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Sample records for laser doppler flowmeter

  1. Laser double Doppler flowmeter

    Science.gov (United States)

    Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

    2014-05-01

    The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

  2. Schlieren laser Doppler flowmeter for the human optical nerve head with the flicker stimuli

    OpenAIRE

    Geiser, Martial; Truffer, Frederic; Evequoz, Hugo; Khayi, Hafid; Mottet, Benjamin; Chiquet, Christophe

    2014-01-01

    We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination poin...

  3. Clinical investigation of the combination of a scanning laser ophthalmoscope and laser Doppler flowmeter.

    Science.gov (United States)

    Michelson, G; Langhans, M J; Groh, M J

    1995-11-01

    In this report we present the clinical applications of a new noninvasive method of imaging in high definition the topography of perfused retinal vessels. By the combination of a laser Doppler Flowmeter with a scanning laser system the retinal circulation can be visualized and quantified. The principles of measuring blood flow by laser Doppler flowmetry are based on the laser Doppler effect: laser light scattered by a moving particle is shifted in frequency. The scanning laser system is a modified laser scanning tomograph (technical data: retinal area of measurement, 2.7 x 0.7 mm; 10 degrees field with 256 points x 64 lines; horizontal digital resolution, 10 microns; wave-length, 670 nm; light power, 100 micro W; data acquisition time, 2.048 s). Every line is scanned 128-times at a line-sampling rate of 4000 Hz. By the performance of discrete fast fourier transformation over 128 intensities of each retinal point the laser Doppler shift is calculated for each retinal point. With these data a 2-dimensional map of the retinal perfusion with 256 x 64-points is created. The brightness of the picture point is coded by the value of the Doppler shift. By this method we examined health eyes with normal intraocular pressure (IOP) and artificially increased IOP and eyes with glaucomatous optic nerve atrophy, proliferative diabetic retinopathy with areas of capillary occlusion, arterial hypertension with microinfarction of the retina, and central retinal artery occlusion. The application of "scanning laser Doppler flowmetry" (SLDF) leads to the visualization of perfused vessels and capillaries of the retina in high resolution. The examination of perfused retinal arterioles, veins, and capillaries by this method represents the anatomical situation. In SLDF the area of normal or impaired retinal circulation becomes visible (capillary nonperfusion, proliferative vascular structures), whereby the extent of the perfusion is proportional to the brightness of the imaged vessel; the brighter the vessels or capillaries, the higher the blood flow inside the vessels. Retinal areas with low capillary flow are "dark" and show no visible vessel. In imaging of an eye with central retinal artery occlusion, retinal arterioles, veins, or capillaries were invisible due to the lack of retinal perfusion. Only ciliary-source vessels of the optic nerve head were bright and visible, indicating normal ciliary circulation. SLDF facilitates the visualization of perfused retinal capillaries and vessels in high resolution. The representation of the function of the retinal circulation by SLDF leads to an image similar to the anatomical situation. The two-dimensional mapping of local blood flow leads to a physiological picture of the retinal perfusion with visible vessels and capillaries. PMID:8751099

  4. Schlieren laser Doppler flowmeter for the human optical nerve head with the flicker stimuli

    Science.gov (United States)

    Geiser, Martial H.; Truffer, Frederic; Evequoz, Hugo; Khayi, Hafid; Mottet, Benjamin; Chiquet, Christophe

    2013-12-01

    We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination point. LDF measurements are based on heterodyne detection of Doppler shifted back-scattered light. We also describe an automated analysis of the LDF signals which rejects artifacts and false signals such as blinks. By using a Doppler simulator consisting of a lens and a rotating diffusing wheel, we demonstrate that velocity and flow vary linearly with the speed of the wheel. A cohort of 12 healthy subjects demonstrated that flicker stimulation induces an increase of 17.8% of blood flow in the ONH.

  5. Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats

    OpenAIRE

    Meirelles Jr. Roberto Ferreira; Ceneviva Reginaldo; Caboclo José Liberato Ferreira; Eisenberg Michael M.

    2003-01-01

    PURPOSE: The pancreatic capillary blood flow (PCBF) was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP) and heart rate (HR) were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control...

  6. Correlation between Changes in Leg Blood Flow and Ankle-Brachial Pressure Index: A Study Using Laser Doppler Flowmeter —The 1st Report—

    OpenAIRE

    Suzuki, Kazuyoshi; Sekiguchi, Miho; Midorikawa, Hirofumi; Sato, Koichi; Akase, Kazuyoshi; Sawada, Renshi; Konno, Shin-Ichi

    2011-01-01

    Objective: The objective of this study was to use non-invasive laser Doppler flowmeter to measure changes in blood flow in peripheral vessels in the legs before and after stress induced by leg elevation stress test and investigate correlations with the ankle-brachial pressure index (ABI).

  7. Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats Estudo das alterações do fluxo capilar pancreático após infusão de ceruleína avaliado por laser-Doppler em ratos

    OpenAIRE

    Roberto Ferreira Meirelles Jr.; Reginaldo Ceneviva; José Liberato Ferreira Caboclo; Michael M. Eisenberg

    2003-01-01

    PURPOSE: The pancreatic capillary blood flow (PCBF) was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP) and heart rate (HR) were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control...

  8. Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats

    Directory of Open Access Journals (Sweden)

    Meirelles Jr. Roberto Ferreira

    2003-01-01

    Full Text Available PURPOSE: The pancreatic capillary blood flow (PCBF was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP and heart rate (HR were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control group and caerulein group, respectively. Caerulein group had a mean decrease of 31.75 ± 16.79%. The serum amylase was 1323.70 ± 239.10U.I-1 and 2184.60 ± 700.46U.I-1 in control and caerulein groups, respectively. There was a significant difference in the PCBF (p<0.05 and serum amylase (p<0.05 when compared to control and caerulein groups. Although micro and microvacuolization were seen in 30% in caerulein group, no significant difference was seen between the groups. CONCLUSION: A decrease in the PCBF may be one of the leading events and it is present before histopathological tissue injury had been established in this model of acute pancreatitis.

  9. Pancreatic capillary blood flow during caerulein-induced pancreatitis evaluated by a laser-doppler flowmeter in rats / Estudo das alterações do fluxo capilar pancreático após infusão de ceruleína avaliado por laser-Doppler em ratos

    Scientific Electronic Library Online (English)

    Roberto Ferreira, Meirelles Jr.; Reginaldo, Ceneviva; José Liberato Ferreira, Caboclo; Michael M., Eisenberg.

    Full Text Available OBJETIVO: O fluxo capilar pancreático (FCP) foi estudado para determinar suas alterações durante a pancreatite aguda induzida por ceruleína, em ratos. MÉTODOS: Vinte ratos foram divididos em grupo controle e grupo ceruleína. Um laser-Doppler fluxímetro foi empregado para determinar, continuamente, o [...] FCP durante 120 minutos. A pressão arterial média (PAM) e a freqüência cardíaca (FC) foram determinadas, durante o experimento. Análise bioquímica sérica e estudo histopatológico, por microscopia ótica, do tecido pancreático foram realizados, ao final do experimento. RESULTADOS: O FCP foi em média 109,08 ± 2,17% e 68,24 ± 16,79% nos grupos controle e ceruleína , respectivamente. No grupo ceruleína, houve uma diminuição média de 31,75 ± 16,79%. Os níveis de amilase sérica foram de 1323,70 ± 239,10U.I-1 e 2184,60 ± 700,46U.I-1 nos grupos controle e ceruleína, respectivamente. Houve diferença significante (p Abstract in english PURPOSE: The pancreatic capillary blood flow (PCBF) was studied to determine its alterations during caerulein-induced pancreatitis in rats. METHODS: Twenty rats were divided in groups: control and caerulein. A laser-Doppler flowmeter to measure PCBF continuously was used. Blood pressure (BP) and hea [...] rt rate (HR) were monitored. Serum biochemistry analyses were determined. Histopathological study was performed. RESULTS: The PCBF measured a mean of 109.08 ± 14.54% and 68.24 ± 10.47% in control group and caerulein group, respectively. Caerulein group had a mean decrease of 31.75 ± 16.79%. The serum amylase was 1323.70 ± 239.10U.I-1 and 2184.60 ± 700.46U.I-1 in control and caerulein groups, respectively. There was a significant difference in the PCBF (p

  10. The suitability of Doppler flowmeters for use in the minerals-processing industry

    International Nuclear Information System (INIS)

    In this report, six commercially available Doppler flowmeters, which were operated under conditions likely to be encountered in the minerals-processing industry, are evaluated. The effects of the density and particle-size distribution of a flowing slurry and the optimum siting of the flowmeter probe are considered, and the results of tests on the response and linearity of the flowmeters are reported

  11. Laser Doppler Velocimetry Workshop

    Science.gov (United States)

    Owen, R. B.

    1979-01-01

    The potential of laser Doppler velocimetry as a technique for use in mapping flows in the several fluid systems under development for doing research on low-gravity processes, is investigated. Laser Doppler velocimetry techniques, equipment, and applications are summarized.

  12. Laser Doppler projection tomography.

    Science.gov (United States)

    Zeng, Yaguang; Xiong, Ke; Lu, Xuanlong; Feng, Guanping; Han, Dingan; Wu, Jing

    2014-02-15

    We propose a laser Doppler projection tomography (LDPT) method to obtain visualization of three-dimensional (3D) flowing structures. With LDPT, the flowing signal is extracted by a modified laser Doppler method, and the 3D flowing image is reconstructed by the filtered backprojection algorithm. Phantom experiments are performed to demonstrate that LDPT is able to obtain 3D flowing structure with higher signal-to-noise ratio and spatial resolution. Our experiment results display its potentially useful application to develop 3D label-free optical angiography for the circulation system of live small animal models or microfluidic experiments. PMID:24562237

  13. Laser doppler spectroscopy

    International Nuclear Information System (INIS)

    The main objects of this paper will be to review the latest developments in laser Doppler techniques as well as the results of cell electrophoretic studies. Although the first cell mobility measurements were done in physiological saline, it has not been until recently that high resolution Doppler measurements of cells in high salt conditions has become routine. This important technical advance has been due to improvements in electrode materials, electrophoresis chamber designs, and heterodyne optics. These topics are considered in detail in Section IV and Section V. In Section VI various laser Doppler approaches are compared with each other as well as with microscopic, free flow analytic, and density gradient techniques. Particle studies are reviewed in Section VII and blood cell studies in the remaining sections of the paper. (orig.)

  14. Laser Doppler imaging, revisited

    OpenAIRE

    Atlan, Michael; Gross, Michel

    2006-01-01

    We present a detection scheme designed to perform laser Doppler imaging in a wide-field configuration, aimed at slow flows characterization. The optical field which carries a spectral information about the local scatterers dynamic state that results from momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne off-axis digital holography.

  15. Holographic laser Doppler ophthalmoscopy

    OpenAIRE

    Simonutti, Manuel; Paques, Michel; Sahel, José-Alain; Gross, Michel; Samson, Benjamin; Magnain, Caroline; Atlan, Michael

    2010-01-01

    We report laser Doppler ophthalmoscopic fundus imaging in the rat eye with near-IR heterodyne holography. Sequential sampling of the beat of the reflected radiation against a frequency-shifted optical local oscillator is made onto an array detector. Wide-field maps of fluctuation spectra in the 10 Hz to 25 kHz band exhibit angiographic contrasts in the retinal vascular tree without requirement of an exogenous marker.

  16. Laser doppler perfusion imaging

    International Nuclear Information System (INIS)

    Recording of tissue perfusion is important in assessing the influence of peripheral vascular diseases on the microcirculation. This thesis reports on a laser doppler perfusion imager based on dynamic light scattering in tissue. When a low power He-Ne laser beam sequentally scans the tissue, moving blood cells generate doppler components in the back-scattered light. A fraction of this light is detected by a photodetector and converted into an electrical signal. In the processor, a signal proportional to the tissue perfusion at each measurement site is calculated and stored. When the scanning procedure is completed, a color-coded perfusion image is presented on a monitor. To convert important aspects of the perfusion image into more quantitative parameters, data analysis functions are implemented in the software. A theory describing the dependence of the distance between individual measurement points and detector on the system amplification factor is proposed and correction algorithms are presented. The performance of the laser doppler perfusion imager was evaluated using a flow simulator. A linear relationship between processor output signal and flow through the simulator was demonstrated for blood cell concentrations below 0.2%. The median sampling depth of the laser beam was simulated by a Monte Carlo technique and estimated to 235 ?m. The perfusion imager has been used in the clinic to study perfusion changes in port wine stains treated with argon laser and to investigate the intensity and extension of the cutaneous axon reflex response after electrical nerve stimulation. The fact that perfusion can be visualized without touching the tissue implies elimination of sterilization problems, thus simplifying clinical investigations of perfusion in association with diagnosis and treatment of peripheral vascular diseases. 22 refs

  17. Laser Doppler velocimetry primer

    Science.gov (United States)

    Bachalo, William D.

    1985-01-01

    Advanced research in experimental fluid dynamics required a familiarity with sophisticated measurement techniques. In some cases, the development and application of new techniques is required for difficult measurements. Optical methods and in particular, the laser Doppler velocimeter (LDV) are now recognized as the most reliable means for performing measurements in complex turbulent flows. And such, the experimental fluid dynamicist should be familiar with the principles of operation of the method and the details associated with its application. Thus, the goals of this primer are to efficiently transmit the basic concepts of the LDV method to potential users and to provide references that describe the specific areas in greater detail.

  18. Ultrasound propagation in steel piping at electric power plant using clamp-on ultrasonic pulse doppler velocity-profile flowmeter

    International Nuclear Information System (INIS)

    Venturi nozzles are widely used to measure the flow rates of reactor feedwater. This flow rate of nuclear reactor feedwater is an important factor in the operation of nuclear power reactors. Some other types of flowmeters have been proposed to improve measurement accuracy. The ultrasonic pulse Doppler velocity-profile flowmeter is expected to be a candidate method because it can measure the flow profiles across the pipe cross sections. For the accurate estimation of the flow velocity, the incidence angle of ultrasonic entering the fluid should be carefully estimated by the theoretical approach. However, the evaluation of the ultrasound propagation is not straightforward for the several reasons such as temperature gradient in the wedge or mode conversion at the interface between the wedge and pipe. In recent years, the simulation code for ultrasound propagation has come into use in the nuclear field for nondestructive testing. This article analyzes and discusses ultrasound propagation in steel piping and water, using the 3D-FEM simulation code and the Kirchhoff method, as it relates to the flow profile measurements in power plants with the ultrasonic pulse Doppler velocity-profile flowmeter. (author)

  19. Laser Doppler Imaging of Microflow

    CERN Document Server

    Gross, Michel; Leng, Jacques

    2013-01-01

    We report a pilot study with a wide-field laser Doppler detection scheme used to perform laser Doppler anemometry and imaging of particle seeded microflow. The optical field carrying the local scatterers (particles) dynamic state, as a consequence of momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne digital holography, which is used to map the scattered field in the object plane at a tunable frequency with a multipixel detector. We show that wide-field heterodyne laser Doppler imaging can be used for quantitative microflow diagnosis; in the presented study, maps of the first-order moment of the Doppler frequency shift are used as a quantitative and directional estimator of the Doppler signature of particles velocity.

  20. Laser Doppler Imaging of Microflow

    OpenAIRE

    Gross, Michel; Atlan, Michael; Leng, Jacques

    2006-01-01

    We report a pilot study with a wide-field laser Doppler detection scheme used to perform laser Doppler anemometry and imaging of particle seeded microflow. The optical field carrying the local scatterers (particles) dynamic state, as a consequence of momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne digital holography, which is used to map the scattered field in the object plane at a tunable frequency...

  1. Laser Doppler anemometry

    Science.gov (United States)

    Johnson, Dennis A.

    1989-01-01

    The application of laser Doppler anemometry (LDA) to compressible flows is discussed. Specifically, burst-counter and dual-beam LDA systems are addressed. Much has been accomplished with LDA in compressible flows despite the difficulties posed by the high speeds and additionally by the rapid spatial changes in speed or flow direction. The successful application of the technique is difficult because the signal to noise ratios (SNRs) are fairly low even under the best of conditions and highly variable because of variations in particle size and particle location with the sensing volume. The available signal processing is not very effective in discarding signals that are too noisy to provide an accurate velocity measurement. The temptation is to work with particles which are too large to adequately follow the flow but which provide cleaner signals due to increased scattering intensities. For the data to have credibility, some check on the particle response must be made for a given facility and LDA system. The capability, if developed, of being able to determine the size of each particle upon which a measurement is based and the SNR of the corresponding signal burst would be extremely valuable in reducing much of the uncertainty now present in LDA compressible flow measurements.

  2. Diode-Laser Doppler Velocimeter

    Science.gov (United States)

    Getzer, Gregory J.

    1989-01-01

    Diode-laser Doppler velocimeter measures nonintrusively flow of incompressible fluid in narrow tube. New velocimeter rugged, compact, and competitive in cost. Includes three-section optical head mounted on tube containing flow. In slightly different version, beam splitter and mirror used to split laser beam into two beams.

  3. Laser Doppler velocimetry for continuous flow solar-pumped iodine laser system

    Science.gov (United States)

    Tabibi, Bagher M.; Lee, Ja H.

    1991-01-01

    A laser Doppler velocimetry (LDV) system was employed to measure the flow velocity profile of iodide vapor inside laser tubes of 36 mm ID and 20 mm ID. The LDV, which was operated in the forward scatter mode used a low power (15 mW) He-Ne laser beam. Velocity ranges from 1 m/s was measured to within one percent accuracy. The flow velocity profile across the laser tube was measured and the intensity of turbulence was determined. The flow of iodide inside the laser tube demonstrated a mixture of both turbulence and laminar flow. The flowmeter used for the laser system previously was calibrated with the LDV and found to be in good agreement.

  4. Photodynamic effects in laser Doppler anemometry

    International Nuclear Information System (INIS)

    Photodynamic effects were observed for the first time in laser Doppler anemometry: the Doppler frequency shift of light scattered by a particle was found to depend on the action of probe light beams on this particle. (laser applications and other topics in quantum electronics)

  5. Signal validation in laser-Doppler velocimetry

    International Nuclear Information System (INIS)

    Simple models are applied to gain insight into signal validation in laser-Doppler velocimetry and its effects on transit-time broadening. The predictions obtained are compared with measurements of decaying turbulence behind a grid using two techniques. Turbulence levels down to 0.04 percent were measured, a tenfold improvement over previously reported laser-Doppler measurements. 11 references

  6. Analysis of ultrasound propagation in high-temperature nuclear reactor feedwater to investigate a clamp-on ultrasonic pulse doppler flowmeter

    International Nuclear Information System (INIS)

    The flow rate of nuclear reactor feedwater is an important factor in the operation of a nuclear power reactor. Venturi nozzles are widely used to measure the flow rate. Other types of flowmeters have been proposed to improve measurement accuracy and permit the flow rate and reactor power to be increased. The ultrasonic pulse Doppler system is expected to be a candidate method because it can measure the flow profile across the pipe cross section, which changes with time. For accurate estimation of the flow velocity, the incidence angle of ultrasound entering the fluid should be estimated using Snell's law. However, evaluation of the ultrasound propagation is not straightforward, especially for a high-temperature pipe with a clamp-on ultrasonic Doppler flowmeter. The ultrasound beam path may differ from what is expected from Snell's law due to the temperature gradient in the wedge and variation in the acoustic impedance between interfaces. Recently, simulation code for ultrasound propagation has come into use in the nuclear field for nondestructive testing. This article analyzes and discusses ultrasound propagation, using 3D-FEM simulation code plus the Kirchhoff method, as it relates to flow profile measurement in nuclear reactor feedwater with the ultrasonic pulse Doppler system. (author)

  7. Self-mixing laser Doppler vibrometer

    Science.gov (United States)

    Scalise, Lorenzo; Paone, Nicola

    2000-05-01

    In this paper, an extremely small, simple and economic laser Doppler sensor is presented. It simply consists of a laser diode and of an optical system composed by two lenses in order to focus the laser light. The sensor is able to measure velocity and it is based on the self-mixing effect that occurs in a semiconductor laser diode when the emitted radiation is back reflected toward the cavity and then re- introduced inside. The velocity is calculated measuring the position of the frequency peak on the frequency spectrum of the intensity signal generated by the photodiode present inside the laser diode when modulated by feedback light coming from the moving scattering particles. The laser Doppler self-mixing velocimeter has been statically calibrated, using a rotating disk covered with white paper. The sensor has then been dynamically characterized using an electro-magnetic shaker and a Laser Doppler Vibrometer as reference.

  8. Bone tissue phantoms for optical flowmeters at large interoptode spacing generated by 3D-stereolithography.

    Science.gov (United States)

    Binzoni, Tiziano; Torricelli, Alessandro; Giust, Remo; Sanguinetti, Bruno; Bernhard, Paul; Spinelli, Lorenzo

    2014-08-01

    A bone tissue phantom prototype allowing to test, in general, optical flowmeters at large interoptode spacings, such as laser-Doppler flowmetry or diffuse correlation spectroscopy, has been developed by 3D-stereolithography technique. It has been demonstrated that complex tissue vascular systems of any geometrical shape can be conceived. Absorption coefficient, reduced scattering coefficient and refractive index of the optical phantom have been measured to ensure that the optical parameters reasonably reproduce real human bone tissue in vivo. An experimental demonstration of a possible use of the optical phantom, utilizing a laser-Doppler flowmeter, is also presented. PMID:25136496

  9. Laser Doppler flowmetry in microvascular surgery

    OpenAIRE

    Adrichem, L.N.A. van

    1992-01-01

    In the first part of this thesis, describing clinical and experimental studies, laser Doppler flowmetry is evaluated as diagnostic tool to assess tissue microcirculation after various microvascular operations. The second part concerns the application of laser Doppler flowmetry to investigate and to objectivate the negative effects of cigarette smoking upon the microcirculation under normal circumstances as well as after microvascular operative procedures. Success of plastic ...

  10. Doppler velocimeter for laser accelerated targets

    International Nuclear Information System (INIS)

    A doppler velocimeter utilizing a spectrograph and a short pulse laser probe is described which provides good spatial (20 ?m) and subnanosecond temporal resolution. This system has been used to measure the velocity profiles of targets ablatively accelerated to very high velocities by a high power laser beam. A unique aspect of this velocimeter is that the doppler wavelength shifts are measured directly rather than employing interferometric techniques

  11. Laser Doppler And Range Systems For Spacecraft

    Science.gov (United States)

    Kinman, P. W.; Gagliardi, R. M.

    1990-01-01

    Report discusses two types of proposed laser systems containing active transponders measuring distance (range) and line-of-sight velocity (via Doppler effect) between deep space vehicle and earth-orbiting satellite. Laser system offers diffraction advantage over microwave system. Delivers comparable power to distant receiver while using smaller transmitting and receiving antennas and less-powerful transmitter. Less subject to phase scintillations caused by passage through such inhomogeneous media as solar corona. One type of system called "incoherent" because range and Doppler measurements do not require coherence with laser carrier signals. Other type of system called "coherent" because successful operation requires coherent tracking of laser signals.

  12. Series of calibration tests at national standard loops and industrial application experiences of new type flow-metering system by ultrasonic pulse-doppler profile-velocimetry

    International Nuclear Information System (INIS)

    Highly-accurate measurements are required to control the thermal outputs for reactor feedwater flow rates. Calibration tests for flowmeters such as time-of-flight (TOF) ultrasonic flow meters are conducted to assure their accuracy in measurements at standard loops, where flow profile factors, which adjust measurand to real flow rates, are determined usually by conducting calibration tests under ambient flow conditions. As nuclear power plants are aging, readings of flowmeters for reactor feedwater systems drift due to the changes of flow profiles. The causes of those deviations are affected by the change of wall roughness of inner surface of pipings, and those changes of flow patterns lead to large errors in measurements. Therefore, it is still in suspicion if its high accuracy on adjusting measurand by profile factors is traceable against the national standard, and moreover, we have to consider the difference of flow configuration between the flow standard and measurement position on-site. The difference of facilities for measurement conditions can be considered as the concept of 'Facility Factor' and the 'Profile Factor' is not sufficient for correcting the meter reading. It is so discussed that measurement of velocity profile on-site is essential. We proposed the new type of flowmeter called UdFlow/UDF, ultrasonic pulse-Doppler flowmeter, which can measure instantaneously-determined flow-velocity profiles and eliminate the effect of deviated flow profile from expeceffect of deviated flow profile from expected ideal one. Series of calibration tests of UdFlow were conducted at the national standard loops in Mexico, CENAM (The Centro National de Metrologia) and in USA, NIST (National Institute of Standard and Technology) in order to evaluate the accuracy of the flowmeter. Four ultrasonic transducers are mounted on the surface of stainless steel piping circumferentially with the diameters of 100mm and 200mm to measure four velocity profiles. The calibration tests found a deviation better than 0.3% between the two devices in terms of the average of the values recorded by six rounds of each measurement. From the results of measurement conducted with Reynolds number varied, it was found that the overall average deviation between the two devices was better than 0.3%. (author)

  13. Laser Doppler distance sensor using phase evaluation.

    Science.gov (United States)

    Günther, P; Pfister, T; Büttner, L; Czarske, J

    2009-02-16

    This paper presents a novel optical sensor which allows simultaneous measurements of axial position and tangential velocity of moving solid state objects. An extended laser Doppler velocimeter setup is used with two slightly tilted interference fringe systems. The distance to a solid state surface can be determined via a phase evaluation. The phase laser Doppler distance sensor offers a distance resolution of 150 nm and a total position uncertainty below 1 microm. Compared to conventional measurement techniques, such as triangulation, the distance resolution is independent of the lateral surface velocity. This advantage enables precise distance and shape measurements of fast rotating surfaces. PMID:19219164

  14. Interface Circuit for Laser Doppler Velocimeters

    Science.gov (United States)

    Harrison, Dean R.; Brown, James L.

    1987-01-01

    New circuit displays more information to user and provides higher data-collection rates. Interface circuit facilitates coupling of laser-Doppler-velocimeter outputs to computer for analysis. Enables user to select variety of intermediate data-processing options, including clock frequency, coincidence channel combinations, coincidence times, dead times, digital or analog output, and channels to be analyzed.

  15. Atmospheric laser Doppler velocimetry - An overview

    Science.gov (United States)

    Bilbro, J. W.

    1980-01-01

    Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.

  16. Laser Doppler visualisation of the velocity field

    International Nuclear Information System (INIS)

    A method for the laser Doppler real-time visualisation of the velocity field of moving media was developed. The method is based on the optical frequency demodulation of the optical fields forming the image of the investigated cross section. The visualiser was constructed on the basis of a semiconfocal optical cavity. The results of the visualisation of the velocity field of a vortical flow in a cylindrical channel are presented. (laser applications and other topics in quantum electronics)

  17. Doppler velocimeter for laser accelerated targets

    International Nuclear Information System (INIS)

    A doppler velocimeter utilizing a spectrograph and a short-pulse laser probe is described which provides good spatial (20 ?m) and subnanosecond temporal resolution. This system has been used to measure the velocity profiles of targets ablatively accelerated to very high velocities by a high-power laser beam. In comparison to systems employing interferometric techniques, this velocimeter significantly relaxes requirements on the target surface being examined and the time resolution needed to measure velocities of rapidly accelerating surfaces

  18. Sub miniaturized laser doppler velocimeter sensor

    Science.gov (United States)

    Gharib, Morteza (Inventor); Modaress, Darius (Inventor); Taugwalder, Frederic (Inventor)

    2003-01-01

    A miniaturized laser Doppler velocimeter is formed in a housing that is preferably 3 mm in diameter or less. A laser couples light to a first diffractive optical element that is formed on the fiber end. The light is coupled to a lens that also includes a diffractive optical element. The same lens is also used to collect receive light, and receives includes another diffractive optical element to collect that received light.

  19. Laser Doppler measurement techniques for spacecraft

    Science.gov (United States)

    Kinman, Peter W.; Gagliardi, Robert M.

