We show that by fully taking advantage of the knowledge of three-dimensional wave-front distribution, a classical solar adaptive optics with one DM can provide an extra performance gain for high-resolution imaging over a large FOV in the near infrared. The TAO will allow existing one-deformable-mirror solar adaptive optics to deliver better performance over a large FOV for high-resolution magnetic field investigation, where solar activities occur in a two-dimensional field up to 60'', and where the near infrared is superior to the visible in terms of magnetic field sensitivity.

  6. Solar Adaptive Optics

    Directory of Open Access Journals (Sweden)

    Thomas R. Rimmele

    2011-06-01

    Full Text Available Adaptive optics (AO has become an indispensable tool at ground-based solar telescopes. AO enables the ground-based observer to overcome the adverse effects of atmospheric seeing and obtain diffraction limited observations. Over the last decade adaptive optics systems have been deployed at major ground-based solar telescopes and revitalized ground-based solar astronomy. The relatively small aperture of solar telescopes and the bright source make solar AO possible for visible wavelengths where the majority of solar observations are still performed. Solar AO systems enable diffraction limited observations of the Sun for a significant fraction of the available observing time at ground-based solar telescopes, which often have a larger aperture than equivalent space based observatories, such as HINODE. New ground breaking scientific results have been achieved with solar adaptive optics and this trend continues. New large aperture telescopes are currently being deployed or are under construction. With the aid of solar AO these telescopes will obtain observations of the highly structured and dynamic solar atmosphere with unprecedented resolution. This paper reviews solar adaptive optics techniques and summarizes the recent progress in the field of solar adaptive optics. An outlook to future solar AO developments, including a discussion of Multi-Conjugate AO (MCAO and Ground-Layer AO (GLAO will be given.

  7. Fluorescent scanning laser ophthalmoscopy for cellular resolution in vivo mouse retinal imaging: benefits and drawbacks of implementing adaptive optics (Conference Presentation)

    Science.gov (United States)

    Zhang, Pengfei; Goswami, Mayank; Pugh, Edward N.; Zawadzki, Robert J.

    2016-03-01

    Scanning Laser Ophthalmoscopy (SLO) is a very important imaging tool in ophthalmology research. By combing with Adaptive Optics (AO) technique, AO-SLO can correct for ocular aberrations resulting in cellular level resolution, allowing longitudinal studies of single cells morphology in the living eyes. The numerical aperture (NA) sets the optical resolution that can be achieve in the "classical" imaging systems. Mouse eye has more than twice NA of the human eye, thus offering theoretically higher resolution. However, in most SLO based imaging systems the imaging beam size at mouse pupil sets the NA of that instrument, while most of the AO-SLO systems use almost the full NA of the mouse eye. In this report, we first simulated the theoretical resolution that can be achieved in vivo for different imaging beam sizes (different NA), assumingtwo cases: no aberrations and aberrations based on published mouse ocular wavefront data. Then we imaged mouse retinas with our custom build SLO system using different beam sizes to compare these results with theory. Further experiments include comparison of the SLO and AO-SLO systems for imaging different type of fluorescently labeled cells (microglia, ganglion, photoreceptors, etc.). By comparing those results and taking into account systems complexity and ease of use, the benefits and drawbacks of two imaging systems will be discussed.

  8. Advanced Adaptive Optics Technology Development

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, S

    2001-09-18

    The NSF Center for Adaptive Optics (CfAO) is supporting research on advanced adaptive optics technologies. CfAO research activities include development and characterization of micro-electro-mechanical systems (MEMS) deformable mirror (DM) technology, as well as development and characterization of high-resolution adaptive optics systems using liquid crystal (LC) spatial light modulator (SLM) technology. This paper presents an overview of the CfAO advanced adaptive optics technology development activities including current status and future plans.

  9. Scanning Tunneling Optical Resonance Microscopy

    Science.gov (United States)

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically < 10 Hz) that the

  10. Optical Profilometers Using Adaptive Signal Processing

    Science.gov (United States)

    Hall, Gregory A.; Youngquist, Robert; Mikhael, Wasfy

    2006-01-01

    A method of adaptive signal processing has been proposed as the basis of a new generation of interferometric optical profilometers for measuring surfaces. The proposed profilometers would be portable, hand-held units. Sizes could be thus reduced because the adaptive-signal-processing method would make it possible to substitute lower-power coherent light sources (e.g., laser diodes) for white light sources and would eliminate the need for most of the optical components of current white-light profilometers. The adaptive-signal-processing method would make it possible to attain scanning ranges of the order of decimeters in the proposed profilometers.

  11. Handbook of optical and laser scanning

    CERN Document Server

    Marshall, Gerald F

    2011-01-01

    From its initial publication titled Laser Beam Scanning in 1985 to Handbook of Optical and Laser Scanning, now in its second edition, this reference has kept professionals and students at the forefront of optical scanning technology. Carefully and meticulously updated in each iteration, the book continues to be the most comprehensive scanning resource on the market. It examines the breadth and depth of subtopics in the field from a variety of perspectives. The Second Edition covers: Technologies such as piezoelectric devices Applications of laser scanning such as Ladar (laser radar) Underwater

  12. Adaptive optical zoom sensor.

    Energy Technology Data Exchange (ETDEWEB)

    Sweatt, William C.; Bagwell, Brett E.; Wick, David Victor

    2005-11-01

    In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable optical magnification with no macroscopic moving parts. Changing the effective focal length and magnification of an imaging system can be accomplished by adeptly positioning two or more active optics in the optical design and appropriately adjusting the optical power of those elements. In this application, the active optics (e.g. liquid crystal spatial light modulators or deformable mirrors) serve as variable focal-length lenses. Unfortunately, the range over which currently available devices can operate (i.e. their dynamic range) is relatively small. Therefore, the key to this concept is to create large changes in the effective focal length of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.

  13. Adaptive Optics for Large Telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, S

    2008-06-27

    The use of adaptive optics was originally conceived by astronomers seeking to correct the blurring of images made with large telescopes due to the effects of atmospheric turbulence. The basic idea is to use a device, a wave front corrector, to adjust the phase of light passing through an optical system, based on some measurement of the spatial variation of the phase transverse to the light propagation direction, using a wave front sensor. Although the original concept was intended for application to astronomical imaging, the technique can be more generally applied. For instance, adaptive optics systems have been used for several decades to correct for aberrations in high-power laser systems. At Lawrence Livermore National Laboratory (LLNL), the world's largest laser system, the National Ignition Facility, uses adaptive optics to correct for aberrations in each of the 192 beams, all of which must be precisely focused on a millimeter scale target in order to perform nuclear physics experiments.

  14. Optical-CT scanning of polymer gels

    International Nuclear Information System (INIS)

    The application of optical-CT scanning to achieve accurate high-resolution 3D dosimetry is a subject of current interest. The purpose of this paper is to provide a brief overview of past research and achievements in optical-CT polymer gel dosimetry, and to review current issues and challenges. The origins of optical-CT imaging of light-scattering polymer gels are reviewed. Techniques to characterize and optimize optical-CT performance are presented. Particular attention is given to studies of artifacts in optical-CT imaging, an important area that has not been well studied to date. The technique of optical-CT simulation by Monte-Carlo modeling is introduced as a tool to explore such artifacts. New simulation studies are presented and compared with experimental data

  15. SCANNING TUNNELING MICROSCOPY STUDIES ON OPTICAL DISC

    Institute of Scientific and Technical Information of China (English)

    徐磊; 顾冬红; 等

    1994-01-01

    Scanning tunneling microscope(STM) is used to investigate the optical dise.The areas with and without data stampers are all observedcarefully.Three-dimensional images of the disc surface clearly demonstrate the period.depth of the grooves and the shape of data stampers.Some phenomena of STM imaging are also discussed.

  16. Micromirror Arrays for Adaptive Optics

    Energy Technology Data Exchange (ETDEWEB)

    Carr, E.J.

    2000-08-07

    The long-range goal of this project is to develop the optical and mechanical design of a micromirror array for adaptive optics that will meet the following criteria: flat mirror surface ({lambda}/20), high fill factor (> 95%), large stroke (5-10 {micro}m), and pixel size {approx}-200 {micro}m. This will be accomplished by optimizing the mirror surface and actuators independently and then combining them using bonding technologies that are currently being developed.

  17. Optical transmission scanning for damage quantification in impacted GFRP composites

    Science.gov (United States)

    Khomenko, Anton; Karpenko, Oleksii; Koricho, Ermias G.; Haq, Mahmoodul; Cloud, Gary L.; Udpa, Lalita

    2016-04-01

    Glass fiber reinforced polymer (GFRP) composites constitute nearly 90% of the global composites market and are extensively used in aerospace, marine, automotive and construction industries. While their advantages of lightweight and superior mechanical properties are well explored, non-destructive evaluation (NDE) techniques that allow for damage/defect detection and assessment of its extent and severity are not fully developed. Some of the conventional NDE techniques for GFRPs include ultrasonics, X-ray, IR thermography, and a variety of optical techniques. Optical methods, specifically measuring the transmission properties (e.g. ballistic optical imaging) of specimens, provide noninvasive, safe, inexpensive, and compact solutions and are commonly used in biomedical applications. In this work, this technique is adapted for rapid NDE of GFRP composites. In its basic form, the system for optical transmission scanning (OTS) consists of a light source (laser diode), a photo detector and a 2D translation stage. The proposed technique provides high-resolution, rapid and non-contact OT (optical transmittance)-scans, and does not require any coupling. The OTS system was used for inspection of pristine and low-velocity impacted (damaged) GFRP samples. The OT-scans were compared with conventional ultrasonic C-scans and showed excellent agreement but with better resolution. Overall, the work presented lays the groundwork for cost-effective, non-contact, and rapid NDE of GFRP composite structures.

  18. Scanning Techniques For Optical Data Storage

    Science.gov (United States)

    Towner, David K.

    1987-01-01

    It seems almost paradoxical that beams of light can be moved and steered at very high speeds using a variety of scanning methods, yet the optical disk drives now being designed and marketed for data storage applications have comparatively long access times. Knowing that optical data storage has unrealized potential is of interest, but of more immediate concern is the recognition that poor access performance is a serious design issue. Magnetic disk drives offer average seek times in the 15-25ms range, compared to about 80-500ms (or more, for CD ROMS) for current optical drives. This performance disparity exists, in part, because the relatively massive "optical heads" in use today cannot be transported across the radius of a disk as quickly as a stack of much lighter magnetic heads. Any potential distance advantage that the optical drive might have, due to its substantially higher track density, is offset by the magnetic drive's use of a multi-disk stack. As a result, the drive must achieve similar radial accelerations during seeks if it is to have similar average access times. The inability of current optical drives to approach the access speeds of comparable magnetic drives significantly reduces the competitiveness of optical products in major segments of the very large data storage market. This shortcoming is especially disturbing when we know that opto-mechanical scanners typically operate in the 1-10ms range and that non-mechanical scanning techniques can be substantially faster than that.

  19. An Adaptive Algorithm to Detect Port Scans

    Institute of Scientific and Technical Information of China (English)

    单蓉胜; 李小勇; 李建华

    2004-01-01

    Detection of port scan is an important component in a network intrusion detection and prevention system. Traditional statistical methods can be easily evaded by stealthy scans and are prone to DeS attacks. This paper presents a new mechanism termed PSD(port scan detection), which is based on TCP packet anomaly evaluation. By learning the port distribution and flags of TCP packets arriving at the protected hosts, PSD can compute the anomaly score of each packet and effectively detect port scans including slow scans and stealthy scans. Experiments show that PSD has high detection accuracy and low detection latency.

  20. Optical scanning cryptography for secure wireless transmission.

    Science.gov (United States)

    Poon, Ting-Chung; Kim, Taegeun; Doh, Kyu

    2003-11-10

    We propose a method for secure wireless transmission of encrypted information. By use of an encryption key, an image or document is optically encrypted by optical heterodyne scanning and hence encryption is performed on the fly. We call this technique optical scanning cryptography. The output of the heterodyne encrypted signal is at radio frequency and can be directly sent through an antenna to a secure site for digital storage to be prepared for decryption. In the secure site, an identical optical scanning system to that used for encryption is used, together with a decryption key, to generate an electrical signal. The electrical signal is then processed and sent to a computer to be used for decryption. Utilizing the stored information received from the encryption stage and the electrical information from the secure site, a digital decryption unit performs a decryption algorithm. If the encryption key and the decryption key are matched, the decryption unit will decrypt the image or document faithfully. The overall cryptosystem can perform the incoherent optical processing counterpart of the well-known coherent double-random phase-encoding technique. We present computer simulations of the idea.

  1. Field guide to adaptive optics

    CERN Document Server

    Tyson, Robert K

    2004-01-01

    ""...These field guides will be immensely useful to all scientists and engineers who wish to brush up on authentic definitions, equations, and tables of data in optics. And the format is really user friendly! I...wonder now how I ever got along in optics without this ready reference....a real winner!"" --Dr. Leno S. Pedrotti, Center for Occupational Research and Development (CORD) Third in the Field Guide Series, this is a summary of the methods for determining the requirements of an adaptive optics system, the performance of the system, and the requirements for the components of th

  2. Future trends in adaptive Optics

    Science.gov (United States)

    Le Louarn, Miska

    2001-05-01

    In this talk, I will summarize the limitations of current adaptive optics systems (cone effect, anisoplanatism) and I will show what methods can be used to overcome them. I will focus on Multi-Conjugate AO and the polychromatic laser guide star. I will also address AO for Extremely Large Telescopes (ELTs), such as OWL (ESO) and CELT (University of California / Caltech).

  3. Adaptive Optics for Industry and Medicine

    Science.gov (United States)

    Dainty, Christopher

    2008-01-01

    wavefront corrector ophthalmic adaptive optics: design and alignment (oral paper) / Alfredo Dubra and David Williams. High speed simultaneous SLO/OCT imaging of the human retina with adaptive optics (oral paper) / M. Pircher ... [et al.]. Characterization of an AO-OCT system (oral paper) / Julia W. Evans ... [et al.]. Adaptive optics optical coherence tomography for retina imaging (oral paper) / Guohua Shi ... [et al.]. Development, calibration and performance of an electromagnetic-mirror-based adaptive optics system for visual optics (oral paper) / Enrique Gambra ... [et al.]. Adaptive eye model (poster paper) / Sergey O. Galetskzy and Alexty V. Kudryashov. Adaptive optics system for retinal imaging based on a pyramid wavefront sensor (poster paper) / Sabine Chiesa ... [et al.]. Modeling of non-stationary dynamic ocular aberrations (poster paper) / Conor Leahy and Chris Dainty. High-order aberrations and accommodation of human eye (poster paper) / Lixia Xue ... [et al.]. Electromagnetic deformable mirror: experimental assessment and first ophthalmic applications (poster paper) / L. Vabre ... [et al.]. Correcting ocular aberrations in optical coherence tomography (poster paper) / Simon Tuohy ... [et al.] -- pt. 4. Adaptive optics in optical storage and microscopy. The application of liquid crystal aberration compensator for the optical disc systems (invited paper) / Masakazu Ogasawara. Commercialization of the adaptive scanning optical microscope (ASOM) (oral paper) / Benjamin Potsaid ... [et al.]. A practical implementation of adaptive optics for aberration compensation in optical microscopy (oral paper) / A. J. Wright ... [et al.]. Active focus locking in an optically sectioning microscope using adaptive optics (poster paper) / S. Poland, A. J. Wright, J. M. Girkin. Towards four dimensional particle tracking for biological applications / Heather I. Campbell ... [et al.]. Adaptive optics for microscopy (poster paper) / Xavier Levecq -- pt. 5. Adaptive optics in lasers

  4. MEMS scanning micromirror for optical coherence tomography.

    Science.gov (United States)

    Strathman, Matthew; Liu, Yunbo; Keeler, Ethan G; Song, Mingli; Baran, Utku; Xi, Jiefeng; Sun, Ming-Ting; Wang, Ruikang; Li, Xingde; Lin, Lih Y

    2015-01-01

    This paper describes an endoscopic-inspired imaging system employing a micro-electromechanical system (MEMS) micromirror scanner to achieve beam scanning for optical coherence tomography (OCT) imaging. Miniaturization of a scanning mirror using MEMS technology can allow a fully functional imaging probe to be contained in a package sufficiently small for utilization in a working channel of a standard gastroesophageal endoscope. This work employs advanced image processing techniques to enhance the images acquired using the MEMS scanner to correct non-idealities in mirror performance. The experimental results demonstrate the effectiveness of the proposed technique.

  5. Contrast-based sensorless adaptive optics for retinal imaging

    OpenAIRE

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T. O.; He, Zheng; Metha, Andrew

    2015-01-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In thi...

  6. Adaptive mode-dependent scan for H.264/AVC intracoding

    Science.gov (United States)

    Wei, Yung-Chiang; Yang, Jar-Ferr

    2010-07-01

    In image/video coding standards, the zigzag scan provides an effective encoding order of the quantized transform coefficients such that the quantized coefficients can be arranged statistically from large to small magnitudes. Generally, the optimal scan should transfer the 2-D transform coefficients into 1-D data in descending order of their average power levels. With the optimal scan order, we can achieve more efficient variable length coding. In H.264 advanced video coding (AVC), the residuals resulting from various intramode predictions have different statistical characteristics. After analyzing the transformed residuals, we propose an adaptive scan order scheme, which optimally matches up with intraprediction mode, to further improve the efficiency of intracoding. Simulation results show that the proposed adaptive scan scheme can improve the context-adaptive variable length coding to achieve better rate-distortion performance for the H.264/AVC video coder without the increase of computation.

  7. The ERIS adaptive optics system

    Science.gov (United States)

    Marchetti, Enrico; Fedrigo, Enrico; Le Louarn, Miska; Madec, Pierre-Yves; Soenke, Christian; Brast, Roland; Conzelmann, Ralf; Delabre, Bernard; Duchateau, Michel; Frank, Christoph; Klein, Barbara; Amico, Paola; Hubin, Norbert; Esposito, Simone; Antichi, Jacopo; Carbonaro, Luca; Puglisi, Alfio; Quirós-Pacheco, Fernando; Riccardi, Armando; Xompero, Marco

    2014-07-01

    The Enhanced Resolution Imager and Spectrograph (ERIS) is the new Adaptive Optics based instrument for ESO's VLT aiming at replacing NACO and SINFONI to form a single compact facility with AO fed imaging and integral field unit spectroscopic scientific channels. ERIS completes the instrument suite at the VLT adaptive telescope. In particular it is equipped with a versatile AO system that delivers up to 95% Strehl correction in K band for science observations up to 5 micron It comprises high order NGS and LGS correction enabling the observation from exoplanets to distant galaxies with a large sky coverage thanks to the coupling of the LGS WFS with the high sensitivity of its visible WFS and the capability to observe in dust embedded environment thanks to its IR low order WFS. ERIS will be installed at the Cassegrain focus of the VLT unit hosting the Adaptive Optics Facility (AOF). The wavefront correction is provided by the AOF deformable secondary mirror while the Laser Guide Star is provided by one of the four launch units of the 4 Laser Guide Star Facility for the AOF. The overall layout of the ERIS AO system is extremely compact and highly optimized: the SPIFFI spectrograph is fed directly by the Cassegrain focus and both the NIX's (IR imager) and SPIFFI's entrance windows work as visible/infrared dichroics. In this paper we describe the concept of the ERIS AO system in detail, starting from the requirements and going through the estimated performance, the opto-mechanical design and the Real-Time Computer design.

  8. Second-harmonic scanning optical microscopy of semiconductor quantum dots

    DEFF Research Database (Denmark)

    Vohnsen, B.; Bozhevolnyi, S.I.; Pedersen, K.;

    2001-01-01

    Second-harmonic (SH) optical imaging of self-assembled InAlGaAs quantum dots (QD's) grown on a GaAs(0 0 1) substrate has been accomplished at room temperature by use of respectively a scanning far-field optical microscope in reflection mode and a scanning near-field optical microscope...

  9. Wavefront sensorless adaptive optics ophthalmoscopy in the human eye

    Science.gov (United States)

    Hofer, Heidi; Sredar, Nripun; Queener, Hope; Li, Chaohong; Porter, Jason

    2011-07-01

    Wavefront sensor noise and fidelity place a fundamental limit on achievable image quality in current adaptive optics ophthalmoscopes. Additionally, the wavefront sensor `beacon' can interfere with visual experiments. We demonstrate real-time (25 Hz), wavefront sensorless adaptive optics imaging in the living human eye with image quality rivaling that of wavefront sensor based control in the same system. A stochastic parallel gradient descent algorithm directly optimized the mean intensity in retinal image frames acquired with a confocal adaptive optics scanning laser ophthalmoscope (AOSLO). When imaging through natural, undilated pupils, both control methods resulted in comparable mean image intensities. However, when imaging through dilated pupils, image intensity was generally higher following wavefront sensor-based control. Despite the typically reduced intensity, image contrast was higher, on average, with sensorless control. Wavefront sensorless control is a viable option for imaging the living human eye and future refinements of this technique may result in even greater optical gains.

  10. Initial concepts for CELT adaptive optics

    Science.gov (United States)

    Dekany, Richard G.; Bauman, Brian J.; Gavel, Donald T.; Troy, Mitchell; Macintosh, Bruce A.; Britton, Matthew C.

    2003-02-01

    The California Extremely Large Telescope (CELT) project has recently completed a 12-month conceptual design phase that has investigated major technology challenges in a number of Observatory subsystems, including adaptive optics (AO). The goal of this effort was not to adopt one or more specific AO architectures. Rather, it was to investigate the feasibility of adaptive optics correction of a 30-meter diameter telescope and to suggest realistic cost ceilings for various adaptive optics capabilities. We present here the key design issues uncovered during conceptual design and present two non-exclusive ‘baseline" adaptive optics concepts that are expected to be further developed during the following preliminary design phase. Further analysis, detailed engineering trade studies, and certain laboratory and telescope experiments must be performed, and key component technology prototypes demonstrated, prior to adopting one or more adaptive optics systems architectures for realization.

  11. Adaptive optics imaging of the retina.

    Science.gov (United States)

    Battu, Rajani; Dabir, Supriya; Khanna, Anjani; Kumar, Anupama Kiran; Roy, Abhijit Sinha

    2014-01-01

    Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

  12. Novel optical scanning cryptography using Fresnel telescope imaging.

    Science.gov (United States)

    Yan, Aimin; Sun, Jianfeng; Hu, Zhijuan; Zhang, Jingtao; Liu, Liren

    2015-07-13

    We propose a new method called modified optical scanning cryptography using Fresnel telescope imaging technique for encryption and decryption of remote objects. An image or object can be optically encrypted on the fly by Fresnel telescope scanning system together with an encryption key. For image decryption, the encrypted signals are received and processed with an optical coherent heterodyne detection system. The proposed method has strong performance through use of secure Fresnel telescope scanning with orthogonal polarized beams and efficient all-optical information processing. The validity of the proposed method is demonstrated by numerical simulations and experimental results.

  13. Adaptive optics program at TMT

    Science.gov (United States)

    Boyer, C.; Adkins, Sean; Andersen, David R.; Atwood, Jenny; Bo, Yong; Byrnes, Peter; Caputa, Kris; Cavaco, Jeff; Ellerbroek, Brent; Gilles, Luc; Gregory, James; Herriot, Glen; Hickson, Paul; Ljusic, Zoran; Manter, Darren; Marois, Christian; Otárola, Angel; Pagès, Hubert; Schoeck, Matthias; Sinquin, Jean-Christophe; Smith, Malcolm; Spano, Paolo; Szeto, Kei; Tang, Jinlong; Travouillon, Tony; Véran, Jean-Pierre; Wang, Lianqi; Wei, Kai

    2014-07-01

    The TMT first light Adaptive Optics (AO) facility consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). NFIRAOS is a 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, and three low-order, infrared, natural guide star wavefront sensors within each client instrument. The first light LGSF system includes six sodium lasers required to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, modeling and validating the TMT first light AO systems and their components over the last two years. This will include pre-final design and prototyping activities for NFIRAOS, preliminary design and prototyping activities for the LGSF, design and prototyping for the deformable mirrors, fabrication and tests for the visible detectors, benchmarking and comparison of different algorithms and processing architecture for the Real Time Controller (RTC) and development and tests of prototype candidate lasers. Comprehensive and detailed AO modeling is continuing to support the design and development of the first light AO facility. Main modeling topics studied during the last two years include further studies in the area of wavefront error budget, sky coverage, high precision astrometry for the galactic center and other observations, high contrast imaging with NFIRAOS and its first light instruments, Point Spread Function (PSF) reconstruction for LGS MCAO, LGS photon return and sophisticated low order mode temporal filtering.

  14. Adaptive noise Wiener filter for scanning electron microscope imaging system.

    Science.gov (United States)

    Sim, K S; Teh, V; Nia, M E

    2016-03-01

    Noise on scanning electron microscope (SEM) images is studied. Gaussian noise is the most common type of noise in SEM image. We developed a new noise reduction filter based on the Wiener filter. We compared the performance of this new filter namely adaptive noise Wiener (ANW) filter, with four common existing filters as well as average filter, median filter, Gaussian smoothing filter and the Wiener filter. Based on the experiments results the proposed new filter has better performance on different noise variance comparing to the other existing noise removal filters in the experiments. SCANNING 38:148-163, 2016. © 2015 Wiley Periodicals, Inc. PMID:26235517

  15. Adaptive optical interconnects: the ADDAPT project

    Science.gov (United States)

    Henker, Ronny; Pliva, Jan; Khafaji, Mahdi; Ellinger, Frank; Toifl, Thomas; Offrein, Bert; Cevrero, Alessandro; Oezkaya, Ilter; Seifried, Marc; Ledentsov, Nikolay; Kropp, Joerg-R.; Shchukin, Vitaly; Zoldak, Martin; Halmo, Leos; Turkiewicz, Jaroslaw; Meredith, Wyn; Eddie, Iain; Georgiades, Michael; Charalambides, Savvas; Duis, Jeroen; van Leeuwen, Pieter

    2015-09-01

    Existing optical networks are driven by dynamic user and application demands but operate statically at their maximum performance. Thus, optical links do not offer much adaptability and are not very energy-efficient. In this paper a novel approach of implementing performance and power adaptivity from system down to optical device, electrical circuit and transistor level is proposed. Depending on the actual data load, the number of activated link paths and individual device parameters like bandwidth, clock rate, modulation format and gain are adapted to enable lowering the components supply power. This enables flexible energy-efficient optical transmission links which pave the way for massive reductions of CO2 emission and operating costs in data center and high performance computing applications. Within the FP7 research project Adaptive Data and Power Aware Transceivers for Optical Communications (ADDAPT) dynamic high-speed energy-efficient transceiver subsystems are developed for short-range optical interconnects taking up new adaptive technologies and methods. The research of eight partners from industry, research and education spanning seven European countries includes the investigation of several adaptive control types and algorithms, the development of a full transceiver system, the design and fabrication of optical components and integrated circuits as well as the development of high-speed, low loss packaging solutions. This paper describes and discusses the idea of ADDAPT and provides an overview about the latest research results in this field.

  16. Scanning optical microscope with long working distance objective

    Science.gov (United States)

    Cloutier, Sylvain G.

    2010-10-19

    A scanning optical microscope, including: a light source to generate a beam of probe light; collimation optics to substantially collimate the probe beam; a probe-result beamsplitter; a long working-distance, infinity-corrected objective; scanning means to scan a beam spot of the focused probe beam on or within a sample; relay optics; and a detector. The collimation optics are disposed in the probe beam. The probe-result beamsplitter is arranged in the optical paths of the probe beam and the resultant light from the sample. The beamsplitter reflects the probe beam into the objective and transmits resultant light. The long working-distance, infinity-corrected objective is also arranged in the optical paths of the probe beam and the resultant light. It focuses the reflected probe beam onto the sample, and collects and substantially collimates the resultant light. The relay optics are arranged to relay the transmitted resultant light from the beamsplitter to the detector.

  17. Five modified boundary scan adaptive test generation algorithms

    Institute of Scientific and Technical Information of China (English)

    Niu Chunping; Ren Zheping; Yao Zongzhong

    2006-01-01

    To study the diagnostic problem of Wire-OR (W-O) interconnect fault of PCB (Printed Circuit Board), five modified boundary scan adaptive algorithms for interconnect test are put forward. These algorithms apply Global-diagnosis sequence algorithm to replace the equal weight algorithm of primary test, and the test time is shortened without changing the fault diagnostic capability. The descriptions of five modified adaptive test algorithms are presented, and the capability comparison between the modified algorithm and the original algorithm is made to prove the validity of these algorithms.

  18. Teaching Optics and Systems Engineering With Adaptive Optics Workbenches

    CERN Document Server

    Harrington, David; Hunter, Lisa; Max, Claire; Hoffmann, Mark; Pitts, Mark; Armstrong, J D

    2010-01-01

    Adaptive optics workbenches are fully functional optical systems that can be used to illustrate and teach a variety of concepts and cognitive processes. Four systems have been funded, designed and constructed by various institutions and people as part of education programs associated with the Center for Adaptive Optics, the Professional Development Program and the Institute for Science and Engineer Educators. Activities can range from first-year undergraduate explorations to professional level training. These workbenches have been used in many venues including the Center for Adaptive Optics AO Summer School, the Maui Community College hosted Akamai Maui Short Course, classrooms, training of new staff in laboratories and other venues. The activity content has focused on various elements of systems thinking, characterization, feedback and system control, basic optics and optical alignment as well as advanced topics such as phase conjugation, wave-front sensing and correction concepts and system design. The work...

  19. A Miniaturized Adaptive Optic Device for Optical Telecommunications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To advance the state-of-the-art uplink laser communication technology, new adaptive optic beam compensation techniques are needed for removing various time-varying...

  20. Optical ballast and adaptive dynamic stable resonator

    Institute of Scientific and Technical Information of China (English)

    Zhang Guang-Yin; Jiao Zhi-Yong; Guo Shu-Guang; Zhang Xiao-Hua; Gu Xue-Wen; Yan Cai-Fan; Wu Ding-Er; Song Feng

    2004-01-01

    In this paper a new concept of ‘optical ballast' is put forward. Optical ballast is a kind of device that can be used to decrease the variation and fluctuation of the propagation characteristics of light beams caused by the disturbance of refractive index of the medium. To illustrate the idea clearly and concretely, a fully adaptive dynamic stable solid-state laser resonator is presented as application example of optical ballast.

  1. Overview of Advanced LIGO Adaptive Optics

    OpenAIRE

    Brooks, Aidan F.; Abbott, Benjamin; Arain, Muzammil A.; Ciani, Giacomo; Cole, Ayodele; Grabeel, Greg; Gustafson, Eric; Guido, Chris; Heintze, Matthew; Heptonstall, Alastair; Jacobson, Mindy; KIM, WON; King, Eleanor; Lynch, Alexander; O'Connor, Stephen

    2016-01-01

    This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements...

  2. Pulse front adaptive optics in multiphoton microscopy

    Science.gov (United States)

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The accurate focusing of ultrashort laser pulses is extremely important in multiphoton microscopy. Using adaptive optics to manipulate the incident ultrafast beam in either the spectral or spatial domain can introduce significant benefits when imaging. Here we introduce pulse front adaptive optics: manipulating an ultrashort pulse in both the spatial and temporal domains. A deformable mirror and a spatial light modulator are operated in concert to modify contours of constant intensity in space and time within an ultrashort pulse. Through adaptive control of the pulse front, we demonstrate an enhancement in the measured fluorescence from a two photon microscope.

  3. Adaptive Optics at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Gavel, D T

    2003-03-10

    Adaptive optics enables high resolution imaging through the atmospheric by correcting for the turbulent air's aberrations to the light waves passing through it. The Lawrence Livermore National Laboratory for a number of years has been at the forefront of applying adaptive optics technology to astronomy on the world's largest astronomical telescopes, in particular at the Keck 10-meter telescope on Mauna Kea, Hawaii. The technology includes the development of high-speed electrically driven deformable mirrors, high-speed low-noise CCD sensors, and real-time wavefront reconstruction and control hardware. Adaptive optics finds applications in many other areas where light beams pass through aberrating media and must be corrected to maintain diffraction-limited performance. We describe systems and results in astronomy, medicine (vision science), and horizontal path imaging, all active programs in our group.

  4. The Adaptive Optics Summer School Laboratory Activities

    CERN Document Server

    Ammons, S Mark; Armstrong, J D; Crossfield, Ian; Do, Tuan; Fitzgerald, Mike; Harrington, David; Hickenbotham, Adam; Hunter, Jennifer; Johnson, Jess; Johnson, Luke; Li, Kaccie; Lu, Jessica; Maness, Holly; Morzinski, Katie; Norton, Andrew; Putnam, Nicole; Roorda, Austin; Rossi, Ethan; Yelda, Sylvana

    2011-01-01

    Adaptive Optics (AO) is a new and rapidly expanding field of instrumentation, yet astronomers, vision scientists, and general AO practitioners are largely unfamiliar with the root technologies crucial to AO systems. The AO Summer School (AOSS), sponsored by the Center for Adaptive Optics, is a week-long course for training graduate students and postdoctoral researchers in the underlying theory, design, and use of AO systems. AOSS participants include astronomers who expect to utilize AO data, vision scientists who will use AO instruments to conduct research, opticians and engineers who design AO systems, and users of high-bandwidth laser communication systems. In this article we describe new AOSS laboratory sessions implemented in 2006-2009 for nearly 250 students. The activity goals include boosting familiarity with AO technologies, reinforcing knowledge of optical alignment techniques and the design of optical systems, and encouraging inquiry into critical scientific questions in vision science using AO sys...

  5. Adaptive optics applications in vision science

    Science.gov (United States)

    Olivier, Scot S.

    2003-06-01

    Adaptive optics can be used to correct the aberrations in the human eye caused by imperfections in the cornea and the lens and thereby, improve image quality both looking into and out of the eye. Under the auspices of the NSF Center for Adaptive Optics and the DOE Biomedical Engineering Program, Lawrence Livermore National Laboratory has joined together with leading vision science researchers around the country to develop and test new ophthalmic imaging systems using novel wavefront corrector technologies. Results of preliminary comparative evaluations of these technologies in initial system tests show promise for future clinical utility.

  6. Pulse front control with adaptive optics

    Science.gov (United States)

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The focusing of ultrashort laser pulses is extremely important for processes including microscopy, laser fabrication and fundamental science. Adaptive optic elements, such as liquid crystal spatial light modulators or membrane deformable mirrors, are routinely used for the correction of aberrations in these systems, leading to improved resolution and efficiency. Here, we demonstrate that adaptive elements used with ultrashort pulses should not be considered simply in terms of wavefront modification, but that changes to the incident pulse front can also occur. We experimentally show how adaptive elements may be used to engineer pulse fronts with spatial resolution.

  7. Adaptive optical design in surface plasma resonance sensor

    Institute of Scientific and Technical Information of China (English)

    ZHANG Feng; ZHONG Jin-gang

    2006-01-01

    A double-prism adaptive optical design in surface plasma resonance (SPR) sensor is proposed,which consists of two identical isosceles right-triangular prisms. One prism is used as a component of Kretschmann configuration,and the other is for regulation of the optical path. When double-prism structure is angle-scanned by an immovable incident ray,the output ray will be always parallel with the incident ray and just has a small displacement with the shift of output point.The output ray can be focused on a fixed photodetector by a convex lens.Thus it can be avoided that a prism and a photodetector rotate by θ and 2θ respectively in conventional angular scanning SPR sensor.This new design reduces the number of the movable components,makes the structure simple and compact,and makes the manipulation convenient.

  8. Contrast-based sensorless adaptive optics for retinal imaging.

    Science.gov (United States)

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T O; He, Zheng; Metha, Andrew

    2015-09-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes. PMID:26417525

  9. Implementation of 3D Optical Scanning Technology for Automotive Applications

    Directory of Open Access Journals (Sweden)

    Abdil Kuş

    2009-03-01

    Full Text Available Reverse engineering (RE is a powerful tool for generating a CAD model from the 3D scan data of a physical part that lacks documentation or has changed from the original CAD design of the part. The process of digitizing a part and creating a CAD model from 3D scan data is less time consuming and provides greater accuracy than manually measuring the part and designing the part from scratch in CAD. 3D optical scanning technology is one of the measurement methods which have evolved over the last few years and it is used in a wide range of areas from industrial applications to art and cultural heritage. It is also used extensively in the automotive industry for applications such as part inspections, scanning of tools without CAD definition, scanning the casting for definition of the stock (i.e. the amount of material to be removed from the surface of the castings model for CAM programs and reverse engineering. In this study two scanning experiments of automotive applications are illustrated. The first one examines the processes from scanning to re-manufacturing the damaged sheet metal cutting die, using a 3D scanning technique and the second study compares the scanned point clouds data to 3D CAD data for inspection purposes. Furthermore, the deviations of the part holes are determined by using different lenses and scanning parameters.

  10. Implementation of 3D Optical Scanning Technology for Automotive Applications.

    Science.gov (United States)

    Kuş, Abdil

    2009-01-01

    Reverse engineering (RE) is a powerful tool for generating a CAD model from the 3D scan data of a physical part that lacks documentation or has changed from the original CAD design of the part. The process of digitizing a part and creating a CAD model from 3D scan data is less time consuming and provides greater accuracy than manually measuring the part and designing the part from scratch in CAD. 3D optical scanning technology is one of the measurement methods which have evolved over the last few years and it is used in a wide range of areas from industrial applications to art and cultural heritage. It is also used extensively in the automotive industry for applications such as part inspections, scanning of tools without CAD definition, scanning the casting for definition of the stock (i.e. the amount of material to be removed from the surface of the castings) model for CAM programs and reverse engineering. In this study two scanning experiments of automotive applications are illustrated. The first one examines the processes from scanning to re-manufacturing the damaged sheet metal cutting die, using a 3D scanning technique and the second study compares the scanned point clouds data to 3D CAD data for inspection purposes. Furthermore, the deviations of the part holes are determined by using different lenses and scanning parameters. PMID:22573995

  11. Optical axis jitter rejection for double overlapped adaptive optics systems

    Science.gov (United States)

    Luo, Qi; Luo, Xi; Li, Xinyang

    2016-04-01

    Optical axis jitters, or vibrations, which arise from wind shaking and structural oscillations of optical platforms, etc., cause a deleterious impact on the performance of adaptive optics systems. When conventional integrators are utilized to reject such high frequency and narrow-band disturbance, the benefits are quite small despite their acceptable capabilities to reject atmospheric turbulence. In our case, two suits of complete adaptive optics systems called double overlapped adaptive optics systems (DOAOS) are used to counteract both optical jitters and atmospheric turbulence. A novel algorithm aiming to remove vibrations is proposed by resorting to combine the Smith predictor and notch filer. With the help of loop shaping method, the algorithm will lead to an effective and stable controller, which makes the characteristics of error transfer function close to notch filters. On the basis of the spectral analysis of observed data, the peak frequency and bandwidth of vibrations can be identified in advance. Afterwards, the number of notch filters and their parameters will be determined using coordination descending method. The relationship between controller parameters and filtering features is discussed, and the robustness of the controller against varying parameters of the control object is investigated. Preliminary experiments are carried out to validate the proposed algorithms. The overall control performance of DOAOS is simulated. Results show that time delays are a limit of the performance, but the algorithm can be successfully implemented on our systems, which indicate that it has a great potential to reject jitters.

  12. Adaptive Matching of the Scanning Aperture of the Environment Parameter

    Science.gov (United States)

    Choni, Yu. I.; Yunusov, N. N.

    2016-04-01

    We analyze a matching system for the scanning aperture antenna radiating through a layer with unpredictably changing parameters. Improved matching has been achieved by adaptive motion of a dielectric plate in the gap between the aperture and the radome. The system is described within the framework of an infinite layered structure. The validity of the model has been confirmed by numerical simulation using CST Microwave Studio software and by an experiment. It is shown that the reflection coefficient at the input of some types of a matching device, which is due to the deviation of the load impedance from the nominal value, is determined by a compact and versatile formula. The potential efficiency of the proposed matching system is shown by a specific example, and its dependence on the choice of the starting position of the dielectric plate is demonstrated.

  13. Adaptive holography for optical sensing applications

    Science.gov (United States)

    Residori, S.; Bortolozzo, U.; Peigné, A.; Molin, S.; Nouchi, P.; Dolfi, D.; Huignard, J. P.

    2016-03-01

    Adaptive holography is a promising method for high sensitivity phase modulation measurements in the presence of slow perturbations from the environment. The technique is based on the use of a nonlinear recombining medium, here an optically addressed spatial light modulator specifically realized to operate at 1.55 μm. Owing to the physical mechanisms involved, the interferometer adapts to slow phase variations within a range of 5-10 Hz, thus filtering out low frequency noise while transmitting higher frequency phase modulations. We present the basic principles of the adaptive interferometer and show that it can be used in association with a sensing fiber in order to detect phase modulations. Finally, a phase-OTDR architecture using the adaptive holographic interferometer is presented and shown to allows the detection of localized perturbations along the sensing fiber.

  14. A fibered interference scanning optical microscope for living cell imaging

    CERN Document Server

    Jean-Baptiste~Decombe,; Villard, Catherine; Guillou, Hervé; Chevrier, Joël; Huant, Serge; Fick, Jochen

    2010-01-01

    We report on the 3-dimensional imaging of biological cells including living neurons by a recently developed fibered interferometric Scanning Optical Microscope. The topography and surface structure of mouse fibroblasts and hippocampal neurons are clearly revealed. This straightforward technique allows fast, high resolution observation of samples in liquids without lengthy alignment procedures or costly components.

  15. Adaptive optics implementation with a Fourier reconstructor.

    Science.gov (United States)

    Glazer, Oded; Ribak, Erez N; Mirkin, Leonid

    2007-02-01

    Adaptive optics takes its servo feedback error cue from a wavefront sensor. The common Hartmann-Shack spot grid that represents the wavefront slopes is usually analyzed by finding the spot centroids. In a novel application, we used the Fourier decomposition of a spot pattern to find deviations from grid regularity. This decomposition was performed either in the Fourier domain or in the image domain, as a demodulation of the grid of spots. We analyzed the system, built a control loop for it, and tested it thoroughly. This allowed us to close the loop on wavefront errors caused by turbulence in the optical system.

  16. High-efficiency Autonomous Laser Adaptive Optics

    CERN Document Server

    Baranec, Christoph; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh; Hogstrom, Kristina; Bui, Khanh; Burse, Mahesh; Chordia, Pravin; Das, Hillol; Dekany, Richard; Kulkarni, Shrinivas; Punnadi, Sujit

    2014-01-01

    As new large-scale astronomical surveys greatly increase the number of objects targeted and discoveries made, the requirement for efficient follow-up observations is crucial. Adaptive optics imaging, which compensates for the image-blurring effects of Earth's turbulent atmosphere, is essential for these surveys, but the scarcity, complexity and high demand of current systems limits their availability for following up large numbers of targets. To address this need, we have engineered and implemented Robo-AO, a fully autonomous laser adaptive optics and imaging system that routinely images over 200 objects per night with an acuity 10 times sharper at visible wavelengths than typically possible from the ground. By greatly improving the angular resolution, sensitivity, and efficiency of 1-3 m class telescopes, we have eliminated a major obstacle in the follow-up of the discoveries from current and future large astronomical surveys.

  17. HIGH-EFFICIENCY AUTONOMOUS LASER ADAPTIVE OPTICS

    International Nuclear Information System (INIS)

    As new large-scale astronomical surveys greatly increase the number of objects targeted and discoveries made, the requirement for efficient follow-up observations is crucial. Adaptive optics imaging, which compensates for the image-blurring effects of Earth's turbulent atmosphere, is essential for these surveys, but the scarcity, complexity and high demand of current systems limit their availability for following up large numbers of targets. To address this need, we have engineered and implemented Robo-AO, a fully autonomous laser adaptive optics and imaging system that routinely images over 200 objects per night with an acuity 10 times sharper at visible wavelengths than typically possible from the ground. By greatly improving the angular resolution, sensitivity, and efficiency of 1-3 m class telescopes, we have eliminated a major obstacle in the follow-up of the discoveries from current and future large astronomical surveys

  18. Adaptive optics without altering visual perception

    OpenAIRE

    Koenig,, I.; NW, Hart; HJ, Hofer

    2014-01-01

    Adaptive optics combined with visual psychophysics creates the potential to study the relationship between visual function and the retina at the cellular scale. This potential is hampered, however, by visual interference from the wavefront-sensing beacon used during correction. For example, we have previously shown that even a dim, visible beacon can alter stimulus perception (Hofer, H. J., Blaschke, J., Patolia, J., & Koenig, D. E. (2012). Fixation light hue bias revisited: Implications for ...

  19. Thermo-optically driven adaptive mirror

    Science.gov (United States)

    Reinert, Felix; Lüthy, Willy

    2006-02-01

    The ideal adaptive optical mirror combines large aperture with high spatial and temporal resolution and a phase shift of at least 2π. Further, a simple low-cost solution is preferred. No adaptive system can perfectly fulfill all these requirements. We present a system that has the potential to reach this goal with the exception of high temporal resolution. But even with a moderate temporal resolution of one second such a system can find practical applications. For example as a laser resonator mirror that allows to modify the intensity distribution of the emission, or to correct slowly varying aberrations of optical systems. Two possible mechanisms can be used to change the optical path length of the adaptive mirror: thermal expansion of the mirror substrate or the thermally induced change of the refractive index (thermal dispersion) of a medium in front of the mirror. Both mechanisms have been shown to lead to promising results. In both cases heating was performed by irradiation of light in the active medium. The thermal dispersion based adaptive mirror is built with a thin layer of a liquid in front of a mirror. To allow a modification of the refractive index by irradiation with a diode laser at 808 nm, a suitable absorber is dissolved in the water. With chopped irradiation a resolution of 3.8 Hz at 30 % contrast is measured. This mirror has been used in a laser resonator to modify the output distribution of the laser. The thermal expansion based adaptive mirror is built with a thin layer of a silicon elastomer with a gold coated front side. We present a preparation method to produce thin films of Sylgard on sapphire. With an irradiated intensity of only 370 mW/cm2 surface modulations of up to 350 nm are obtained. With a test pattern a resolution of 1.6 line-pairs per millimeter at 30 % contrast is measured. The temporal resolution is better than one second.

  20. Near field scanning optical microscopy of polycrystalline semiconductors

    Science.gov (United States)

    Herndon, Mary Kay

    1999-09-01

    Photovoltaic devices are commonly used for space applications and remote terrestrial power requirements. Polycrystalline solar cell devices often have much lower efficiencies than their crystalline counterparts, but because they can be fabricated much more cheaply, they can still be cost-effective when compared to single crystal devices. The long term goal of this work is to provide information that will lead to higher quality devices with improved cost efficiency. In order to do this, a better understanding of the mechanisms that take place in these materials is needed. The goal of this thesis was to improve our understanding of these devices by adapting a novel characterization technique, Near Field Scanning Optical Microscopy (NSOM), to the study of polycrystalline films. Visible light NSOM is a relatively new technique that allows for optical characterization of materials with resolution beyond the far-field diffraction limit. By using NSOM to study the physical and electrical properties of polycrystalline solar cells, individual grains can be studied and more insight can be gained as to how various properties of the thin films affect the device efficiency. For this research, an NSOM was designed and built to be versatile enough to handle the sorts of samples and measurements required for studying a variety of photovoltaic devices. As a first step, the NSOM was used to characterize single crystal GaAs solar cell devices. Measurements of topography and NSOM-induced photocurrent were obtained simultaneously on cross sections of the material, allowing the p-n junction to be probed. Because the NSOM data could be compared to an expected result, this allowed verification of the new microscope's imaging capabilities and ensured accurate data interpretation. Effects of surface recombination were detected on the cleaved edges. The NSOM was used to characterize surface quality and study the effects of surface passivation treatments. Of the polycrystalline materials

  1. Overview of Advanced LIGO Adaptive Optics

    CERN Document Server

    Brooks, Aidan F; Arain, Muzammil A; Ciani, Giacomo; Cole, Ayodele; Grabeel, Greg; Gustafson, Eric; Guido, Chris; Heintze, Matthew; Heptonstall, Alastair; Jacobson, Mindy; Kim, Won; King, Eleanor; Lynch, Alexander; O'Connor, Stephen; Ottaway, David; Mailand, Ken; Mueller, Guido; Munch, Jesper; Sannibale, Virginio; Shao, Zhenhua; Smith, Michael; Veitch, Peter; Vo, Thomas; Vorvick, Cheryl; Willems, Phil

    2016-01-01

    This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements of correcting for nominal distortion in Advanced LIGO to a maximum residual error of 5.4nm, weighted across the laser beam, for up to 125W of laser input power into the interferometer.

  2. Adaptive optics optical coherence tomography for retina imaging

    Institute of Scientific and Technical Information of China (English)

    Guohua Shi; Yun Dai; Ling Wang; Zhihua Ding; Xuejun Rao; Yudong Zhang

    2008-01-01

    When optical coherence tomography (OCT) is used for human retina imaging, its transverse resolution is limited by the aberrations of human eyes. To overcome this disadvantage, a high resolution imaging system for living human retina, which consists of a time domain OCT system and a 37-elements adaptive optics (AO) system, has been developed. The AO closed loop rate is 20 frames per second, and the OCT has a 6.7-μm axial resolution. In this paper, this system is introduced and the high resolution imaging results for retina are presented.

  3. Adaptive optics for space debris tracking

    Science.gov (United States)

    Bennet, Francis; D'Orgeville, Celine; Gao, Yue; Gardhouse, William; Paulin, Nicolas; Price, Ian; Rigaut, Francois; Ritchie, Ian T.; Smith, Craig H.; Uhlendorf, Kristina; Wang, Yanjie

    2014-07-01

    Space debris in Low Earth Orbit (LEO) is becoming an increasing threat to satellite and spacecraft. A reliable and cost effective method for detecting possible collisions between orbiting objects is required to prevent an exponential growth in the number of debris. Current RADAR survey technologies used to monitor the orbits of thousands of space debris objects are relied upon to manoeuvre operational satellites to prevent possible collisions. A complimentary technique, ground-based laser LIDAR (Light Detection and Ranging) have been used to track much smaller objects with higher accuracy than RADAR, giving greater prediction of possible collisions and avoiding unnecessary manoeuvring. Adaptive optics will play a key role in any ground based LIDAR tracking system as a cost effective way of utilising smaller ground stations or less powerful lasers. The use of high power and high energy lasers for the orbital modification of debris objects will also require an adaptive optic system to achieve the high photon intensity on the target required for photon momentum transfer and laser ablation. EOS Space Systems have pioneered the development of automated laser space debris tracking for objects in low Earth orbit. The Australian National University have been developing an adaptive optics system to improve this space debris tracking capability at the EOS Space Systems Mount Stromlo facility in Canberra, Australia. The system is integrated with the telescope and commissioned as an NGS AO system before moving on to LGS AO and tracking operations. A pulsed laser propagated through the telescope is used to range the target using time of flight data. Adaptive optics is used to increase the maximum range and number or targets available to the LIDAR system, by correcting the uplink laser beam. Such a system presents some unique challenges for adaptive optics: high power lasers reflecting off deformable mirrors, high slew rate tracking, and variable off-axis tracking correction. A

  4. Electron density measurements for plasma adaptive optics

    Science.gov (United States)

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  5. A New Tracking Method for Helical Scanning Optical Tape Recorder

    Science.gov (United States)

    Narahara, Tatsuya; Kamatani, Yoshiteru; Nakao, Takashi; Kumai, Satoshi; Ozue, Tadashi

    1993-11-01

    Using a new tracking method, high track density recording on an optical tape has been achieved with a helical-scanning optical tape recorder (HS-OTR). In this recorder, the tape is wrapped around a drum, which has a high numerical-aperture objective lens of 0.50, without contact with the rotating part by means of air pressure. In the optical design, moving parts, both focus and tracking actuators, light source and reproducing optics are placed outside the rotary drum. With this system, a high carrier-to-noise-ratio of 51 dB for 1 μm mark length has been achieved. Using the tracking method, which includes a starting point servo loop, written marks have been reproduced track by track with a 2 μm pitch.

  6. Transfer functions in collection scanning near-field optical microscopy

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Vohnsen, Brian; Bozhevolnaya, Elena A.

    1999-01-01

    It is generally accepted that, if in collection near-field optical microscopy the probe-sample coupling can be disregarded, a fiber probe can be considered as a detector of the near-field intensity whose size can be accounted for via an intensity transfer function. We show that, in general...... are considered with respect to the relation between near-field optical images and the corresponding intensity distributions. Our conclusions are supported with numerical simulations and experimental results obtained by using a photon scanning tunneling microscope with an uncoated fiber tip....

  7. The CHARA Array Adaptive Optics Program

    Science.gov (United States)

    Ten Brummelaar, Theo; Che, Xiao; McAlister, Harold A.; Ireland, Michael; Monnier, John D.; Mourard, Denis; Ridgway, Stephen T.; sturmann, judit; Sturmann, Laszlo; Turner, Nils H.; Tuthill, Peter

    2016-01-01

    The CHARA array is an optical/near infrared interferometer consisting of six 1-meter diameter telescopes the longest baseline of which is 331 meters. With sub-millisecond angular resolution, the CHARA array is able to spatially resolve nearby stellar systems to reveal the detailed structures. To improve the sensitivity and scientific throughput, the CHARA array was funded by NSF-ATI in 2011, and by NSF-MRI in 2015, for an upgrade of adaptive optics (AO) systems to all six telescopes. The initial grant covers Phase I of the adaptive optics system, which includes an on-telescope Wavefront Sensor and non-common-path (NCP) error correction. The WFS use a fairly standard Shack-Hartman design and will initially close the tip tilt servo and log wavefront errors for use in data reduction and calibration. The second grant provides the funding for deformable mirrors for each telescope which will be used closed loop to remove atmospheric aberrations from the beams. There are then over twenty reflections after the WFS at the telescopes that bring the light several hundred meters into the beam combining laboratory. Some of these, including the delay line and beam reducing optics, are powered elements, and some of them, in particular the delay lines and telescope Coude optics, are continually moving. This means that the NCP problems in an interferometer are much greater than those found in more standard telescope systems. A second, slow AO system is required in the laboratory to correct for these NCP errors. We will breifly describe the AO system, and it's current status, as well as discuss the new science enabled by the system with a focus on our YSO program.

  8. Processing of Graphene combining Optical Detection and Scanning Probe Lithography

    Directory of Open Access Journals (Sweden)

    Zimmermann Sören

    2015-01-01

    Full Text Available This paper presents an experimental setup tailored for robotic processing of graphene with in-situ vision based control. A robust graphene detection approach is presented applying multiple image processing operations of the visual feedback provided by a high-resolution light microscope. Detected graphene flakes can be modified using a scanning probe based lithographical process that is directly linked to the in-situ optical images. The results of this process are discussed with respect to further application scenarios.

  9. Phase sensor for solar adaptive-optics

    CERN Document Server

    Kellerer, Aglae

    2011-01-01

    Wavefront sensing in solar adaptive-optics is currently done with correlating Shack-Hartmann sensors, although the spatial- and temporal-resolutions of the phase measurements are then limited by the extremely fast computing required to correlate the sensor signals at the frequencies of daytime atmospheric-fluctuations. To avoid this limitation, a new wavefront-sensing technique is presented, that makes use of the solar brightness and is applicable to extended sources. The wavefront is sent through a modified Mach-Zehnder interferometer. A small, central part of the wavefront is used as reference and is made to interfere with the rest of the wavefront. The contrast of two simultaneously measured interference-patterns provides a direct estimate of the wavefront phase, no additional computation being required. The proposed optical layout shows precise initial alignment to be the critical point in implementing the new wavefront-sensing scheme.

  10. Design considerations for CELT adaptive optics

    Science.gov (United States)

    Dekany, Richard G.; Nelson, Jerry E.; Bauman, Brian J.

    2000-07-01

    California Institute of Technology and University of California have begun conceptual design studies for a new telescope for astronomical research at visible and infrared wavelengths. The California Extremely Large Telescope (CELT) is currently envisioned as a filled-aperture, steerable, segmented telescope of approximately 30 m diameter. The key to satisfying many of the science goals of this observatory is the availability of diffraction-limited wavefront control. We describe potential observing modes of CELT, including a discussion of the several major outstanding AO system architectural design issues to be resolved prior to the initiation of the detailed design of the adaptive optics capability.

  11. Adaptive Holographic Fiber-Optic Interferometer

    Science.gov (United States)

    Kozhevnikov, Nikolai M.; Lipovskaya, Margarita J.

    1990-04-01

    Interaction of phase-modulated light beams in photorefractive local inertial responce media was analysed. Interaction of this type allows to registrate phase-modulated signals adaptively under low frequency phase disturbtion. The experiments on multimode fiber-optic interferometer with demodulation element based on photorefractive bacteriorhodopsin-doped polimer film are described. As the writing of dynamic phase hologram is an inertial process the signal fluctuations with the frequencies up to 100 Hz can be canceled. The hologram efficiencies are enough to registrate high frequency phase shifts ~10-4 radn.