    1986-01-01

    Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

  20. Laser Doppler measurement of cutaneous blood flow

    International Nuclear Information System (INIS)

    Laser Doppler velocimetry is an instrument system which has only recently been applied to the evaluation and quantitation of perfusion in the micro-vascular bed. The instrument is based on the Doppler principle, but uses low power laser light rather than the more commonly used ultrasound, and has a sample volume of approximately 1 mm/sup 3/. As it is non-invasive, it can be used on any skin surface or exposed microvascular bed and provides a continuous semi-quantitative measure of microcirculatory perfusion, it has a number of advantages as compared to other cutaneous blood flow measurement techniques. Initial studies have shown that it is easily used, and it has demonstrated good correlation with both xenon radio-isotope clearance and microsphere deposition techniques. Areas of current evaluation and utilization are in most major areas of medicine and surgery and include plastic, vascular and orthopaedic surgery, dermatology, gastro-enterology, rheumatology, burns and anaesthesiology

  1. Fish embryo multimodal imaging by laser Doppler digital holography

    CERN Document Server

    Verrier, Nicolas; Picart, Pascal; Gross, Michel

    2015-01-01

    A laser Doppler imaging scheme combined to an upright microscope is proposed. Quantitative Doppler imaging in both velocity norm and direction, as well as amplitude contrast of either zebrafish flesh or vasculature is demonstrated.

  2. Diffractive beam splitter for laser Doppler velocimetry

    OpenAIRE

    Schmidt, J; Völkel, R.; Stork, W; Sheridan, John T.; Schwider, J.; Streibl, N.; Durst, F

    1992-01-01

    A miniaturized sensor head for the optical measurement of velocities of fluids based on laser Doppler velocimetry is demonstrated. Holographic optical elements mounted on a glass substrate are used for beam splitting and deflection. Volume holograms in dichromated gelatin exhibit good optical efficiency (75% transmission of a cascade of two holographic optical elements). With diffractive devices one can achieve achromatic behavior that makes the sensor insensitive to wavelength drifts or mode...

  3. Utilization of laser Doppler flowmetry and tissue spectrophotometry for burn depth assessment using a miniature swine model.

    Science.gov (United States)

    Lotter, Oliver; Held, Manuel; Schiefer, Jennifer; Werner, Ole; Medved, Fabian; Schaller, Hans-Eberhard; Rahmanian-Schwarz, Afshin; Jaminet, Patrick; Rothenberger, Jens

    2015-01-01

    Currently, the diagnosis of burn depth is primarily based on a visual assessment and can be dependent on the surgeons' experience. The goal of this study was to determine the ability of laser Doppler flowmeter combined with a tissue spectrophotometer to discriminate burn depth in a miniature swine burn model. Burn injuries of varying depth, including superficial-partial, deep-partial, and full thickness, were created in seven Göttingen minipigs using an aluminium bar (100?°C), which was applied to the abdominal skin for periods of 1, 3, 6, 12, 30, and 60 seconds with gravity alone. The depth of injury was evaluated histologically using hematoxylin and eosin staining. All burns were assessed 3 hours after injury using a device that combines a laser light and a white light to determine blood flow, hemoglobin oxygenation, and relative amount of hemoglobin. The blood flow (41 vs. 124 arbitrary units [AU]) and relative amount of hemoglobin (32 vs. 52 AU) were significantly lower in full thickness compared with superficial-partial thickness burns. However, no significant differences in hemoglobin oxygenation were observed between these depths of burns (61 vs. 60%). These results show the ability of laser Doppler flowmeter and tissue spectrophotometer in combination to discriminate between various depths of injury in the minipig model, suggesting that this device may offer a valuable tool for burn depth assessment influencing burn management. PMID:25487000

  4. Parallax effects in laser Doppler spectroscopy

    International Nuclear Information System (INIS)

    Parallax effects in laser Doppler spectroscopy, associated with the variation of the scattering angle during motion of a particle through the probed volume, were investigated by a numerical simulation method based on the Mie scattering theory. It was found that, in general, the shifts of the spectral profile parameters (the average frequency, broadening, asymmetry, and kurtosis) become significant as the parallax number N??=(2/?)?? (? is the angular size of the probed volume, ? = ?d/? is the relative particle diameter) increases. The anomalous ranges of the parameters of the particle and of the optical system, in which marked distortions (such as the polymodal nature and the splitting of the spectral profile) are observed even for a low parallax number (N?? || 1), were discovered. (laser applications and other topics in quantum electronics)

  5. Laser Doppler velocimetry and its application to turbulent flow measurements

    International Nuclear Information System (INIS)

    The present state of development is reviewed of laser Doppler velocimetry, a new method of fluid flow characteristic measurement. The physical principles involved, the classification of the optical schemes utilized, the typical experimental arrangements, the nature of the laser Doppler velocimeter signal and methods of signal analysis are discussed. The comprehensive bibliography contains more than 300 references from 1964 to 1974. (author)

  6. Widefield laser doppler velocimeter: development and theory.

    Energy Technology Data Exchange (ETDEWEB)

    Hansche, Bruce David; Reu, Phillip L.; Massad, Jordan Elias

    2007-03-01

    The widefield laser Doppler velocimeter is a new measurement technique that significantly expands the functionality of a traditional scanning system. This new technique allows full-field velocity measurements without scanning, a drawback of traditional measurement techniques. This is particularly important for tests in which the sample is destroyed or the motion of the sample is non-repetitive. The goal of creating ''velocity movies'' was accomplished during the research, and this report describes the current functionality and operation of the system. The mathematical underpinnings and system setup are thoroughly described. Two prototype experiments are then presented to show the practical use of the current system. Details of the corresponding hardware used to collect the data and the associated software to analyze the data are presented.

  7. Laser Doppler vibrometry: new ENT applications

    Science.gov (United States)

    Stasche, Norbert; Baermann, M.; Kempe, C.; Hoermann, Karl; Foth, Hans-Jochen

    1996-12-01

    Common audiometry often does not really allow a reliable and objective differential diagnosis of hearing disorders such as otosclerosis, adhesive otitis, ossicular interruption or tinnitus, even though several methods might be used complementarily. In recent years, some experimental studies on middle ear mechanics established laser Doppler vibrometry (LDV) as a useful method allowing objective measurement of human tympanic membrane displacement. The present study on LDV investigated the clinical use of this new method under physiological conditions. LDV proved to be a fast, reproducible, non-invasive and very sensitive instrument to characterize ear-drum vibrations in various middle ear dysfunctions, except in tinnitus patients. For future applications, improved optical characteristics of the vibrometer might result in a better differential diagnosis of subjective and objective tinnitus, otoacoustic emissions or Morbus Meniere.

  8. A borescopic laser Doppler velocimetry probe

    Science.gov (United States)

    O'Brien, Kory T.; Ölçmen, Semih M.

    2014-07-01

    We present a miniature, fiber-optic, single-velocity-component laser Doppler velocimetry (LDV) probe for measurement in flows where access is very limited. The main probe neck is 7?mm in diameter. The probe operates in the backscatter mode. The borescopic design of the probe allows the neck of the probe to be as long as is needed to access remote locations. The neck length of the probe is 15.24?cm and was designed to make measurements at 30?mm away from the probe’s tip. The probe was tested in two free-jet flows, (i) pipe jet flow and (ii) convergent nozzle jet flow, to demonstrate the working principle of the probe.

  9. Coherent Detection in Laser Doppler Velocimeters

    DEFF Research Database (Denmark)

    Hanson, Steen Grüner

    1974-01-01

    The possibility of heterodyning between electromagnetic waves scattered by particles separated in space is explained from a classical point of view and from a quantum mechanical point of view. The last description being carried out using only the Heisenberg uncertainty principle and a rather coarse, but intelligible particle picture of electromagnetic waves. The analysis is carried out with special emphasis on the heterodyning process in the laser Doppler velocimeter (LDV) because the main purpose of this article is to provide a better understanding of this instrument. An aid for this purpose is the evaluation of a visual comprehensive interference pattern (Moiré pattern), which furthermore reveals some important features of the optical set-up.

  10. Sub-Doppler laser cooling of potassium atoms

    CERN Document Server

    Landini, M; Carcagni', L; Trypogeorgos, D; Fattori, M; Inguscio, M; Modugno, G

    2011-01-01

    We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of systems and an adiabatic ramping of the laser parameters allows to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25(3)microK and 47(5)microK in high-density samples of the two isotopes 39K and 41K, respectively. Our findings will find application to other atomic systems.

  11. Sub-Doppler laser cooling of potassium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Landini, M. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); INFN, Sezione di Firenze, I-50019 Sesto Fiorentino (Italy); Dipartimento di fisica, Universita di Trento, I-38123 Povo (Trento) (Italy); Roy, S.; Carcagni, L.; Trypogeorgos, D. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); Fattori, M.; Inguscio, M.; Modugno, G. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); INFN, Sezione di Firenze, I-50019 Sesto Fiorentino (Italy)

    2011-10-15

    We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25{+-}3 {mu}K and 47{+-}5 {mu}K in high-density samples of the two isotopes {sup 39}K and {sup 41}K, respectively. Our findings should find application to other atomic systems.

  12. Laser Doppler anemometer signal processing for blood flow velocity measurements

    Science.gov (United States)

    Borozdova, M. A.; Fedosov, I. V.; Tuchin, V. V.

    2015-03-01

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented.

  13. Sub-Doppler laser cooling of potassium atoms

    International Nuclear Information System (INIS)

    We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25±3 ?K and 47±5 ?K in high-density samples of the two isotopes 39K and 41K, respectively. Our findings should find application to other atomic systems.

  14. Sub-Doppler laser cooling of potassium atoms

    OpenAIRE

    Landini, M.; Roy, S.; Carcagn Xec, L.; Trypogeorgos, D.; Fattori, M.; Inguscio, M.; Modugno, G.

    2011-01-01

    We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of systems and an adiabatic ramping of the laser parameters allows to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25(3)microK and 47(5)microK in high-density...

  15. Bone tissue phantoms for optical flowmeters at large interoptode spacing generated by 3D-stereolithography

    OpenAIRE

    Binzoni, Tiziano; Torricelli, Alessandro; Giust, Remo; Sanguinetti, Bruno; Bernhard, Paul; Spinelli, Lorenzo

    2014-01-01

    A bone tissue phantom prototype allowing to test, in general, optical flowmeters at large interoptode spacings, such as laser-Doppler flowmetry or diffuse correlation spectroscopy, has been developed by 3D-stereolithography technique. It has been demonstrated that complex tissue vascular systems of any geometrical shape can be conceived. Absorption coefficient, reduced scattering coefficient and refractive index of the optical phantom have been measured to ensure that the optical parameters r...

  16. Application of laser Doppler velocimeter to chemical vapor laser system

    Science.gov (United States)

    Gartrell, Luther R.; Hunter, William W., Jr.; Lee, Ja H.; Fletcher, Mark T.; Tabibi, Bagher M.

    1993-01-01

    A laser Doppler velocimeter (LDV) system was used to measure iodide vapor flow fields inside two different-sized tubes. Typical velocity profiles across the laser tubes were obtained with an estimated +/-1 percent bias and +/-0.3 to 0.5 percent random uncertainty in the mean values and +/-2.5 percent random uncertainty in the turbulence-intensity values. Centerline velocities and turbulence intensities for various longitudinal locations ranged from 13 to 17.5 m/sec and 6 to 20 percent, respectively. In view of these findings, the effects of turbulence should be considered for flow field modeling. The LDV system provided calibration data for pressure and mass flow systems used routinely to monitor the research laser gas flow velocity.

  17. Fiberoptic laser-Doppler anemometer for industrial flow measurement

    International Nuclear Information System (INIS)

    The paper describes laser-Doppler anemometers whose sending and receiving lenses are decoupled from the rest of the optics by means of glassfibers. This technique yields robust fiber optical probes, which work under industrial conditions. Their application to practical flows is shown and preliminary measurements are presented. The measurements indicate that fiber optical laser-Doppler systems are not only easy to handle, they can also yield LDA-signal quality comparable to conventional systems. (orig.)

  18. Blood flow measurement by laser Doppler method in orofacial region

    OpenAIRE

    Grga ?urica; Dželetovi? Bojan; Živkovi? Slavoljub; Kršljak Elena

    2010-01-01

    Laser Doppler is a noninvasive, objective, reproducible and painless method for measuring blood flow in tissue microcirculation. This method is based on the Doppler effect, the change in frequency of light reflecting from blood cells in motion. Light from helium-neon laser through optical fibers and probes is directed to the surface of the tissue in which the flow is measured. Light portion is reflected from the cells in motion and changes the frequency while another portion is reflecte...

  19. Measurement of Water Flowing Velocity Using Laser Doppler Velocimetry Technique

    International Nuclear Information System (INIS)

    A Doppler laser differential method was used to measure the velocity of water flowing in a transparent glass tube in two cases : 1) a tap water and 2) a water pumped by a fish tank pump, the water had been colored with potassium permanganate (KMnO4). Several measurements of the water velocity were carried out manually and with Doppler laser differential method for both cases. The comparison between these measurements shows a reasonable agreement. (Authors)

  20. Muscle activity characterization by laser Doppler Myography

    International Nuclear Information System (INIS)

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin

  1. Evaluating microcirculation by pulsatile laser Doppler signal

    Energy Technology Data Exchange (ETDEWEB)

    Chao, P T [Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (China); Department of Physics, National Taiwan Normal University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Jan, M Y [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Hsiu, H [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Department of Electrical Engineering, Yuan-ze University, Chun-Li, Taiwan (China); Hsu, T L [Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Wang, W K [Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China); Wang, Y Y Lin [Department of Physics, National Taiwan Normal University, Taipei, Taiwan (China); Biophysics Lab, Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan (China)

    2006-02-21

    Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 {+-} 5.54 ms, mean {+-} SD) than in WKY (76.92 {+-} 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 {+-} 1.98 ms) than in WKY (58.02 {+-} 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods.

  2. Evaluating microcirculation by pulsatile laser Doppler signal

    International Nuclear Information System (INIS)

    Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 ± 5.54 ms, mean ± SD) than in WKY (76.92 ± 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 ± 1.98 ms) than in WKY (58.02 ± 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods

  3. Miniature Laser Doppler Velocimeter for Measuring Wall Shear

    Science.gov (United States)

    Gharib, Morteza; Modarress, Darius; Forouhar, Siamak; Fourguette, Dominique; Taugwalder, Federic; Wilson, Daniel

    2005-01-01

    A miniature optoelectronic instrument has been invented as a nonintrusive means of measuring a velocity gradient proportional to a shear stress in a flow near a wall. The instrument, which can be mounted flush with the wall, is a variant of a basic laser Doppler velocimeter. The laser Doppler probe volume can be located close enough to the wall (as little as 100 micron from the surface) to lie within the viscosity-dominated sublayer of a turbulent boundary layer. The instrument includes a diode laser, the output of which is shaped by a diffractive optical element (DOE) into two beams that have elliptical cross sections with very high aspect ratios.

  4. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser

    Science.gov (United States)

    Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung

    2012-09-01

    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO2 laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  5. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser

    International Nuclear Information System (INIS)

    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO2 laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  6. Measurement of microvascular blood flow in cancellous bone using laser Doppler flowmetry and 133Xe-clearance

    International Nuclear Information System (INIS)

    Blood flow in cancelleous bone with varying vascular density was investigated simultaneously with Laser Doppler Flowmeter (LDF) and 113Xe-clearance. The cancellous bone subapical to 2 contralateral incisors in the mandibles of 17 young pigs was used as an experimental model. Light from a 2 mW He-Ne-laser was guided through an optical fibre to a flowmeter probe. Stainless steel probe-holders firmly inserted in the pulpal canals of the two incisors served as the probe entrance to cancellous bone for blood flow recording. Due to the Doppler effect, the light scattered by circulating blood cells undergoes a frequency shift. The back-scattered light picked up by optical fibres in the probe, was guided to a photosensitive device, where it was demodulated. After signal processing, a signal referred to as the Blood Flow Value (BFV) was recorded on a pen recorder. Rhythmical variations (vasomotion) in BFV with frequencies from 2-11 cycles/min were observed in 6% of recordings made initially after probeholder implantation, and in 34% of the recordings made 5 weeks later. On this occasion, a marked increase in BFV was recorded. Histological examination showed increased vascularity in the bone tissue. The reproducibility error of LDF was 7.4% and temporal changes in BFV, apart from vasomotion, were 8.3%, provided no injections or manipulations of the probe were made. Spatial variations in BFV were found to be related to the vascular density. 2 successive recordings by cular density. 2 successive recordings by LDF from the same bone area were highly correlated (r=0.98). The corresponding figure for 2 logarithmic decay rates of locally injected 133Xe was 0.76. No correlation between BFV and 133Xe-clearance could be demonstrated. (author)

  7. Blood flow measurement by laser Doppler method in orofacial region

    Directory of Open Access Journals (Sweden)

    Grga ?urica

    2010-01-01

    Full Text Available Laser Doppler is a noninvasive, objective, reproducible and painless method for measuring blood flow in tissue microcirculation. This method is based on the Doppler effect, the change in frequency of light reflecting from blood cells in motion. Light from helium-neon laser through optical fibers and probes is directed to the surface of the tissue in which the flow is measured. Light portion is reflected from the cells in motion and changes the frequency while another portion is reflected from the static tissue maintaining the same frequency as the initial light. The total reflected light, with changed and original frequency, reaches photo detector in the same probe where the emitter is and it is transformed into electrical impulse. In the orofacial region the laser Doppler method is used to examine blood flow in the mandible, teeth pulp and masticator muscles. A significant drawback of the laser Doppler method is its sensitivity to the ambient conditions during measuring and the fact that blood flow is measured in all blood vessels of examined microregion. Therefore, the circulation of isolated individual blood vessels can not be monitored. Laser Doppler method can give reliable indicators of blood flow in mouth tissue and method is acceptable for the patients.

  8. Processor operated correlator with applications to laser Doppler signals

    OpenAIRE

    Bisgaard, C.; Johnsen, B.; Hassager, Ole

    2009-01-01

    A 64-channel correlator is designed with application to the processing of laser Doppler anemometry signals in the range 200 Hz to 250 kHz. The correlator is processor operated to enable the consecutive sampling of 448 correlation functions at a rate up to 500 Hz. Software is described to identify a Doppler frequency from each correlation and the system is especially designed for transient flow signals. Doppler frequencies are determined with an accuracy of about 0.1%. Review of Scientific Ins...

  9. Vocal fold vibration measurements using laser Doppler vibrometry

    OpenAIRE

    Chan, Alfred; Mongeau, Luc; Kost, Karen

    2013-01-01

    The objective of this study was to measure the velocity of the superior surface of human vocal folds during phonation using laser Doppler vibrometry (LDV). A custom-made endoscopic laser beam deflection unit was designed and fabricated. An in vivo clinical experimental procedure was developed to simultaneously collect LDV velocity and video from videolaryngoscopy. The velocity along the direction of the laser beam, i.e., the inferior-superior direction, was captured. The velocity was synchron...

  10. Non-intrusive Shock Measurements Using Laser Doppler Vibrometers

    Science.gov (United States)

    Statham, Shannon M.; Kolaini, Ali R.

    2012-01-01

    Stud mount accelerometers are widely used by the aerospace industry to measure shock environments during hardware qualification. The commonly used contact-based sensors, however, interfere with the shock waves and distort the acquired signature, which is a concern not actively discussed in the community. To alleviate these interference issues, engineers at the Jet Propulsion Laboratory are investigating the use of non-intrusive sensors, specifically Laser Doppler Vibrometers, as alternatives to the stud mounted accelerometers. This paper will describe shock simulation tests completed at the Jet Propulsion Laboratory, compare the measurements from stud mounted accelerometers and Laser Doppler Vibrometers, and discuss the advantages and disadvantages of introducing Laser Doppler Vibrometers as alternative sensors for measuring shock environments.

  11. Fano-Doppler laser cooling of hybrid nanostructures.

    Science.gov (United States)

    Ridolfo, Alessandro; Saija, Rosalba; Savasta, Salvatore; Jones, Philip H; Iatì, Maria Antonia; Maragò, Onofrio M

    2011-09-27

    Laser cooling the center-of-mass motion of systems that exhibit Fano resonances is discussed. We find that cooling occurs for red or blue detuning of the laser frequency from resonance depending on the Fano factor associated with the resonance. The combination of the Doppler effect with the radiation cross-section quenching typical of quantum interference yields temperatures below the conventional Doppler limit. This scheme opens perspectives for controlling the motion of mesoscopic systems such as hybrid nanostructures at the quantum regime and the exploration of motional nonclassical states at the nanoscale. PMID:21806014

  12. Laser Doppler velocimetry based on the photoacoustic effect in a CO2 laser

    International Nuclear Information System (INIS)

    We report a simple laser Doppler velocimeter in which the photoacoustic effect was used to measure the rotation wheel speed. A Doppler signal, caused by mixing a returning wave with an originally existing wave inside the CO2 laser cavity, was detected using a microphone in the laser tube. Frequency of the microphone output was in proportion to the rotation speed of a wheel and is dependent on the cosine of the angle between the direction of the laser beam and tangent of wheel velocity. A Doppler-shifted frequency as high as 34 kHz was detected using this method. A frequency response of a few megahertz is expected from the laser Doppler velocimeter based on the photoacoustic effect in a CO2 laser by using a wider bandwidth microphone

  13. Holographic laser Doppler imaging of microvascular blood flow

    CERN Document Server

    Magnain, C; Boucneau, T; Simonutti, M; Ferezou, I; Rancillac, A; Vitalis, T; Sahel, J A; Paques, M; Atlan, M

    2014-01-01

    We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency shifted reference beam, permits frequency selective imaging in the radiofrequency range. These Doppler images are acquired with an off axis Mach Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse method analysis of local first order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1 to 10 millimeters per second range in vitro ...

  14. Effective particle size range in laser-Doppler anemometry

    International Nuclear Information System (INIS)

    The present paper points out that all existing laser-Doppler anemometer systems do not only operate within a finite range of Doppler frequencies but also work within a relatively narrow range of signal amplitudes. It is shown that this corresponds to a finite, and usually to an extremely small, range of particle diameters which contributes to the final LDA measurements. The investigation results in conclusions regarding optimum particle size distributions for laser-Doppler anemometry. If fluid velocity measurements are attempted rather than particle velocity measurements, the particles still have to satisfy well known size requirements that are flow, fluid and particle density dependent. The experimental study employs a combined optical system for simultaneous measurements of particle velocity, particle size and particle concentration. The system is used to measure those particles of a spectrum of oil droplets that contribute to the validated signal output of counter and transient recorder based LDA-electronic signal processing systems. (orig./HP)

  15. Flow profile study using miniature laser-Doppler velocimetry

    Science.gov (United States)

    Booij, W. E.; de Jongh, A.; de Mul, F. F. M.

    1995-11-01

    We present a physics experiment, in which laser-Doppler velocimetry is used to make first-year university physics students realize that the idealized solutions offered by standard text books seldom are applicable without corrections, which often are numerical. This is demonstrated by carefully measuring and calculating the flow profile in a rectangular pipe.

  16. Dual beam translator for use in Laser Doppler anemometry

    Science.gov (United States)

    Brudnoy, David M. (Albany, NY)

    1987-01-01

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  17. Methodology and reproducibility of bidirectional laser Doppler velocimetry

    International Nuclear Information System (INIS)

    Bidirectional laser Doppler velocimetry in conjunction with monochromatic fundus photography allows non invasive measurement of retinal blood velocity. We have shown that it gives reproducible results in humans and experimental animals which agree well with those of the radioactively labelled microsphere technique. (author)

  18. Alignment technique for three-dimensional laser Doppler anemometry

    International Nuclear Information System (INIS)

    Three-dimensional laser Doppler anemometry is a powerful, non-intrusive measurement technique. The high data rate point measurement allows direct quantification of turbulence quantities. However, for this type of study, a very high level of laser beam alignment is required; without good alignment only mean flow measurements are possible. We report here on an alignment procedure that is simple and cost-effective, yet results in much higher data rates than traditional, pinhole-based methods. (technical design note)

  19. Coherent Doppler Laser Radar: Technology Development and Applications

    Science.gov (United States)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through headwind minimization. In addition to the airborne and space platforms, a coherent Doppler laser radar system in an unmanned aerial vehicle (UAV) could provide battlefield weather and target identification.

  20. Application of Hilbert-Huang transform to laser Doppler velocimeter

    Science.gov (United States)

    Xiaoming, Nie; Jian, Zhou; Xingwu, Long

    2012-10-01

    A new method based on Hilbert-Huang transform is proposed to analyze the laser Doppler signal with a large acceleration. The Doppler signal is decomposed into several Intrinsic Mode Functions (IMFs) via empirical mode decomposition (EMD). And the Hilbert transform is used to compute the instantaneous frequency. The vehicle velocity parameter is estimated by taking linear fitting on the instantaneous frequency of the relevant IMF. The simulation results show that the HHT-based method is quite useful for the LDV that offers velocity parameter to the vehicle self-contained navigation system when the vehicle moves at a large acceleration.

  1. Scanning laser doppler velocimeter using iodine iodine-vapor discriminator

    International Nuclear Information System (INIS)

    This paper presents a scanning laser doppler velocimeter (SLDV) that is able to measure the velocity over two dimensions. SDV can be used to measure the 2-D velocity of a rotating disk or fluid by using the molecular iodine absorption line (1109) as the frequency discrimination to determine the doppler shift of the target backscattering. The laser source, a narrow line-width Nd:YAG laser at the second harmonic, is frequency locked to the 1109 line as the frequency reference by a digital PID servo with the frequency jitter less than 1 MHz for arbitrarily long periods. Experimental results show that SDV is capable of mapping the speed vector of the target, and the measurement uncertainty of the rotating disk speed is less than 0.25 m/s.

  2. Three-dimensional laser cooling at the Doppler limit

    CERN Document Server

    Chang, Rockson; Bouton, Quentin; Fang, Yami; Klafka, Tobias; Audo, Kevin; Aspect, Alain; Westbrook, Christoph I; Clément, David

    2014-01-01

    Many predictions of the theory of Doppler cooling of 2-level atoms, notably the celebrated minimum achievable temperature $T_D=\\hbar \\Gamma/2 k_B$, have never been verified in a three-dimensional geometry. Here, we show that, despite their degenerate level structure, we can use Helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the sensitivity of optical molasses to a power imbalance in the laser beams, finding excellent agreement with the Doppler theory. We show that the special properties of Helium, particularly its small mass and narrow transition linewidth, prevent effective sub-Doppler cooling with red-detuned optical molasses.

  3. Three-dimensional laser cooling at the Doppler limit

    Science.gov (United States)

    Chang, R.; Hoendervanger, A. L.; Bouton, Q.; Fang, Y.; Klafka, T.; Audo, K.; Aspect, A.; Westbrook, C. I.; Clément, D.

    2014-12-01

    Many predictions of Doppler-cooling theory of two-level atoms have never been verified in a three-dimensional geometry, including the celebrated minimum achievable temperature ? ? /2 kB , where ? is the transition linewidth. Here we show that, despite their degenerate level structure, we can use helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the sensitivity of optical molasses to a power imbalance in the laser beams, finding excellent agreement with Doppler theory. We show that the special properties of helium, particularly its small mass and narrow transition linewidth, prevent effective sub-Doppler cooling with red-detuned optical molasses. This discussion can be generalized to identify when a given species is likely to be subject to the same limitation.

  4. Influence of laser frequency noise on scanning Fabry-Perot interferometer based laser Doppler velocimetry

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2014-01-01

    n this work, we study the performance of a scanning Fabry-Perot interferometer based laser Doppler velocimeter (sFPILDV) and compare two candidate 1.5 um single-frequency laser sources for the system – a fiber laser (FL) and a semiconductor laser (SL). We describe a straightforward calibration procedure for the sFPI-LDV and investigate the effect of different degrees of laser frequency noise between the FL and the SL on the velocimeter’s performance

  5. Influence of laser frequency noise on scanning Fabry-Perot interferometer based laser Doppler velocimetry

    Science.gov (United States)

    Rodrigo, Peter John; Pedersen, Christian

    2014-03-01

    In this work, we study the performance of a scanning Fabry-Perot interferometer based laser Doppler velocimeter (sFPILDV) and compare two candidate 1.5 um single-frequency laser sources for the system - a fiber laser (FL) and a semiconductor laser (SL). We describe a straightforward calibration procedure for the sFPI-LDV and investigate the effect of different degrees of laser frequency noise between the FL and the SL on the velocimeter's performance.

  6. Three component laser Doppler measurements in an axisymmetric jet

    Science.gov (United States)

    Kuhlmann, John M.; Gross, Robert W.

    1989-01-01

    A three-component laser Doppler anemometer (LDA) was used to acquire a detailed set of three-dimensional mean and fluctuating velocity measurements in a low-speed air jet entering a stagnant ambient, over the first 20 jet exit diameters along the jet trajectory. These data are physically consistent with previous measurements in axisymmetric jets. The relative difficulty of obtaining three-dimensional and two-dimensional LDA data is briefly discussed.

  7. Exploring shot noise and Laser Doppler imagery with heterodyne holography

    OpenAIRE

    Gross, Michel; Verpillat, Frédéric; Joud, Fadwa; Atlan, Michael

    2012-01-01

    Heterodyne Holography is a variant of Digital Holography, where the optical frequencies of signal and reference arms can be freely adjusted by acousto-optic modulators. Heterodyne Holography is an extremely versatile and reliable holographic technique, which is able the reach the shot noise limit in sensitivity at very low levels of signal. Frequency tuning enables Heterodyne Holography to become a Laser Doppler imaging technique that is able to analyze various kinds of motion.

  8. Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging

    OpenAIRE

    Habib TABATABAI; Oliver, David E.; Rohrbaugh, John W.; Papadopoulos, Christopher

    2013-01-01

    Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted...

  9. Proposed pixel for custom laser doppler vibrometry camera

    OpenAIRE

    Jackson, Stephen

    2012-01-01

    Non-destructive testing is an important field of research in many areas of industry and science. This field covers methods that test some property of an object while not impacting its future usefulness. This project is specifically interested in a method of NDE called Laser Doppler Vibrometry (LDV), which uses light to probe the motion of an object's surface. This thesis presents research into the possibility of developing a full-field LDV camera capable of measuring the vibration at a nu...

  10. Velocity Measurement Based on Laser Doppler Effect

    International Nuclear Information System (INIS)

    A novel method for velocity measurement is presented. In this scheme, a parallel-linear-polarization dual-frequency laser is incident on the target and senses the target velocity with both the frequencies, which can increase the maximum measurable velocity significantly. The theoretical analysis and verification experiment of the novel method are presented, which show that high-velocity measurement can be achieved with high precision using this method. (fundamental areas of phenomenology(including applications))

  11. Wind Doppler lidar with 1.5 ?m fiber laser

    International Nuclear Information System (INIS)

    Compact Doppler lidar with monostatic receiving geometry has been developed and tested. Laser source of the lidar is continuous wave fiber laser ELD-1000 with 1.5 ?m wavelength and 1 W output. For distances up to 100 m the range of measurable wind velocities is 1.5 – 20 m/s. Results obtained show that performance conditions for the lidar corresponds to the visibility range up to 1 km. Sonic vibrations with small amplitudes (? 10 nm) of remote targets with diffuse reflection has been registered by this device at distances up to 60 m

  12. Reynolds stress measurements in cylindrical geometry using laser Doppler anemometry

    International Nuclear Information System (INIS)

    Two-component one-point velocity correlation measurements in a cylindrical test section were performed using two-color Laser Doppler anemometry (LDA). In order to overcome the severe optical distortion effects in cylindrical geometry and achieve two-color spatial coincidence, two experimental methods were used: (1) attaching a rectangular, fluid-filled box to the pipe exterior; and (2) employing a laser-beam translating device. A description of these methods and some examples of coincidence data taken in pipe flow are presented

  13. Sub-Doppler laser spectroscopy of small molecules

    International Nuclear Information System (INIS)

    Three different techniques of laser spectroscopy with sub-Doppler resolution are discussed which have been applied to the investigation of diatomic and triatomic molecules. These are linear laser spectroscopy in collimated molecular beams, polarization spectroscopy and a combination of both methods with optical-optical double resonance techniques. The methods are illustrated by high resolution spectra of the molecules NaK, Cs2 and NO2. A section on time resolved spectroscopy, applied to lifetime measurements and to the determination of collision induced relaxation processes concludes the paper. (orig.)

  14. Spinning disk calibration method and apparatus for laser Doppler velocimeter

    Science.gov (United States)

    Snyder, P. K. (inventor)

    1986-01-01

    A method and apparatus for calibrating laser Doppler velocimeters having one or more intersecting beam pairs are described. These velocimeters measure fluid velocity by observing the light scattered by particles in the fluid stream. Moving fluid particulates are simulated by fine taut wires that are radially mounted on a disk that is rotated at a known velocity. The laser beam intersection locus is first aimed at the very center of the disk and then the disk is translated so that the locus is swept by the rotating wires. The radial distance traversed is precisely measured so that the velocity of the wires (pseudo particles) may be calculated.

  15. Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

    OpenAIRE

    Risti? Slavica S.; Ili? Jelena T.; ?antrak ?or?e S.; Risti? Ognjen R.; Jankovi? Novica Z.

    2012-01-01

    Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central par...

  16. Simultaneous laser-Doppler flowmetry of canine spinal cord and cerebral blood flow: responses to PaCO2 and blood pressure changes.

    Science.gov (United States)

    Sadanaga, M; Kano, T; Hashiguchi, A; Sakamoto, M; Higashi, K; Morioka, T

    1993-10-01

    We observed the relative changes of both spinal cord blood flow (local SCBF) and local cerebral blood flow (local CBF) using independent laser-Doppler flowmeters (LDF) in 12 dogs under N2O(50%)-O2-enflurane(1.0%) anesthesia. The dorsal surface of the lumbar spinal cord and the parietal surface of the brain were partially exposed. Two fine LDF probes were placed between the exposed surfaces and the dura maters at each site. Both local SCBF and local CBF decreased simultaneously with hyperventilation and increased with hypoventilation within several seconds. The local SCBF responses to PaCO2 changes were similar in direction and degree as those of the local CBF. Autoregulation of local SCBF to arterial blood pressure (ABP) changes was abolished, though that of the local CBF was still recognized in a blunted fashion within a mean ABP range of 50 to 150 mmHg. PMID:15278792

  17. Doppler shift of laser light reflected from expanding plasmas

    International Nuclear Information System (INIS)

    The Doppler shift of light reflected from a plane stratified expanding plasma is analyzed. Nonlinear effects are not considered and oblique incidence is restricted to the case of s polarization. The frequency shift is shown to consist of two components, one due to the motion of the reflecting surface, and another due to plasma flow through that surface. The shifts have a different dependence on the angle of incidence. Typically, the two contributions are comparable in laser fusion applications, being of order delta?/?approx.c/sub s//capprox.10-3, where c/sub s/ = (Z-italic T/sub e//M)/sup 1/2/ is the ion sound speed in the underdense plasma. In general, the Doppler shift has a time variation which induces a bandwidth in the reflected wave

  18. VCSEL-based miniature laser-Doppler interferometer

    Science.gov (United States)

    Pruijmboom, Armand; Schemmann, Marcel; Hellmig, Jochen; Schutte, Jeroen; Moench, Holger; Pankert, Joseph

    2008-02-01

    There are many applications for non-contact measurement of the displacement and velocity of moving objects, especially when achieved at low cost. An optical displacement sensor has been developed that can be compared to expensive laser-interferometry sensors, however at a cost compatible with requirements for consumer products. This miniature Laser-Doppler Interferometer works on all light scattering surfaces. The first large-scale application is in PC-mice. The measurement principle employs so-called "Laser Self Mixing", which occurs when laser light scattered on a surface, within the coherence length, is coupled back into the laser cavity. When the object is moving, the back-scattered light is continuously shifting in phase relative to the laser light at the laser mirror. This results in a periodic perturbation of the feedback into the laser cavity, which causes modulations of the light intensity in the cavity. The frequency of these modulations is proportional the speed of the object. A VCSEL, optimized for this application, is used as light source, a photo-diode in the sensor measures the intensity fluctuations and, finally, an integrated circuit transfers the photo-diode signal into velocity or displacement information. To determine the direction of the movement, a triangle modulation of the laser-current is used, which modulates the laser-temperature and hence the laser frequency. Next to the applications in PC-mice a much wider range of applications as input device in consumer products can be envisaged. For instance menu navigation by finger movement over a sensor in remote controls, mobile phones and lap tops. Furthermore a wide field of applications is envisaged in the manufacturing of industrial equipment, which requires non-contact measurement of the movement of materials. The small form factor of less than 0.2 cubic centimeters allows applications previously considered impossible.

  19. Sub-Doppler Laser Cooling of Fermionic K-40 Atoms

    CERN Document Server

    Modugno, G; Hannaford, P; Roati, G; Inguscio, M

    1999-01-01

    We report laser cooling of fermionic K-40 atoms, with temperatures down to (15 +/- 5) microK, for an enriched sample trapped in a MOT and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of two of the lowest realizable rms velocity (~3.5v rec) in 3D optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of K-40 atoms.

  20. Holographic laser Doppler imaging of pulsatile blood flow

    CERN Document Server

    Bencteux, Jeffrey; Kostas, Thomas; Bayat, Sam; Atlan, Michael

    2015-01-01

    We report on wide-field imaging of pulsatile motion induced by blood flow using heterodyne holographic interferometry on the thumb of a healthy volunteer, in real-time. Optical Doppler images were measured with green laser light by a frequency-shifted Mach-Zehnder interferometer in off-axis configuration. The recorded optical signal was linked to local instantaneous out-of-plane motion of the skin at velocities of a few hundreds of microns per second, and compared to blood pulse monitored by plethysmoraphy during an occlusion-reperfusion experiment.

  1. Sub-Doppler Laser Cooling of Fermionic K-40 Atoms

    OpenAIRE

    Modugno, G.; Benko, C.; Hannaford, P.; Roati, G.; Inguscio, M.

    1999-01-01

    We report laser cooling of fermionic K-40 atoms, with temperatures down to (15 +/- 5) microK, for an enriched sample trapped in a MOT and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of two of the lowest realizable rms velocity (~3.5v rec) in 3D optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniqu...

  2. Sub-Doppler modulation spectroscopy of potassium for laser stabilization

    International Nuclear Information System (INIS)

    We study modulation spectroscopy of the potassium D2 transitions at 766.7 nm. The vapour pressure, controlled by heating a commercial reference cell, is first optimized using conventional saturated absorption spectroscopy. Heterodyne detection then yields sub-Doppler frequency discriminants suitable for stabilizing lasers in experiments with cold atoms. Comparisons are made between spectra obtained by direct modulation of the probe beam and those using modulation transfer from the pump via nonlinear mixing. Finally, suggestions are made for further optimization of the signals. (paper)

  3. Holographic laser Doppler imaging of pulsatile blood flow

    OpenAIRE

    Bencteux, Jeffrey; Pagnoux, Pierre; Kostas, Thomas; Bayat, Sam; Atlan, Michael

    2015-01-01

    We report on wide-field imaging of pulsatile motion induced by blood flow using heterodyne holographic interferometry on the thumb of a healthy volunteer, in real-time. Optical Doppler images were measured with green laser light by a frequency-shifted Mach-Zehnder interferometer in off-axis configuration. The recorded optical signal was linked to local instantaneous out-of-plane motion of the skin at velocities of a few hundreds of microns per second, and compared to blood p...

  4. Laser doppler measurements of flow in a rod bundle

    International Nuclear Information System (INIS)

    A two component laser doppler velocimeter with polarized beams and frequency shift was used to measure the turbulent flow field for axial flow between the rods of a nine rod, square pitch rod bundle. Parameters measured include mean axial and lateral velocities, turbulence intensities and the friction factor. The axial velocities for 10 000 to 40 000 Reynolds number are slightly higher than those reported by Rowe. The maximum lateral velocities measured are about 1% of the bulk velocity; somewhat larger than suggested by earlier authors. Axial and lateral turbulence intensities are larger than those in pipe flows. (orig.)

  5. Short-time Fourier transform laser Doppler holography

    OpenAIRE

    Samson, Benjamin; Atlan, Michael

    2012-01-01

    We report a demonstration of laser Doppler holography at a sustained acquisition rate of 250 Hz on a 1 Megapixel complementary metal-oxide-semiconductor (CMOS) sensor array and image display at 10 Hz frame rate. The holograms are optically acquired in off-axis configuration, with a frequency-shifted reference beam. Wide-field imaging of optical fluctuations in a 250 Hz frequency band is achieved by turning time-domain samplings to the dual domain via short-time temporal Four...

  6. Fiber optic laser Doppler anemometry in swirling jets

    Science.gov (United States)

    Taghavi, R.; Rice, E. J.

    1991-01-01

    Time-averaged and fluctuating quantities are measured in a free turbulent swirling jet. Data from a two-component laser Doppler anemometry (LDA) are compared to the measurements via hot-wire and 5-hole pitot probes. To acquire the proper seeding density near the axis of a swirling jet for LDA measurements proved difficult. This is due to an imbalance of the centrifugal force and radial pressure gradient, which throws the seeding material off the axis. Despite this problem, close agreement between various measurement techniques is obtained.

  7. Holographic laser Doppler imaging of pulsatile blood flow

    Science.gov (United States)

    Bencteux, Jeffrey; Pagnoux, Pierre; Kostas, Thomas; Bayat, Sam; Atlan, Michael

    2015-06-01

    We report on wide-field imaging of pulsatile motion induced by blood flow using heterodyne holographic interferometry on the thumb of a healthy volunteer, in real-time. Optical Doppler images were measured with green laser light by a frequency-shifted Mach-Zehnder interferometer in off-axis configuration. The recorded optical signal was linked to local instantaneous out-of-plane motion of the skin at velocities of a few hundreds of microns per second, and compared to blood pulse monitored by plethysmoraphy during an occlusion-reperfusion experiment.

  8. Sub-Doppler laser cooling and magnetic trapping of erbium

    International Nuclear Information System (INIS)

    We investigate cooling mechanisms in magneto-optically and magnetically trapped erbium. We find efficient sub-Doppler cooling in our trap, which can persist even in large magnetic fields due to the near degeneracy of two Lande g factors. Furthermore, a continuously loaded magnetic trap is demonstrated where we observe temperatures below 25 ?K. These favorable cooling and trapping properties suggest a number of scientific possibilities for rare-earth-metal atomic physics, including narrow linewidth laser cooling and spectroscopy, unique collision studies, and degenerate bosonic and fermionic gases with long-range magnetic dipole coupling

  9. Laser spectroscopy of multi-level doppler broadened atomic system

    International Nuclear Information System (INIS)

    Doppler broadened atomic vapor system can be easily prepared for spectroscopy study than an atomic beam system can be. Vapor cell and hollow cathode discharge lamps are widely used in the experiment. The possibility for observing the trapped state in a Doppler broadened ? system was examined and confirmed by our early experiment where counter-propagating laser beams are used. For the measurement of the hyperfine structure constants of high-lying levels of heavy elements, we compared the co-propagating and counter-propagating beams in a Doppler broadened ladder systems. It was shown that the counter-propagating beams give a stronger and narrower signal than that from the co-propagating beams. Our treatment also considers the power broadening of the transition. For some photo-ionization experiments, it is necessary to pump two thermally populated levels simultaneously to the higher level and then to the auto-ionizing levels. A technique is proposed to avoid the trapped state and to increase the ionization efficiency.

  10. Doppler tomography of mass-transfer processes in condensed media induced by femtosecond laser pulses

    International Nuclear Information System (INIS)

    A femtosecond laser scheme for studying laser-induced mass transfer is proposed. A Doppler velocity meter using a femtosecond Ti: sapphire laser is created. A thermal capillary convection initiated by this laser in paraffin is investigated (with a spatial resolution of 15 ?m). (laser applications and other topics in quantum electronics)

  11. Method for acceleration measurement using a laser Doppler interferometer

    International Nuclear Information System (INIS)

    A novel method for estimating acceleration directly from the digitized waveform of interference signals is proposed based on a laser Doppler interferometer. In this method, a second-order polynomial function is developed, of which the coefficients are calculated by fitting with the time and corresponding order of zero crossings. Acceleration is calculated as the product of the second-order coefficient and the wavelength of a laser. The performance of this method is evaluated by comparing with the zero crossing method (ZCM) and zero crossing fitting method (ZFM) in simulation. The results show that the accuracy of acceleration calculated by using this method is higher than those by using the ZCM and ZFM, particularly when the signal-to-noise ratio is lower than 40 dB. (technical design note)

  12. Holographic optical system for aberration corrections in laser Doppler velocimetry

    Science.gov (United States)

    Kim, R. C.; Case, S. K.; Schock, H. J.

    1985-01-01

    An optical system containing multifaceted holographic optical elements (HOEs) has been developed to correct for aberrations introduced by nonflat windows in laser Doppler velocimetry. The multifacet aberration correction approach makes it possible to record on one plate many sets of adjacent HOEs that address different measurement volume locations. By using 5-mm-diameter facets, it is practical to place 10-20 sets of holograms on one 10 x 12.5-cm plate, so that the procedure of moving the entire optical system to examine different locations may not be necessary. The holograms are recorded in dichromated gelatin and therefore are nonabsorptive and suitable for use with high-power argon laser beams. Low f-number optics coupled with a 90-percent efficient distortion-correcting hologram in the collection side of the system yield high optical efficiency.

  13. Precision of laser Doppler scanning in clinical use.

    Science.gov (United States)

    Stücker, M; Heese, A; Hoffmann, K; Röchling, A; Altmeyer, P

    1995-09-01

    Reactions of the cutaneous microcirculation to local stimuli have been quantitated in terms of area of erythema (planimetry), change in colour (colorimetry) and time-dependent changes in perfusion (one-dimensional laser Doppler fluxmetry (LDF)). Using the new technique of laser Doppler scanning (LDS) it is now possible to quantify and demonstrate two-dimensional patterns of microvascular perfusion in terms of intensity and extent. The precision of this new technique was compared with the previously established techniques by examining the reactions of 15 healthy volunteers to the intracutaneous injection of carbacholin and isotonic NaCl solutions. Both stimuli were applied paravertebrally, on the left and right side. Reactions were examined after 10 min. As a control for temporal reproducibility the examination was repeated on another day. All methods allowed the differentiation of reactions to carbacholin from those to NaCl (P or = 0.78). Using LDF or planimetry, reproducibility of values was lower (r or = 0.77). Hyperaemic areas seen with LDS were significantly larger than those determined by planimetry. Results of LDS are reproducible spatially and temporally: the technique will allow time-course observations of skin reactions that are accompanied by medium-term changes in perfusion. PMID:8593712

  14. Magnetostriction measurement in thin films using laser Doppler vibrometry

    Energy Technology Data Exchange (ETDEWEB)

    Varghese, Ronnie, E-mail: ronniev@vt.edu [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, VA 24061 (United States); Viswan, Ravindranath [Materials Science and Engineering Department, Virginia Tech, Blacksburg, VA 24061 (United States); Joshi, Keyur [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, VA 24061 (United States); Seifikar, Safoura [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Zhou, Yuan [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, VA 24061 (United States); Schwartz, Justin [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, VA 24061 (United States)

    2014-08-01

    This paper reports the laser Doppler vibrometry based measurement of the magnetostriction in magnetic thin films. Using this method, the strain induced by an AC magnetic field in the polycrystalline cobalt ferrite and nickel ferrite thin films grown on silicon and platinized silicon substrates was measured under a DC magnetic bias. The experimental setup and the derivation of the magnetostriction constant from the experimentally measured deflection values are discussed. The magnetostriction values derived using force and bending moment balances were compared with that derived from an industry standard relationship. In addition, we corroborate our approach by comparing the values derived from bending theory calculations of magnetically induced torque to those from measurements using Vibrating Sample Magnetometer (VSM). At high DC magnetic field bias, the magnitude of magnetization calculated from the measured magnetostriction was found to match the measured magnetization by VSM. - Highlights: • Laser Doppler vibrometry based technique to measure magnetostriction in thin films. • Strain induced by an AC magnetic field under a DC magnetic bias. • Picometer level deflections in polycrystalline cobalt and nickel ferrite thin films.

  15. Magnetostriction measurement in thin films using laser Doppler vibrometry

    International Nuclear Information System (INIS)

    This paper reports the laser Doppler vibrometry based measurement of the magnetostriction in magnetic thin films. Using this method, the strain induced by an AC magnetic field in the polycrystalline cobalt ferrite and nickel ferrite thin films grown on silicon and platinized silicon substrates was measured under a DC magnetic bias. The experimental setup and the derivation of the magnetostriction constant from the experimentally measured deflection values are discussed. The magnetostriction values derived using force and bending moment balances were compared with that derived from an industry standard relationship. In addition, we corroborate our approach by comparing the values derived from bending theory calculations of magnetically induced torque to those from measurements using Vibrating Sample Magnetometer (VSM). At high DC magnetic field bias, the magnitude of magnetization calculated from the measured magnetostriction was found to match the measured magnetization by VSM. - Highlights: • Laser Doppler vibrometry based technique to measure magnetostriction in thin films. • Strain induced by an AC magnetic field under a DC magnetic bias. • Picometer level deflections in polycrystalline cobalt and nickel ferrite thin films

  16. Raman processes in sub-Doppler laser cooling

    International Nuclear Information System (INIS)

    We have observed a new type of sub-Doppler laser cooling with neither polarization gradients nor magnetic fields. All known sub-Doppler laser cooling methods require one of these two to resdistribute the atomic population among the energy levels. This allows the irreversible processes of optical pumping vels. This allows the irreversible processes of optical pumping (OP) to manipulate the conservative force of light shifts (e.g. resonant exchange between the two beams comprising a standing wave) into a damping force. Our scheme employs stimulated Raman transitions between ground state hyperfine levels of Rb with a bichromatic standing wave, accompanied by a momentum change of ?p = 2?k. OP, with ?p = 1?k, creates a population imbalance allowing repetition of the Raman process. When the detuning of the light from Raman resonance ? is properly chosen, the net momentum exchange damps the atomic motion. Changing ? by only ?/6(1 MHz) replaces cooling by heating. This process separates the velocity selective Raman resonance and OP processes differently from others, and helps clarify the role of these different mechanisms

  17. Measuring with laser Doppler vibrometer on moving frame (LDVMF)

    Science.gov (United States)

    Rahimi, Siamand; Li, Zili; Dollevoet, Rolf

    2014-05-01

    Structural dynamic gives insight into structural properties such as mass, eigenfrequencies, eigenmodes, modal damping and strain distribution and can be utilized in structural health monitoring, dynamic sub-structuring, etc. In this context structural vibration is measured and used. The measurement is done by means of conventional sensors such as accelerometers or non destructively using Laser Doppler Vibrometer (LDV), for instance. The non-destructive, non-contact measurement techniques preserve the integrity of the structure and don't add mass and stiffness to the structure under test. When one deals with civil structures such as rail and road ways, pipelines and catenary the importance of these techniques becomes more evident as they allow standoff measurement on a moving frame. Nevertheless when LDV is employed due to the relative in-plane motion between the LDV and the target speckle noise is generated which degrades the signal quality and makes this application not very straightforward but challenging. One of the first Laser Doppler Vibrometer on moving frame is adopted to measure and monitor the ground vibration, aiming at detection of buried land mines. The major addressed difficulty in this application is the speckle noise present in the acquired signal. In general the signal quality and the Signal to Noise Ratio (SNR) are a function of the laser spot size and wave length, measurement distance, relative velocity and sampling frequency. A trade-off between these factors, which are not always intuitive would help to minimize the noise floor due to the speckle noise. In this paper a test rig is presented which allows to study the speckle noise at different measurement ranges, between 1.8 and 2.8 m, and different velocities, up to 150 km/h. The results might serve as a guideline to the design process of a LDVMF.

  18. Non-contact photoacoustic tomography with a laser Doppler vibrometer

    Science.gov (United States)

    Xu, Guan; Wang, Cheng; Feng, Ting; Oliver, David E.; Wang, Xueding

    2014-03-01

    Most concurrent photoacoustic tomography systems are based on traditional ultrasound measurement regime, which requires the contact or acoustic coupling material between the biological tissue and the ultrasound transducer. This study investigates the feasibility of non-contact measurement of photacoustic signals generated inside biomedical tissues by observing the vibrations at the surface of the tissues with a commercial laser Doppler vibrometer. The vibrometer with 0- 2MHz measurement bandwidth and 5 MHz sampling frequency was integrated to a conventional rotational PAT data acquisition system. The data acquisition of the vibrometer was synchronized to the laser illumination from an Nd:YAG laser with output at 532nm. The laser energy was tuned to 17.5mJ per square centimeter. The PA signals were acquired at 120 angular locations uniformly distributed around the scanned objects. The frequency response of the measurement system was first calibrated. 2-inch-diamater cylindrical phantoms containing small rubber plates and biological tissues were afterwards imaged. The phantoms were made from 5% intralipid solution in 10% porcine gelatin to simulate the light scattering in biological tissue and to backscatter the measurement laser from the vibrometer. Time-domain backprojection method was used for the image reconstruction. Experiments with real-tissue phantoms show that with laser illumination of 17.5 mJ/cm2 at 532 nm, the non-contact photoacoustic (PA) imaging system with 15dB detection bandwidth of 2.5 MHz can resolve spherical optical inclusions with dimension of 500?m and multi-layered structure with optical contrast in strongly scattering medium. The experiment results prompt the potential implementation of the non-contact PAT to achieve "photoacoustic camera".

  19. Laser Doppler Velocimetry and full-field soot volume fraction

    Science.gov (United States)

    Greenberg, Paul S.

    1995-01-01

    Since its introduction in the mid-sixties, Laser Doppler Velocimetry (LDV) has become one of the most widely used methods for the measurement of flows. Its remote and essentially non-intrusive nature provides an invaluable tool for a variety of difficult measurement situations which would be otherwise inaccessible. The high spatial resolution and rapid temporal response afforded by this technique are well suited to the determination of spatial and temporal details of flow fields, as well as characterization of turbulence. Advances in the understanding of the properties of LDV signals, accompanied by technological advances in coherent laser sources, detectors of high sensitivity and low noise, optical fabrication techniques and high-speed digital signal processing architectures have resulted in systems of increased accuracy and flexibility. As will be shown, recent progress in solid-state lasers and photo-detectors has been beneficial insofar as the compatibility of this method with the unique and severe constraints inherent in microgravity combustion science experiments.

  20. Application of Laser Doppler Vibrometery for human heart auscultation.

    Science.gov (United States)

    Koegelenberg, S; Scheffer, C; Blanckenberg, M M; Doubell, A F

    2014-01-01

    In this study the potential of a Laser Doppler Vibrometer (LDV) was tested as a non-contact sensor for the classification of heart sounds. Of the twenty participants recorded using the LDV, five presented with Aortic Stenosis (AS), three were healthy and twelve presented with other pathologies. The recorded heart sounds were denoised and segmented using a combination of the Electrocardiogram (ECG) data and the complexity of the signal. Frequency domain features were extracted from the segmented heart sound cycles and used to train a K-nearest neighbor classifier. Due to the small number of participants, the classifier could not be trained to differentiate between normal and abnormal participants, but could successfully distinguish between participants who presented with AS and those who did not. A sensitivity of 80 % and a specificity of 100 % were achieved a test dataset. PMID:25570986

  1. Laser Doppler vibrometry measurement of the mechanical myogram

    Science.gov (United States)

    Rohrbaugh, John W.; Sirevaag, Erik J.; Richter, Edward J.

    2013-12-01

    Contracting muscles show complex dimensional changes that include lateral expansion. Because this expansion process is intrinsically vibrational, driven by repetitive actions of multiple motor units, it can be sensed and quantified using the method of Laser Doppler Vibrometry (LDV). LDV has a number of advantages over more traditional mechanical methods based on microphones and accelerometers. The LDV mechanical myogram from a small hand muscle (the first dorsal interosseous) was studied under conditions of elastic loading applied to the tip of the abducted index finger. The LDV signal was shown to be related systematically to the level of force production, and to compare favorably with conventional methods for sensing the mechanical and electrical aspects of muscle contraction.