  12. Progress of MEMS Scanning Micromirrors for Optical Bio-Imaging

    Directory of Open Access Journals (Sweden)

    Lih Y. Lin

    2015-11-01

    Full Text Available Microelectromechanical systems (MEMS have an unmatched ability to incorporate numerous functionalities into ultra-compact devices, and due to their versatility and miniaturization, MEMS have become an important cornerstone in biomedical and endoscopic imaging research. To incorporate MEMS into such applications, it is critical to understand underlying architectures involving choices in actuation mechanism, including the more common electrothermal, electrostatic, electromagnetic, and piezoelectric approaches, reviewed in this paper. Each has benefits and tradeoffs and is better suited for particular applications or imaging schemes due to achievable scan ranges, power requirements, speed, and size. Many of these characteristics are fabrication-process dependent, and this paper discusses various fabrication flows developed to integrate additional optical functionality beyond simple lateral scanning, enabling dynamic control of the focus or mirror surface. Out of this provided MEMS flexibility arises some challenges when obtaining high resolution images: due to scanning non-linearities, calibration of MEMS scanners may become critical, and inherent image artifacts or distortions during scanning can degrade image quality. Several reviewed methods and algorithms have been proposed to address these complications from MEMS scanning. Given their impact and promise, great effort and progress have been made toward integrating MEMS and biomedical imaging.

  13. In vivo cellular visualization of the human retina using optical coherence tomography and adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, S S; Jones, S M; Chen, D C; Zawadzki, R J; Choi, S S; Laut, S P; Werner, J S

    2006-01-05

    Optical coherence tomography (OCT) sees the human retina sharply with adaptive optics. In vivo cellular visualization of the human retina at micrometer-scale resolution is possible by enhancing Fourier-domain optical-coherence tomography with adaptive optics, which compensate for the eye's optical aberrations.

  14. Adaptive optics and laser guide stars at Lick observatory

    Energy Technology Data Exchange (ETDEWEB)

    Brase, J.M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    For the past several years LLNL has been developing adaptive optics systems for correction of both atmospheric turbulence effects and thermal distortions in optics for high-power lasers. Our early work focused on adaptive optics for beam control in laser isotope separation and ground-based free electron lasers. We are currently developing innovative adaptive optics and laser systems for sodium laser guide star applications at the University of California`s Lick and Keck Observeratories. This talk will describe our adaptive optics technology and some of its applications in high-resolution imaging and beam control.

  15. Optical Design for Extremely Large Telescope Adaptive Optics Systems

    Energy Technology Data Exchange (ETDEWEB)

    Bauman, B J

    2003-11-26

    Designing an adaptive optics (AO) system for extremely large telescopes (ELT's) will present new optical engineering challenges. Several of these challenges are addressed in this work, including first-order design of multi-conjugate adaptive optics (MCAO) systems, pyramid wavefront sensors (PWFS's), and laser guide star (LGS) spot elongation. MCAO systems need to be designed in consideration of various constraints, including deformable mirror size and correction height. The y,{bar y} method of first-order optical design is a graphical technique that uses a plot with marginal and chief ray heights as coordinates; the optical system is represented as a segmented line. This method is shown to be a powerful tool in designing MCAO systems. From these analyses, important conclusions about configurations are derived. PWFS's, which offer an alternative to Shack-Hartmann (SH) wavefront sensors (WFS's), are envisioned as the workhorse of layer-oriented adaptive optics. Current approaches use a 4-faceted glass pyramid to create a WFS analogous to a quad-cell SH WFS. PWFS's and SH WFS's are compared and some newly-considered similarities and PWFS advantages are presented. Techniques to extend PWFS's are offered: First, PWFS's can be extended to more pixels in the image by tiling pyramids contiguously. Second, pyramids, which are difficult to manufacture, can be replaced by less expensive lenslet arrays. An approach is outlined to convert existing SH WFS's to PWFS's for easy evaluation of PWFS's. Also, a demonstration of PWFS's in sensing varying amounts of an aberration is presented. For ELT's, the finite altitude and finite thickness of LGS's means that the LGS will appear elongated from the viewpoint of subapertures not directly under the telescope. Two techniques for dealing with LGS spot elongation in SH WFS's are presented. One method assumes that the laser will be pulsed and uses a segmented micro

  16. Design of Scattering Scanning Near-Field Optical Microscope

    Science.gov (United States)

    Schrecongost, Dustin

    The primary objective of this work is to construct a fully functional scattering type Scanning Near-field Optical Microscope (s-SNOM), and to understand the working mechanisms behind it. An s-SNOM is an instrument made up of two separate instruments working in unison. One instrument is a scanning optical microscope focusing light onto a raster scanning sample surface combined with an interferometer set up. The second instrument is an Atomic Force Microscope (AFM) operating in noncontact mode. The AFM uses a small probe that interacts with the raster scanning sample surface to map out the topography of the of the sample surface. An s-SNOM uses both of these instruments simultaneously by focusing the light of the optical microscope onto the probe of the AFM. This probe acts as a nano-antenna and confines the light allowing for light-matter interaction to be inferred far below the resolution of the diffraction limit of light. This specific s-SNOM system is unique to others by having a controllable environment. It is high vacuum compatible and variable temperature. In addition, it is efficient at collecting scattered light due to the focusing objective being a partial elliptical mirror which collects 360° of light around the major axis. This s-SNOM system will be used for direct imaging of surface plasmons. Intended works are inducing surface plasmons on InSe thin films, and seeing the enhancement effect of introducing Au nano-rods. Also dielectric properties of materials will be interpreted such as the metal to insulator phase transition of NbO2.

  17. Optical design of the adaptive optics laser guide star system

    Energy Technology Data Exchange (ETDEWEB)

    Bissinger, H. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The design of an adaptive optics package for the 3 meter Lick telescope is presented. This instrument package includes a 69 actuator deformable mirror and a Hartmann type wavefront sensor operating in the visible wavelength; a quadrant detector for the tip-tile sensor and a tip-tilt mirror to stabilize atmospheric first order tip-tile errors. A high speed computer drives the deformable mirror to achieve near diffraction limited imagery. The different optical components and their individual design constraints are described. motorized stages and diagnostics tools are used to operate and maintain alignment throughout observation time from a remote control room. The expected performance are summarized and actual results of astronomical sources are presented.

  18. Object-oriented Matlab adaptive optics toolbox

    Science.gov (United States)

    Conan, R.; Correia, C.

    2014-08-01

    Object-Oriented Matlab Adaptive Optics (OOMAO) is a Matlab toolbox dedicated to Adaptive Optics (AO) systems. OOMAO is based on a small set of classes representing the source, atmosphere, telescope, wavefront sensor, Deformable Mirror (DM) and an imager of an AO system. This simple set of classes allows simulating Natural Guide Star (NGS) and Laser Guide Star (LGS) Single Conjugate AO (SCAO) and tomography AO systems on telescopes up to the size of the Extremely Large Telescopes (ELT). The discrete phase screens that make the atmosphere model can be of infinite size, useful for modeling system performance on large time scales. OOMAO comes with its own parametric influence function model to emulate different types of DMs. The cone effect, altitude thickness and intensity profile of LGSs are also reproduced. Both modal and zonal modeling approach are implemented. OOMAO has also an extensive library of theoretical expressions to evaluate the statistical properties of turbulence wavefronts. The main design characteristics of the OOMAO toolbox are object-oriented modularity, vectorized code and transparent parallel computing. OOMAO has been used to simulate and to design the Multi-Object AO prototype Raven at the Subaru telescope and the Laser Tomography AO system of the Giant Magellan Telescope. In this paper, a Laser Tomography AO system on an ELT is simulated with OOMAO. In the first part, we set-up the class parameters and we link the instantiated objects to create the source optical path. Then we build the tomographic reconstructor and write the script for the pseudo-open-loop controller.

  19. Light scattering in optical CT scanning of Presage dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y; Adamovics, J; Cheeseborough, J C; Chao, K S; Wuu, C S, E-mail: yx2010@columbia.ed

    2010-11-01

    The intensity of the scattered light from the Presage dosimeters was measured using a Thorlabs PM100D optical power meter (Thorlabs Inc, Newton, NJ) with an optical sensor of 1 mm diameter sensitive area. Five Presage dosimeters were made as cylinders of 15.2 cm, 10 cm, 4 cm diameters and irradiated with 6 MV photons using a Varian Clinac 2100EX. Each dosimeter was put into the scanning tank of an OCTOPUS' optical CT scanner (MGS Research Inc, Madison, CT) filled with a refractive index matching liquid. A laser diode was positioned at one side of the water tank to generate a stationary laser beam of 0.8 mm width. On the other side of the tank, an in-house manufactured positioning system was used to move the optical sensor in the direction perpendicular to the outgoing laser beam from the dosimeters at an increment of 1 mm. The amount of scattered photons was found to be more than 1% of the primary light signal within 2 mm from the laser beam but decreases sharply with increasing off-axis distance. The intensity of the scattered light increases with increasing light attenuations and/or absorptions in the dosimeters. The scattered light at the same off-axis distance was weaker for dosimeters of larger diameters and for larger detector-to-dosimeter distances. Methods for minimizing the effect of the light scattering in different types of optical CT scanners are discussed.

  20. The Tesat transportable adaptive optical ground station

    Science.gov (United States)

    Saucke, Karen; Seiter, Christoph; Heine, Frank; Gregory, Mark; Tröndle, Daniel; Fischer, Edgar; Berkefeld, Thomas; Feriencik, Mikael; Feriencik, Marco; Richter, Ines; Meyer, Rolf

    2016-03-01

    Tesat together with Synopta have built a Transportable Adaptive Optical Ground Station (TAOGS) under contract of German Aerospace Center DLR for communication with the 1st and 2nd generation of Tesat's spaceborne Laser Communication Terminals (LCTs), which employ coherent homodyne optical communication with 1064 nm and binary phase shift keying (BPSK) modulation. The TAOGS is able to communicate with space segments on low earth orbit (LEO, high pointing and tracking dynamics, 5.625 Gbps), and with space segments on geostationary orbit (GEO, low pointing dynamics, up to 40,000 km distance, optical data rate of 2.8125 Gbps and user data rate of 1.8 Gbps). After an alignment and testing phase at the location of Izana, Tenerife, using the TDP1 LCT on geostationary Alphasat as counter terminal, the TAOGS is now fully functioning. Several up-links, down-links and bi-directional links have been performed. Experimental results of some of these links are presented. An outlook to further activities is given.

  1. The Coming of Age of Adaptive Optics

    Science.gov (United States)

    1995-10-01

    How Ground-Based Astronomers Beat the Atmosphere Adaptive Optics (AO) is the new ``wonder-weapon'' in ground-based astronomy. By means of advanced electro-optical devices at their telescopes, astronomers are now able to ``neutralize'' the image-smearing turbulence of the terrestrial atmosphere (seen by the unaided eye as the twinkling of stars) so that much sharper images can be obtained than before. In practice, this is done with computer-controlled, flexible mirrors which refocus the blurred images up to 100 times per second, i.e. at a rate that is faster than the changes in the atmospheric turbulence. This means that finer details in astronomical objects can be studied and also - because of the improved concentration of light in the telescope's focal plane - that fainter objects can be observed. At the moment, Adaptive Optics work best in the infrared part of spectrum, but at some later time it may also significantly improve observations at the shorter wavelengths of visible light. The many-sided aspects of this new technology and its impact on astronomical instrumentation was the subject of a recent AO conference [1] with over 150 participants from about 30 countries, presenting a total of more than 100 papers. The Introduction of AO Techniques into Astronomy The scope of this meeting was the design, fabrication and testing of AO systems, characterisation of the sources of atmospheric disturbance, modelling of compensation systems, individual components, astronomical AO results, non-astronomical applications, laser guide star systems, non-linear optical phase conjugation, performance evaluation, and other areas of this wide and complex field, in which front-line science and high technology come together in a new and powerful symbiosis. One of the specific goals of the meeting was to develop contacts between AO scientists and engineers in the western world and their colleagues in Russia and Asia. For the first time at a conference of this type, nine Russian

  2. Parsing optical scanned 3D data by Bayesian inference

    Science.gov (United States)

    Xiong, Hanwei; Xu, Jun; Xu, Chenxi; Pan, Ming

    2015-10-01

    Optical devices are always used to digitize complex objects to get their shapes in form of point clouds. The results have no semantic meaning about the objects, and tedious process is indispensable to segment the scanned data to get meanings. The reason for a person to perceive an object correctly is the usage of knowledge, so Bayesian inference is used to the goal. A probabilistic And-Or-Graph is used as a unified framework of representation, learning, and recognition for a large number of object categories, and a probabilistic model defined on this And-Or-Graph is learned from a relatively small training set per category. Given a set of 3D scanned data, the Bayesian inference constructs a most probable interpretation of the object, and a semantic segment is obtained from the part decomposition. Some examples are given to explain the method.

  3. Second-harmonic scanning optical microscopy of poled silica waveguides

    DEFF Research Database (Denmark)

    Pedersen, Kjeld; Bozhevolnyi, Sergey I.; Arentoft, Jesper;

    2000-01-01

    Second-harmonic scanning optical microscopy (SHSOM) is performed on electric-field poled silica-based waveguides. Two operation modes of SHSOM are considered. Oblique transmission reflection and normal reflection modes are used to image the spatial distribution of nonlinear susceptibilities in the...... limitations of the two operation modes when used for SHSOM studies of poled silica-based waveguides are discussed. The influence of surface defects on the resulting second-harmonic images is also considered. ©2000 American Institute of Physics....

  4. Multi-mode Scanning Near-field Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A scanning near-field optical microscope using uncoated fiber tip is described, which can work in transmission and reflection configurations, both capable of working in illumination and collection-mode, so that either transparent or opaque sample can be investigated. Depending on different applications, either constant-gap or constant-height images can be achieved. A compact homemade translator permits to select interested area of sample in the range of 4mm×4mm. Working in the constant-height as well as transmission and collection-mode configuration, several kinds of samples such as holographic grating, liposome and zeolite were investigated. The experimental results revealed the dependence of the optical resolution of the SNOM on the tip-sample separation.

  5. An adaptive optics imaging system designed for clinical use.

    Science.gov (United States)

    Zhang, Jie; Yang, Qiang; Saito, Kenichi; Nozato, Koji; Williams, David R; Rossi, Ethan A

    2015-06-01

    Here we demonstrate a new imaging system that addresses several major problems limiting the clinical utility of conventional adaptive optics scanning light ophthalmoscopy (AOSLO), including its small field of view (FOV), reliance on patient fixation for targeting imaging, and substantial post-processing time. We previously showed an efficient image based eye tracking method for real-time optical stabilization and image registration in AOSLO. However, in patients with poor fixation, eye motion causes the FOV to drift substantially, causing this approach to fail. We solve that problem here by tracking eye motion at multiple spatial scales simultaneously by optically and electronically integrating a wide FOV SLO (WFSLO) with an AOSLO. This multi-scale approach, implemented with fast tip/tilt mirrors, has a large stabilization range of ± 5.6°. Our method consists of three stages implemented in parallel: 1) coarse optical stabilization driven by a WFSLO image, 2) fine optical stabilization driven by an AOSLO image, and 3) sub-pixel digital registration of the AOSLO image. We evaluated system performance in normal eyes and diseased eyes with poor fixation. Residual image motion with incremental compensation after each stage was: 1) ~2-3 arc minutes, (arcmin) 2) ~0.5-0.8 arcmin and, 3) ~0.05-0.07 arcmin, for normal eyes. Performance in eyes with poor fixation was: 1) ~3-5 arcmin, 2) ~0.7-1.1 arcmin and 3) ~0.07-0.14 arcmin. We demonstrate that this system is capable of reducing image motion by a factor of ~400, on average. This new optical design provides additional benefits for clinical imaging, including a steering subsystem for AOSLO that can be guided by the WFSLO to target specific regions of interest such as retinal pathology and real-time averaging of registered images to eliminate image post-processing.

  6. Durham adaptive optics real-time controller.

    Science.gov (United States)

    Basden, Alastair; Geng, Deli; Myers, Richard; Younger, Eddy

    2010-11-10

    The Durham adaptive optics (AO) real-time controller was initially a proof of concept design for a generic AO control system. It has since been developed into a modern and powerful central-processing-unit-based real-time control system, capable of using hardware acceleration (including field programmable gate arrays and graphical processing units), based primarily around commercial off-the-shelf hardware. It is powerful enough to be used as the real-time controller for all currently planned 8 m class telescope AO systems. Here we give details of this controller and the concepts behind it, and report on performance, including latency and jitter, which is less than 10 μs for small AO systems.

  7. Optical Design and Optimization of Translational Reflective Adaptive Optics Ophthalmoscopes

    Science.gov (United States)

    Sulai, Yusufu N. B.

    The retina serves as the primary detector for the biological camera that is the eye. It is composed of numerous classes of neurons and support cells that work together to capture and process an image formed by the eye's optics, which is then transmitted to the brain. Loss of sight due to retinal or neuro-ophthalmic disease can prove devastating to one's quality of life, and the ability to examine the retina in vivo is invaluable in the early detection and monitoring of such diseases. Adaptive optics (AO) ophthalmoscopy is a promising diagnostic tool in early stages of development, still facing significant challenges before it can become a clinical tool. The work in this thesis is a collection of projects with the overarching goal of broadening the scope and applicability of this technology. We begin by providing an optical design approach for AO ophthalmoscopes that reduces the aberrations that degrade the performance of the AO correction. Next, we demonstrate how to further improve image resolution through the use of amplitude pupil apodization and non-common path aberration correction. This is followed by the development of a viewfinder which provides a larger field of view for retinal navigation. Finally, we conclude with the development of an innovative non-confocal light detection scheme which improves the non-invasive visualization of retinal vasculature and reveals the cone photoreceptor inner segments in healthy and diseased eyes.

  8. Adaptive optics optical coherence tomography at 1 MHz.

    Science.gov (United States)

    Kocaoglu, Omer P; Turner, Timothy L; Liu, Zhuolin; Miller, Donald T

    2014-12-01

    Image acquisition speed of optical coherence tomography (OCT) remains a fundamental barrier that limits its scientific and clinical utility. Here we demonstrate a novel multi-camera adaptive optics (AO-)OCT system for ophthalmologic use that operates at 1 million A-lines/s at a wavelength of 790 nm with 5.3 μm axial resolution in retinal tissue. Central to the spectral-domain design is a novel detection channel based on four high-speed spectrometers that receive light sequentially from a 1 × 4 optical switch assembly. Absence of moving parts enables ultra-fast (50ns) and precise switching with low insertion loss (-0.18 dB per channel). This manner of control makes use of all available light in the detection channel and avoids camera dead-time, both critical for imaging at high speeds. Additional benefit in signal-to-noise accrues from the larger numerical aperture afforded by the use of AO and yields retinal images of comparable dynamic range to that of clinical OCT. We validated system performance by a series of experiments that included imaging in both model and human eyes. We demonstrated the performance of our MHz AO-OCT system to capture detailed images of individual retinal nerve fiber bundles and cone photoreceptors. This is the fastest ophthalmic OCT system we know of in the 700 to 915 nm spectral band.

  9. Integrated optics in an electrically scanned imaging Fourier transform spectrometer

    Science.gov (United States)

    Breckinridge, James B. (Inventor); Ocallaghan, Fred G. (Inventor)

    1982-01-01

    An efficient, lightweight and stable, Fourier transform spectrometer was developed. The mechanical slide mechanism needed to create a path difference was eliminated by the use of retro-reflecting mirrors in a monolithic interferometer assembly in which the mirrors are not at 90 degrees to the propagation vector of the radiation, but rather at a small angle. The resulting plane wave fronts create a double-sided inteferogram of the source irradiance distribution which is detected by a charge-coupled device image sensor array. The position of each CCD pixel in the array is an indication of the path difference between the two retro-reflecting mirrors in the monolithic optical structure. The Fourier transform of the signals generated by the image sensor provide the spectral irradiance distribution of the source. For imaging, the interferometer assembly scans the source of irradiation by moving the entire instrument, such as would occur if it was fixedly mounted to a moving platform, i.e., a spacecraft. During scanning, the entrace slot to the monolithic optical structure sends different pixels to corresponding interferograms detected by adjacent columns of pixels of the image sensor.

  10. Images of photoreceptors in living primate eyes using adaptive optics two-photon ophthalmoscopy

    OpenAIRE

    Hunter, Jennifer J.; Masella, Benjamin; Dubra, Alfredo; Sharma, Robin; Yin, Lu; Merigan, William H.; Palczewska, Grazyna; Palczewski, Krzysztof; Williams, David R.

    2010-01-01

    In vivo two-photon imaging through the pupil of the primate eye has the potential to become a useful tool for functional imaging of the retina. Two-photon excited fluorescence images of the macaque cone mosaic were obtained using a fluorescence adaptive optics scanning laser ophthalmoscope, overcoming the challenges of a low numerical aperture, imperfect optics of the eye, high required light levels, and eye motion. Although the specific fluorophores are as yet unknown, strong in vivo intrins...

  11. Electron optics of multi-beam scanning electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadi-Gheidari, A., E-mail: A.M.Gheidari@tudelft.nl [Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Kruit, P. [Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands)

    2011-07-21

    We have developed a multi-beam scanning electron microscope (MBSEM), which delivers a square array of 196 focused beams onto a sample with a resolution and current per beam comparable to a state of the art single beam SEM. It consists of a commercially available FEI Nova-nano 200 SEM column equipped with a novel multi-electron beam source module. The key challenge in the electron optical design of the MBSEM is to minimize the off-axial aberrations of the lenses. This article addresses the electron optical design of the system and presents the result of optics simulations for a specific setting of the system. It is shown that it is possible to design a system with a theoretical axial spot size of 1.2 nm at 15 kV with a probe current of 26 pA. The off-axial aberrations for the outermost beam add up 0.8 nm, increasing the probe size to 1.5 nm.

  12. Using Site Testing Data for Adaptive Optics Simulations

    OpenAIRE

    Herriot, Glen; Andersen, David; Conan, Rod; Ellerbroek, Brent; Gilles, Luc; Hickson, Paul; Jackson, Kate; Lardière, Olivier; Pfrommer, Thomas; Véran, Jean-Pierre; Wang, Lianqi

    2011-01-01

    Astronomical Site testing data plays a vital role in the simulation, design, evaluation and operation of adaptive optics systems for large telescope. We present the example of TMT and its first light facilitiy adaptive optics system NFIRAOS, and illustrate the many simulations done based on site testing data.

  13. Optical design for uniform scanning in MEMS-based 3D imaging lidar.

    Science.gov (United States)

    Lee, Xiaobao; Wang, Chunhui

    2015-03-20

    This paper proposes a method for the optical system design of uniform scanning in a larger scan field of view (FOV) in 3D imaging lidar. The theoretical formulas are derived for the design scheme. By employing the optical design software ZEMAX, a foldaway uniform scanning optical system based on MEMS has been designed, and the scanning uniformity and spot size of the system on the target plane, perpendicular to optical axis, are analyzed and discussed. Results show that the designed system can scan uniformly within the FOV of 40°×40° with small spot size for the target at distance of about 100 m. PMID:25968504

  14. Optimized micromirror arrays for adaptive optics

    Science.gov (United States)

    Michalicek, M. Adrian; Comtois, John H.; Hetherington, Dale L.

    1999-01-01

    This paper describes the design, layout, fabrication, and surface characterization of highly optimized surface micromachined micromirror devices. Design considerations and fabrication capabilities are presented. These devices are fabricated in the state-of-the-art, four-level, planarized, ultra-low-stress polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT). This enabling process permits the development of micromirror devices with near-ideal characteristics that have previously been unrealizable in standard three-layer polysilicon processes. The reduced 1 μm minimum feature sizes and 0.1 μm mask resolution make it possible to produce dense wiring patterns and irregularly shaped flexures. Likewise, mirror surfaces can be uniquely distributed and segmented in advanced patterns and often irregular shapes in order to minimize wavefront error across the pupil. The ultra-low-stress polysilicon and planarized upper layer allow designers to make larger and more complex micromirrors of varying shape and surface area within an array while maintaining uniform performance of optical surfaces. Powerful layout functions of the AutoCAD editor simplify the design of advanced micromirror arrays and make it possible to optimize devices according to the capabilities of the fabrication process. Micromirrors fabricated in this process have demonstrated a surface variance across the array from only 2-3 nm to a worst case of roughly 25 nm while boasting active surface areas of 98% or better. Combining the process planarization with a ``planarized-by-design'' approach will produce micromirror array surfaces that are limited in flatness only by the surface deposition roughness of the structural material. Ultimately, the combination of advanced process and layout capabilities have permitted the fabrication of highly optimized micromirror arrays for adaptive optics.

  15. Beam shaping for laser-based adaptive optics in astronomy

    OpenAIRE

    Béchet, Clémentine; Guesalaga, Andrés; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

    2014-01-01

    The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics syst...

  16. Stellar photometry with Multi Conjugate Adaptive Optics

    CERN Document Server

    Fiorentino, Giuliana; McConnachie, Alan; Stetson, Peter B; Bono, Giuseppe; Turri, Paolo; Andersen, David; Veran, Jean-Pierre; Diolaiti, Emiliano; Schreiber, Laura; Ciliegi, Paolo; Bellazzini, Michele; Tolstoy, Eline; Monelli, Matteo; Iannicola, Giacinto; Ferraro, Ivan; Testa, Vincenzo

    2016-01-01

    We overview the current status of photometric analyses of images collected with Multi Conjugate Adaptive Optics (MCAO) at 8-10m class telescopes that operated, or are operating, on sky. Particular attention will be payed to resolved stellar population studies. Stars in crowded stellar systems, such as globular clusters or in nearby galaxies, are ideal test particles to test AO performance. We will focus the discussion on photometric precision and accuracy reached nowadays. We briefly describe our project on stellar photometry and astrometry of Galactic globular clusters using images taken with GeMS at the Gemini South telescope. We also present the photometry performed with DAOPHOT suite of programs into the crowded regions of these globulars reaching very faint limiting magnitudes Ks ~21.5 mag on moderately large fields of view (~1.5 arcmin squared). We highlight the need for new algorithms to improve the modeling of the complex variation of the Point Spread Function across the ?eld of view. Finally, we outl...

  17. VASAO: visible all sky adaptive optics

    Science.gov (United States)

    Veillet, Christian; Lai, Olivier; Salmon, Derrick; Pique, Jean-Paul

    2006-06-01

    Building on an extensive and successful experience in Adaptive Optics (AO) and on recent developments made in its funding nations, the Canada-France-Hawaii-Telescope Corporation (CFHT) is studying the VASAO concept: an integrated AO system that would allow diffraction limited imaging of the whole sky in the visible as well as in the infrared. At the core of VASAO, Pueo-Hou (the new Pueo) is built on Pueo, the current CFHT AO bonnette. Pueo will be refurbished and improved to be able to image the isoplanetic field at 700 nm with Strehl ratios of 30% or better, making possible imaging with a resolution of 50 milliarcseconds between 500 and 700nm, and at the telescope limit of diffraction above. The polychromatic tip-tilt laser guide star currently envisioned will be generated by a single 330nm mode-less laser, and the relative position of the 330nm and 589nm artificial stars created on the mesosphere by the 330nm excitation of the sodium layer will be monitored to provide the atmospheric tip-tilt along the line of sight, following the philosophy developed for the ELP-OA project. The feasibility study of VASAO will take most of 2006 in parallel with the development of a science case making the best possible use of the unique capabilities of the system, If the feasibility study is encouraging, VASAO development could start in 2007 for a full deployment on the sky by 2011-2012.

  18. Adaptive optics for daytime deep space laser communications to Mars

    Science.gov (United States)

    Wilson, Keith E.; Wright, Malcolm; Lee, Shinkhak; Troy, Mitchell

    2005-01-01

    This paper describes JPL research in adaptive optics (AO) to reduce the daytime background noise on a Mars-to-Earth optical communications link. AO can reduce atmosphere-induced wavefront aberrations, and enable single mode receiver operation thereby buying back margin in the deep space optical communications link.

  19. Large Binocular Telescope Adaptive Optics System: New achievements and perspectives in adaptive optics

    CERN Document Server

    Esposito, Simone; Pinna, Enrico; Puglisi, Alfio; Quirós-Pacheco, Fernando; Arcidiacono, Carmelo; Xompero, Marco; Briguglio, Runa; Agapito, Guido; Busoni, Lorenzo; Fini, Luca; Argomedo, Javier; Gherardi, Alessandro; Brusa, Guido; Miller, Douglas; Guerra, Juan Carlos; Stefanini, Paolo; Salinari, Piero; 10.1117/12.898641

    2012-01-01

    The Large Binocular Telescope (LBT) is a unique telescope featuring two co-mounted optical trains with 8.4m primary mirrors. The telescope Adaptive Optics (AO) system uses two innovative key components, namely an adaptive secondary mirror with 672 actuators and a high-order pyramid wave-front sensor. During the on-sky commissioning such a system reached performances never achieved before on large ground-based optical telescopes. Images with 40mas resolution and Strehl Ratios higher than 80% have been acquired in H band (1.6 micron). Such images showed a contrast as high as 10e-4. Based on these results, we compare the performances offered by a Natural Guide Star (NGS) system upgraded with the state-of-the-art technology and those delivered by existing Laser Guide Star (LGS) systems. The comparison, in terms of sky coverage and performances, suggests rethinking the current role ascribed to NGS and LGS in the next generation of AO systems for the 8-10 meter class telescopes and Extremely Large Telescopes (ELTs)...

  20. Application of optical scanning for measurements of castings and cores

    Directory of Open Access Journals (Sweden)

    M. Wieczorowski

    2010-01-01

    Full Text Available In the paper application of non destructive method for dimensional control of elements in initial phase of car manufacturing, at Volks-wagen Poznań foundry was presented. VW foundry in Poznań is responsible of series production of chill and dies castings made of light alloys using contemporary technologies. Castings have a complex shape: they are die castings of housings for steering columns and gravity chill castings of cylinder heads, for which cores are manufactured using both hot box and cold box method. Manufacturing capabilities of VW foundry in Poznań reach 26.000 tons of aluminum castings per year. Optical system ATOS at Volkswagen Poznań foundry is used to digitize object and determination of all dimensions and shapes of inspected object. This technology is applied in car industry, reverse engineering, quality analysis and control and to solve many similar tasks. System is based on triangulation: sensor head projects different fringes patterns onto a measured object while scanner observes their trajectories using two cameras. Basing on optical transform equations a processing unit automatically and with a great accuracy calculates 3D coordinates for every pixel of camera. Depending on camera reso-lution as an effect of such a scan we obtain a cloud of up to 4 million points for every single measurement. In the paper examples of di-mensional analysis regarding castings and cores were presented.

  1. ComPoScan: Adaptive Scanning for Efficient Concurrent Communications and Positioning with 802.11

    DEFF Research Database (Denmark)

    King, Thomas; Kjærgaard, Mikkel Baun

    2008-01-01

    Using 802.11 concurrently for communications and positioning is problematic, especially if location-based services (e.g., indoor navigation) are concurrently executed with real-time applications (e.g., VoIP, video conferencing). Periodical scanning for measuring the signal strength interrupts...... active scanning to allow positioning and to minimize the impact on the data flow. The system is configurable to realize different trade-offs between position accuracy and the level of communication interruption. We provide extensive experimental results by emulation on data collected at several sites...... and by validation in several real-world deployments. Results from the emulation show that the system can realize different trade-offs by changing parameters. Furthermore, the emulation shows that the system works independently of the environment, the network card, the signal strength measurement technology...

  2. Adaptive optics ophthalmologic systems using dual deformable mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Jones, S; Olivier, S; Chen, D; Sadda, S; Joeres, S; Zawadzki, R; Werner, J S; Miller, D

    2007-02-01

    Adaptive Optics (AO) have been increasingly combined with a variety of ophthalmic instruments over the last decade to provide cellular-level, in-vivo images of the eye. The use of MEMS deformable mirrors in these instruments has recently been demonstrated to reduce system size and cost while improving performance. However, currently available MEMS mirrors lack the required range of motion for correcting large ocular aberrations, such as defocus and astigmatism. In order to address this problem, we have developed an AO system architecture that uses two deformable mirrors, in a woofer/tweeter arrangement, with a bimorph mirror as the woofer and a MEMS mirror as the tweeter. This setup provides several advantages, including extended aberration correction range, due to the large stroke of the bimorph mirror, high order aberration correction using the MEMS mirror, and additionally, the ability to ''focus'' through the retina. This AO system architecture is currently being used in four instruments, including an Optical Coherence Tomography (OCT) system and a retinal flood-illuminated imaging system at the UC Davis Medical Center, a Scanning Laser Ophthalmoscope (SLO) at the Doheny Eye Institute, and an OCT system at Indiana University. The design, operation and evaluation of this type of AO system architecture will be presented.

  3. Novel adaptive laser scanning sensor for reverse engineering measurement

    Institute of Scientific and Technical Information of China (English)

    Zhao Ji; Ma Zi; Lin Na; Zhu Quanmin

    2007-01-01

    In this paper, a series of new techniques are used to optimize typical laser scanning sensor. The integrated prototype is compared with traditional approach to demonstrate the much improved performance. In the research and development, camera calibration is achieved by extracting characteristic points of the laser plane, so that the calibration efficiency is improved significantly. With feedback control of its intensity, the laser is automatically adjusted for different material. A modified algorithm is presented to improve the accuracy of laser stripe extraction. The fusion of data extracted from left and right camera is completed with re-sampling technique. The scanner is integrated with a robot arm and some other machinery for on-line measurement and inspection, which provides a flexible measurement tool for reverse engineering.

  4. Adaptive Zero-Coefficient Distribution Scan for Inter Block Mode Coding of H.264/AVC

    Science.gov (United States)

    Wang, Jing-Xin; Su, Alvin W. Y.

    Scanning quantized transform coefficients is an important tool for video coding. For example, the MPEG-4 video coder adopts three different scans to get better coding efficiency. This paper proposes an adaptive zero-coefficient distribution scan in inter block coding. The proposed method attempts to improve H.264/AVC zero coefficient coding by modifying the scan operation. Since the zero-coefficient distribution is changed by the proposed scan method, new VLC tables for syntax elements used in context-adaptive variable length coding (CAVLC) are also provided. The savings in bit-rate range from 2.2% to 5.1% in the high bit-rate cases, depending on different test sequences.

  5. Adaptive optics retinal imaging in the living mouse eye.

    Science.gov (United States)

    Geng, Ying; Dubra, Alfredo; Yin, Lu; Merigan, William H; Sharma, Robin; Libby, Richard T; Williams, David R

    2012-04-01

    Correction of the eye's monochromatic aberrations using adaptive optics (AO) can improve the resolution of in vivo mouse retinal images [Biss et al., Opt. Lett. 32(6), 659 (2007) and Alt et al., Proc. SPIE 7550, 755019 (2010)], but previous attempts have been limited by poor spot quality in the Shack-Hartmann wavefront sensor (SHWS). Recent advances in mouse eye wavefront sensing using an adjustable focus beacon with an annular beam profile have improved the wavefront sensor spot quality [Geng et al., Biomed. Opt. Express 2(4), 717 (2011)], and we have incorporated them into a fluorescence adaptive optics scanning laser ophthalmoscope (AOSLO). The performance of the instrument was tested on the living mouse eye, and images of multiple retinal structures, including the photoreceptor mosaic, nerve fiber bundles, fine capillaries and fluorescently labeled ganglion cells were obtained. The in vivo transverse and axial resolutions of the fluorescence channel of the AOSLO were estimated from the full width half maximum (FWHM) of the line and point spread functions (LSF and PSF), and were found to be better than 0.79 μm ± 0.03 μm (STD)(45% wider than the diffraction limit) and 10.8 μm ± 0.7 μm (STD)(two times the diffraction limit), respectively. The axial positional accuracy was estimated to be 0.36 μm. This resolution and positional accuracy has allowed us to classify many ganglion cell types, such as bistratified ganglion cells, in vivo.

  6. Adaptive optics OCT using 1060nm swept source and dual deformable lenses for human retinal imaging

    Science.gov (United States)

    Jian, Yifan; Lee, Sujin; Cua, Michelle; Miao, Dongkai; Bonora, Stefano; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    Adaptive optics concepts have been applied to the advancement of biological imaging and microscopy. In particular, AO has also been very successfully applied to cellular resolution imaging of the retina, enabling visualization of the characteristic mosaic patterns of the outer retinal layers using flood illumination fundus photography, Scanning Laser Ophthalmoscopy (SLO), and Optical Coherence Tomography (OCT). Despite the high quality of the in vivo images, there has been a limited uptake of AO imaging into the clinical environment. The high resolution afforded by AO comes at the price of limited field of view and specialized equipment. The implementation of a typical adaptive optics imaging system results in a relatively large and complex optical setup. The wavefront measurement is commonly performed using a Hartmann-Shack Wavefront Sensor (HS-WFS) placed at an image plane that is optically conjugated to the eye's pupil. The deformable mirror is also placed at a conjugate plane, relaying the wavefront corrections to the pupil. Due to the sensitivity of the HS-WFS to back-reflections, the imaging system is commonly constructed from spherical mirrors. In this project, we present a novel adaptive optics OCT retinal imaging system with significant potential to overcome many of the barriers to integration with a clinical environment. We describe in detail the implementation of a compact lens based wavefront sensorless adaptive optics (WSAO) 1060nm swept source OCT human retinal imaging system with dual deformable lenses, and present retinal images acquired in vivo from research volunteers.

  7. Architecture and performance of astronomical adaptive optics systems

    Science.gov (United States)

    Bloemhof, E.

    2002-01-01

    In recent years the technological advances of adaptive optics have enabled a great deal of innovative science. In this lecture I review the system-level design of modern astronomical AO instruments, and discuss their current capabilities.

  8. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging.

    Science.gov (United States)

    Cua, Michelle; Wahl, Daniel J; Zhao, Yuan; Lee, Sujin; Bonora, Stefano; Zawadzki, Robert J; Jian, Yifan; Sarunic, Marinko V

    2016-09-07

    Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems.

  9. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging

    Science.gov (United States)

    Cua, Michelle; Wahl, Daniel J.; Zhao, Yuan; Lee, Sujin; Bonora, Stefano; Zawadzki, Robert J.; Jian, Yifan; Sarunic, Marinko V.

    2016-01-01

    Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems. PMID:27599635

  10. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging.

    Science.gov (United States)

    Cua, Michelle; Wahl, Daniel J; Zhao, Yuan; Lee, Sujin; Bonora, Stefano; Zawadzki, Robert J; Jian, Yifan; Sarunic, Marinko V

    2016-01-01

    Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems. PMID:27599635

  11. Astronomy applications of adaptive optics at Lawrence Livermore National Laboratory

    Science.gov (United States)

    Bauman, Brian J.; Gavel, Donald T.

    2003-06-01

    Astronomical applications of adaptive optics at Lawrence Livermore National Laboratory (LLNL) has a history that extends from 1984. The program started with the Lick Observatory Adaptive Optics system and has progressed through the years to lever-larger telescopes: Keck, and now the proposed CELT (California Extremely Large Telescope) 30m telescope. LLNL AO continues to be at the forefront of AO development and science.

  12. Astronomy Applications of Adaptive Optics at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Bauman, B J; Gavel, D T

    2003-04-23

    Astronomical applications of adaptive optics at Lawrence Livermore National Laboratory (LLNL) has a history that extends from 1984. The program started with the Lick Observatory Adaptive Optics system and has progressed through the years to lever-larger telescopes: Keck, and now the proposed CELT (California Extremely Large Telescope) 30m telescope. LLNL AO continues to be at the forefront of AO development and science.

  13. Wavefront sensorless adaptive optics ophthalmoscopy in the human eye

    OpenAIRE

    Hofer, Heidi; Sredar, Nripun; Queener, Hope; Li, Chaohong; Porter, Jason

    2011-01-01

    Wavefront sensor noise and fidelity place a fundamental limit on achievable image quality in current adaptive optics ophthalmoscopes. Additionally, the wavefront sensor ‘beacon’ can interfere with visual experiments. We demonstrate real-time (25 Hz), wavefront sensorless adaptive optics imaging in the living human eye with image quality rivaling that of wavefront sensor based control in the same system. A stochastic parallel gradient descent algorithm directly optimized the mean intensity in ...

  14. Solar adaptive optics at the Observatorio del Teide, Tenerife

    Science.gov (United States)

    Soltau, Dirk; Berkefeld, Thomas; Schmidt, Dirk; von der Lühe, Oskar

    2013-10-01

    Observing the Sun with high angular resolution is difficult because the turbulence in the atmosphere is strongest during day time. In this paper we describe the principles of solar adaptive optics exemplified by the two German solar telescopes VTT and GREGOR at the Observatorio del Teide. With theses systems we obtain near diffraction limited images of the Sun. Ways to overcome the limits of conventional AO by applying multiconjugate adaptive optics (MCAO) are shown.

  15. Adaptive optics in digital micromirror based confocal microscopy

    Science.gov (United States)

    Pozzi, P.; Wilding, D.; Soloviev, O.; Vdovin, G.; Verhaegen, M.

    2016-03-01

    This proceeding reports early results in the development of a new technique for adaptive optics in confocal microscopy. The term adaptive optics refers to the branch of optics in which an active element in the optical system is used to correct inhomogeneities in the media through which light propagates. In its most classical form, mostly used in astronomical imaging, adaptive optics is achieved through a closed loop in which the actuators of a deformable mirror are driven by a wavefront sensor. This approach is severely limited in fluorescence microscopy, as the use of a wavefront sensor requires the presence of a bright, point like source in the field of view, a condition rarely satisfied in microscopy samples. Previously reported approaches to adaptive optics in fluorescence microscopy are therefore limited to the inclusion of fluorescent microspheres in the sample, to use as bright stars for wavefront sensors, or time consuming sensorless optimization procedures, requiring several seconds of optimization before the acquisition of a single image. We propose an alternative approach to the problem, implementing sensorless adaptive optics in a Programmable array microscope. A programmable array microscope is a microscope based on a digital micromirror device, in which the single elements of the micromirror act both as point sources and pinholes.

  16. Photonic crystal-adaptive optical devices

    DEFF Research Database (Denmark)

    Buss, Thomas

    -doped liquid crystal gain medium for the realization of cheap and compact optically pumped, electrically tunable lasers. Finally, a transparent projection display is presented which uses sub-wavelength gratings for redirection of light guided inside a waveguide and facilitates electro-optic switching by means...

  17. Computational adaptive optics for broadband interferometric tomography of tissues and cells

    Science.gov (United States)

    Adie, Steven G.; Mulligan, Jeffrey A.

    2016-03-01

    Adaptive optics (AO) can shape aberrated optical wavefronts to physically restore the constructive interference needed for high-resolution imaging. With access to the complex optical field, however, many functions of optical hardware can be achieved computationally, including focusing and the compensation of optical aberrations to restore the constructive interference required for diffraction-limited imaging performance. Holography, which employs interferometric detection of the complex optical field, was developed based on this connection between hardware and computational image formation, although this link has only recently been exploited for 3D tomographic imaging in scattering biological tissues. This talk will present the underlying imaging science behind computational image formation with optical coherence tomography (OCT) -- a beam-scanned version of broadband digital holography. Analogous to hardware AO (HAO), we demonstrate computational adaptive optics (CAO) and optimization of the computed pupil correction in 'sensorless mode' (Zernike polynomial corrections with feedback from image metrics) or with the use of 'guide-stars' in the sample. We discuss the concept of an 'isotomic volume' as the volumetric extension of the 'isoplanatic patch' introduced in astronomical AO. Recent CAO results and ongoing work is highlighted to point to the potential biomedical impact of computed broadband interferometric tomography. We also discuss the advantages and disadvantages of HAO vs. CAO for the effective shaping of optical wavefronts, and highlight opportunities for hybrid approaches that synergistically combine the unique advantages of hardware and computational methods for rapid volumetric tomography with cellular resolution.

  18. Topographic, electrochemical, and optical images captured using standing approach mode scanning electrochemical/optical microscopy.

    Science.gov (United States)

    Takahashi, Yasufumi; Hirano, Yu; Yasukawa, Tomoyuki; Shiku, Hitoshi; Yamada, Hiroshi; Matsue, Tomokazu

    2006-12-01

    We developed a high-resolution scanning electrochemical microscope (SECM) for the characterization of various biological materials. Electrode probes were fabricated by Ti/Pt sputtering followed by parylene C-vapor deposition polymerization on the pulled optical fiber or glass capillary. The effective electrode radius estimated from the cyclic voltammogram of ferrocyanide was found to be 35 nm. The optical aperture size was less than 170 nm, which was confirmed from the cross section of the near-field scanning optical microscope (NSOM) image of the quantum dot (QD) particles with diameters in the range of 10-15 nm. The feedback mechanism controlling the probe-sample distance was improved by vertically moving the probe by 0.1-3 microm to reduce the damage to the samples. This feedback mode, defined as "standing approach (STA) mode" (Yamada, H.; Fukumoto, H.; Yokoyama, T.; Koike, T. Anal. Chem. 2005, 77, 1785-1790), has allowed the simultaneous electrochemical and topographic imaging of the axons and cell body of a single PC12 cell under physiological conditions for the first time. STA-mode feedback imaging functions better than tip-sample regulation by the conventionally available AFM. For example, polystyrene beads (diameter approximately 6 microm) was imaged using the STA-mode SECM, whereas imaging was not possible using a conventional AFM instrument. PMID:17128996

  19. Amplitude variations on the Extreme Adaptive Optics testbed

    Energy Technology Data Exchange (ETDEWEB)

    Evans, J; Thomas, S; Dillon, D; Gavel, D; Phillion, D; Macintosh, B

    2007-08-14

    High-contrast adaptive optics systems, such as those needed to image extrasolar planets, are known to require excellent wavefront control and diffraction suppression. At the Laboratory for Adaptive Optics on the Extreme Adaptive Optics testbed, we have already demonstrated wavefront control of better than 1 nm rms within controllable spatial frequencies. Corresponding contrast measurements, however, are limited by amplitude variations, including those introduced by the micro-electrical-mechanical-systems (MEMS) deformable mirror. Results from experimental measurements and wave optic simulations of amplitude variations on the ExAO testbed are presented. We find systematic intensity variations of about 2% rms, and intensity variations with the MEMS to be 6%. Some errors are introduced by phase and amplitude mixing because the MEMS is not conjugate to the pupil, but independent measurements of MEMS reflectivity suggest that some error is introduced by small non-uniformities in the reflectivity.

  20. Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy.

    Science.gov (United States)

    Yi, Ji; Chen, Siyu; Shu, Xiao; Fawzi, Amani A; Zhang, Hao F

    2015-10-01

    We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina. PMID:26504622

  1. Optical Field Measurement of Nano-Apertures with a Scanning Near-Field Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    XU Tie-Jun; XU Ji-Ying; WANG Jia; TIAN Qian

    2004-01-01

    @@ We investigate optical near-field distributions of the unconventional C-apertures and the conventional square apertures in preliminary experiment with an aperture scanning near-field optical microscope. These nano-apertures are fabricated in Au film on a glass substrate with focused ion beam technology. The experimental results indicate the uptrend of output light intensity that a C-aperture enables the intensity maximum to increase at least 10times more than a square aperture with same unit length. The measured near-field light spot sizes of C-apertureand square aperture with 200-nm unit length are 439nm × 500nm and 245nm × 216nm, respectively.

  2. GPU-based computational adaptive optics for volumetric optical coherence microscopy

    Science.gov (United States)

    Tang, Han; Mulligan, Jeffrey A.; Untracht, Gavrielle R.; Zhang, Xihao; Adie, Steven G.

    2016-03-01

    Optical coherence tomography (OCT) is a non-invasive imaging technique that measures reflectance from within biological tissues. Current higher-NA optical coherence microscopy (OCM) technologies with near cellular resolution have limitations on volumetric imaging capabilities due to the trade-offs between resolution vs. depth-of-field and sensitivity to aberrations. Such trade-offs can be addressed using computational adaptive optics (CAO), which corrects aberration computationally for all depths based on the complex optical field measured by OCT. However, due to the large size of datasets plus the computational complexity of CAO and OCT algorithms, it is a challenge to achieve high-resolution 3D-OCM reconstructions at speeds suitable for clinical and research OCM imaging. In recent years, real-time OCT reconstruction incorporating both dispersion and defocus correction has been achieved through parallel computing on graphics processing units (GPUs). We add to these methods by implementing depth-dependent aberration correction for volumetric OCM using plane-by-plane phase deconvolution. Following both defocus and aberration correction, our reconstruction algorithm achieved depth-independent transverse resolution of 2.8 um, equal to the diffraction-limited focal plane resolution. We have translated the CAO algorithm to a CUDA code implementation and tested the speed of the software in real-time using two GPUs - NVIDIA Quadro K600 and Geforce TITAN Z. For a data volume containing 4096×256×256 voxels, our system's processing speed can keep up with the 60 kHz acquisition rate of the line-scan camera, and takes 1.09 seconds to simultaneously update the CAO correction for 3 en face planes at user-selectable depths.

  3. CCD-based optical CT scanning of highly attenuating phantoms

    Energy Technology Data Exchange (ETDEWEB)

    Al-Nowais, Shamsa [Department of Physics, University of Surrey, Guildford (United Kingdom); Doran, Simon J [CRUK Clinical MR Research Group, Institute of Cancer Research, Sutton (United Kingdom)], E-mail: Simon.Doran@icr.ac.uk

    2009-05-01

    The introduction of optical computed tomography (optical-CT) offers economic and easy to use 3-D optical readout for gel dosimeters. However, previous authors have noted some challenges regarding the accuracy of such imaging techniques at high values of optical density. In this paper, we take a closer look at the 'cupping' artefact evident in both light-scattering polymer systems and highly light absorbing phantoms using our CCD-based optical scanner. In addition, a technique is implemented whereby the maximum measurable optical absorbance is extended to correct for any errors that may have occurred in the estimated value of the dark current or ambient light reaching the detector. The results indicate that for absorbance values up to 2.0, the optical scanner results have good accuracy, whereas this is not the case at high absorbance values for reasons yet to be explained.

  4. PASSATA - Object oriented numerical simulation software for adaptive optics

    CERN Document Server

    Agapito, G; Esposito, S

    2016-01-01

    We present the last version of the PyrAmid Simulator Software for Adaptive opTics Arcetri (PASSATA), an IDL and CUDA based object oriented software developed in the Adaptive Optics group of the Arcetri observatory for Monte-Carlo end-to-end adaptive optics simulations. The original aim of this software was to evaluate the performance of a single conjugate adaptive optics system for ground based telescope with a pyramid wavefront sensor. After some years of development, the current version of PASSATA is able to simulate several adaptive optics systems: single conjugate, multi conjugate and ground layer, with Shack Hartmann and Pyramid wavefront sensors. It can simulate from 8m to 40m class telescopes, with diffraction limited and resolved sources at finite or infinite distance from the pupil. The main advantages of this software are the versatility given by the object oriented approach and the speed given by the CUDA implementation of the most computational demanding routines. We describe the software with its...

  5. The New Weather Radar for America's Space Program in Florida: A Temperature Profile Adaptive Scan Strategy

    Science.gov (United States)

    Carey, L. D.; Petersen, W. A.; Deierling, W.; Roeder, W. P.

    2009-01-01

    A new weather radar is being acquired for use in support of America s space program at Cape Canaveral Air Force Station, NASA Kennedy Space Center, and Patrick AFB on the east coast of central Florida. This new radar replaces the modified WSR-74C at Patrick AFB that has been in use since 1984. The new radar is a Radtec TDR 43-250, which has Doppler and dual polarization capability. A new fixed scan strategy was designed to best support the space program. The fixed scan strategy represents a complex compromise between many competing factors and relies on climatological heights of various temperatures that are important for improved lightning forecasting and evaluation of Lightning Launch Commit Criteria (LCC), which are the weather rules to avoid lightning strikes to in-flight rockets. The 0 C to -20 C layer is vital since most generation of electric charge occurs within it and so it is critical in evaluating Lightning LCC and in forecasting lightning. These are two of the most important duties of 45 WS. While the fixed scan strategy that covers most of the climatological variation of the 0 C to -20 C levels with high resolution ensures that these critical temperatures are well covered most of the time, it also means that on any particular day the radar is spending precious time scanning at angles covering less important heights. The goal of this project is to develop a user-friendly, Interactive Data Language (IDL) computer program that will automatically generate optimized radar scan strategies that adapt to user input of the temperature profile and other important parameters. By using only the required scan angles output by the temperature profile adaptive scan strategy program, faster update times for volume scans and/or collection of more samples per gate for better data quality is possible, while maintaining high resolution at the critical temperature levels. The temperature profile adaptive technique will also take into account earth curvature and refraction

  6. Wavelet methods in multi-conjugate adaptive optics

    CERN Document Server

    Helin, Tapio

    2013-01-01

    The next generation ground-based telescopes rely heavily on adaptive optics for overcoming the limitation of atmospheric turbulence. In the future adaptive optics modalities, like multi-conjugate adaptive optics (MCAO), atmospheric tomography is the major mathematical and computational challenge. In this severely ill-posed problem a fast and stable reconstruction algorithm is needed that can take into account many real-life phenomena of telescope imaging. We introduce a novel reconstruction method for the atmospheric tomography problem and demonstrate its performance and flexibility in the context of MCAO. Our method is based on using locality properties of compactly supported wavelets, both in the spatial and frequency domain. The reconstruction in the atmospheric tomography problem is obtained by solving the Bayesian MAP estimator with a conjugate gradient based algorithm. An accelerated algorithm with preconditioning is also introduced. Numerical performance is demonstrated on the official end-to-end simul...

  7. Wavelet methods in multi-conjugate adaptive optics

    Science.gov (United States)

    Helin, T.; Yudytskiy, M.

    2013-08-01

    The next generation ground-based telescopes rely heavily on adaptive optics for overcoming the limitation of atmospheric turbulence. In the future adaptive optics modalities, like multi-conjugate adaptive optics (MCAO), atmospheric tomography is the major mathematical and computational challenge. In this severely ill-posed problem, a fast and stable reconstruction algorithm is needed that can take into account many real-life phenomena of telescope imaging. We introduce a novel reconstruction method for the atmospheric tomography problem and demonstrate its performance and flexibility in the context of MCAO. Our method is based on using locality properties of compactly supported wavelets, both in the spatial and frequency domains. The reconstruction in the atmospheric tomography problem is obtained by solving the Bayesian MAP estimator with a conjugate-gradient-based algorithm. An accelerated algorithm with preconditioning is also introduced. Numerical performance is demonstrated on the official end-to-end simulation tool OCTOPUS of European Southern Observatory.

  8. Beaconless adaptive-optics technique for HEL beam control

    Science.gov (United States)

    Khizhnyak, Anatoliy; Markov, Vladimir

    2016-05-01

    Effective performance of forthcoming laser systems capable of power delivery on a distant target requires an adaptive optics system to correct atmospheric perturbations on the laser beam. The turbulence-induced effects are responsible for beam wobbling, wandering, and intensity scintillation, resulting in degradation of the beam quality and power density on the target. Adaptive optics methods are used to compensate for these negative effects. In its turn, operation of the AOS system requires a reference wave that can be generated by the beacon on the target. This report discusses a beaconless approach for wavefront correction with its performance based on the detection of the target-scattered light. Postprocessing of the beacon-generated light field enables retrieval and detailed characterization of the turbulence-perturbed wavefront -data that is essential to control the adaptive optics module of a high-power laser system.

  9. Surface Plasmon Wave Adapter Designed with Transformation Optics

    DEFF Research Database (Denmark)

    Zhang, Jingjing; Xiao, Sanshui; Wubs, Martijn;

    2011-01-01

    On the basis of transformation optics, we propose the design of a surface plasmon wave adapter which confines surface plasmon waves on non-uniform metal surfaces and enables adiabatic mode transformation of surface plasmon polaritons with very short tapers. This adapter can be simply achieved...... with homogeneous anisotropic naturally occurring materials or subwavelength grating-structured dielectric materials. Full wave simulations based on a finite-element method have been performed to validate our proposal....

  10. Hybrid Deconvolution of Adaptive Optics Retinal Images from Wavefront Sensing

    Institute of Scientific and Technical Information of China (English)

    TIAN Yu; RAO Chang-Hui; RAO Xue-Jun; WANG Cheng; YU Xiang; LIU Qian; XUE Li-Xia; LING Ning; JIANG Wen-Han

    2008-01-01

    Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time.However the correction is partial due to the limitation of hardware.We propose a kind of hybrid image post-processing method.which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image.This method is applied in the image restoration of the vivid human retinal images.The results show that it is effective to improve the retinal image quality.

  11. A real-time simulation facility for astronomical adaptive optics

    CERN Document Server

    Basden, Alastair

    2014-01-01

    In this paper we introduce the concept of real-time hardware-in-the-loop simulation for astronomical adaptive optics, and present the case for the requirement for such a facility. This real-time simulation, when linked with an adaptive optics real-time control system, provides an essential tool for the validation, verification and integration of the Extremely Large Telescope real-time control systems prior to commissioning at the telescope. We demonstrate that such a facility is crucial for the success of the future extremely large telescopes.