  2. Corrections to the direct spectral estimation for laser Doppler data

    Science.gov (United States)

    Nobach, Holger

    2015-05-01

    An algorithm for estimating the power spectral density and the correlation function of laser Doppler-generated data sets is introduced. The algorithm is of the type of direct spectral estimators including weighting of individual velocity values to correct statistical biases caused by the correlation of instantaneous data rate and velocity values. It is extended by the forward-backward inter-arrival time weighting, the correction of the wraparound error, that of dead-time influences, and an error due to the removal of estimated block mean values. A temporal limitation of the correlation function as an alternative to the block averaging allows the block lengths to be chosen in a wide range with less necessities for compromises between systematic and random errors.

  3. Cantilever spring constant calibration using laser Doppler vibrometry

    International Nuclear Information System (INIS)

    Uncertainty in cantilever spring constants is a critical issue in atomic force microscopy (AFM) force measurements. Though numerous methods exist for calibrating cantilever spring constants, the accuracy of these methods can be limited by both the physical models themselves as well as uncertainties in their experimental implementation. Here we report the results from two of the most common calibration methods, the thermal tune method and the Sader method. These were implemented on a standard AFM system as well as using laser Doppler vibrometry (LDV). Using LDV eliminates some uncertainties associated with optical lever detection on an AFM. It also offers considerably higher signal to noise deflection measurements. We find that AFM and LDV result in similar uncertainty in the calibrated spring constants, about 5%, using either the thermal tune or Sader methods provided that certain limitations of the methods and instrumentation are observed

  4. Velocity bias in two component individual realization laser Doppler velocimetry

    International Nuclear Information System (INIS)

    In addition to the typical biasing problems associated with one component Laser Doppler Velocimetry (LDV), two component LDV measurements can suffer from other types of bias. In particular, coincidence bias is of interest. This type of velocity bias results from requiring simultaneous, or nearly simultaneous, measurements of the velocity components. In this study, two velocity bias correction schemes, based on the time between velocity samples, together with three different approaches for constant time-interval sampling of the velocity data have been evaluated. The effects of coincidence seeding rate and coincidence time window on velocity, normal, and Reynold's stress measurements are presented. Measurements with narrow coincidence window settings and/or low coincidence seeding rate resulted in velocity measurements which were larger than the true local average

  5. Flow tracing fidelity of scattering aerosol in laser Doppler velocimetry

    Science.gov (United States)

    Mazumder, M. K.; Kirsch, K. J.

    1975-01-01

    An experimental method for the determination of the flow-tracing fidelity of a scattering aerosol used in laser Doppler velocimeters was developed with particular reference to the subsonic turbulence measurements. The method employs the measurement of the dynamic response of a flow-seeding aerosol excited by acoustic waves. The amplitude and frequency of excitation were controlled in order to simulate the corresponding values of fluid turbulence components. Experimental results are presented on the dynamic response of aerosols over the size range from 0.1 to 2.0 microns in diam and over the frequency range 100 Hz to 100 kHz. It was observed that unit-density spherical scatterers with diameters of 0.2 micron followed subsonic air turbulence frequency components up to 100 kHz with 98% fidelity.

  6. Bragg cell laser intensity modulation: effect on laser Doppler velocimetry measurements

    International Nuclear Information System (INIS)

    In most laser Doppler velocimetry (LDV) systems, the frequency of one of the two laser beams that intersect to create the probe volume is shifted with an acousto-optic element. It is shown here that Bragg shifting can impose a problematic fluctuation in intensity on the frequency-shifted beam, producing spurious velocity measurements. This fluctuation occurs at twice the Bragg cell frequency, and its relative amplitude to the time average intensity is a function of the ratio of the laser beam diameter to the Bragg cell acoustic wavelength. A physical model and a configuration procedure to minimize adverse effects of the intensity modulations are presented.

  7. Evaluation of the marginal gingival health using laser doppler flowmetry

    Scientific Electronic Library Online (English)

    Hakan, Develioglu; Bülent, Kesim; Aykut, Tuncel.

    Full Text Available Os objetivos deste estudo foram comparar o fluxo sangüíneo gengival (FSG) em sítios teste (dentes retentores de próteses parciais fixas) e sítios controle (dentes naturais contralaterais) e investigar se há alguma relação entre os índices clínicos (IC) e os valores de FSG. Doze indivíduos saudáveis [...] (6 mulheres e 6 homens) com idades entre 20 a 54 anos participaram deste estudo. O FSG foi medido no ponto médio da gengina marginal em ambos os sítios teste e controle utilizando dopplerfluxometria a laser (DFL). Além disso, as medidas referentes ao índice de placa, índice gengival e profundidade de sondagem foram registradas. Foi observada diferença estatisticamente significante (p0.05) entre os sítios teste e controle com relação aos índices clínicos, exceto para o índice de placa. Os achados deste estudo sugerem que existe uma relação significante entre próteses parciais fixas retidas por resina com margens localizadas subgengivalmente e o FSG marginal. Embora os índices clínicos sejam úteis para coletar informações sobre as condições clínicas dos tecidos gengivais, o FSG é uma ferramenta importante para medir o fluxo sanguíneo tissular gengival e avaliar a saúde periodontal. Em conclusão, a dopplerfluxometria a laser pode ser usada juntamente com índices clínicos para avaliar a saúde gengival marginal. Abstract in english The purposes of this study were to compare the gingival blood flow (GBF) in test sites (teeth retaining fixed partial dentures) and control sites (contralateral natural teeth) and investigate whether there is any relationship between clinical indices and GBF values. Twelve healthy subjects (6 female [...] s and 6 males) aged 20 to 54 years were enrolled this study. The GBF was measured from the middle point of the marginal gingiva in the test and control sites using laser Doppler flowmetry (LDF). Additionally, plaque index, gingival index and probing depth measurements were recorded. Statistically significant difference (p0.05) was found between test and control sites with respect to the clinical indices, except for plaque index. The findings of this study suggest that there is a significant relation between resin-bonded fixed partial dentures with margins located subgingivally and marginal GBF. Clinical indices are helpful to collect information about the clinical health status of gingival tissues, but GBF is a good tool to measure gingival tissue blood flow and assess periodontal health. In conclusion, laser Doppler flowmetry can be used together with clinical indices to evaluate the marginal gingival health.

  8. Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 1. Laser Doppler wake vortex tracking at Kennedy Airport

    Science.gov (United States)

    Krause, M. C.; Wilson, D. J.; Howle, R. E.; Edwards, B. B.; Craven, C. E.; Jetton, J. L.

    1976-01-01

    Test operations of the Scanning Laser Doppler System (SLDS) at Kennedy International Airport (KIA) during August 1974 through June 1975 are reported. A total of 1,619 data runs was recorded with a totally operational system during normal landing operations at KIA. In addition, 53 data runs were made during cooperative flybys with the C880 for a grand total of 1672 recorded vortex tracks. Test crews were in attendance at KIA for 31 weeks, of which 25 weeks were considered operational and the other six were packing, unpacking, setup and check out. Although average activity equates to 67 recorded landing operations per week, two periods of complete runway inactivity spanned 20 days and 13 days, respectively. The operation frequency therefore averaged about 88 operations per week.

  9. Laser Doppler holographic microscopy in transmission: application to fish embryo imaging

    OpenAIRE

    Verrier, Nicolas; Alexandre, Daniel; Gross, Michel

    2014-01-01

    We have extended Laser Doppler holographic microscopy to transmission geometry. The technique is validated with living fish embryos imaged by a modified upright bio-microcope. By varying the frequency of the holographic reference beam, and the combination of frames used to calculate the hologram, multimodal imaging has been performed. Doppler images of the blood vessels for different Doppler shifts, images where the flow direction is coded in RGB colors or movies showing blo...

  10. Photonic Doppler velocimetry of laser-ablated ultrathin metals

    International Nuclear Information System (INIS)

    Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection 'confusing' the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis t probes, and sampling different analysis techniques

  11. Laser Doppler vibrometry with a single-frequency microchip green laser

    International Nuclear Information System (INIS)

    We have developed a laser vibrometer based on an Nd:YVO4/YVO4/KTP monolithic single-frequency green laser operating at 532 nm, with a narrow linewidth of radiation. Two configurations of the laser Doppler vibrometer have been investigated—with the so-called single- and double-frequency Bragg shifts. Measurement of heterodyne signals as a mixing result of scattered and reference beams has been carried out. In both configurations we have obtained signals with a high S/N ratio of >30 dB with resolution bandwidth = 200 kHz for a vibrometer output power of 3 mW. In our opinion, stable single-frequency solid-state green lasers provide new opportunities for the development of miniature laser vibrometry

  12. Laser Doppler anemometer: new algorithm for signal processing at high light scattering

    Science.gov (United States)

    Borozdova, M. A.; Fedosov, I. V.; Tuchin, V. V.

    2015-03-01

    We developed a Laser Doppler anemometer which uses a novel technique of signal processing to minimize the effect of undesirable light scattering. The technique has been applied to estimate Doppler frequency shift at flow velocity measurements. We have shown that technique is applicable for measurements in turbid media like biological tissues.

  13. Measurement of high intensity atomic and ionic beams by using method of Doppler laser spectroscopy

    International Nuclear Information System (INIS)

    The possibility of measuring divergence of high intensity atomic and ionic beams by using the method of Doppler laser spectroscopy, proposed by the author, is considered. This method, which is based on the detection of induced atomic radiation, allows for increased efficiency of detecting primary levels in comparison with passive Doppler spectroscopy which uses detection of spontaneous radiation

  14. Frequency-domain, wide-field laser Doppler in vivo imaging

    OpenAIRE

    Atlan, Michael; Gross, Michel; Forget, Benoit,; Vitalis, Tania; Rancillac, Armelle; Dunn, Andrew

    2006-01-01

    We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne optical-mixing configuration, that can create wide-field laser Doppler maps. As an illustration, we show results obtained in a mouse brain, in vivo, showing the Doppler signature of blood flow. The instrument is based on the frequency-shifting digital holography scheme.

  15. Cramér–Rao lower bound of laser Doppler measurements at moving rough surfaces

    International Nuclear Information System (INIS)

    Laser Doppler techniques are widely used for measuring both fluid flows and moving solid surfaces. The measurement uncertainty of laser Doppler sensors is fundamentally limited by the uncertainty of the Doppler frequency estimation. Generally, the minimum achievable uncertainty of any unbiased estimator is given by the Cramér–Rao lower bound (CRLB). While the CRLB is well known for laser Doppler burst signals of single tracer particles used in flow research, no analytical expression for the CRLB has been known up to now for scattered light signals of rough solid surfaces where speckle effects occur. Therefore, the aim of this paper is to close this gap and to provide a simple analytical expression for the CRLB for the Doppler frequency estimation from scattered light signals of moving rough solid surfaces for the first time. A comparison with experimental data demonstrates the validity of the derived analytical CRLB formula, which is also proven to be consistent with previous works. The progress for science is that this analytical CRLB formula enables both an easy estimation of the minimum achievable uncertainty of laser Doppler measurements at moving rough surfaces and a direct analysis of the influences of certain system and signal parameters on the measurement uncertainty. This reveals specific measuring features and capabilities of different laser Doppler techniques. In addition, the CRLB is a valuable tool to evaluate the efficiency of applied signal processing techniques

  16. Diagnostic accuracy of laser Doppler flowmetry versus strain gauge plethysmography for segmental pressure measurement

    DEFF Research Database (Denmark)

    HØyer, Christian; Sandermann, Jes

    2013-01-01

    To assess the diagnostic accuracy of laser Doppler flowmetry (LDF) with mercury-in-silastic strain gauge plethysmography (SGP) as a reference test for measuring the toe and ankle pressures in patients with known or suspected peripheral arterial disease (PAD).

  17. See the Brain at Work—Intraoperative Laser Doppler Functional Brain Imaging

    OpenAIRE

    Martin-Williams, Erica J.; Raabe, Andreas; Van de Ville, Dimitri; Leutenegger, Marcel; Szelenyi, Andrea; Hattingen, Elke; Gerlach, Rudiger; Seifert, Voker; Hauger, Christoph; LOPEZ, ANTONIO; Leitgeb, Rainer A.; Unser, Michael; Lasser, Theo

    2009-01-01

    During open brain surgery we acquire perfusion images non-invasively using laser Doppler imaging. The regions of brain activity show a distinct signal in response to stimulation providing intraoperative functional brain maps of remarkably strong contrast.

  18. Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

    Directory of Open Access Journals (Sweden)

    Risti? Slavica S.

    2012-01-01

    Full Text Available Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6 exists a small, or negligible pipe wall influence on laser- -Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analyzed and determined for used test rig and for some other pipe geometries. [Projekat Ministarstva nauke Republike Srbije, br. TR 35046

  19. Accuracy of flowmeters measuring horizontal groundwater flow in an unconsolidated aquifer simulator.

    Science.gov (United States)

    Bayless, E.R.; Mandell, Wayne A.; Ursic, James R.

    2011-01-01

    Borehole flowmeters that measure horizontal flow velocity and direction of groundwater flow are being increasingly applied to a wide variety of environmental problems. This study was carried out to evaluate the measurement accuracy of several types of flowmeters in an unconsolidated aquifer simulator. Flowmeter response to hydraulic gradient, aquifer properties, and well-screen construction was measured during 2003 and 2005 at the U.S. Geological Survey Hydrologic Instrumentation Facility in Bay St. Louis, Mississippi. The flowmeters tested included a commercially available heat-pulse flowmeter, an acoustic Doppler flowmeter, a scanning colloidal borescope flowmeter, and a fluid-conductivity logging system. Results of the study indicated that at least one flowmeter was capable of measuring borehole flow velocity and direction in most simulated conditions. The mean error in direction measurements ranged from 15.1 degrees to 23.5 degrees and the directional accuracy of all tested flowmeters improved with increasing hydraulic gradient. The range of Darcy velocities examined in this study ranged 4.3 to 155 ft/d. For many plots comparing the simulated and measured Darcy velocity, the squared correlation coefficient (r2) exceeded 0.92. The accuracy of velocity measurements varied with well construction and velocity magnitude. The use of horizontal flowmeters in environmental studies appears promising but applications may require more than one type of flowmeter to span the range of conditions encountered in the field. Interpreting flowmeter data from field settings may be complicated by geologic heterogeneity, preferential flow, vertical flow, constricted screen openings, and nonoptimal screen orientation.

  20. Sub-Doppler Laser Cooling of Thulium Atoms in a Magneto-optical Trap

    OpenAIRE

    Sukachev, D.; A. Sokolov; Chebakov, K.; Akimov, A.; Kanorsky, S.; Kolachevsky, N.; Sorokin, V

    2010-01-01

    We have experimentally studied sub-Doppler laser cooling in a magneto-optical trap for thulium atoms working at the wavelength of 410.6\\,nm. Without any dedicated molasses period of sub-Doppler cooling, the cloud of $3\\times 10^6$ atoms at the temperature of 25(5)\\,$\\mu$K was observed. The measured temperature is significantly lower than the Doppler limit of 240$\\mu$K for the cooling transition at 410.6\\,nm. High efficiency of the sub-Doppler cooling process is due to a near...

  1. Laser Doppler phase shifting using a high-speed digital micromirror device

    Science.gov (United States)

    Kuo, D.; Sharpe, J. P.

    2015-03-01

    Here we demonstrate the use of a binary spatial light modulator (Texas Instruments Digital Micromirror Device) to impart a phase shift to the beams of a laser Doppler velocimeter. Advantages of this approach to laser Doppler phase shifting include low cost, low power consumption, a precisely known phase-stepping frequency and the capability of working with a broad range of optical wavelengths. In the implementation shown here velocities of order 1 cm/s are measured.

  2. High-speed wave-mixing laser Doppler imaging, in vivo.

    OpenAIRE

    Atlan, Michael; Gross, Michel; Vitalis, Tania; Rancillac, Armelle; Rossier, Jean; Boccara, Claude

    2008-01-01

    An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording with a complementary metal-oxide semi-conductor (CMOS) camera. Observation of a mice cranium with near infrared ($\\lambda$ = 785 nm) laser light in reflection configuration is reported. Doppler spe...

  3. Two-beam nonlinear Kerr effect to stabilize laser frequency with sub-Doppler resolution

    OpenAIRE

    Martins, Weliton Soares; Cavalcante, Hugo L. D. de S.; de Silans, Thierry Passerat; Oriá, Marcos; Chevrollier, Martine.

    2012-01-01

    Avoiding laser frequency drifts is a key issue in many atomic physics experiments. Several techniques have been developed to lock the laser frequency using sub-Doppler dispersive atomic lineshapes as error signals in a feedback loop. We propose here a two-beam technique that uses non-linear properties of an atomic vapor around sharp resonances to produce sub-Doppler dispersive-like lineshapes that can be used as error signals. Our simple and robust technique has the advantag...

  4. Intraoperative use of laser Doppler in the study of cerebral microvascular circulation.

    OpenAIRE

    MOSTERT, Michael Martin

    1988-01-01

    Laser Doppler (LD) flowmetry has been used for evaluation of microcirculatory flow in a variety of human tissues, including skin, muscle, retina and recently the brain. In the present paper, intraoperative Laser Doppler recordings have been performed in 72 cases, in basal conditions and after stimulation. The morphology of basal recordings obtained from normal cortical areas were analyzed and three different rhythmical variations were identified; these rhythmical variations are described and ...

  5. Laser Doppler velocimeter multiplexer interface for simultaneous measured events

    Science.gov (United States)

    Harrison, Dean R. (inventor); Brown, James L. (inventor)

    1988-01-01

    A laser Doppler velocimeter multiplexer interface includes an event pulse synchronizer which synchronizes data pulses from events A, B, and C. Clock control is connected to receive timing information on the data pulses from the synchronizer. Displays are connected to receive clock signals from the clock control for indicating a data rate for each of the measured events A, B, and C. The display is connected to receive clock signals from the clock control to indicate a coincidence rate between data pulses for any selected combination of the measured events A, B, and C. A multiplexer receives the data pulses from the events A, B, and C and rate data from the clock control. The multiplexer has output for supplying the data pulses and rate data to a single input of a data processing system. A multiplexer control is connected to supply control signals to the multiplexer for selecting the event data pulses and the rate data for output from the multiplexer. The multiplexer control receives start signals from the pulse synchronizer and user selected inputs for desired outputs from the multiplexer.

  6. Assessment of gut mucosal perfusion and colonic tissue blood flow during abdominal aortic surgery with gastric tonometry and laser Doppler flowmetry.

    Science.gov (United States)

    Nakatsuka, Mitsuru

    2002-01-01

    The objective of this study was to investigate the effect of infrarenal aortic cross-clamping and unclamping on gut mucosal perfusion by gastric tonometry and on sigmoid colonic tissue blood flow by laser Doppler flowmetry during abdominal aortic surgery. This was a prospective before-and-after intervention comparison study in a university hospital of 8 male patients, aged 57-87, undergoing elective infrarenal abdominal aortic surgery. Each patient was pretreated with ranitidine. Following general anesthesia, a nasogastric tonometer was inserted into the stomach. The balloon of the tonometer was filled with 2.5 mL of normal saline for gas tension and pH analysis. This process was repeated before and after aortic cross-clamping and unclamping. Gastric mucosal pHi was calculated with the Henderson-Hasselbalch equation from the arterial Hco3- and the tonometrically measured mucosal Pco2. A laser Doppler flow probe was placed in contact with the serosa of the sigmoid colon against the mesentery after the abdomen was opened. Sigmoid colonic tissue blood flow (SCBF) was assessed by the laser Doppler flowmeter. Gastric mucosal pHi by gastric tonometry and colonic tissue blood flow by laser Doppler flowmetry were measured before and after aortic cross-clamping and unclamping. Gastric mucosal pHi decreased significantly 30 minutes after aortic cross-clamping (7.37 +/-0.07) (p SCBF decreased significantly after aortic cross-clamping (28.1 +/-4.8 mL/min/100 g) compared with the value before aortic cross-clamping (51.9 +/-11.3 mL/min/100 g) (p SCBF returned to 41.7 +/-7.4 mL/min/100 g. It is concluded that transient episodes of significant intestinal mucosal ischemia may have been encountered occasionally in patients undergoing abdominal aortic surgery, but a sigmoid colonic tissue blood flow of 41.7 +/-7.4 mL/min/100 g was sufficient to prevent postoperative ischemic colitis regardless of whether there was ligation or no ligation of inferior mesenteric artery among the studied population since none of the patients developed clinically significant ischemic colitis. PMID:12075384

  7. Dead time effects in laser Doppler anemometry measurements

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Buchhave, Preben

    2014-01-01

    We present velocity power spectra computed by the so-called direct method from burst-type laser Doppler anemometer (LDA) data, both measured in a turbulent round jet and generated in a computer. Using today’s powerful computers, we have been able to study more properties of the computed spectra than was previously possible, and we noted some unexpected features of the spectra that we now attribute to the unavoidable influence of a finite measurement volume (MV). The most prominent effect, which initially triggered these studies, was the appearance of damped oscillations in the higher frequency range, starting around the cutoff frequency due to the finite size of the MV. Using computer-generated data mimicking the LDA data, these effects have previously been shown to appear due to the effect of dead time, i.e., the finite time during which the system is not able to acquire new measurements. These dead times can be traced back to the fact that the burst-mode LDA cannot measure more than one signal burst at a time. Since the dead time is approximately equal to the residence time for a particle traversing a measurement volume, we are dealing with widely varying dead times, which, however, are assumed to be measured for each data point. In addition, the detector and processor used in the current study introduce a certain amount of fixed processing and data transfer times, which further contribute to the distortion of the computed spectrum. However, we show an excellent agreement between a measured spectrum and our modeled LDA data, thereby confirming the validity of our model for the LDA burst processor.

  8. Enhanced Doppler ultrasound imaging of interstitial laser therapy in rat mammary tumors

    Science.gov (United States)

    Zasuly, James M.; Fan, Ming; Dowlatshahi, Kambiz

    1997-05-01

    In order to better develop ultrasonography for use in monitoring interstitial laser therapy (ILT), we imaged rat mammary tumors using power Doppler ultrasound in conduction with intravenous contrast agent (Albunex) before and after laser therapy. Small vessel perfusion throughout a variable portion of the tumor could be detected by power Doppler ultrasound. Lesions created with diode laser by delivery of 500 to 3000 J appeared as perfusion defects on post-treatment images. Image topography and lesion size correlated with gross histologic findings. We conclude that ultrasonographic monitoring of local changes in blood flow using contrast enhancing agent can be useful in characterizing lesions created with ILT.

  9. Pipe flow measurements of turbulence and ambiguity using laser-Doppler velocimetry

    Science.gov (United States)

    Berman, N. S.; Dunning, J. W.

    1973-01-01

    The laser-Doppler ambiguities predicted by George and Lumley (1973) have been verified experimentally for turbulent pipe flows. Experiments were performed at Reynolds numbers from 5000 to 15,000 at the center line and near the wall. Ambiguity levels were measured from power spectral densities of FM demodulated laser signals and were compared with calculations based on the theory. The turbulent spectra for these water flows after accounting for the ambiguity were equivalent to hot-film measurements at similar Reynolds numbers. The feasibility of laser-Doppler measurements very close to the wall in shear flows is demonstrated.

  10. Optical design for laser Doppler angular encoder with sub-nanoradian sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Shu, D.; Alp, E.E.; Barraza, J.; Kuzay, T.M.; Mooney, T.

    1997-09-01

    A novel laser angular encoder system has been developed based on the principles of radar, the Doppler effect, optical heterodyning, and self aligning multiple reflection optics. Using this novel three dimensional multiple reflection optical path, a 10 to 20 times better resolution has been reached compared to commercially available laser Doppler displacement meters or laser interferometer systems. With the new angular encoder, sub-nanoradian resolution has been attained in the 8 degree measuring range in a compact setup about 60 mm (H) x 150 mm (W) x 370 mm (L) in size for high energy resolution applications at the Advanced Photon Source undulator beamline 3-ID.

  11. Laser Doppler vibrometry experiment on a piezo-driven slot synthetic jet in water.

    Czech Academy of Sciences Publication Activity Database

    Brou?ková, Zuzana; Vít, T.; Trávní?ek, Zden?k

    Liberec, 2014 - (Dan?ová, P.; Vít, T.), s. 71-77 [Experimental Fluid Mechanics 2014. ?eský Krumlov (CZ), 18.11.2014-21.11.2014] R&D Projects: GA ?R GA14-08888S Institutional support: RVO:61388998 Keywords : synthetic jet * laser Doppler vibrometry * laser induced fluorescence Subject RIV: BJ - Thermodynamics

  12. Laser cooling of an atomic beam by spatial Doppler tuning of a resonance transition

    International Nuclear Information System (INIS)

    Cooling of an atomic beam by Doppler tuning is proposed. The atomic beam is decelerated by repeatedly crossing a resonant laser beam at a decreasing angle. An example of the experimental configuration to slow down a two-level atomic beam by a factor of 20 using two lasers is given. (author)

  13. Insensitivity of single particle time domain measurements to laser velocimeter 'Doppler ambiguity.'

    Science.gov (United States)

    Johnson, D. A.

    1973-01-01

    It is shown that single particle time domain measurements in high speed gas flows obtained by a laser velocimeter technique developed for use in wind tunnels are not affected by the so-called 'Doppler ambiguity.' A comparison of hot-wire anemometer and laser velocimeter measurements taken under similar flow conditions is used for the demonstration.

  14. Signal parameters estimation using time-frequency representation for laser doppler anemometry

    OpenAIRE

    Baral-Baron, Grégory; Lahalle, Elisabeth; Fleury, Gilles; Lacondemine, Xavier; Schlotterbeck, Jean-Pierre

    2012-01-01

    This paper describes a processing method to estimate parameters of chirp signals for Laser Doppler Anemometry (LDA). The Doppler frequency as well as additional useful parameters are considered here. These parameters are the burst width and the frequency rate. Different estimators based on the spectrogram are proposed. Cramer-Rao bounds are given and performance of the estimators compared to the state of the art using Monte-Carlo simulations for synthesized LDA signals. The characteristics of...

  15. Laser Doppler holographic microscopy in transmission: application to fish embryo imaging

    CERN Document Server

    Verrier, Nicolas; Gross, Michel

    2014-01-01

    We have extended Laser Doppler holographic microscopy to transmission geometry. The technique is validated with living fish embryos imaged by a modified upright bio-microcope. By varying the frequency of the holographic reference beam, and the combination of frames used to calculate the hologram, multimodal imaging has been performed. Doppler images of the blood vessels for different Doppler shifts, images where the flow direction is coded in RGB colors or movies showing blood cells individual motion have been obtained as well. The ability to select the Fourier space zone that is used to calculate the signal, makes the method quantitative.

  16. Reactor main steam flowmeter

    International Nuclear Information System (INIS)

    The present invention intends to stabilize the measurement of a flowmeter disposed to a main steam pipe of a pressure vessel of a BWR type reactor. That is, the exit of the nozzle of the main steam pipe in the reactor pressure vessel comprises a gradually restricting portion, a throat portion and a diffusing portion. The position of the pressure detection terminal disposed downstream of the gradually restricting portion is below the pipeline of a flowmeter element, and condensates are stored in a pressure introduction pipeline succeeding to the pressure detection terminal. With such a constitution, when an accident of main steam pipe rupture should occur, the amount of steams jetted from the reactor pressure vessel to the reactor container, that is, the amount of loss of coolants can be reduced. As a result, the reactor container and the reactor building can be made compact and safe. Further, since a straight pipe, which has been necessary in an existent standard venturi type element, is no more necessary, the volume of the reactor container can be reduced. (I.S.)

  17. Soap film gas flowmeter

    International Nuclear Information System (INIS)

    A soap film gas flowmeter is described comprising: a flow tube having a hollow body with opposite open ends through which a soap film is propelled and a first closed chamber housing a soap solution. It also includes means for supporting the flow tube in a substantially vertical position with the open bottom end of the flow tube disposed in the first chamber above the soap solution; a second closed chamber into which the open top end of the flow tube extends and gas inlet means for introducing gas into the first chamber at a flow rate to be measured using the flowmeters. A gas exit means is included for discharging the gas introduced into the first chamber through the second chamber. Plus there are means for generating a single soap bubble from the soap solution substantially at the bottom end of the flow tube and a relatively large opening in the flowtube for providing an open passageway for inlet gas to pass through the flowtube when the bottom open end of the flowtube is covered by the soap solution

  18. Laser Doppler position sensor for position and shape measurements of fast rotating objects

    Science.gov (United States)

    Czarske, Jürgen; Pfister, Thorsten; Büttner, Lars

    2006-08-01

    We report about a novel optical method based on laser Doppler velocimetry for position and shape measurements of moved solid state surfaces with approximately one micrometer position resolution. 3D shape measurements of a rotating cylinder inside a turning machine as well as tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm and 586 m/s blade tip velocity are presented. All results are in good agreement with conventional reference probes. The measurement accuracy of the laser Doppler position sensor is investigated in dependence of the speckle pattern. Furthermore, it is shown that this sensor offers high temporal resolution and high position resolution simultaneously and that shading can be reduced compared to triangulation. Consequently, the presented laser Doppler position sensor opens up new perspectives in the field of real-time manufacturing metrology and process control, for example controlling the turning and the grinding process or for future developments of turbo machines.