  12. Hybrid Deconvolution of Adaptive Optics Retinal Images from Wavefront Sensing

    International Nuclear Information System (INIS)

    Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time. However the correction is partial due to the limitation of hardware. We propose a kind of hybrid image post-processing method, which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image. This method is applied in the image restoration of the vivid human retinal images. The results show that it is effective to improve the retinal image quality

  13. 3D manipulation with a scanning near field optical nanotweezers

    CERN Document Server

    Berthelot, J; Juan, M L; Kreuzer, M P; Renger, J; Quidant, R

    2013-01-01

    Recent advances in Nanotechnologies have prompted the need for tools to accurately and non-invasively manipulate individual nano-objects. Among possible strategies, optical forces have been foreseen to provide researchers with nano-optical tweezers capable to trap a specimen and move it in 3D. In practice though, the combination of weak optical forces involved and photothermal issues have thus far prevented their experimental realization. Here, we demonstrate first 3D optical manipulation of single 50 nm dielectric objects with near field nano-tweezers. The nano-optical trap is built by engineering a bowtie plasmonic aperture at the extremity of a tapered metal-coated optical fiber. Both the trapping operation and monitoring are performed through the optical fiber making these nano-tweezers totally autonomous and free of bulky optical elements. The achieved trapping performances allow for the trapped specimen to be moved over tens of micrometers during several minutes with very low in-trap intensities. This n...

  14. Optical characterication of probes for photon scanning tunnelling microscopy

    DEFF Research Database (Denmark)

    Vohnsen, Brian; Bozhevolnyi, Sergey I.

    1999-01-01

    in a direct manner and has most often been inferred from the apparent quality of recorded optical images. Complicated near-field optical imaging characteristics, together with the possibility of topographically induced artefacts, however, has increased demands for a more reliable probe characterization...

  15. Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

    Energy Technology Data Exchange (ETDEWEB)

    Awwal, A; Bauman, B; Gavel, D; Olivier, S; Jones, S; Hardy, J L; Barnes, T; Werner, J S

    2003-02-05

    Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.

  16. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

    Science.gov (United States)

    Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Seungjae; Lee, Byoungho; Kim, Myung K.

    2015-11-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: self­interference incoherent digital holography (SIDH). The SIDH generates a complex-i.e., amplitude plus phase-hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  17. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics.

    Science.gov (United States)

    Jang, Changwon; Kim, Jonghyun; Clark, David C; Lee, Seungjae; Lee, Byoungho; Kim, Myung K

    2015-01-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex—i.e., amplitude plus phase—hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  18. Accuracy requirements of optical linear algebra processors in adaptive optics imaging systems.

    Science.gov (United States)

    Downie, J D; Goodman, J W

    1989-10-15

    A ground-based adaptive optics imaging telescope system attempts to improve image quality by measuring and correcting for atmospherically induced wavefront aberrations. The necessary control computations during each cycle will take a finite amount of time, which adds to the residual error variance since the atmosphere continues to change during that time. Thus an optical processor may be well-suited for this task. This paper investigates this possibility by studying the accuracy requirements in a general optical processor that will make it competitive with, or superior to, a conventional digital computer for adaptive optics use.

  19. Limitations to adaptive optics image quality in rodent eyes

    OpenAIRE

    Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

    2012-01-01

    Adaptive optics (AO) retinal image quality of rodent eyes is inferior to that of human eyes, despite the promise of greater numerical aperture. This paradox challenges several assumptions commonly made in AO imaging, assumptions which may be invalidated by the very high power and dioptric thickness of the rodent retina. We used optical modeling to compare the performance of rat and human eyes under conditions that tested the validity of these assumptions. Results showed that AO image quality ...

  20. Modeling the Effect of Wave-front Aberrations in Fiber-based Scanning Optical Microscopy

    NARCIS (Netherlands)

    Verstraete, H.R.G.W.; Verhaegen, M.H.G.; Kalkman, J.

    2013-01-01

    In scanning microscopy and optical coherence tomography, aberrations of the wave-front cause a loss in intensity and resolution. Intensity and resolution are quantified using Fresnel propagation, Fraunhofer diffraction, and the calculation of overlap integrals.

  1. Optical System Design For High Speed Bar Code Scanning

    Science.gov (United States)

    Hellekson, Ronald; Reddersen, Brad; Campbell, Scott

    1987-04-01

    Spectra-Physics recently introduced the Model 750 SL scanner for use in the European point-of-sale market, to meet the European requirement for a scanner of less than 13 cm height. The model 750 SL uses a higher density computer designed scan pattern with a retrodirective collection system to scan and detect UPC, EAN, and JAN bar codes. The scanner "reads" these bar codes in such a way that the user need not precisely align the bar code symbol with respect to the window in the scanner even at package speeds up to 100 inches per second. By using a unique geometrical arrangement of mirrors, a polygonal mirror assembly, and a custom-designed plastic bifocal lens, a design was developed to meet these requirements. This paper describes the design of this new low cost scanner, the use of computer-aided design in the development of this scanner, and some observations on the future of bar code scanning.

  2. A Guided Mode View on Near-Field Scanning Optical Microscopy Measurements of Optical Magnetic Fields with Slit Probes

    OpenAIRE

    Stoffer, Remco; Hammer, Manfred; Ivanova, O. V.; Hoekstra, Hugo J.W.M.

    2010-01-01

    Recent Near-field Scanning Optical Microscopy (NSOM) experiments with slit metal coated probes claim to measure the out-of-plane optical magnetic field around a dielectric sample waveguide [1]. The observations can also be explained by mode overlap calculations.

  3. Smart microscope: an adaptive optics learning system for aberration correction in multiphoton confocal microscopy.

    Science.gov (United States)

    Albert, O; Sherman, L; Mourou, G; Norris, T B; Vdovin, G

    2000-01-01

    Off-axis aberrations in a beam-scanning multiphoton confocal microscope are corrected with a deformable mirror. The optimal mirror shape for each pixel is determined by a genetic learning algorithm, in which the second-harmonic or two-photon fluorescence signal from a reference sample is maximized. The speed of the convergence is improved by use of a Zernike polynomial basis for the deformable mirror shape. This adaptive optical correction scheme is implemented in an all-reflective system by use of extremely short (10-fs) optical pulses, and it is shown that the scanning area of an f:1 off-axis parabola can be increased by nine times with this technique. PMID:18059779

  4. Nonlinear optical switching and optical limiting in colloidal CdSe quantum dots investigated by nanosecond Z-scan measurement

    Science.gov (United States)

    Valligatla, Sreeramulu; Haldar, Krishna Kanta; Patra, Amitava; Desai, Narayana Rao

    2016-10-01

    The semiconductor nanocrystals are found to be promising class of third order nonlinear optical materials because of quantum confinement effects. Here, we highlight the nonlinear optical switching and optical limiting of cadmium selenide (CdSe) quantum dots (QDs) using nanosecond Z-scan measurement. The intensity dependent nonlinear absorption and nonlinear refraction of CdSe QDs were investigated by applying the Z-scan technique with 532 nm, nanosecond laser pulses. At lower intensities, the nonlinear process is dominated by saturable absorption (SA) and it is changed to reverse saturable absorption (RSA) at higher intensities. The SA behaviour is attributed to the ground state bleaching and the RSA is ascribed to free carrier absorption (FCA) of CdSe QDs. The nonlinear optical switching behaviour and reverse saturable absorption makes CdSe QDs are good candidate for all-optical device and optical limiting applications.

  5. Active reflective components for adaptive optical zoom systems

    Science.gov (United States)

    Jungwirth, Matthew Edward Lewis

    This dissertation presents the theoretical and experimental exploration of active reflective components specifically for large-aperture adaptive optical zoom systems. An active reflective component can change its focal length by physically deforming its reflecting surface. Adaptive optical zoom (AOZ) utilizes active components in order to change magnification and achieve optical zoom, as opposed to traditional zooming systems that move elements along the optical axis. AOZ systems are theoretically examined using a novel optical design theory that enables a full-scale tradespace analysis, where optical design begins from a broad perspective and optimizes to a particular system. The theory applies existing strategies for telescope design and aberration simulation to AOZ, culminating in the design of a Cassegrain objective with a 3.3X zoom ratio and a 375mm entrance aperture. AOZ systems are experimentally examined with the development of a large-aperture active mirror constructed of a composite material called carbon fiber reinforced polymer (CFRP). The active CFRP mirror uses a novel actuation method to change radius of curvature, where actuators press against two annular rings placed on the mirror's back. This method enables the radius of curvature to increase from 2000mm to 2010mm. Closed-loop control maintains good optical performance of 1.05 waves peak-to-valley (with respect to a HeNe laser) when the active CFRP mirror is used in conjunction with a commercial deformable mirror.

  6. Wavefront reconstruction in adaptive optics systems using nonlinear multivariate splines

    NARCIS (Netherlands)

    De Visser, C.C.; Verhaegen, M.H.G.

    2012-01-01

    This paper presents a new method for zonal wavefront reconstruction (WFR) with application to adaptive optics systems. This new method, indicated as Spline based ABerration REconstruction (SABRE), uses bivariate simplex B-spline basis functions to reconstruct the wavefront using local wavefront slop

  7. MICADO : The E-ELT adaptive optics imaging camera

    NARCIS (Netherlands)

    Davies, Richard; Ageorges, N.; Barl, L.; Bedin, L. R.; Bender, R.; Bernardi, P.; Chapron, F.; Clenet, Y.; Deep, A.; Deul, E.; Drost, M.; Eisenhauer, F.; Falomo, R.; Fiorentino, G.; Förster Schreiber, N. M.; Gendron, E.; Genzel, R.; Gratadour, D.; Greggio, L.; Grupp, F.; Held, E.; Herbst, T.; Hess, H.-J.; Hubert, Z.; Jahnke, K.; Kuijken, K.; Lutz, D.; Magrin, D.; Muschielok, B.; Navarro, R.; Noyola, E.; Paumard, T.; Piotto, G.; Ragazzoni, R.; Renzini, A.; Rousset, G.; Rix, H.-W.; Saglia, R.; Tacconi, L.; Thiel, M.; Tolstoy, E.; Trippe, S.; Tromp, N.; Valentijn, E. A.; Verdoes Kleijn, G.; Wegner, M.; McLean, I.S.; Ramsay, S.K.; Takami, H.

    2010-01-01

    MICADO is the adaptive optics imaging camera for the E-ELT. It has been designed and optimised to be mounted to the LGS-MCAO system MAORY, and will provide diffraction limited imaging over a wide (~1 arcmin) field of view. For initial operations, it can also be used with its own simpler AO module th

  8. New algorithms for adaptive optics point-spread function reconstruction

    CERN Document Server

    Gendron, E; Fusco, T; Rousset, G; Gendron, Eric; Cl\\'{e}net, Yann; Fusco, Thierry

    2006-01-01

    Context. The knowledge of the point-spread function compensated by adaptive optics is of prime importance in several image restoration techniques such as deconvolution and astrometric/photometric algorithms. Wavefront-related data from the adaptive optics real-time computer can be used to accurately estimate the point-spread function in adaptive optics observations. The only point-spread function reconstruction algorithm implemented on astronomical adaptive optics system makes use of particular functions, named $U\\_{ij}$. These $U\\_{ij}$ functions are derived from the mirror modes, and their number is proportional to the square number of these mirror modes. Aims. We present here two new algorithms for point-spread function reconstruction that aim at suppressing the use of these $U\\_{ij}$ functions to avoid the storage of a large amount of data and to shorten the computation time of this PSF reconstruction. Methods. Both algorithms take advantage of the eigen decomposition of the residual parallel phase covari...

  9. Data-Driven Optimal Control for Adaptive Optics

    NARCIS (Netherlands)

    Hinnen, K.J.G.

    2007-01-01

    Adaptive optics (AO) is a technique to actively correct the wavefront distortions introduced in a light beam as it propagates through a turbulent medium. Nowadays, it is commonly applied in ground-based telescopes to counteract the devastating effect of atmospheric turbulence. This thesis focuses on

  10. On the influence of the Illuminati in astronomical adaptive optics

    CERN Document Server

    Morzinski, Katie M

    2012-01-01

    Astronomical adaptive optics (AO) has come into its own. Major O/IR telescopes are achieving diffraction-limited imaging; major facilities are being built with AO as an integral part. To the layperson, it may seem that AO has developed along a serpentine path. However, with a little illumination, the mark of Galileo's heirs becomes apparent in explaining the success of AO.

  11. Fluorescence in situ hybridization on human metaphase chromosomes detected by near-field scanning optical microscopy

    NARCIS (Netherlands)

    Moers, M.H.P.; Kalle, W.H.J.; Ruiter, A.G.T.; Wiegant, J.C.A.G.; Raap, A.K.; Greve, J.; Grooth, de B.G.; Hulst, van N.F.

    1996-01-01

    Fluorescence in situ hybridization o­n human metaphase chromosomes is detected by near-field scanning optical microscopy. This combination of cytochemical and scanning probe techniques enables the localization and identification of several fluorescently labelled genomic DNA fragments o­n a single ch

  12. Scanning probe and optical tweezer investigations of biomolecular interactions

    Energy Technology Data Exchange (ETDEWEB)

    Rigby-Singleton, Shellie

    2002-07-01

    A complex array of intermolecular forces controls the interactions between and within biological molecules. The desire to empirically explore the fundamental forces has led to the development of several biophysical techniques. Of these, the atomic force microscope (AFM) and the optical tweezers have been employed throughout this thesis to monitor the intermolecular forces involved in biomolecular interactions. The AFM is a well-established force sensing technique capable of measuring biomolecular interactions at a single molecule level. However, its versatility has not been extrapolated to the investigation of a drug-enzyme complex. The energy landscape for the force induced dissociation of the DHFR-methotrexate complex was studied. Revealing an energy barrier to dissociation located {approx}0.3 nm from the bound state. Unfortunately, the AFM has a limited range of accessible loading rates and in order to profile the complete energy landscape alternative force sensing instrumentation should be considered, for example the BFP and optical tweezers. Thus, this thesis outlines the development and construction an optical trap capable of measuring intermolecular forces between biomolecules at the single molecule level. To demonstrate the force sensing abilities of the optical set up, proof of principle measurements were performed which investigate the interactions between proteins and polymer surfaces subjected to varying degrees of argon plasma treatment. Complementary data was gained from measurements performed independently by the AFM. Changes in polymer resistance to proteins as a response to changes in polymer surface chemistry were detected utilising both AFM and optical tweezers measurements. Finally, the AFM and optical tweezers were employed as ultrasensitive biosensors. Single molecule investigations of the antibody-antigen interaction between the cardiac troponin I marker and its complementary antibody, reveals the impact therapeutic concentrations of heparin

  13. Adaptive AFM scan speed control for high aspect ratio fast structure tracking

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Ahmad; Schuh, Andreas; Rangelow, Ivo W. [Department of Microelectronic and Nanoelectronic Systems, Faculty of Electrical Engineering and Information Technology Ilmenau University of Technology, Gustav-Kirchhoffstr. 1, 98684 Ilmenau (Germany)

    2014-10-15

    Improved imaging rates in Atomic Force Microscopes (AFM) are of high interest for disciplines such as life sciences and failure analysis of semiconductor wafers, where the sample topology shows high aspect ratios. Also, fast imaging is necessary to cover a large surface under investigation in reasonable times. Since AFMs are composed of mechanical components, they are associated with comparably low resonance frequencies that undermine the effort to increase the acquisition rates. In particular, high and steep structures are difficult to follow, which causes the cantilever to temporarily loose contact to or crash into the sample. Here, we report on a novel approach that does not affect the scanner dynamics, but adapts the lateral scanning speed of the scanner. The controller monitors the control error signal and, only when necessary, decreases the scan speed to allow the z-piezo more time to react to changes in the sample's topography. In this case, the overall imaging rate can be significantly increased, because a general scan speed trade-off decision is not needed and smooth areas are scanned fast. In contrast to methods trying to increase the z-piezo bandwidth, our method is a comparably simple approach that can be easily adapted to standard systems.

  14. Optic flow improves adaptability of spatiotemporal characteristics during split-belt locomotor adaptation with tactile stimulation.

    Science.gov (United States)

    Eikema, Diderik Jan A; Chien, Jung Hung; Stergiou, Nicholas; Myers, Sara A; Scott-Pandorf, Melissa M; Bloomberg, Jacob J; Mukherjee, Mukul

    2016-02-01

    Human locomotor adaptation requires feedback and feed-forward control processes to maintain an appropriate walking pattern. Adaptation may require the use of visual and proprioceptive input to decode altered movement dynamics and generate an appropriate response. After a person transfers from an extreme sensory environment and back, as astronauts do when they return from spaceflight, the prolonged period required for re-adaptation can pose a significant burden. In our previous paper, we showed that plantar tactile vibration during a split-belt adaptation task did not interfere with the treadmill adaptation however, larger overground transfer effects with a slower decay resulted. Such effects, in the absence of visual feedback (of motion) and perturbation of tactile feedback, are believed to be due to a higher proprioceptive gain because, in the absence of relevant external dynamic cues such as optic flow, reliance on body-based cues is enhanced during gait tasks through multisensory integration. In this study, we therefore investigated the effect of optic flow on tactile-stimulated split-belt adaptation as a paradigm to facilitate the sensorimotor adaptation process. Twenty healthy young adults, separated into two matched groups, participated in the study. All participants performed an overground walking trial followed by a split-belt treadmill adaptation protocol. The tactile group (TC) received vibratory plantar tactile stimulation only, whereas the virtual reality and tactile group (VRT) received an additional concurrent visual stimulation: a moving virtual corridor, inducing perceived self-motion. A post-treadmill overground trial was performed to determine adaptation transfer. Interlimb coordination of spatiotemporal and kinetic variables was quantified using symmetry indices and analyzed using repeated-measures ANOVA. Marked changes of step length characteristics were observed in both groups during split-belt adaptation. Stance and swing time symmetries were

  15. Adaptive wide-field optical tomography

    Science.gov (United States)

    Venugopal, Vivek; Intes, Xavier

    2013-03-01

    We describe a wide-field optical tomography technique, which allows the measurement-guided optimization of illumination patterns for enhanced reconstruction performances. The iterative optimization of the excitation pattern aims at reducing the dynamic range in photons transmitted through biological tissue. It increases the number of measurements collected with high photon counts resulting in a dataset with improved tomographic information. Herein, this imaging technique is applied to time-resolved fluorescence molecular tomography for preclinical studies. First, the merit of this approach is tested by in silico studies in a synthetic small animal model for typical illumination patterns. Second, the applicability of this approach in tomographic imaging is validated in vitro using a small animal phantom with two fluorescent capillaries occluded by a highly absorbing inclusion. The simulation study demonstrates an improvement of signal transmitted (˜2 orders of magnitude) through the central portion of the small animal model for all patterns considered. A corresponding improvement in the signal at the emission wavelength by 1.6 orders of magnitude demonstrates the applicability of this technique for fluorescence molecular tomography. The successful discrimination and localization (˜1 mm error) of the two objects with higher resolution using the optimized patterns compared with nonoptimized illumination establishes the improvement in reconstruction performance when using this technique.

  16. Adaptive optics assisted Fourier domain OCT with balanced detection

    Science.gov (United States)

    Meadway, A.; Bradu, A.; Hathaway, M.; Van der Jeught, S.; Rosen, R. B.; Podoleanu, A. Gh.

    2011-03-01

    Two factors are of importance to optical coherence tomography (OCT), resolution and sensitivity. Adaptive optics improves the resolution of a system by correcting for aberrations causing distortions in the wave-front. Balanced detection has been used in time domain OCT systems by removing excess photon noise, however it has not been used in Fourier domain systems, as the cameras used in the spectrometers saturated before excess photon noise becomes a problem. Advances in camera technology mean that this is no longer the case and balanced detection can now be used to improve the signal to noise ratio in a Fourier domain (FD) OCT system. An FD-OCT system, enhanced with adaptive optics, is presented and is used to show the improvement that balanced detection can provide. The signal to noise ratios of single camera detection and balanced detection are assessed and in-vivo retinal images are acquired to demonstrate better image quality when using balance detection.

  17. The AVES adaptive optics spectrograph for the VLT: status report

    Science.gov (United States)

    Pallavicini, Roberto; Delabre, Bernard; Pasquini, Luca; Zerbi, Filippo M.; Bonanno, Giovanni; Comari, Maurizio; Conconi, Paolo; Mazzoleni, Ruben; Santin, Paolo; Damiani, Francesco; Di Marcantonio, Paolo; Franchini, Mariagrazia; Spano, Paolo; Bonifacio, P.; Catalano, Santo; Molaro, Paolo P.; Randich, S.; Rodono, Marcello

    2003-03-01

    We report on the status of AVES, the Adaptive-optics Visual Echelle Spectrograph proposed for the secondary port of the Nasmyth Adaptive Optics System (NAOS) recently installed at the VLT. AVES is an intermediate resolution (R ≍ 16,000) high-efficiency fixed- format echelle spectrograph which operates in the spectral band 500 - 1,000 nm. In addition to a high intrinsic efficiency, comparable to that of ESI at Keck II, it takes advantage of the adaptive optics correction provided by NAOS to reduce the sky and detector contribution in background-limited observations of weak sources, thus allowing a further magnitude gain with respect to comparable non-adaptive optics spectrographs. Simulations show that the instrument will be capable of reaching a magnitude V = 22.5 at S/N > 10 in two hours, two magnitudes weaker than GIRAFFE at the same resolution and 3 magnitudes weaker than the higher resolution UVES spectrograph. Imaging and coronographic functions have also been implemented in the design. We present the results of the final design study and we dicuss the technical and operational issues related to its implementation at the VLT as a visitor instrument. We also discuss the possibility of using a scaled-up non-adaptive optics version of the same design as an element of a double- or triple-arm intermediate-resolution spectrograph for the VLT. Such an option looks attractive in the context of a high-efficiency large-bandwidth (320 - 1,500 nm) spectrograph ("fast-shooter") being considered by ESO as a 2nd-generation VLT instrument.

  18. Non-scanning, non-interferometric, three-dimensional optical profilometer with nanometer resolution

    Institute of Scientific and Technical Information of China (English)

    Chen-Tai Tan; Yuan-Sheng Chan; Jhao-An Chen; Teh-Chao Liao; Ming-Hung Chiu

    2011-01-01

    A non-scanning, non-interferometric, three-dimensional (3D) optical profilometer based on geometric optics, critical angle principle, and the use of a charge-coupled device (CCD) camera is presented. The surface profile of the test specimen can be transferred into the reflectance profile. The reflectance profile, obtained from a CCD, is the ratio of the intensity at the critical angle to the intensity obtained at the total internal reflection angle. The optical profilometer provides a sub-micron measuring range with nanometer resolution and can be used to measure roughness or surface defects in real time.%A non-scanning,non-interferometric,three-dimensional (3D) optical profilometer based on geometric optics,critical angle principle,and the use of a charge-coupled device (CCD) camera is presented.The surface profile of the test specimen can be transferred into the reflectance profile.The reflectance profile,obtained from a CCD,is the ratio of the intensity at the critical angle to the intensity obtained at the total internal reflection angle.The optical profilometer provides a sub-micron measuring range with nanometer resolution and can be used to measure roughness or surface defects in real time.Optical profilometers may be distinguished into two types:scanning and non-scanning types.Scanning profilometers have better axial resolution but spend much time in measuring.For three-dimensional (3D) surface profile measurement,scanning approaches such as confocal microscopy[1- 3],or near-field microscopy[4],which have high axial and lateral resolutions for measuring a snall scanned area,arc usually not used to measure a large surface profile.Non-scanning approaches such as the noninterferometric method[5,6],interference microscopy[7-10],and second-harmonic generation[11],can measure a large surface field,but the surface height calculation based on the fringe analysis is more complex.

  19. Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

    OpenAIRE

    Jian, Yifan; Xu, Jing; Gradowski, Martin A.; Bonora, Stefano; Zawadzki, Robert J.; Sarunic, Marinko V.

    2014-01-01

    We present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimi...

  20. Polarization contrast in fluorescence scanning near-field optical microscopy in reflection

    NARCIS (Netherlands)

    Jalocha, A.; Hulst, van N.F.

    1995-01-01

    Polarization contrast is presented in fluorescence images of a Langmuir-Blodgett monolayer obtained with a scanning near-field optical microscope operated in reflection. A tapered optical fiber is used both to excite and to collect the fluorescence. The lateral resolution in the reflection fluoresce

  1. Heterodyne method of apertureless near-field scanning optical microscopy on periodic gold nanowells.

    Energy Technology Data Exchange (ETDEWEB)

    Hall, J. E.; Wiederrecht, G. P.; Gray, S. K.; Chang, S.-H.; Jeon, S.; Rogers, J. A.; Bachelot, R.; Royer, P.; Univ. of Illinois; Univ. of Technology at Troyes; Inst. of Electro-Optical Science and Engineering

    2007-04-02

    Heterodyne detection for apertureless near-field scanning optical microscopy was used to study periodic gold nanowell arrays. Optical near-field amplitude and phase signals were obtained simultaneously with the topography of the gold nanowells and with different polarizations. Theoretical calculations of the near-fields were consistent with the experiments; in particular, the calculated amplitudes were in especially good agreement. The heterodyne method is shown to be particularly effective for these types of periodic photonic structures and other highly scattering media, which can overwhelm the near-field scattered signal when conventional apertureless near-field scanning optical microscopy is used.

  2. Picosecond optical nonlinearities in symmetrical and unsymmetrical phthalocyanines studied using the Z-scan technique

    Indian Academy of Sciences (India)

    S Venugopal Rao; P T Anusha; L Giribabu; Surya P Tewari

    2010-11-01

    We present our experimental results on the picosecond nonlinear optical (NLO) studies of symmetrical and unsymmetrical phthalocyanines, examined using the Z-scan technique. Both the open-aperture and closed-aperture Z-scan curves for three samples were recorded and the nonlinear coefficients were extracted from the theoretical fits. The nonlinear absorption/refraction contribution from the solvent was also identified. The observed open aperture behaviour for these molecules is understood in terms of the absorption coefficients of these molecules near 800 nm and the peak intensities used. It is established that these phthalocyanines exhibit large optical nonlinearities and, hence, are suitable for optical limiting applications.

  3. Detection of Luminescent Nanodiamonds Using a Scanning Near-Field Optical Microscope with an Aperture Probe

    Science.gov (United States)

    Shershulin, V. A.; Samoylenko, S. R.; Shenderova, O. A.; Vlasov, I. I.; Konov, V. I.

    2016-09-01

    Scanning near-fi eld optical microscopy (SNOM) with an aperture probe has been used to map the luminescence of isolated submicron diamond crystallites. 532-nm laser light was used to excite luminescence of nitrogen-vacancy (NV) centers. The sizes of the analyzed diamond crystallites were determined with an atomic-force microscope. The optical resolution for the lateral dimensions of the luminescing diamond crystallites was doubled on going from confocal luminescence microscopy to scanning near-fi eld optical microscopy with a 290-nm probe aperture diameter.

  4. Differential geometry of the ruled surfaces optically generated by mirror scanning devices: II. Generation of helicoids and hyperbolic paraboloids.

    Science.gov (United States)

    Li, Yajun

    2011-06-01

    The theory developed in Part I of this study [Y. Li, "Differential geometry of the ruled surfaces optically generated by mirror-scanning devices. I. Intrinsic and extrinsic properties of the scan field," J. Opt. Soc. Am. A28, 667 (2011)] for the ruled surfaces optically generated by single-mirror scanning devices is extended to multimirror scanning systems for an investigation of optical generation of the well-known ruled surfaces, such as helicoid, Plücker's conoid, and hyperbolic paraboloid.

  5. Scanning optical pyrometer for measuring temperatures in hollow cathodes

    OpenAIRE

    Polk, J. E.; Marrese-Reading, C. M.; Thornber, B.; Dang, L.; Johnson, L. K.; Katz, I

    2007-01-01

    Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measu...

  6. Proton irradiation of liquid crystal based adaptive optical devices

    International Nuclear Information System (INIS)

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (1010p/cm2). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  7. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    Science.gov (United States)

    Naser, Mohamed A.; Patterson, Michael S.; Wong, John W.

    2014-04-01

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation.

  8. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    International Nuclear Information System (INIS)

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation. (paper)

  9. Genomewide scan for adaptive differentiation along altitudinal gradient in the Andrew's toad Bufo andrewsi.

    Science.gov (United States)

    Guo, Baocheng; Lu, Di; Liao, Wen Bo; Merilä, Juha

    2016-08-01

    Recent studies of humans, dogs and rodents have started to discover the genetic underpinnings of high altitude adaptations, yet amphibians have received little attention in this respect. To identify possible signatures of adaptation to altitude, we performed a genome scan of 15 557 single nucleotide polymorphisms (SNPs) obtained with restriction site-associated DNA sequencing of pooled samples from 11 populations of Andrew's toad (Bufo andrewsi) from the edge of the Tibetan Plateau, spanning an altitudinal gradient from 1690 to 2768 m.a.s.l. We discovered significant geographic differentiation among all sites, with an average FST   = 0.023 across all SNPs. Apart from clear patterns of isolation by distance, we discovered numerous outlier SNPs showing strong associations with variation in altitude (1394 SNPs), average annual temperature (1859 SNPs) or both (1051 SNPs). Levels and patterns of genetic differentiation in these SNPs were consistent with the hypothesis that they have been subject to directional selection and reflect adaptation to altitudinal variation among the study sites. Genes with footprints of selection were significantly enriched in binding and metabolic processes. Several genes potentially related to high altitude adaptation were identified, although the identity and functional significance of most genomic targets of selection remain unknown. In general, the results provide genomic support for results of earlier common garden and low coverage genetic studies that have uncovered substantial adaptive differentiation along altitudinal and latitudinal gradients in amphibians. PMID:27289071

  10. Adaptive circle-ellipse fitting method for estimating tree diameter based on single terrestrial laser scanning

    Science.gov (United States)

    Bu, Guochao; Wang, Pei

    2016-04-01

    Terrestrial laser scanning (TLS) has been used to extract accurate forest biophysical parameters for inventory purposes. The diameter at breast height (DBH) is a key parameter for individual trees because it has the potential for modeling the height, volume, biomass, and carbon sequestration potential of the tree based on empirical allometric scaling equations. In order to extract the DBH from the single-scan data of TLS automatically and accurately within a certain range, we proposed an adaptive circle-ellipse fitting method based on the point cloud transect. This proposed method can correct the error caused by the simple circle fitting method when a tree is slanted. A slanted tree was detected by the circle-ellipse fitting analysis, then the corresponding slant angle was found based on the ellipse fitting result. With this information, the DBH of the trees could be recalculated based on reslicing the point cloud data at breast height. Artificial stem data simulated by a cylindrical model of leaning trees and the scanning data acquired with the RIEGL VZ-400 were used to test the proposed adaptive fitting method. The results shown that the proposed method can detect the trees and accurately estimate the DBH for leaning trees.

  11. Fast calibration of high-order adaptive optics systems.

    Science.gov (United States)

    Kasper, Markus; Fedrigo, Enrico; Looze, Douglas P; Bonnet, Henri; Ivanescu, Liviu; Oberti, Sylvain

    2004-06-01

    We present a new method of calibrating adaptive optics systems that greatly reduces the required calibration time or, equivalently, improves the signal-to-noise ratio. The method uses an optimized actuation scheme with Hadamard patterns and does not scale with the number of actuators for a given noise level in the wavefront sensor channels. It is therefore highly desirable for high-order systems and/or adaptive secondary systems on a telescope without a Gregorian focal plane. In the latter case, the measurement noise is increased by the effects of the turbulent atmosphere when one is calibrating on a natural guide star. PMID:15191182

  12. Infinite impulse response modal filtering in visible adaptive optics

    CERN Document Server

    Agapito, G; Quirós-Pacheco, F; Puglisi, A; Esposito, S

    2012-01-01

    Diffraction limited resolution adaptive optics (AO) correction in visible wavelengths requires a high performance control. In this paper we investigate infinite impulse response filters that optimize the wavefront correction: we tested these algorithms through full numerical simulations of a single-conjugate AO system comprising an adaptive secondary mirror with 1127 actuators and a pyramid wavefront sensor (WFS). The actual practicability of the algorithms depends on both robustness and knowledge of the real system: errors in the system model may even worsen the performance. In particular we checked the robustness of the algorithms in different conditions, proving that the proposed method can reject both disturbance and calibration errors.

  13. Infinite impulse response modal filtering in visible adaptive optics

    Science.gov (United States)

    Agapito, G.; Arcidiacono, C.; Quirós-Pacheco, F.; Puglisi, A.; Esposito, S.

    2012-07-01

    Diffraction limited resolution adaptive optics (AO) correction in visible wavelengths requires a high performance control. In this paper we investigate infinite impulse response filters that optimize the wavefront correction: we tested these algorithms through full numerical simulations of a single-conjugate AO system comprising an adaptive secondary mirror with 1127 actuators and a pyramid wavefront sensor (WFS). The actual practicability of the algorithms depends on both robustness and knowledge of the real system: errors in the system model may even worsen the performance. In particular we checked the robustness of the algorithms in different conditions, proving that the proposed method can reject both disturbance and calibration errors.

  14. Spot Weight Adaptation for Moving Target in Spot Scanning Proton Therapy

    Directory of Open Access Journals (Sweden)

    Paul eMorel

    2015-05-01

    Full Text Available Purpose: This study describes a real-time spot weight adaptation method in spot-scanning proton therapy for moving target or moving patient, so that the resultant dose distribution closely matches the planned dose distribution. Materials and Methods: The method proposed in this study adapts the weight (MU of the delivering pencil beam to that of the target spot it will actually hit during patient/target motion. The target spot a certain delivering pencil beam may hit relies on patient monitoring and/or motion modeling using four-dimensional (4D CT. After the adapted delivery, the required total weight (MU for this target spot is then subtracted from the planned value. With continuous patient motion and continuous spot scanning, the planned doses to all target spots will eventually be all fulfilled. In a proof-of-principle test, a lung case was presented with realistic temporal and motion parameters; the resultant dose distribution using spot weight adaptation was compared to that without using this method. The impact of the real-time patient/target position tracking or prediction was also investigated.Results: For moderate motion (i.e., mean amplitude 0.5 cm, D95% to the planning target volume (PTV was only 81.5% of the prescription (RX dose; with spot weight adaptation PTV D95% achieves 97.7%RX. For large motion amplitude (i.e., 1.5 cm, without spot weight adaptation PTV D95% is only 42.9% of RX; with spot weight adaptation, PTV D95% achieves 97.7%RX. Larger errors in patient/target position tracking or prediction led to worse final target coverage; an error of 3mm or smaller in patient/target position tracking is preferred. Conclusion: The proposed spot weight adaptation method was able to deliver the planned dose distribution and maintain target coverage when patient motion was involved. The successful implementation of this method would rely on accurate monitoring or prediction of patient/target motion.

  15. Adaptive optics for improved retinal surgery and diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Humayun, M S; Sadda, S R; Thompson, C A; Olivier, S S; Kartz, M W

    2000-08-21

    It is now possible to field a compact adaptive optics (AO) system on a surgical microscope for use in retinal diagnostics and surgery. Recent developments in integrated circuit technology and optical photonics have led to the capability of building an AO system that is compact and significantly less expensive than traditional AO systems. It is foreseen that such an AO system can be integrated into a surgical microscope while maintaining a package size of a lunchbox. A prototype device can be developed in a manner that lends itself well to large-scale manufacturing.

  16. Adaptive Data Rates for Flexible Transceivers in Optical Networks

    Directory of Open Access Journals (Sweden)

    Brian Thomas Teipen

    2012-05-01

    Full Text Available Efforts towards commercializing higher-speed optical transmission have demonstrated the need for advanced modulation formats, several of which require similar transceiver hardware architecture. Adaptive transceivers can be built to have a number of possible operational configurations selected by software. Such software-defined transceiver configurations can create specific modulation formats to support sets of data rates, corresponding tolerances to system impairments, and sets of electronic digital signal processing schemes chosen to best function in a given network environment. In this paper, we discuss possibilities and advantages of reconfigurable, bit-rate flexible transceivers, and their potential applications in future optical networks.

  17. Nonlinear Optical Interactions in Bacteriorhodopsin Using Z-Scan

    Science.gov (United States)

    Aranda, Francisco J.; Rao, Devulapalli V. G. L. N.; Wong, Chi L.; Zhou, Ping; Chen, Zhong; Akkara, Joseph A.; Kaplan, David L.; Roach, Joseph F.

    1995-06-01

    Nonlinear refractive index coefficient n2 of bacteriorhodopsin suspensions in water is measured by the Z-scan technique with a low power continuous wave laser at 647.1 manometer wavelength. Our results indicate that both the magnitude and the sign of n2 depend strongly on the light intensity. Negative values for n2 are obtained for on axis laser irradiance at the focus above 3 W/cm2. The observed self-defocusing phenomena can be attributed to the index change due to the light induced transition between the photochromic states. The results elucidate the origin of n2 and offer a plausible explanation for the differences in the reported n2 measurements.

  18. Adaptation technology between IP layer and optical layer in optical Internet

    Science.gov (United States)

    Ji, Yuefeng; Li, Hua; Sun, Yongmei

    2001-10-01

    Wavelength division multiplexing (WDM) optical network provides a platform with high bandwidth capacity and is supposed to be the backbone infrastructure supporting the next-generation high-speed multi-service networks (ATM, IP, etc.). In the foreseeable future, IP will be the predominant data traffic, to make fully use of the bandwidth of the WDM optical network, many attentions have been focused on IP over WDM, which has been proposed as the most promising technology for new kind of network, so-called Optical Internet. According to OSI model, IP is in the 3rd layer (network layer) and optical network is in the 1st layer (physical layer), so the key issue is what adaptation technology should be used in the 2nd layer (data link layer). In this paper, firstly, we analyze and compare the current adaptation technologies used in backbone network nowadays. Secondly, aiming at the drawbacks of above technologies, we present a novel adaptation protocol (DONA) between IP layer and optical layer in Optical Internet and describe it in details. Thirdly, the gigabit transmission adapter (GTA) we accomplished based on the novel protocol is described. Finally, we set up an experiment platform to apply and verify the DONA and GTA, the results and conclusions of the experiment are given.

  19. Laser Guide Star Adaptive Optics without Tip-tilt

    CERN Document Server

    Davies, R; Lidman, C; Louarn, M Le; Kasper, M; Förster-Schreiber, N M; Roccatagliata, V; Ageorges, N; Amico, P; Dumas, C; Mannucci, F

    2008-01-01

    Adaptive optics (AO) systems allow a telescope to reach its diffraction limit at near infrared wavelengths. But to achieve this, a bright natural guide star (NGS) is needed for the wavefront sensing, severely limiting the fraction of the sky over which AO can be used. To some extent this can be overcome with a laser guide star (LGS). While the laser can be pointed anywhere in the sky, one still needs to have a natural star, albeit fainter, reasonably close to correct the image motion (tip-tilt) to which laser guide stars are insensitive. There are in fact many astronomical targets without suitable tip-tilt stars, but for which the enhanced resolution obtained with the Laser Guide Star Facility (LGSF) would still be very beneficial. This article explores what adaptive optics performance one might expect if one dispenses with the tip-tilt star, and in what situations this mode of observing might be needed.

  20. Neptune and Titan Observed with Keck Telescope Adaptive Optics

    Energy Technology Data Exchange (ETDEWEB)

    Max, C.E.; Macintosh, B.A.; Gibbard, S.; Gavel, D.T.; Roe, H.; De Pater, I.; Ghez, A.M.; Acton, S.; Wizinowich, P.L.; Lai, O.

    2000-05-05

    The authors report on observations taken during engineering science validation time using the new adaptive optics system at the 10-m Keck II Telescope. They observe Neptune and Titan at near-infrared wavelengths. These objects are ideal for adaptive optics imaging because they are bright and small, yet have many diffraction-limited resolution elements across their disks. In addition Neptune and Titan have prominent physical features, some of which change markedly with time. They have observed infrared-bright storms on Neptune, and very low-albedo surface regions on Titan, Saturn's largest moon, Spatial resolution on Neptune and Titan was 0.05-0.06 and 0.04-0.05 arc sec, respectively.

  1. Laser Tomography Adaptive Optics (LTAO): A performance study

    CERN Document Server

    Tatulli, E

    2013-01-01

    We present an analytical derivation of the on-axis performance of Adaptive Optics systems using a given number of guide stars of arbitrary altitude, distributed at arbitrary angular positions in the sky. The expressions of the residual error are given for cases of both continuous and discrete turbulent atmospheric profiles. Assuming Shack-Hartmann wavefront sensing with circular apertures, we demonstrate that the error is formally described by integrals of products of three Bessel functions. We compare the performance of Adaptive Optics correction when using natural, Sodium or Rayleigh laser guide stars. For small diameter class telescopes (~5m), we show that a few number of Rayleigh beacons can provide similar performance to that of a single Sodium laser, for a lower overall cost of the instrument. For bigger apertures, using Rayleigh stars may not be such a suitable alternative because of the too severe cone effect that drastically degrades the quality of the correction.

  2. LIFT: analysis of performance in a laser assisted adaptive optics

    Science.gov (United States)

    Plantet, Cedric; Meimon, Serge; Conan, Jean-Marc; Neichel, Benoît; Fusco, Thierry

    2014-08-01

    Laser assisted adaptive optics systems rely on Laser Guide Star (LGS) Wave-Front Sensors (WFS) for high order aberration measurements, and rely on Natural Guide Stars (NGS) WFS to complement the measurements on low orders such as tip-tilt and focus. The sky-coverage of the whole system is therefore related to the limiting magnitude of the NGS WFS. We have recently proposed LIFT, a novel phase retrieval WFS technique, that allows a 1 magnitude gain over the usually used 2×2 Shack-Hartmann WFS. After an in-lab validation, LIFT's concept has been demonstrated on sky in open loop on GeMS (the Gemini Multiconjugate adaptive optics System at Gemini South). To complete its validation, LIFT now needs to be operated in closed loop in a laser assisted adaptive optics system. The present work gives a detailed analysis of LIFT's behavior in presence of high order residuals and how to limit aliasing effects on the tip/tilt/focus estimation. Also, we study the high orders' impact on noise propagation. For this purpose, we simulate a multiconjugate adaptive optics loop representative of a GeMS-like 5 LGS configuration. The residual high orders are derived from a Fourier based simulation. We demonstrate that LIFT keeps a high performance gain over the Shack-Hartmann 2×2 whatever the turbulence conditions. Finally, we show the first simulation of a closed loop with LIFT estimating turbulent tip/tilt and focus residuals that could be induced by sodium layer's altitude variations.

  3. Scanning optical pyrometer for measuring temperatures in hollow cathodes

    International Nuclear Information System (INIS)

    Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measurements of the external temperature during cathode operation and are used to calibrate the pyrometer system in situ with a small oven enclosing the externally heated cathode. The diagnostic method and initial measurements of the temperature distribution in a hollow cathode are discussed

  4. Differential geometry of the ruled surfaces optically generated by mirror-scanning devices. I. Intrinsic and extrinsic properties of the scan field.

    Science.gov (United States)

    Li, Yajun

    2011-04-01

    Rectilinear propagation of light rays in homogeneous isotropic media makes it possible for optical generation of ruled surfaces as the ray is deflected by a rotatable mirror. Scan patterns on a plane or curved surface are merely curves on the ruled surface. Based on this understanding, structures of the scan fields produced by mirror-scanning devices of different configurations are investigated in terms of differential geometry. Expressions of the first and second fundamental coefficients and the first and second Gauss differential forms are given for an investigation of the intrinsic properties of the optically generated ruled surfaces. The Plücker ruled conoid is then generalized for mathematical modeling of the scan fields produced by single-mirror scanning devices of different configurations. Part II will be devoted to a study of multi-mirror scanning systems for optical generation of well-known ruled surfaces such as helicoids and hyperbolic paraboloids.

  5. Adaptive optics with pupil tracking for high resolution retinal imaging.

    Science.gov (United States)

    Sahin, Betul; Lamory, Barbara; Levecq, Xavier; Harms, Fabrice; Dainty, Chris

    2012-02-01

    Adaptive optics, when integrated into retinal imaging systems, compensates for rapidly changing ocular aberrations in real time and results in improved high resolution images that reveal the photoreceptor mosaic. Imaging the retina at high resolution has numerous potential medical applications, and yet for the development of commercial products that can be used in the clinic, the complexity and high cost of the present research systems have to be addressed. We present a new method to control the deformable mirror in real time based on pupil tracking measurements which uses the default camera for the alignment of the eye in the retinal imaging system and requires no extra cost or hardware. We also present the first experiments done with a compact adaptive optics flood illumination fundus camera where it was possible to compensate for the higher order aberrations of a moving model eye and in vivo in real time based on pupil tracking measurements, without the real time contribution of a wavefront sensor. As an outcome of this research, we showed that pupil tracking can be effectively used as a low cost and practical adaptive optics tool for high resolution retinal imaging because eye movements constitute an important part of the ocular wavefront dynamics.

  6. Stellar populations from adaptive optics observations four test cases

    CERN Document Server

    Bedding, T R; Courbin, F; Sams, B J

    1997-01-01

    We describe a first attempt to apply adaptive optics to the study of resolved stellar populations in galaxies. Advantages over traditional approaches are (i) improved spatial resolution and point-source sensitivity through adaptive optics, and (ii) use of the near-infrared region, where the peak of the spectral energy distribution for old populations is found. Disadvantages are the small area covered and the need for excellent seeing. We made observations with the ADONIS system at the European Southern Observatory of the peculiar elliptical galaxy NGC 5128; the irregular galaxy IC 5152 (a possible outer member of the Local Group); the Sc galaxy NGC 300 (a member of the Sculptor group); and the Sgr window in the bulge of the Milky Way. These different fields give excellent test cases for the potential of adaptive optics. In the first two cases, we failed to obtain photometry of individual stars, which would have required excellent seeing. For NGC 300 we measured magnitudes for nine individual supergiants (H = ...

  7. Optimizing Photon Collection from Point Sources with Adaptive Optics

    Science.gov (United States)

    Hill, Alexander; Hervas, David; Nash, Joseph; Graham, Martin; Burgers, Alexander; Paudel, Uttam; Steel, Duncan; Kwiat, Paul

    2015-05-01

    Collection of light from point-like sources is typically poor due to the optical aberrations present with very high numerical-aperture optics. In the case of quantum dots, the emitted mode is nonisotropic and may be quite difficult to couple into single- or even few-mode fiber. Wavefront aberrations can be corrected using adaptive optics at the classical level by analyzing the wavefront directly (e.g., with a Shack-Hartmann sensor); however, these techniques are not feasible at the single-photon level. We present a new technique for adaptive optics with single photons using a genetic algorithm to optimize collection from point emitters with a deformable mirror. We first demonstrate our technique for improving coupling from a subwavelength pinhole, which simulates isotropic emission from a point source. We then apply our technique in situto InAs/GaAs quantum dots, obtaining coupling increases of up to 50% even in the presence of an artificial source of drift.

  8. Lens-based wavefront sensorless adaptive optics swept source OCT

    Science.gov (United States)

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J.; Bonora, Stefano; Sarunic, Marinko V.

    2016-06-01

    Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient’s eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects.

  9. Manufacturing of glassy thin shell for adaptive optics: results achieved

    Science.gov (United States)

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  10. Anisoplanatism in adaptive optics systems due to pupil aberrations

    Energy Technology Data Exchange (ETDEWEB)

    Bauman, B

    2005-08-01

    Adaptive optics systems typically include an optical relay that simultaneously images the science field to be corrected and also a set of pupil planes conjugate to the deformable mirror of the system. Often, in the optical spaces where DM's are placed, the pupils are aberrated, leading to a displacement and/or distortion of the pupil that varies according to field position--producing a type of anisoplanatism, i.e., a degradation of the AO correction with field angle. The pupil aberration phenomenon is described and expressed in terms of Seidel aberrations. An expression for anisoplanatism as a function of pupil distortion is derived, an example of an off-axis parabola is given, and a convenient method for controlling pupil-aberration-generated anisoplanatism is proposed.

  11. ScanSim: A tool for simulating optical-CT imaging

    OpenAIRE

    Oldham, Mark

    2010-01-01

    A software tool has been developed that can simulate image formation in a variety of optical-CT scanning configurations. The formalism of the simulation is introduced, including two main modes: a diverging point source mode, and a converging broad beam mode. Preliminary results are presented for scanning Presage dosimeters in both modes and immersed in refractive media of widely varying refractive index (RI), including air, water, and a fully matched medium. Pronounced differences in the edge...

  12. Toward endoscopes with no distal optics: video-rate scanning microscopy through a fiber bundle.

    Science.gov (United States)

    Andresen, Esben Ravn; Bouwmans, Géraud; Monneret, Serge; Rigneault, Hervé

    2013-03-01

    We report a step toward scanning endomicroscopy without distal optics. The focusing of the beam at the distal end of a fiber bundle is achieved by imposing a parabolic phase profile across the exit face with the aid of a spatial light modulator. We achieve video-rate images by galvanometric scanning of the phase tilt at the proximal end. The approach is made possible by the bundle, designed to have very low coupling between cores.

  13. Integrated modeling of the GMT laser tomography adaptive optics system

    Science.gov (United States)

    Piatrou, Piotr

    2014-08-01

    Laser Tomography Adaptive Optics (LTAO) is one of adaptive optics systems planned for the Giant Magellan Telescope (GMT). End-to-end simulation tools that are able to cope with the complexity and computational burden of the AO systems to be installed on the extremely large telescopes such as GMT prove to be an integral part of the GMT LTAO system development endeavors. SL95, the Fortran 95 Simulation Library, is one of the software tools successfully used for the LTAO system end-to-end simulations. The goal of SL95 project is to provide a complete set of generic, richly parameterized mathematical models for key elements of the segmented telescope wavefront control systems including both active and adaptive optics as well as the models for atmospheric turbulence, extended light sources like Laser Guide Stars (LGS), light propagation engines and closed-loop controllers. The library is implemented as a hierarchical collection of classes capable of mutual interaction, which allows one to assemble complex wavefront control system configurations with multiple interacting control channels. In this paper we demonstrate the SL95 capabilities by building an integrated end-to-end model of the GMT LTAO system with 7 control channels: LGS tomography with Adaptive Secondary and on-instrument deformable mirrors, tip-tilt and vibration control, LGS stabilization, LGS focus control, truth sensor-based dynamic noncommon path aberration rejection, pupil position control, SLODAR-like embedded turbulence profiler. The rich parameterization of the SL95 classes allows to build detailed error budgets propagating through the system multiple errors and perturbations such as turbulence-, telescope-, telescope misalignment-, segment phasing error-, non-common path-induced aberrations, sensor noises, deformable mirror-to-sensor mis-registration, vibration, temporal errors, etc. We will present a short description of the SL95 architecture, as well as the sample GMT LTAO system simulation

  14. Adaptive optics at the Subaru telescope: current capabilities and development

    Science.gov (United States)

    Guyon, Olivier; Hayano, Yutaka; Tamura, Motohide; Kudo, Tomoyuki; Oya, Shin; Minowa, Yosuke; Lai, Olivier; Jovanovic, Nemanja; Takato, Naruhisa; Kasdin, Jeremy; Groff, Tyler; Hayashi, Masahiko; Arimoto, Nobuo; Takami, Hideki; Bradley, Colin; Sugai, Hajime; Perrin, Guy; Tuthill, Peter; Mazin, Ben

    2014-08-01

    Current AO observations rely heavily on the AO188 instrument, a 188-elements system that can operate in natural or laser guide star (LGS) mode, and delivers diffraction-limited images in near-IR. In its LGS mode, laser light is transported from the solid state laser to the launch telescope by a single mode fiber. AO188 can feed several instruments: the infrared camera and spectrograph (IRCS), a high contrast imaging instrument (HiCIAO) or an optical integral field spectrograph (Kyoto-3DII). Adaptive optics development in support of exoplanet observations has been and continues to be very active. The Subaru Coronagraphic Extreme-AO (SCExAO) system, which combines extreme-AO correction with advanced coronagraphy, is in the commissioning phase, and will greatly increase Subaru Telescope's ability to image and study exoplanets. SCExAO currently feeds light to HiCIAO, and will soon be combined with the CHARIS integral field spectrograph and the fast frame MKIDs exoplanet camera, which have both been specifically designed for high contrast imaging. SCExAO also feeds two visible-light single pupil interferometers: VAMPIRES and FIRST. In parallel to these direct imaging activities, a near-IR high precision spectrograph (IRD) is under development for observing exoplanets with the radial velocity technique. Wide-field adaptive optics techniques are also being pursued. The RAVEN multi-object adaptive optics instrument was installed on Subaru telescope in early 2014. Subaru Telescope is also planning wide field imaging with ground-layer AO with the ULTIMATE-Subaru project.

  15. Measurement of Temperature Change in Nonlinear Optical Materials by Using the Z-Scan Technique

    Institute of Scientific and Technical Information of China (English)

    DONG Shu-Guang; YANG Jun-Yi; SHUI Min; YI Chuan-Xiang; LI Zhong-Guo; SONG Ying-Lin

    2011-01-01

    @@ Spatial and temporal changes of temperature in a novel polymer are investigated by using the Z-scan technique under ns laser pulse excitation.According to the open aperture Z-scan experimental results, the nonlinear absorption coefficient of the polymer is determined.By solving the diffusion equation of heat conduction induced by optical absorption, the spatial and temporal changes in temperature are obtained.This change in temperature drives the photo-acoustic and electromagnetic wave propagating in the polymer and induces the change in refractive index, which serves as a negative lens, and the closed aperture Z-scan shows a peak and valley profile.Based on the numerical calculation, we achieve a good fit to the closed-aperture Z-scan curve with an optimized nonlinear refractive index.This consistency attests the existence of temperature change in the solution, and the Z-scan technique is suitable to investigate this change in temperature.

  16. Synthetic aperture laser optical feedback imaging using a translational scanning with galvanometric mirrors

    OpenAIRE

    Glastre, Wilfried; Jacquin, Olivier; Hugon, Olivier; de Chatellus, Hugues Guillet; Lacot, Eric

    2012-01-01

    In this paper we present an experimental setup based on Laser Optical Feedback Imaging (LOFI) and on Synthetic Aperture (SA) with translational scanning by galvanometric mirrors for the purpose of making deep and resolved images through scattering media. We provide real 2D optical synthetic-aperture image of a fixed scattering target with a moving aperture and an isotropic resolution. We demonstrate theoretically and experimentally that we can keep microscope resolution beyond the working dis...

  17. Scanning near-field optical microscopy utilizing silicon nitride probe photoluminescence

    OpenAIRE

    Lulevich, V.; Ducker, W. A.

    2005-01-01

    We describe a simple method for performing high-resolution scanning near-field optical microscopy (SNOM). A commercial Si3N4 tip is illuminated by an intense light source, which causes the tip to emit redshifted (inelastically scattered) light. Part of the redshifted light passes through a sample, allowing transmission light microscopy. By simple modification of a commercial atomic force microscopes (AFM), we are able to image many different samples with high-resolution optical microscopy, ac...

  18. Full-color holographic 3D imaging system using color optical scanning holography

    Science.gov (United States)

    Kim, Hayan; Kim, You Seok; Kim, Taegeun

    2016-06-01

    We propose a full-color holographic three-dimensional imaging system that composes a recording stage, a transmission and processing stage and reconstruction stage. In recording stage, color optical scanning holography (OSH) records the complex RGB holograms of an object. In transmission and processing stage, the recorded complex RGB holograms are transmitted to the reconstruction stage after conversion to off-axis RGB holograms. In reconstruction stage, the off-axis RGB holograms are reconstructed optically.

  19. High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography

    Science.gov (United States)

    Olivier, Scot S.; Werner, John S.; Zawadzki, Robert J.; Laut, Sophie P.; Jones, Steven M.

    2010-09-07

    This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.

  20. Images of photoreceptors in living primate eyes using adaptive optics two-photon ophthalmoscopy.

    Science.gov (United States)

    Hunter, Jennifer J; Masella, Benjamin; Dubra, Alfredo; Sharma, Robin; Yin, Lu; Merigan, William H; Palczewska, Grazyna; Palczewski, Krzysztof; Williams, David R

    2010-01-01

    In vivo two-photon imaging through the pupil of the primate eye has the potential to become a useful tool for functional imaging of the retina. Two-photon excited fluorescence images of the macaque cone mosaic were obtained using a fluorescence adaptive optics scanning laser ophthalmoscope, overcoming the challenges of a low numerical aperture, imperfect optics of the eye, high required light levels, and eye motion. Although the specific fluorophores are as yet unknown, strong in vivo intrinsic fluorescence allowed images of the cone mosaic. Imaging intact ex vivo retina revealed that the strongest two-photon excited fluorescence signal comes from the cone inner segments. The fluorescence response increased following light stimulation, which could provide a functional measure of the effects of light on photoreceptors. PMID:21326644

  1. Graphite/Cyanate Ester Face Sheets for Adaptive Optics

    Science.gov (United States)

    Bennett, Harold; Shaffer, Joseph; Romeo, Robert

    2008-01-01

    It has been proposed that thin face sheets of wide-aperture deformable mirrors in adaptive-optics systems be made from a composite material consisting of cyanate ester filled with graphite. This composite material appears to offer an attractive alternative to low-thermal-expansion glasses that are used in some conventional optics and have been considered for adaptive-optics face sheets. Adaptive-optics face sheets are required to have maximum linear dimensions of the order of meters or even tens of meters for some astronomical applications. If the face sheets were to be made from low-thermal-expansion glasses, then they would also be required to have thicknesses of the order of a millimeter so as to obtain the optimum compromise between the stiffness needed for support and the flexibility needed to enable deformation to controlled shapes by use of actuators. It is difficult to make large glass sheets having thicknesses less than 3 mm, and 3-mm-thick glass sheets are too stiff to be deformable to the shapes typically required for correction of wavefronts of light that has traversed the terrestrial atmosphere. Moreover, the primary commercially produced candidate low-thermal-expansion glass is easily fractured when in the form of thin face sheets. Graphite-filled cyanate ester has relevant properties similar to those of the low-expansion glasses. These properties include a coefficient of thermal expansion (CTE) of the order of a hundredth of the CTEs of other typical mirror materials. The Young s modulus (which quantifies stiffness in tension and compression) of graphite-filled cyanate ester is also similar to the Young's moduli of low-thermal-expansion glasses. However, the fracture toughness of graphite-filled cyanate ester is much greater than that of the primary candidate low-thermal-expansion glass. Therefore, graphite-filled cyanate ester could be made into nearly unbreakable face sheets, having maximum linear dimensions greater than a meter and thicknesses of

  2. Beam shaping for laser-based adaptive optics in astronomy

    CERN Document Server

    Béchet, Clémentine; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

    2014-01-01

    The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics system (GeMS). A beam shaping concept with two deformable mirrors is investigated in order to provide automated optimization of the laser quality for astronomical AO. This study aims at demonstrating the correction of quasi-static aberrations of the laser, in both amplitude and phase, testing a prototype of this two-deformable mirror concept on GeMS. The paper presents the results of the preparatory study before the experimental phase. An algorithm to control amplitude and phase correction, based on phase retrieval techniques...

  3. The study of lossy compressive method with different interpolation for holographic reconstruction in optical scanning holography

    Directory of Open Access Journals (Sweden)

    HU Zhijuan

    2015-08-01

    Full Text Available The lossy hologram compression method with three different interpolations is investigated to compress images holographically recorded with optical scanning holography.Without loss of major reconstruction details,results have shown that the lossy compression method is able to achieve high compression ratio of up to 100.

  4. Combining optical tweezers and scanning probe microscopy to study DNA-protein interactions

    NARCIS (Netherlands)

    Huisstede, Jurgen H.G.; Subramaniam, Vinod; Bennink, Martin L.

    2007-01-01

    We present the first results obtained with a new instrument designed and built to study DNA-protein interactions at the single molecule level. This microscope combines optical tweezers with scanning probe microscopy and allows us to locate DNA-binding proteins on a single suspended DNA molecule. A s

  5. Implant planning and placement using optical scanning and cone beam CT technology

    NARCIS (Netherlands)

    J.M. van der Zel

    2008-01-01

    There is a growing interest in minimally invasive implant therapy as a standard prosthodontic treatment, providing complete restoration of occlusal function. A new treatment method (CADDIMA), which combines both computerized tomographic (CT) and optical laser-scan data for planning and design of sur

  6. Kilohertz scanning all-fiber optical delay line using piezoelectric actuation

    Science.gov (United States)

    Henderson, David A.; Hoffman, Conrad; Culhane, Robert; Viggiano, Dan, III

    2004-12-01

    Commercial applications for fiber sensing and low-coherence interferometry are rapidly growing in medical, industrial and aerospace markets. These new instruments must be smaller, more robust and less expensive. An all-fiber optical delay line or "fiber stretcher", using piezoelectric (PZT) actuation, offers a simple solid-state solution that eliminates free space optics. The challenges for PZT fiber stretchers include: reducing non-linearity and hysteresis, achieving sufficient scan range with minimum fiber length, maximizing scan frequency and reducing losses in the drive electronics. PZT actuators are essentially large ceramic capacitors that must be rapidly charged and discharged to achieve fast scanning. The mechanical response of the PZT ceramic is greater than 10 kHz which makes it practical to scan at four kilohertz. A thin-walled piezoelectric disk or cylinder achieves 4.5 millimeters of fiber stretch using 20 meters of coiled fiber. Digitally controlled series resonant electronics produce a 1200 volt sinusoidal drive signal at a fixed frequency of four kilohertz while dissipating only 16 Watts. An all-fiber optical delay line module, using piezoelectric actuators and a series resonant drive, is a miniature, robust and efficient alternative to free-space optics with dithering mirrors or spinning polygons.

  7. Direct Measurement of Evanescent Wave Interference with a Scanning Near-field Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    HONG Tao; WANG Jia; XU Tie-Jun; SUN Li-Qun

    2004-01-01

    @@ Evanescent wave interference is studied theoretically and experimentally. The interference patterns were directly measured with a scanning near-field optical microscope. The acquired image of the interference pattern is clear and has better contrast than that previously acquired with a photon-scanning tunnelling microscope or lasertrapped particles. The spatial period of the interference fringes is 180nm, which agrees with the theoretical value.The results indicate that the probe of the scanning near-field optical microscope has a resolution beyond 100 nm.The relation between the evanescent field intensity and the distance is also measured. When the separation between the probe and the interface is up to 180nm, the intensity can decrease to 1/e of the maximum.

  8. Can previous thyroid scan induce cytogenetic radio adaptive response in patients treated by radioiodine for hyperthyroidism?

    International Nuclear Information System (INIS)

    Background: Induction of radio adaptive responses in cells pretreated with a low dose radiation before exposure to a high dose is well documented by many in investigators. The aim of this study is to determine the frequency of chromosomal aberration in peripheral blood lymphocytes of patients treated by radioiodine (131 I) for hyperthyroidism, with or without previous thyroid scan with 99m Tc. Materials and methods: venous blood samples were obtained from 35 patients one month after radioiodine therapy and cytogenetic ally evaluated using analysis of metaphase in two groups. The first group (n=15, 13 females and 2 males, mean age=44.7±11.5 years and mean weight 74.4±7.9 Kg) received 5 mCi 99m Tc for thyroid scanning 38.6±19.9 days before radioiodine therapy with 10.4±3.4 mCi 131I. The second group (n=20, 14 females and 6 males, mean age=41.0±10.8 years and mean weight=68.1±9.2 Kg) didn't have history of thyroid scanning. We also studied a control group (n=29, 11 females and 8 males age=33.7±7.4 and mean weight=70.0±8.8 Kg) who didn't have any history of diagnostic or therapeutic and also occupational exposure. Results: The mean frequency of total chromosomal aberrations in the first and second groups and controls were 1.46±1.55, 1.65±1.62 and 0.93±0.92 respectively. Results also showed that the mean frequency of total chromosome aberration in two groups were higher than controls and significantly higher in patients who had not received 99m Tc compared those who had undertaken thyroid scan before radioiodine therapy (p=0.03). Conclusion: These findings may indicate the fact that the radiation dose received from 99m Tc could induce resistance to subsequent higher radiation dose of 131 I in peripheral blood lymphocytes and it might be due to cytogenetic radio adaptive response

  9. Six-channel adaptive fibre-optic interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Romashko, R V; Bezruk, M N; Kamshilin, A A; Kulchin, Yurii N

    2012-06-30

    We have proposed and analysed a scheme for the multiplexing of orthogonal dynamic holograms in photorefractive crystals which ensures almost zero cross talk between the holographic channels upon phase demodulation. A six-channel adaptive fibre-optic interferometer was built, and the detection limit for small phase fluctuations in the channels of the interferometer was determined to be 2.1 Multiplication-Sign 10{sup -8} rad W{sup 1/2} Hz{sup -1/2}. The channel multiplexing capacity of the interferometer was estimated. The formation of 70 channels such that their optical fields completely overlap in the crystal reduces the relative detection limit in the working channel by just 10 %. We found conditions under which the maximum cross talk between the channels was within the intrinsic noise level in the channels (-47 dB).

  10. High Resolution Observations using Adaptive Optics: Achievements and Future Needs

    Indian Academy of Sciences (India)

    K. Sankarasubramanian; T. Rimmele

    2008-03-01

    Over the last few years, several interesting observations were obtained with the help of solar Adaptive Optics (AO). In this paper, few observations made using the solarAOare enlightened and briefly discussed. A list of disadvantages with the current AO system are presented. With telescopes larger than 1.5 m expected during the next decade, there is a need to develop the existing AO technologies for large aperture telescopes. Some aspects of this development are highlighted. Finally, the recent AO developments in India are also presented.

  11. Self-characterization of linear and nonlinear adaptive optics systems.

    Science.gov (United States)

    Hampton, Peter J; Conan, Rodolphe; Keskin, Onur; Bradley, Colin; Agathoklis, Pan

    2008-01-10

    We present methods used to determine the linear or nonlinear static response and the linear dynamic response of an adaptive optics (AO) system. This AO system consists of a nonlinear microelectromechanical systems deformable mirror (DM), a linear tip-tilt mirror (TTM), a control computer, and a Shack-Hartmann wavefront sensor. The system is modeled using a single-input-single-output structure to determine the one-dimensional transfer function of the dynamic response of the chain of system hardware. An AO system has been shown to be able to characterize its own response without additional instrumentation. Experimentally determined models are given for a TTM and a DM. PMID:18188192

  12. Light amplification by stimulated emission from an optically pumped molecular junction in a scanning tunneling microscope

    CERN Document Server

    Braun, K; Wang, X; Adler, H; Peisert, H; Chasse, T; Zhang, D; Meixner, A J

    2013-01-01

    Here, we introduce and experimentally demonstrate optical amplification and stimulated emission from a single optically pumped molecular tunneling junction of a scanning tunneling microscope. The gap between a sharp gold tip and a flat gold substrate covered with a self-assembled monolayer of 5-chloro-2-mercaptobenzothiazole molecules forms an extremely small optical gain medium. When electrons tunnel from the molecules highest occupied molecular orbital to the tip, holes are left behind. These can be repopulated by hot electrons induced by the laser-driven plasmon oscillation on the metal surfaces enclosing the cavity. Solving the laser-rate equations for this system shows that the repopulation process can be efficiently stimulated by the gap modes near field, TERS scattering from neighboring molecules acting as an optical seed. Our results demonstrate how optical enhancement inside the plasmonic cavity can be further increased by a stronger localization via tunneling through molecules. We anticipate that st...

  13. Accuracy of optical scanning methods of the Cerec®3D system in the process of making ceramic inlays

    Directory of Open Access Journals (Sweden)

    Trifković Branka

    2010-01-01

    Full Text Available Background/Aim. One of the results of many years of Cerec® 3D CAD/CAM system technological development is implementation of one intraoral and two extraoral optical scanning methods which, depending on the current indications, are applied in making fixed restorations. The aim of this study was to determine the degree of precision of optical scanning methods by the use of the Cerec®3D CAD/CAM system in the process of making ceramic inlays. Methods. The study was conducted in three experimental groups of inlays prepared using the procedure of three methods of scanning Cerec ®3D system. Ceramic inlays made by conventional methodology were the control group. The accuracy of optical scanning methods of the Cerec®3D system computer aided designcomputer aided manufacturing (CAD/CAM was indirectly examined by measuring a marginal gap size between inlays and demarcation preparation by scanning electron microscope (SEM. Results. The results of the study showed a difference in the accuracy of the existing methods of scanning dental CAD/CAM systems. The highest level of accuracy was achieved by the extraoral optical superficial scanning technique. The value of marginal gap size inlays made with the technique of extraoral optical superficial scanning was 32.97 ± 13.17 μ. Techniques of intraoral optical superficial and extraoral point laser scanning showed a lower level of accuracy (40.29 ± 21.46 μ for inlays of intraoral optical superficial scanning and 99.67 ± 37.25 μ for inlays of extraoral point laser scanning. Conclusion. Optical scanning methods in dental CAM/CAM technologies are precise methods of digitizing the spatial models; application of extraoral optical scanning methods provides the hightest precision.

  14. GPR Signal Processing with Geography Adaptive Scanning using Vector Radar for Antipersonal Landmine Detection

    Directory of Open Access Journals (Sweden)

    Shinsuke Sato

    2008-11-01

    Full Text Available Ground Penetrating Radar (GPR is a promising sensor for landmine detection, however there are two major problems to overcome. One is the rough ground surface. The other problem is the distance between the antennas of GPR. It remains irremovable clutters on a sub-surface image output from GPR by first problem. Geography adaptive scanning is useful to image objects beneath rough ground surface. Second problem makes larger the nonlinearity of the relationship between the time for propagation and the depth of a buried object, imaging the small objects such as an antipersonnel landmine closer to the antennas. In this paper, we modify Kirchhoff migration so as to account for not only the variation of position of the sensor head, but also the antennas alignment of the vector radar. The validity of this method is discussed through application to the signals acquired in experiments.

  15. Image restoration of the open-loop adaptive optics retinal imaging system based on optical transfer function analysis

    Science.gov (United States)

    Yu, Lei; Qi, Yue; Li, Dayu; Xia, Mingliang; Xuan, Li

    2013-07-01

    The residual aberrations of the adaptive optics retinal imaging system will decrease the quality of the retinal images. To overcome this obstacle, we found that the optical transfer function (OTF) of the adaptive optics retinal imaging system can be described as the Levy stable distribution. Then a new method is introduced to estimate the OTF of the open-loop adaptive optics system, based on analyzing the residual aberrations of the open-loop adaptive optics system in the residual aberrations measuring mode. At last, the estimated OTF is applied to restore the retinal images of the open-loop adaptive optics retinal imaging system. The contrast and resolution of the restored image is significantly improved with the Laplacian sum (LS) from 0.0785 to 0.1480 and gray mean grads (GMG) from 0.0165 to 0.0306.

  16. Handheld ultrahigh speed swept source optical coherence tomography instrument using a MEMS scanning mirror.

    Science.gov (United States)

    Lu, Chen D; Kraus, Martin F; Potsaid, Benjamin; Liu, Jonathan J; Choi, Woojhon; Jayaraman, Vijaysekhar; Cable, Alex E; Hornegger, Joachim; Duker, Jay S; Fujimoto, James G

    2013-12-20

    We developed an ultrahigh speed, handheld swept source optical coherence tomography (SS-OCT) ophthalmic instrument using a 2D MEMS mirror. A vertical cavity surface-emitting laser (VCSEL) operating at 1060 nm center wavelength yielded a 350 kHz axial scan rate and 10 µm axial resolution in tissue. The long coherence length of the VCSEL enabled a 3.08 mm imaging range with minimal sensitivity roll-off in tissue. Two different designs with identical optical components were tested to evaluate handheld OCT ergonomics. An iris camera aided in alignment of the OCT beam through the pupil and a manual fixation light selected the imaging region on the retina. Volumetric and high definition scans were obtained from 5 undilated normal subjects. Volumetric OCT data was acquired by scanning the 2.4 mm diameter 2D MEMS mirror sinusoidally in the fast direction and linearly in the orthogonal slow direction. A second volumetric sinusoidal scan was obtained in the orthogonal direction and the two volumes were processed with a software algorithm to generate a merged motion-corrected volume. Motion-corrected standard 6 x 6 mm(2) and wide field 10 x 10 mm(2) volumetric OCT data were generated using two volumetric scans, each obtained in 1.4 seconds. High definition 10 mm and 6 mm B-scans were obtained by averaging and registering 25 B-scans obtained over the same position in 0.57 seconds. One of the advantages of volumetric OCT data is the generation of en face OCT images with arbitrary cross sectional B-scans registered to fundus features. This technology should enable screening applications to identify early retinal disease, before irreversible vision impairment or loss occurs. Handheld OCT technology also promises to enable applications in a wide range of settings outside of the traditional ophthalmology or optometry clinics including pediatrics, intraoperative, primary care, developing countries, and military medicine. PMID:24466495

  17. Genome-Wide Scan for Adaptive Divergence and Association with Population-Specific Covariates.

    Science.gov (United States)

    Gautier, Mathieu

    2015-12-01

    In population genomics studies, accounting for the neutral covariance structure across population allele frequencies is critical to improve the robustness of genome-wide scan approaches. Elaborating on the BayEnv model, this study investigates several modeling extensions (i) to improve the estimation accuracy of the population covariance matrix and all the related measures, (ii) to identify significantly overly differentiated SNPs based on a calibration procedure of the XtX statistics, and (iii) to consider alternative covariate models for analyses of association with population-specific covariables. In particular, the auxiliary variable model allows one to deal with multiple testing issues and, providing the relative marker positions are available, to capture some linkage disequilibrium information. A comprehensive simulation study was carried out to evaluate the performances of these different models. Also, when compared in terms of power, robustness, and computational efficiency to five other state-of-the-art genome-scan methods (BayEnv2, BayScEnv, BayScan, flk, and lfmm), the proposed approaches proved highly effective. For illustration purposes, genotyping data on 18 French cattle breeds were analyzed, leading to the identification of 13 strong signatures of selection. Among these, four (surrounding the KITLG, KIT, EDN3, and ALB genes) contained SNPs strongly associated with the piebald coloration pattern while a fifth (surrounding PLAG1) could be associated to morphological differences across the populations. Finally, analysis of Pool-Seq data from 12 populations of Littorina saxatilis living in two different ecotypes illustrates how the proposed framework might help in addressing relevant ecological issues in nonmodel species. Overall, the proposed methods define a robust Bayesian framework to characterize adaptive genetic differentiation across populations. The BayPass program implementing the different models is available at http://www1.montpellier.inra.fr/CBGP/software/baypass/.

  18. Genome-Wide Scan for Adaptive Divergence and Association with Population-Specific Covariates.

    Science.gov (United States)

    Gautier, Mathieu

    2015-12-01

    In population genomics studies, accounting for the neutral covariance structure across population allele frequencies is critical to improve the robustness of genome-wide scan approaches. Elaborating on the BayEnv model, this study investigates several modeling extensions (i) to improve the estimation accuracy of the population covariance matrix and all the related measures, (ii) to identify significantly overly differentiated SNPs based on a calibration procedure of the XtX statistics, and (iii) to consider alternative covariate models for analyses of association with population-specific covariables. In particular, the auxiliary variable model allows one to deal with multiple testing issues and, providing the relative marker positions are available, to capture some linkage disequilibrium information. A comprehensive simulation study was carried out to evaluate the performances of these different models. Also, when compared in terms of power, robustness, and computational efficiency to five other state-of-the-art genome-scan methods (BayEnv2, BayScEnv, BayScan, flk, and lfmm), the proposed approaches proved highly effective. For illustration purposes, genotyping data on 18 French cattle breeds were analyzed, leading to the identification of 13 strong signatures of selection. Among these, four (surrounding the KITLG, KIT, EDN3, and ALB genes) contained SNPs strongly associated with the piebald coloration pattern while a fifth (surrounding PLAG1) could be associated to morphological differences across the populations. Finally, analysis of Pool-Seq data from 12 populations of Littorina saxatilis living in two different ecotypes illustrates how the proposed framework might help in addressing relevant ecological issues in nonmodel species. Overall, the proposed methods define a robust Bayesian framework to characterize adaptive genetic differentiation across populations. The BayPass program implementing the different models is available at http://www1.montpellier

  19. AVES: an adaptive optics visual echelle spectrograph for the VLT

    Science.gov (United States)

    Pasquini, Luca; Delabre, Bernard; Avila, Gerardo; Bonaccini, Domenico

    1998-07-01

    We present the preliminary study of a low cost, high performance spectrograph for the VLT, for observations in the V, R and I bands. This spectrograph is meant for intermediate (R equals 16,000) resolution spectroscopy of faint (sky and/or detector limited) sources, with particular emphasis on the study of solar-type (F-G) stars belonging to the nearest galaxies and to distant (or highly reddened) galactic clusters. The spectrograph is designed to use the adaptive optics (AO) systems at the VLT Telescope. Even if these AO systems will not provide diffraction limited images in the V, R and I bands, the photon concentration will still be above approximately 60% of the flux in an 0.3 arcsecond aperture for typical Paranal conditions. This makes the construction of a compact, cheap and efficient echelle spectrograph possible. AVES will outperform comparable non adaptive optic instruments by more than one magnitude for sky- and/or detector-limited observations, and it will be very suitable for observations in crowded fields.

  20. Adaptive Optics and Lucky Imager (AOLI): presentation and first light

    CERN Document Server

    Velasco, S; Mackay, C; Oscoz, A; King, D L; Crass, J; Díaz-Sánchez, A; Femenía, B; González-Escalera, V; Labadie, L; López, R L; Garrido, A Pérez; Puga, M; Rodríguez-Ramos, L F; Zuther, J

    2015-01-01

    In this paper we present the Adaptive Optics Lucky Imager (AOLI), a state-of-the-art instrument which makes use of two well proved techniques for extremely high spatial resolution with ground-based telescopes: Lucky Imaging (LI) and Adaptive Optics (AO). AOLI comprises an AO system, including a low order non-linear curvature wavefront sensor together with a 241 actuators deformable mirror, a science array of four 1024x1024 EMCCDs, allowing a 120x120 down to 36x36 arcseconds field of view, a calibration subsystem and a powerful LI software. Thanks to the revolutionary WFS, AOLI shall have the capability of using faint reference stars ({\\it I\\/} $\\sim$ 16.5-17.5), enabling it to be used over a much wider part of the sky than with common Shack-Hartmann AO systems. This instrument saw first light in September 2013 at William Herschel Telescope. Although the instrument was not complete, these commissioning demonstrated its feasibility, obtaining a FWHM for the best PSF of 0.151$\\pm$0.005 arcsec and a plate scale o...

  1. Adaptive optics sky coverage modeling for extremely large telescopes.

    Science.gov (United States)

    Clare, Richard M; Ellerbroek, Brent L; Herriot, Glen; Véran, Jean-Pierre

    2006-12-10

    A Monte Carlo sky coverage model for laser guide star adaptive optics systems was proposed by Clare and Ellerbroek [J. Opt. Soc. Am. A 23, 418 (2006)]. We refine the model to include (i) natural guide star (NGS) statistics using published star count models, (ii) noise on the NGS measurements, (iii) the effect of telescope wind shake, (iv) a model for how the Strehl and hence NGS wavefront sensor measurement noise varies across the field, (v) the focus error due to imperfectly tracking the range to the sodium layer, (vi) the mechanical bandwidths of the tip-tilt (TT) stage and deformable mirror actuators, and (vii) temporal filtering of the NGS measurements to balance errors due to noise and servo lag. From this model, we are able to generate a TT error budget for the Thirty Meter Telescope facility narrow-field infrared adaptive optics system (NFIRAOS) and perform several design trade studies. With the current NFIRAOS design, the median TT error at the galactic pole with median seeing is calculated to be 65 nm or 1.8 mas rms.

  2. Non-iterative adaptive optical microscopy using wavefront sensing

    Science.gov (United States)

    Tao, X.; Azucena, O.; Kubby, J.

    2016-03-01

    This paper will review the development of wide-field and confocal microscopes with wavefront sensing and adaptive optics for correcting refractive aberrations and compensating scattering when imaging through thick tissues (Drosophila embryos and mouse brain tissue). To make wavefront measurements in biological specimens we have modified the laser guide-star techniques used in astronomy for measuring wavefront aberrations that occur as star light passes through Earth's turbulent atmosphere. Here sodium atoms in Earth's mesosphere, at an altitude of 95 km, are excited to fluoresce at resonance by a high-power sodium laser. The fluorescent light creates a guide-star reference beacon at the top of the atmosphere that can be used for measuring wavefront aberrations that occur as the light passes through the atmosphere. We have developed a related approach for making wavefront measurements in biological specimens using cellular structures labeled with fluorescent proteins as laser guide-stars. An example is a fluorescently labeled centrosome in a fruit fly embryo or neurons and dendrites in mouse brains. Using adaptive optical microscopy we show that the Strehl ratio, the ratio of the peak intensity of an aberrated point source relative to the diffraction limited image, can be improved by an order of magnitude when imaging deeply into live dynamic specimens, enabling near diffraction limited deep tissue imaging.

  3. Adaptive Optics Imaging Survey of Luminous Infrared Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Laag, E A; Canalizo, G; van Breugel, W; Gates, E L; de Vries, W; Stanford, S A

    2006-03-13

    We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L{sub FIR} {ge} 10{sup 12} L{sub {circle_dot}}) and 19 new LIGs (with L{sub FIR} {ge} 10{sup 11} L{sub {circle_dot}}). Twenty of the galaxies in the sample were imaged with either the Lick or Keck adaptive optics systems in H or K{prime}. Galaxy morphologies were determined using the two dimensional fitting program GALFIT and the residuals examined to look for interesting structure. The morphologies reveal that at least 30% are involved in tidal interactions, with 20% being clear mergers. An additional 50% show signs of possible interaction. Line ratios were used to determine powering mechanism; of the 17 objects in the sample showing clear emission lines--four are active galactic nuclei and seven are starburst galaxies. The rest exhibit a combination of both phenomena.

  4. CRAO: a compact and refractive adaptive-optics

    Science.gov (United States)

    Fujishiro, Naofumi; Kitao, Eiji; Shimizu, Tomo; Matsui, Takuya; Ikeda, Yuji; Kawakita, Hideyo; Oya, Shin

    2014-08-01

    CRAO is a demonstrator of a compact and low-cost adaptive-optics (AO) with a double-pass lens configuration. Owing to its compact optical layout compared to conventional reflective AOs, the instrument size can be reduced to only 0.03 square meters. We plan to apply this miniaturization technique into future AOs on a variety of telescopes ranging from 1m- to 30m-class. CRAO is installed at a Nasmyth focus of the 1.3m Araki telescope at Koyama Astronomical Observatory in Kyoto Sangyo University. CRAO adopts a closed-loop single-conjugate system with wavelength coverage of 400 - 700 nm and the field of view of 30 arcsec. For low cost, we also employ commercial products on its wavefront sensor (WFS), deformable mirror (DM), and tip-tilt (TT) stage. CRAO is designed to improve the atmospheric seeing from 2.5 to 0.6arcsec under a typical condition at Koyama Astronomical Observatory with 12x12 subapertures in the WFS, 48 electrodes in the membrane DM and the control bandwidth of 200Hz. In order to examine key issues inherent in refractive optical system such as chromatic aberration, temperature aberration and ghost images, room and on-sky experiments are currently underway. CRAO has seen first light in May 2014, and we have confirmed that effects of chromatic aberration and ghost images induced by its refractive optics are negligible for at least TT correction. In this paper, we present experimental results as well as the design of optics, opto-mechanics and control system.

  5. Scanning a DNA molecule for bound proteins using hybrid magnetic and optical tweezers.

    Directory of Open Access Journals (Sweden)

    Marijn T J van Loenhout

    Full Text Available The functional state of the genome is determined by its interactions with proteins that bind, modify, and move along the DNA. To determine the positions and binding strength of proteins localized on DNA we have developed a combined magnetic and optical tweezers apparatus that allows for both sensitive and label-free detection. A DNA loop, that acts as a scanning probe, is created by looping an optically trapped DNA tether around a DNA molecule that is held with magnetic tweezers. Upon scanning the loop along the λ-DNA molecule, EcoRI proteins were detected with ~17 nm spatial resolution. An offset of 33 ± 5 nm for the detected protein positions was found between back and forwards scans, corresponding to the size of the DNA loop and in agreement with theoretical estimates. At higher applied stretching forces, the scanning loop was able to remove bound proteins from the DNA, showing that the method is in principle also capable of measuring the binding strength of proteins to DNA with a force resolution of 0.1 pN/[Formula: see text]. The use of magnetic tweezers in this assay allows the facile preparation of many single-molecule tethers, which can be scanned one after the other, while it also allows for direct control of the supercoiling state of the DNA molecule, making it uniquely suitable to address the effects of torque on protein-DNA interactions.

  6. Adaptive distributed Kalman filtering with wind estimation for astronomical adaptive optics.

    Science.gov (United States)

    Massioni, Paolo; Gilles, Luc; Ellerbroek, Brent

    2015-12-01

    In the framework of adaptive optics (AO) for astronomy, it is a common assumption to consider the atmospheric turbulent layers as "frozen flows" sliding according to the wind velocity profile. For this reason, having knowledge of such a velocity profile is beneficial in terms of AO control system performance. In this paper we show that it is possible to exploit the phase estimate from a Kalman filter running on an AO system in order to estimate wind velocity. This allows the update of the Kalman filter itself with such knowledge, making it adaptive. We have implemented such an adaptive controller based on the distributed version of the Kalman filter, for a realistic simulation of a multi-conjugate AO system with laser guide stars on a 30 m telescope. Simulation results show that this approach is effective and promising and the additional computational cost with respect to the distributed filter is negligible. Comparisons with a previously published slope detection and ranging wind profiler are made and the impact of turbulence profile quantization is assessed. One of the main findings of the paper is that all flavors of the adaptive distributed Kalman filter are impacted more significantly by turbulence profile quantization than the static minimum mean square estimator which does not incorporate wind profile information.

  7. Adaptive distributed Kalman filtering with wind estimation for astronomical adaptive optics.

    Science.gov (United States)

    Massioni, Paolo; Gilles, Luc; Ellerbroek, Brent

    2015-12-01

    In the framework of adaptive optics (AO) for astronomy, it is a common assumption to consider the atmospheric turbulent layers as "frozen flows" sliding according to the wind velocity profile. For this reason, having knowledge of such a velocity profile is beneficial in terms of AO control system performance. In this paper we show that it is possible to exploit the phase estimate from a Kalman filter running on an AO system in order to estimate wind velocity. This allows the update of the Kalman filter itself with such knowledge, making it adaptive. We have implemented such an adaptive controller based on the distributed version of the Kalman filter, for a realistic simulation of a multi-conjugate AO system with laser guide stars on a 30 m telescope. Simulation results show that this approach is effective and promising and the additional computational cost with respect to the distributed filter is negligible. Comparisons with a previously published slope detection and ranging wind profiler are made and the impact of turbulence profile quantization is assessed. One of the main findings of the paper is that all flavors of the adaptive distributed Kalman filter are impacted more significantly by turbulence profile quantization than the static minimum mean square estimator which does not incorporate wind profile information. PMID:26831389

  8. Optical encryption of unlimited-size images based on ptychographic scanning digital holography.

    Science.gov (United States)

    Gao, Qiankun; Wang, Yali; Li, Tuo; Shi, Yishi

    2014-07-20

    The ptychographic scanning operation is introduced into digital holography to expand the field-of-view (FOV). An optical image encryption method based on this technique is further proposed and analyzed. The plaintext is moved sequentially in the way of ptychographic scanning and corresponding pairs of phase-shifted interferograms are recorded as ciphertexts. Then the holographic processing and the ptychographic iterative reconstruction are both employed to retrieve the plaintext. Numerical experiments demonstrate that the proposed system possesses high security level and wide FOV. The proposed method might also be used for other potential applications, such as three-dimensional information encryption and image hiding.

  9. Nonlinear optical properties of zinc oxide doped bismuth thin films using Z-scan technique

    Science.gov (United States)

    Abed, S.; Bouchouit, K.; Aida, M. S.; Taboukhat, S.; Sofiani, Z.; Kulyk, B.; Figa, V.

    2016-06-01

    ZnO doped Bi thin films were grown on glass substrates by spray ultrasonic technique. This paper presents the effect of Bi doping concentration on structural and nonlinear optical properties of zinc oxide thin films. These thin films were characterized by X-ray diffractometer technique. XRD analysis revealed that the ZnO:Bi thin films indicated good preferential orientation along c-axis perpendicular to the substrate. The nonlinear optical properties such as nonlinear absorption coefficient (β) and third order nonlinear susceptibility (Imχ(3)) are investigated. The calculations have been performed with a Z scan technique using Nd:YAG laser emitting 532 nm. The reverse saturable absorption (RSA) mechanism was responsible for the optical limiting effect. The results suggest that this material considered as a promising candidate for future optical device applications.

  10. Bow-tie optical antenna probes for single-emitter scanning near-field optical microscopy

    OpenAIRE

    Farahani, Javad N.; Eisler, Hans-Jürgen; Pohl, Dieter W; Pavius, Michaël; Flückiger, Philippe; Gasser, Philippe; Hecht, Bert

    2007-01-01

    A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si3N4 atomic force microscopy tips is described. We demonstrate that these novel optical probes are capable of sub-wavelength imaging of single quantum dots at room temperature. The enhanced and confined optical near-field at the antenna feed gap leads to locally enhanced photoluminescence (PL) of single quantum dots. Photoluminescence quenching due to the proximity of metal is found to be insignificant. The met...

  11. Low Temperature Apertureless Near-field Scanning Optical Microscope for Optical Spectroscopy of Single Ge/Si Quantum Dots

    Science.gov (United States)

    Zhu, Henry; Patil, N. G.; Levy, Jeremy

    2001-03-01

    A low-temperature apertureless near-field scanning optical microscope has been designed and constructed for the purpose of investigating the optical properties of individual Ge/Si quantum dots. The microscope fits in the 37 mm bore of a Helium vapor magneto-optic cryostat, allowing operations down to liquid helium temperatures in magnetic fields up to 8 Tesla. An in situ microscope objective focuses light onto the sample, which is scanned in the three spatial directions using a compact modular stage. An AFM/STM tip resides on the top; feedback is achieved using a quartz tuning fork oscillator. Both tip and objective are attached to inertial sliding motors that can move in fine (10 nm) steps to achieve touchdown and focus. A femtosecond optical parametric oscillator is used to excite carriers in the quantum dots both resonantly and non-resonantly; scattered luminescence from the AFM/STM tip is collected and analyzed spectrally using a 1/2 meter imaging spectrometer and a LN_2-cooled InGaAs array. We gratefully acknowledge NSF (DMR-9701725, IMR-9802784) and DARPA (DAAD-16-99-C1036) for financial support of this work.

  12. Synthetic aperture laser optical feedback imaging using a translational scanning with galvanometric mirrors

    CERN Document Server

    Glastre, Wilfried; Hugon, Olivier; De Chatellus, Hugues Guillet; Lacot, Eric

    2012-01-01

    In this paper we present an experimental setup based on Laser Optical Feedback Imaging (LOFI) and on Synthetic Aperture (SA) with translational scanning by galvanometric mirrors for the purpose of making deep and resolved images through scattering media. We provide real 2D optical synthetic-aperture image of a fixed scattering target with a moving aperture and an isotropic resolution. We demonstrate theoretically and experimentally that we can keep microscope resolution beyond the working distance. A photometric balance is made and we show that the number of photons participating in the final image decreases with the square of the reconstruction distance. This degradation is partially compensated by the high sensitivity of LOFI.

  13. Z-scan and optical limiting properties of Hibiscus Sabdariffa dye

    Science.gov (United States)

    Diallo, A.; Zongo, S.; Mthunzi, P.; Rehman, S.; Alqaradawi, S. Y.; Soboyejo, W.; Maaza, M.

    2014-12-01

    The intensity-dependent refractive index n 2 and the nonlinear susceptibility χ (3) of Hibiscus Sabdariffa dye solutions in the nanosecond regime at 532 nm are reported. More presicely, the variation of n 2, β, and real and imaginary parts of χ (3) versus the natural dye extract concentration has been carried out by z-scan and optical limiting techniques. The third-order nonlinearity of the Hibiscus Sabdariffa dye solutions was found to be dominated by nonlinear refraction, which leads to strong optical limiting of laser.

  14. Scanning probe microscopy of thermally excited mechanical modes of an optical microcavity

    CERN Document Server

    Kippenberg, T J; Vahala, K J

    2006-01-01

    The resonant buildup of light within optical microcavities elevates the radiation pressure which mediates coupling of optical modes to the mechanical modes of a microcavity. Above a certain threshold pump power, regenerative mechanical oscillation occurs causing oscillation of certain mechanical eigenmodes. Here, we present a methodology to spatially image the micro-mechanical resonances of a toroid microcavity using a scanning probe technique. The method relies on recording the induced frequency shift of the mechanical eigenmode when in contact with a scanning probe tip. The method is passive in nature and achieves a sensitivity sufficient to spatially resolve the vibrational mode pattern associated with the thermally agitated displacement at room temperature. The recorded mechanical mode patterns are in good qualitative agreement with the theoretical strain fields as obtained by finite element simulations.

  15. Mono-Cycle Photonics and Optical Scanning Tunneling Microscopy Route to Femtosecond Ångstrom Technology

    CERN Document Server

    Yamashita, Mikio; Morita, Ryuji

    2005-01-01

    "Mono-Cycle Photonics and Optical Scanning Tunneling Microscopy" deals with both the ultrashort laser-pulse technology in the few- to mono-cycle region and the laser-surface-controlled scanning-tunneling microscopy (STM) extending into the spatiotemporal extreme technology. The former covers the theory of nonlinear pulse propagation beyond the slowly-varing-envelope approximation, the generation and active chirp compensation of ultrabroadband optical pulses, the amplitude and phase characterization of few- to mono-cycle pulses, and the feedback field control for the mono-cycle-like pulse generation. In addition, the wavelength-multiplex shaping of ultrabroadband pulse is described. The latter covers the CW-laser-excitation STM, the femtosecond-time-resolved STM and atomic-level surface phenomena controlled by femtosecond pulses.

  16. The adaptation of methods in multilayer optics for the calculation of specular neutron reflection

    International Nuclear Information System (INIS)

    The adaptation of standard methods in multilayer optics to the calculation of specular neutron reflection is described. Their application is illustrated with examples which include a glass optical flat and a deuterated Langmuir-Blodgett film. (author)

  17. Scanning fiber-optic nonlinear endomicroscopy with miniature aspherical compound lens and multimode fiber collector

    OpenAIRE

    Wu, Yicong; Xi, Jiefeng; Cobb, Michael J.; Li, Xingde

    2009-01-01

    A flexible scanning fiber-optic endomicroscope using a miniature compound lens and a multimode-fiber (MMF) collector was developed for two-photon fluorescence (TPF) and second-harmonic generation (SHG) imaging. The compound lens consisted of a pair of aspherical lenses and exhibited reduced chromatic aberration compared with gradient-index lenses, thus increasing the TPF/SHG collection efficiency. The introduction of a short MMF collector at the distal end of the double-clad fiber of the endo...

  18. Design and development of an optical scanning mechanism (OSMA) with minimum momentum transfer

    Science.gov (United States)

    Sainz, L. B. F.; Herrera, E.; Bajo, J. M.; Mallard, H. J.

    1981-01-01

    The development model for an optical scanning mechanism assembly is described as being two equal inertial masses which collide with each other to minimize the momentum transfer to the satellite and other mounted instruments. The design criteria for the mirror, the compensating inertia structure and other components are given. The details of the design are discussed and related test results are presented, which show the validity of the design concept for momentum compensation.

  19. Flexydos3D: A new deformable anthropomorphic 3D dosimeter readout with optical CT scanning

    Science.gov (United States)

    De Deene, Yves; Hill, Robin; Skyt, Peter S.; Booth, Jeremy

    2015-01-01

    A new deformable polydimethylsiloxane (PDMS) based dosimeter is proposed that can be cast in an anthropomorphic shape and that can be used for 3D radiation dosimetry of deformable targets. The new material has additional favorable characteristics as it is tissue equivalent for high-energy photons, easy to make and is non-toxic. In combination with dual wavelength optical scanning, it is a powerful dosimeter for dose verification of image gated or organ tracked radiotherapy with moving and deforming targets.

  20. Resolution of Internal Total Reflection Scanning Near-field Optical Microscopy

    Institute of Scientific and Technical Information of China (English)

    GE Huayong; GUO Qizhi; TAN Weihan

    2002-01-01

    In this paper, the probe-sample interaction equation based on Mie′s scattering theory is derived, and the resolution of scanning near field optical microscopy is calculated numerically. The results show that the offset of far-field component to near-field component in total field plays an important role in the resolution and the size of samples also has influence on resolution.

  1. Development of scanning laser sensor for underwater 3D imaging with the coaxial optics

    Science.gov (United States)

    Ochimizu, Hideaki; Imaki, Masaharu; Kameyama, Shumpei; Saito, Takashi; Ishibashi, Shoujirou; Yoshida, Hiroshi

    2014-06-01

    We have developed the scanning laser sensor for underwater 3-D imaging which has the wide scanning angle of 120º (Horizontal) x 30º (Vertical) with the compact size of 25 cm diameter and 60 cm long. Our system has a dome lens and a coaxial optics to realize both the wide scanning angle and the compactness. The system also has the feature in the sensitivity time control (STC) circuit, in which the receiving gain is increased according to the time of flight. The STC circuit contributes to detect a small signal by suppressing the unwanted signals backscattered by marine snows. We demonstrated the system performance in the pool, and confirmed the 3-D imaging with the distance of 20 m. Furthermore, the system was mounted on the autonomous underwater vehicle (AUV), and demonstrated the seafloor mapping at the depth of 100 m in the ocean.

  2. Laser-induced cantilever behaviour in apertureless scanning near-field optical microscopes

    International Nuclear Information System (INIS)

    The laser-induced deformation of a typical commercial cantilever commonly used for scanning near-field optical microscopes was investigated by means of a software package based on the finite element method. The thermo-mechanical behaviour of such a cantilever whose tip was irradiated by a laser beam was calculated in the temperature regime between room temperature and 850 K. The spatial tip displacement was simulated at timescales <0.1 ms, since feedback-based constant force measurements exhibit reaction times in this range. It could be shown that in addition to former tip-based thermal expansion calculations the cantilever deformation is already significant at moderate temperatures, particularly when a reflective coating is present. The experimental and calculated results suggest that tip scanning in cantilever-based scanning probe microscopes for laser-based surface modification applications should be performed in thermal equilibrium. (paper)

  3. Full-color optical scanning holography with common red, green, and blue channels [Invited].

    Science.gov (United States)

    Kim, Hayan; Kim, You Seok; Kim, Taegeun

    2016-01-20

    We propose color optical scanning holography (OSH) that records red, green, and blue (RGB) holograms of real objects by single scanning. The proposed color OSH composes a RGB multiplexing unit, color time-dependent Fresnel zone plate generation unit, scanning unit, space-integrating photodetection unit, and demultiplexing unit. In the proposed color OSH, RGB beams follow a common path from the multiplexing unit to a photodetector, generating an electric current containing the object's complex RGB hologram information. In the demultiplexing unit, the complex RGB holograms are extracted and arranged as a complex color hologram. In experiments, we record the complex color hologram of a three-dimensional object composed of RGB transparencies using the color OSH. Numerical reconstruction shows that the recorded hologram contains information about the object's color as well as the diffracted field from the object. PMID:26835951

  4. Compact MEMS-based Adaptive Optics Optical Coherence Tomography for Clinical Use

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D; Olivier, S; Jones, S; Zawadzki, R; Evans, J; Choi, S; Werner, J

    2008-02-04

    We describe a compact MEMS-based adaptive optics (AO) optical coherence tomography system with improved AO performance and ease of clinical use. A typical AO system consists of a Shack-Hartmann wavefront sensor and a deformable mirror that measures and corrects the ocular and system aberrations. Because of the limitation on the current deformable mirror technologies, the amount of real-time ocular-aberration compensation is restricted and small in the previous AO-OCT instruments. In this instrument, we proposed to add an optical apparatus to correct the spectacle aberrations of the patients such as myopia, hyperopia and astigmatism. This eliminated the tedious process of the trial lenses in clinical imaging. Different amount of spectacle aberration compensation was achieved by motorized stages and automated with the AO computer for ease of clinical use. In addition, the compact AO-OCT was optimized to have minimum system aberrations to reduce AO registration errors and improve AO performance.

  5. `imaka - a ground-layer adaptive optics system on Maunakea

    CERN Document Server

    Chun, Mark; Toomey, Douglas; Lu, Jessica; Service, Max; Baranec, Christoph; Thibault, Simon; Brousseau, Denis; Hayano, Yutaka; Oya, Shin; Santi, Shane; Kingery, Christopher; Loss, Keith; Gardiner, John; Steele, Brad

    2016-01-01

    We present the integration status for `imaka, the ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. This wide-field GLAO pathfinder system exploits Maunakea's highly confined ground layer and weak free-atmosphere to push the corrected field of view to ~1/3 of a degree, an areal field approaching an order of magnitude larger than any existing or planned GLAO system, with a FWHM ~ 0.33 arcseconds in the visible and near infrared. We discuss the unique design aspects of the instrument, the driving science cases and how they impact the system, and how we will demonstrate these cases on the sky.

  6. Synthetic Modeling of Astronomical Closed Loop Adaptive Optics

    CERN Document Server

    Jolissaint, Laurent

    2010-01-01

    We present an analytical model of a single natural guide star astronomical adaptive optics system, in closed loop mode. The model is used to simulate the long exposure system point spread function, using the spatial frequency (or Fourier) approach, and complement an initial open loop model. Applications range from system design, science case analysis and AO data reduction. All the classical phase errors have been included: deformable mirror fitting error, wavefront sensor spatial aliasing, wavefront sensor noise, and the correlated anisoplanatic and servo-lag error. The model includes the deformable mirror spatial transfer function, and the actuator array geometry can be different from the wavefront sensor lenslet array geometry. We also include the dispersion between the sensing and the correction wavelengths. Illustrative examples are given at the end of the paper.

  7. MICADO: the E-ELT Adaptive Optics Imaging Camera

    CERN Document Server

    Davies, R

    2010-01-01

    MICADO is the adaptive optics imaging camera for the E-ELT. It has been designed and optimised to be mounted to the LGS-MCAO system MAORY, and will provide diffraction limited imaging over a wide (about 1 arcmin) field of view. For initial operations, it can also be used with its own simpler AO module that provides on-axis diffraction limited performance using natural guide stars. We discuss the instrument's key capabilities and expected performance, and show how the science drivers have shaped its design. We outline the technical concept, from the opto-mechanical design to operations and data processing. We describe the AO module, summarise the instrument performance, and indicate some possible future developments.

  8. Multiple Object Adaptive Optics: Mixed NGS/LGS tomography

    Science.gov (United States)

    Morris, Tim; Gendron, Eric; Basden, Alastair; Martin, Olivier; Osborn, James; Henry, David; Hubert, Zoltan; Sivo, Gaetano; Gratadour, Damien; Chemla, Fanny; Sevin, Arnaud; Cohen, Matthieu; Younger, Eddy; Vidal, Fabrice; Wilson, Richard; Batterley, Tim; Bitenc, Urban; Reeves, Andrew; Bharmal, Nazim; Raynaud, Henri-François; Kulcsar, Caroline; Conan, Jean-Marc; Guzman, Dani; De Cos Juez, Javier; Huet, Jean-Michel; Perret, Denis; Dickson, Colin; Atkinson, David; Baillie, Tom; Longmore, Andy; Todd, Stephen; Talbot, Gordon; Morris, Simon; Myers, Richard; Rousset, Gérard

    2013-12-01

    Open-loop adaptive optics has been successfully demonstrated on-sky by several groups, including the fully tomographic MOAO demonstration made using CANARY. MOAO instrumentation such as RAVEN will deliver the first astronomical science and other planned instruments aim to extend both open-loop AO performance and the number of corrected fields. Many of these planned systems rely on the use of tomographic open-loop LGS wavefront sensing. Here we present results from the combined NGS/LGS tomographic CANARY system and then compare the NGS- and LGS-based tomographic system performance. We identify the major system performance drivers, and highlight some potential routes for further exploitation of open-loop tomographic AO.

  9. Kalman filtering to suppress spurious signals in Adaptive Optics control

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  10. High-redshift quasar host galaxies with adaptive optics

    CERN Document Server

    Kuhlbrodt, B; Wisotzki, L; Jahnke, K

    2005-01-01

    We present K band adaptive optics observations of three high-redshift (z ~ 2.2) high-luminosity quasars, all of which were studied for the first time. We also bserved several point spread function (PSF) calibrators, non-simultaneously because of the small field of view. The significant temporal PSF variations on timescales of minutes inhibited a straightforward scaled PSF removal from the quasar images. Characterising the degree of PSF concentration by the radii encircling 20% and 80% of the total flux, respectively, we found that even under very different observing conditions the r20 vs. r80 relation varied coherently between individual short exposure images, delineating a well-defined relation for point sources. Placing the quasar images on this relation, we see indications that all three objects were resolved. We designed a procedure to estimate the significance of this result, and to estimate host galaxy parameters, by reproducing the statistical distribution of the individual short exposure images. We fi...

  11. Enhancing stellar spectroscopy with extreme adaptive optics and photonics

    CERN Document Server

    Jovanovic, Nemanja; Cvetojevic, Nick; Guyon, Olivier; Martinache, Frantz

    2016-01-01

    Extreme adaptive optics systems are now in operation across the globe. These systems, capable of high order wavefront correction, deliver Strehl ratios of 90% in the near-infrared. Originally intended for the direct imaging of exoplanets, these systems are often equipped with advanced coronagraphs that suppress the on-axis-star, interferometers to calibrate wavefront errors, and low order wavefront sensors to stabilize any tip/tilt residuals to a degree never seen before. Such systems are well positioned to facilitate the detailed spectroscopic characterization of faint substellar companions at small angular separations from the host star. Additionally, the increased light concentration of the point-spread function and the unprecedented stability create opportunities in other fields of astronomy as well, including spectroscopy. With such Strehl ratios, efficient injection into single-mode fibers or photonic lanterns becomes possible. With diffraction-limited components feeding the instrument, calibrating a sp...

  12. Performance of the Keck Observatory adaptive optics system

    Energy Technology Data Exchange (ETDEWEB)

    van Dam, M A; Mignant, D L; Macintosh, B A

    2004-01-19

    In this paper, the adaptive optics (AO) system at the W.M. Keck Observatory is characterized. The authors calculate the error budget of the Keck AO system operating in natural guide star mode with a near infrared imaging camera. By modeling the control loops and recording residual centroids, the measurement noise and band-width errors are obtained. The error budget is consistent with the images obtained. Results of sky performance tests are presented: the AO system is shown to deliver images with average Strehl ratios of up to 0.37 at 1.58 {micro}m using a bright guide star and 0.19 for a magnitude 12 star.

  13. Adaptive fiber optics collimator based on flexible hinges.

    Science.gov (United States)

    Zhi, Dong; Ma, Yanxing; Ma, Pengfei; Si, Lei; Wang, Xiaolin; Zhou, Pu

    2014-08-20

    In this manuscript, we present a new design for an adaptive fiber optics collimator (AFOC) based on flexible hinges by using piezoelectric stacks actuators for X-Y displacement. Different from traditional AFOC, the new structure is based on flexible hinges to drive the fiber end cap instead of naked fiber. We fabricated a real AFOC based on flexible hinges, and the end cap's deviation and resonance frequency of the device were measured. Experimental results show that this new AFOC can provide fast control of tip-tilt deviation of the laser beam emitting from the end cap. As a result, the fiber end cap can support much higher power than naked fiber, which makes the new structure ideal for tip-tilt controlling in a high-power fiber laser system.

  14. Adaptive Optics Observations of Exoplanets, Brown Dwarfs, & Binary Stars

    CERN Document Server

    Hinkley, Sasha

    2011-01-01

    The current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Fu...

  15. Adaptive optics imaging of low and intermediate redshift quasars

    CERN Document Server

    Márquez, I; Theodore, B; Bremer, M; Monnet, G; Beuzit, J L

    2001-01-01

    We present the results of adaptive-optics imaging in the H and K bands of 12 low and intermediate redshift (z15.0) themselves as reference for the correction, have typical spatial resolution of FWHM~0.3 arcsec before deconvolution. The deconvolved H-band image of PG1700+514 has a spatial resolution of 0.16 arcsec and reveals a wealth of details on the companion and the host-galaxy. Four out of the twelve quasars have close companions and obvious signs of interactions. The two-dimensional images of three of the host-galaxies unambiguously reveal bars and spiral arms. The morphology of the other objects are difficult to determine from one dimensional surface brightness profile and deeper images are needed. Analysis of mocked data shows that elliptical galaxies are always recognized as such, whereas disk hosts can be missed for small disk scale lengths and large QSO contributions.

  16. 4th International Workshop on Adaptive Optics for Industry and Medicine

    CERN Document Server

    Wittrock, Ulrich

    2005-01-01

    This book treats the development and application of adaptive optics for industry and medicine. The contributions describe recently developed components for adaptive-optics systems such as deformable mirrors, wavefront sensors, and mirror drivers as well as complete adaptive optical systems and their applications in industry and medicine. Applications range from laser-beam forming and adaptive aberration correction for high-power lasers to retinal imaging in ophthalmology. The contributions are based on presentations made at the 4th International Workshop on Adaptive Optics in Industry and Medicine which took place in Münster, Germany, in October 2003. This highly successful series of workshops on adaptive optics started in 1997 and continues with the 5th workshop in Beijing in 2005.

  17. Efficacy of visual-scanning training and prism adaptation for neglect rehabilitation.

    Science.gov (United States)

    Spaccavento, Simona; Cellamare, Fara; Cafforio, Elisabetta; Loverre, Anna; Craca, Angela

    2016-01-01

    Unilateral spatial neglect consists of the inability of a patient to respond, orient, and attend to stimuli on the left side of a space following a right-hemisphere lesion. Many rehabilitation approaches have been proposed to reduce neglect. The aim of our study was to compare the effect of visual-scanning training (VST) and prismatic adaptation (PA) on patients with neglect following a right-hemisphere lesion. Twenty patients with left neglect were enrolled in the study. Before and after training, a comprehensive neuropsychological assessment of visuospatial abilities, evaluating personal, peripersonal, and extrapersonal neglect, was performed. After assessment, patients were alternately assigned to 1 of 2 groups, VST or PA. Both trainings consisted of 20 sessions, 1 per day, 5 days a week for 4 weeks. The results showed that both treatments improved patient neglect, especially in personal and peripersonal spaces. No difference between pretreatment and posttreatment was found in extrapersonal subscales. This finding could be due to the fact that there were no exercises requiring the use of objects within reach in either training. In conclusion, no difference between the 2 approaches was found, and both are useful rehabilitation techniques that appear to improve neglect.

  18. Progress on Developing Adaptive Optics–Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

    OpenAIRE

    Zawadzki, RJ; Capps, AG; Kim, DY; Panorgias, A.; Stevenson, SB; Hamann, B; Werner, JS

    2014-01-01

    Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acqu...

  19. Multi-modal adaptive optics system including fundus photography and optical coherence tomography for the clinical setting.

    Science.gov (United States)

    Salas, Matthias; Drexler, Wolfgang; Levecq, Xavier; Lamory, Barbara; Ritter, Markus; Prager, Sonja; Hafner, Julia; Schmidt-Erfurth, Ursula; Pircher, Michael

    2016-05-01

    We present a new compact multi-modal imaging prototype that combines an adaptive optics (AO) fundus camera with AO-optical coherence tomography (OCT) in a single instrument. The prototype allows acquiring AO fundus images with a field of view of 4°x4° and with a frame rate of 10fps. The exposure time of a single image is 10 ms. The short exposure time results in nearly motion artifact-free high resolution images of the retina. The AO-OCT mode allows acquiring volumetric data of the retina at 200kHz A-scan rate with a transverse resolution of ~4 µm and an axial resolution of ~5 µm. OCT imaging is acquired within a field of view of 2°x2° located at the central part of the AO fundus image. Recording of OCT volume data takes 0.8 seconds. The performance of the new system is tested in healthy volunteers and patients with retinal diseases.

  20. In-vivo imaging of inner retinal cellular morphology with adaptive optics - optical coherence tomography: challenges and possible solutions

    Science.gov (United States)

    Zawadzki, Robert J.; Jones, Steven M.; Kim, Dae Yu; Poyneer, Lisa; Capps, Arlie G.; Hamann, Bernd; Olivier, Scot S.; Werner, John S.

    2012-03-01

    Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the outer layers of the human retina. Despite the significant progress in imaging cone and rod photoreceptor mosaics, visualization of cellular structures in the inner retina has been achieved only with extrinsic contrast agents that have not been approved for use with humans. In this paper we describe the main limiting factors in visualizing inner retinal cells and the methods we implemented to reduce their effects on images acquired with AO-OCT. These include improving the system point spread function (AO performance), monitoring of motion artifacts (retinal motion tracking), and speckle pattern reduction (temporal and spatial averaging). Results of imaging inner retinal morphology and the improvement offered by the new UC Davis AOOCT system with spatio-temporal image averaging are presented.

  1. A Tuning Fork with a Short Fibre Probe Sensor for a Near-FieldScanning Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    王沛; 鲁拥华; 章江英; 明海; 谢建平; 黄建文; 高宗圣; 蔡定平

    2002-01-01

    We report on a tapping-mode tuning fork with a short fibre probe sensor for a near-field scanning optical microscope. The method demonstrates how to fabricate the short fibre probe. This tapping-mode tuning fork with a short fibre probe can provide stable and high Q at the tapping frequency of the tuning fork, and can give high-quality near-field scanning optical microscope and atomic force microscope images of samples. We present the results of using the tapping-mode tuning fork with a short fibre probe sensor for a near-field scanning optical microscope performed on an eight-channel silica waveguide.

  2. Multimodal ophthalmic imaging using swept source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

    Science.gov (United States)

    Malone, Joseph D.; El-Haddad, Mohamed T.; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Tao, Yuankai K.