  19. Laser Doppler visualisation of the velocity field by excluding the influence of multiparticle scattering

    International Nuclear Information System (INIS)

    The method of laser Doppler visualisation and measurement of the velocity field in gas and liquid flows by suppressing the influence of multiparticle scattering is discussed. The cross section of the flow under study is illuminated by a laser beam transformed by an anamorphic optical system into a laser sheet. The effect of multiparticle scattering is eliminated by obtaining differential combinations of frequency-demodulated images of the laser sheet in different regions of the angular spectrum of scattered light. (laser applications and other topics in quantum electronics)

  20. Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms

    OpenAIRE

    Piilo, J.; Lundh, E; Suominen, K. -A.

    2003-01-01

    We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. This is the normal situation e.g. in magneto-optical traps (MOT). The Doppler limit heating rate due to radiative collisions is calculated for Mg-24 atoms in a magneto-optical trap based on the singlet S_0 - singlet P_1 atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We a...

  1. Three interfering beams in laser Doppler velocimetry for particle position and microflow velocity profile measurements

    International Nuclear Information System (INIS)

    It is proposed to use three interfering and coplanar laser beams to form the probe volume of laser Doppler systems. This allows us to obtain, for each particle crossing this probe volume, a Doppler signal whose frequency amplitude spectrum exhibits two characteristic peaks. Electromagnetic calculations and experimental validations clearly demonstrate that we can estimate simultaneously, from the analysis of these two frequency peaks, the particle position along the optical axis and one velocity component. This technique is expected to have great potentialities for velocity profile measurements in microfluidic or boundary layer flows, as well as for the sizing of spherical particles

  2. Sub-Doppler Laser Cooling of Thulium Atoms in a Magneto-optical Trap

    CERN Document Server

    Sukachev, D; Chebakov, K; Akimov, A; Kanorsky, S; Kolachevsky, N; Sorokin, V

    2010-01-01

    We have experimentally studied sub-Doppler laser cooling in a magneto-optical trap for thulium atoms working at the wavelength of 410.6\\,nm. Without any dedicated molasses period of sub-Doppler cooling, the cloud of $3\\times 10^6$ atoms at the temperature of 25(5)\\,$\\mu$K was observed. The measured temperature is significantly lower than the Doppler limit of 240$\\mu$K for the cooling transition at 410.6\\,nm. High efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Land\\'e-$g$ factors of the lower $4f^{13}6s^{2}\\, (J\\,=\\,{7}/{2})$ and the upper $4f^{12}5d_{3/2}6s^{2}\\, (J\\,=\\,{9}/{2})$ cooling levels.}

  3. Laser backscattering analytical model of Doppler power spectra about rotating convex quadric bodies of revolution

    Science.gov (United States)

    Gong, YanJun; Wu, ZhenSen; Wang, MingJun; Cao, YunHua

    2010-01-01

    We propose an analytical model of Doppler power spectra in backscatter from arbitrary rough convex quadric bodies of revolution (whose lateral surface is a quadric) rotating around axes. In the global Cartesian coordinate system, the analytical model deduced is suitable for general convex quadric body of revolution. Based on this analytical model, the Doppler power spectra of cones, cylinders, paraboloids of revolution, and sphere-cones combination are proposed. We analyze numerically the influence of geometric parameters, aspect angle, wavelength and reflectance of rough surface of the objects on the broadened spectra because of the Doppler effect. This analytical solution may contribute to laser Doppler velocimetry, and remote sensing of ballistic missile that spin.

  4. Application of laser Doppler velocimeter to velocity measurement of charged dust particles in high electric field

    International Nuclear Information System (INIS)

    As a preliminary study for the collection process of dust particles in an electrostatic precipitator, a laser Doppler velocimeter with high spatial resolution and high accuracy was used to measure the moving velocity of small dust particles charged in a high electric field. For an optical system of the velocimeter, the differential type was adopted. To achieve the high sampling rate, the period-measuring system was used for obtaining the velocity data from Doppler beat signals. By means of the laser Doppler velocimeter constructed here, accurate measurements of the moving velocity and direction of dust particles as a function of the applied electrode voltage and polarity were performed over a sectional plane of the model electrostatic precipitator. The experimental results may be useful for revealing the collection process of dust particles in the high electric field and, therefore, for the design of the electrostatic precipitator. (orig.)

  5. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

    International Nuclear Information System (INIS)

    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S1/2?5P3/2?6S1/2?nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

  6. Two-channel self-mixing laser Doppler measurement with carrier-frequency-division multiplexing

    Science.gov (United States)

    Otsuka, Kenju; Abe, Kazutaka; Sano, Natsumi; Sudo, Seiichi; Ko, Jing-Yuan

    2005-03-01

    We demonstrate real-time two-channel self-mixing laser-Doppler measurement with extreme optical sensitivity using a laser-diode-pumped thin-slice LiNdP4O12 laser. Successful carrier-frequency-division-multiplexed two-channel operations are realized by using one laser, two sets of optical frequency shifters, and a two-channel frequency-modulated-wave demodulation circuit. Simultaneous independent measurements of vibrations of speakers and averaged motions of small Brownian particles in different scattering cells are demonstrated. Self-mixing photon correlation spectroscopy of particle size distributions is also discussed.

  7. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

    OpenAIRE

    Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.

    2011-01-01

    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a star-like geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S_{1/2}->5P_{3/2}->6S_{1/2}->nP in Rb atoms have shown that compared to the one- and two-photon laser excitation this approach provides much narrower line width and longer coherence time for both cold at...

  8. He-Ne laser effects on blood microcirculation. An in vivo study through laser doppler flowmetry

    International Nuclear Information System (INIS)

    Blood microcirculation performs an important function in tissue repair process, as well as in pain control, allowing for greater oxygenation of the tissues and the accelerated expulsion of metabolic products, that may be contributing to pain. Low Intensity Laser Therapy (LILT) is widely used to promote healing, and there is an assumption that it is mechanism of action may be due to an enhancement of blood supply. The purpose of this study was to evaluate, using laser Doppler flowmetry (LDF), the stated effects caused by radiation emitted by a He-Ne laser (?=632.8 nm) on blood microcirculation during tissue repair. To this end, 15 male mice were selected and received a liquid nitrogen provoked lesion, above the dorsal region, and blood flow was measured periodically, during 21 days. Due to radiation emission by the LDF equipment, a control group was established to evaluate possible effects caused by this radiation on microcirculation. To evaluate the He-Ne laser effects, a 1.15 J/cm2 dose was utilized, with an intensity of 6 mW/cm2. The results obtained demonstrate flow alterations, provoked by the lesion, and subsequent inflammatory response. There was no statistical difference between the studied groups. As per the analysis of the results there is no immediate effect due the radiation emitted by a He Ne laser on microcirculation, although a percentage increase was observed in day 7 on medium blood flow rate in irradiated specimens. New studies are necessary to validate the use of this wavelength, in order to promote beneficial alterations in blood supply in radiated areas. (author)

  9. Multipoint laser Doppler vibrometry using holographic optical elements and a CMOS digital camera

    OpenAIRE

    Connelly, Michael J.; Szecowka, Przemyslaw M.; Jallapuram, Raghavendra; Martin, Suzanne; Toal, VIncent; Whelan, Maurice P.

    2008-01-01

    A laser Doppler vibrometer (LDV) is described in which holographic optical elements are used to provide the interferometer reference and object illumination beams. A complementary metal-oxide semiconductor camera, incorporating a digital signal processor, is used to carry out real-time signal processing of the interferometer output to allow multipoint LDV to be implemented.

  10. Experimental data base of turbulent flow in rod bundles using laser doppler velocimeter

    International Nuclear Information System (INIS)

    This report presents in detail the hydraulic characteristics measurements in subchannels of rod bundles using one-component LDV (Laser Doppler Velocimeter). In particular, this report presents the figures and tabulations of the resulting data. The detailed explanations about these results are shown in references publicated or presented at the conference. 4 kinds of experimental work were performed so far. (Author)

  11. Precise micro flow rate measurements by a laser Doppler velocity profile sensor with time division multiplexing

    International Nuclear Information System (INIS)

    This paper presents the measurement of flow rate inside a microchannel by using a laser Doppler technique. For this application a novel laser Doppler velocity profile sensor has been developed. Instead of parallel fringe systems, two superposed fan-like fringe systems with opposite gradients are employed to determine the velocity distribution inside the microchannel directly. The sensor utilizes the time division multiplexing technique to discriminate both fringe systems. A velocity uncertainty of 0.18% and a spatial resolution of 960 nm are demonstrated in the flow, which is the highest spatially resolved measurement by a laser Doppler technique published to date. Flow rate measurements, in the range of 30 µl min?1, with a statistical uncertainty of 5 × 10?4 are further presented. In comparison to a reference, by precise weighing, the mean deviation between both measurement principles amounts to 1%. With the advantage of high spatial resolution with simultaneous low velocity uncertainty, the laser Doppler velocity profile sensor offers a new tool for microfluidic diagnostics, e.g. in lab-on-a-chip systems or for drug delivery, which requires very small flow rates

  12. Velocity measurements of sputtered particles using the Laser-Doppler method

    International Nuclear Information System (INIS)

    The development of tunable single frequency dye lasers has enabled the realization of a Doppler-Shift-Laser-Spectrometer (DSLS) for the detection and energy analysis of neutral sputtered particles. It is based on the Doppler-shifted resonance excitation by monochromatic radiation. The particle beam to be measured is intersected by two laser beams at 900 and 300 respectively. The laser is turned over a resonance line of the species to be investigated. The sharp non-Doppler-shifted 900 spectrum is used as zero marking on the velocity axis. The intensity of the Doppler-shifted 300 fluorescence spectrum is directly proportional to the particle intensity in the corresponding velocity interval. A high detection sensitivity of about 50 particles/cm3 and a velocity resolution of 50 m/s can be achieved. With the DSLS it is possible to investigate one particular kind of sputtered atoms with high resolution over a wide energy region. Results for different targets bombarded with rare gas ions are presented. The obtained spectra allow to determine the influence of slow thermal processes, thermal spikes and collision cascades to the sputtering process. A comparison with results obtained with time-of-flight experiments is given. (orig.)

  13. DOPPLER SHIFT IN X-RAY SPECTRUM FOR LASER-IMPLODED SPHERICAL MICROSHELLS

    OpenAIRE

    Fiedorowicz, H.; Denus, S.; Jeziak, K.; Kolanowski, M.; Parys, P.; Pawlowicz, W.; Wolowski, J

    1988-01-01

    Doppler shifts due to plasma motion have been observed in the space resolved X-ray spectra for the laser-imploded spherical microshells. The analysis of the X-ray spectrum makes it possible to study the ablation process from the microshell surface.

  14. Basic problems associated with the interpretation of the fluorescence spectra in Doppler-shift laser spectroscopy

    International Nuclear Information System (INIS)

    The influence of power broadening and the interpretation of the measured fluorescence spectra as being proportional to the flux or density in Doppler-shift laser fluorescence spectroscopy using cw-dye laser excitation are discussed. Power broadening was found to be negligible for the measurement of energy spectra of sputtered species and in the low energy regime (below several 1000m/s) the measured fluorescence signal of Na was found to be proportional to the flux. (Auth.)

  15. Differential Laser Doppler based Non-Contact Sensor for Dimensional Inspection with Error Propagation Evaluation

    OpenAIRE

    Ketsaya Vacharanukul; Samir Mekid

    2006-01-01

    To achieve dynamic error compensation in CNC machine tools, a non-contact laser probe capable of dimensional measurement of a workpiece while it is being machined has been developed and presented in this paper. The measurements are automatically fed back to the machine controller for intelligent error compensations. Based on a well resolved laser Doppler technique and real time data acquisition, the probe delivers a very promising dimensional accuracy at few microns over a range of 100 mm. Th...

  16. Basic problems associated with the interpretation of the fluorescence spectra in Doppler-shift laser spectroscopy

    International Nuclear Information System (INIS)

    The influence of power broadening and the interpretation of the measured fluorescence spectra as being proportional to the flux or density in Doppler-shift laser fluorescence spectroscopy using cw-dye laser excitation are discussed. Power broadening was found to be negligible for the measurement of energy spectra of sputtered species and in the low energy regime (below several 1000m/s) the measured fluorescence signal of Na was found to be proportional to the flux. (Author)

  17. Simultaneous multivelocity component laser Doppler velocimetry using one digital frequency processor

    Science.gov (United States)

    Johnson, D. A.

    1990-01-01

    Digital frequency processing used in conjunction with optical frequency shifting is an ideal way to achieve simultaneous multivelocity component measurements in laser Doppler velocimetry. This becomes obvious once realized that multivelocity component information at different frequency offsets can be obtained directly from the composite frequency spectrum of a single-channel digital frequency processor. The approach has numerous advantages over the very popular approach of using a different laser wavelength, photodetector, and signal processor for each velocity component.

  18. Signal processing considerations for low signal to noise ratio laser Doppler and phase Doppler signals

    Science.gov (United States)

    Ibrahim, K. M.; Wertheimer, G. D.; Bachalo, William D.

    1991-01-01

    The relative performance of current methods used for estimating the phase and the frequency in LDV and phase Doppler applications in low signal to noise ratio conditions is analyzed. These methods include the Fourier analysis and the correlation techniques. Three methods that use the correlation function for frequency and phase estimations are evaluated in terms of accuracy and speed of processing. These methods include: (1) the frequency estimation using zero crossings counting of the auto-correlation function, (2) the Blackman-Tukey method, and (3) the AutoRegressive method (AR). The relative performance of these methods is evaluated and compared with the Fourier analysis method which provides the optimum performance in terms of the Maximum Likelihood (ML) criteria.

  19. Sub-Doppler laser cooling and magnetic trapping of erbium

    OpenAIRE

    Berglund, Andrew J.; Lee, Siu Au; Mcclelland, Jabez J.

    2008-01-01

    We investigate cooling mechanisms in magneto-optically and magnetically trapped erbium. We find efficient sub-Doppler cooling in our trap, which can persist even in large magnetic fields due to the near degeneracy of two Lande g factors. Furthermore, a continuously loaded magnetic trap is demonstrated where we observe temperatures below 25 microkelvin. These favorable cooling and trapping properties suggest a number of scientific possibilities for rare-earth atomic physics, ...

  20. Three-dimensional laser cooling at the Doppler limit

    OpenAIRE

    Chang, Rockson; Hoendervanger, Lynn; Bouton, Quentin; Fang, Yami; Klafka, Tobias; Audo, Kevin; Aspect, Alain; Westbrook, Christoph I; Clément, David

    2014-01-01

    Many predictions of Doppler cooling theory of two-level atoms have never been verified in a three-dimensional geometry, including the celebrated minimum achievable temperature $\\hbar \\Gamma/2 k_B$, where $\\Gamma$ is the transition linewidth. Here, we show that, despite their degenerate level structure, we can use Helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the s...

  1. Structure of a swirl-stabilized spray flame by imaging, laser Doppler velocimetry, and phase Doppler anemometry

    Science.gov (United States)

    Edwards, C. F.; Rudoff, R. C.

    1991-01-01

    Data are presented which describe the mean structure of a steady, swirl-stabilized, kerosene spray flame in the near-injector region of a research furnace. The data presented include ensemble-averaged results of schlieren, luminosity, and extinction imaging, measurement of the gas phase velocity field by laser Doppler velocimetry, and characterization of the condensed phase velocity by phase Doppler anemometry. The results of these studies define six key regions in the flame: the dense spray region; the rich, two-phase, fuel jet; the main air jet; the internal product recirculation zone; the external product recirculation zone; and the gaseous diffusion flame zone. The first five of these regions form a conical mixing layer which prepares the air and fuel for combustion. The air and fuel jets comprise the central portion of this mixing layer and are bounded on either side by the hot product gases of the internal and external recirculation zones. Entrainment of these product gases into the air/fuel streams provides the energy required to evaporate the fuel spray and initiate combustion. Intermittency of the internal recirculation and spray jet flows accounts for unexpected behavior observed in the aerodynamics of the two phases. The data reported herein are part of the database being accumulated on this spray flame for the purpose of detailed comparison with numerical modeling.

  2. Shape and vibration measurement of fast rotating objects employing novel laser Doppler techniques

    Science.gov (United States)

    Pfister, Thorsten; Günther, Philipp; Büttner, Lars; Czarske, Jürgen

    2007-06-01

    This contribution presents novel laser Doppler techniques, which allow simultaneous measurement of radial position and tangential velocity and, thus, determination of the shape of rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-like interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It is shown that the position uncertainty of this sensor is not only independent of the surface roughness but, most notably, that it is in principle independent of the object velocity. Thus, in contrast to conventional distance sensors, the novel laser Doppler position sensor offers high temporal resolution below 3 ?s and high position resolution in the micrometer range simultaneously. The sensor was applied to automatic 3D shape measurements of turning parts and to monitoring rotor unbalance and dynamic deformations. Furthermore, in situ measurements of tip clearance and rotor vibrations at turbo machines for up to 600 m/s blade tip velocity are reported. The results are in excellent agreement with those of triangulation and capacitive probes, respectively.

  3. Differential Laser Doppler based Non-Contact Sensor for Dimensional Inspection with Error Propagation Evaluation

    Directory of Open Access Journals (Sweden)

    Ketsaya Vacharanukul

    2006-06-01

    Full Text Available To achieve dynamic error compensation in CNC machine tools, a non-contactlaser probe capable of dimensional measurement of a workpiece while it is being machinedhas been developed and presented in this paper. The measurements are automatically fedback to the machine controller for intelligent error compensations. Based on a well resolvedlaser Doppler technique and real time data acquisition, the probe delivers a very promisingdimensional accuracy at few microns over a range of 100 mm. The developed opticalmeasuring apparatus employs a differential laser Doppler arrangement allowing acquisitionof information from the workpiece surface. In addition, the measurements are traceable tostandards of frequency allowing higher precision.

  4. Laser-induced fluorescence and Doppler-free polarization spectra in a low density hydrogen plasma

    International Nuclear Information System (INIS)

    The H? spectral line profile in a low-density hydrogen plasma of a microwave discharge has been measured by the laser-induced fluorescence and the Doppler-free polarization spectroscopy methods with a pulsed high-power tunable laser. The saturation characteristics of the output signals in each method were examined in detail with observations of typical saturation broadening. The original homogeneous width of the line was estimated in the limit of no laser pumping, and various factors governing this width are discussed while demonstrating the importance of the clarification of molecular processes in the discharge. In the Doppler-free spectra a large distortion of the spectrum was also found under different operating conditions; it was attributed to the plasma opacity effect. (author)

  5. Laser Doppler blood flow complementary metal oxide semiconductor imaging sensor with analog on-chip processing

    International Nuclear Information System (INIS)

    A 4x4 pixel array with analog on-chip processing has been fabricated within a 0.35 ?m complementary metal oxide semiconductor process as a prototype sensor for laser Doppler blood flow imaging. At each pixel the bandpass and frequency weighted filters necessary for processing laser Doppler blood flow signals have been designed and fabricated. Because of the space constraints of implementing an accurate ?0.5 filter at the pixel level, this has been approximated using the ''roll off'' of a high-pass filter with a cutoff frequency set at 10 kHz. The sensor has been characterized using a modulated laser source. Fixed pattern noise is present that is demonstrated to be repeatable across the array and can be calibrated. Preliminary blood flow results on a finger before and after occlusion demonstrate that the sensor array provides the potential for a system that can be scaled to a larger number of pixels for blood flow imaging

  6. Evaluation of data obtained from atmospheric laser Doppler velocimeter

    Science.gov (United States)

    Keck, T. S.; Telford, J. W.

    1985-01-01

    The Doppler lidar velocimeter produces a variety of kinds of data. Besides the line of sight velocity components, there are the reflected amplitudes and the Doppler widths. Computer graphics software for displaying these data was produced. Different methods of presentation are needed for the various items. A picture was produced as pictures are often the best way to gain understanding. The individual lidar scans form a crosshatch pattern. Thus one-dimensional measurements fit together to form a two-dimensional whole. A pair of velocity measurements at a point combine to form a wind measurement with direction and magnitude. This gives a forest of wind vectors. The goal is to find a recognizable pattern to these trees. Often it is necessary to show only part of the information. That is, show only the wind direction not its magnitude or reduce the wind to streamlines of air flow. In other cases data are reduced to contour plots. Just enough contour lines are included to show the picture described.

  7. Improving SNR of Doppler signal and expanding dynamic measurement range of single-mode VCSEL self-mixing laser Doppler velocimetry

    Science.gov (United States)

    Xu, Jun; He, Deyong; Lv, Liang; Gui, Huaqiao; Zhao, Tianpeng; Ming, Hai; Xie, Jianping

    2005-01-01

    The experiments show that the single-mode vertical-cavity surface-emitting laser (VCSEL) Laser Doppler Velocimetry (LDV) is better than the multilongitudinal-mode laser diode LDV in many characteristics, such as the accuracy of velocity measurement and the temperature range of the laser. Because the output power of the single-mode VCSEL is very low and only 0.7mW, the backscattered light received by the photodiode in the laser house is so weak that the signal-to-noise ratio (SNR) of Doppler signal is low. And the Doppler signal spectrum width spread and amplitude modulation envelope badly influence the velocity measurement accuracy. Analog phase-locked loop (PLL) has many characteristics, such as narrow band tracking filter, locking the signal with peak voltage and high rejection ratio of amplitude modulation. Using the analog PLL, the SNR of Doppler signal and the velocity measurement accuracy can be improved obviously. But because the locking range of the common analog PLL is narrow, we use difference frequency analog PLL to expand the locking range, and the dynamic range of velocity measurement can be greatly expanded. As a result, the velocity measurement accuracy of the single-mode VCSEL self-mixing LDV is better than 1% when the velocity range is from 30mm/s to 480mm/s.

  8. Remote Doppler velocimeter based on an Nd3+ : YAG chip laser and its application in a study of laser-induced hydrodynamic flows

    International Nuclear Information System (INIS)

    A remote Doppler velocimeter with extensive functional capabilities was constructed on the basis of a monolithic single-frequency ring Nd3+ : YAG laser pumped by a laser diode. This velocimeter was used to investigate laser-induced hydrodynamic flows in condensed media. (laser applications and other topics in quantum electronics)

  9. Vibration measurements on rotating machinery using laser Doppler velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Rothberg, S.J.; Halliwell, N.A. (Loughborough Univ. of Technology, Leicestershire (United Kingdom). Dept. of Mechanical Engineering)

    1994-07-01

    This paper explores the use of laser vibrometry for vibration measurement directly from a rotating component. The presence of a surface velocity component due to the rotation itself is shown to create a strong measurement dependency on vibration perpendicular to the intended measurement direction. Particular ambiguity results at synchronous frequencies. A mathematical means to resolve the genuine vibration components from two simultaneous laser vibrometer measurements is presented and shown to be effective in the study of nonsynchronous rotor vibrations.

  10. Laser Doppler vibrometry experiment on a piezo-driven slot synthetic jet in water

    Science.gov (United States)

    Brou?ková, Zuzana; Vít, Tomáš; Trávní?ek, Zden?k

    2015-05-01

    The present study deals with a slot synthetic jet (SJ) issuing from an actuator into quiescent surroundings and driven by a piezoceramic transducer. The actuator slot width was 0.36 mm, with a drive frequency proposed near the theoretical natural frequency of the actuator. The working fluid was water at room temperature. The present experiments used flow visualization (a laser-induced fluorescence technique) and laser Doppler vibrometry methods. Flow visualization was used to identify SJ formation, to demonstrate its function, and to estimate SJ velocity. Laser Doppler vibrometry was used to quantify diaphragm displacement and refine operating parameters. Phase averaging yielded a spatial and temporal diaphragm deflection during the actuation period. Taking incompressibility and continuity into consideration, the velocity in the actuator slot and the Reynolds number of the SJ were evaluated as 0.21 m/s and 157, respectively. The present results confirmed a SJ actuator function at the resonance frequency of approximately 46 Hz, which corresponds closely with the theoretical evaluation. The laser Doppler vibrometry results corresponded closely with an estimation of SJ velocity by the present flow visualization.

  11. Laser Doppler vibrometry experiment on a piezo-driven slot synthetic jet in water

    Directory of Open Access Journals (Sweden)

    Brou?ková Zuzana

    2015-01-01

    Full Text Available The present study deals with a slot synthetic jet (SJ issuing from an actuator into quiescent surroundings and driven by a piezoceramic transducer. The actuator slot width was 0.36 mm, with a drive frequency proposed near the theoretical natural frequency of the actuator. The working fluid was water at room temperature. The present experiments used flow visualization (a laser-induced fluorescence technique and laser Doppler vibrometry methods. Flow visualization was used to identify SJ formation, to demonstrate its function, and to estimate SJ velocity. Laser Doppler vibrometry was used to quantify diaphragm displacement and refine operating parameters. Phase averaging yielded a spatial and temporal diaphragm deflection during the actuation period. Taking incompressibility and continuity into consideration, the velocity in the actuator slot and the Reynolds number of the SJ were evaluated as 0.21 m/s and 157, respectively. The present results confirmed a SJ actuator function at the resonance frequency of approximately 46 Hz, which corresponds closely with the theoretical evaluation. The laser Doppler vibrometry results corresponded closely with an estimation of SJ velocity by the present flow visualization.

  12. A novel method for measurement of dynamic light scattering phase function of particles utilizing laser-Doppler power density spectra

    OpenAIRE

    Wojtkiewicz, Stanislaw; Liebert, Adam; Rix, Hervé; Sawosz, Piotr; Maniewski, Roman

    2012-01-01

    We developed a novel method of measurement of the dynamic light scattering phase function of particles utilizing laser Doppler technique. We show the theoretical background, validation carried out on Monte Carlo data and proposition of measurement setup.

  13. Measurement of the Doppler power of flowing blood using ultrasound Doppler devices.

    Science.gov (United States)

    Huang, Chih-Chung; Chou, Hung-Lung; Chen, Pay-Yu

    2015-02-01

    Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser-receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and echogenicity of flowing blood were compared with those obtained in several previous studies. PMID:25542489

  14. 1540-nm single frequency single-mode pulsed all fiber laser for coherent Doppler lidar

    Science.gov (United States)

    Zhang, Xin; Diao, Weifeng; Liu, Yuan; Liu, Jiqiao; Hou, Xia; Chen, Weibiao

    2015-02-01

    A single-mode single frequency eye-safe pulsed all fiber laser based on master oscillator power amplification structure is presented. This laser is composed of a narrow linewidth distributed laser diode seed laser and two-stage cascade amplifiers. 0.8 m longitudinally gradient strained erbium/ytterbium co-doped polarization-maintaining fiber with a core diameter of 10 ?m is used as the gain fiber and two acoustic-optics modulators are adopted to enhance pulse extinction ratio. A peak power of 160 W and a pulse width of 200 ns at 10 kHz repetition rate are achieved with transform-limited linewidth and diffraction-limited beam quality. This laser will be employed in a compact short range coherent Doppler wind lidar.

  15. Surface wave measurements using a single continuously scanning laser Doppler vibrometer: application to elastography.

    Science.gov (United States)

    Salman, Muhammad; Sabra, Karim G

    2013-03-01

    A continuous scanning laser Doppler vibrometry (CSLDV) obtained sweeping a single laser beam along a periodic scan pattern allows measuring surface vibrations at many points simultaneously by demultiplexing the CSLDV signal. This known method fundamentally differs from conventional scanning laser vibrometry techniques in which the laser beam is kept at a fixed point during each measurement and then moved to a new position prior to the next measurement. This article demonstrates the use of a CSLDV for measuring in a non-contact fashion the velocity of low-frequency surface waves (f laser beam, linearly scanned over the test surface at 200 Hz over lengths up to 6 cm, were validated using an array of three fixed laser Doppler vibrometers distributed along the same scan line. Furthermore, this CSLDV setup was used to measure the increase in surface wave velocity over the biceps brachii muscle which was directly correlated to the actual stiffening of the biceps occurring while a subject was performing voluntary contractions at an increasing level. PMID:23463997

  16. Accurate flexural spring constant calibration of colloid probe cantilevers using scanning laser Doppler vibrometry.

    Science.gov (United States)

    Gates, Richard S; Osborn, William A; Shaw, Gordon A

    2015-06-12

    Calibration of the flexural spring constant for atomic force microscope (AFM) colloid probe cantilevers provides significant challenges. The presence of a large attached spherical added mass complicates many of the more common calibration techniques such as reference cantilever, Sader, and added mass. Even the most promising option, AFM thermal calibration, can encounter difficulties during the optical lever sensitivity measurement due to strong adhesion and friction between the sphere and a surface. This may cause buckling of the end of the cantilever and hysteresis in the approach-retract curves resulting in increased uncertainty in the calibration. Most recently, a laser Doppler vibrometry thermal method has been used to accurately calibrate the normal spring constant of a wide variety of tipped and tipless commercial cantilevers. This paper describes a variant of the technique, scanning laser Doppler vibrometry, optimized for colloid probe cantilevers and capable of spring constant calibration uncertainties near ±1%. PMID:25990652

  17. A study of radial-flow turbomachinery blade vibration measurements using Eulerian laser Doppler vibrometry

    Science.gov (United States)

    Oberholster, A. J.; Heyns, P. S.

    2014-05-01

    The structural integrity of blades is critical to the health of turbomachinery. Since operational failure of these blades can possibly lead to catastrophic failure of the machine, it is important to have knowledge of blade conditions in an online fashion. Due to several practical implications, it is desired to measure blade vibration with a non-contact technique. The application of laser Doppler vibrometry towards the vibration based condition monitoring of axial-flow turbomachinery blades has been successfully demonstrated in previous work. In this paper the feasibility of using laser Doppler vibrometry to measure radial-flow turbomachinery blade vibrations is investigated with the aid of digital image correlation and strain gauge telemetry.

  18. Model studies of blood flow in basilar artery with 3D laser Doppler anemometer

    Science.gov (United States)

    Frolov, S. V.; Sindeev, S. V.; Liepsch, D.; Balasso, A.; Proskurin, S. G.; Potlov, A. Y.

    2015-03-01

    It is proposed an integrated approach to the study of basilar artery blood flow using 3D laser Doppler anemometer for identifying the causes of the formation and development of cerebral aneurysms. Feature of the work is the combined usage of both mathematical modeling and experimental methods. Described the experimental setup and the method of measurement of basilar artery blood flow, carried out in an interdisciplinary laboratory of Hospital Rechts der Isar of Technical University of Munich. The experimental setup used to simulate the blood flow in the basilar artery and to measure blood flow characteristics using 3D laser Doppler anemometer (3D LDA). Described a method of numerical studies carried out in Tambov State Technical University and the Bakoulev Center for Cardiovascular Surgery. Proposed an approach for sharing experimental and numerical methods of research to identify the causes of the basilar artery aneurysms.

  19. Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. 2

    Science.gov (United States)

    Seegmiller, H. L.; Bader, J. B.; Cooney, J. P.; Deyoung, A.; Donaldson, R. W., Jr.; Gunter, W. D., Jr.; Harrison, D. R.

    1985-01-01

    A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy.

  20. Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. II

    Science.gov (United States)

    Seegmiller, H. L.; Bader, J. B.; Cooney, J. P.; De Young, A.; Donaldson, R. W., Jr.

    1985-01-01

    A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy.

  1. Accurate flexural spring constant calibration of colloid probe cantilevers using scanning laser Doppler vibrometry

    Science.gov (United States)

    Gates, Richard S.; Osborn, William A.; Shaw, Gordon A.

    2015-06-01

    Calibration of the flexural spring constant for atomic force microscope (AFM) colloid probe cantilevers provides significant challenges. The presence of a large attached spherical added mass complicates many of the more common calibration techniques such as reference cantilever, Sader, and added mass. Even the most promising option, AFM thermal calibration, can encounter difficulties during the optical lever sensitivity measurement due to strong adhesion and friction between the sphere and a surface. This may cause buckling of the end of the cantilever and hysteresis in the approach–retract curves resulting in increased uncertainty in the calibration. Most recently, a laser Doppler vibrometry thermal method has been used to accurately calibrate the normal spring constant of a wide variety of tipped and tipless commercial cantilevers. This paper describes a variant of the technique, scanning laser Doppler vibrometry, optimized for colloid probe cantilevers and capable of spring constant calibration uncertainties near ±1%.

  2. A model-free noise removal for the interpolation method of correlation and spectral estimation from laser Doppler data

    Science.gov (United States)

    Nobach, Holger

    2015-05-01

    A procedure to estimate and remove the contribution of data noise to the correlation function and the power spectral density calculated from laser Doppler data with the interpolation method is introduced. In comparison with earlier approaches, the new procedure is model free and, therefore, more objective. The new procedure is proven based on experimental data taken with a laser Doppler system, where the power spectral density obtained with the interpolation method is compared directly to data from a hot-wire reference measurement.

  3. Clinical Utility of Laser-Doppler Vibrometer Measurements in Live Normal and Pathologic Human Ears

    OpenAIRE

    Rosowski, John J.; Nakajima, Hideko H.; Merchant, Saumil N

    2008-01-01

    The laser-Doppler vibrometer (LDV) is a research tool that can be used to quickly measure the sound-induced velocity of the tympanic membrane near the umbo (the inferior tip of the malleus) in live human subjects and patients. In this manuscript we demonstrate the LDV to be a sensitive and selective tool for the diagnosis and differentiation of various ossicular disorders in patients with intact tympanic membranes and aerated middle ears. Patients with partial or total ossicular interruption ...

  4. On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement

    OpenAIRE

    Li, Yanlu; Segers, Patrick; Dirckx, Joris; Baets, Roel

    2013-01-01

    Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-...

  5. Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow

    OpenAIRE

    Marcos Pinotti; Faria, Edna M.

    2006-01-01

    Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA) is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurements in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiment...

  6. Doppler cooling with coherent trains of laser pulses and tunable "velocity comb"

    OpenAIRE

    Ilinova, Ekaterina; Ahmad, Mahmoud; Derevianko, Andrei

    2011-01-01

    We explore the possibility of decelerating and Doppler cooling of an ensemble of two-level atoms by a coherent train of short, non-overlapping laser pulses. We develop a simple analytical model for dynamics of a two-level system driven by the resulting frequency comb field. We find that the effective scattering force mimics the underlying frequency comb structure. The force pattern depends strongly on the ratio of the atomic lifetime to the repetition time and pulse area. Fo...

  7. Laser doppler myography (LDMi): A novel non-contact measurement method for the muscle activity

    OpenAIRE

    Scalise, L; Casaccia, S; Marchionni, P; Ercoli, I; Tomasini, EP

    2013-01-01

    Background and aims: Electromyography (EMG) is considered the gold-standard for the evaluation of muscle activity. Transversal and dimensional changes of the muscle, during muscle activity, generate vibrational phenomena which can be measured by Laser Doppler Vibrometry (LDVi). There is a relationship between muscle contraction and vibrational activity, therefore, some information on fundamental muscle parameters can be assessed without contact with LDVi. In this paper, we explore the possibi...

  8. Laser Doppler spectroscopy of atomic hydrogen in the photodissociation of HI

    International Nuclear Information System (INIS)

    Laser induced fluorescence Doppler spectroscopy has been applied for the first time to atomic hydrogen using tunable vuv light at the Lyman-? line. The dissociation of HI at 266 nm into H+I(Psub(1/2)) and H+I(Psub(3/2)) has been investigated. The recoil energy, angular distribution and branching ratio of the H atom have been measured, serving to test and study the feasibility and applicability of the technique. (orig.)

  9. Doppler-free optogalvanic spectroscopy using an infrared color center laser

    International Nuclear Information System (INIS)

    We have used a cw color center laser near 2.6 ?m to study highly excited states in helium and neon atoms by Doppler-free intermodulated optogalvanic spectroscopy in a hollow cathode discharge tube. For helium n = 4 to 6 transitions, the resolution was limited to about 320 MHz (FWHM) by Holtzmark broadening due to the presence of charged particles in the discharge. Lines as narrow as 60 MHz were observed for neon 3s5-5p10. (orig.)

  10. Venous Small Bowel Infarction: Intraoperative Laser Doppler Flowmetry Discriminates Critical Blood Supply and Spares Bowel Length

    OpenAIRE

    S. A. Käser; Glauser, P. M.; Maurer, C. A.

    2012-01-01

    Introduction. In mesenteric infarction due to arterial occlusion, laser Doppler flowmetry and spectrometry are known reliable noninvasive methods for measuring microvascular blood flow and oxygen utilisation. Case Presentation. As an innovation we used these methods in a patient with acute extensive mesenteric infarction due to venous occlusion, occurring after radical right hemicolectomy. Aiming to avoid short bowel syndrome, we spared additional 110?cm of small bowel, instead of leaving onl...

  11. A Systematic Review of the Evolution of Laser Doppler Techniques in Burn Depth Assessment

    OpenAIRE

    Manaf Khatib; Shehab Jabir; Edmund Fitzgerald O’Connor; Bruce Philp

    2014-01-01

    Aims. The introduction of laser Doppler (LD) techniques to assess burn depth has revolutionized the treatment of burns of indeterminate depth. This paper will systematically review studies related to these two techniques and trace their evolution. At the same time we hope to highlight current controversies and areas where further research is necessary with regard to LD imaging (LDI) techniques. Methods. A systematic search for relevant literature was carried out on PubMed, Medline, EMBASE, an...

  12. Local Heating as a Predilatation Method for Measurement of Vasoconstrictor Responses with Laser-Doppler Flowmetry

    OpenAIRE

    Henricson, Joakim; Baiat, Yashma; Sjöberg, Folke

    2011-01-01

    Studying microvascular responses to iontophoresis of vasoconstricting drugs contributes to a better understanding of the regulatory mechanisms of cutaneous vessels, but measuring these responses with laser-Doppler flowmetry at basal blood flow conditions is technically challenging. This study aimed to investigate whether the measurement of cutaneous vasoconstrictor responses to noradrenaline (NA) and phenylephrine (PE), delivered by iontophoresis, is facilitated by predilatation of the microv...

  13. Quantitative analysis of skin flap blood flow in the rat using laser Doppler velocimetry.

    OpenAIRE

    Marks, N J

    1985-01-01

    Two experiments carried out on rat skin flaps are described, where microvascular flow has been measured noninvasively by a laser Doppler velocimeter. Using this technique it is possible to define the limits of an axial pattern flap in terms of microvascular flow; this was found to increase when the flap is elevated. 'Random-pattern' perfusion is defined by a fall in flow. This recovers sequentially along the flap, and at a constant rate at all sites. A differential in microvascular perfusion ...

  14. Suitability of Laser Doppler Velocimetry for the Calibration of Pressure Microphones

    OpenAIRE

    Degroot, Anne; MacDonald, Robert; Richoux, Olivier; Gazengel, Bruno; Campbell, Murray

    2007-01-01

    The details of a new approach for absolute calibration of microphones, based on the direct measurement of acoustic particle velocity using Laser Doppler Velocimetry (LDV), are presented and discussed. The calibration technique is carried out inside a tube in which plane waves propagate and closed by a rigid termination. The method developed proposes to estimate the acoustic pressure with two velocity measurements and a physical model. Minimum theoretical uncertainties on the estimated pressur...

  15. 3D flow measurements in nuclear fuel rod bundles using Laser Doppler velocimetry

    International Nuclear Information System (INIS)

    Using a two color Laser Doppler velocimeter, mean velocities and turbulence intensities have been measured in a complex geometric structure close to the 17 x 17 square lattice nuclear fuel rod bundles. Good accuracy of the control volume location and high data rate acquisition have been achieved. Comparisons are made between four different optical configurations measuring the same phenomenon. In this paper attention is focused not only on understandable discrepancies but also on unpredictable minor uncertainties

  16. Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

    OpenAIRE

    Risti? Slavica S.; Puhari? Mirjana A.; Kutin Marina M.; Mati? Dušan R.

    2010-01-01

    Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Compari...

  17. Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical traps

    CERN Document Server

    Youn, Seo Ho; Lev, Benjamin L

    2010-01-01

    Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit population-wide sub-Doppler cooling due to their near degeneracy of excited and ground state Lande g factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Doppler-cooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degen...

  18. An advanced laser-Doppler velocimeter for full-vector particle position and velocity measurements

    International Nuclear Information System (INIS)

    An advanced laser-Doppler measurement technique has been developed for fully resolved three-component particle position and velocity vector measurements in turbulent flows. The instrument deemed the 'comprehensive' laser-Doppler velocimeter employs a novel optical arrangement to measure multiple-component sub-measurement-volume-scale seed particle positions simultaneously with the velocity vector measurements of conventional laser-Doppler velocimetry (LDV). In the current paper, the effectiveness of the position resolution capabilities is considered, which allows for velocity statistics measurements at multiple locations within the measurement volume. Design estimates for the position vector uncertainties for a particle passing the measurement volume are about 3 µm root mean square in any direction, although in situ estimates indicate an uncertainty value closer to 14 µm with the possibility of further refinement through optimized alignment. To validate the operation of the instrument, measurements are presented in turbulent boundary layers previously examined with high-resolution conventional LDV. The flat-plate turbulent boundary layer is studied at two Reynolds numbers up to Re? = 7500. Measurements are also presented in a pressure-driven three-dimensional turbulent boundary layer created beside a wing/body junction. These measurements illustrate the effectiveness of the technique for obtaining highly resolved velocity profiles within the measurement locity profiles within the measurement volume and give the highest spatial resolution velocity statistics published for Reynolds numbers of the magnitude studied

  19. Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical traps

    International Nuclear Information System (INIS)

    Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit populationwide sub-Doppler cooling due to their near degeneracy of excited- and ground-state Landeg factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Doppler-cooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degenerate g factors.

  20. Laser Doppler flowmetry signals to quantify effects of isoflurane on the peripheral cardiovascular system of healthy rats

    Science.gov (United States)

    Humeau, Anne; Fizanne, Lionel; Roux, Jérôme; Asfar, Pierre; Cales, Paul; Rousseau, David; Chapeau-Blondeau, François

    2007-12-01

    The optical Doppler effect resulting from interactions between laser light photons and red blood cells of the microcirculation is used to characterize the influence of isoflurane, an halogenated volatile anesthetic, on the peripheral cardiovascular system. After having recorded laser Doppler flowmetry blood perfusion signals on isoflurane-induced anesthetized healthy rats, wavelet analyses show a significant decrease of the myogenic and neurogenic activities when isoflurane dose increases from 1.5% to 3%. Moreover, the approximate entropy shows a weak decrease of signal irregularity when dose of isoflurane increases. These findings demonstrate the usefulness of the optical Doppler effect in physiological and pharmacological applications.

  1. Coherent summation of spatially distorted laser Doppler signals by using a two-dimensional heterodyne detector array

    Science.gov (United States)

    Chan, Kin P.; Killinger, Dennis K.

    1992-01-01

    Phase-sensitive coherent summation of individual heterodyne detector array signals was demonstrated for the enhanced detection of spatially distorted laser Doppler returns. With the use of a 2 x 2 heterodyne detector array, the phase and amplitude of a time-varying speckle pattern was detected, and the signal-to-noise ratio of the Doppler shift estimate was shown to be improved by a factor of 2, depending on the extent of spatial coherence loss. These results are shown to agree with a first-order analysis and indicate the advantage of coherent summation for both short-range laser Doppler velocimetry and long-range atmospheric coherent lidar.

  2. New Laser Doppler Velocimetry with Wide Dynamic Range and Clear Directional Discrimination

    Science.gov (United States)

    Gui, Hua-Qiao; Lü, Liang; He, De-Yong; Xu, Jun; Xie, Jian-Ping; Zhao, Tian-Peng; Wang, An-Ting; Ming, Hai

    2005-06-01

    We present a new laser Doppler velocimetry based on self-mixing effect using a single longitudinal-mode vertical-cavity surface-emitting laser modulated by a dynamic triangular current. It can indicate the direction of velocity without ambiguity in a wide dynamic range of 5.2-479.9 mm/s. The accuracy of velocity measurement is better than 3.1% in the whole velocity range when a diffusing target is used for measurements. More interestingly, it works very well on different diffusing surfaces, even on a black glossy photographic paper.

  3. Comparative study of the performance of semiconductor laser based coherent Doppler lidars

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    Coherent Doppler Lidars (CDLs), operating at an eye-safe 1.5-micron wavelength, have found promising applications in the optimization of wind-power production. To meet the wind-energy sector's impending demand for more cost-efficient industrial sensors, we have focused on the development of continuous-wave CDL systems using compact, inexpensive semiconductor laser (SL) sources. In this work, we compare the performance of two candidate emitters for an allsemiconductor CDL system: (1) a monolithic master-oscillator-power-amplifier (MOPA) SL and (2) an external-cavity tapered diode laser (ECTDL).

  4. The remote measurement of tornado-like flows employing a scanning laser Doppler system

    Science.gov (United States)

    Jeffreys, H. B.; Bilbro, J. W.; Dimarzio, C.; Sonnenschein, C.; Toomey, D.

    1977-01-01

    The paper deals with a scanning laser Doppler velocimeter system employed in a test program for measuring naturally occurring tornado-like phenomena, known as dust devils. A description of the system and the test program is followed by a discussion of the data processing techniques and data analysis. The system uses a stable 15-W CO2 laser with the beam expanded and focused by a 12-inch telescope. Range resolution is obtained by focusing the optical system. The velocity of each volume of air (scanned in a horizontal plane) is determined from spectral analysis of the heterodyne signal. Results derived from the measurement program and data/system analyses are examined.

  5. Doppler wind lidar using a MOPA semiconductor laser at stable single-frequency operation

    OpenAIRE

    Rodrigo, Peter John; Pedersen, Christian

    2009-01-01

    A compact master-oscillator power-amplifier semiconductor laser (MOPA-SL) is a good candidate for a coherent light source (operating at 1550 nm) in a Doppler wind Lidar. The MOPA-SL requires two injection currents: Idfb for the distributed-feedback (DFB) laser section (master oscillator) and Iamp for the tapered amplifier section. The specified maximum current values are 0.7 A and 4.0 A for Idfb and Iamp. Although the MOPA-SL has been proven capable of producing single-frequency CW output bea...

  6. Flexural vibration spectra of carbon nanotubes measured using laser Doppler vibrometry

    International Nuclear Information System (INIS)

    Laser Doppler vibrometry is used to measure the thermal vibration spectra of individual multiwalled carbon nanotubes (MWNTs) under ambient conditions. Since the entire vibration spectrum is measured with high frequency resolution, the resonant frequencies and quality factors of the MWNTs are accurately determined, allowing for estimates of their elastic moduli. Because the diameters of the MWNTs studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate values for the smallest diameter nanotube or nanowire whose vibration can be measured in this way.

  7. Incident beam polarization for laser Doppler velocimetry employing a sapphire cylindrical window

    Science.gov (United States)

    Lock, J. A.; Schock, H. J.

    1985-01-01

    For laser Doppler velocimetry studies employing sapphire windows as optical access ports, the birefringency of sapphire produces an extra beam intersection volume which serves to effectively smear the acquired velocity flow field data. It is shown that for a cylindrical window geometry, the extra beam intersection volume may be eliminated with minimal decrease in the fringe visibility of the remaining intersection volume by suitably orienting the polarizations of the initial laser beams. For horizontally incident beams, these polarizations were measured at three intersection locations within the cylinder. It was found that the measured polarization angles agreed with the theoretical predictions.

  8. Measurement of isotope ratios by Doppler-free laser spectroscopy applying semiconductor diode lasers and thermionic diode detection

    International Nuclear Information System (INIS)

    In this correspondence, where preliminary results of isotope ratio measurements in Ba are given, the authors will demonstrate the simple but powerful application of diode lasers in isotope-selective trace element detection and isotope dilution techniques using LEI Doppler-free two-photon spectroscopy and thermionic diode detection, which may become an easy to operate and low-cost alternative to mass spectrometry

  9. Ultrasonic detection of photothermal interaction of lasers with tissue using a pulsed Doppler system

    Science.gov (United States)

    Ying, Hao; Azeemi, Aamer; Hartley, Craig J.; Motamedi, Massoud; Bell, Brent A.; Rastegar, Sohi; Sheppard, L. C.

    1995-05-01

    Thermal therapy using various heating sources such as lasers or microwaves to destroy benign and malignant lesions has recently gained widespread acceptance. However, the accurate prediction of thermal damage in tissue according to theoretical or computer modeling is difficult and unreliable due to target variability with respect to physical properties, geometry, and blood perfusion. Thus, one of the major obstacles to application of thermal therapies has been the lack of a noninvasive, real-time method that could determine the extent and geometry of treated tissue. To evaluate the effects of laser heating on tissue, we have developed an analog-digital hybrid Doppler ultrasound system to measure the phase and amplitude of ultrasonic echoes returned from the heated tissue. The system consists of an eight-gate pulsed Doppler detector, a 16-channel 12-bit A/D converter, and a signal analysis and visualization software package. In vitro studies using canine liver showed two distinct types of modulation of the echoes along the ultrasound beam path during laser irradiation using an 810 nm diode laser. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 2 signals showed large and rapid variations in amplitude and phase which usually appeared after tissue surface explosion and were indicative of tissue ablation. We hypothesize that the observed phase changes in type 1 signals are due to thermal effects within the tissue consistent with tissue expansion and contraction while the phase changes in type 2 signals are likely due to formation and motion of gas bubbles in the tissue. A further development of the Doppler ultrasound technique could lead to the generation of feedback information needed for monitoring and automatic control of thermal treatment using various heating modalities such as laser, high intensity focused ultrasound, microwaves, or radio frequency waves.

  10. Medical diagnosis of the cardiovascular system on the carotid artery with IR laser Doppler vibrometer

    Science.gov (United States)

    Mignanelli, Laura; Rembe, Christian; Kroschel, Kristian; Luik, Armin; Castellini, Paolo; Scalise, Lorenzo

    2014-05-01

    Laser Doppler Vibrometry (LDV) is known to be a possible diagnosis tool for many cardiac applications as the detection and monitoring of some important vital parameters (Heart Rate, Heart Rate Variability, Pulse Wave Velocity) in a non-contact and non-intrusive way. The technique has become known as Optical Vibrocardiography (VCG) i.e. by measuring the vibrations on the carotid artery or on the thorax [1-5]. The aim of the present study is to interpret the vibrational signal acquired from the carotid artery in relation to the electrocardiographic and hemodynamic aspects and to enable the extraction of further medical information relevant for diagnosis purpose. For the investigation an infrared (IR) Laser Doppler Vibrometer has been used. The acquired VCG signals have been processed and compared with the simultaneously acquired electrocardiogram and the color-coded Doppler sonogram. This has enabled a deeper understanding of the signature of the vibrational signal. Furthermore, in this paper, we also discuss the medical value of the VCG signal obtained from the carotid artery.

  11. A source of error in the velocity measurement of large spherical bubbles using laser Doppler anemometry

    International Nuclear Information System (INIS)

    This article reports a source of error in the velocity measurements of large spherical bubbles by laser Doppler anemometry. Experimental evidences gathered in Poiseuille bubbly flows, as well as on controlled bubble streets, show that, for a detector at a 90 deg. viewing angle, the velocity of millimeter size spherical bubbles can be underestimated by 15%. Such a bias is shown to arise from the interaction on the receiver of two optical contributions, one from external reflection and one from internal reflection, produced from the same bubble. Their combination leads to alterations of the Doppler frequency inside a burst, and hence, to improper velocity measurements. An analysis based on geometrical optics indicates that such a combination is possible only for a ratio of the probe volume to the bubble diameter larger than unity. Such a conclusion is supported by careful experiments. Finally, simple ways of avoiding this bias are proposed and validated

  12. Doppler cooling with coherent trains of laser pulses and a tunable velocity comb

    International Nuclear Information System (INIS)

    We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, nonoverlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a ''velocity comb''--a series of narrow equidistant peaks in the velocity space.

  13. Laser doppler velocimeter on the base of an image converter and photomultiplier

    International Nuclear Information System (INIS)

    A laser-Doppler velocimeter (DV) is described in which discrimination and registration of the Doppler frequency is performed by an image converter operating from photomultiplier pulses. The LDV under consideration is intended measuring velocities in steady and unsteady gas flows and can be used when there are insignificant concentrations of microparticles artificially introduced into the flow and, in some cases, when the flow contains naturally-present microparticles. The LVD flowsheet and circuits of control units are considered. The proposed LDV allows measurements of gas flow velocities in the range from 10-3 to 104 m/s. A conclusion has been drawn that the proposed LDV combines a high sensitivity of a photomultiplier-based LDV with the possibility of operation in a wide range of velocity measurement inherent in an LDV using a Fabry-Perot interferometer

  14. Self-mixing laser Doppler flow sensor: an optofluidic implementation.

    Science.gov (United States)

    Nikoli?, Milan; Hicks, Elaine; Lim, Yah Leng; Bertling, Karl; Raki?, Aleksandar D

    2013-11-20

    We present the miniaturization of self-mixing interferometry (SMI) into a microfluidic circuit using an optical fiber, forming an optofluidic device that can be used as a component in lab on a chip systems. We characterize the performance of the device as a fluid velocity (and hence flow) sensor, showing it to produce good accuracy and correlation with theory over a range of velocities from 0.5 to 60??mm/s and almost four decades of scatterer concentration. SMI in an optofluidic system has the advantage that only a single path to the optical inspection point is needed, as the laser source is also the receiver of light. In addition, the same system that is used for measuring fluid velocity can be used to measure other quantities such as particle size. The configuration presented is inherently easy to optically align due to the self-aligned property of SMI and divergent nature of light exiting the embedded optical fiber, providing for low-cost manufacturing. PMID:24513768

  15. Nonlinear ultrasonic image of fatigue cracks by using laser doppler vibrometry

    International Nuclear Information System (INIS)

    A nonlinear acoustic effect is a sensitive tool to detect a micro-scale crack or the early stage of cracking during the fatigue process. Such damage produces a nonlinear stress-strain relationship, and the nonlinearity can be measured by a higher harmonic component in the frequency domain. The 2nd harmonic component and higher harmonic components are subtracted using laser Doppler vibrometry. Because the laser beam can be focused on the smallest spot, the localized nonlinear acoustic parameters can be determined. As the damage increases, the level of nonlinearity increases, which can be used for the diagnosis of micro-cracks. Using a scanning laser beam, localized nonlinear acoustic parameters can be mapped around a cracked specimen. Various nonlinear parameters are chosen and tested around the crack tip, and the most sensitive nonlinear parameter for a micro-crack or closed crack can be optimized

  16. Nonlinear ultrasonic image of fatigue cracks by using laser doppler vibrometry

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Yong Moo; Kim, Ha Nam; Lee, Duck Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    A nonlinear acoustic effect is a sensitive tool to detect a micro-scale crack or the early stage of cracking during the fatigue process. Such damage produces a nonlinear stress-strain relationship, and the nonlinearity can be measured by a higher harmonic component in the frequency domain. The 2{sup nd} harmonic component and higher harmonic components are subtracted using laser Doppler vibrometry. Because the laser beam can be focused on the smallest spot, the localized nonlinear acoustic parameters can be determined. As the damage increases, the level of nonlinearity increases, which can be used for the diagnosis of micro-cracks. Using a scanning laser beam, localized nonlinear acoustic parameters can be mapped around a cracked specimen. Various nonlinear parameters are chosen and tested around the crack tip, and the most sensitive nonlinear parameter for a micro-crack or closed crack can be optimized.

  17. Dynamics of shocks in laser-launched flyer plates probed by photon Doppler velocimetry

    Science.gov (United States)

    Curtis, A. D.; Dlott, D. D.