    2016-03-01

    Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) benefit clinical diagnostic imaging in ophthalmology by enabling in vivo noninvasive en face and volumetric visualization of retinal structures, respectively. Spectrally encoding methods enable confocal imaging through fiber optics and reduces system complexity. Previous applications in ophthalmic imaging include spectrally encoded confocal scanning laser ophthalmoscopy (SECSLO) and a combined SECSLO-OCT system for image guidance, tracking, and registration. However, spectrally encoded imaging suffers from speckle noise because each spectrally encoded channel is effectively monochromatic. Here, we demonstrate in vivo human retinal imaging using a swept source spectrally encoded scanning laser ophthalmoscope and OCT (SSSESLO- OCT) at 1060 nm. SS-SESLO-OCT uses a shared 100 kHz Axsun swept source, shared scanner and imaging optics, and are detected simultaneously on a shared, dual channel high-speed digitizer. SESLO illumination and detection was performed using the single mode core and multimode inner cladding of a double clad fiber coupler, respectively, to preserve lateral resolution while improving collection efficiency and reducing speckle contrast at the expense of confocality. Concurrent en face SESLO and cross-sectional OCT images were acquired with 1376 x 500 pixels at 200 frames-per-second. Our system design is compact and uses a shared light source, imaging optics, and digitizer, which reduces overall system complexity and ensures inherent co-registration between SESLO and OCT FOVs. En face SESLO images acquired concurrent with OCT cross-sections enables lateral motion tracking and three-dimensional volume registration with broad applications in multivolume OCT averaging, image mosaicking, and intraoperative instrument tracking.

  3. Application of a photorefractive bismuth titanate crystal for the construction of adaptive fiber optic seismic receivers

    International Nuclear Information System (INIS)

    The possibility of using a photorefractive Bi12TiO20 crystal to create an adaptive fiber optic geophone has been studied. It is shown that this crystal provides efficient phase demodulation in and adaptive interferometer scheme at low optical powers

  4. Lasers, lenses and light curves : adaptive optics microscopy and peculiar transiting exoplanets

    NARCIS (Netherlands)

    Werkhoven, Theodorus Isaak Mattheus van

    2014-01-01

    In the first part of this thesis, we present an adaptive optics implementation for multi-photon microscopy correcting sample-induced wavefront aberrations using either direct wavefront sensing to run a close-loop adaptive optics system (Chapter 3), or use a model-based sensorless approach to iterati

  5. Adaptive-optic approach to mitigating aero-optic disturbances for a forced shear layer

    Science.gov (United States)

    Nightingale, Alice M.

    Non-uniform, variable-density fields, resulting from compressibility effects in turbulent flows, are the source of aero-optical distortions which cause significant reductions in optical system performance. As a laser beam transverses through an optically active medium, containing index-of-refraction variations, several optical phenomena occur including beam wander, image distortion, and beam defocus. When encountering a variation in the index field, light waves refract causing an otherwise planar wavefront of a laser beam to become aberrated, contributing to the adverse effects mentioned above. Adaptive-Optics (AO) is a technique used to correct for such spatially and temporally varying aberrations on an optical beam by applying a conjugate waveform correction prior to the beams transmission through the flow. Conventional AO systems are bandwidth limited by real-time processing issues and wavefront sensor limitations. Therefore, an alternative to the conventional AO approach has been proposed, developed and evaluated with the goal of overcoming such bandwidth limitations. The alternative AO system, presented throughout this document, consists of two main features; feed-forward flow control and a phase-locked-loop AO control strategy. Initially irregular, unpredictable large-scale structures within a shear layer are regularized using flow control. Subsequently, the resulting optical wavefront, and corresponding optical signal, emerging from the regularized flow becomes more periodic and predictable effectively reducing the bandwidth necessary to make real-time corrections. A phase-lock-loop controller is then used to perform real-time corrections. Wavefront corrections are estimated based upon the regularized flow, while two small aperture laser beams provide a non-intrusive means of acquiring amplitude and phase error measurements. The phase-lock-loop controller uses these signals as feedback to synchronize the deformable mirror's waveform to that of the shear

  6. Nonlinear optical characterization of graphite oxide thin film by open aperture Z-scan technique

    Science.gov (United States)

    Sreeja, V. G.; Cheruvalathu, Ajina; Reshmi, R.; Devasia, Sebin; Anila, E. I.

    2016-05-01

    In this paper we explore the structural characterization of graphite oxide powder prepared from graphite powder by oxidation via modified Hummers method. The nonlinear optical properties of the spin coated graphite oxide thin film is also explored by open aperture Z-Scan technique. Structural and physiochemical properties of the samples were investigated with the help of Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy (Raman).The results of FT-IR and Raman spectroscopy showed that the graphite is oxidized by strong oxidants and the oxygen atoms are introduced into the graphite layers forming C=C, O-H and -C-H groups. The synthesized sample has good crystalline nature with lesser defects. The nonlinear optical property of GO thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated GO thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated to explore its applications in Q switched mode locking laser systems.

  7. Spectroscopy of single emitters using a scanning optical microscope in a dilution refrigerator

    Science.gov (United States)

    Ghosh, Saikat; Heikes, Colin; Wise, Frank; Gaeta, Alexander; Ralph, Dan

    2010-03-01

    We report the design and implementation of a fiber-based optical scanning microscope, capable of operating at temperatures down to 20 mK and in magnetic fields in excess of 9 Tesla, with sub-micron spatial resolution and ultra-low light levels. A home-made modular, piezo-based scanning head is at the heart of the design, with optical fibers coupling light in and out of a commercial dilution refrigerator. The microscope can be operated both in transmission and reflection modes. In the transmission mode, we can analyze the polarization of the light transmitted through the sample down to femto-Watt light levels, using detectors and polarizers integrated with the scanning head inside the refrigerator. In the reflection mode, the instrument can be operated in a confocal geometry in conjunction with single photon counting modules to measure anti-bunching and the decay times of fluorescent photons. We are using this microscope to study individual nano- emitters, focusing initially on spin dynamics in semiconductor quantum dots.

  8. Automated interferometric synthetic aperture microscopy and computational adaptive optics for improved optical coherence tomography.

    Science.gov (United States)

    Xu, Yang; Liu, Yuan-Zhi; Boppart, Stephen A; Carney, P Scott

    2016-03-10

    In this paper, we introduce an algorithm framework for the automation of interferometric synthetic aperture microscopy (ISAM). Under this framework, common processing steps such as dispersion correction, Fourier domain resampling, and computational adaptive optics aberration correction are carried out as metrics-assisted parameter search problems. We further present the results of this algorithm applied to phantom and biological tissue samples and compare with manually adjusted results. With the automated algorithm, near-optimal ISAM reconstruction can be achieved without manual adjustment. At the same time, the technical barrier for the nonexpert using ISAM imaging is also significantly lowered. PMID:26974799

  9. Adaptive Optics for the 8 meter Chinese Giant Solar Telescope

    Science.gov (United States)

    Beckers, Jacques; Liu, Zhong; Deng, Yuanyong; Ji, Haisheng

    2013-12-01

    Solar ELTs enable diffraction limited imaging of the basic structure of the solar atmosphere. Magneto-hydrodynamic considerations limit their size to about 0.03 arcsec. To observe them in the near-infrared 8-meter class telescopes are needed. The Chinese Giant Solar Telescope, or CGST, is such a NIR solar ELT. It is a Ring Telescope with 8-meter outer diameter and a central clear aperture of about 6-meter diameter. At present various options for such a Gregorian type telescope are under study like a continuous ring made of segments or a multiple aperture ring made of 7 off-axis telescopes. The advantages of such a ring telescope is that its MTF covers all spatial frequencies out to those corresponding to its outer diameter, that its circular symmetry makes it polarization neutral, and that its large central hole helps thermal control and provides ample space for MCAO and Gregorian instrumentation. We present the current status of the design of the CGST. Our thinking is guided by the outstanding performance of the 1-meter vacuum solar telescope of the Yunnan Solar Observatory which like the CGST uses both AO and image reconstruction. Using it with a ring-shape aperture mask the imaging techniques for the CGST are being explored. The CGST will have Multi-Conjugate Adaptive Optics (MCAO). The peculiarities of Atmospheric Wavefront Tomography for Ring Telescopes are aided by the ample availability of guide stars on the Sun. IR MCAO-aided diffraction limited imaging offers the advantage of a large FOV, and high solar magnetic field sensitivity. Site testing is proceeding in western China, (e.g. northern Yunnan Province and Tibet). The CGST is a Chinese solar community project originated by the Yunnan Astronomical Observatory, the National Astronomical Observatories, the Purple Mountain Observatory, the Nanjing University, the Nanjing Institute of Astronomical Optics & Technology and the Beijing Normal University.

  10. Adaptive Q control for Tapping-mode Nano-scanning Using a Piezo-actuated Bimorph Probe

    CERN Document Server

    Gunev, Ihsan; Karaman, Sertac; Basdogan, Cagatay

    2012-01-01

    A new approach, called Adaptive Q-control, for tapping-mode Atomic Force Microscopy (AFM) is introduced and implemented on a home-made AFM set-up utilizing a Laser Doppler Vibrometer (LDV) and a piezo-actuated bimorph probe. In the standard Q-control, the effective Q-factor of the scanning probe is adjusted prior to the scanning depending on the application. However, there is a trade-off in setting the effective Q-factor of an AFM probe. The Q-factor is either increased to reduce the tapping forces or decreased to increase the maximum achievable scan speed. Realizing these two benefits simultaneously using the standard Q-control is not possible. In adaptive Q-control, the Q-factor of the probe is set to an initial value as in standard Q-control, but then modified on the fly during scanning when necessary to achieve this goal. In this paper, we present the basic theory behind the adaptive Q-control, the electronics enabling the on-line modification of the probe's effective Q-factor, and the results of the expe...

  11. Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems

    CERN Document Server

    Wu, Zhizheng; Ben Amara, Foued

    2013-01-01

    Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems presents a novel design of wavefront correctors based on magnetic fluid deformable mirrors (MFDM) as well as corresponding control algorithms. The presented wavefront correctors are characterized by their linear, dynamic response. Various mirror surface shape control algorithms are presented along with experimental evaluations of the performance of the resulting adaptive optics systems. Adaptive optics (AO) systems are used in various fields of application to enhance the performance of optical systems, such as imaging, laser, free space optical communication systems, etc. This book is intended for undergraduate and graduate students, professors, engineers, scientists and researchers working on the design of adaptive optics systems and their various emerging fields of application. Zhizheng Wu is an associate professor at Shanghai University, China. Azhar Iqbal is a research associate at the University of Toronto, Canada. Foue...

  12. Handheld scanning probes for optical coherence tomography: developments, applications, and perspectives

    Science.gov (United States)

    Duma, V.-F.; Demian, D.; Sinescu, C.; Cernat, R.; Dobre, G.; Negrutiu, M. L.; Topala, F. I.; Hutiu, Gh.; Bradu, A.; Podoleanu, A. G.

    2016-03-01

    We present the handheld scanning probes that we have recently developed in our current project for biomedical imaging in general and for Optical Coherence Tomography (OCT) in particular. OCT is an established, but dynamic imagistic technique based on laser interferometry, which offers micrometer resolutions and millimeters penetration depths. With regard to existing devices, the newly developed handheld probes are simple, light and relatively low cost. Their design is described in detail to allow for the reproduction in any lab, including for educational purposes. Two probes are constructed almost entirely from off-the-shelf components, while a third, final variant is constructed with dedicated components, in an ergonomic design. The handheld probes have uni-dimensional (1D) galvanometer scanners therefore they achieve transversal sections through the biological sample investigated - in contrast to handheld probes equipped with bi-dimensional (2D) scanners that can also achieve volumetric (3D) reconstructions of the samples. These latter handheld probes are therefore also discussed, as well as the possibility to equip them with galvanometer 2D scanners or with Risley prisms. For galvanometer scanners the optimal scanning functions studied in a series of previous works are pointed out; these functions offer a higher temporal efficiency/duty cycle of the scanning process, as well as artifact-free OCT images. The testing of the handheld scanning probes in dental applications is presented, for metal ceramic prosthesis and for teeth.

  13. Characterization of Line Nanopatterns on Positive Photoresist Produced by Scanning Near-Field Optical Microscope

    Directory of Open Access Journals (Sweden)

    Sadegh Mehdi Aghaei

    2015-01-01

    Full Text Available Line nanopatterns are produced on the positive photoresist by scanning near-field optical microscope (SNOM. A laser diode with a wavelength of 450 nm and a power of 250 mW as the light source and an aluminum coated nanoprobe with a 70 nm aperture at the tip apex have been employed. A neutral density filter has been used to control the exposure power of the photoresist. It is found that the changes induced by light in the photoresist can be detected by in situ shear force microscopy (ShFM, before the development of the photoresist. Scanning electron microscope (SEM images of the developed photoresist have been used to optimize the scanning speed and the power required for exposure, in order to minimize the final line width. It is shown that nanometric lines with a minimum width of 33 nm can be achieved with a scanning speed of 75 µm/s and a laser power of 113 mW. It is also revealed that the overexposure of the photoresist by continuous wave laser generated heat can be prevented by means of proper photoresist selection. In addition, the effects of multiple exposures of nanopatterns on their width and depth are investigated.

  14. Observation of nanostructure by scanning near-field optical microscope with small sphere probe

    Directory of Open Access Journals (Sweden)

    Yasushi Oshikane, Toshihiko Kataoka, Mitsuru Okuda, Seiji Hara, Haruyuki Inoue and Motohiro Nakano

    2007-01-01

    Full Text Available Step and terrace structure has been observed in an area of 1 μm×1 μm on the cleaved surface of KCl–KBr solid-solution single crystal by scanning near-field optical microscope (SNOM with a small sphere probe of 500 nm diameter. Lateral spatial resolution of the SNOM system was estimated to be 20 nm from the observation of step width and the scanning-step interval. Vertical spatial resolution was estimated to be 5–2 nm from the observation of step height and noise level of photomultiplier tube (PMT. With applying a dielectric dipole radiation model to the probe surface, the reason why such a high spatial resolution was obtained in spite of the 500 nm sphere probe, was understood as the effect of the near-field term appeared in the radiation field equations.

  15. A Reflective Gaussian Coronagraph for Extreme Adaptive Optics: Laboratory Performance

    Science.gov (United States)

    Park, Ryeojin; Close, Laird M.; Siegler, Nick; Nielsen, Eric L.; Stalcup, Thomas

    2006-11-01

    We report laboratory results of a coronagraphic test bench to assess the intensity reduction differences between a ``Gaussian'' tapered focal plane coronagraphic mask and a classical hard-edged ``top hat'' function mask at extreme adaptive optics (ExAO) Strehl ratios of ~94%. However, unlike a traditional coronagraph design, we insert a reflective focal plane mask at 45° to the optical axis. We also use an intermediate secondary mask (mask 2) before a final image in order to block additional mask-edge-diffracted light. The test bench simulates the optical train of ground-based telescopes (in particular, the 8.1 m Gemini North Telescope). It includes one spider vane, different mask radii (r = 1.9λ/D, 3.7λ/D, and 7.4λ/D), and two types of reflective focal plane masks (hard-edged top-hat and Gaussian tapered profiles). In order to investigate the relative performance of these competing coronagraphic designs with regard to extrasolar planet detection sensitivity, we utilize the simulation of realistic extrasolar planet populations (Nielsen et al.). With an appropriate translation of our laboratory results to expected telescope performance, a Gaussian tapered mask radius of 3.7λ/D with an additional mask (mask 2) performs best (highest planet detection sensitivity). For a full survey with this optimal design, the simulation predicts that ~30% more planets would be detected than with a top-hat function mask of similar size with mask 2. Using the best design, the point contrast ratio between the stellar point-spread function (PSF) peak and the coronagraphic PSF at 10λ/D (0.4" in the H band if D = 8.1 m) is ~10 times higher than a classical Lyot top-hat coronagraph. Hence, we find that a Gaussian apodized mask with an additional blocking mask is superior (~10 times higher contrast) to the use of a classical Lyot coronagraph for ExAO-like Strehl ratios.

  16. Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

    Science.gov (United States)

    TÜRK, Ayşe Gözde; SABUNCU, Metin; ÜNAL, Sena; ÖNAL, Banu; ULUSOY, Mübin

    2016-01-01

    ABSTRACT Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light beam of OCT (Thorlabs), allowing measurement in 200 µm intervals. Restorations were cemented with a self-adhesive cement resin (SmartCem2, Dentsply), and then marginal adaptations were again measured with OCT. Mean values were statistically compared by using independent-samples t-test and paired samples t-test (p<0.05), before and after cementation. Results Direct inlays presented statistically smaller marginal discrepancy values than indirect inlays, before (p=0.00001442) and after (p=0.00001466) cementation. Marginal discrepancy values were increased for all restorations after cementation (p=0.00008839, p=0.000000952 for direct and indirect inlays, respectively). The mean marginal discrepancy value of the direct group increased from 56.88±20.04 µm to 91.88±31.7 µm, whereas the indirect group increased from 107.54±35.63 µm to 170.29±54.83 µm. Different techniques are available to detect marginal adaptation of restorations, but the OCT system can give quantitative information about resin cement thickness and its interaction between tooth and restoration in a nondestructive manner. Conclusions Direct inlays presented smaller marginal discrepancy than indirect inlays. The marginal discrepancy values were increased for all restorations that refer to cement thickness after cementation

  17. Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

    Science.gov (United States)

    TÜRK, Ayşe Gözde; SABUNCU, Metin; ÜNAL, Sena; ÖNAL, Banu; ULUSOY, Mübin

    2016-01-01

    ABSTRACT Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light beam of OCT (Thorlabs), allowing measurement in 200 µm intervals. Restorations were cemented with a self-adhesive cement resin (SmartCem2, Dentsply), and then marginal adaptations were again measured with OCT. Mean values were statistically compared by using independent-samples t-test and paired samples t-test (pinlays presented statistically smaller marginal discrepancy values than indirect inlays, before (p=0.00001442) and after (p=0.00001466) cementation. Marginal discrepancy values were increased for all restorations after cementation (p=0.00008839, p=0.000000952 for direct and indirect inlays, respectively). The mean marginal discrepancy value of the direct group increased from 56.88±20.04 µm to 91.88±31.7 µm, whereas the indirect group increased from 107.54±35.63 µm to 170.29±54.83 µm. Different techniques are available to detect marginal adaptation of restorations, but the OCT system can give quantitative information about resin cement thickness and its interaction between tooth and restoration in a nondestructive manner. Conclusions Direct inlays presented smaller marginal discrepancy than indirect inlays. The marginal discrepancy values were increased for all restorations that refer to cement thickness after cementation. PMID:27556210

  18. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Science.gov (United States)

    Simeoni, G. G.; Valicu, R. G.; Borchert, G.; Böni, P.; Rasmussen, N. G.; Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A.

    2015-12-01

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4-10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  19. New challenges for Adaptive Optics Extremely Large Telescopes

    CERN Document Server

    Le Louarn, M; Sarazin, M; Tokovinin, A

    2000-01-01

    The performance of an adaptive optics (AO) system on a 100m diameter ground based telescope working in the visible range of the spectrum is computed using an analytical approach. The target Strehl ratio of 60% is achieved at 0.5um with a limiting magnitude of the AO guide source near R~10, at the cost of an extremely low sky coverage. To alleviate this problem, the concept of tomographic wavefront sensing in a wider field of view using either natural guide stars (NGS) or laser guide stars (LGS) is investigated. These methods use 3 or 4 reference sources and up to 3 deformable mirrors, which increase up to 8-fold the corrected field size (up to 60\\arcsec at 0.5 um). Operation with multiple NGS is limited to the infrared (in the J band this approach yields a sky coverage of 50% with a Strehl ratio of 0.2). The option of open-loop wavefront correction in the visible using several bright NGS is discussed. The LGS approach involves the use of a faint (R ~22) NGS for low-order correction, which results in a sky cov...

  20. Micron narrowband adaptive optics imaging in the arches cluster

    CERN Document Server

    Blum, R D; Pasquali, A; Heydari-Malayeri, M; Conti, P S; Schmutz, W

    2001-01-01

    Canada-France-Hawaii-Telescope adaptive optics bonnette images through narrow-band filters in the $K-$band are presented for the Arches cluster. Continuum fluxes, line fluxes, and equivalent widths are derived from high angular resolution images, some near diffraction limited, for the well known massive stars in the Arches cluster. Images were obtained in the lines of \\ion{He}{1} 2.06 \\mic, \\ion{H}{1} Br$\\gamma$ (2.17 \\mic), and \\ion{He}{2} 2.19 \\mic as well as continuum positions at 2.03 \\mic, 2.14 \\mic, and 2.26 \\mic. In addition, fluxes are presented for \\ion{H}{1} P$\\alpha$ (1.87 \\mic) and a nearby continuum position (1.90 \\mic) from Hubble Space Telescope archival data. The 2 \\mic and P$\\alpha$ data reveal two new emission-line stars and three fainter candidate emission-line objects. Indications for a spectral change of one object between earlier observations in 1992/1993 and our data from 1999 are found. The ratio of \\ion{He}{2} 2.19 \\mic to Br$\\gamma$ emission exhibits a narrow distribution among the s...

  1. Adaptive optics near infrared integral field spectroscopy of NGC 2992

    CERN Document Server

    Friedrich, S; Hicks, E K S; Engel, H; Müller-Sánchez, F; Genzel, R; Tacconi, L J

    2010-01-01

    NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows. Observations were performed with the adaptive optics near infrared integral field spectrograph SINFONI on the VLT, complemented by longslit observations with ISAAC on the VLT, as well as N- and Q-band data from the Spitzer archive. The spatial and spectral resolutions of the SINFONI data are 50 pc and 83 km/s, respectively. The field of view of 3" x 3" corresponds to 450 pc x 450 pc. Br_gamma equivalent width and line fluxes from PAHs were compared to stellar population models to constrain the age of the putative recent star formation. A simple geometric model of two mutually inclined disks and an additional cone to describe an outflow was developed to explain the observed complex velocity field in H_2 1-0S(1). The morphologies of the B...

  2. Novel adaptive fiber-optics collimator for coherent beam combination.

    Science.gov (United States)

    Zhi, Dong; Ma, Pengfei; Ma, Yanxing; Wang, Xiaolin; Zhou, Pu; Si, Lei

    2014-12-15

    In this manuscript, we experimentally validate a novel design of adaptive fiber-optics collimator (AFOC), which utilizes two levers to enlarge the movable range of the fiber end cap. The enlargement of the range makes the new AFOC possible to compensate the end-cap/tilt aberration in fiber laser beam combining system. The new AFOC based on flexible hinges and levers was fabricated and the performance of the new AFOC was tested carefully, including its control range, frequency response and control accuracy. Coherent beam combination (CBC) of two 5-W fiber amplifiers array with simultaneously end-cap/tilt control and phase-locking control was implemented successfully with the novel AFOC. Experimental results show that the average normalized power in the bucket (PIB) value increases from 0.311 to 0.934 with active phasing and tilt aberration compensation simultaneously, and with both controls on, the fringe contrast improves to more than 82% from 0% for the case with both control off. This work presents a promising structure for tilt aberration control in high power CBC system.

  3. Adaptive optics for ultra short pulsed lasers in UHV environment

    Science.gov (United States)

    Deneuville, Francois; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-02-01

    ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.

  4. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Simeoni, G. G., E-mail: ggsimeoni@outlook.com [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Valicu, R. G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Borchert, G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Böni, P. [Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Rasmussen, N. G. [Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A. [Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln (Germany)

    2015-12-14

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  5. TH-C-BRD-09: Successes and Limitations of Online Range Adaptive Spot Scanning Proton Therapy for NSCLC

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, JP [UT MD Anderson Cancer Center, Houston, TX (United States); UT Graduate School of Biomedical Sciences at Houston, Houston, TX (United States); Dong, L [Scripps Proton Therapy Center, San Diego, CA (United States); Park, P [Emory University, Scottsdale, GA (United States); Zhu, XR; Kudchadker, RJ; Frank, SJ; Court, LE [UT MD Anderson Cancer Center, Houston, TX (United States)

    2014-06-15

    Purpose: To determine the ability to adapt discrete spot-scanning proton therapy (SSPT) plans based on geometric changes of anatomy to minimize normal tissue dose and maintain target coverage. Methods: We developed and tested a range-correction algorithm to compensate for anatomy changes in SSPT with correction factors for target lateral size changes and energy scaling. This algorithm adjusts the energy of each spot from the original optimized treatment plan to match the new daily anatomy based on water equivalent path-length. To correct for the lateral target size changes, the peripheral spots were scaled based on phantom studies with variable target size. For energy change corrections, alternative cumulative scaling factor lookup tables were generated based on calculated central-axis and integral depth dose calculations for different energies. These various adaptive algorithms were performed on 7 lung cancer patients that were previously treated with proton therapy and who required at least one adaptive intervention. Single-field optimized SSPT plans were generated for these patients with clinical beam angles. Dose-volume histogram metrics were obtained for these patients for both the non-adaptive and the different adaptive plans applied to the last available weekly CT scan. Results: The doses to normal tissue were largely reduced for the spinal cord (Dmax), total lung (V20Gy), and contralateral lung (V20Gy) for all different methods of adaptive planning. With both corrections applied, the average changes for these metrics were −6.2Gy, −2.7%, and −4.9%, respectively. The same method generated unacceptably high target hot spots with average target V110% increase of 12.3%. Conclusion: Adaptive methods based on direct adjustments to proton range can reduce normal tissue doses under large anatomical changes but are insufficient in achieving clinically acceptable target doses and generate unacceptably sizeable hot spots. Adaptive planning methods for proton

  6. TH-C-BRD-09: Successes and Limitations of Online Range Adaptive Spot Scanning Proton Therapy for NSCLC

    International Nuclear Information System (INIS)

    Purpose: To determine the ability to adapt discrete spot-scanning proton therapy (SSPT) plans based on geometric changes of anatomy to minimize normal tissue dose and maintain target coverage. Methods: We developed and tested a range-correction algorithm to compensate for anatomy changes in SSPT with correction factors for target lateral size changes and energy scaling. This algorithm adjusts the energy of each spot from the original optimized treatment plan to match the new daily anatomy based on water equivalent path-length. To correct for the lateral target size changes, the peripheral spots were scaled based on phantom studies with variable target size. For energy change corrections, alternative cumulative scaling factor lookup tables were generated based on calculated central-axis and integral depth dose calculations for different energies. These various adaptive algorithms were performed on 7 lung cancer patients that were previously treated with proton therapy and who required at least one adaptive intervention. Single-field optimized SSPT plans were generated for these patients with clinical beam angles. Dose-volume histogram metrics were obtained for these patients for both the non-adaptive and the different adaptive plans applied to the last available weekly CT scan. Results: The doses to normal tissue were largely reduced for the spinal cord (Dmax), total lung (V20Gy), and contralateral lung (V20Gy) for all different methods of adaptive planning. With both corrections applied, the average changes for these metrics were −6.2Gy, −2.7%, and −4.9%, respectively. The same method generated unacceptably high target hot spots with average target V110% increase of 12.3%. Conclusion: Adaptive methods based on direct adjustments to proton range can reduce normal tissue doses under large anatomical changes but are insufficient in achieving clinically acceptable target doses and generate unacceptably sizeable hot spots. Adaptive planning methods for proton

  7. Guided access cavity preparation using cone-beam computed tomography and optical surface scans - an ex vivo study

    DEFF Research Database (Denmark)

    Buchgreitz, J; Buchgreitz, M; Mortensen, D;

    2016-01-01

    AIM: To evaluate ex vivo, the accuracy of a preparation procedure planned for teeth with pulp canal obliteration (PCO) using a guide rail concept based on a cone-beam computed tomography (CBCT) scan merged with an optical surface scan. METHODOLOGY: A total of 48 teeth were mounted in acrylic bloc...

  8. In vivo integrated photoacoustic ophthalmoscopy, optical coherence tomography, and scanning laser ophthalmoscopy for retinal imaging

    Science.gov (United States)

    Song, Wei; Zhang, Rui; Zhang, Hao F.; Wei, Qing; Cao, Wenwu

    2012-12-01

    The physiological and pathological properties of retina are closely associated with various optical contrasts. Hence, integrating different ophthalmic imaging technologies is more beneficial in both fundamental investigation and clinical diagnosis of several blinding diseases. Recently, photoacoustic ophthalmoscopy (PAOM) was developed for in vivo retinal imaging in small animals, which demonstrated the capability of imaging retinal vascular networks and retinal pigment epithelium (RPE) at high sensitivity. We combined PAOM with traditional imaging modalities, such as fluorescein angiography (FA), spectral-domain optical coherence tomography (SD-OCT), and auto-fluorescence scanning laser ophthalmoscopy (AF-SLO), for imaging rats and mice. The multimodal imaging system provided more comprehensive evaluation of the retina based on the complementary imaging contrast mechanisms. The high-quality retinal images show that the integrated ophthalmic imaging system has great potential in the investigation of blinding disorders.

  9. Initial experience with optical-CT scanning of RadBall Dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Oldham, M; Clift, C; Thomas, A; Farfan, E; Foley, T; Jannik, T; Adamovics, J; Holmes, C; Stanley, S, E-mail: Mark.Oldham@Duke.ed

    2010-11-01

    The RadBall dosimeter is a novel device for providing 3-D information on the magnitude and distribution of contaminant sources of unknown radiation in a given hot cell, glovebox, or contaminated room. The device is presently under evaluation by the National Nuclear Lab (NNL, UK) and the Savannah River National Laboratory (SRNL, US), for application as a diagnostic device for such unknown contaminants in the nuclear industry. A critical component of the technique is imaging the dose distribution recorded in the RadBall using optical-CT scanning. Here we present our initial investigations using the Duke Mid-sized Optical-CT Scanner (DMOS) to image dose distributions deposited in RadBalls exposed to a variety of radiation treatments.

  10. Design and testing of prototype handheld scanning probes for optical coherence tomography.

    Science.gov (United States)

    Demian, Dorin; Duma, Virgil-Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-08-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic-for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat-in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated. PMID:25107512

  11. Scattering-type scanning near-field optical microscopy with reconstruction of vertical interaction

    Science.gov (United States)

    Wang, Le; Xu, Xiaoji G.

    2015-11-01

    Scattering-type scanning near-field optical microscopy provides access to super-resolution spectroscopic imaging of the surfaces of a variety of materials and nanostructures. In addition to chemical identification, it enables observations of nano-optical phenomena, such as mid-infrared plasmons in graphene and phonon polaritons in boron nitride. Despite the high lateral spatial resolution, scattering-type near-field optical microscopy is not able to provide characteristics of near-field responses in the vertical dimension, normal to the sample surface. Here, we present an accurate and fast reconstruction method to obtain vertical characteristics of near-field interactions. For its first application, we investigated the bound electromagnetic field component of surface phonon polaritons on the surface of boron nitride nanotubes and found that it decays within 20 nm with a considerable phase change in the near-field signal. The method is expected to provide characterization of the vertical field distribution of a wide range of nano-optical materials and structures.

  12. Design and testing of prototype handheld scanning probes for optical coherence tomography.

    Science.gov (United States)

    Demian, Dorin; Duma, Virgil-Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-08-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic-for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat-in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated.

  13. Improvement of differential optical absorption spectroscopy with a multichannel scanning technique.

    Science.gov (United States)

    Brauers, T; Hausmann, M; Brandenburger, U; Dorn, H P

    1995-07-20

    Differential optical absorption spectroscopy (DOAS) of atmospheric trace gases requires the detection of optical densities below 0.1%. Photodiode arrays are used more and more as detectors for DOAS because they allow one to record larger spectral intervals simultaneously. This type of optical multichannel analyzer (OMA), however, shows sensitivity differences among the individual photodiodes (pixels), which are of the order of 1%. To correct for this a sensitivity reference spectrum is usually recorded separately from the trace-gas measurements. Because of atmospheric turbulence the illumination of the detector while an atmospheric absorption spectrum is being recorded is different from the conditions during the reference measurement. As a result the sensitivity patterns do not exactly match, and the corrected spectra still show a residual structure that is due to the sensitivity difference. This effect usually limits the detection of optical densities to approximately 3 × 10(-4). A new method for the removal of the sensitivity pattern is presented in this paper: Scanning the spectrometer by small wavelength increments after each readout of the OMA allows one to separate the OMA-fixed pattern and the wavelength-fixed structures (absorption lines). The properties of the new method and its applicability are demonstrated with simulated spectra. Finally, first atmospheric measurements with a laser long-path instrument demonstrate a detection limit of 3 × 10(-5) of a DOAS experiment. PMID:21052280

  14. Adaptive optics assisted visualization of thickened retinal arterial wall in a patient with controlled malignant hypertension

    Directory of Open Access Journals (Sweden)

    Arichika S

    2014-10-01

    Full Text Available Shigeta Arichika, Akihito Uji, Nagahisa Yoshimura Department of Ophthalmology and Visual Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan Purpose: We aimed to visualize the retinal arterial wall thickness, assisted by noninvasive adaptive optics scanning laser ophthalmoscopy (AO-SLO.Methods: The arterial wall thickness was measured and compared between one normal subject and one patient suffering from malignant hypertensive retinopathy.Results: Increased arterial wall thickness was revealed with a newly developed AO-SLO system, in a retinal artery of 1-papilla diameter temporal inferior to the optic disc. The average wall thickness, with hypertension, was 18.7 µm, and the wall-to-lumen ratio was 0.44, both bigger than normal.Conclusion: AO-SLO enabled us to evaluate the retinal wall thickness in the hypertensive patient. The arterial walls were thickened compared with normal. AO-SLO may facilitate future noninvasive study of arterial walls in human medicine. Keywords: wall thickness, AO-SLO, hypertensive retinopathy

  15. First-order design of off-axis reflective ophthalmic adaptive optics systems using afocal telescopes

    Science.gov (United States)

    Gómez-Vieyra, Armando; Dubra, Alfredo; Williams, David R.; Malacara-Hernández, Daniel

    2009-09-01

    Scanning laser ophthalmoscopes (SLOs) and optical coherence tomographs are the state-of-the-art retinal imaging instruments, and are essential for early and reliable diagnosis of eye disease. Recently, with the incorporation of adaptive optics (AO), these instruments have started to deliver near diffraction-limited performance in both humans and animal models, enabling the resolution of the retinal ganglion cell bodies, their processes, the cone photoreceptor and the retinal pigment epithelial cells mosaics. Unfortunately, these novel instruments have not delivered consistent performance across human subjects and animal models. One of the limitations of current instruments is the astigmatism in the pupil and imaging planes, which degrades image quality, by preventing the wavefront sensor from measuring aberrations with high spatial content. This astigmatism is introduced by the sequence of off-axis reflective elements, typically spherical mirrors, used for relaying pupil and imaging planes. Expressions for minimal astigmatism on the image and pupil planes in off-axis reflective afocal telescopes formed by pairs of spherical mirrors are presented. The formulas, derived from the marginal ray fans equation, are valid for small angles of incidence (systems. An example related to this last application is discussed.

  16. Marginal adaptation analysis performed with en face optical coherence tomography in fixed partial dentures

    Science.gov (United States)

    Sinescu, Cosmin; Negrutiu, Meda Lavinia; Antonie, Sergiu; Dobre, George; Bradu, Adrian; Hughes, Michael; Rominu, Mihai; Podoleanu, Adrian Gh.

    2009-02-01

    Frameworks for fixed partial denture made out of dental alloys thought classic techniques currently involve many errors like marginal and internal gaps. The aim of this study is to present alternative technologies in making frameworks from dental alloys using selective laser sintering/ selective laser melting (SLS/ SLM) and to investigate the marginal adaptation of the fixed dental prostheses using the en face optical coherence tomography. These procedures imply the use of a scanning device PROBIS, SMART OPTICS with the help of 3D Dental Scanner software. For digitizing the 3D model we used the Dental Wings Kunde Software. The files obtained were sent to a SLS/ SLM machine, Hint-Els rapidPro, where the CoCr powder was sintered/melt by selectively consolidating successive layers of powder material on top of each other, using thermal energy supplied by a focused and computer controlled laser beam. Through this technique can be produced up to 80 pieces in only one step. A parallel between the classic casting technique and this new technology reveal the least has several advantages: fast finishing time, excellent marginal and internal fit, biocompatibility and superior chemical properties. SLS/ SLM proved to be a promising technology that may overcome the classic ones, because of the superior marginal fit of the fixed dental prostheses to the teeth.

  17. Coherence gated wavefront sensorless adaptive optics for two photon excited fluorescence retinal imaging (Conference Presentation)

    Science.gov (United States)

    Jian, Yifan; Cua, Michelle; Bonora, Stefano; Pugh, Edward N.; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    We present a novel system for adaptive optics two photon imaging. We utilize the bandwidth of the femtosecond excitation beam to perform coherence gated imaging (OCT) of the sample. The location of the focus is directly observable in the cross sectional OCT images, and adjusted to the desired depth plane. Next, using real time volumetric OCT, we perform Wavefront Sensorless Adaptive Optics (WSAO) aberration correction using a multi-element adaptive lens capable of correcting up to 4th order Zernike polynomials. The aberration correction is performed based on an image quality metric, for example intensity. The optimization time is limited only by the OCT acquisition rate, and takes ~30s. Following aberration correction, two photon fluorescence images are acquired, and compared to results without adaptive optics correction. This technique is promising for multiphoton imaging in multi-layered, scattering samples such as eye and brain, in which traditional wavefront sensing and guide-star sensorless adaptive optics approaches may not be suitable.

  18. The optical design of a visible adaptive optics system for the Magellan Telescope

    Science.gov (United States)

    Kopon, Derek

    The Magellan Adaptive Optics system will achieve first light in November of 2012. This AO system contains several subsystems including the 585-actuator concave adaptive secondary mirror, the Calibration Return Optic (CRO) alignment and calibration system, the CLIO 1-5 microm IR science camera, the movable guider camera and active optics assembly, and the W-Unit, which contains both the Pyramid Wavefront Sensor (PWFS) and the VisAO visible science camera. In this dissertation, we present details of the design, fabrication, assembly, alignment, and laboratory performance of the VisAO camera and its optical components. Many of these components required a custom design, such as the Spectral Differential Imaging Wollaston prisms and filters and the coronagraphic spots. One component, the Atmospheric Dispersion Corrector (ADC), required a unique triplet design that had until now never been fabricated and tested on sky. We present the design, laboratory, and on-sky results for our triplet ADC. We also present details of the CRO test setup and alignment. Because Magellan is a Gregorian telescope, the ASM is a concave ellipsoidal mirror. By simulating a star with a white light point source at the far conjugate, we can create a double-pass test of the whole system without the need for a real on-sky star. This allows us to test the AO system closed loop in the Arcetri test tower at its nominal design focal length and optical conjugates. The CRO test will also allow us to calibrate and verify the system off-sky at the Magellan telescope during commissioning and periodically thereafter. We present a design for a possible future upgrade path for a new visible Integral Field Spectrograph. By integrating a fiber array bundle at the VisAO focal plane, we can send light to a pre-existing facility spectrograph, such as LDSS3, which will allow 20 mas spatial sampling and R˜1,800 spectra over the band 0.6-1.05 microm. This would be the highest spatial resolution IFU to date, either

  19. Analysis of the dynamics and frequency spectrum synthesis of an optical-mechanical scanning device

    Science.gov (United States)

    Andryushkevichyus, A. I.; Kumpikas, A. L.; Kumpikas, K. L.

    1973-01-01

    A two-coordinate optical-mechanical scanning device (OMSD), the operating unit of which is a scanning disk, with directional and focusing optics and a board, on which the data carrier is placed, is examined. The disk and board are kinematically connected by a transmission mechanism, consisting of a worm and complex gear drive and a tightening screw-nut with correcting device, and it is run by a synchronous type motor. The dynamic errors in the system depend, first, on irregularities in rotation of the disk, fluctuations in its axis and vibrations of the table in the plane parallel to the plane of the disk. The basic sources of the fluctuations referred to above are residual disbalance of the rotor and other rotating masses, the periodic component of the driving torque of the synchronous motor, variability in the resistance, kinematic errors in the drive and other things. The fluctuations can be transmitted to the operating units through the kinematic link as a flexural-torsional system, as well as through vibrations of the housing of the device.

  20. Reciprocity theory of apertureless scanning near-field optical microscopy with point-dipole probes.

    Science.gov (United States)

    Esslinger, Moritz; Vogelgesang, Ralf

    2012-09-25

    Near-field microscopy offers the opportunity to reveal optical contrast at deep subwavelength scales. In scanning near-field optical microscopy (SNOM), the diffraction limit is overcome by a nanoscopic probe in close proximity to the sample. The interaction of the probe with the sample fields necessarily perturbs the bare sample response, and a critical issue is the interpretation of recorded signals. For a few specific SNOM configurations, individual descriptions have been modeled, but a general and intuitive framework is still lacking. Here, we give an exact formulation of the measurable signals in SNOM which is easily applicable to experimental configurations. Our results are in close analogy with the description Tersoff and Hamann have derived for the tunneling currents in scanning tunneling microscopy. For point-like scattering probe tips, such as used in apertureless SNOM, the theory simplifies dramatically to a single scalar relation. We find that the measured signal is directly proportional to the field of the coupled tip-sample system at the position of the tip. For weakly interacting probes, the model thus verifies the empirical findings that the recorded signal is proportional to the unperturbed field of the bare sample. In the more general case, it provides guidance to an intuitive and faithful interpretation of recorded images, facilitating the characterization of tip-related distortions and the evaluation of novel SNOM configurations, both for aperture-based and apertureless SNOM.

  1. Ultrafast random-access scanning in two-photon microscopy using acousto-optic deflectors.

    Science.gov (United States)

    Salomé, R; Kremer, Y; Dieudonné, S; Léger, J-F; Krichevsky, O; Wyart, C; Chatenay, D; Bourdieu, L

    2006-06-30

    Two-photon scanning microscopy (TPSM) is a powerful tool for imaging deep inside living tissues with sub-cellular resolution. The temporal resolution of TPSM is however strongly limited by the galvanometric mirrors used to steer the laser beam. Fast physiological events can therefore only be followed by scanning repeatedly a single line within the field of view. Because acousto-optic deflectors (AODs) are non-mechanical devices, they allow access at any point within the field of view on a microsecond time scale and are therefore excellent candidates to improve the temporal resolution of TPSM. However, the use of AOD-based scanners with femtosecond pulses raises several technical difficulties. In this paper, we describe an all-digital TPSM setup based on two crossed AODs. It includes in particular an acousto-optic modulator (AOM) placed at 45 degrees with respect to the AODs to pre-compensate for the large spatial distortions of femtosecond pulses occurring in the AODs, in order to optimize the spatial resolution and the fluorescence excitation. Our setup allows recording from freely selectable point-of-interest at high speed (1kHz). By maximizing the time spent on points of interest, random-access TPSM (RA-TPSM) constitutes a promising method for multiunit recordings with millisecond resolution in biological tissues.

  2. Multimodal imaging of the human temporal bone: A comparison of CT and optical scanning techniques

    Science.gov (United States)

    Voie, Arne H.; Whiting, Bruce; Skinner, Margaret; Neely, J. Gail; Lee, Kenneth; Holden, Tim; Brunsden, Barry

    2003-10-01

    A collaborative effort between Washington University in St. Louis and Spencer Technologies in Seattle, WA has been undertaken to create a multimodal 3D reconstruction of the human cochlea and vestibular system. The goal of this project is to improve the accuracy of in vivo CT reconstructions of implanted cochleae, and to expand the knowledge of high-resolution anatomical detail provided by orthogonal-plane optical sectioning (OPFOS). At WUSL, computed tomography (CT) images of the cochlea are used to determine the position of cochlear implant electrodes relative to target auditory neurons. The cochlear implant position is determined using pre- and post-operative CT scans. The CT volumes are cross-registered to align the semicircular canals and internal auditory canal, which have a unique configuration in 3-D space. The head of a human body donor was scanned with a clinical CT device, after which the temporal bones were removed, fixed in formalin and trimmed prior to scanning with a laboratory Micro CT scanner. Following CT, the temporal bones were sent to the OPFOS Imaging Lab at Spencer Technologies for a further analysis. 3-D reconstructions of CT and OPFOS imaging modalities were compared, and results are presented. [Work supported by NIDCD Grants R44-03623-5 and R01-00581-13.

  3. Endoscopic optical coherence tomography of the retina at 1310 nm using paired-angle rotating scanning

    Science.gov (United States)

    Sarunic, Marinko V.; Han, Shuo; Wu, Jigang; Yaqoob, Zahid; Humayun, Mark; Yang, Changhuei

    2007-02-01

    Vitrectomy (removal of the vitreous humor) is an ophthalmic surgery required as a precursor to several posterior chamber procedures. Vitrectomy is commonly performed using an endoscopic vitreous cutter and fiber based light delivery for observation through a surgical microscope. Cross-sectional visualization of the retina and remnant vitreous layers during surgery using an external optical coherence tomography (OCT) scanner is impractical due to deformation in the shape of the eye and the cornea. We present a forward imaging probe with 820 μm outer diameter (21 gauge needle) for cross-sectional endoscopic OCT imaging during ophthalmic surgeries. The Paired-Angle-Rotating Scanner (PARS) OCT probe is based on angle polished gradient index (GRIN) lenses which are rotated about the optical axis. The scan pattern is determined by the angle between the GRIN lenses and the relative angular velocity. Endoscopic placement of the PARS-OCT probe tip near the retinal surface permits use of a longer wavelength light, in particular 1310 nm, which would otherwise suffer significant attenuation traversing the vitreous humor. The prototype endoscopic PARS-OCT probe is coupled to a commercially available 1310 nm swept laser source, and uses commercial software for data acquisition, processing, and display of retinal images in real time at an A-scan rate of 16 kHz. We present an analysis of aberrations due to off axis use of GRIN lenses and measure the scan pattern of the PARS probe. Images acquired on an ex vivo porcine retina are presented, motivating development of the endoscopic PARS-OCT probe for clinical evaluation.

  4. Modeling a Miniaturized Scanning Electron Microscope Focusing Column - Lessons Learned in Electron Optics Simulation

    Science.gov (United States)

    Loyd, Jody; Gregory, Don; Gaskin, Jessica

    2016-01-01

    This presentation discusses work done to assess the design of a focusing column in a miniaturized Scanning Electron Microscope (SEM) developed at the NASA Marshall Space Flight Center (MSFC) for use in-situ on the Moon-in particular for mineralogical analysis. The MSFC beam column design uses purely electrostatic fields for focusing, because of the severe constraints on mass and electrical power consumption imposed by the goals of lunar exploration and of spaceflight in general. The resolution of an SEM ultimately depends on the size of the focused spot of the scanning beam probe, for which the stated goal here is a diameter of 10 nanometers. Optical aberrations are the main challenge to this performance goal, because they blur the ideal geometrical optical image of the electron source, effectively widening the ideal spot size of the beam probe. In the present work the optical aberrations of the mini SEM focusing column were assessed using direct tracing of non-paraxial rays, as opposed to mathematical estimates of aberrations based on paraxial ray-traces. The geometrical ray-tracing employed here is completely analogous to ray-tracing as conventionally understood in the realm of photon optics, with the major difference being that in electron optics the lens is simply a smoothly varying electric field in vacuum, formed by precisely machined electrodes. Ray-tracing in this context, therefore, relies upon a model of the electrostatic field inside the focusing column to provide the mathematical description of the "lens" being traced. This work relied fundamentally on the boundary element method (BEM) for this electric field model. In carrying out this research the authors discovered that higher accuracy in the field model was essential if aberrations were to be reliably assessed using direct ray-tracing. This led to some work in testing alternative techniques for modeling the electrostatic field. Ultimately, the necessary accuracy was attained using a BEM

  5. Probing other solar systems with current and future adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B; Marois, C; Phillion, D; Poyneer, L; Graham, J; Zuckerman, B; Gavel, D; Veran, J; Wilhelmsen-Evans, J; Mellis, C

    2008-09-08

    Over the past decade, the study of extrasolar planets through indirect techniques--primarily Doppler measurements--has revolutionized our understanding of other solar systems. The next major step in this field will be the direct detection and characterization, via imaging and spectroscopy, of the planets themselves. To achieve this, we must separate the light from the faint planet from the extensive glare of its parent star. We pursued this goal using the current generation of adaptive optics (AO) systems on large ground-based telescopes, using infrared imaging to search for the thermal emission from young planets and developing image processing techniques to distinguish planets from telescope-induced artifacts. Our new Angular Differential Imaging (ADI) technique, which uses the sidereal rotation of the Earth and telescope, is now standard for ground-based high-contrast imaging. Although no young planets were found in our surveys, we placed the strongest limits yet on giant planets in wide orbits (>30 AU) around young stars and characterized planetary companion candidates. The imaging of planetary companions on solar-system-like scales (5-30 AU) will require a new generation of advanced AO systems that are an order of magnitude more powerful than the LLNL-built Keck AO system. We worked to develop and test the key technologies needed for these systems, including a spatially-filtered wavefront sensor, efficient and accurate wavefront reconstruction algorithms, and precision AO wavefront control at the sub-nm level. LLNL has now been selected by the Gemini Observatory to lead the construction of the Gemini Planet Imager, a $24M instrument that will be the most advanced AO system in the world.

  6. Three-dimensional phase-contrast X-ray microtomography with scanning-imaging X-ray microscope optics.

    Science.gov (United States)

    Takeuchi, Akihisa; Uesugi, Kentaro; Suzuki, Yoshio

    2013-09-01

    A three-dimensional (3D) X-ray tomographic micro-imaging system has been developed. The optical system is based on a scanning-imaging X-ray microscope (SIXM) optics, which is a hybrid system consisting of a scanning microscope optics with a one-dimensional (1D) focusing (line-focusing) device and an imaging microscope optics with a 1D objective. In the SIXM system, each 1D dataset of a two-dimensional (2D) image is recorded independently. An object is illuminated with a line-focused beam. Positional information of the region illuminated by the line-focused beam is recorded with the 1D imaging microscope optics as line-profile data. By scanning the object with the line focus, 2D image data are obtained. In the same manner as for a scanning microscope optics with a multi-pixel detector, imaging modes such as phase contrast and absorption contrast can be arbitrarily configured after the image data acquisition. By combining a tomographic scan method and the SIXM system, quantitative 3D imaging is performed. Results of a feasibility study of the SIXM for 3D imaging are shown.

  7. SU-E-J-78: Adaptive Planning Workflow in a Pencil Beam Scanning Proton Therapy Center

    Energy Technology Data Exchange (ETDEWEB)

    Blakey, M; Price, S; Robison, B; Niek, S; Moe, S; Renegar, J; Mark, A; Spenser, W [Provision Healthcare Partners, Knoxville, TN (United States)

    2015-06-15

    Purpose: The susceptibility of proton therapy to changes in patient setup and anatomy necessitates an adaptive planning process. With the right planning tools and clinical workflow, an adaptive plan can be created in a timely manner without adding significant workload to the treatment planning staff. Methods: In our center, a weekly QA CT is performed on most patients to assess setup, anatomy change, and tumor response. The QA CT is fused to the treatment planning CT, the contours are transferred via deformable registration, and the plan dose is recalculated on the QA CT. A physicist assesses the dose distribution, and an adaptive plan is requested based on tumor coverage or OAR dose changes. After the physician confirms or alters the deformed contours, a dosimetrist develops an adaptive plan using our TPS adaptation module. The plan is assessed for robustness and is then reviewed by the physician. Patient QA is performed within three days following the first adapted treatment. Results: Of the patients who received QA CTs, 19% required at least one adaptive plan (18.5% H&N, 18.5% brain, 11.1% breast, 14.8% chestwall, 14.8% lung, 18.5% pelvis and 3.8% abdomen). Of these patients, 14% went on a break, while the remainder was treated with the previous plan during the re-planning process. Adaptive plans were performed based on tumor shrinkage, anatomy change or positioning uncertainties for 37.9%, 44.8%, and 17.3% of the patients, respectively. On average, 3 full days are required between the QA CT and the first adapted plan treatment. Conclusion: Adaptive planning is a crucial component of proton therapy and should be applied to any site when the QA CT shows significant deviation from the plan. With an efficient workflow, an adaptive plan can be applied without delaying patient treatment or burdening the dosimetry and medical physics team.

  8. SU-E-J-78: Adaptive Planning Workflow in a Pencil Beam Scanning Proton Therapy Center

    International Nuclear Information System (INIS)

    Purpose: The susceptibility of proton therapy to changes in patient setup and anatomy necessitates an adaptive planning process. With the right planning tools and clinical workflow, an adaptive plan can be created in a timely manner without adding significant workload to the treatment planning staff. Methods: In our center, a weekly QA CT is performed on most patients to assess setup, anatomy change, and tumor response. The QA CT is fused to the treatment planning CT, the contours are transferred via deformable registration, and the plan dose is recalculated on the QA CT. A physicist assesses the dose distribution, and an adaptive plan is requested based on tumor coverage or OAR dose changes. After the physician confirms or alters the deformed contours, a dosimetrist develops an adaptive plan using our TPS adaptation module. The plan is assessed for robustness and is then reviewed by the physician. Patient QA is performed within three days following the first adapted treatment. Results: Of the patients who received QA CTs, 19% required at least one adaptive plan (18.5% H&N, 18.5% brain, 11.1% breast, 14.8% chestwall, 14.8% lung, 18.5% pelvis and 3.8% abdomen). Of these patients, 14% went on a break, while the remainder was treated with the previous plan during the re-planning process. Adaptive plans were performed based on tumor shrinkage, anatomy change or positioning uncertainties for 37.9%, 44.8%, and 17.3% of the patients, respectively. On average, 3 full days are required between the QA CT and the first adapted plan treatment. Conclusion: Adaptive planning is a crucial component of proton therapy and should be applied to any site when the QA CT shows significant deviation from the plan. With an efficient workflow, an adaptive plan can be applied without delaying patient treatment or burdening the dosimetry and medical physics team

  9. Adaptive optics in nonlinear microscopy implemented with open-loop control and EMCCD-based Shack-Hartmann wavefront sensor

    Science.gov (United States)

    Sun, Wei

    Nonlinear microscopy, with its unique advantages over conventional confocal fluorescence microscopy, has been widely adopted to study biological processes at the cellular level. However, like all other high-resolution optical imaging techniques, nonlinear microscopy suffers from focal degradation due to optical aberrations in the sample as a result of refractive index mismatch. Optical aberrations distort the wavefront of the excitation beam, causing the focal spot to be larger than the diffraction limit. Since the fluorescence efficiency scales nonlinearly with the profile of the focusing excitation beam, aberrations further degrade the image brightness in addition to resolution. In this dissertation I describe the design, characterization and experimentation of an adaptive optics (AO) nonlinear laser scanning microscope implemented with open-loop control and an EMCCD-based Shack-Hartmann wavefront sensor (EMCCD SHWFS) for aberration compensation. Adaptive optics (AO), originally designed for ground-based astronomical observatories to correct for the aberrations from atmospheric turbulence while imaging distant stars and planets, has benefited many biomedical imaging platforms. We integrated a microelectromechanical system (MEMS) deformable mirror (DM) into our nonlinear laser scanning microscope. With an accurate open-loop control mechanism, which predicts the control voltages and generates a prescribed surface shape on the MEMS DM, known aberrations in the system can be compensated for with this computationally simple and inherently fast method. The use of a nonlinear guide star imbedded within the sample can reflect the sample aberration. However, the low level of nonlinear fluorescence signal is usually detected by photomultiplier tubes (PMT) and is below the sensitivity of a conventional charge-coupled device (CCD) based Shack-Hartmann wavefront sensor. This dissertation also describes the design of an EMCCD SHWFS to measure the wavefront distortion from the

  10. Three-dimensional imaging of intracochlear tissue by scanning laser optical tomography (SLOT)

    Science.gov (United States)

    Tinne, N.; Nolte, L.; Antonopoulos, G. C.; Schulze, J.; Andrade, J.; Heisterkamp, A.; Meyer, H.; Warnecke, A.; Majdani, O.; Ripken, T.

    2016-02-01

    The presented study focuses on the application of scanning laser optical tomography (SLOT) for non-destructive visualization of anatomical structures inside the human cochlea ex vivo. SLOT is a laser-based highly efficient microscopy technique, which allows for tomographic imaging of the internal structure of transparent large-scale specimens (up to 1 cm3). Thus, in the field of otology this technique is best convenient for an ex vivo study of the inner ear anatomy. For this purpose, the preparation before imaging comprises mechanically assisted decalcification, dehydration as well as optical clearing of the cochlea samples. Here, we demonstrate results of SLOT visualizing hard and soft tissue structures of the human cochlea with an optical resolution in the micrometer range using absorption and autofluorescence as contrast mechanisms. Furthermore, we compare our results with the method of X-ray micro tomography (micro-CT, μCT) as clinical gold standard which is based only on absorption. In general, SLOT can provide the advantage of covering all contrast mechanisms known from other light microscopy techniques, such as fluorescence or scattering. For this reason, a protocol for antibody staining has been developed, which additionally enables selective mapping of cellular structures within the cochlea. Thus, we present results of SLOT imaging rodent cochleae showing specific anatomical structures such as hair cells and neurofilament via fluorescence. In conclusion, the presented study has shown that SLOT is an ideally suited tool in the field of otology for in toto visualization of the inner ear microstructure.

  11. Implant adaptation of stock abutments versus CAD/CAM abutments: a radiographic and Scanning Electron Microscopy study

    Science.gov (United States)

    Apicella, Davide; Veltri, Mario; Chieffi, Nicoletta; Polimeni, Antonella; Giovannetti, Agostino; Ferrari, Marco

    2011-01-01

    Summary Introduction The study evaluated a null-hypothesis of no differences of fit between stock abutments and CAD/CAM titanium, gold sputtered and zirconia abutments when examined for radiographic adaptation and Scanning Electron Microcopy (SEM) at their inner aspect. The agreement between microscopic and radiographic fit was also assessed. Methods Implants (Osseospeed, Astra Tech, Mölndal, Sweden) were connected to titanium abutments (Ti-design, Astra Tech, Mölndal, Sweden) (control group n=12), to stock zirconia abutments (Zir-design, Astra Tech) (group 1 n=12) and to third party zirconia abutments (Aadva Zr abutment, GC, Tokyo, Japan) as observed under SEM (JEOL JSM-6060LV, Tokyo, Japan). Two independent operators blindly evaluated the images, according to a three-score scale: perfect adaptation, no complete adaptation, and clear evidence of no adaptation. A Kruskal-Wallis test was applied to assess significant differences in adaptation scores between the groups. Results All specimens showed precise SEM adaptation at all tested interfaces and no radiographically apparent gaps. No significant differences were found and therefore the null-hypothesis tested was accepted. Radiographic and SEM scores were in agreement. Discussion CAD/CAM titanium, gold sputtered and zirconia abutments and third-part CAD/CAM zirconia abutments show an adaptation to Astra Tech implants that is comparable to that of stock titanium and zirconia abutments. Clinicians might be able to verify such adaptation with an x-ray. In-vivo studies would be needed to evaluate the clinical outcome of CAD/CAM abutments. PMID:22238709

  12. Adaptive Integrated Optical Bragg Grating in Semiconductor Waveguide Suitable for Optical Signal Processing

    Science.gov (United States)

    Moniem, T. A.

    2016-05-01

    This article presents a methodology for an integrated Bragg grating using an alloy of GaAs, AlGaAs, and InGaAs with a controllable refractive index to obtain an adaptive Bragg grating suitable for many applications on optical processing and adaptive control systems, such as limitation and filtering. The refractive index of a Bragg grating is controlled by using an external electric field for controlling periodic modulation of the refractive index of the active waveguide region. The designed Bragg grating has refractive indices programmed by using that external electric field. This article presents two approaches for designing the controllable refractive indices active region of a Bragg grating. The first approach is based on the modification of a planar micro-strip structure of the iGaAs traveling wave as the active region, and the second is based on the modification of self-assembled InAs/GaAs quantum dots of an alloy from GaAs and InGaAs with a GaP traveling wave. The overall design and results are discussed through numerical simulation by using the finite-difference time-domain, plane wave expansion, and opto-wave simulation methods to confirm its operation and feasibility.

  13. The numerical simulation tool for the MAORY multiconjugate adaptive optics system

    CERN Document Server

    Arcidiacono, Carmelo; Bregoli, Giovanni; Diolaiti, Emiliano; Foppiani, Italo; Agapito, Guido; Puglisi, Alfio; Xompero, Marco; Oberti, Sylvain; Cosentino, Giuseppe; Lombini, Matteo; Butler, Chris R; Ciliegi, Paolo; Cortecchia, Fausto; Patti, Mauro; Esposito, Simone; Feautrier, Philippe

    2016-01-01

    The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is a hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implements the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and uses libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

  14. 自适应光传送网%Adaptive Optical Transport Network

    Institute of Scientific and Technical Information of China (English)

    王加莹; 赵继军; 刘赛

    2005-01-01

    提出未来光网络的智能化特征,包括连接智能化、业务智能化和传输自适应三个方面.这几个方面的特征将成为未来自适应光传送网的标志.%Intelligent features of future optical transport self-adaptation' ,which will construct an integrated earmark of future self-adaptive optical transport network.

  15. Experimental Adaptive Digital Performance Monitoring for Optical DP-QPSK Coherent Receiver

    DEFF Research Database (Denmark)

    Borkowski, Robert; Zhang, Xu; Zibar, Darko;

    2011-01-01

    We report on a successful experimental demonstration of a digital optical performance monitoring (OPM) yielding satisfactory estimation accuracy along with adaptive impairment equalization. No observable penalty is measured when equalizer is driven by monitoring module.......We report on a successful experimental demonstration of a digital optical performance monitoring (OPM) yielding satisfactory estimation accuracy along with adaptive impairment equalization. No observable penalty is measured when equalizer is driven by monitoring module....

  16. High resolution mesospheric sodium properties for adaptive optics applications

    Science.gov (United States)

    Pfrommer, T.; Hickson, P.

    2014-05-01

    Context. The performance of laser guide star adaptive optics (AO) systems for large optical and infrared telescopes is affected by variability of the sodium layer, located at altitudes between 80 and 120 km in the upper mesosphere and lower thermosphere. The abundance and density structure of the atomic sodium found in this region is subject to local and global weather effects, planetary and gravity waves and magnetic storms, and is variable on time scales down to tens of milliseconds, a range relevant to AO. Aims: It is therefore important to characterize the structure and dynamical evolution of the sodium region on small, as well as large spatial and temporal scales. Parameters of particular importance for AO are the mean sodium altitude, sodium layer width and the temporal power spectrum of the centroid altitude. Methods: We have conducted a three-year campaign employing a high-resolution lidar system installed on the 6-m Large Zenith Telescope (LZT) located near Vancouver, Canada. During this period, 112 nights of useful data were obtained. Results: The vertical density profile of atomic sodium shows remarkable structure and variability. Smooth Gaussian-shaped profiles rarely occur. Multiple internal layers are frequently found. These layers often have sharp lower edges, with scale heights of just a few hundred meters, and tend to drift downwards at a typical rate of one kilometer every two to three hours. Individual layers can persist for many hours, but their density and internal structure can be highly variable. Sporadic layers are seen reaching peak densities several times the average, often in just a few minutes. Coherent vertical oscillations are often found, typically extending over tens of kilometers in altitude. Regions of turbulence are evident and Kelvin-Helmholtz instability are sometimes seen. The mean value of the centroid altitude is found to be 90.8 ± 0.1 km. The sodium layer width was determined by computing the altitude range that contains a

  17. Measurements of nonlinear optical properties of PVDF/ZnO using Z-scan technique

    Energy Technology Data Exchange (ETDEWEB)

    Shanshool, Haider Mohammed, E-mail: haidshan62@gmail.com [Ministry of Science and Technology, Baghdad (Iraq); Yahaya, Muhammad [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor (Malaysia); Yunus, Wan Mahmood Mat [Department of Physics, Faculty of Science, University Putra Malaysia, Serdang (Malaysia); Abdullah, Ibtisam Yahya [Department of Physics, College of Science, University of Mosul, Mosul (Iraq)

    2015-10-15

    The nonlinear optical properties of ZnO nanoparticles dispersed in poly (vinylidene fluoride) (PVDF) polymer are investigated. PVDF/ZnO nanocomposites were prepared by mixing different concentrations of ZnO nanoparticles, as the filler, with PVDF, as the polymer matrix, using casting method. Acetone was used as a solvent for the polymer. FTIR spectra of the samples were analyzed thus confirming the formation of α and β phases. The absorbance spectra of the samples were obtained, thereby showing high absorption in the UV region. The linear absorption coefficient was calculated. The single-beam Z-scan technique was used to measure the nonlinear refractive index and the nonlinear absorption coefficient of the PVDF/ZnO nanocomposite samples. We observed that the nonlinear refractive index is in the order of 10{sup -13} cm{sup 2}/W with the negative sign, whereas the nonlinear absorption coefficient is in the order of 10{sup -8} cm/W. (author)

  18. Novel grid-based optical Braille conversion: from scanning to wording

    Science.gov (United States)

    Yoosefi Babadi, Majid; Jafari, Shahram

    2011-12-01

    Grid-based optical Braille conversion (GOBCO) is explained in this article. The grid-fitting technique involves processing scanned images taken from old hard-copy Braille manuscripts, recognising and converting them into English ASCII text documents inside a computer. The resulted words are verified using the relevant dictionary to provide the final output. The algorithms employed in this article can be easily modified to be implemented on other visual pattern recognition systems and text extraction applications. This technique has several advantages including: simplicity of the algorithm, high speed of execution, ability to help visually impaired persons and blind people to work with fax machines and the like, and the ability to help sighted people with no prior knowledge of Braille to understand hard-copy Braille manuscripts.

  19. Polarization Properties in Apertureless-Type Scanning Near-Field Optical Microscopy.

    Science.gov (United States)

    Ishibashi, Takayuki; Cai, Yongfu

    2015-12-01

    Polarization properties of apertureless-type scanning near-field optical microscopy (a-SNOM) were measured experimentally and were also analyzed using a finite-difference time-domain (FDTD) simulation. Our study reveals that the polarization properties in the a-SNOM are maintained and the a-SNOM works as a wave plate expressed by a Jones matrix. The measured signals obtained by the lock-in detection technique could be decomposed into signals scattered from near-field region and background signals reflected by tip and sample. Polarization images measured by a-SNOM with an angle resolution of 1° are shown. FDTD analysis also reveals the polarization properties of light in the area between a tip and a sample are p-polarization in most of cases. PMID:26415540

  20. Scanning magneto-optical Kerr microscope with auto-balanced detection scheme.

    Science.gov (United States)

    Halahovets, Y; Siffalovic, P; Jergel, M; Senderak, R; Majkova, E; Luby, S; Kostic, I; Szymanski, B; Stobiecki, F

    2011-08-01

    We have developed a scanning magneto-optical Kerr microscope dedicated to localization and measurement of the in-plane magnetization of ultra-thin layered magnetic nanostructures with high sensitivity and signal-to-noise ratio. The novel light detection scheme is based on a differential photodetector with automatic common mode noise rejection system with a high noise suppression up to 50 dB. The sensitivity of the developed detection scheme was tested by measurement of a single Co layer and a giant magnetoresistance (GMR) multilayer stack. The spatial resolution of the Kerr microscope was demonstrated by mapping an isolated 5×5 μm spin-valve pillar. PMID:21895250

  1. Adaptative Multigrid and Variable Parameterization for Optical-flow Estimation

    OpenAIRE

    Memin, Etienne; Pérez, Patrick

    1997-01-01

    We investigate the use of adaptative multigrid minimization algorithms for the estimation of the apparent motion field. The proposed approach provides a coherent and efficient framework for estimating piecewise smooth flow fields for different parameterizations relative to adaptative partitions of the image. The performances of the resulting algorithms are demonstrated in the difficult context of a non convex global energy formulation.

  2. Scanning laser optical tomography resolves structural plasticity during regeneration in an insect brain.

    Directory of Open Access Journals (Sweden)

    René Eickhoff

    Full Text Available BACKGROUND: Optical Projection Tomography (OPT is a microscopic technique that generates three dimensional images from whole mount samples the size of which exceeds the maximum focal depth of confocal laser scanning microscopes. As an advancement of conventional emission-OPT, Scanning Laser Optical Tomography (SLOTy allows simultaneous detection of fluorescence and absorbance with high sensitivity. In the present study, we employ SLOTy in a paradigm of brain plasticity in an insect model system. METHODOLOGY: We visualize and quantify volumetric changes in sensory information procession centers in the adult locust, Locusta migratoria. Olfactory receptor neurons, which project from the antenna into the brain, are axotomized by crushing the antennal nerve or ablating the entire antenna. We follow the resulting degeneration and regeneration in the olfactory centers (antennal lobes and mushroom bodies by measuring their size in reconstructed SLOTy images with respect to the untreated control side. Within three weeks post treatment antennal lobes with ablated antennae lose as much as 60% of their initial volume. In contrast, antennal lobes with crushed antennal nerves initially shrink as well, but regain size back to normal within three weeks. The combined application of transmission-and fluorescence projections of Neurobiotin labeled axotomized fibers confirms that recovery of normal size is restored by regenerated afferents. Remarkably, SLOTy images reveal that degeneration of olfactory receptor axons has a trans-synaptic effect on second order brain centers and leads to size reduction of the mushroom body calyx. CONCLUSIONS: This study demonstrates that SLOTy is a suitable method for rapid screening of volumetric plasticity in insect brains and suggests its application also to vertebrate preparations.

  3. Combining supine MRI and 3D optical scanning for improved surgical planning of breast conserving surgeries

    Science.gov (United States)

    Pallone, Matthew J.; Poplack, Steven P.; Barth, Richard J., Jr.; Paulsen, Keith D.

    2012-02-01

    Image-guided wire localization is the current standard of care for the excision of non-palpable carcinomas during breast conserving surgeries (BCS). The efficacy of this technique depends upon the accuracy of wire placement, maintenance of the fixed wire position (despite patient movement), and the surgeon's understanding of the spatial relationship between the wire and tumor. Notably, breast shape can vary significantly between the imaging and surgical positions. Despite this method of localization, re-excision is needed in approximately 30% of patients due to the proximity of cancer to the specimen margins. These limitations make wire localization an inefficient and imprecise procedure. Alternatively, we investigate a method of image registration and finite element (FE) deformation which correlates preoperative supine MRIs with 3D optical scans of the breast surface. MRI of the breast can accurately define the extents of very small cancers. Furthermore, supine breast MR reduces the amount of tissue deformation between the imaging and surgical positions. At the time of surgery, the surface contour of the breast may be imaged using a handheld 3D laser scanner. With the MR images segmented by tissue type, the two scans are approximately registered using fiducial markers present in both acquisitions. The segmented MRI breast volume is then deformed to match the optical surface using a FE mechanical model of breast tissue. The resulting images provide the surgeon with 3D views and measurements of the tumor shape, volume, and position within the breast as it appears during surgery which may improve surgical guidance and obviate the need for wire localization.

  4. Signal of microstrip scanning near-field optical microscope in far- and near-field zones.

    Science.gov (United States)

    Morozov, Yevhenii M; Lapchuk, Anatoliy S

    2016-05-01

    An analytical model of interference between an electromagnetic field of fundamental quasi-TM(EH)00-mode and an electromagnetic field of background radiation at the apex of a near-field probe based on an optical plasmon microstrip line (microstrip probe) has been proposed. The condition of the occurrence of electromagnetic energy reverse flux at the apex of the microstrip probe was obtained. It has been shown that the nature of the interference depends on the length of the probe. Numerical simulation of the sample scanning process was conducted in illumination-reflection and illumination-collection modes. Results of numerical simulation have shown that interference affects the scanning signal in both modes. However, in illumination-collection mode (pure near-field mode), the signal shape and its polarity are practically insensible to probe length change; only signal amplitude (contrast) is slightly changed. However, changing the probe length strongly affects the signal amplitude and shape in the illumination-reflection mode (the signal formed in the far-field zone). Thus, we can conclude that even small background radiation can significantly influence the signal in the far-field zone and has practically no influence on a pure near-field signal. PMID:27140358

  5. Sensorless adaptive optics and the effect of field of view in biological second harmonic generation microscopy

    Science.gov (United States)

    Vandendriessche, Stefaan; Vanbel, Maarten K.; Verbiest, Thierry

    2014-05-01

    In light of the population aging in many developed countries, there is a great economical interest in improving the speed and cost-efficiency of healthcare. Clinical diagnosis tools are key to these improvements, with biophotonics providing a means to achieve them. Standard optical microscopy of in vitro biological samples has been an important diagnosis tool since the invention of the microscope, with well known resolution limits. Nonlinear optical imaging improves on the resolution limits of linear microscopy, while providing higher contrast images and a greater penetration depth due to the red-shifted incident light compared to standard optical microscopy. It also provides information on molecular orientation and chirality. Adaptive optics can improve the quality of nonlinear optical images. We analyzed the effect of sensorless adaptive optics on the quality of the nonlinear optical images of biological samples. We demonstrate that care needs to be taken when using a large field of view. Our findings provide information on how to improve the quality of nonlinear optical imaging, and can be generalized to other in vitro biological samples. The image quality improvements achieved by adaptive optics should help speed up clinical diagnostics in vitro, while increasing their accuracy and helping decrease detection limits. The same principles apply to in vivo biological samples, and in the future it may be possible to extend these findings to other nonlinear optical effects used in biological imaging.

  6. Scan-based volume animation driven by locally adaptive articulated registrations.

    Science.gov (United States)

    Rhee, Taehyun; Lewis, J P; Neumann, Ulrich; Nayak, Krishna S

    2011-03-01

    This paper describes a complete system to create anatomically accurate example-based volume deformation and animation of articulated body regions, starting from multiple in vivo volume scans of a specific individual. In order to solve the correspondence problem across volume scans, a template volume is registered to each sample. The wide range of pose variations is first approximated by volume blend deformation (VBD), providing proper initialization of the articulated subject in different poses. A novel registration method is presented to efficiently reduce the computation cost while avoiding strong local minima inherent in complex articulated body volume registration. The algorithm highly constrains the degrees of freedom and search space involved in the nonlinear optimization, using hierarchical volume structures and locally constrained deformation based on the biharmonic clamped spline. Our registration step establishes a correspondence across scans, allowing a data-driven deformation approach in the volume domain. The results provide an occlusion-free person-specific 3D human body model, asymptotically accurate inner tissue deformations, and realistic volume animation of articulated movements driven by standard joint control estimated from the actual skeleton. Our approach also addresses the practical issues arising in using scans from living subjects. The robustness of our algorithms is tested by their applications on the hand, probably the most complex articulated region in the body, and the knee, a frequent subject area for medical imaging due to injuries.

  7. Investigation of Two-Dimensional Transition Metal Dichalcogenides by Optical and Scanning Tunneling Spectroscopy

    Science.gov (United States)

    Rigosi, Albert F.

    The goal of this dissertation is not only to present works completed and projects initiated and accomplished, but to also attempt to teach some of the material to readers who have limited exposure to condensed matter. I will offer an introduction to two-dimensional transition metal dichalcogenide materials (2D TMDCs) and the mathematics required to understand the research conducted. Some effort will be given on explaining the experimental setups and preparations. Projects that required elaborate sample fabrication and the yielded results will be summarized. These results have heavy implications for the science behind bound electron-hole pairs, the effects of magnetic fields on such pairs, and extracting the useful optical properties from the material systems in which these pairs reside. Specialized fabrication techniques of samples for longer term projects that I led will also be presented, namely those of constructing heterostructures by stacking various 2D TMDCs for exploring the modulated properties of these novel arrangements. The latter portion of this dissertation will cover the nanoscopic dynamics of TMDC heterostructures. The Kramers-Kronig relations will be derived and discussed in detail. Data and results regarding the electronic structure of these materials, their heterostructures, and their custom alloys measured via scanning tunneling microscopy will be presented. Coupled with the measured optical properties, significant numerical quantities that characterize these materials are extracted. There will be several appendices that offer some supplementary information and basic summaries about all the projects that were initiated.

  8. An evaluation of a combined scanning probe and optical microscope for lunar regolith studies

    Science.gov (United States)

    Yang, S.; Pike, W. T.; Staufer, U.; Claus, D.; Rodenburg, J. M.

    2011-12-01

    The microscopic properties of the lunar regolith such as the shape, the surface texture and the size distribution are required for an understanding of both past surface processes and potential hazards for future human exploration [1]. To reveal the particle morphology at the sub micrometer scale, scanning-probe microscopy (SPM), first used on the 2008 Phoenix mission [1], is a proven approach; however, there are two main challenges for the measurement of lunar particles. Firstly, the SPM tip is liable to move particles during scanning, even when using the lower contact forces of the dynamic-mode imaging. Hence the particles need to be stabilised during imaging. Secondly, typically the AFM tip extends about 10 μm from its cantilever, so larger particles protruding more than this height above their substrates cannot be scanned completely. To immobilize particles and eliminate large particles during SPM scanning, micromachined Si substrates, which have been successfully applied in the Phoenix project for Mars investigation in 2008 [2], have been investigated for lunar analogue material. On these substrates micrometer pits are patterned and serve as traps to enhance the stability of the AFM scanning by grasping the particles. In addition, the diameter of pits can determine the size of dusts to be captured and reduce the adhesion for the larger dust and so eliminate the oversized particles. To extend the imaging range and assist in selecting scan areas for the SPM, we use a type of lensless optical imaging (LOM) which uses ptychographic diffractive imaging [3] to eliminate the restrictions and performance limitations of conventional focusing devices. As a reference, scanning electron microscopy (SEM) which minimizes particle-probe interactions and has the advantage of an extended depth of field, is employed to image the same particle fields at resolutions covering both the SPM and LOM. By comparing the differences and the similarities between SEM and LOM images, the

  9. Sensitivity calibration procedures in optical-CT scanning of BANG 3 polymer gel dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y.; Wuu, Cheng-Shie; Maryanski, Marek J. [Department of Radiation Oncology, Columbia University, New York, New York 10032 (United States); Department of Radiation Oncology, Columbia University, New York, New York 10032 and MGS Research Inc., Madison, Connecticut 06443 (United States)

    2010-02-15

    The dose response of the BANG 3 polymer gel dosimeter (MGS Research Inc., Madison, CT) was studied using the OCTOPUS laser CT scanner (MGS Research Inc., Madison, CT). Six 17 cm diameter and 12 cm high Barex cylinders, and 18 small glass vials were used to house the gel. The gel phantoms were irradiated with 6 and 10 MV photons, as well as 12 and 16 MeV electrons using a Varian Clinac 2100EX. Three calibration methods were used to obtain the dose response curves: (a) Optical density measurements on the 18 glass vials irradiated with graded doses from 0 to 4 Gy using 6 or 10 MV large field irradiations; (b) optical-CT scanning of Barex cylinders irradiated with graded doses (0.5, 1, 1.5, and 2 Gy) from four adjacent 4x4 cm{sup 2} photon fields or 6x6 cm{sup 2} electron fields; and (c) percent depth dose (PDD) comparison of optical-CT scans with ion chamber measurements for 6x6 cm{sup 2}, 12 and 16 MeV electron fields. The dose response of the BANG 3 gel was found to be linear and energy independent within the uncertainties of the experimental methods (about 3%). The slopes of the linearly fitted dose response curves (dose sensitivities) from the four field irradiations (0.0752{+-}3%, 0.0756{+-}3%, 0.0767{+-}3%, and 0.0759{+-}3% cm{sup -1} Gy{sup -1}) and the PDD matching methods (0.0768{+-}3% and 0.0761{+-}3% cm{sup -1} Gy{sup -1}) agree within 2.2%, indicating a good reproducibility of the gel dose response within phantoms of the same geometry. The dose sensitivities from the glass vial approach are different from those of the cylindrical Barex phantoms by more than 30%, owing probably to the difference in temperature inside the two types of phantoms during gel formation and irradiation, and possible oxygen contamination of the glass vial walls. The dose response curve obtained from the PDD matching approach with 16 MeV electron field was used to calibrate the gel phantom irradiated with the 12 MeV, 6x6 cm{sup 2} electron field. Three-dimensional dose distributions

  10. Three-dimensional dosimetry of small megavoltage radiation fields using radiochromic gels and optical CT scanning

    Energy Technology Data Exchange (ETDEWEB)

    Babic, Steven; Battista, Jerry; Jordan, Kevin [Department of Physics and Engineering, London Regional Cancer Program at London Health Sciences Centre, 790 Commissioners Road East, London, Ontario N6 A 4L6 (Canada); McNiven, Andrea [Princess Margret Hospital/University Health Network, Toronto, Ontario (Canada)], E-mail: steven.babic@lhsc.on.ca

    2009-04-21

    The dosimetry of small fields as used in stereotactic radiotherapy, radiosurgery and intensity-modulated radiation therapy can be challenging and inaccurate due to partial volume averaging effects and possible disruption of charged particle equilibrium. Consequently, there exists a need for an integrating, tissue equivalent dosimeter with high spatial resolution to avoid perturbing the radiation beam and artificially broadening the measured beam penumbra. In this work, radiochromic ferrous xylenol-orange (FX) and leuco crystal violet (LCV) micelle gels were used to measure relative dose factors (RDFs), percent depth dose profiles and relative lateral beam profiles of 6 MV x-ray pencil beams of diameter 28.1, 9.8 and 4.9 mm. The pencil beams were produced via stereotactic collimators mounted on a Varian 2100 EX linear accelerator. The gels were read using optical computed tomography (CT). Data sets were compared quantitatively with dosimetric measurements made with radiographic (Kodak EDR2) and radiochromic (GAFChromic (registered) EBT) film, respectively. Using a fast cone-beam optical CT scanner (Vista(TM)), corrections for diffusion in the FX gel data yielded RDFs that were comparable to those obtained by minimally diffusing LCV gels. Considering EBT film-measured RDF data as reference, cone-beam CT-scanned LCV gel data, corrected for scattered stray light, were found to be in agreement within 0.5% and -0.6% for the 9.8 and 4.9 mm diameter fields, respectively. The validity of the scattered stray light correction was confirmed by general agreement with RDF data obtained from the same LCV gel read out with a laser CT scanner that is less prone to the acceptance of scattered stray light. Percent depth dose profiles and lateral beam profiles were found to agree within experimental error for the FX gel (corrected for diffusion), LCV gel (corrected for scattered stray light), and EBT and EDR2 films. The results from this study reveal that a three-dimensional dosimetry

  11. Three-dimensional dosimetry of small megavoltage radiation fields using radiochromic gels and optical CT scanning

    Science.gov (United States)

    Babic, Steven; McNiven, Andrea; Battista, Jerry; Jordan, Kevin

    2009-04-01

    The dosimetry of small fields as used in stereotactic radiotherapy, radiosurgery and intensity-modulated radiation therapy can be challenging and inaccurate due to partial volume averaging effects and possible disruption of charged particle equilibrium. Consequently, there exists a need for an integrating, tissue equivalent dosimeter with high spatial resolution to avoid perturbing the radiation beam and artificially broadening the measured beam penumbra. In this work, radiochromic ferrous xylenol-orange (FX) and leuco crystal violet (LCV) micelle gels were used to measure relative dose factors (RDFs), percent depth dose profiles and relative lateral beam profiles of 6 MV x-ray pencil beams of diameter 28.1, 9.8 and 4.9 mm. The pencil beams were produced via stereotactic collimators mounted on a Varian 2100 EX linear accelerator. The gels were read using optical computed tomography (CT). Data sets were compared quantitatively with dosimetric measurements made with radiographic (Kodak EDR2) and radiochromic (GAFChromic® EBT) film, respectively. Using a fast cone-beam optical CT scanner (Vista™), corrections for diffusion in the FX gel data yielded RDFs that were comparable to those obtained by minimally diffusing LCV gels. Considering EBT film-measured RDF data as reference, cone-beam CT-scanned LCV gel data, corrected for scattered stray light, were found to be in agreement within 0.5% and -0.6% for the 9.8 and 4.9 mm diameter fields, respectively. The validity of the scattered stray light correction was confirmed by general agreement with RDF data obtained from the same LCV gel read out with a laser CT scanner that is less prone to the acceptance of scattered stray light. Percent depth dose profiles and lateral beam profiles were found to agree within experimental error for the FX gel (corrected for diffusion), LCV gel (corrected for scattered stray light), and EBT and EDR2 films. The results from this study reveal that a three-dimensional dosimetry method

  12. Nonlinear optical properties of carboxymethyl starch nanocomposite by Z-scan technique using a Nd-YAG laser

    Science.gov (United States)

    Naderali, R.; Jafari, A.; Motiei, H.

    2015-09-01

    In this paper, the third-order nonlinear optical properties of modified nanocomposite carboxymethyl starch are presented. The nanocomposite of carboxymethyl starch has been synthesized by a chemical technique. X-ray diffraction and scanning electron microscopy were used to study its crystal structure. Linear optical response of this sample was studied by using UV-Visible spectroscopy. Nonlinear refraction and absorption coefficients of the nanocomposite were measured in two different solvents, dimethylformamide and N-methylpyrrolidone, by Z-scan method using a continuous wave Nd-YAG laser at 532 nm. The measured values of nonlinear refraction in both of the solutions were from the order of.

  13. Adaptive Optical Phase Estimation Using Time-Symmetric Quantum Smoothing

    CERN Document Server

    Wheatley, T A; Yonezawa, H; Nakane, D; Arao, H; Pope, D T; Ralph, T C; Wiseman, H M; Furusawa, A; Huntington, E H

    2009-01-01

    Quantum parameter estimation has many applications, from gravitational wave detection to quantum key distribution. We present the first experimental demonstration of the time-symmetric technique of quantum smoothing. We consider both adaptive and non-adaptive quantum smoothing, and show that both are better than their well-known time-asymmetric counterparts (quantum filtering). For the problem of estimating a stochastically varying phase shift on a coherent beam, our theory predicts that adaptive quantum smoothing (the best scheme) gives an estimate with a mean-square error up to $2\\sqrt{2}$ times smaller than that from non-adaptive quantum filtering (the standard quantum limit). The experimentally measured improvement is $2.24 \\pm 0.14$.

  14. Faraday-effect light-valve arrays for adaptive optical instruments

    Energy Technology Data Exchange (ETDEWEB)

    Hirleman, E.D.; Dellenback, P.A.

    1987-01-01

    The ability to adapt to a range of measurement conditions by autonomously configuring software or hardware on-line will be an important attribute of next-generation intelligent sensors. This paper reviews the characteristics of spatial light modulators (SLM) with an emphasis on potential integration into adaptive optical instruments. The paper focuses on one type of SLM, a magneto-optic device based on the Faraday effect. Finally, the integration of the Faraday-effect SLM into a laser-diffraction particle-sizing instrument giving it some ability to adapt to the measurement context is discussed.

  15. A fully automatic framework for cell segmentation on non-confocal adaptive optics images

    Science.gov (United States)

    Liu, Jianfei; Dubra, Alfredo; Tam, Johnny

    2016-03-01

    By the time most retinal diseases are diagnosed, macroscopic irreversible cellular loss has already occurred. Earlier detection of subtle structural changes at the single photoreceptor level is now possible, using the adaptive optics scanning light ophthalmoscope (AOSLO). This work aims to develop a fully automatic segmentation framework to extract cell boundaries from non-confocal split-detection AOSLO images of the cone photoreceptor mosaic in the living human eye. Significant challenges include anisotropy, heterogeneous cell regions arising from shading effects, and low contrast between cells and background. To overcome these challenges, we propose the use of: 1) multi-scale Hessian response to detect heterogeneous cell regions, 2) convex hulls to create boundary templates, and 3) circularlyconstrained geodesic active contours to refine cell boundaries. We acquired images from three healthy subjects at eccentric retinal regions and manually contoured cells to generate ground-truth for evaluating segmentation accuracy. Dice coefficient, relative absolute area difference, and average contour distance were 82±2%, 11±6%, and 2.0±0.2 pixels (Mean±SD), respectively. We find that strong shading effects from vessels are a main factor that causes cell oversegmentation and false segmentation of non-cell regions. Our segmentation algorithm can automatically and accurately segment photoreceptor cells on non-confocal AOSLO images, which is the first step in longitudinal tracking of cellular changes in the individual eye over the time course of disease progression.

  16. Principle of adaptive optical current transducer on independent variables and its test

    Institute of Scientific and Technical Information of China (English)

    LU Zhong-feng; GUO Zhi-zhong

    2008-01-01

    In order to improve the measurement precision of the optical current transducer (OCT), the adaptive optical transducing principle on independent variables is presented in this paper. And one of the adaptive opti-cal current transducer(AOCT) on the independent variables of the output of the electricmegnet current trans-ducer is introduced. According to IEC660044-8, the performance of AOCT was examined roundly applying the standard testing system authenticated by the state authority. The results indicate that the measurement precision of the AOCT has already reached 0.2 class under the temperature from -40℃ to 60℃,which proves the feasi-bility of the method.

  17. Adaptive image content-based exposure control for scanning applications in radiography

    NARCIS (Netherlands)

    H. Schulerud; J. Thielemann; T. Kirkhus; K. Kaspersen; J.M. Østby; M.G. Metaxas; G.J. Royle; J. Griffiths; E. Cook; C. Esbrand; S. Pani; C. Venanzi; P.F. van der Stelt; G. Li; R. Turchetta; A. Fant; S. Theodoridis; H. Georgiou; G. Hall; M. Noy; J. Jones; J. Leaver; F. Triantis; A. Asimidis; N. Manthos; R. Longo; A. Bergamaschi; R.D. Speller

    2007-01-01

    I-ImaS (Intelligent Imaging Sensors) is a European project which has designed and developed a new adaptive X-ray imaging system using on-line exposure control, to create locally optimized images. The I-ImaS system allows for real-time image analysis during acquisition, thus enabling real-time exposu

  18. Imaging human retinal pigment epithelium cells using adaptive optics optical coherence tomography

    Science.gov (United States)

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2016-03-01

    Retinal pigment epithelium (RPE) cells are vital to health of the outer retina, but are often compromised in ageing and major ocular diseases that lead to blindness. Early manifestation of RPE disruption occurs at the cellular level, and while biomarkers at this scale hold considerable promise, RPE cells have proven extremely challenging to image in the living human eye. We present a novel method based on optical coherence tomography (OCT) equipped with adaptive optics (AO) that overcomes the associated technical obstacles. The method takes advantage of the 3D resolution of AO-OCT, but more critically sub-cellular segmentation and registration that permit organelle motility to be used as a novel contrast mechanism. With this method, we successfully visualized RPE cells and characterized their 3D reflectance profile in every subject and retinal location (3° and 7° temporal to the fovea) imaged to date. We have quantified RPE packing geometry in terms of cell density, cone-to-RPE ratio, and number of nearest neighbors using Voronoi and power spectra analyses. RPE cell density (cells/mm2) showed no significant difference between 3° (4,892+/-691) and 7° (4,780+/-354). In contrast, cone-to- RPE ratio was significantly higher at 3° (3.88+/-0.52:1) than 7° (2.31+/- 0.23:1). Voronoi analysis also showed most RPE cells have six nearest neighbors, which was significantly larger than the next two most prevalent associations: five and seven. Averaged across the five subjects, prevalence of cells with six neighbors was 51.4+/-3.58% at 3°, and 54.58+/-3.01% at 7°. These results are consistent with histology and in vivo studies using other imaging modalities.

  19. High-Resolution Adaptive Optics Test-Bed for Vision Science

    Energy Technology Data Exchange (ETDEWEB)

    Wilks, S C; Thomspon, C A; Olivier, S S; Bauman, B J; Barnes, T; Werner, J S

    2001-09-27

    We discuss the design and implementation of a low-cost, high-resolution adaptive optics test-bed for vision research. It is well known that high-order aberrations in the human eye reduce optical resolution and limit visual acuity. However, the effects of aberration-free eyesight on vision are only now beginning to be studied using adaptive optics to sense and correct the aberrations in the eye. We are developing a high-resolution adaptive optics system for this purpose using a Hamamatsu Parallel Aligned Nematic Liquid Crystal Spatial Light Modulator. Phase-wrapping is used to extend the effective stroke of the device, and the wavefront sensing and wavefront correction are done at different wavelengths. Issues associated with these techniques will be discussed.

  20. High-sensitivity piezoelectric tube sensor for shear-force detection in scanning near-field optical microscopy

    Science.gov (United States)

    Lindfors, K.; Kapulainen, M.; Ryytty, P.; Kaivola, M.

    2004-11-01

    An easy-to-implement non-optical shear-force detection setup for tip-sample distance regulation in scanning near-field optical microscopy is demonstrated. The detection method is based on attaching the near-field probe to a piezoelectric tube resulting in excellent mechanical contact between tip and detector. The main advantages of the method are good signal-to-background contrast and thus potential for high sensitivity. The method is demonstrated by obtaining approach curves of silicon surfaces. The suitability for optical experiments is further shown by measuring the near-field intensity distribution of the emission of a semiconductor laser.

  1. Magnetic smart material application to adaptive x-ray optics

    Science.gov (United States)

    Ulmer, M. P.; Graham, Michael E.; Vaynman, Semyon; Cao, J.; Takacs, Peter Z.

    2010-09-01

    We discuss a technique of shape modification that can be applied to thin walled ({100-400 micron thickness) electroformed replicated optics or slumped glass optics to improve the near net shape of the mirror as well as the midfrequency ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a permanently magnetic material. The MSM material exhibits strains about 400 times stronger than ordinary ferromagnetic materials. The deformation process involves a magnetic write head which traverses the surface, and under the guidance of active metrology feedback, locally magnetizes the surface to impart strain where needed. Designs and basic concepts as applied to space borne X-ray optics will be described.

  2. Direct characterization of ultraviolet-light-induced refractive index structures by scanning near-field optical microscopy

    DEFF Research Database (Denmark)

    Svalgaard, Mikael; Madsen, S.; Hvam, Jørn Märcher;

    1998-01-01

    We have applied a reflection scanning near-field optical microscope to directly probe ultraviolet (UV)-light-induced refractive index structures in planar glass samples. This technique permits direct comparison between topography and refractive index changes (10(-5)-10(-3)) with submicrometer...

  3. Scanning near-field optical microscopy on rough surfaces: applications in chemistry, biology, and medicine

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Shear-force apertureless scanning near-field optical microscopy (SNOM with very sharp uncoated tapered waveguides relies on the unexpected enhancement of reflection in the shear-force gap. It is the technique for obtaining chemical (materials contrast in the optical image of “real world” surfaces that are rough and very rough without topographical artifacts, and it is by far less complicated than other SNOM techniques that can only be used for very flat surfaces. The experimental use of the new photophysical effect is described. The applications of the new technique are manifold. Important mechanistic questions in solid-state chemistry (oxidation, diazotization, photodimerization, surface hydration, hydrolysis are answered with respect to simultaneous AFM (atomic force microscopy and detailed crystal packing. Prehistoric petrified bacteria and concomitant pyrite inclusions are also investigated with local RAMAN SNOM. Polymer beads and unstained biological objects (rabbit heart, shrimp eye allow for nanoscopic analysis of cell organelles. Similarly, human teeth and a cancerous tissue are analyzed. Bladder cancer tissue is clearly differentiated from healthy tissue without staining and this opens a new highly promising diagnostic tool for precancer diagnosis. Industrial applications are demonstrated at the corrosion behavior of dental alloys (withdrawal of a widely used alloy, harmless substitutes, improvement of paper glazing, behavior of blood bags upon storage, quality assessment of metal particle preparations for surface enhanced RAMAN spectroscopy, and determination of diffusion coefficient and light fastness in textile fiber dyeing. The latter applications include fluorescence SNOM. Local fluorescence SNOM is also used in the study of partly aggregating dye nanoparticles within resin/varnish preparations. Unexpected new insights are obtained in all of the various fields that cannot be obtained by other techniques.

  4. Packetisation in Optical Packet Switch Fabrics using adaptive timeout values

    DEFF Research Database (Denmark)

    Mortensen, Brian Bach

    2006-01-01

    either because the timer reaches a specific timeout value, or because the optical packet is completely filled with segments. Only two distinct values of the timeout value are used. Which of the two timeout values to use, is selected by 3 different control thresholds. The first threshold level applies to...... the inter arrival rate at the individual VOQs. The remaining thresholds applies to the optical slot level inter arrival rate at the input and output line cards. If any measurements are beyond a given threshold, the higher timeout value is used. The proposed method can be used to make a trade...

  5. Quality evaluation of adaptive optical image based on DCT and Rényi entropy

    Science.gov (United States)

    Xu, Yuannan; Li, Junwei; Wang, Jing; Deng, Rong; Dong, Yanbing

    2015-04-01

    The adaptive optical telescopes play a more and more important role in the detection system on the ground, and the adaptive optical images are so many that we need find a suitable method of quality evaluation to choose good quality images automatically in order to save human power. It is well known that the adaptive optical images are no-reference images. In this paper, a new logarithmic evaluation method based on the use of the discrete cosine transform(DCT) and Rényi entropy for the adaptive optical images is proposed. Through the DCT using one or two dimension window, the statistical property of Rényi entropy for images is studied. The different directional Rényi entropy maps of an input image containing different information content are obtained. The mean values of different directional Rényi entropy maps are calculated. For image quality evaluation, the different directional Rényi entropy and its standard deviation corresponding to region of interest is selected as an indicator for the anisotropy of the images. The standard deviation of different directional Rényi entropy is obtained as the quality evaluation value for adaptive optical image. Experimental results show the proposed method that the sorting quality matches well with the visual inspection.

  6. Parallel-mode scanning optical sectioning using digital Fresnel holography with three-wave interference phase-shifting.

    Science.gov (United States)

    Kelner, Roy; Rosen, Joseph

    2016-02-01

    The Fresnel incoherent correlation holography (FINCH) method is applicable to various techniques of imaging, including fluorescence microscopy. Recently, a FINCH configuration capable of optical sectioning, using a scanning phase pinhole, has been suggested [Optica 1, 70 (2014)]. This capability is highly important in situations that demand the suppression of out-of-focus information from the hologram reconstruction of a specific plane of interest, such as the imaging of thick samples in biology. In this study, parallel-mode scanning using multiple phase pinholes is suggested as a means to shorten the acquisition time in an optical sectioning FINCH configuration. The parallel-mode scanning is enabled through a phase-shifting procedure that extracts the mixed term of two out of three interfering beams.

  7. Scanning electron microscopy of Antarctophthirus microchir (Phthiraptera: Anoplura: Echinophthiriidae): studying morphological adaptations to aquatic life.

    Science.gov (United States)

    Leonardi, María Soledad; Crespo, Enrique A; Raga, Juan Antonio; Fernández, Mercedes

    2012-09-01

    The members of the Family Echinophthiriidae (Phthiraptera: Anoplura) are unique among insects because they infest hosts with an amphibious lifestyle. During their evolution they developed morphological traits that are reflected in unique features. The SEM is a helpful tool to analyze them. Knowing in detail the external structure of these lice is the first step to understand the whole process that derived from the co-adaptation of lice and pinnipeds to the marine environment. For the first time, we studied the external structure of all stages of an echinophthiriid louse. The results are discussed in the light of their evolutionary, functional, and ecological implications. PMID:22503484

  8. Adaptive Optics for EUV Lithography: Phase Retrieval for Wavefront Metrology

    NARCIS (Netherlands)

    Polo, A.

    2014-01-01

    In the semiconductor industry, optical lithography is presently the most widespread technology used to print a geometrical pattern on a semiconductor wafer. Because of the plans imposed by the International Technology Roadmap for Semiconductors (ITRS) for more powerful and smaller chips, new printin

  9. Feasibility of fiber optic displacement sensor scanning system for imaging of dental cavity

    Science.gov (United States)

    Rahman, Husna Abdul; Che Ani, Adi Izhar; Harun, Sulaiman Wadi; Yasin, Moh.; Apsari, Retna; Ahmad, Harith

    2012-07-01

    The purpose of this study is to investigate the potential of intensity modulated fiber optic displacement sensor scanning system for the imaging of dental cavity. Here, we discuss our preliminary results in the imaging of cavities on various teeth surfaces, as well as measurement of the diameter of the cavities which are represented by drilled holes on the teeth surfaces. Based on the analysis of displacement measurement, the sensitivities and linear range for the molar, canine, hybrid composite resin, and acrylic surfaces are obtained at 0.09667 mV/mm and 0.45 mm 0.775 mV/mm and 0.4 mm 0.5109 mV/mm and 0.5 mm and 0.25 mV/mm and 0.5 mm, respectively, with a good linearity of more than 99%. The results also show a clear distinction between the cavity and surrounding tooth region. The stability, simplicity of design, and low cost of fabrication make it suitable for restorative dentistry.

  10. Development of a scanning nearfield optical microscope for low-temperature investigations of semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hodeck, Kai Friedrich

    2009-02-19

    In the present work the electronic structure of MOCVD-grown InGaAs/GaAs and InAs/GaAs quantum dots which are characterized by a particularly low ground state transition energy, was investigated using Scanning Nearfield Optical Microscopy (SNOM). The pivotal question of the presented investigations is, which influence the interaction of the confined carriers has on the energy states of the biexcitons and the multiexcitons in a quantum dot. Therefore, photoluminescence spectra of single quantum dots were investigated under varying excitation intensity at different temperatures between 5 K and 300 K. The construction of a novel scanning nearfield microscope especially for low temperatures allowed the investigation of single quantum dots. Due to significant improvements of the positioning technology and the shear-force distance control between the sample and the nearfield probe a stable scanning of the quantum dot samples at 5 K could be demonstrated, showing a lateral optical resolution of 200 nm. This way, in the photoluminescence spectroscopy of single quantum dots the thermal linewidth broadening of the detected light was reduced down to a value of less than 1 meV, which allowed the identification of the transitions of biexcitons and multiexcitons. On the basis of the performed measurements, for the InGaAs/GaAs quantum dots a biexciton state was identified, with variable binding energies of 2-7 meV. Furthermore, a positively charged trion state with a binding energy of 11 meV was observed, showing high emission intensity, which can be assigned to the sample doping. Accordingly, for the positively charged biexciton state a binding energy of 11 meV can be announced. For the investigated InAs/GaAs quantum dots a biexciton state with binding energies of 3-4 meV was found. Some of the investigated InAs/GaAs quantum dots showed the formation of positively charged states, in particular of a trion state with a binding energy of 3 meV, and of the positively charged

  11. The experiment to detect equivalent optical path difference in independent double aperture interference light path based on step scanning method

    Science.gov (United States)

    Wang, Chaoyan; Chen, Xin-yang; Zheng, Lixin; Ding, Yuanyuan

    2014-11-01

    Fringe test is the method which can detect the relative optical path difference in optical synthetic aperture telescope array. To get to the interference fringes, the two beams of light in the meeting point must be within the coherence length. Step scanning method is within its coherence length, selecting a specific step, changing one-way's optical path of both by changing position of micro displacement actuator. At the same time, every fringe pattern can be recorded. The process of fringe patterns is from appearing to clear to disappearing. Firstly, a particular pixel is selected. Then, we keep tract of the intensity of every picture in the same position. From the intensity change, the best position of relative optical path difference can be made sure. The best position of relative optical path difference is also the position of the clearest fringe. The wavelength of the infrared source is 1290nm and the bandwidth is 63.6nm. In this experiment, the coherence length of infrared source is detected by cube reflection experiment. The coherence length is 30μm by data collection and data processing, and that result of 30μm is less different from the 26μm of theoretical calculated. In order to further test the relative optical path of optical synthetic aperture using step scanning method, the infrared source is placed into optical route of optical synthesis aperture telescope double aperture. The precision position of actuator can be obtained when the fringe is the clearest. By the experiment, we found that the actuating step affects the degree of precision of equivalent optical path. The smaller step size, the more accurate position. But the smaller the step length, means that more steps within the coherence length measurement and the longer time.

  12. A scanning probe-based pick-and-place procedure for assembly of integrated quantum optical hybrid devices

    CERN Document Server

    Schell, Andreas W; Schröder, Tim; Wolters, Janik; Aichele, Thomas; Benson, Oliver

    2011-01-01

    Integrated quantum optical hybrid devices consist of fundamental constituents such as single emitters and tailored photonic nanostructures. A reliable fabrication method requires the controlled deposition of active nanoparticles on arbitrary nanostructures with highest precision. Here, we describe an easily adaptable technique that employs picking and placing of nanoparticles with an atomic force microscope combined with a confocal setup. In this way, both the topography and the optical response can be monitored simultaneously before and after the assembly. The technique can be applied to arbitrary particles. Here, we focus on nanodiamonds containing single nitrogen vacancy centers, which are particularly interesting for quantum optical experiments on the single photon and single emitter level.

  13. Development of a scalable generic platform for adaptive optics real time control

    CERN Document Server

    Surendran, Avinash; Ramaprakash, A N; Parihar, Padmakar

    2015-01-01

    The main objective of the present project is to explore the viability of an adaptive optics control system based exclusively on Field Programmable Gate Arrays (FPGAs), making strong use of their parallel processing capability. In an Adaptive Optics (AO) system, the generation of the Deformable Mirror (DM) control voltages from the Wavefront Sensor (WFS) measurements is usually through the multiplication of the wavefront slopes with a predetermined reconstructor matrix. The ability to access several hundred hard multipliers and memories concurrently in an FPGA allows performance far beyond that of a modern CPU or GPU for tasks with a well defined structure such as Adaptive Optics control. The target of the current project is to generate a signal for a real time wavefront correction, from the signals coming from a Wavefront Sensor, wherein the system would be flexible to accommodate all the current Wavefront Sensing techniques and also the different methods which are used for wavefront compensation. The system ...

  14. Local optical absorption spectra of h-BN–MoS2 van der Waals heterostructure revealed by scanning near-field optical microscopy

    Science.gov (United States)

    Nozaki, Junji; Kobayashi, Yu; Miyata, Yasumitsu; Maniwa, Yutaka; Watanabe, Kenji; Taniguchi, Takashi; Yanagi, Kazuhiro

    2016-06-01

    Van der Waals (vdW) heterostructures, in which different two-dimensional layered materials are stacked, can exhibit unprecedented optical properties. Development of a technique to clarify local optical properties of vdW heterostructures is of great importance for the correct understanding of their backgrounds. Here, we examined local optical absorption spectra of h-BN–MoS2 vdW heterostructures by scanning near-field microscopy measurements with a spatial resolution of 100 nm. In an as-grown sample, there was almost no site dependence of their optical absorption spectra. However, in a degraded sample where defects and deformations were artificially induced, a significant site-dependence of optical absorption spectra was observed.

  15. Whole-Genome Scans Provide Evidence of Adaptive Evolution in Malawian Plasmodium falciparum Isolates

    DEFF Research Database (Denmark)

    Ocholla, Harold; Preston, Mark D; Mipando, Mwapatsa;

    2014-01-01

    BACKGROUND:  Selection by host immunity and antimalarial drugs has driven extensive adaptive evolution in Plasmodium falciparum and continues to produce ever-changing landscapes of genetic variation. METHODS:  We performed whole-genome sequencing of 69 P. falciparum isolates from Malawi and used...... population genetics approaches to investigate genetic diversity and population structure and identify loci under selection. RESULTS:  High genetic diversity (π = 2.4 × 10(-4)), moderately high multiplicity of infection (2.7), and low linkage disequilibrium (500-bp) were observed in Chikhwawa District, Malawi......, an area of high malaria transmission. Allele frequency-based tests provided evidence of recent population growth in Malawi and detected potential targets of host immunity and candidate vaccine antigens. Comparison of the sequence variation between isolates from Malawi and those from 5 geographically...

  16. An adaptive optics approach for laser beam correction in turbulence utilizing a modified plenoptic camera

    Science.gov (United States)

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2015-09-01

    Adaptive optics has been widely used in the field of astronomy to correct for atmospheric turbulence while viewing images of celestial bodies. The slightly distorted incoming wavefronts are typically sensed with a Shack-Hartmann sensor and then corrected with a deformable mirror. Although this approach has proven to be effective for astronomical purposes, a new approach must be developed when correcting for the deep turbulence experienced in ground to ground based optical systems. We propose the use of a modified plenoptic camera as a wavefront sensor capable of accurately representing an incoming wavefront that has been significantly distorted by strong turbulence conditions (C2n distortions. After the large distortions have been corrected, a secondary mode utilizing more traditional adaptive optics algorithms can take over to fine tune the wavefront correction. This two-stage algorithm can find use in free space optical communication systems, in directed energy applications, as well as for image correction purposes.

  17. Fixation light hue bias revisited: implications for using adaptive optics to study color vision.

    Science.gov (United States)

    Hofer, H J; Blaschke, J; Patolia, J; Koenig, D E

    2012-03-01

    Current vision science adaptive optics systems use near infrared wavefront sensor 'beacons' that appear as red spots in the visual field. Colored fixation targets are known to influence the perceived color of macroscopic visual stimuli (Jameson, D., & Hurvich, L. M. (1967). Fixation-light bias: An unwanted by-product of fixation control. Vision Research, 7, 805-809.), suggesting that the wavefront sensor beacon may also influence perceived color for stimuli displayed with adaptive optics. Despite its importance for proper interpretation of adaptive optics experiments on the fine scale interaction of the retinal mosaic and spatial and color vision, this potential bias has not yet been quantified or addressed. Here we measure the impact of the wavefront sensor beacon on color appearance for dim, monochromatic point sources in five subjects. The presence of the beacon altered color reports both when used as a fixation target as well as when displaced in the visual field with a chromatically neutral fixation target. This influence must be taken into account when interpreting previous experiments and new methods of adaptive correction should be used in future experiments using adaptive optics to study color.

  18. AVES-IMCO: an adaptive optics visible spectrograph and imager/coronograph for NAOS

    Science.gov (United States)

    Beuzit, Jean-Luc; Lagrange, A.-M.; Mouillet, D.; Chauvin, G.; Stadler, E.; Charton, J.; Lacombe, F.; AVES-IMCO Team

    2001-05-01

    The NAOS adaptive optics system will very soon provide diffraction-limited images on the VLT, down to the visible wavelengths (0.020 arcseconds at 0.83 micron for instance). At the moment, the only instrument dedicated to NAOS is the CONICA spectro-imager, operating in the near-infrared from 1 to 5 microns. We are now proposing to ESO, in collaboration with an Italian group, the development of a visible spectrograph/imager/coronograph, AVES-IMCO (Adaptive Optics Visual Echelle Spectrograph and IMager/COronograph). We present here the general concept of the new instrument as well as its expected performances in the different modes.

  19. Adaptive Optics Concept For Multi-Objects 3D Spectroscopy on ELTs

    CERN Document Server

    Neichel, B; Puech, M; Conan, J M; Lelouarn, M; Gendron, E; Hammer, F; Rousset, G; Jagourel, P; Bouchet, P

    2005-01-01

    In this paper, we present a first comparison of different Adaptive Optics (AO) concepts to reach a given scientific specification for 3D spectroscopy on Extremely Large Telescope (ELT). We consider that a range of 30%-50% of Ensquarred Energy (EE) in H band (1.65um) and in an aperture size from 25 to 100mas is representative of the scientific requirements. From these preliminary choices, different kinds of AO concepts are investigated : Ground Layer Adaptive Optics (GLAO), Multi-Object AO (MOAO) and Laser Guide Stars AO (LGS). Using Fourier based simulations we study the performance of these AO systems depending on the telescope diameter.

  20. Interferometric adaptive optics for high-power laser beam correction in fast ignition experiments

    Energy Technology Data Exchange (ETDEWEB)

    Homoelle, D; Baker, K L; Patel, P K; Utterback, E; Rushford, M C; Siders, C W; Barty, C P J, E-mail: homoelle1@llnl.go [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)

    2010-08-01

    We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32x32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from {approx}75{mu}rad to <2{mu}rad.

  1. Interferometric adaptive optics for high-power laser beam correction in fast ignition experiments

    Science.gov (United States)

    Homoelle, D.; Baker, K. L.; Patel, P. K.; Utterback, E.; Rushford, M. C.; Siders, C. W.; Barty, C. P. J.

    2010-08-01

    We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32×32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from ~75μrad to <2μrad.

  2. An adaptive optics approach to the reduction of misalignments and beam jitters in gravitational wave interferometers

    International Nuclear Information System (INIS)

    We describe a study and the preliminary experimental results on the possibility of using adaptive optics systems for the reduction of geometrical fluctuations of input laser beams in long baseline interferometric detectors of gravitational waves. The experimental tests aimed to test the efficiency of Hermite-Gauss versus Shack-Hartmann wavefront reconstruction and feedback diagonalization. These preliminary results seem to indicate that the adaptive optics systems may be integrated in the near future as stabilization stages before a passive mode cleaner cavity, provided that the operational band of the mirror is increased together with the efficiency of the control system

  3. Investigation of Power8 processors for astronomical adaptive optics real-time control

    CERN Document Server

    Basden, Alastair

    2015-01-01

    The forthcoming Extremely Large Telescopes all require adaptive optics systems for their successful operation. The real-time control for these systems becomes computationally challenging, in part limited by the memory bandwidths required for wavefront reconstruction. We investigate new POWER8 processor technologies applied to the problem of real-time control for adaptive optics. These processors have a large memory bandwidth, and we show that they are suitable for operation of first-light ELT instrumentation, and propose some potential real-time control system designs. A CPU-based real-time control system significantly reduces complexity, improves maintainability, and leads to increased longevity for the real-time control system.

  4. Axial range of conjugate adaptive optics in two-photon microscopy

    CERN Document Server

    Paudel, Hari P; Mertz, Jerome; Bifano, Thomas

    2015-01-01

    We describe an adaptive optics technique for two-photon microscopy in which the deformable mirror used for aberration compensation is positioned in a plane conjugate to the plane of the aberration. We demonstrate in a proof-of-principle experiment that this technique yields a large field of view advantage in comparison to standard pupil-conjugate adaptive optics. Further, we show that the extended field of view in conjugate AO is maintained over a relatively large axial translation of the deformable mirror with respect to the conjugate plane. We conclude with a discussion of limitations and prospects for the conjugate AO technique in two-photon biological microscopy.

  5. Interferometric adaptive optics for high-power laser beam correction in fast ignition experiments

    Energy Technology Data Exchange (ETDEWEB)

    Homoelle, D C; Baker, K L; Patel, P K; Utterback, E; Rushford, M C; Siders, C W; Barty, C J

    2009-10-22

    We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32 x 32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from {approx}75{micro}rad to <2{micro}rad.

  6. Towards feasible and effective predictive wavefront control for adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L A; Veran, J

    2008-06-04

    We have recently proposed Predictive Fourier Control, a computationally efficient and adaptive algorithm for predictive wavefront control that assumes frozen flow turbulence. We summarize refinements to the state-space model that allow operation with arbitrary computational delays and reduce the computational cost of solving for new control. We present initial atmospheric characterization using observations with Gemini North's Altair AO system. These observations, taken over 1 year, indicate that frozen flow is exists, contains substantial power, and is strongly detected 94% of the time.