    2014-05-01

    We investigated the launch and impact with glass targets for four different thicknesses of Al laser-launched flyer plates by monitoring the flight with photon Doppler velocimetry (PDV). The amplitudes and damping times of the reverberating shocks in the flyers, created by short laser pulse launching, were investigated as a function of pulse duration using 10 or 20 ns laser pulses. The shorter pulse duration showed a surprisingly more efficient damping process in the thicker flyers. The durations of the supported shocks in the glass targets were also measured as a function of flyer thickness. The supported shock durations were significantly shorter than the common picture of shock round-trip transit time in the flyer.

  18. Performance analysis of continuous tracking laser Doppler vibrometry applied to rotating structures in coast-down

    International Nuclear Information System (INIS)

    In this paper a performance analysis of the so-called tracking continuous scanning laser Doppler vibrometry (TCSLDV) exploited in coast-down has been performed. This non-contact measurement system is able to scan continuously over a rotating surface during coast-down and to determine vibration operational deflection shapes (ODSs) and natural frequencies in short time, i.e. the temporal extent of the coast-down. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the whole rotor surface synchronously with its rotation, so that the LDV output is modulated by the structure's ODSs. This technique has a full-field nature that enables it to measure simultaneously the time and spatial dependence of the vibration in a unique measurement. However, the TCSLDV presents some criticalities in practical applications, especially when applied to rotary transient and fast processes. In fact, if the vibration is transient and decays very fast, then the laser beam could not have had the time to scan the complete structure surface and the modulation of the ODS could be partial. An analytical model reproducing a representative experiment has been developed in order to evaluate the sensitivity of results to testing conditions. The laser beam trajectory in both the fixed and rotating reference systems has been synthesized showing its dependence on experimental parameters as the rotation speed variation during coast-down. It has been demonstrated the decrease in speed induces the deformation of the laser trajectory influencing the LDV output time history, spectrum and consequently the recovered ODS. (paper)

  19. Eulerian laser Doppler vibrometry: Online blade damage identification on a multi-blade test rotor

    Science.gov (United States)

    Oberholster, A. J.; Heyns, P. S.

    2011-01-01

    Laser Doppler vibrometry enables the telemetry-free measurement of online turbomachinery blade vibration. Specifically, the Eulerian or fixed reference frame implementation of laser vibrometry provides a practical solution to the condition monitoring of rotating blades. The short data samples that are characteristic of this measurement approach do however negate the use of traditional frequency domain signal processing techniques. It is therefore necessary to employ techniques such as time domain analysis and non-harmonic Fourier analysis to obtain useful information from the blade vibration signatures. The latter analysis technique allows the calculation of phase angle trends which can be used as indicators of blade health deterioration, as has been shown in previous work for a single-blade rotor. This article presents the results from tests conducted on a five-blade axial-flow test rotor at different rotor speeds and measurement positions. With the aid of artificial neural networks, it is demonstrated that the parameters obtained from non-harmonic Fourier analysis and time domain signal processing on Eulerian laser Doppler vibrometry signals can successfully be used to identify and quantify blade damage from among healthy blades. It is also shown that the natural frequencies of individual blades can be approximated from the Eulerian signatures recorded during rotor run-up and run-down.

  20. Monostatic coaxial 1.5 ?m laser Doppler velocimeter using a scanning Fabry-Perot interferometer

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2013-01-01

    We present a laser Doppler velocimeter (LDV) in monostatic coaxial arrangement consisting of off-the-shelf telecom-grade components: a single frequency laser (wavelength ? = 1.5 ?m) and a high-finesse scanning Fabry-Perot interferometer (sFPI). In contrast to previous 1.5 ?m LDV systems based on heterodyne detection, our sFPI-LDV has the advantages of having large remote sensing range not limited by laser coherence, high velocity dynamic range not limited by detector bandwidth and inherent sign discrimination of Doppler shift. The more optically efficient coaxial arrangement where transmitter and receiver optics share a common axis reduces the number of components and greatly simplifies the optical alignment. However, the sensitivity to unwanted backreflections is increased. To circumvent this problem, we employ a custom optical circulator design which compared to commercial fiber-optic circulator achieves ~40 dB reduction in strength of unwanted reflections (i.e. leakage) while maintaining high optical efficiency. Experiments with a solid target demonstrate the performance of the sFPI-LDV system with high sensitivity down to pW level at present update rates up to 10 Hz.

  1. Experimental and clinical application of laser doppler flowmetry in gastric and duodenal ulcerative bleedings

    Directory of Open Access Journals (Sweden)

    Afanasieva G.A.

    2011-12-01

    Full Text Available The research goal is to develop a new objective diagnostic method of prerecurrence syndrome that will prognose bleeding recurrence from gastroduodenal ulcers. Materials and methods. Method of laser Doppler flowmetry (LDF of the regional perfusion of tissue has been used. The experimental part has been done on 30 white laboratory rats. Characteristics of regional tissue perfusion in the simulation and laser hemostasis of bleeding have been studied. Gastroduodenal endoscopy has been performed with laser Doppler flowmetry (ELDF in clinical conditions to predict the recurrence of ulcerative bleeding. The prognostic method of gastroduodenal ulcerative bleeding was used in 58 patients hospitalized with such pathology and activity of bleeding Forrest II. Results. The study of microcirculation parameters and experimental hemostasis has showed the possibility of using LDF to measure its performance. Effective hemostasis has been accompanied by a significant decrease in perfusion. On the basis of microcirculation parameters in ulcerative bleeding, medical adrenaline test has been proposed for an objective verification pre-recurrence syndrome. To evaluate the effectiveness of endoscopic hemostasis perfusion has been measured before and after its implementation. Conclusion. ELDF has objectified the prognosis of ulcerative bleeding recurrence, verified pre-recurrence syndrome and evaluated the efficacy of endoscopic hemostasis

  2. Monostatic coaxial 1.5 ?m laser Doppler velocimeter using a scanning Fabry-Perot interferometer.

    Science.gov (United States)

    Rodrigo, Peter John; Pedersen, Christian

    2013-09-01

    We present a laser Doppler velocimeter (LDV) in monostatic coaxial arrangement consisting of off-the-shelf telecom-grade components: a single frequency laser (wavelength ? = 1.5 ?m) and a high-finesse scanning Fabry-Perot interferometer (sFPI). In contrast to previous 1.5 ?m LDV systems based on heterodyne detection, our sFPI-LDV has the advantages of having large remote sensing range not limited by laser coherence, high velocity dynamic range not limited by detector bandwidth and inherent sign discrimination of Doppler shift. The more optically efficient coaxial arrangement where transmitter and receiver optics share a common axis reduces the number of components and greatly simplifies the optical alignment. However, the sensitivity to unwanted backreflections is increased. To circumvent this problem, we employ a custom optical circulator design which compared to commercial fiber-optic circulator achieves ~40 dB reduction in strength of unwanted reflections (i.e. leakage) while maintaining high optical efficiency. Experiments with a solid target demonstrate the performance of the sFPI-LDV system with high sensitivity down to pW level at present update rates up to 10 Hz. PMID:24103985

  3. Full-field laser-Doppler imaging and its physiological significance for tissue blood perfusion

    International Nuclear Information System (INIS)

    Using Monte Carlo simulations for a semi-infinite medium representing a skeletal muscle tissue, it is demonstrated that the zero- and first-order moments of the power spectrum for a representative pixel of a full-field laser-Doppler imager behave differently from classical laser-Doppler flowmetry. In particular, the zero-order moment has a very low sensitivity to tissue blood volume changes, and it becomes completely insensitive if the probability for a photon to interact with a moving red blood cell is above 0.05. It is shown that the loss in sensitivity is due to the strong forward scatter of the propagating photons in biological tissues (i.e., anisotropy factor g = 0.9). The first-order moment is linearly related to the root mean square of the red blood cell velocity (the Brownian component), and there is also a positive relationship with tissue blood volume. The most common physiological interpretation of the first-order moment is as tissue blood volume times expectation of the blood velocity (in probabilistic terms). In this sense, the use of the first-order moment appears to be a reasonable approach for qualitative real-time blood flow monitoring, but it does not allow us to obtain information on blood velocity or volume independently. Finally, it is shown that the spatial and temporal resolution trade-off imposed by the CMOS detectors, used in full-field laser-Doppler hardware, may lead to measurements that vary oppositely with the underlying physiological quanely with the underlying physiological quantities. Further improvements on detectors' sampling rate will overcome this limitation.

  4. Homodyne laser Doppler vibrometer on silicon-on-insulator with integrated 90 degree optical hybrids.

    Science.gov (United States)

    Li, Yanlu; Baets, Roel

    2013-06-01

    A miniaturized homodyne laser Doppler vibrometer (LDV) with a compact 90° optical hybrid is experimentally demonstrated on a CMOS compatible silicon-on-insulator (SOI) platform. Optical components on this platform usually have inadequate suppressions of spurious reflections, which significantly influence the performance of the LDV. Numerical compensation methods are implemented to effectively decrease the impact of these spurious reflections. With the help of these compensation methods, measurements for both super-half-wavelength and sub-half-wavelength vibrations are demonstrated. Results show that the minimal detectable velocity is around 1.2 ?m/s. PMID:23736586

  5. Use of a laser doppler vibrometer for high frequency accelerometer characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, V.I.; Hansche, B.D.; Solomon, O.M.

    1995-12-31

    A laser doppler vibrometer (LDV) is being used for high frequency characterizations of accelerometers at Sandia National Laboratories (SNL). A LDV with high frequency (up to 1.5 MHz) and high velocity (10 M/s) capability was purchased from a commercial source and has been certified by the Primary Electrical Standards Department at SNL. The method used for this certification and the certification results are presented. Use of the LDV for characterization of accelerometers at high frequencies and of accelerometer sensitivity to cross-axis shocks on a Hopkinson bar apparatus is discussed.

  6. Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

    Directory of Open Access Journals (Sweden)

    Risti? Slavica S.

    2010-01-01

    Full Text Available Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp was experimentally determined by Laser Doppler Anemometry (LDA measurements. Two models were tested: model of airplane G4 (Super Galeb and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles.

  7. Laser frequency stabilization on sub-doppler resonances in thin gas cells

    International Nuclear Information System (INIS)

    This paper is the brief review on the laser frequency stabilization methods by means of subb-doppler absorption and fluorescence resonances (on centers of quantum transitions), which arise because of the specific optical selection of comparatively slow-speed atoms in a thin cell with a rarefied gas. It is considered two following mechanisms of such a velocity selection of atomic particles connected with their flight durations between walls of the thin cell : 1) optical pumping of sublevels of the ground atomic term and optical excitation of long-lived quantum levels

  8. Influence Of Optical Properties and Fiber separation on Laser Doppler Flowmetry

    OpenAIRE

    Larsson, Marcus; Steenbergen, Wiendelt; Stro?mberg, Tomas

    2002-01-01

    Microcirculatory blood flow can be measured using a laser Doppler flowmetry (LDF) probe. However, the readings are affected by tissue optical properties (absorption and scattering coefficient; µa and µs) and probe geometry. In this study the influence of optical properties (µa?[0.053, 0.23] mm-1; µs?[14.7, 45.7] mm-1) on LDF perfusion and sampling depth were evaluated for different fiber separations. In-vitro measurements were made on a sophisticated tissue phantom with known optical ...

  9. A laser Doppler approach to cardiac motion monitoring: effects of surface and measurement position

    Science.gov (United States)

    Scalise, Lorenzo; Morbiducci, Umberto; De Melis, Mirko

    2006-06-01

    In this paper we present a novel, non-invasive measurement system for optical monitoring of the cardiac rate. This measurement method, called vibrocardiography (VCG), is based on the use of a laser Doppler vibrometer for the measurement of the velocity of displacement of the skin in correspondence of the chest wall. We report the typical VCG signals measured on 4 healthy subject and in particular, we investigated the effect on the signal of the measurement position respect to the chest wall as well as the effect of the surface characteristics on the measured signal.

  10. Measurement of turbulent flow using ultrasound velocity profile method. 2. Comparison with laser doppler velocimetry

    International Nuclear Information System (INIS)

    Ultrasonic Velocity Profile (UVP) measuring method has many advantages over the conventional flow measurement methods, such as measurement of an instantaneous velocity profile on a line with the transducer was measured, and it is applicable to opaque liquids because of possible to measure from outside of the wall. This method has capabilities applicable to various flow measurements, but requires a large measurement volume. In this paper, the effect of the measurement volume on the mean velocity profile have been investigated for fully developed turbulent flows in a vertical pipe and was compared with a result obtained by Direct Numerical Simulation (DNS) and results of Laser Doppler Velocimetry (LDV) measurement. (author)

  11. The application of laser Doppler velocimetry to trailing vortex definition and alleviation

    Science.gov (United States)

    Orloff, K. L.; Grant, G. R.

    1973-01-01

    A laser Doppler velocimeter whose focal volume can be rapidly traversed through a flowfield has been used to overcome the problem introduced by excursions of the central vortex filament within a wind tunnel test section. The basic concepts of operation of the instrument are reviewed and data are presented which accurately define the trailing vortex from a square-tipped rectangular wing. Measured axial and tangential velocity distributions are given, both with and without a vortex dissipator panel installed at the wing tip. From the experimental data, circulation and vorticity distributions are obtained and the effect of turbulence injection into the vortex structure is discussed.

  12. Measurement of fluid velocity development in laminar pipe flow using laser Doppler velocimetry

    Science.gov (United States)

    Molki, Arman; Khezzar, Lyes; Goharzadeh, Afshin

    2013-09-01

    In this paper we present a non-intrusive experimental approach for obtaining velocity gradient profiles in a transparent smooth pipe under laminar flow conditions (Re = 925) using a laser Doppler velocimeter (LDV). Measurements were taken within the entrance region of the pipe at l = 300 mm and l = 600 mm from the pipe inlet, in addition to measurements of the fully developed flow at l = 1800 mm. The obtained results show how the velocity profile from upstream of the pipe develops into a classical laminar profile downstream, which matches the theoretical profile well. Additionally, a brief summary of historical information about the development of flow measurement techniques, in particular LDV, is provided.

  13. The Use of a Laser Doppler Velocimeter in a Standard Flammability Tube

    Science.gov (United States)

    Strehlow, R. A.; Flynn, E. M.

    1985-01-01

    The use of the Laser Doppler Velocimeter, (LDV), to measure the flow associated with the passage of a flame through a standard flammability limit tube (SFLT) was studied. Four major results are presented: (1) it is shown that by using standard ray tracing calculations, the displacement of the LDV volume and the fringe rotation within the experimental error of measurement can be predicted; (2) the flow velocity vector field associated with passage of an upward propagating flame in an SFLT is determined; (3) it is determined that the use of a light interruption technique to track particles is not feasible; and (4) it is shown that a 25 mW laser is adequate for LDV measurements in the Shuttle or Spacelab.

  14. A 3-component laser-Doppler velocimeter data acquisition and reduction system

    Science.gov (United States)

    Rodman, L. C.; Bell, J. H.; Mehta, R. D.

    1986-01-01

    This report describes a laser Doppler velocimeter capable of measuring all three components of velocity simultaneously in low-speed flows. All the mean velocities, Reynolds stresses, and higher-order products can then be evaluated. The approach followed is to split one of the colors used in a 2-D system, thus creating a third set of beams which is then focused in the flow from an off-axis direction. The third velocity component is computed from the known geometry of the system. In this report, the laser optical hardware and the data acquisition electronics are described in detail. In addition, full operating procedures and listings of the software (written in BASIC and assembly languages) are also included. Some typical measurements obtained with this system in a vortex/mixing layer interaction are presented and compared directly to those obtained with a cross-wire system.

  15. IN-PLANE MODAL TESTING OF A FREE ISOTROPIC PLATE USING LASER DOPPLER VIBROMETER MEASUREMENTS

    International Nuclear Information System (INIS)

    In this work an experimental procedure is proposed to obtain the lowest free in-plane vibration modes of an aluminum plate. Responses are measured along two longitudinal directions on the plate surface at selected points by an out-of-plane laser Doppler vibrometer set up to measure in-plane vibrations. Excitation is made at one specific point of the plate edge using a light impact hammer. The plate is supported by silicone spheres to simulate the free edge boundary conditions and ensure a stable stationary position in order to keep the laser focus distance. Numerical finite element simulations are carried out to compute the in-plane modes and frequencies in order to compare them with the corresponding experimental results. The identified experimental modes agree very well with the numerical predictions. The smooth in-plane modes can be used to identify the plate material constitutive model parameters using existing methods proposed elsewhere by the authors.

  16. High resolution laser induced fluorescence Doppler velocimetry utilizing saturated absorption spectroscopy

    International Nuclear Information System (INIS)

    A high resolution laser induced fluorescence (LIF) system has been developed to measure the flow velocity field of neutral particles in an electron-cyclotron-resonance argon plasma. The flow velocity has been determined by the Doppler shift of the LIF spectrum, which is proportional to the velocity distribution function. Very high accuracy in velocity determination has been achieved by installing a saturated absorption spectroscopy unit into the LIF system, where the absolute value and scale of laser wavelength are determined by using the Lamb dip and the fringes of a Fabry-Perot interferometer. The minimum detectable flow velocity of a newly developed LIF system is ±2 m/s, and this performance remains unchanged in a long-time experiment. From the radial measurements of LIF spectra of argon metastable atoms, it is found that there exists an inward flow of neutral particles associated with neutral depletion.

  17. Laser Doppler technique for nondestructive evaluation of mechanical heart valves kinematics

    Science.gov (United States)

    Grigioni, Mauro; Daniele, Carla; Morbiducci, U.; Del Gaudio, C.; D'Avenio, Giuseppe; Di Meo, D.; Barbaro, Vincenzo

    2004-06-01

    Laser techniques for vibration measurement, due to their non-contact nature, represents an interesting alternative investigational tool to be tested in biomedical and clinic fields. A particular application could be as evaluation method in design and quality control of artificial organs. Aim of this study is to investigate the application of laser vibrometry to the study of mechanical heart valves in-vitro, with an ad hoc set-up. A heterodyne laser Doppler vibrometry system, which allows the measurement of both vibrational velocity and displacement was used. Three different approaches have been carried out, in order to stress the limits of the laser vibrometry technique for testing heart valve prostheses. Critical points and difficulties to build up experimental studies in this field were clearly pointed out. In the present study only one laser head was used, the aim of the authors being to test the feasibility of a simplified approach on mechanical cardiac valves. Starting from that analysis a comparison could be made to assess the capability to discriminate between normal and malfunctioning devices. The advantage of the proposed test bench is that it could provide a non-contact, non-destructive analysis of the valve under the same working conditions as those upon implantation. The proposed method could furnish a typical "fingerprint" characterizing each valve behavior in repeatable experimental conditions.

  18. Multi-frequency, 3D ODS measurement by continuous scan laser Doppler vibrometry

    Science.gov (United States)

    Weekes, Ben; Ewins, David

    2015-06-01

    Continuous scan laser Doppler vibrometry (CSLDV) is a technique which has been described and explored in the literature for over two decades, but remains niche compared to SLDV inspection by a series of discrete-point measurements. This is in part because of the unavoidable phenomenon of laser speckle, which deteriorates signal quality when velocity data is captured from a moving spot measurement. Further, applicability of CSLDV has typically been limited to line scans and rectangular areas by the application of sine, step, or ramp functions to the scanning mirrors which control the location of the measurement laser spot. In this paper it is shown that arbitrary functions to scan any area can easily be derived from a basic calibration routine, equivalent to the calibration performed in conventional discrete-point laser vibrometry. This is extended by performing the same scan path upon a test surface from three independent locations of the laser head, and decomposing the three sets of one-dimensional deflection shapes into a single set of three-dimensional deflection shapes. The test was performed with multi-sine excitation, yielding 34 operating deflection shapes from each scan.

  19. In-situ position and vibration measurement of rough surfaces using laser Doppler distance sensors

    Science.gov (United States)

    Czarske, J.; Pfister, T.; Günther, P.; Büttner, L.

    2009-06-01

    In-situ measurement of distances and shapes as well as dynamic deformations and vibrations of fast moving and especially rotating objects, such as gear shafts and turbine blades, is an important task at process control. We recently developed a laser Doppler distance frequency sensor, employing two superposed fan-shaped interference fringe systems with contrary fringe spacing gradients. Via two Doppler frequency evaluations the non-incremental position (i.e. distance) and the tangential velocity of rotating bodies are determined simultaneously. The distance uncertainty is in contrast to e.g. triangulation in principle independent of the object velocity. This unique feature allows micrometer resolutions of fast moved rough surfaces. The novel sensor was applied at turbo machines in order to control the tip clearance. The measurements at a transonic centrifugal compressor were performed during operation at up to 50,000 rpm, i.e. 586 m/s velocity of the blade tips. Due to the operational conditions such as temperatures of up to 300 °C, a flexible and robust measurement system with a passive fiber-coupled sensor, using diffractive optics, has been realized. Since the tip clearance of individual blades could be temporally resolved an analysis of blade vibrations was possible. A Fourier transformation of the blade distances results in an average period of 3 revolutions corresponding to a frequency of 1/3 of the rotary frequency. Additionally, a laser Doppler distance sensor using two tilted fringe systems and phase evaluation will be presented. This phase sensor exhibits a minimum position resolution of ?z = 140 nm. It allows precise in-situ shape measurements at grinding and turning processes.

  20. Fractal Dimension Characterization of in-vivo Laser Doppler Flowmetry signals

    Science.gov (United States)

    Srinivasan, Gayathri; Sujatha, N.

    Laser Doppler Blood Flow meter uses tissue backscattered light to non-invasively assess the blood flow rate. qualitatively. As there is large spatial variability and the temporal heterogeneity in tissue microvasculature, the measured blood flow rate is expressed in relative units. A non-linear approach in order to understand the dynamics of the microcirculation led to the fractal characterization of the blood flow signals. The study presented in the paper aims to analyze the fractal behavior of Laser Doppler Flow (LDF) signals and to quantitatively estimate the fractal dimension of waveforms using Box-Counting method. The measured Fractal dimension is an estimate of temporal variability of tissue perfusion. The rate at which fractal dimension varies as a function of location between individuals, exhibits a weak correlation with time. Further studies with a larger number of subjects are necessary to test the generality of the findings and if changes in dimension are reproducible in given individuals. In conclusion, the fractal dimension determined by Box-counting method may be useful for characterizing LDF time series signals. Future experiments evaluating whether the technique can be used to quantify microvascular dysfunction, as commonly occurring in conditions such as Diabetes, Raynaud's phenomenon, Erythromelalgia and Achenbach syndrome needs to be evaluated.

  1. Agent-based station for on-line diagnostics by self-adaptive laser Doppler vibrometry.

    Science.gov (United States)

    Serafini, S; Paone, N; Castellini, P

    2013-12-01

    A self-adaptive diagnostic system based on laser vibrometry is proposed for quality control of mechanical defects by vibration testing; it is developed for appliances at the end of an assembly line, but its characteristics are generally suited for testing most types of electromechanical products. It consists of a laser Doppler vibrometer, equipped with scanning mirrors and a camera, which implements self-adaptive bahaviour for optimizing the measurement. The system is conceived as a Quality Control Agent (QCA) and it is part of a Multi Agent System that supervises all the production line. The QCA behaviour is defined so to minimize measurement uncertainty during the on-line tests and to compensate target mis-positioning under guidance of a vision system. Best measurement conditions are reached by maximizing the amplitude of the optical Doppler beat signal (signal quality) and consequently minimize uncertainty. In this paper, the optimization strategy for measurement enhancement achieved by the down-hill algorithm (Nelder-Mead algorithm) and its effect on signal quality improvement is discussed. Tests on a washing machine in controlled operating conditions allow to evaluate the efficacy of the method; significant reduction of noise on vibration velocity spectra is observed. Results from on-line tests are presented, which demonstrate the potential of the system for industrial quality control. PMID:24387408

  2. Assessment of measurement efficiency in laser- and phase-Doppler techniques: an information theory approach

    International Nuclear Information System (INIS)

    Laser- and phase-Doppler diagnostic techniques provide information on particle characteristics in the form of discrete probability distribution functions. Most methods assess the amount of information required for an accurate measurement through the first- and second-order moments of these distributions. However, considering that a measurement is the distribution and not its moments, a different approach is developed based on information theory (IT) concepts in order to assess if the information provided to the experimentalist is enough to ensure an accurate statistical analysis. The methodology and stopping criteria are presented and used in previously reported measurements obtained with laser- and phase-Doppler techniques. Results show that using an IT approach to assess the reliability of data provided by a measurement means evaluating the degree of stabilization of a discrete probability distribution, where more information acquired does not necessarily imply a more accurate measurement. The statistical analysis performed using the number of samples indicated by the IT method, compared to the total sample size previously measured, shows similar results. Moreover, measurement time is substantially reduced if the IT method is used, thus improving measurement efficiency. (paper)

  3. Visualization of solitary waves via laser Doppler vibrometry for heavy impurity identification in a granular chain

    International Nuclear Information System (INIS)

    We study the propagation of highly nonlinear solitary waves in a one-dimensional granular chain composed of homogeneous spherical particles that includes a heavy impurity. We experimentally investigate the transmission and backscattering behavior of solitary waves in the region of the impurity by using a laser Doppler vibrometer. To assess the sensitivity of solitary waves to various impurity masses, this non-contact measurement technique is complemented by a conventional contact measurement method based on an instrumented sensor particle. By leveraging these two schemes, we find that the travelling time and attenuation of backscattered solitary waves are highly sensitive to the location and mass of an inserted impurity. The experimental results are found to be in satisfactory agreement with the numerical results obtained from a discrete element model and the theoretical predictions based on nonlinear wave dynamics and classical contact theory. This study demonstrates that laser Doppler vibrometry can be an efficient tool to visualize highly nonlinear wave propagation in granular media. With a view towards potential applications, highly nonlinear solitary waves can be employed as nondestructive probing signals to identify heavy impurities embedded in ordered granular architectures. (paper)

  4. Doppler laser flowmetry test of the functional condition of precapillar and postcapillar resistance in essential hypertensive patients

    Science.gov (United States)

    Lukjanov, Valdimir F.

    2000-04-01

    243 patient of essential hypertension were examined with the help of Doppler-Laser Flowmetry, optical photometry. Flowmetry was used to measure vasomotion and blood flow after arterial compression, decompression and venous hyperemia were held. New Doppler-Laser flowmetry diagnostic test of functional condition of microcirculation was worked out of find precapillary and postcapillar resistance. Precapillary resistance included next basis parameters: vasomotion with high frequency and low amplitude, latent time after decompression, large postocclusive reactive hyperemia, absent venous hyperemia. Postcapillar amplitude, little or absent postocclusive reactive hyperemia, large venous hyperemia. This test-method was applied to select pathogenetic treatment of essential hypertension.

  5. Influence of intracavity doppler frequency shift in the swept-cavity ringdown spectroscopy incorporating continuous-wave laser excitation

    International Nuclear Information System (INIS)

    Cavity ringdown spectroscopy (CRDS) with continuous-wave (cw) laser excitation has added high frequency resolution to the ability of CRDS being used for the absolute quantification of trace-level species present in many chemical processes. Cavity dithering technique has easily resolved the problem of resonant coupling of a cw laser light into a high-finesse cavity. The present study addresses the potential uncertainty involved in such cw-CRDS techniques incorporating the cavity mirror motion, i.e., the doppler frequency shift of a probe light inside the cavity. In the high-resolution spectroscopic work of megahertz-accuracy, even the influence of intracavity doppler effect may become significant.

  6. Low flow vortex shedding flowmeter

    Science.gov (United States)

    Waugaman, Charles J.

    1989-01-01

    The purpose was to continue a development project on a no moving parts vortex shedding flowmeter used for flow measurement of hypergols. The project involved the design and construction of a test loop to evaluate the meter for flow of Freon which simulates the hypergol fluids. Results were obtained on the output frequency characteristics of the flow meter as a function of flow rate. A family of flow meters for larger size lines and ranges of flow was sized based on the results of the tested meter.