  7. High-speed polarization sensitive optical coherence tomography scan engine based on Fourier domain mode locked laser

    OpenAIRE

    Bonesi, Marco; Sattmann, Harald; Torzicky, Teresa; Zotter, Stefan; Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Eigenwillig, Christoph; Wieser, Wolfgang; Huber, Robert; Hitzenberger, Christoph K.

    2012-01-01

    We report on a new swept source polarization sensitive optical coherence tomography scan engine that is based on polarization maintaining (PM) fiber technology. The light source is a Fourier domain mode locked laser with a PM cavity that operates in the 1300 nm wavelength regime. It is equipped with a PM buffer stage that doubles the fundamental sweep frequency of 54.5 kHz. The fiberization allows coupling of the scan engine to different delivery probes. In a first demonstration, we use the s...

  8. Influence of the probe-sample interaction on scanning near-field optical microscopic images in the far field

    Institute of Scientific and Technical Information of China (English)

    Li Zhi; Zhang Jia-Sen; Yang Jing; Gong Qi-Huang

    2006-01-01

    We have studied the influence of probe-sample interaction in a scanning near-field optical microscopy (SNOM) in the far field by using samples with a step structure. For a sample with a step height of ~λ/4, the SNOM image contrast between the two sides of the step changes periodically at different scan heights. For a step height of ~λ/2, the image contrast remains approximately the same. The probe-sample interaction determines the SNOM image contrast here. The influence of different refractive indices of the sample has been also analysed by using a simple theoretical model.

  9. IN VITRO ANALYSIS OF MARGINAL ADAPTATION AND RESISTANCE OF DIFFERENT DENTAL COMPOSITES: STEREO AND SCANNING ELECTRON MICROSCOPIC EVALUATION.

    Science.gov (United States)

    Pilolli, G P; Lauritano, D; Lucchese, A; Di Stasio, D; Petruzzi, M; Marrone, G; Serpico, R; Favia, G

    2015-01-01

    To compare the performance, by scanning electron microscopic analysis, of the interface between tooth and four commercial restorative composite resins in Class I cavities following exposure to acidified artificial solution, pH 4.5, with a background electrolyte composition similar to saliva, 600 teeth were divided into 4 groups. The first group was treated with microfilled light-cured Heliomolar; the second group with Durafill; the third group with the microfilled self-cured Isomolar; and the fourth group was treated using the hybrid self-cured Miradapt. All teeth of each group were randomly divided into two sub-groups: A) a control group that was immersed in artificial saliva (pH 7); B) a study group that was immersed in artificial saliva acidified with phosphoric acid (pH 4.5) in order to obtain artificial caries. The samples were examined by scanning electron microscopy. Data were analyzed using Pearson’s Chi-squared test (χ2) with R statistical software. The statistical analyses demonstrated significant differences in the two sub-groups A and B when considered for the light-cured composites whereas no difference was monitored for self-cured composites. Statistical analysis (p minore di 0.001) also demonstrated that the type of composite strongly influenced the infiltration grade. Our results demonstrate that incremental layering techniques might improve the marginal adaptation for light-cured composites, while self-cured show a marked polymerization contraction which can cause marginal breakdown.

  10. Adaptive spectral window sizes for extraction of diagnostic features from optical spectra

    Science.gov (United States)

    Kan, Chih-Wen; Lee, Andy Y.; Nieman, Linda T.; Sokolov, Konstantin; Markey, Mia K.

    2010-07-01

    We present an approach to adaptively adjust the spectral window sizes for optical spectra feature extraction. Previous studies extracted features from spectral windows of a fixed width. In our algorithm, piecewise linear regression is used to adaptively adjust the window sizes to find the maximum window size with reasonable linear fit with the spectrum. This adaptive windowing technique ensures the signal linearity in defined windows; hence, the adaptive windowing technique retains more diagnostic information while using fewer windows. This method was tested on a data set of diffuse reflectance spectra of oral mucosa lesions. Eight features were extracted from each window. We performed classifications using linear discriminant analysis with cross-validation. Using windowing techniques results in better classification performance than not using windowing. The area under the receiver-operating-characteristics curve for windowing techniques was greater than a nonwindowing technique for both normal versus mild dysplasia (MD) plus severe high-grade dysplasia or carcinama (SD) (MD+SD) and benign versus MD+SD. Although adaptive and fixed-size windowing perform similarly, adaptive windowing utilizes significantly fewer windows than fixed-size windows (number of windows per spectrum: 8 versus 16). Because adaptive windows retain most diagnostic information while reducing the number of windows needed for feature extraction, our results suggest that it isolates unique diagnostic features in optical spectra.

  11. Push-pull membrane mirrors for adaptive optics.

    Science.gov (United States)

    Bonora, Stefano; Poletto, Luca

    2006-12-11

    We propose an improvement to the electrostatic membrane deformable mirror technique introducing push-pull capability that increases the performance in the correction of optical aberrations. The push-pull effect is achieved by the addition of some transparent electrodes on the top of the device. The transparent electrode is an indium-tin-oxide coated glass. The improvement of the mirror in generating surfaces is demonstrated by the comparison with a pull membrane mirror. The control is carried out in open loop by the knowledge of the response of each single electrode. An effective iterative strategy for the clipping management is presented. The performances are evaluated both in terms of Zernike polynomials generation and in terms of aberrations compensation based on the statistics of human eyes.

  12. Push-pull membrane mirrors for adaptive optics

    Science.gov (United States)

    Bonora, Stefano; Poletto, Luca

    2006-12-01

    We propose an improvement to the electrostatic membrane deformable mirror technique introducing push-pull capability that increases the performance in the correction of optical aberrations. The push-pull effect is achieved by the addition of some transparent electrodes on the top of the device. The transparent electrode is an indium-tin-oxide coated glass. The improvement of the mirror in generating surfaces is demonstrated by the comparison with a pull membrane mirror. The control is carried out in open loop by the knowledge of the response of each single electrode. An effective iterative strategy for the clipping management is presented. The performances are evaluated both in terms of Zernike polynomials generation and in terms of aberrations compensation based on the statistics of human eyes.

  13. Axial-Stereo 3-D Optical Metrology for Inner Profile of Pipes Using a Scanning Laser Endoscope

    Science.gov (United States)

    Gong, Yuanzheng; Johnston, Richard S.; Melville, C. David; Seibel, Eric J.

    2015-07-01

    As the rapid progress in the development of optoelectronic components and computational power, 3-D optical metrology becomes more and more popular in manufacturing and quality control due to its flexibility and high speed. However, most of the optical metrology methods are limited to external surfaces. This article proposed a new approach to measure tiny internal 3-D surfaces with a scanning fiber endoscope and axial-stereo vision algorithm. A dense, accurate point cloud of internally machined threads was generated to compare with its corresponding X-ray 3-D data as ground truth, and the quantification was analyzed by Iterative Closest Points algorithm.

  14. Femtosecond THz time domain spectroscopy at 36 kHz scan rate using an acousto-optic delay

    CERN Document Server

    Urbanek, B; Eisele, M; Baierl, S; Kaplan, D; Lange, C; Huber, R

    2016-01-01

    We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4 ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of $1.7 \\times 10^5/\\sqrt{\\rm Hz}$. Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of $10\\,\\rm nm/\\sqrt{\\rm Hz}$. The compact, all-optical design ensures alignment-free operation even in harsh environments.

  15. Femtosecond terahertz time-domain spectroscopy at 36 kHz scan rate using an acousto-optic delay

    Science.gov (United States)

    Urbanek, B.; Möller, M.; Eisele, M.; Baierl, S.; Kaplan, D.; Lange, C.; Huber, R.

    2016-03-01

    We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4-ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of 1.7 × 105 / √{ H z } . Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of 10 nm/ √{ H z } . The compact, all-optical design ensures alignment-free operation even in harsh environments.

  16. Extracting hysteresis from nonlinear measurement of wavefront-sensorless adaptive optics system

    NARCIS (Netherlands)

    Song, H.; Vdovin, G.; Fraanje, R.; Schitter, G.; Verhaegen, M.

    2008-01-01

    In many scientific and medical applications wavefront-sensorless adaptive optics (AO) systems are used to correct the wavefront aberration by optimizing a certain target parameter, which is nonlinear with respect to the control signal to the deformable mirror (DM). Hysteresis is the most common nonl

  17. Using 50-mm electrostatic membrane deformable mirror in astronomical adaptive optics

    NARCIS (Netherlands)

    Tokovinin, A.; Thomas, S.; Vdovin, G.

    2004-01-01

    Membrane micro-machined deformable mirrors (MMDM) feature low cost, low power consumption, small size and absence of hysteresis. Interested in using such a device for the adaptive optics system at the SOAR 4.1-m telescope, we evaluated the performance of a 79-channel 50-mm (pupil size 35mm) MMDM fro

  18. Placing Limits on Extragalactic Substructure with Gravitational Lenses and Adaptive Optics

    NARCIS (Netherlands)

    Lagattuta, David J.; Vegetti, S.; Auger, M. W.; Fassnacht, C. D.; Koopmans, L. V. E.; McKean, J. P.

    2011-01-01

    We present the first results from a systematic search for extragalactic substructure, using high resolution Adaptive Optics (AO) images of known strong gravitational lenses. In particular we focus on two lens systems, B0128+437 and B1939+666, placing limits on both luminous and dark matter substruct

  19. Adaptive PMD Compensation in 10 Gbit/s RZ Optical Communication System

    Institute of Scientific and Technical Information of China (English)

    Yu; Li; Zhang; Xiaoguang; Zhou; Guangtao; Shen; Yu; Zheng; Yuan; Li; Chaoyang; Liu; Yumin; Chen; Lin; Yang; Bojun

    2003-01-01

    We report an experiment of adaptive compensation for polarization mode dispersion (PMD) in 10Gbit/s return zero (RZ) optical communication system. The quasi-real-time PMD compensation is realized. The algorithm so-called particle swarm optimization (PSO) is used to control feedback compensation system.

  20. Development of an ultra-lightweight scanning mirror for the optical imager of the second generation METEOSAT (MSG)

    Science.gov (United States)

    Harnisch, Bernd; Pradier, A.; Deyerler, Michael; Kunkel, Bernd P.; Papenburg, U.

    1994-09-01

    A new material designated C/SiC is the basis for a current ultra-lightweight scan mirror (ULSM) ESA/ESTEC technology development contract for the METEOSAT Second Generation (MSG) Program (Ref. {1}). It consists of random- oriented carbon fibers as 'greenbody' which is shaped to the designed configuration, and is infiltrated in the liquid phase with Si resulting in a SiC enriched surface layer, with a CVD grown SiC optical polishing layer. The reflective coating finally is silver under a dedicated protection layer. The requirements for this mirror are rather stringent: during 7 years in a geostationary orbit of life it will permantly be exposed to centrifugal forces induced by the satellite spinning at 100 rpm. Due to high image quality requirements for the imager - designated SEVIRI (Spinning Enhanced Visible IR Imager) - the MTF degradation caused by the scan mirror alone are defined to EQ 3%, resulting in rather high surface quality requirements. The main contribution is the spin induced mirror tip deflection which turned out to be the design driver. The technologically most challenging requirement is to develop a scan mirror with 800 X 500 mm(superscript 2) effective aperture and a central cutout - the telescope is a Gregory concept - to withstand tight environmental requirements at a mass which was specified as coating will be rendered to ESA. Since this contract is a technology contract, applications beyond the MSG scan mirror are borne in mind, including higher optical surface qualities such as (lambda) /30 or curved surfaces, also aspheric mirrors of possibly even larger diameters. The manufacturing and optical process implement subcontractors which are not listed among the authors, i.e. SGL Carbon/Meitingen, FRG, for the Si infiltration; Schunk Kohlenstofftechnik/GieBen, FRG, for the CVD SiC coating; REOSC Optique, Ballainvilliers, France for the optical polishing, and Jenoptik, Jena, FRG, for the silver and protection coating.

  1. Optical techniques: using coarse and detailed scans for the preventive acquisition of fingerprints with chromatic white-light sensors

    Science.gov (United States)

    Hildebrandt, Mario; Dittmann, Jana; Vielhauer, Claus; Leich, Marcus

    2011-11-01

    The preventive application of automated latent fingerprint acquisition devices can enhance the Homeland Defence, e.g. by improving the border security. Here, contact-less optical acquisition techniques for the capture of traces are subject to research; chromatic white light sensors allow for multi-mode operation using coarse or detailed scans. The presence of potential fingerprints could be detected using fast coarse scans. Those Regions-of- Interest can be acquired afterwards with high-resolution detailed scans to allow for a verification or identification of individuals. An acquisition and analysis of fingerprint traces on different objects that are imported or pass borders might be a great enhancement for security. Additionally, if suspicious objects require a further investigation, an initial securing of potential fingerprints could be very useful. In this paper we show current research results for the coarse detection of fingerprints to prepare the detailed acquisition from various surface materials that are relevant for preventive applications.

  2. Adaptive optics imaging of the outer retinal tubules in Bietti's crystalline dystrophy.

    Science.gov (United States)

    Battu, R; Akkali, M C; Bhanushali, D; Srinivasan, P; Shetty, R; Berendschot, T T J M; Schouten, J S A G; Webers, C A

    2016-05-01

    PurposeTo study the outer retinal tubules using spectral domain optical coherence tomography and adaptive optics and in patients with Bietti's crystalline dystrophy.MethodsTen eyes of five subjects from five independent families with Bietti's crystalline Dystrophy (BCD) were characterized with best-corrected visual acuity (BCVA), full-field electroretinography, and fundus autofluorescence (FAF). High-resolution images were obtained with the spectral domain optical coherence tomography (SD-OCT) and adaptive optics (AO).ResultsSD-OCT showed prominent outer retinal layer loss and outer retinal tubulations at the margin of outer retinal loss. AO images displayed prominent macrotubules and microtubules with characteristic features in eight out of the 10 eyes. Crystals were present in all ten eyes. There was a reduction in the cone count in all eyes in the area outside the outer retinal tubules (ORT).ConclusionsThis study describes the morphology of the outer retinal tubules when imaged enface on the adaptive optics in patients with BCD. These findings provide insight into the macular structure of these patients. This may have prognostic implications and refine the study on the pathogenesis of BCD.

  3. Adaptive optics in spinning disk microscopy: improved contrast and brightness by a simple and fast method.

    Science.gov (United States)

    Fraisier, V; Clouvel, G; Jasaitis, A; Dimitrov, A; Piolot, T; Salamero, J

    2015-09-01

    Multiconfocal microscopy gives a good compromise between fast imaging and reasonable resolution. However, the low intensity of live fluorescent emitters is a major limitation to this technique. Aberrations induced by the optical setup, especially the mismatch of the refractive index and the biological sample itself, distort the point spread function and further reduce the amount of detected photons. Altogether, this leads to impaired image quality, preventing accurate analysis of molecular processes in biological samples and imaging deep in the sample. The amount of detected fluorescence can be improved with adaptive optics. Here, we used a compact adaptive optics module (adaptive optics box for sectioning optical microscopy), which was specifically designed for spinning disk confocal microscopy. The module overcomes undesired anomalies by correcting for most of the aberrations in confocal imaging. Existing aberration detection methods require prior illumination, which bleaches the sample. To avoid multiple exposures of the sample, we established an experimental model describing the depth dependence of major aberrations. This model allows us to correct for those aberrations when performing a z-stack, gradually increasing the amplitude of the correction with depth. It does not require illumination of the sample for aberration detection, thus minimizing photobleaching and phototoxicity. With this model, we improved both signal-to-background ratio and image contrast. Here, we present comparative studies on a variety of biological samples.

  4. A novel data adaptive detection scheme for distributed fiber optic acoustic sensing

    Science.gov (United States)

    Ölçer, Íbrahim; Öncü, Ahmet

    2016-05-01

    We introduce a new approach for distributed fiber optic sensing based on adaptive processing of phase sensitive optical time domain reflectometry (Φ-OTDR) signals. Instead of conventional methods which utilizes frame averaging of detected signal traces, our adaptive algorithm senses a set of noise parameters to enhance the signal-to-noise ratio (SNR) for improved detection performance. This data set is called the secondary data set from which a weight vector for the detection of a signal is computed. The signal presence is sought in the primary data set. This adaptive technique can be used for vibration detection of health monitoring of various civil structures as well as any other dynamic monitoring requirements such as pipeline and perimeter security applications.

  5. Operation of the adaptive optics system at the Large Binocular Telescope Observatory

    Science.gov (United States)

    Miller, Douglas L.; Guerra, Juan Carlos; Boutsia, Konstantina; Fini, Luca; Argomedo, Javier; Biddick, Chris; Agapito, Guido; Arcidiacono, Carmelo; Briguglio, Runa; Brusa, Guido; Busoni, Lorenzo; Esposito, Simone; Hill, John; Kulesa, Craig; McCarthy, Don; Pinna, Enrico; Puglisi, Alfio T.; Quiros-Pacheco, Fernando; Riccardi, Armando; Xompero, Marco

    2012-07-01

    The Adaptive Optics System at the Large Binocular Telescope Observatory consists of two Adaptive Secondary (ASM) mirrors and two Pyramid Wavefront sensors. The first ASM/Pyramid pair has been commissioned and is being used for science operation using the NIR camera PISCES on the right side of the binocular telescope. The left side ASM/Pyramid system is currently being commissioned, with completion scheduled for the Fall of 2012. We will discuss the operation of the first Adaptive Optics System at the LBT Observatory including interactions of the AO system with the telescope and its TCS, observational modes, user interfaces, observational scripting language, time requirement for closed loop and offsets and observing efficiency.

  6. FOCAL PLANE WAVEFRONT SENSING USING RESIDUAL ADAPTIVE OPTICS SPECKLES

    Energy Technology Data Exchange (ETDEWEB)

    Codona, Johanan L.; Kenworthy, Matthew, E-mail: jlcodona@gmail.com [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

    2013-04-20

    Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance the Strehl ratio or suppress the residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphs and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly changing residual atmospheric speckles at the 6.5 m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor measurements are used to estimate the residual wavefront, allowing us to approximately compute the rapidly evolving phase and amplitude of speckle halo. When combined with relatively short, synchronized science camera images, the complex speckle estimates can be used to interferometrically analyze the images, leading to an estimate of the static diffraction halo with NCP effects included. In an operational system, this information could be collected continuously and used to iteratively correct quasi-static NCP errors or suppress imperfect coronagraphic halos.

  7. Focal Plane Wavefront Sensing using Residual Adaptive Optics Speckles

    CERN Document Server

    Codona, Johanan L

    2013-01-01

    Optical imperfections, misalignments, aberrations, and even dust can significantly limit sensitivity in high-contrast imaging systems such as coronagraphs. An upstream deformable mirror (DM) in the pupil can be used to correct or compensate for these flaws, either to enhance Strehl ratio or suppress residual coronagraphic halo. Measurement of the phase and amplitude of the starlight halo at the science camera is essential for determining the DM shape that compensates for any non-common-path (NCP) wavefront errors. Using DM displacement ripples to create a series of probe and anti-halo speckles in the focal plane has been proposed for space-based coronagraphs and successfully demonstrated in the lab. We present the theory and first on-sky demonstration of a technique to measure the complex halo using the rapidly-changing residual atmospheric speckles at the 6.5m MMT telescope using the Clio mid-IR camera. The AO system's wavefront sensor (WFS) measurements are used to estimate the residual wavefront, allowing ...

  8. Investigation of optical nanostructures for photovoltaics with near-field scanning microscopy; Untersuchung optischer Nanostrukturen fuer die Photovoltaik mit Nahfeldmikroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Beckers, Thomas

    2011-09-26

    Textured and rough surfaces are known to increase light trapping in solar cells significantly. The development and optimization of these nano-structures is essential to improve the energy conversion efficiency of thin-film solar cells. In the past, first research approaches covered classical and macroscopic investigations, e.g. determining the haze or angularly resolved scattering. These methods do not provide precise explanation for the optical improvement of the devices, because layer thicknesses and structure sizes in thin-film solar cells are smaller than the wavelength of visible light. The impact of local nano-structures and their contribution to the local absorption enhancement is not resolved by macroscopic measurements. In this thesis, near-field scanning optical microscopy is introduced as first near-field investigations of nano-structures for photovoltaics. This provides an insight into local optical effects for relevant surfaces of photovoltaic devices. Investigating the distribution of the electric fields in layer stacks is crucial to understand the absorption in solar cells. Evanescent fields, which occur due to total internal reflection at the interfaces, are measurable by near-field scanning optical microscopy and yield important information about local light trapping. Within the framework of this thesis, correlations between local surface structures and optical near-field effects are shown. In this case structure features of randomly textured surfaces, which optimize local light trapping, are identified. It paves the way to connect microscopic optical effects on the surface with the macroscopic performance of thin-film solar cells. Moreover, the measurement yields a 3D illustration of the electric field distribution over the sample surface. It is an important criterion to prove the results of rigorous diffraction theory. An excellent agreement between experiment and simulation is found. The simulations provide an insight into the material, which is

  9. A comparative study on the optical limiting properties of different nano spinel ferrites with Z-scan technique

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Jeevan Job; Krishnan, Shiji [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, Kerala 686560 (India); Sridharan, K.; Philip, Reji [Light and Matter Physics Group, Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India); Kalarikkal, Nandakumar, E-mail: nkkalarikkal@mgu.ac.in [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, Kerala 686560 (India); Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala 686560 (India)

    2012-08-15

    Highlights: ► First report in which the optical limiting properties of five different nano spinel ferrites are compared. ► The obtained nonlinearity fits to a two-photon like absorption process. ► Except for NiFe{sub 2}O{sub 4}, the observed nonlinearity has contributions from excited state absorption. ► A size dependent optical limiting response is obtained. ► Among the investigated ferrites, ZnFe{sub 2}O{sub 4} is found to be a better candidate for the optical limiting applications. -- Abstract: We report the optical limiting properties of five different spinel ferrites, NiFe{sub 2}O{sub 4}, Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, ZnFe{sub 2}O{sub 4}, Ni{sub 0.5}Co{sub 0.5}Fe{sub 2}O{sub 4}, and CoFe{sub 2}O{sub 4} with an average particle grain size of 8 nm. The optical limiting properties are investigated using the open aperture Z-scan technique. The obtained nonlinearity fits to a two-photon like absorption process. Except for NiFe{sub 2}O{sub 4}, the observed nonlinearity has contributions from excited state absorption. The optical limiting response is also studied against particle size and the nonlinearity is found to increase with increasing particle size within the range of our investigations. On comparing the optical limiting properties, ZnFe{sub 2}O{sub 4} is found to be a better candidate for the optical limiting applications. To the best of our knowledge, this is the first report where the optical limiting properties of spinel ferrites are compared.

  10. Comparison of Adaptive Optics and Phase-Conjugate Mirrors for Correction of Aberrations in Double-Pass Amplifiers

    Science.gov (United States)

    Jackel, Steven; Moshe, Inon; Lavi, Raphy

    2003-02-01

    Correction of birefringence-induced effects (depolarization and bipolar focusing) were achieved in double-pass amplifiers by use of a Faraday rotator between the laser rod and the retroreflecting optic. A necessary condition was ray retrace. Retrace was limited by imperfect conjugate-beam fidelity and by nonreciprocal refractive indices. We compared various retroreflectors: stimulated-Brillouin-scatter phase-conjugate mirrors (PCMs), PCMs with rod-to-PCM relay imaging (IPCM), IPCMs with astigmatism-correcting adaptive optics, and all-adaptive-optics imaging variable-radius mirrors. Results with flash-lamp-pumped, Nd:Cr:GSGG double-pass amplifiers showed the superiority of adaptive optics over nonlinear optics retroreflectors in terms of maximum average power, improved beam quality, and broader oscillator pulse duration /bandwidth operating range. Hybrid PCM-adaptive optics retroreflectors yielded intermediate power /beam-quality results.

  11. Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics

    Science.gov (United States)

    Dong, Bing; Li, Yan; Han, Xin-li; Hu, Bin

    2016-01-01

    For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10−5 in optimized correction and is 1.427 × 10−5 in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method. PMID:27598161

  12. Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics.

    Science.gov (United States)

    Dong, Bing; Li, Yan; Han, Xin-Li; Hu, Bin

    2016-09-02

    For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10(-5) in optimized correction and is 1.427 × 10(-5) in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method.

  13. Replica calibration artefacts for optical 3D scanning of micro parts

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Carmignato, S.; Cantatore, Angela;

    2009-01-01

    applications to reproduce the geometry of a step artefact, a miniature step gauge, and a curve standard for optical measuring machines. The replica artefacts were calibrated using a tactile coordinate measuring machine and measured on two different optical scanners. Replication quality and applicability...

  14. Scanning electron microscopy analysis of marginal adaptation of composite resines to enamel after using of standard and gradual photopolimerization

    Directory of Open Access Journals (Sweden)

    Dačić Stefan

    2014-01-01

    Full Text Available Introduction. Bonding between composite and hard dental tissue is most commonly assessed by measuring bonding strength or absence of marginal gap along the restoration interface. Marginal index (MI is a significant indicator of the efficiency of the bond between material and dental tissue because it also shows the values of width and length of marginal gap. Objective. The aim of this investigation was to estimate quantitative and qualitative features of the bond between composite resin and enamel and to determine the values of MI in enamel after application of two techniques of photopolymerization with two composite systems. Methods. Forty Class V cavities on extracted teeth were prepared and restored for scanning electron microscope (SEM analysis of composite bonding to enamel. Adhesion to enamel was achieved by Adper Single Bond 2 - ASB (3M ESPE, or by Adper Easy One - AEO (3M ESPE. Photopolymerization of Filtek Ultimate - FU (3M ESPE was performed using constant halogen light (HIP or soft start program (SOF. Results. Quantitative and qualitative analysis, showed better mikromorphological bonding with SOF photopolymerization and ASB/FU composite system. Differences in MI between different photopolymerization techniques (HIP: 0.6707; SOF: 0.2395 were statistically significant (p<0.001, as well as differences between the composite systems (ASB/FU: 0.0470; AEO/ FU: 0.8651 (p<0.001 by two-way ANOVA test. Conclusion. Better marginal adaptation of composite to enamel was obtained with SOF photopolymerization in both composite systems.

  15. Visual Scanning Training, Limb Activation Treatment, and Prism Adaptation for rehabilitating left neglect: Who is the winner?

    Directory of Open Access Journals (Sweden)

    Konstantinos ePriftis

    2013-07-01

    Full Text Available We compared, for the first time, the overall and differential effects of three of the most widely used left neglect (LN treatments: Visual Scanning Training (VST, Limb Activation Treatment (LAT, and Prism Adaptation (PA. Thirty-three LN patients were assigned in quasi-random order to the three groups (VST, LAT, or PA. Each patient received only one type of treatment. LN patients’ performance on everyday life tasks was assessed four times (over a period of six weeks: A1 and A2 (i.e., the two pre-treatment assessments; A3 and A4 (i.e., the two post-treatment assessments. LN patients in each of the three treatment conditions were treated for the same number of sessions (i.e., 20. The results showed that improvements were present in the majority of the tests assessing the peripersonal space in everyday life activities. Our findings were independent of unspecific factors and lasted for at least two weeks following the end of the treatments. There were no interactions, however, between LN treatments and assessments. We suggest that all three treatments can be considered as valid rehabilitation interventions for LN and could be employed for ameliorating LN signs.

  16. Adaptive Bit Rate Video Streaming Through an RF/Free Space Optical Laser Link

    Directory of Open Access Journals (Sweden)

    A. Akbulut

    2010-06-01

    Full Text Available This paper presents a channel-adaptive video streaming scheme which adjusts video bit rate according to channel conditions and transmits video through a hybrid RF/free space optical (FSO laser communication system. The design criteria of the FSO link for video transmission to 2.9 km distance have been given and adaptive bit rate video streaming according to the varying channel state over this link has been studied. It has been shown that the proposed structure is suitable for uninterrupted transmission of videos over the hybrid wireless network with reduced packet delays and losses even when the received power is decreased due to weather conditions.

  17. Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

    Science.gov (United States)

    Keller, Brenton; Cunefare, David; Grewal, Dilraj S.; Mahmoud, Tamer H.; Izatt, Joseph A.; Farsiu, Sina

    2016-07-01

    We introduce a metric in graph search and demonstrate its application for segmenting retinal optical coherence tomography (OCT) images of macular pathology. Our proposed "adjusted mean arc length" (AMAL) metric is an adaptation of the lowest mean arc length search technique for automated OCT segmentation. We compare this method to Dijkstra's shortest path algorithm, which we utilized previously in our popular graph theory and dynamic programming segmentation technique. As an illustrative example, we show that AMAL-based length-adaptive segmentation outperforms the shortest path in delineating the retina/vitreous boundary of patients with full-thickness macular holes when compared with expert manual grading.

  18. Scanned ion beam therapy for prostate carcinoma. Comparison of single plan treatment and daily plan-adapted treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hild, Sebastian [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Department of Biophysics, Darmstadt (Germany); University Clinic Erlangen and Friedrich- Alexander-University Erlangen-Nuernberg (FAU), Department of Radiation Oncology, Erlangen (Germany); Graeff, Christian [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Department of Biophysics, Darmstadt (Germany); Rucinski, Antoni [University Clinic Heidelberg, Heidelberg Ion-Beam Therapy Center (HIT) and Department of Radiation Oncology, Heidelberg (Germany); Sapienza Universit' a di Roma, Dipartimento di Scienze di Base e Applicate per Ingegneria, Roma (Italy); INFN, Roma (Italy); Zink, Klemens [University of Applied Sciences, Institute for Medical Physics and Radiation Protection, Giessen (Germany); University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg (Germany); Habl, Gregor [University Clinic Heidelberg, Heidelberg Ion-Beam Therapy Center (HIT) and Department of Radiation Oncology, Heidelberg (Germany); Klinikum rechts der Isar, Technische Universitaet Muenchen (TUM), Department of Radiation Oncology, Munich (Germany); Durante, Marco [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Department of Biophysics, Darmstadt (Germany); Technische Universitaet Darmstadt, Faculty of Physics, Darmstadt (Germany); Herfarth, Klaus [University Clinic Heidelberg, Heidelberg Ion-Beam Therapy Center (HIT) and Department of Radiation Oncology, Heidelberg (Germany); Bert, Christoph [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Department of Biophysics, Darmstadt (Germany); University Clinic Erlangen and Friedrich- Alexander-University Erlangen-Nuernberg (FAU), Department of Radiation Oncology, Erlangen (Germany); University Hospital Erlangen, Radiation Oncology, Erlangen (Germany)

    2016-02-15

    Intensity-modulated particle therapy (IMPT) for tumors showing interfraction motion is a topic of current research. The purpose of this work is to compare three treatment strategies for IMPT to determine potential advantages and disadvantages of ion prostate cancer therapy. Simulations for three treatment strategies, conventional one-plan radiotherapy (ConvRT), image-guided radiotherapy (IGRT), and online adaptive radiotherapy (ART) were performed employing a dataset of 10 prostate cancer patients with six CT scans taken at one week intervals. The simulation results, using a geometric margin concept (7-2 mm) as well as patient-specific internal target volume definitions for IMPT were analyzed by target coverage and exposure of critical structures on single fraction dose distributions. All strategies led to clinically acceptable target coverage in patients exhibiting small prostate motion (mean displacement < 4 mm), but IGRT and especially ART led to significant sparing of the rectum. In 20 % of the patients, prostate motion exceeded 4 mm causing insufficient target coverage for ConvRT (V95{sub mean} = 0.86, range 0.63-0.99) and IGRT (V95{sub mean} = 0.91, range 0.68-1.00), while ART maintained acceptable target coverage. IMPT of prostate cancer demands consideration of rectal sparing and adaptive treatment replanning for patients exhibiting large prostate motion. (orig.) [German] Adaptive Therapieansaetze fuer sich interfraktionell bewegende Zielvolumina in der intensitaetsmodulierten Partikeltherapie (IMPT) befinden sich zurzeit in der Entwicklung. In dieser Arbeit werden drei Behandlungsstrategien auf moegliche Vor- und Nachteile in der IMPT des Prostatakarzinoms hin untersucht. Auf Basis eines anonymisierten Datensatzes aus 10 Patienten mit Prostatakarzinom wurden die drei Bestrahlungsstrategien, konventionelle Ein-Plan-Strahlentherapie (ConvRT), bildunterstuetzte Strahlentherapie (IGRT) und tagesaktuelle Strahlentherapie (adaptive radiotherapy,ART), simuliert

  19. Adaptation in the optical properties of the crystalline lens in the eyes of the Lessepsian migrant Siganus rivulatus.

    Science.gov (United States)

    Gagnon, Yakir L; Shashar, Nadav; Kröger, Ronald H H

    2011-08-15

    Vision is an important source of information for many animals. The crystalline lens plays a central role in the visual pathway and hence the ecology of fishes. In this study, we tested whether the different light regimes in the Mediterranean and Red Seas have an effect on the optical properties of the lenses in the rivulated rabbitfish, Siganus rivulatus. This species has migrated through the Suez Canal from the Red Sea and established a vital population in the Mediterranean Sea. Longitudinal spherical aberration curves and focal lengths of the fish lenses were measured by laser scans and compared between the two populations. In addition, rivulated rabbitfish from the Mediterranean Sea were exposed to colored light (yellow, green and blue) and unfiltered light for periods of 1 or 13 days to test for short-term adjustments. Lens focal length was significantly longer (3%) in the Rea Sea population. The shorter focal length of the Mediterranean population can be explained as an adaptation to the dimmer light environment, as this difference makes the Mediterranean eyes 5% more sensitive than the eyes of the Red Sea population. The difference may be due to genetic differences or, more likely, adaptive developmental plasticity. Short-term regulatory mechanisms do not seem to be involved.

  20. Thermo-optically driven adaptive mirror based on thermal expansion: preparation and resolution

    Science.gov (United States)

    Reinert, Felix; Lüthy, W.

    2005-12-01

    A thermo-optically driven adaptive mirror is presented. It is based on the thermal expansion of a thin film heated with a light pattern. We describe a procedure for the preparation of a silicon elastomer with a high-quality optical surface. This material, Sylgard 184, has a high linear thermal expansion coefficient of 3.1μ10-4 K-1. Surface modulations are recorded in an interferometer. Modulations of 350 nm result at an intensity of 370 mW/cm2. The resolution is measured with a line pattern. The contrast drops to 30 % at 1.6 line pairs per millimeter (lp/mm).

  1. Experimentally observe the effect of spherical aberration on diffractive intraocular lens using adaptive optics

    Science.gov (United States)

    Guo, Huanqing; DeLestrange, Elie

    2015-03-01

    We first investigated the similarity in optical quality of a batch of diffractive intraocular lenses (DIOLs), providing experimental evidence for one DIOL as representative of a batch. Using adaptive optics, we then evaluated one DIOL under different levels of Zernike spherical aberration (SA) by applying both a point spread function test and a psychophysical visual acuity test. We found that for small aperture size SA has the effect of shifting the through-focus curve of DIOL. Also, for a relatively large aperture size, it has different effects on the distant and near foci.

  2. Nonlinear optical properties of cobalt and iron doped CdSe nanoparticles using Z-scan technique

    Energy Technology Data Exchange (ETDEWEB)

    Gaur, Poonam, E-mail: poonam.gaur612@gmail.com [Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Sonipat 131001, Haryana (India); Malik, B.P. [Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Sonipat 131001, Haryana (India); Gaur, Arun [Department of Physics, Hindu College, Sonipat 131001, Haryana (India)

    2015-01-15

    The present work aims at the synthesis of pure, Cobalt (Co) and Iron (Fe) doped CdSe nanoparticles by the wet chemical method. The optical properties of synthesized nanoparticles have been characterized by X-ray diffraction (XRD), UV–vis spectroscopy to find the optical direct band gap and estimation of particle size by using Debye–Scherrer formula and HRTEM. The nonlinear optical properties such as nonlinear absorption co-efficient, nonlinear refraction co-efficient and third order nonlinear susceptibility χ{sup (3)} are investigated. The calculations have been performed with the help of Z-scan experimental set-up using Nd: YAG laser emitting 532 nm, 5 ns laser pulses with intensity maintained at 2.296 TW/cm{sup 2}. The nanoparticles clearly exhibit a negative value of nonlinear refraction, which is attributed to the two photon absorption and free carrier absorption. Further the optical limiting behavior is determined (figure of merit (FOM)). The presence of RSA in these nanoparticles makes them a potential material for the development of optical limiter.

  3. Investigation of third-order optical nonlinearity in KBe2BO3F2 crystal by Z-scan

    Science.gov (United States)

    Li, F.-Q.; Zong, N.; Zhang, F.-F.; Yang, J.; Yang, F.; Peng, Q.-J.; Cui, D.-F.; Zhang, J.-Y.; Wang, X.-Y.; Chen, C.-T.; Xu, Z.-Y.

    2012-08-01

    The third-order optical nonlinearity of deep-ultraviolet (DUV) nonlinear optical (NLO) crystal KBe2BO3F2 (KBBF) was investigated using single-beam Z-scan technique for the first time. The Z-scans were performed on a c-cut KBBF crystal and a KBBF prism-coupling device (PCD) with picosecond pulses at 355 nm. No two-photon absorption was observed in the experiment. The measured nonlinear refraction index n 2 showed positive signs, indicating self-focusing Kerr effects. The n 2 values were estimated to be (1.75±0.35)×10-15 cm2/W with the c-cut sample and (1.85±0.37)×10-15 cm2/W with the PCD, corresponding to the third-order nonlinear optical susceptibilities χ_{eff}^{(3)} of (0.99±0.20)×10-13 esu and (0.94±0.19)×10-13 esu, respectively. The results are expected to promote the investigation of frequency conversion processes with ultra-short laser in KBBF crystal.

  4. Gemini multi-conjugate adaptive optics system review I: Design, trade-offs and integration

    CERN Document Server

    Rigaut, Francois; Boccas, Maxime; d'Orgeville, Céline; Vidal, Fabrice; van Dam, Marcos A; Arriagada, Gustavo; Fesquet, Vincent; Galvez, Ramon L; Gausachs, Gaston; Cavedoni, Chad; Ebbers, Angelic W; Karewicz, Stan; James, Eric; Lührs, Javier; Montes, Vanessa; Perez, Gabriel; Rambold, William N; Rojas, Roberto; Walker, Shane; Bec, Matthieu; Trancho, Gelys; Sheehan, Michael; Irarrazaval, Benjamin; Boyer, Corinne; Ellerbroek, Brent L; Flicker, Ralf; Gratadour, Damien; Garcia-Rissmann, Aurea; Daruich, Felipe

    2013-01-01

    The Gemini Multi-conjugate adaptive optics System (GeMS) at the Gemini South telescope in Cerro Pach{\\'o}n is the first sodium-based multi-Laser Guide Star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near infrared, with uniform quality over a field of view of two square arcminutes. The present paper (I) is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light.

  5. Experience with wavefront sensor and deformable mirror interfaces for wide-field adaptive optics systems

    CERN Document Server

    Basden, A G; Bharmal, N A; Bitenc, U; Brangier, M; Buey, T; Butterley, T; Cano, D; Chemla, F; Clark, P; Cohen, M; Conan, J -M; de Cos, F J; Dickson, C; Dipper, N A; Dunlop, C N; Feautrier, P; Fusco, T; Gach, J L; Gendron, E; Geng, D; Goodsell, S J; Gratadour, D; Greenaway, A H; Guesalaga, A; Guzman, C D; Henry, D; Holck, D; Hubert, Z; Huet, J M; Kellerer, A; Kulcsar, C; Laporte, P; Roux, B Le; Looker, N; Longmore, A J; Marteaud, M; Martin, O; Meimon, S; Morel, C; Morris, T J; Myers, R M; Osborn, J; Perret, D; Petit, C; Raynaud, H; Reeves, A P; Rousset, G; Lasheras, F Sanchez; Rodriguez, M Sanchez; Santos, J D; Sevin, A; Sivo, G; Stadler, E; Stobie, B; Talbot, G; Todd, S; Vidal, F; Younger, E J

    2016-01-01

    Recent advances in adaptive optics (AO) have led to the implementation of wide field-of-view AO systems. A number of wide-field AO systems are also planned for the forthcoming Extremely Large Telescopes. Such systems have multiple wavefront sensors of different types, and usually multiple deformable mirrors (DMs). Here, we report on our experience integrating cameras and DMs with the real-time control systems of two wide-field AO systems. These are CANARY, which has been operating on-sky since 2010, and DRAGON, which is a laboratory adaptive optics real-time demonstrator instrument. We detail the issues and difficulties that arose, along with the solutions we developed. We also provide recommendations for consideration when developing future wide-field AO systems.

  6. Adaptive optics in multiphoton microscopy: comparison of two, three and four photon fluorescence.

    Science.gov (United States)

    Sinefeld, David; Paudel, Hari P; Ouzounov, Dimitre G; Bifano, Thomas G; Xu, Chris

    2015-11-30

    We demonstrate adaptive optics system based on nonlinear feedback from 3- and 4-photon fluorescence. The system is based on femtosecond pulses created by soliton self-frequency shift of a 1550-nm fiber-based femtosecond laser together with micro-electro-mechanical system (MEMS) phase spatial light modulator (SLM). We perturb the 1020-segment SLM using an orthogonal Walsh sequence basis set with a modified version of three-point phase shifting interferometry. We show the improvement after aberrations correction in 3-photon signal from fluorescent beads. In addition, we compare the improvement obtained in the same adaptive optical system for 2-, 3- and 4-photon fluorescence using dye pool. We show that signal improvement resulting from aberration correction grows exponentially as a function of the order of nonlinearity.

  7. The Robo-AO KOI Survey: laser adaptive optics imaging of every Kepler exoplanet candidate

    CERN Document Server

    Ziegler, Carl; Baranec, Christoph; Morton, Tim; Riddle, Reed; Atkinson, Dani; Nofi, Larissa

    2016-01-01

    The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star (KOI) with laser adaptive optics imaging to hunt for blended nearby stars which may be physically associated companions. With the unparalleled efficiency provided by the first fully robotic adaptive optics system, we perform the critical search for nearby stars (0.15" to 4.0" separation with contrasts up to 6 magnitudes) that dilute the observed planetary transit signal, contributing to inaccurate planetary characteristics or astrophysical false positives. We present 3313 high resolution observations of Kepler planetary hosts from 2012-2015, discovering 479 nearby stars. We measure an overall nearby star probability rate of 14.5\\pm0.8%. With this large data set, we are uniquely able to explore broad correlations between multiple star systems and the properties of the planets which they host, providing insight into the formation and evolution of planetary systems in our galaxy. Several KOIs of particular interest...

  8. Coherent free space optics communications over the maritime atmosphere with use of adaptive optics for beam wavefront correction.

    Science.gov (United States)

    Li, Ming; Cvijetic, Milorad

    2015-02-20

    We evaluate the performance of the coherent free space optics (FSO) employing quadrature array phase-shift keying (QPSK) modulation over the maritime atmosphere with atmospheric turbulence compensated by use of adaptive optics (AO). We have established a comprehensive FSO channel model for maritime conditions and also made a comprehensive comparison of performance between the maritime and terrestrial atmospheric links. The FSO links are modeled based on the intensity attenuation resulting from scattering and absorption effects, the log-amplitude fluctuations, and the phase distortions induced by turbulence. The obtained results show that the FSO system performance measured by the bit-error-rate (BER) can be significantly improved when the optimization of the AO system is achieved. Also, we find that the higher BER is observed in the maritime FSO channel with atmospheric turbulence, as compared to the terrestrial FSO systems if they experience the same turbulence strength.

  9. High dynamic range optical scanning of sediments and rock samples: More than colour?

    Science.gov (United States)

    Klug, Martin; Fabian, Karl; Knies, Jochen

    2015-04-01

    An automated high dynamic range (HDR) scanning procedure for cores and single sediment samples has been developed based on the GeoTek core scanner equipped with a 3* 2048 pixel CCD array GeoScan colour line-scan camera and a Sigma AF 105mm F2.8 EX DG MACRO lens. Repeated colour line scans of the same core sequence using different illumination and exposure time settings, but equal aperture, can be combined into single HDR images. This yields improved colour definition especially if layers of highly variable brightness occur in the same sequence. Colour calibration is performed automatically during image processing based on synchronization of colour charts. Polarized light is used to minimize gloss on wet surfaces. Beyond improved colour detection, high resolution scans with pixel size down to 25 µm provide the possibility of quantifying fabric, texture, and colour contrast between mottle and matrix. We present examples from marine sediments, lake sediments, hard rock cores, and individual soil samples. Due to the high resolution in sediment sequences, the improved images provide important background information to interpret synchronous measurements of density, magnetic susceptibility, or X-ray fluorescence with respect to their respective measurement footprint. If for example an XRF measurement indicates a 2% increase in Fe at a location of a thin black layer of 1/10 of the XRF measurement footprint, within an otherwise homogenous sequence, it can be inferred that the real Fe abundance within the layer is probably 20% higher than in the surrounding sediment. HDR scanning can therefore help to provide high resolution informed interpolation and deconvolution of measurements with larger sensor footprints.

  10. Four-probe scanning tunnelling microscope with atomic resolution for electrical and electro-optical property measurements of nanosystems

    Institute of Scientific and Technical Information of China (English)

    Lin Xiao; He Xiao-Bo; Lu Jun-Ling; Gao Li; Huan Qing; Shi Dong-Xia; Gao Hong-Jun

    2005-01-01

    We demonstrate a special four-probe scanning tunnelling microscope (STM) system in ultrahigh vacuum (UHV),which can provide coarse positioning for every probe independently with the help of scanning electron microscope (SEM)and fine positioning down to nanometre using the STM technology. The system allows conductivity measurement by means of a four-point probe method, which can draw out more accurate electron transport characteristics in nanostructures, and provides easy manipulation of low dimension materials. All measurements can be performed in variable temperature (from 30K to 500K), magnetic field (from 0 to 0.1T), and different gas environments. Simultaneously, the cathodoluminescence (CL) spectrum can be achieved through an optical subsystem. Test measurements using some nanowire samples show that this system is a powerful tool in exploring electron transport characteristics and spectra in nanoscale physics.

  11. An optical scanning system for spectroscopic impurity flux investigations inside the ASDEX tokamak

    International Nuclear Information System (INIS)

    A scanning mirror system was developed to resolve impurity flux sources spatially across about 2/3 of the ASDEX surface by using visible spectroscopy. A totally computer-controlled layout allows wide-range spatial scanning during a discharge. Spectra over a range of ∝ 150 A are recorded with an integration time down to 20 ms. The versatility of this new system is illustrated by means of first observations of ASDEX discharges with additional heating (NI, LH, ICRH) and modulated gas puffing experiments. (orig.)

  12. Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

    NARCIS (Netherlands)

    Martin, S.C.; De Pater, I.; Marcus, P.

    2011-01-01

    We present H-band (1.4–1.8 μm) images of Neptune with a spatial resolution of ∼0.06″, taken with the W.M. Keck II telescope using the slit-viewing camera (SCAM) of the NIRSPEC instrument backed with Adaptive Optics. Images with 60-second integration times span 4 hours each on UT 20 and 21 August, 20

  13. Optical Digital Imitation Painting Design Based on Self-Adaptive Image Feature

    OpenAIRE

    Zhu Liyan; Qin Jianfei; Qu Liyong; Song Shuwei; Xu Weidong

    2016-01-01

    Based on the study of existing digital imitation camouflage technology, we propose a kind of optical digital imitation camouflage design algorithm which is based on the characteristic of self-adaptive image. Picking main color feature of the background by using K-means clustering algorithm, counting the shape characteristics of each main color spots by separating layers, we generated digital camouflage pattern automatically by segmenting the background region characteristics and fill the back...

  14. Registration of adaptive optics corrected retinal nerve fiber layer (RNFL) images

    OpenAIRE

    Ramaswamy, Gomathy; Lombardo, Marco; Devaney, Nicholas

    2014-01-01

    Glaucoma is the leading cause of preventable blindness in the western world. Investigation of high-resolution retinal nerve fiber layer (RNFL) images in patients may lead to new indicators of its onset. Adaptive optics (AO) can provide diffraction-limited images of the retina, providing new opportunities for earlier detection of neuroretinal pathologies. However, precise processing is required to correct for three effects in sequences of AO-assisted, flood-illumination images: uneven illumina...

  15. Ferrofluid Based Deformable Mirrors - a New Approach to Adaptive Optics Using Liquid Mirrors

    OpenAIRE

    Laird, P.; Bergamasco, R.; Berube, V.; Borra, E. F.; Ritcey, A.; Rioux, M.; Robitaille, N.; Thibault, S.; Silva Jr, L. Vieira da; Yockell-Lelievre, H.

    2002-01-01

    The trend towards ever larger telescopes and more advanced adaptive optics systems is driving the need for deformable mirrors with a large number of low cost actuators. Liquid mirrors have long been recognized a potential low cost alternative to conventional solid mirrors. By using a water or oil based ferrofluid we are able to benefit from a stronger magnetic response than is found in magnetic liquid metal amalgams and avoid the difficulty of passing a uniform current through a liquid. Depos...

  16. Adaptive Optics at Optical Wavelengths: Test Observations of Kyoto 3DII Connected to Subaru Telescope AO188

    Science.gov (United States)

    Matsubayashi, K.; Sugai, H.; Shimono, A.; Akita, A.; Hattori, T.; Hayano, Y.; Minowa, Y.; Takeyama, N.

    2016-09-01

    Adaptive optics (AO) enables us to observe objects with high spatial resolution, which is important in most astrophysical observations. Most AO systems are operational at near-infrared wavelengths but not in the optical range, because optical observations require a much higher performance to obtain the same Strehl ratio as near-infrared observations. Therefore, to enable AO-assisted observations at optical wavelengths, we connected the Kyoto Tridimensional Spectrograph II (Kyoto 3DII), which can perform integral field spectroscopy, to the second generation AO system of the Subaru Telescope (AO188). We developed a new beam-splitter that reflects light below 594 nm for the wavefront sensors of AO188 and transmits above 644 nm for Kyoto 3DII. We also developed a Kyoto 3DII mount at the Nasmyth focus of the Subaru Telescope. In test observations, the spatial resolution of the combined AO188–Kyoto 3DII was higher than that in natural seeing conditions, even at 6500 Å. The full width at half maximum of an undersampled (1.5 spaxels) bright guide star (7.0 mag in the V-band) was 0.″12.

  17. Adaptive Optics at Optical Wavelengths: Test Observations of Kyoto 3DII Connected to Subaru Telescope AO188

    Science.gov (United States)

    Matsubayashi, K.; Sugai, H.; Shimono, A.; Akita, A.; Hattori, T.; Hayano, Y.; Minowa, Y.; Takeyama, N.

    2016-09-01

    Adaptive optics (AO) enables us to observe objects with high spatial resolution, which is important in most astrophysical observations. Most AO systems are operational at near-infrared wavelengths but not in the optical range, because optical observations require a much higher performance to obtain the same Strehl ratio as near-infrared observations. Therefore, to enable AO-assisted observations at optical wavelengths, we connected the Kyoto Tridimensional Spectrograph II (Kyoto 3DII), which can perform integral field spectroscopy, to the second generation AO system of the Subaru Telescope (AO188). We developed a new beam-splitter that reflects light below 594 nm for the wavefront sensors of AO188 and transmits above 644 nm for Kyoto 3DII. We also developed a Kyoto 3DII mount at the Nasmyth focus of the Subaru Telescope. In test observations, the spatial resolution of the combined AO188-Kyoto 3DII was higher than that in natural seeing conditions, even at 6500 Å. The full width at half maximum of an undersampled (1.5 spaxels) bright guide star (7.0 mag in the V-band) was 0.″12.

  18. Practical High-Order Adaptive Optics Systems For Extrasolar Planet Searches

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B A; Olivier, S; Bauman, B; Brase, J; Carr, E; Carrano, C J; Gavel, D; Max, C E; Patience, J

    2001-08-29

    Direct detection of photons emitted or reflected by an extrasolar planet is an extremely difficult but extremely exciting application of adaptive optics. Typical contrast levels for an extrasolar planet would be 10{sup 9}-Jupiter is a billion times fainter than the sun. Current adaptive optics systems can only achieve contrast levels of 10{sup 6}, but so-called ''extreme'' adaptive optics systems with 10{sup 4}-10{sup 5} degrees of freedom could potentially detect extrasolar planets. We explore the scaling laws defining the performance of these systems, first set out by Angel (1994), and derive a different definition of an optimal system. Our sensitivity predictions are somewhat more pessimistic than the original paper, due largely to slow decorrelation timescales for some noise sources, though choosing to site an ExAO system at a location with exceptional r{sub 0} (e.g. Mauna Kea) can offset this. We also explore the effects of segment aberrations in a Keck-like telescope on ExAO; although the effects are significant, they can be mitigated through Lyot coronagraphy.

  19. High-resolution Imaging of Living Retina through Optic Adaptive Retinal Imaging System

    Institute of Scientific and Technical Information of China (English)

    Chunhui Jiang; Wenji Wang; Ning Ling; Gezhi Xu; Xuejun Rao; Xinyang Li; Yudong Zhang

    2002-01-01

    Purpose: To evaluate the possibility as well as the usage of adaptive optics in high-resolution retinal imaging.Methods:From March to November 2001, the fundus of 25 adults were checked by using Optic Adaptive Retinal Imaging System (OAS). The age of the subjects varied from 18~48 years. All had normal visual acuity from 0.9 to 1.0. No abnormality was found in the ocular examination, and their medical as well as ocular history was unremarkable. Results: High-resolution images of the retinal cells, photoreceptor and bipolar cell, were analysed. In these images, the cells are clearly resolved. The density of the photoreceptor at area 1.5 degree from the foveloa is around 40 000~50 000/mm2. At area 3 degree, it drops to less than 30 000/mm2.Conclusion:Optic Adaptive Retinal Imaging System (AOS) is able to get high-resolution image of retinal cells in living human eyes. It may be widely used in ophthalmology experimentally and clinically.

  20. MAD Adaptive Optics Imaging of High Luminosity Quasars: A Pilot Project

    CERN Document Server

    Liuzzo, E; Paiano, S; Treves, A; Uslenghi, M; Arcidiacono, C; Baruffolo, A; Diolaiti, E; Farinato, J; Lombini, M; Moretti, A; Ragazzoni, R; Brast, R; Donaldson, R; Kolb, J; Marchetti, E; Tordo, S

    2016-01-01

    We present near-IR images of five luminous quasars at z~2 and one at z~4 obtained with an experimental adaptive optics instrument at the ESO Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these non optimal conditions, the resulting images of point sources have cores of FWHM ~0.2 arcsec. We are able to characterize the host galaxy properties for 2 sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with adaptive optics systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2-3 kpc) quasar host galaxies for QSOs at z = ...

  1. An adaptive extended Kalman filter for fluorescence diffuse optical tomography of tumor pharmacokinetics

    Science.gov (United States)

    Wang, Xin; Wu, Linhui; Yi, Xi; Zhang, Limin; Gao, Feng; Zhao, Huijuan

    2014-03-01

    According to the morphological differences in the vascularization between healthy and diseased tissues, pharmacokinetic-rate images of fluorophore can provide diagnostic information for tumor differentiation, and especially have the potential for staging of tumors. In this paper, fluorescence diffuse optical tomography method is firstly used to acquire metabolism-related time-course images of the fluorophore concentration. Based on a two-compartment model comprised of plasma and extracelluar-extravascular space, we next propose an adaptive-EKF framework to estimate the pharmacokinetic-rate images. With the aid of a forgetting factor, the adaptive-EKF compensate the inaccuracy initial values and emphasize the effect of the current data in order to realize a better online estimation compared with the conventional EKF. We use simulate data to evaluate the performance of the proposed methodology. The results suggest that the adaptive-EKF can obtain preferable pharmacokinetic-rate images than the conventional EKF with higher quantitativeness and noise robustness.

  2. Validation Through Simulations of a Cn2 Profiler for the ESO/VLT Adaptive Optics Facility

    CERN Document Server

    Garcia-Rissmann, A; Kolb, J; Louarn, M Le; Madec, P -Y; Neichel, B

    2015-01-01

    The Adaptive Optics Facility (AOF) project envisages transforming one of the VLT units into an adaptive telescope and providing its ESO (European Southern Observatory) second generation instruments with turbulence corrected wavefronts. For MUSE and HAWK-I this correction will be achieved through the GALACSI and GRAAL AO modules working in conjunction with a 1170 actuators Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). Multiple wavefront sensors will enable GLAO and LTAO capabilities, whose performance can greatly benefit from a knowledge about the stratification of the turbulence in the atmosphere. This work, totally based on end-to-end simulations, describes the validation tests conducted on a Cn2 profiler adapted for the AOF specifications. Because an absolute profile calibration is strongly dependent on a reliable knowledge of turbulence parameters r0 and L0, the tests presented here refer only to normalized output profiles. Uncertainties in the input parameters inherent t...

  3. Generalization of the optical scanning holography%光学扫描全息术的推广

    Institute of Scientific and Technical Information of China (English)

    刘守渔; 梁万国; 谢敬辉; 赵达尊

    2001-01-01

    The optical scanning holography is given as the following: at the recording sta ge, a real time Fresnel Zone Plate (FZP) is used to scan an object to make the i ntensity distribution of the FZP convolute with the intensity transmissivity of the object, then a photodetector detects the convolution and converts it to dig ital data, the holographic information, to be stored in the computer. At the re co nstruction stage, another FZP signal generated by the computer convolutes with t he stored holographic data resulting in the reconstructed information of the obj ect at a particular crosssection corresponding to the parameters of the second F ZP. A generalizing optical scanning holography is proposed, which says that any real-time optical intensity distribution function can be acted as the optical field to scan the object for obtaining the holographie information, if it has t he following characterics:(1) it is the function of x,y, z with circle symme try of z;(2) for a given z, its autocorrelation is a δ function.%给出了光学扫描全息术的基本原理。 记录时用实时FZP与物体强度透射率发生卷积从而产 生扫描全息图;再现时用与记录时相对应的FZP与全息图信号发生卷积即可再现出物体的信 息。 推广了光学扫描全息术,提出只要某一实时的光场强度分布函数具有如下性质:(l)该函数中含有x,y,z参量且相对于z参量具有圆对称性;(2) 对于某一确定的z参量 ,该函数的自相关是δ函数,就可以把该光场作为光学扫描全息术中的照明光场对物体进行扫描记录以得到扫描全息图。

  4. Description of spermatheca and eggs of Eurygaster austriaca (Schrank, 1778) (Heteroptera: Scutelleridae),based on optical and scanning electron microscopy

    OpenAIRE

    CANDAN, Selami; Suludere, Zekiye; GÜLLÜ, Mustafa

    2011-01-01

    Spermatheca and egg morphology of Eurygaster austriaca (Schrank, 1778) were studied by optical and scanning electron microscopy (SEM). The spermatheca of E. austriaca is characterized by a spermathecal bulb, a pumping region, distal and proximal flanges and ducts, and a genital chamber. Each female was shown to deposit 14 green eggs on average in mass. The spherical eggs averaged 1.05 ± 0.05 mm in diameter. The first external evidence of embryonic development was the appearance of 2 red eye s...

  5. A Scanning Multi-Axis Differential Optical Absorption Spectroscopy System for Measurement of Tropospheric NO2 in Beijing

    Institute of Scientific and Technical Information of China (English)

    LI Ang; XIE Pin-Hua; LIU Cheng; LIU Jian-Guo; LIU Wen-Qing

    2007-01-01

    A scanning multi-axis differential optical absorption spectroscopy (DOAS) system is developed for monitoring tropospheric NO2 abundance. Measurements at different viewing angles near the horizon can be performed sequentially with one telescope collecting scattered sunlight reflected by a moving mirror. Tropospheric NO2 diurnal variations can be derived from slant column densities (SCDs) of different elevation angles. The result from a field campaign in Beijing in summer of 2005 reveals potential possibility for the monitoring of tropospheric NO2 by multi-axis DOAS technique.

  6. Ship detection for high resolution optical imagery with adaptive target filter

    Science.gov (United States)

    Ju, Hongbin

    2015-10-01

    Ship detection is important due to both its civil and military use. In this paper, we propose a novel ship detection method, Adaptive Target Filter (ATF), for high resolution optical imagery. The proposed framework can be grouped into two stages, where in the first stage, a test image is densely divided into different detection windows and each window is transformed to a feature vector in its feature space. The Histograms of Oriented Gradients (HOG) is accumulated as a basic feature descriptor. In the second stage, the proposed ATF highlights all the ship regions and suppresses the undesired backgrounds adaptively. Each detection window is assigned a score, which represents the degree of the window belonging to a certain ship category. The ATF can be adaptively obtained by the weighted Logistic Regression (WLR) according to the distribution of backgrounds and targets of the input image. The main innovation of our method is that we only need to collect positive training samples to build the filter, while the negative training samples are adaptively generated by the input image. This is different to other classification method such as Support Vector Machine (SVM) and Logistic Regression (LR), which need to collect both positive and negative training samples. The experimental result on 1-m high resolution optical images shows the proposed method achieves a desired ship detection performance with higher quality and robustness than other methods, e.g., SVM and LR.

  7. Ultrahigh-Resolution Combined Coronal Optical Coherence Tomography Confocal Scanning Ophthalmoscope (OCT/SLO): a pilot study

    International Nuclear Information System (INIS)

    To evaluate clinical images from a prototype ultrahigh resolution (UHR) combined coronal optical coherence tomography/confocal scanning ophthalmoscope (OCT/SLO) and to compare them to standard-resolution OCT/SLO images on the same patients. Cross-sectional pilot-study. Sixty-six eyes of 42 patients with various macular pathologies, such as age-related macular degeneration, macular edema, macular hole, central serous retinopathy, epiretinal membrane and posterior vitreous traction syndrome. Each subject was first scanned with a standard-resolution OCT/SLO that has an axial resolution of ∼ 10 micron. Immediately following, patients were scanned with the prototype UHR OCT/SLO device. The UHR system employs a compact super luminescent diode (SLD) with a 150 nm bandwidth centered at 890 nm, which allows imaging of the retina with an axial resolution of 3 microns. Both coronal and longitudinal OCT scans were acquired with each system, and compared side-by-side. Scan quality was assessed for the observer's ability to visualize the vitreo-retinal interface and retinal layers - in particular of the outer retina/RPE/choroidal interface, increased discrimination of pathological changes, and better signal intensity. Ultrahigh and standard-resolution coronal and longitudinal OCT/SLO images of macular pathologies. In the side-by-side comparison with the commercial standard-resolution OCT/SLO images, the scans in the Ultrahigh resolution OCT/SLO images were superior in 85 % of cases. Relatively poor quality images were attributed to lower signal-to-noise ratio, limited focusing, or media opacities. Several images that had a better signal intensity in the standard-resolution OCT/SLO system were found to show more retinal detail in the UHR system. In general, intraretinal layers in the UHR OCT/SLO images were better delineated in both coronal and longitudinal scans. Enhanced details were also seen in the outer retina/RPE/choroidal complex. The UHR OCT/SLO system produced better

  8. Extending resolution of scanning optical microscopy beyond the Abbe limit through the assistance of InSb thin layers.

    Science.gov (United States)

    Ding, Chenliang; Wei, Jingsong; Li, Qisong; Liang, Xin; Wei, Tao

    2016-04-01

    The resolution of light imaging is required to extend beyond the Abbe limit to the subdiffraction, or even nanoscale. In this Letter, we propose to extend the resolution of scanning optical microscopy (SOM) beyond the Abbe limit as a kind of subdiffraction imaging technology through the assistance of InSb thin layers due to obvious nonlinear saturation absorption and reversible formation of an optical pinhole channel. The results show that the imaging resolution is greatly improved compared with the SOM itself. This work provides a way to improve the resolution of SOM without changing the SOM itself, but through the assistance of InSb thin layers. This is also a simple and practical way to extend the resolution of SOM beyond the Abbe limit.

  9. Design and Development of an Optical Path Difference Scan Mechanism for Fourier Transform Spectrometers using High Displacement RAINBOW Actuators

    Science.gov (United States)

    Wise, Stephanie A.; Hardy, Robin C.; Dausch, David E.

    1997-01-01

    A new piezoelectric drive mechanism has been developed for optical translation in space-based spectrometer systems. The mechanism utilizes a stack of RAINBOW high displacement piezoelectric actuators to move optical components weighing less than 250 grams through a one centimeter travel. The mechanism uses the direct motion of the piezoelectric devices, stacked such that the displacement of the individual RAINBOW actuators is additive. A prototype device has been built which utilizes 21 RAINBOWs to accomplish the necessary travel. The mechanism weighs approximately 0.6 kilograms and uses less than 2 Watts of power at a scanning frequency of 0.5 Hertz, significantly less power than that required by state-of-the-art motor systems.

  10. Transverse Pupil Shifts for Adaptive Optics Non-Common Path Calibration

    Science.gov (United States)

    Bloemhof, Eric E.

    2011-01-01

    A simple new way of obtaining absolute wavefront measurements with a laboratory Fizeau interferometer was recently devised. In that case, the observed wavefront map is the difference of two cavity surfaces, those of the mirror under test and of an unknown reference surface on the Fizeau s transmission flat. The absolute surface of each can be determined by applying standard wavefront reconstruction techniques to two grids of absolute surface height differences of the mirror under test, obtained from pairs of measurements made with slight transverse shifts in X and Y. Adaptive optics systems typically provide an actuated periscope between wavefront sensor (WFS) and commonmode optics, used for lateral registration of deformable mirror (DM) to WFS. This periscope permits independent adjustment of either pupil or focal spot incident on the WFS. It would be used to give the required lateral pupil motion between common and non-common segments, analogous to the lateral shifts of the two phase contributions in the lab Fizeau. The technique is based on a completely new approach to calibration of phase. It offers unusual flexibility with regard to the transverse spatial frequency scales probed, and will give results quite quickly, making use of no auxiliary equipment other than that built into the adaptive optics system. The new technique may be applied to provide novel calibration information about other optical systems in which the beam may be shifted transversely in a controlled way.

  11. Adaptive coded spreading OFDM signal for dynamic-λ optical access network

    Science.gov (United States)

    Liu, Bo; Zhang, Lijia; Xin, Xiangjun

    2015-12-01

    This paper proposes and experimentally demonstrates a novel adaptive coded spreading (ACS) orthogonal frequency division multiplexing (OFDM) signal for dynamic distributed optical ring-based access network. The wavelength can be assigned to different remote nodes (RNs) according to the traffic demand of optical network unit (ONU). The ACS can provide dynamic spreading gain to different signals according to the split ratio or transmission length, which offers flexible power budget for the network. A 10×13.12 Gb/s OFDM access with ACS is successfully demonstrated over two RNs and 120 km transmission in the experiment. The demonstrated method may be viewed as one promising for future optical metro access network.

  12. Fast binarized time-reversed adapted-perturbation (b-TRAP) optical focusing inside scattering media

    CERN Document Server

    Ma, Cheng; Liu, Yan; Wang, Lihong V

    2015-01-01

    Light scattering inhibits high-resolution optical imaging, manipulation and therapy deep inside biological tissue by preventing focusing. To form deep foci, wavefront-shaping and time-reversal techniques that break the optical diffusion limit have been developed. For in vivo applications, such focusing must provide high gain, high speed, and a large number of spatial modes. However, none of the previous techniques meet these requirements simultaneously. Here, we overcome this challenge by rapidly measuring the perturbed optical field within a single camera exposure followed by adaptively time-reversing the phase-binarized perturbation. Consequently, a phase-conjugated wavefront is synthesized within a millisecond, two orders of magnitude shorter than the digitally achieved record. We demonstrated real-time focusing in dynamic scattering media, and extended laser speckle contrast imaging to new depths. The unprecedented combination of fast response, high gain, and large mode count makes this work a major strid...

  13. Field of view advantage of conjugate adaptive optics in microscopy applications

    CERN Document Server

    Mertz, Jerome; Bifano, Thomas G

    2015-01-01

    The imaging performance of an optical microscope can be degraded by sample-induced aberrations. A general strategy to undo the effect of these aberrations is to apply wavefront correction with a deformable mirror (DM). In most cases, the DM is placed conjugate to the microscope pupil, called pupil adaptive optics (AO). When the aberrations are spatially variant, an alternative configuration involves placing the DM conjugate to the main source of aberrations, called conjugate AO. We provide theoretical and experimental comparison of both configurations for the simplified case where spatially variant aberrations are produced by a well defined phase screen. We pay particular attention to the resulting correction field of view (FOV). Conjugate AO is found to provide a significant FOV advantage. While this result is well known in the astronomy community, our goal here is to recast it specifically for the optical microscopy community.

  14. Mission to Mars: Adaptive Identifier for the Solution of Inverse Optical Metrology Tasks

    Science.gov (United States)

    Krapivin, Vladimir F.; Varotsos, Costas A.; Christodoulakis, John

    2016-06-01

    A human mission to Mars requires the solution of many problems that mainly linked to the safety of life, the reliable operational control of drinking water as well as health care. The availability of liquid fuels is also an important issue since the existing tools cannot fully provide the required liquid fuels quantities for the mission return journey. This paper presents the development of new methods and technology for reliable, operational, and with high availability chemical analysis of liquid solutions of various types. This technology is based on the employment of optical sensors (such as the multi-channel spectrophotometers or spectroellipsometers and microwave radiometers) and the development of a database of spectral images for typical liquid solutions that could be the objects of life on Mars. This database exploits the adaptive recognition of optical images of liquids using specific algorithms that are based on spectral analysis, cluster analysis and methods for solving the inverse optical metrology tasks.

  15. High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Julia Wilhelmsen [Univ. of California, Davis, CA (United States)

    2006-01-01

    Direct imaging of extrasolar planets is an important, but challenging, next step in planetary science. Most planets identified to date have been detected indirectly--not by emitted or reflected light but through the effect of the planet on the parent star. For example, radial velocity techniques measure the doppler shift in the spectrum of the star produced by the presence of a planet. Indirect techniques only probe about 15% of the orbital parameter space of our solar system. Direct methods would probe new parameter space, and the detected light can be analyzed spectroscopically, providing new information about detected planets. High contrast adaptive optics systems, also known as Extreme Adaptive Optics (ExAO), will require contrasts of between 10-6 and 10-7 at angles of 4-24 λ/D on an 8-m class telescope to image young Jupiter-like planets still warm with the heat of formation. Contrast is defined as the intensity ratio of the dark wings of the image, where a planet might be, to the bright core of the star. Such instruments will be technically challenging, requiring high order adaptive optics with > 2000 actuators and improved diffraction suppression. Contrast is ultimately limited by residual static wavefront errors, so an extrasolar planet imager will require wavefront control with an accuracy of better than 1 nm rms within the low- to mid-spatial frequency range. Laboratory demonstrations are critical to instrument development. The ExAO testbed at the Laboratory for Adaptive Optics was designed with low wavefront error and precision optical metrology, which is used to explore contrast limits and develop the technology needed for an extrasolar planet imager. A state-of-the-art, 1024-actuator micro-electrical-mechanical-systems (MEMS) deformable mirror was installed and characterized to provide active wavefront control and test this novel technology. I present 6.5 x 10-8 contrast measurements with a prolate shaped pupil and

  16. Investigation on a replica step gauge for optical 3D scanning of micro parts

    DEFF Research Database (Denmark)

    Cantatore, Angela; De Chiffre, Leonardo; Carmignato, S.

    2010-01-01

    This work deals with investigation of the stability over time and surface cooperativeness of a calibration artefact intended for optical scanner verification. A replica step gauge with 11 grooves, made of bisacryl material for dental applications (luxabite) and previously fabricated was studied....... The stability over time of the step gauge was evaluated by repetitive measurement campaigns over a period of eight months, using measurements taken with a tactile CMM and with an optical scanner. Surface cooperativeness was investigated by measuring artefact grooves and pitch and comparing results with tactile...

  17. Optical nonlinearity of organic dyes as studied by Z-scan and transient grating techniques

    Indian Academy of Sciences (India)

    Umakanta Tripathy; R Justin Rajesh; Prem B Bisht; A Subrahamanyam

    2002-12-01

    The excited state absorption cross-section of 5,5′-dichloro-11-diphenylamino- 3,3′-diethyl-10,12-ethylinethiatricarbocyanine perchlorate (IR140) have been measured by using a single beam transmission technique. Z-scan experiments have been used to find out a few nonlinear parameters. The excited state relaxation times have also been measured by using laser induced transient grating (LITG) technique.

  18. Direct measurement of the surface dynamics of supercooled liquid-glycerol by optical scanning a film

    Institute of Scientific and Technical Information of China (English)

    Zhang Fang; Zhang Guo-Feng; Dong Shuang-Li; Sun Jian-Hu; Chen Rui-Yun; Xiao Lian-Tuan; Jia Suo-Tang

    2009-01-01

    The surface dynamics of supercooled liquid-glycerol is studied by scanning the thickness of the glycerol film with single photon detection. Measurements are performed at room temperature well above the glycerol's glass transition temperature. It is shown that the surface dynamics of the glycerol film is very sensitive to the temperature. The linear relationship between the thickness of the film and the viscosity predicted by the Vogel-Fulcher-Tammann-Hesse (VFTH) law is also presented experimentally.

  19. Remote optical sensing on the nanometer scale with a bowtie aperture nano-antenna on a fiber tip of scanning near-field optical microscopy

    International Nuclear Information System (INIS)

    Plasmonic nano-antennas have proven the outstanding ability of sensing chemical and physical processes down to the nanometer scale. Sensing is usually achieved within the highly confined optical fields generated resonantly by the nano-antennas, i.e., in contact to the nanostructures. In this paper, we demonstrate the sensing capability of nano-antennas to their larger scale environment, well beyond their plasmonic confinement volume, leading to the concept of “remote” (non contact) sensing on the nanometer scale. On the basis of a bowtie-aperture nano-antenna (BNA) integrated at the apex of a SNOM (Scanning Near-field Optical Microscopy) fiber tip, we introduce an ultra-compact, moveable, and background-free optical nanosensor for the remote sensing of a silicon surface (up to distance of 300 nm). Sensitivity of the BNA to its large scale environment is high enough to expect the monitoring and control of the spacing between the nano-antenna and a silicon surface with sub-nanometer accuracy. This work paves the way towards an alternative class of nanopositioning techniques, based on the monitoring of diffraction-free plasmon resonance, that are alternative to nanomechanical and diffraction-limited optical interference-based devices

  20. Remote optical sensing on the nanometer scale with a bowtie aperture nano-antenna on a fiber tip of scanning near-field optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Atie, Elie M.; Xie, Zhihua; El Eter, Ali; Salut, Roland; Baida, Fadi I.; Grosjean, Thierry, E-mail: thierry.grosjean@univ-fcomte.fr [Institut FEMTO-ST, UMR CNRS 6174, Université de Franche-Comté, Département d' Optique P.M. Duffieux, 15B avenue des Montboucons, 25030 Besançon cedex (France); Nedeljkovic, Dusan [Lovalite s.a.s., 7 rue Xavier Marmier, 25000 Besançon (France); Tannous, Tony [Department of Physics, University of Balamand, P.O. Box 100 Tripoli (Lebanon)

    2015-04-13

    Plasmonic nano-antennas have proven the outstanding ability of sensing chemical and physical processes down to the nanometer scale. Sensing is usually achieved within the highly confined optical fields generated resonantly by the nano-antennas, i.e., in contact to the nanostructures. In this paper, we demonstrate the sensing capability of nano-antennas to their larger scale environment, well beyond their plasmonic confinement volume, leading to the concept of “remote” (non contact) sensing on the nanometer scale. On the basis of a bowtie-aperture nano-antenna (BNA) integrated at the apex of a SNOM (Scanning Near-field Optical Microscopy) fiber tip, we introduce an ultra-compact, moveable, and background-free optical nanosensor for the remote sensing of a silicon surface (up to distance of 300 nm). Sensitivity of the BNA to its large scale environment is high enough to expect the monitoring and control of the spacing between the nano-antenna and a silicon surface with sub-nanometer accuracy. This work paves the way towards an alternative class of nanopositioning techniques, based on the monitoring of diffraction-free plasmon resonance, that are alternative to nanomechanical and diffraction-limited optical interference-based devices.

  1. Noninvasive monitoring of glucose concentration using differential absorption low-coherence interferometry based on rapid scanning optical delay line

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yong; Zeng Nan; He Yonghong, E-mail: heyh@sz.tsinghua.edu.cn [Laboratory of Optical Imaging and Sensing, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055 (China)

    2011-01-01

    A non-invasive method of detecting glucose concentration using differential absorption low-coherence interferometry (DALCI) based on rapid scanning optical delay line is presented. Two light sources, one centered within (1625 nm) a glucose absorption band, while the other outside (1310 nm) the glucose absorption band, are used in the experiment. The low-coherence interferometry (LCI) is employed to obtain the signals back-reflecting from the iris which carries the messages of material concentration in anterior chamber. Using rapid scanning optical delay line (RSOD) as the reference arm, we can detect the signals in a very short time. Therefore the glucose concentration can be monitored in real-time, which is very important for the detection in vivo. In our experiments, the cornea and aqueous humor can be treated as nearly non-scattering substance. The difference in the absorption coefficient is much larger than the difference in the scattering coefficient, so the influence of scattering can be neglected. By subtracting the algorithmic low-coherence interference signals of the two wavelengths, the absorption coefficient can be calculated which is proportional to glucose concentration. To reduce the speckle noise, a 30 variation of signals were used before the final calculation of the glucose concentration. The improvements of our experiment are also discussed in the article. The method has a potential application for noninvasive detection of glucose concentration in vivo and in real-time.

  2. Development and Experimental Testing of an Optical Micro-Spectroscopic Technique Incorporating True Line-Scan Excitation

    Directory of Open Access Journals (Sweden)

    Gabriel Biener

    2013-12-01

    Full Text Available Multiphoton micro-spectroscopy, employing diffraction optics and electron-multiplying CCD (EMCCD cameras, is a suitable method for determining protein complex stoichiometry, quaternary structure, and spatial distribution in living cells using Förster resonance energy transfer (FRET imaging. The method provides highly resolved spectra of molecules or molecular complexes at each image pixel, and it does so on a timescale shorter than that of molecular diffusion, which scrambles the spectral information. Acquisition of an entire spectrally resolved image, however, is slower than that of broad-bandwidth microscopes because it takes longer times to collect the same number of photons at each emission wavelength as in a broad bandwidth. Here, we demonstrate an optical micro-spectroscopic scheme that employs a laser beam shaped into a line to excite in parallel multiple sample voxels. The method presents dramatically increased sensitivity and/or acquisition speed and, at the same time, has excellent spatial and spectral resolution, similar to point-scan configurations. When applied to FRET imaging using an oligomeric FRET construct expressed in living cells and consisting of a FRET acceptor linked to three donors, the technique based on line-shaped excitation provides higher accuracy compared to the point-scan approach, and it reduces artifacts caused by photobleaching and other undesired photophysical effects.

  3. Determination of third-order optical absorptive nonlinearity of ZnO nanoparticles by Z-scan technique

    Science.gov (United States)

    Sreeja, R.; Reshmi, R.; Manu, George; Jayaraj, M. K.

    2008-09-01

    A sensitive single-beam technique for measuring the nonlinear absorption coefficient of ZnO nanoparticles is reported here. The transmittance T(z) of the sample is measured by open aperture Z-scan technique as the sample is moved along the propagation path(z) of a focused Gaussian laser beam. The ZnO nanoparticles synthesized by wet chemical method, by mixing zinc acetate dehydrate and NaOH in ethanol is a clear transparent colloidal solution. The average size of ZnO nanoparticles is 6nm as confirmed by TEM analysis. Two-photon absorption of colloidal solutions of ZnO nanoparticles in ethanol is investigated by the Z-scan method using the nanosecond pulses from the second harmonics of Nd:YAG laser (532nm). The value of β for ZnO dispersed in ethanol extracted from the Z-scan data are 2.1cm/GW. ZnO nanoparticles of various sizes were embedded in PVA matrix on glass substrate and size dependence on β value was analyzed. The high value of two photon absorption coefficient (β) demonstrate that ZnO nanoparticle is a potential material for optical limiting applications.

  4. High-resolution in-depth imaging of optically cleared thick samples using an adaptive SPIM

    Science.gov (United States)

    Masson, Aurore; Escande, Paul; Frongia, Céline; Clouvel, Grégory; Ducommun, Bernard; Lorenzo, Corinne

    2015-11-01

    Today, Light Sheet Fluorescence Microscopy (LSFM) makes it possible to image fluorescent samples through depths of several hundreds of microns. However, LSFM also suffers from scattering, absorption and optical aberrations. Spatial variations in the refractive index inside the samples cause major changes to the light path resulting in loss of signal and contrast in the deepest regions, thus impairing in-depth imaging capability. These effects are particularly marked when inhomogeneous, complex biological samples are under study. Recently, chemical treatments have been developed to render a sample transparent by homogenizing its refractive index (RI), consequently enabling a reduction of scattering phenomena and a simplification of optical aberration patterns. One drawback of these methods is that the resulting RI of cleared samples does not match the working RI medium generally used for LSFM lenses. This RI mismatch leads to the presence of low-order aberrations and therefore to a significant degradation of image quality. In this paper, we introduce an original optical-chemical combined method based on an adaptive SPIM and a water-based clearing protocol enabling compensation for aberrations arising from RI mismatches induced by optical clearing methods and acquisition of high-resolution in-depth images of optically cleared complex thick samples such as Multi-Cellular Tumour Spheroids.

  5. Scan-less, line-field confocal microscopy by combination of wavelength/space conversion with dual optical comb

    Science.gov (United States)

    Yasui, Takeshi; Hase, Eiji; Miyamoto, Shuji; Hsieh, Yi-Da; Minamikawa, Takeo; Yamamoto, Hirotsugu

    2016-03-01

    Optical frequency comb (OFC) has attracted attentions for optical frequency metrology in visible and infrared regions because the mode-resolved OFC spectrum can be used as a precise frequency ruler due to both characteristics of broadband radiation and narrow-line CW radiation. Furthermore, the absolute accuracy of all frequency modes in OFC is secured by phase-locking a repetition frequency frep and a carrier-envelope-offset frequency fceo to a frequency standard. However, application fields of OFC other than optical frequency metrology are still undeveloped. One interesting aspect of OFC except for the frequency ruler is optical carrier having a huge number of discrete frequency channels because OFC is composed of a series of frequency spikes regularly separated by frep in the broad spectral range. If a certain quantity to be measured is encoded on each comb mode by dimensional conversion, a huge number of data for the measured quantity can be obtained from a single mode-resolved spectrum of OFC. In this paper, we encode the confocal microscopic line-image of a sample on the mode-resolved OFC spectrum by the dimensional conversion between wavelength and 1D-space. The resulting image-encoded OFC spectrum is acquired by an optical spectrum analyzer or dual comb spectrometer. Finally, the line image of the sample is decoded from the spectral amplitude of the mode-resolved OFC spectrum. The combination of OFC with the dimensional conversion enables to establish both confocal modality and line-field imaging under the scan-less condition.

  6. Development of active/adaptive lightweight optics for the next generation of telescopes

    Science.gov (United States)

    Ghigo, M.; Basso, S.; Citterio, O.; Mazzoleni, F.; Vernani, D.

    2006-02-01

    The future large optical telescopes will have such large dimensions to require innovative technical solutions either in the engineering and optical fields. Their optics will have dimensions ranging from 30 to 100 m. and will be segmented. It is necessary to develop a cost effective industrial process, fast and efficient, to create the thousands of segments neeededs to assemble the mirrors of these instruments. INAF-OAB (Astronomical Observatory of Brera) is developing with INAF-Arcetri (Florence Astronomical Observatory) a method of production of lightweight glass optics that is suitable for the manufacturing of these segments. These optics will be also probably active and therefore the segments have to be thin, light and relatively flexible. The same requirements are valid also for the secondary adaptive mirrors foreseen for these telescopes and that therefore will benefit from the same technology. The technique under investigation foresees the thermal slumping of thin glass segments using a high quality ceramic mold (master). The sheet of glass is placed onto the mold and then, by means of a suitable thermal cycle, the glass is softened and its shape is changed copying the master shape. At the end of the slumping the correction of the remaining errors will be performed using the Ion Beam Figuring technique, a non-contact deterministic technique. To reduce the time spent for the correction it will be necessary to have shape errors on the segments as small as possible. A very preliminary series of experiments already performed on reduced size segments have shown that it is possible to copy a master shape with high accuracy (few microns PV) and it is very likely that copy accuracies of 1 micron or less are possible. The paper presents in detail the concepts of the proposed process and describes our current efforts that are aimed at the production of a scaled demonstrative adaptive segment of 50 cm of diameter.

  7. High-resolution three-dimensional scanning optical image system for intrinsic and extrinsic contrast agents in tissue

    Science.gov (United States)

    Gu, Yueqing; Qian, Zhiyu; Chen, Jinxian; Blessington, Dana; Ramanujam, Nimmi; Chance, Britton

    2002-01-01

    This article presents the theory and development of a three-dimensional (3D) imaging instrument capable of determining the biochemical properties of tissue by measuring the absorption or fluorescence of different intrinsic and extrinsic agents simultaneously. A bifurcated optical fiber bundle, serving to deliver the excitation light and collect the emission or reflection light, scans over the flat tissue surface retrieving optical signals in each pixel. Two-dimensional (2D) images of a series of subsequent sections are obtained after signal conversion and processing to yield a 3D image. Manipulation of the scanning step and diameter size of the fibers within the bundle, the spatial resolution of the instrument attains a maximum of 40 × 40 × 10 μm3. The wavelength range is extended from ultraviolet to the near infrared (NIR) through specialized optical design, typically employed for the NIR extrinsic contrast agents study. The instrument is most applicable in situations involving the measurement of fluorescence or absorption at any specific wavelength within the spectrum range. Flavoprotein and nicotinamide adeine dinucleotide are the two typical intrinsic agents indicating the oxidization and reduction status of the tissue sample, with their fluorescence detected at wavelengths of 540 and 440 nm, respectively. Oxy and deoxy hemoglobin are two other significant intrinsic agents for evaluating the blood oxygenation saturation by recording their absorptions at two different wavelengths of 577 and 546 nm. These intrinsic agents were measured in this study for comparison of biochemical properties of rat liver in different gas inhalation treatments. Indocyanine green, a NIR extrinsic contrast agent measured at wavelengths of 780 nm/830 nm as excitation/emission can indicate blood pooling by displaying the distribution of blood vessels within a 9 L tumor. The advantage of high sensitivity, spatial resolution, and broad applied potentiality were demonstrated by the

  8. Adaptive cancellation of light relative intensity noise for fiber optic gyroscope

    Directory of Open Access Journals (Sweden)

    Zhong xiao Ji

    2013-07-01

    Full Text Available In order to reduce the relative intensity noise (RIN in the interferometric signal of the fiber optic gyroscope (FOG, an adaptive noise subtraction method is presented, which aims to overcome to the drawbacks that the fixed delay time and gain of the digital noise subtraction method. The drawbacks will make the performance of FOG to be degraded greatly in the changing environment. In the paper the adaptive noise subtraction system based on the recursive least squares algorithm (RLS is formed in FPGA, in which the interferometric signal is regarded as the signal source, and RIN in the free end of the optical fiber coupler of FOG is looked as the noise reference signal. The two critical parameters that minimum delay time and its varying range result from measuring the minimum and maximum delay times of the interferometric signal in a certain temperature range. The off-line and on-line temperature experimental results verify the capability of adapting to the environmental temperature.

  9. Adaptive Cancellation of Light Relative Intensity Noise for Fiber Optic Gyroscope

    Directory of Open Access Journals (Sweden)

    Zhongxiao Ji

    2013-07-01

    Full Text Available In order to reduce the relative intensity noise (RIN in the interferometric signal of the fiber optic gyroscope (FOG, an adaptive noise subtraction method is presented, which aims to overcome to the drawbacks that the fixed delay time and gain of the digital noise subtraction method. The drawbacks will make the performance of FOG to be degraded greatly in the changing environment. In the paper the adaptive noise subtraction system based on the recursive least squares algorithm (RLS is formed in FPGA, in which the interferometric signal is regarded as the signal source, and RIN in the free end of the optical fiber coupler of FOG is looked as the noise reference signal. The two critical parameters that minimum delay time and its varying range result from measuring the minimum and maximum delay times of the interferometric signal in a certain temperature range. The off-line and on-line temperature experimental results verify the capability of adapting to the environmental temperature.      

  10. Nonlinear Optical Properties of Novel Polymeric Rare Earth Phthalocyanine Studied Using Picosecond Z-Scan Technique

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; XU Song; LI Zhong-Yu; ZHANG Fu-Shi

    2008-01-01

    Three novel tri-dimensional phthalocyanine polymers, with lanthanum (LaPPc), gadolinium (GdPPc) and ytter-bium (YbPPc) as centric atoms, have been synthesized from a tetranuclear phthalonitrile. Third-order optical nonlinearities of these compounds in DMF solution are measured by a picosecond Z-sacn technique at 532nm. It is found that all the compounds show reverse saturation absorption and nonlinear self-focus refraction effect. The second-order molecular hyperpolarizabilities are calculated to be 1.82×10-29, 1.48×10-29 and 1.45×10-29 esu for LaPPc, GdPPc and YbPPc, respectively. The differences among their nonlinear optical properties are attributed to the special tri-dimensional structure and the variation in rare earth atoms.

  11. A high sensitivity optically stimulated luminescence scanning system for measurement of single sand-sized grains

    DEFF Research Database (Denmark)

    Duller, G.A.T.; Bøtter-Jensen, L.; Kohsiek, P.;

    1999-01-01

    An instrument has been designed for the routine analysis of the optically stimulated luminescence signal from single grains of sand. The system is capable of analysing over 3000 individual grains in a single measurement sequence, and the OSL signal from each grain can be read in less than 3 s....... The design principles are described, along with preliminary measurements that illustrate the operation of the system and its capabilities....

  12. Coronagraphic Imager with Adaptive Optics (CIAO) for the Subaru 8.2m Telescope

    Science.gov (United States)

    Tamura, M.; Suto, H.; Murakawa, K.; Hayashi, S.; Kaifu, N.; Itoh, Y.; Fukagawa, M.; Oasa, Y.; Naoi, T.

    2001-05-01

    We describe a near-infrared coronagraphic camera built for use with the Subaru 8.2m telescope and its adaptive optics system. This instrument, CIAO, aims to obtain high-resolution (0.06 arcsec at 2 micron) images of faint objects in close vicinity of bright objects at near-infrared wavelengths. The coronagraphic optics are all cooled. Occulting masks whose diameter ranges from 0.1 to 3 arcsec and several types of Lyot stops are selectable. Standard broad-band imaging and a number of narow-band imaging are possible with or without coronagraph, with two pixel scales of 22 mas/pixel and 11 mas/pixel. Low resolution coronagraphic grism spectroscopy is also available. CIAO utilize one ALLADIN II (1024x1024 InSb) scince-grade array detector manufactured by Raytheon, covering the wavelengths from 1 to 5 micron. CIAO will be very useful for studies of companion brown dwarfs and extra-solar planets, circumstelar disks around both young stelar obejcts and main-sequence stars, jets and outflows from both young stars and evolved stars, circumnuclear regions around AGNs, and host galaxies of QSOs. We also present preliminary results from the first commissioning run with adaptive optics at the Subaru telescope.

  13. Early ComeOn+ Adaptive Optics Observation of GQ Lup and its Substellar Companion

    CERN Document Server

    Janson, M; Henning, T; Zinnecker, H; Janson, Markus; Brandner, Wolfgang; Henning, Thomas; Zinnecker, Hans

    2006-01-01

    An analysis of adaptive optics K-band imaging data of GQ Lup acquired in 1994 by the first generation adaptive optics system ComeOn+ at the ESO 3.6m optical telescope in La Silla is presented. The data reveal a likely candidate for the low-mass companion recently reported in the literature. An a posteriori detection in the 11 year old data would provide a useful astrometric data point for the very long period (~1000 yr) orbit of the GQ Lup system. However, the data is severely contaminated by speckle noise at the given projected separation, which decreases the confidence of the detection. Still, from the data we can conclude that GQ Lup B is not an unrelated background source, but instead a physical companion to GQ Lup A. We present here the reduction and analysis of the ComeOn+ images, as well as the results. We also discuss the nature of the companion based on data and models available in the scientific literature and examine claims made regarding the classification of the object as a planet.

  14. Adaptive neuro-fuzzy prediction of modulation transfer function of optical lens system

    Science.gov (United States)

    Petković, Dalibor; Shamshirband, Shahaboddin; Anuar, Nor Badrul; Md Nasir, Mohd Hairul Nizam; Pavlović, Nenad T.; Akib, Shatirah

    2014-07-01

    The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to predict MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using MATLAB/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

  15. Modulation transfer function estimation of optical lens system by adaptive neuro-fuzzy methodology

    Science.gov (United States)

    Petković, Dalibor; Shamshirband, Shahaboddin; Pavlović, Nenad T.; Anuar, Nor Badrul; Kiah, Miss Laiha Mat

    2014-07-01

    The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to estimate MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

  16. Micrometric precision of prosthetic dental crowns obtained by optical scanning and computer-aided designing/computer-aided manufacturing system

    Science.gov (United States)

    das Neves, Flávio Domingues; de Almeida Prado Naves Carneiro, Thiago; do Prado, Célio Jesus; Prudente, Marcel Santana; Zancopé, Karla; Davi, Letícia Resende; Mendonça, Gustavo; Soares, Carlos José

    2014-08-01

    The current study evaluated prosthetic dental crowns obtained by optical scanning and a computer-aided designing/computer-aided manufacturing system using micro-computed tomography to compare the marginal fit. The virtual models were obtained with four different scanning surfaces: typodont (T), regular impressions (RI), master casts (MC), and powdered master casts (PMC). Five virtual models were obtained for each group. For each model, a crown was designed on the software and milled from feldspathic ceramic blocks. Micro-CT images were obtained for marginal gap measurements and the data were statistically analyzed by one-way analysis of variance followed by Tukey's test. The mean vertical misfit was T=62.6±65.2 μm; MC=60.4±38.4 μm; PMC=58.1±38.0 μm, and RI=89.8±62.8 μm. Considering a percentage of vertical marginal gap of up to 75 μm, the results were T=71.5%, RI=49.2%, MC=69.6%, and PMC=71.2%. The percentages of horizontal overextension were T=8.5%, RI=0%, MC=0.8%, and PMC=3.8%. Based on the results, virtual model acquisition by scanning the typodont (simulated mouth) or MC, with or without powder, showed acceptable values for the marginal gap. The higher result of marginal gap of the RI group suggests that it is preferable to scan this directly from the mouth or from MC.

  17. Third-Order Optical Nonlinearities of Squarylium Dyes with Benzothiazole Donor Groups Measured Using the Picosecond Z-Scan Technique

    International Nuclear Information System (INIS)

    Third-order optical nonlinearities of two squarylium dyes with benzothiazole donor groups (BSQ1 and BSQ2) in chloroform solution are measured by a picosecond Z-scan technique at 532 nm. It is found that the two compounds show the saturation absorption and nonlinear self-focus refraction effect. The molecular second hyperpolarizabilities are calculated to be 7.46 × 10−31 esu and 5.01 × 10−30 esu for BSQ1 and BSQ2, respectively. The large optical nonlinearities of squarylium dyes can be attributed to their rigid and intramolecular charge transfer structure. The difference in γ values is attributed to the chloro group of benzene rings of BSQ2 and the one-photon resonance effect. It is found that the third-order nonlinear susceptibilities of two squarylium dyes are mainly determined by the real parts of χ(3), and the large optical nonlinearities of studied squarylium dyes can be attributed to the nonlinear refraction. (fundamental areas of phenomenology(including applications))

  18. Feasibility study on 3-D shape analysis of high-aspect-ratio features using through-focus scanning optical microscopy

    Science.gov (United States)

    Attota, Ravi Kiran; Weck, Peter; Kramar, John A.; Bunday, Benjamin; Vartanian, Victor

    2016-01-01

    In-line metrologies currently used in the semiconductor industry are being challenged by the aggressive pace of device scaling and the adoption of novel device architectures. Metrology and process control of three-dimensional (3-D) high-aspect-ratio (HAR) features are becoming increasingly important and also challenging. In this paper we present a feasibility study of through-focus scanning optical microscopy (TSOM) for 3-D shape analysis of HAR features. TSOM makes use of 3-D optical data collected using a conventional optical microscope for 3-D shape analysis. Simulation results of trenches and holes down to the 11 nm node are presented. The ability of TSOM to analyze an array of HAR features or a single isolated HAR feature is also presented. This allows for the use of targets with area over 100 times smaller than that of conventional gratings, saving valuable real estate on the wafers. Indications are that the sensitivity of TSOM may match or exceed the International Technology Roadmap for Semiconductors (ITRS) measurement requirements for the next several years. Both simulations and preliminary experimental results are presented. The simplicity, lowcost, high throughput, and nanometer scale 3-D shape sensitivity of TSOM make it an attractive inspection and process monitoring solution for nanomanufacturing. PMID:27464112

  19. Feasibility study on 3-D shape analysis of high-aspect-ratio features using through-focus scanning optical microscopy.

    Science.gov (United States)

    Attota, Ravi Kiran; Weck, Peter; Kramar, John A; Bunday, Benjamin; Vartanian, Victor

    2016-07-25

    In-line metrologies currently used in the semiconductor industry are being challenged by the aggressive pace of device scaling and the adoption of novel device architectures. Metrology and process control of three-dimensional (3-D) high-aspect-ratio (HAR) features are becoming increasingly important and also challenging. In this paper we present a feasibility study of through-focus scanning optical microscopy (TSOM) for 3-D shape analysis of HAR features. TSOM makes use of 3-D optical data collected using a conventional optical microscope for 3-D shape analysis. Simulation results of trenches and holes down to the 11 nm node are presented. The ability of TSOM to analyze an array of HAR features or a single isolated HAR feature is also presented. This allows for the use of targets with area over 100 times smaller than that of conventional gratings, saving valuable real estate on the wafers. Indications are that the sensitivity of TSOM may match or exceed the International Technology Roadmap for Semiconductors (ITRS) measurement requirements for the next several years. Both simulations and preliminary experimental results are presented. The simplicity, lowcost, high throughput, and nanometer scale 3-D shape sensitivity of TSOM make it an attractive inspection and process monitoring solution for nanomanufacturing. PMID:27464112

  20. Performance Investigation on Scan-On-Receive and Adaptive Digital Beam-Forming for High-Resolution Wide-Swath Synthetic Aperture Radar

    OpenAIRE

    Bordoni, Federica; Younis, Marwan; Makhoul Varona, Eduardo; Gebert, Nicolas; Krieger, Gerhard

    2009-01-01

    The work investigates the performance of the Smart Multi-Aperture Radar Technique (SMART) Synthetic Aperture Radar (SAR) system for high-resolution wide-swath imaging based on Scan-on-Receive (SCORE) algorithm for receive beam steering. SCORE algorithm works under model mismatch conditions in presence of topographic height. A study on the potentiality of an adaptive approach for receive beam steering based on spatial spectral estimation is presented. The impact of topographic height on SCORE ...

  1. Contrast enhancement in microscopy of human thyroid tumors by means of acousto-optic adaptive spatial filtering

    Science.gov (United States)

    Yushkov, Konstantin B.; Molchanov, Vladimir Y.; Belousov, Pavel V.; Abrosimov, Aleksander Y.

    2016-01-01

    We report a method for edge enhancement in the images of transparent samples using analog image processing in coherent light. The experimental technique is based on adaptive spatial filtering with an acousto-optic tunable filter in a telecentric optical system. We demonstrate processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  2. Wavefront sensorless adaptive optics fluorescence biomicroscope for in vivo retinal imaging in mice.

    Science.gov (United States)

    Wahl, Daniel J; Jian, Yifan; Bonora, Stefano; Zawadzki, Robert J; Sarunic, Marinko V

    2016-01-01

    Cellular-resolution in vivo fluorescence imaging is a valuable tool for longitudinal studies of retinal function in vision research. Wavefront sensorless adaptive optics (WSAO) is a developing technology that enables high-resolution imaging of the mouse retina. In place of the conventional method of using a Shack-Hartmann wavefront sensor to measure the aberrations directly, WSAO uses an image quality metric and a search algorithm to drive the shape of the adaptive element (i.e. deformable mirror). WSAO is a robust approach to AO and it is compatible with a compact, low-cost lens-based system. In this report, we demonstrated a hill-climbing algorithm for WSAO with a variable focus lens and deformable mirror for non-invasive in vivo imaging of EGFP (enhanced green fluorescent protein) labelled ganglion cells and microglia cells in the mouse retina.

  3. woptic: optical conductivity with Wannier functions and adaptive k-mesh refinement

    CERN Document Server

    Assmann, E; Kuneš, J; Toschi, A; Blaha, P; Held, K

    2015-01-01

    We present an algorithm for the adaptive tetrahedral integration over the Brillouin zone of crystalline materials, and apply it to compute the optical conductivity, dc conductivity, and thermopower. For these quantities, whose contributions are often localized in small portions of the Brillouin zone, adaptive integration is especially relevant. Our implementation, the woptic package, is tied into the wien2wannier framework and allows including a many-body self energy, e.g. from dynamical mean-field theory (DMFT). Wannier functions and dipole matrix elements are computed with the DFT package Wien2k and Wannier90. For illustration, we show DFT results for fcc-Al and DMFT results for the correlated metal SrVO$_3$.

  4. Wavefront sensorless adaptive optics fluorescence biomicroscope for in vivo retinal imaging in mice.

    Science.gov (United States)

    Wahl, Daniel J; Jian, Yifan; Bonora, Stefano; Zawadzki, Robert J; Sarunic, Marinko V

    2016-01-01

    Cellular-resolution in vivo fluorescence imaging is a valuable tool for longitudinal studies of retinal function in vision research. Wavefront sensorless adaptive optics (WSAO) is a developing technology that enables high-resolution imaging of the mouse retina. In place of the conventional method of using a Shack-Hartmann wavefront sensor to measure the aberrations directly, WSAO uses an image quality metric and a search algorithm to drive the shape of the adaptive element (i.e. deformable mirror). WSAO is a robust approach to AO and it is compatible with a compact, low-cost lens-based system. In this report, we demonstrated a hill-climbing algorithm for WSAO with a variable focus lens and deformable mirror for non-invasive in vivo imaging of EGFP (enhanced green fluorescent protein) labelled ganglion cells and microglia cells in the mouse retina. PMID:26819812

  5. Efficient wave function simulations in nonlinear quantum optics using an adaptive coherent state basis

    International Nuclear Information System (INIS)

    Full text: We show that a suitable set of coherent basis states placed on a discrete hexagonal grid can be used to numerically very accurately represent general quantum states in a memory efficient way. Adding an algorithm for dynamic basis adaptation allows highly accurate Quantum Monte Carlo wave function simulations with small basis sets. At the example of the intricate nonlinear dynamics of an optical parametric oscillator around threshold, we demonstrate that this approach yields accurate time dependent solutions with a substantially smaller basis sets than required for a photon number basis. Above threshold the adaptive basis splits into localized subsets allowing efficient representation of bimodal or even more complex phase space distributions and directly yields an intuitive physical picture of the ongoing dynamics. (author)

  6. AMA- and RWE- Based Adaptive Kalman Filter for Denoising Fiber Optic Gyroscope Drift Signal.

    Science.gov (United States)

    Yang, Gongliu; Liu, Yuanyuan; Li, Ming; Song, Shunguang

    2015-10-23

    An improved double-factor adaptive Kalman filter called AMA-RWE-DFAKF is proposed to denoise fiber optic gyroscope (FOG) drift signal in both static and dynamic conditions. The first factor is Kalman gain updated by random weighting estimation (RWE) of the covariance matrix of innovation sequence at any time to ensure the lowest noise level of output, but the inertia of KF response increases in dynamic condition. To decrease the inertia, the second factor is the covariance matrix of predicted state vector adjusted by RWE only when discontinuities are detected by adaptive moving average (AMA).The AMA-RWE-DFAKF is applied for denoising FOG static and dynamic signals, its performance is compared with conventional KF (CKF), RWE-based adaptive KF with gain correction (RWE-AKFG), AMA- and RWE- based dual mode adaptive KF (AMA-RWE-DMAKF). Results of Allan variance on static signal and root mean square error (RMSE) on dynamic signal show that this proposed algorithm outperforms all the considered methods in denoising FOG signal.

  7. Sensitivity calibration procedures in optical-CT scanning of BANG®3 polymer gel dosimeters

    OpenAIRE

    Xu, Y; Wuu, Cheng-Shie; Maryanski, Marek J.

    2010-01-01

    The dose response of the BANG®3 polymer gel dosimeter (MGS Research Inc., Madison, CT) was studied using the OCTOPUS™ laser CT scanner (MGS Research Inc., Madison, CT). Six 17 cm diameter and 12 cm high Barex cylinders, and 18 small glass vials were used to house the gel. The gel phantoms were irradiated with 6 and 10 MV photons, as well as 12 and 16 MeV electrons using a Varian Clinac 2100EX. Three calibration methods were used to obtain the dose response curves: (a) Optical density measurem...

  8. Submicrometer infrared surface imaging using a scanning-probe microscope and an optical parametric oscillator laser.

    Science.gov (United States)

    Hill, Graeme A; Rice, James H; Meech, Stephen R; Craig, Duncan Q M; Kuo, Paulina; Vodopyanov, Konstantin; Reading, Michael

    2009-02-15

    Submicrometer IR surface imaging was performed with a resolution better than the diffraction limit. The apparatus was based on an IR optical parametric oscillator laser and a commercial atomic force microscope and used, as the detection mechanism, induced resonant oscillations in an atomic force microscopy (AFM) cantilever. For the first time to our knowledge this was achieved with top-down illumination and a benchtop IR source, thus extending the range of potential applications of this technique. IR absorption and AFM topography images of polystyrene beads were recorded simultaneously with an image resolution of 200 nm. PMID:19373331

  9. Third order optical non-linear (Z-scan), birefringence, photoluminescence, mechanical and etching studies on melaminium levulinate monohydrate (MLM) single crystal for optical device applications

    Science.gov (United States)

    Sivakumar, N.; Anbalagan, G.

    2016-10-01

    Z-scan studies on the grown crystal was investigated by diode-pumped Nd; YAG laser. Nonlinear refractive index (n2) and third-order nonlinear optical susceptibility (χ3) values of MLM were found to be -1.0 × 10-8 cm2/W and 1.36 × 10-6 esu respectively. Powder X-ray diffraction analysis depicted that the crystal belongs to monoclinic system with space group P21/c. Birefringence study revealed the optical dispersion behavior of MLM crystal. Linear refractive index on (10-1) plane was measured by prism coupling technique and was estimated to be 1.4705. Hardness study was carried out along three different planes which exhibit hardness anisotropy of 41.11%. Meyer's index values of the grown crystal for the (10-1), (010) and (111) planes were found to be 2.39, 2.61 and 2.04 respectively. Etching studies on the prominent (10-1) growth plane was explained by two dimensional layer growth mechanisms. Photoluminescence study was performed on MLM crystal to explore its efficacy towards optical device fabrications.

  10. Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

    Science.gov (United States)

    Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

    2015-12-28

    An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network. PMID:26832033

  11. Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

    Science.gov (United States)

    Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

    2015-12-28

    An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network.

  12. DESIGN ISSUES FOR BIT RATE-ADAPTIVE 3R O/E/OTRANSPONDER IN INTELLIGENT OPTICAL NETWORKS

    Institute of Scientific and Technical Information of China (English)

    朱栩; 曾庆济; 杨旭东; 刘逢清; 肖石林

    2002-01-01

    This paper reported the design and implementation of a bit rate-adaptive Optical-Electronic-Optical (O/E/O) transponder accomplishing almost full data rate transparency up to 2.5 Gb/s with 3R (Reamplifying, Reshaping and Retiming) processing in electronic domain. Based on the chipsets performing clock recovery in several continuous bit rate ranges, a clock and data regenerating circuit self-adaptive to the bit rate of input signal was developed. Key design issues were presented, laying stress on the functional building blocks and scheme for the bit rate-adaptive retiming circuit. The experimental results show a good scalability performance.

  13. Cell depth imaging by point laser scanning fluorescence microscopy with an optical disk pickup head

    Science.gov (United States)

    Tsai, Rung-Ywan; Chen, Jung-Po; Lee, Yuan-Chin; Chiang, Hung-Chih; Cheng, Chih-Ming; Huang, Chun-Chieh; Huang, Tai-Ting; Cheng, Chung-Ta; Tiao, Golden

    2015-09-01

    A compact, cost-effective, and position-addressable digital laser scanning microscopy (DLSM) instrument is made using a commercially available Blu-ray disc read-only memory (BD-ROM) pickup head. Fluorescent cell images captured by DLSM have resolutions of 0.38 µm. Because of the position-addressable function, multispectral fluorescence cell images are captured using the same sample slide with different excitation laser sources. Specially designed objective lenses with the same working distance as the image-capturing beam are used for the different excitation laser sources. By accurately controlling the tilting angles of the sample slide or by moving the collimator lens of the image-capturing beam, the fluorescence cell images along different depth positions of the sample are obtained. Thus, z-section images with micrometer-depth resolutions are achievable.

  14. Optical probing of sample heating in scanning near-field experiments with apertured probes

    International Nuclear Information System (INIS)

    We have used the inherent thermochromism of conjugated polymers to investigate substrate heating effects in scanning near-field experiments with metal-coated 'apertured' probes. Chemically etched and pulled fibers were used to provide near-field excitation of fully converted films of poly(p-phenylene vinylene), PPV, and of poly(4,4'-diphenylene diphenylvinylene). We detect no significant blueshift of the photoluminescence spectra generated with near-field excitation, in comparison to those collected with far-field excitation. We conclude that polymer heating in the region contributing to the luminescence is less than 40 K. We also demonstrate that thermolithography of the PPV precursor is not significant by comparing UV (325 nm) and red (670 nm) illumination

  15. Ultra-high vacuum compatible optical chopper system for synchrotron x-ray scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hao, E-mail: hc000211@ohio.edu [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701 (United States); Cummings, Marvin; Shirato, Nozomi; Stripe, Benjamin; Preissner, Curt; Freeland, John W. [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Rosenmann, Daniel [Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Kersell, Heath; Hla, Saw-Wai [Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701 (United States); Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Rose, Volker, E-mail: vrose@anl.gov [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

    2016-01-28

    High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.

  16. Optical surface scanning for respiratory motion monitoring in radiotherapy: a feasibility study

    DEFF Research Database (Denmark)

    Bekke, Susanne Lise; Mahmood, Faisal; Helt-Hansen, Jakob;

    2014-01-01

    Purpose. We evaluated the feasibility of a surface scanning system (Catalyst) for respiratory motion monitoring of breast cancer patients treated with radiotherapy in deep inspiration breath-hold (DIBH). DIBH is used to reduce the radiation dose to the heart and lung. In contrast to RPM...... and 3: the Quasar phantom was used to study if the angle of the monitored surface affects the amplitude of the recorded signal. Results. Experiment 1: we observed comparable period estimates for both systems. The amplitudes were 8 ± 0.1 mm (Catalyst) and 4.9 ± 0.1 mm (RPM). Independent check with in......, a competing marker-based system, Catalyst does not require an objectmarker on the patient's skin. Materials and Methods. Experiment 1: a manikin was used to simulate sinusoidal breathing. The amplitude, period and baseline (signal value at end-expiration) were estimated with RPM and Catalyst. Experiment 2...

  17. Recovery Management in All Optical Networks Using Biologically-Inspired Complex Adaptive System

    Directory of Open Access Journals (Sweden)

    Inadyuti Dutt

    2013-01-01

    Full Text Available All-Optical Networks have the ability to display varied advantages like performance efficiency, throughput etc but their efficiency depends on their survivability as they are attack prone. These attacks can be categorised as active or passive because they try to access information within the network or alter the information in the network. The attack once detected has to be recovered by formulating back-up or alternative paths. The proposed heuristic uses biologically inspired Complex Adaptive System, inspired by Natural Immune System. The study shows that natural immune system exhibit unique behaviour of detecting foreign bodies in our body and removing them on their first occurrences. This phenomenon is being utilised in the proposed heuristic for recovery management in All-optical Network

  18. Adaptive Optics Imaging of Lyman Break Galaxies as Progenitors of Spheroids in the Local Universe

    CERN Document Server

    Akiyama, M; Kobayashi, N; Ohta, K; Iwata, I

    2007-01-01

    In order to reveal the stellar mass distribution of z~3 galaxies, we are conducting deep imaging observations of U-dropout Lyman Break Galaxies (LBGs) with Adaptive Optics (AO) systems in K-band, which corresponds to rest-frame V-band of z~3 galaxies. The results of the Subaru intensive-program observations with AO36/NGS/IRCS indicate that 1) the K-band peaks of some of the LBGs brighter than K=22.0 mag show significant offset from those in the optical images, 2) the z~3 Mv* LBGs and serendipitously observed Distant Red Galaxies (DRGs) have flat profiles similar to disk galaxies in the local universe (i.e., Sersic with n2 systems among the luminous z~3 LBGs and DRGs, and their strong spatial clustering, we infer that the dense n2 spheroids of nearby galaxies through relaxations due to major merger events.

  19. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    Science.gov (United States)

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  20. Adaptive information interchange system of the fiber-optic measuring networks with the computer

    Science.gov (United States)

    Denisov, Igor V.; Drozdov, Roman S.; Sedov, Victor A.

    2005-06-01

    In the present paper the characteristics and opportunities of application of the system of parallel input-output of information from the fiber-optical measuring network into computer are considered. The system consists of two pars: on manframe and several expansion blocks. The first part is internal, is connected directly in the socket of the motherboard of the personal computer. It is designed for buffering system signals and development of cojmands of controlling by the system for input-output of signals into personal computer and signals generation onto expansion blocks. The second part is external, connects to the mainframe by means of cables. It designed for transformation of information from the fiber-optical measuring network into signalsof rthe mainframe and instrument settings adaptation. The analysis of speed of procesing of analog and digital data by system is presented. The possible schemes of use of the system for processing quasistationary and dynamic fields are considered.