  7. High Resolution Self-Mixing Laser-Doppler Vibrometry with a Laser-Diode-Pumped Microchip LiNdP4O12 Laser

    Science.gov (United States)

    Otsuka, Kenju; Fukazawa, Takeki; Sekita, Nobuatsu; Higashihara, Shin-ichi

    2000-07-01

    A simple laser vibrometer system (LVS) has been built around a laser-diode-pumped microchip LiNdP4O12 (LNP) laser combined with an acousto-optic frequency shifter, using an efficient self-mixing modulation arising from the interference between a laser field and a weak field that is fed back from a rough vibrating target. The LVS provides a 50 dB carrier-to-noise ratio for 3 kHz bandwidth, even when monitoring parts that have extremely low reflectivity. Application to laser-Doppler-velocimetry (LDV) capable of discriminating the direction in which different targets are moving has been demonstrated. A remote-sensing experiment by optical fiber access to the target is described briefly.

  8. Development of JSNS target vessel diagnosis system using laser Doppler method

    International Nuclear Information System (INIS)

    When an intense pulsed proton beam with a power of 1 MW is irradiated to a mercury target, a pressure wave caused by the proton beam gives a vibration on the target vessel. Pitting damage also occurs on the target vessel, especially incident beam area, resulting in shortening of a life-time. It is very important to monitor the vibration of the target vessel from the view point of the life-time estimation. We developed the target vessel diagnosis system using laser Doppler method and successfully installed it in an actual pulsed spallation source. The diagnosis system consists of retro-reflecting corner-cube mirror (reflective mirror) on the target, mirror assembly in a reflector plug and laser source-detector. The newly developed reflective mirror, made by nickel, was installed by vacuum silver brazing on the target vessel to detect the target vibration. In order to pass the laser beam to the target vessel, a mirror assembly was installed inside the reflector plug. It is replaceable using a remote handling machine during a maintenance period. Nd-YAG laser beam (wave length: 533 nm) with the power of 50 mW was adopted to detect the target vibration. The first proton beam to the target in the spallation neutron source (JSNS) was provided on 30 May 2008. The first signal related to the target vibration was also detected by using this target vessel diagnosis system.

  9. Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry

    Science.gov (United States)

    Ishida, Hiroki; Yasue, Youichi; Hachiga, Tadashi; Andoh, Tsugunobu; Akiguchi, Shunsuke; Kuraishi, Yasushi; Shimizu, Tadamichi

    2014-07-01

    We developed a micro multipoint laser Doppler velocimeter (?-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the ?-MLDV. Although average velocity is generally estimated from a peak position ( f peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.

  10. Laser-Doppler anemometer for the study of the velocity field for free convection with internal heat sources

    International Nuclear Information System (INIS)

    With the aid of a laser-Doppler anemometer velocity profiles of the tangential component of the mean flow velocity of a fluid at free convection with internal heat sources in a hemispherical vessel were determined. The anemometer used worked according to the two-beam-method, the light of the incident beams being submitted to a given frequency distortion. (orig./TK)

  11. Observation of optical Ramsey interference frings in collinear ion beam-laser beam interaction by Doppler switching

    International Nuclear Information System (INIS)

    We report the observation of optical Ramsey interference fringes in collinear ion beam-laser beam interaction. The analogue of separated fields is created by Doppler switching the ions in two successive zones of the common beam path. New conditions to study quantum interference effects are offered by this method. (orig.)

  12. Ultracold Fermi mixtures and simultaneous sub-Doppler laser cooling of fermionic ^{6}Li and ^{40}K

    OpenAIRE

    Sievers, Franz

    2014-01-01

    Ce travail rend compte de nouvelles techniques développées pour l’étude expérimentale de gaz ultrafroids de lithium et de potassium fermioniques. Les améliorations de notre expérience ^{6}Li-^{40}K y sont décrites et caractérisées. Nous présentons un laser solide de grande finesse capable d’émettre 5W de puissance à 671 nm. Nous utilisons cette source laser dans le contexte d'une nouvelle technique de refroidissement sub-Doppler, reposant sur la transition atomique D1 des atom...

  13. Application of a commercially-manufactured Doppler-shift laser velocimeter to the measurement of basilar-membrane vibration*

    OpenAIRE

    RUGGERO, MARIO A.; RICH, NOLA C.

    1991-01-01

    A commercially-available laser Doppler-shift velocimeter has been coupled to a compound microscope equipped with ultra-long-working-distance objectives for the purpose of measuring basilar membrane vibrations in the chinchilla. The animal preparation is nearly identical to that used in our laboratory for similar measurements using the Mössbauer technique. The vibrometer head is mounted on the third tube of the microscope’s trinocular head and its laser beam is focused on high-refractive-in...

  14. Analytic calculation of absorption spectra for Doppler-broadened alkali-metal atoms at low laser intensity

    International Nuclear Information System (INIS)

    The absorption spectra of Doppler-broadened alkali-metal atoms were calculated analytically at low laser intensity. The results for the D2 and the D1 lines, which are expressed by using the nuclear spin and the energy separation of the atoms, were obtained. These results may be helpful for estimating the absolute values of the absorption and the transmission of a weak laser beam.

  15. Maximum-likelihood estimates of the frequency and other parameters of signals of laser Doppler measuring systems operating in the one-particle-scattering mode

    International Nuclear Information System (INIS)

    Maximum-likelihood equations are presented for estimates of the Doppler frequency (speed) and other unknown parameters of signals of laser Doppler anemometers and lidars operating in the one-particle-scattering mode. Shot noise was assumed to be the main interfering factor of the problem. The error correlation matrix was calculated and the Rao - Cramer bounds were determined. The results are confirmed by the computer simulation of the Doppler signal and the numerical solution of the maximum-likelihood equations for the Doppler frequency. The obtained estimate is unbiased, and its dispersion coincides with the Rao-Cramer bound. (laser applications and other topics in quantum electronics)

  16. Measurement uncertainty and temporal resolution of Doppler global velocimetry using laser frequency modulation

    International Nuclear Information System (INIS)

    A Doppler global velocimetry (DGV) measurement technique with a sinusoidal laser frequency modulation is presented for measuring velocity fields in fluid flows. A cesium absorption cell is used for the conversion of the Doppler shift frequency into a change in light intensity, which can be measured by a fiber coupled avalanche photo diode array. Because of a harmonic analysis of the detector element signals, no errors due to detector offset drifts occur and no reference detector array is necessary for measuring the scattered light power. Hence, large errors such as image misalignment errors and beam split errors are eliminated. Furthermore, the measurement system is also capable of achieving high measurement rates up to the modulation frequency (100 kHz) and thus opens new perspectives to multiple point investigations of instationary flows, e.g., for turbulence analysis. A fundamental measurement uncertainty analysis based on the theory of Cramer and Rao is given and validated by experimental results. The current relation between time resolution and measurement uncertainty, as well as further optimization strategies, are discussed

  17. He-Ne laser effects on blood microcirculation. An in vivo study through laser doppler flowmetry; Efeito do laser de helio neonio sobre a microcirculacao sanguinea durante a reparacao tecidual. Estudo in vivo por meio de fluxometria laser doppler

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, Silvia Cristina

    2002-07-01

    Blood microcirculation performs an important function in tissue repair process, as well as in pain control, allowing for greater oxygenation of the tissues and the accelerated expulsion of metabolic products, that may be contributing to pain. Low Intensity Laser Therapy (LILT) is widely used to promote healing, and there is an assumption that it is mechanism of action may be due to an enhancement of blood supply. The purpose of this study was to evaluate, using laser Doppler flowmetry (LDF), the stated effects caused by radiation emitted by a He-Ne laser ({lambda}=632.8 nm) on blood microcirculation during tissue repair. To this end, 15 male mice were selected and received a liquid nitrogen provoked lesion, above the dorsal region, and blood flow was measured periodically, during 21 days. Due to radiation emission by the LDF equipment, a control group was established to evaluate possible effects caused by this radiation on microcirculation. To evaluate the He-Ne laser effects, a 1.15 J/cm{sup 2} dose was utilized, with an intensity of 6 mW/cm{sup 2}. The results obtained demonstrate flow alterations, provoked by the lesion, and subsequent inflammatory response. There was no statistical difference between the studied groups. As per the analysis of the results there is no immediate effect due the radiation emitted by a He Ne laser on microcirculation, although a percentage increase was observed in day 7 on medium blood flow rate in irradiated specimens. New studies are necessary to validate the use of this wavelength, in order to promote beneficial alterations in blood supply in radiated areas. (author)

  18. A multi-point laser Doppler vibrometer with fiber-based configuration.

    Science.gov (United States)

    Yang, C; Guo, M; Liu, H; Yan, K; Xu, Y J; Miao, H; Fu, Y

    2013-12-01

    Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas. PMID:24387407

  19. Application and assessment of laser Doppler velocimetry for underwater acoustic measurements

    Science.gov (United States)

    Harland, A. R.; Petzing, J. N.; Tyrer, J. R.; Bickley, C. J.; Robinson, S. P.; Preston, R. C.

    2003-08-01

    The majority of traditional methods for making underwater acoustic pressure measurements involve placing all or part of a measurement transducer in the acoustic field. A variety of optical metrology techniques have been developed in an attempt to reduce or remove any perturbing effects. An example of this is the use of laser interferometry which has been developed as the primary method of calibrating hydrophones in the frequency range 500 kHz- 20 MHz at the National Physical Laboratory (NPL). This technique involves suspending a thin Mylar pellicle in the acoustic field and recording the displacement of the pellicle surface using a Michelson Interferometer. This study details a comparison of a Laser Doppler Velocimeter (LDV) with the NPL Laser Interferometer, which gives a good correlation where agreement is within approximately 4% and 7% for two different power levels from a 500 kHz plane piston transducer and within 2.5% and 1% for the same power levels from a 1 MHz plane piston transducer. A novel, non-perturbing method of recording temporally resolved acoustic pressure distributions in water using an LDV is also described. The technique is shown to benefit from the consistent frequency response of the LDV detection system, such that the measured output resembles the drive voltage input to the transducer more closely than a similar hydrophone measurement. For the experimental arrangement described, the LDV system is shown to be sensitive to minimum pressure amplitudes of nominally 18.9 mPa/? Hz.

  20. A multi-point laser Doppler vibrometer with fiber-based configuration

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C. [Temasek Laboratories and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China); Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621900 (China); Guo, M.; Liu, H.; Yan, K.; Xu, Y. J.; Fu, Y., E-mail: fuyuoptics@gmail.com [Temasek Laboratories and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); Miao, H. [Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China)

    2013-12-15

    Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas.

  1. A multi-point laser Doppler vibrometer with fiber-based configuration

    International Nuclear Information System (INIS)

    Laser Doppler vibrometer (LDV) is a non-contact optical interferometric system to measure vibrations of structures and machines with a high precision. Normal LDV can only offer a single-point measurement. Scanning LDV is usually impractical to do measurement on transient events. In this paper, a fiber-based self-synchronized multi-point LDV is proposed. The multiple laser beams with different frequency shifts are generated from one laser source. The beams are projected onto a vibrating object, reflected and interfered with a common reference beam. The signal including vibration information of multiple spatial points is captured by one single-pixel photodetector. The optical system is mainly integrated by fiber components for flexibility in measurement. Two experiments are conducted to measure a steady-state simple harmonic vibration of a cantilever beam and a transient vibration of a beam clamped at both ends. In the first measurement, a numerical interpolation is applied to reconstruct the mode shape with increased number of data points. The vibration mode obtained is compared with that from FEM simulation. In transient vibration measurement, the first five resonant frequencies are obtained. The results show the new-reported fiber-based multipoint LDV can offer a vibration measurement on various spatial points simultaneously. With the flexibility of fiber configuration, it becomes more practical for dynamic structural evaluation in industrial areas

  2. Laser Doppler anemometry measurements in a circulating fluidized bed of metal particles

    DEFF Research Database (Denmark)

    Ibsen, Claus Hübbe; Solberg, Tron

    2002-01-01

    Laser Doppler Anemometry (LDA) measurements were performed in a 1/9 scale model of a 12 MW circulating fluidized bed (CFB) boiler. The model was operated according to scaling laws. The 2D-LDA system used was positioned in two different ways to obtain the three velocity components u, v and w of the solid phase from which the particle kinetic stresses were determined. The measured velocity profiles are in agreement with previous data from the full-scale boiler, i.e. showing a flat profile over the core region of the riser with a pronounced wall layer. The particle kinetic stresses are found to be anisotropic and strongly influenced by large scale effects originating from the bottom-bed bubbles.

  3. On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement.

    Science.gov (United States)

    Li, Yanlu; Segers, Patrick; Dirckx, Joris; Baets, Roel

    2013-07-01

    Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-insulator substrate. In this system, a chip with two homodyne LDVs is utilized to simultaneously measure the pulse wave at two different locations along the CCA. Measurement results show that the dual-LDV chip can successfully conduct the PWV measurement. PMID:23847745

  4. EURISOL-DS Multi-MW Target: Cavitations detection by the a Laser Doppler Vibrometer

    CERN Document Server

    Cyril Kharoua, Yacine Kadi, Jacques Lettry, Laure Blumenfeld, Karel Samec (CERN)Knud Thomsen, Sergej Dementevjs, Rade Milenkovich (PSI)Anatoli Zik, Erik Platacis (IPUL)

    This technical note summarises the innovative measurement devices used within Task #2 of the European Isotope Separation On-Line Radioactive Ion Beam Facility Design Study (EURISOL-DS) to detect the occurrence of cavitation in liquid metal flowing inside the CGS target mock-up.During the METEX hydraulic experiment carried out at IPUL (Institute of Physics of the University of Latvia), a Laser Doppler Vibrometer was used to characterize the wall vibrations of the beam window at different flow regimes. A series of tests proved the high sensitivity of the LDV to detect the occurrence of cavitation in the liquid metal flowing inside the target. In this context, a dedicated test procedure was developed to establish the validity of using LDV for detecting the onset of cavitation.

  5. Conformal scanning laser Doppler vibrometer measurement of tenor steelpan response to impulse excitation.

    Science.gov (United States)

    Ryan, Teresa; O'Malley, Patrick; Glean, Aldo; Vignola, Joseph; Judge, John

    2012-11-01

    A conformal scanning laser Doppler vibrometer system is used in conjunction with a mechanical pannist to measure the surface normal vibration of the entire playing surface of a C-lead tenor steelpan. The mechanical pannist is a device designed to deliver controlled, repeatable strikes that mimic a mallet during authentic use. A description of the measurement system is followed by select examples of behavior common to the results from three different excitation notes. A summary of observed response shapes and associated frequencies demonstrates the concerted placement of note overtones by the craftsmen who manufacture and tune the instruments. The measurements provide a rich mechanical snapshot of the complex motion that generates the distinctive sound of a steelpan. PMID:23145629

  6. Effect of timolol on sub-foveal choroidal blood flow using laser Doppler flowmetry

    Science.gov (United States)

    Palanisamy, Nithiyanantham; Rovati, Luigi; Cellini, Mauro; Gizzi, Corrado; Strobbe, Ernesto; Campos, Emilio; Riva, Charles E.

    2011-03-01

    Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours. Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated eyes were observed.

  7. Innovative technique for field calibration and inspection of large district heating meters. Laser doppler velocimetry (LDV)

    Energy Technology Data Exchange (ETDEWEB)

    Adams, M.; Frederiksen, J.; Drysdale, A. [Danish Technological Inst., Aarhus (Denmark); Hessel, C.E. [Aalborg Municipal Works (Denmark)

    2002-10-01

    During the last three years, the Danish Technological Institute has managed and co-ordinated a recently completed R and D project aimed at developing an innovative method for field calibration and inspection of large district heating meters. The method is based on Laser Doppler Velocimetry (LDV) and the project has been carried out in close co-operation with partners from Danish district heating plants and supply companies, flow meter manufacturers, a leading manufacturer of LDV equipment and the Technical University of Denmark. The resulting measurement method has been developed with special reference to large (>200 mm diameter) district heating meters used for surveillance, control and billing, but the technique can also be used advantageously for flow measurements in almost any closed pipe system transporting transparent gases and liquids. Results of the project have been very satisfactory and the Danish Technological Institute expects to be able to offer fully accredited in-situ LDV measurements in the near future. (orig.)

  8. Laser Doppler velocimeter for vehicle application with improved signal-to-noise ratio

    Science.gov (United States)

    Nie, Xiaoming; Zhou, Jian; Long, Xingwu

    2014-09-01

    Laser Doppler velocimeter (LDV) with improved signal-to-noise ratio (SNR) is presented to measure the vehicle velocity. A novel optical structure named split-reuse type configuration is developed to improve the SNR of LDV. Reference measurements were provided by measuring the outer surface of a precision single-axis turntable. Under these conditions, the measurement uncertainty of the instrument is better than 0.56 % with 95 % confidence interval. The split-reuse type LDV has been tested with an automobile on the open road, and the measurement results are comparing with the results of a precision spatial filter velocimeter, which verify the feasibility of split-reuse type LDV to measure the self-velocity of vehicle.

  9. Scanning laser Doppler velocimeter system simulation for sensing aircraft wake vortices

    Science.gov (United States)

    Thomson, J. A. L.; Meng, J. C. S.

    1976-01-01

    A model that simulates the interaction of a laser-Doppler velocimeter with an aircraft wake flowfield is described. A hydrodynamic model is developed which represents the trailing vortex sheet and wind shear as discrete free vortices distributed over a two-dimensional grid. A sensor model is formulated for scanning both in range and in angle to produce a fan beam configuration without frequency translation. Output of this model is a frequency spectrum vs both range and angle. Once the spectrum is evaluated, simulations of the data analysis procedure are carried out. Patterns of various features of the signature are presented in range-elevation angle plots. The problem of locating the vortex centers is discussed as a pattern recognition problem and as a point target problem.

  10. Laser Doppler vibrometer measurement on spiders in moving-coil loudspeakers

    Science.gov (United States)

    Kong, Xiaopeng; Zeng, Xinwu; Tian, Zhangfu

    2014-12-01

    The spider is the dominate stiffness to suspend the cone for a moving-coil loudspeaker unit, and is most commonly a concentrically corrugated fabric disk. A subwoofer closed box is designed to excite the tested spiders pneumatically, and the Laser Doppler Vibrometer (LDV) is used to measure the velocity of the moving spiders. The effective stiffness, loss factor and some viscoelastic behaviors such as level dependent stiffness have been investigated. The results find that, this pneumatic non-contact dynamic technique successfully measured the viscoelastic behaviors of spiders from extremely low frequency 5 Hz to 200 Hz, and the effective stiffness of spiders is dependent on the input voltage level, which is higher level with lower stiffness.

  11. Laser Doppler vibrometry measurements of the carotid pulse: biometrics using hidden Markov models

    Science.gov (United States)

    Kaplan, Alan D.; O'Sullivan, Joseph A.; Sirevaag, Erik J.; Rohrbaugh, John W.

    2009-05-01

    Small movements of the skin overlying the carotid artery, arising from pressure pulse changes in the carotid during the cardiac cycle, can be detected using the method of Laser Doppler Vibrometry (LDV). Based on the premise that there is a high degree of individuality in cardiovascular function, the pulse-related movements were modeled for biometric use. Short time variations in the signal due to physiological factors are described and these variations are shown to be informative for identity verification and recognition. Hidden Markov models (HMMs) are used to exploit the dependence between the pulse signals over successive cardiac cycles. The resulting biometric classification performance confirms that the LDV signal contains information that is unique to the individual.

  12. Hidden state dynamics in laser Doppler vibrometery measurements of the carotid pulse under resting conditions.

    Science.gov (United States)

    Kaplan, Alan D; O'Sullivan, Joseph A; Sirevaag, Erik J; Kristjansson, Sean D; Lai, Po-Hsiang; Rohrbaugh, John W

    2010-01-01

    A laser Doppler vibrometer (LDV) is used to sense movements of the skin overlying the carotid artery. Fluctuations in carotid artery diameter due to variations in the underlying blood pressure are sensed at the surface of the skin. Portions of the LDV signal corresponding to single heartbeats, called the LDV pulses, are extracted. This paper introduces the use of hidden Markov models (HMMs) to model the dynamics of the LDV pulse from beat to beat based on pulse morphology, which under resting conditions are primarily due to breathing effects. LDV pulses are classified according to state, by computing the optimal state path through the data using trained HMMs. HMM state dynamics are compared to simultaneous recordings of strain gauges placed on the abdomen. The work presented here provides a robust statistical approach to modeling the dependence of the LDV pulse on latent states. PMID:21096057

  13. Barriers to the management of Diabetes Mellitus – is there a future role for Laser Doppler Flowmetry?

    Directory of Open Access Journals (Sweden)

    Minnie Au

    2012-12-01

    Full Text Available Diabetes Mellitus (DM is a chronic disease that carries a significant disease burden in Australia and worldwide. The aim of this paper is to identify current barriers in the management of diabetes, ascertain whether there is a benefit from early detection and determine whether LDF has the potential to reduce the disease burden of DM by reviewing the literature relating to its current uses and development. In this literature review search terms included; laser Doppler flowmetry, diabetes mellitus, barriers to management, uses, future, applications, vasomotion, subcutaneous, cost. Databases used included Google Scholar, Scopus, Science Direct and Medline. Publications from the Australian government and textbooks were also utilised. Articles reviewed had access to the full text and were in English.

  14. Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas

    International Nuclear Information System (INIS)

    We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.

  15. Laser Doppler Velocimeter measurements in a 3-D impinging twin-jet fountain flow

    Science.gov (United States)

    Saripalli, K. R.

    1987-01-01

    Mean velocity and turbulence measurements were conducted on the three dimensional fountain flow field generated by the impingement of two axisymmetric jets on a ground plane with application to vertical takeoff and landing (VTOL) aircraft. The basic instantaneous velocity data were obtained using a two component laser Doppler velocimeter in a plane connecting the nozzle centerlines at different heights above the ground emphasizing the jet impingement region and the fountain upwash region formed by the collision of the wall jets. The distribution of mean velocity components and turbulence quantities, including the turbulence intensity and the Reynolds shear stress, were derived from the basic velocity data. Detailed studies of the characteristics of the fountain revealed self-similarity in the mean velocity and turbulence profiles across the fountain. The spread and mean velocity decay characteristics of the fountain were established. Turbulence intensities of the order of 50% were observed in the fountain.

  16. Boundary layer measurements on an airfoil in cascade using laser Doppler anemometry

    Science.gov (United States)

    Williams, F. W.

    1986-01-01

    Laser Doppler anemometry (LDA) was used to obtain detailed boundary layer data at 89.3 percent chord on the pressure surface of a double circular arc compressor blade in cascade. The measurements were taken at a chord Reynolds number of 5.0 x 10 to the 5th and a cascade angle of 53 degrees. The mean velocity, local turbulence intensity, skewness, and kurtosis were determined from the measured velocity probability distributions. The mean velocity profile and the local turbulence intensity profile had classical shapes. Also, the skewness and kurtosis had commonly observed shapes through out the boundary layer, reaching maximum values for Y/delta between 0.5 and 1.1 and Gaussian values for Y/delta greater than 1.1. A comparison was made between data taken with and without the Bragg cell and no significant differences were found.

  17. Measurement of a counter rotation propeller flowfield using a Laser Doppler Velocimeter

    Science.gov (United States)

    Harrison, G. L.; Sullivan, J. P.

    1987-01-01

    This paper is a summary of the results of the experimental investigation of the flow field about a counter-rotating propeller (CRP) system using a Laser Doppler Velocimeter (LDV). The number of configurations available for the CRP system is limitless, thus only a small portion of the number of possible cases were examined. Measurements were made upstream, in between and downstream of the propeller system. The abundance of data readily available from the LDV system clearly identifies the tip vortices and wake regions. The recovery by the downstream propeller of the swirl velocity imparted to the flow by the upstream propeller is very evident. The coefficients of thrust and power were determined using momentum and energy analysis of the data and compared to theory.

  18. Automatic measurement of field-dependent elastic modulus and damping by laser Doppler vibrometry

    International Nuclear Information System (INIS)

    A method for characterizing the magnetoelastic dependence of both Young's modulus and damping on the magnetic field is presented. It is based on laser Doppler vibrometry and free longitudinal vibration in soft ferromagnetic rods and wires, and offers a broad range of improved features including accuracy, lack of interaction with the sample, speed of measurement, full automation, high resolution and the possibility of stress-dependence studies. All these allow samples to be perfectly characterized in the full magnetic field range, estimating the behaviour of the specimen as different magnetization curves are followed and discovering critical points that had been overlooked in previous works. As an example, the magnetoelastic characterization of nickel rods is described, and excellent results are obtained which are consistent with the hysteresis loop of nickel and the theory of magnetic domains in ferromagnetic materials

  19. A microcomputer based frequency-domain processor for laser Doppler anemometry

    Science.gov (United States)

    Horne, W. Clifton; Adair, Desmond

    1988-01-01

    A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors.

  20. A laser Doppler velocimeter approach for near-wall three-dimensional turbulence measurements

    Science.gov (United States)

    Johnson, D. A.; Brown, J. D.

    1990-01-01

    A near-wall laser Doppler velocimeter approach is described that relies on a beam-turning probe which makes possible the direct measurement of the crossflow velocity at a grazing incident and the placement of optical components close to the flow region of interest regardless of test facility size. Other important elements of the approach are the use of digital frequency processing, an optically smooth measurement surface, and observation of the sensing volume at 90 degrees. The combination was found to dramatically reduce noise-in-signal effects caused by surface light scattering. Turbulent boundary-layer data to within 20 microns (y(sup+) approximately equal to 1) of the surface are presented which illustrate the potential of the approach.

  1. Doppler-free laser spectroscopy of buffer-gas-cooled molecular radicals

    International Nuclear Information System (INIS)

    We demonstrate Doppler-free saturated absorption spectroscopy of cold molecular radicals formed by laser ablation inside a cryogenic buffer gas cell. By lowering the temperature, congested regions of the spectrum can be simplified, and by using different temperatures for different regions of the spectrum a wide range of rotational states can be studied optimally. We use the technique to study the optical spectrum of YbF radicals with a resolution of 30 MHz, measuring the magnetic hyperfine parameters of the electronic ground state. The method is suitable for high-resolution spectroscopy of a great variety of molecules at controlled temperature and pressure, and is particularly well suited to those that are difficult to produce in the gas phase.

  2. Accurate and precise calibration of AFM cantilever spring constants using laser Doppler vibrometry

    International Nuclear Information System (INIS)

    Accurate cantilever spring constants are important in atomic force microscopy both in control of sensitive imaging and to provide correct nanomechanical property measurements. Conventional atomic force microscope (AFM) spring constant calibration techniques are usually performed in an AFM. They rely on significant handling and often require touching the cantilever probe tip to a surface to calibrate the optical lever sensitivity of the configuration. This can damage the tip. The thermal calibration technique developed for laser Doppler vibrometry (LDV) can be used to calibrate cantilevers without handling or touching the tip to a surface. Both flexural and torsional spring constants can be measured. Using both Euler–Bernoulli modeling and an SI traceable electrostatic force balance technique as a comparison we demonstrate that the LDV thermal technique is capable of providing rapid calibrations with a combination of ease, accuracy and precision beyond anything previously available. (paper)

  3. Joint time-frequency analysis of tracking laser Doppler vibrometry data on a rolling tire

    Energy Technology Data Exchange (ETDEWEB)

    Castellini, P. [Ancona Univ. (Italy). Dipt. di Meccanica; Montanini, R. [Messina Univ. (Italy). DCIIM

    2001-07-01

    The vibration analysis of a rolling tire is a very interesting but difficult task. To obtain realistic results on the dynamic characteristics of the tire, laboratory tests should be performed under simulated operative conditions, that is, when the tire is rolling. This task is not easy to achieve with traditional measurement techniques. In this paper tracking laser Doppler vibrometer (TLDV) has been applied for the measurement of time histories of the vibration velocity of a tire. A Lagrangian approach was adopted: data were acquired with the target in continuously changing conditions. In fact, the measurement point rotates with the tire and therefore it enters and exits from the contact area. In order to analyse vibration data, that are in an unsteady condition, a joint time-frequency analysis has been performed. Different algorithms have been compared and some preliminary results are shown in this work. (orig.)

  4. Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry

    CERN Document Server

    Crua, Cyril

    2015-01-01

    In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a three dimensional laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working fluid, or limiting the fuel injection pressure. The vibrometer, which uses the Doppler effect to measure the velocity of a vibrating object, was used to scan injector nozzle tips during the injection event. The data were processed using a discrete Fourier transform to provide time-resolved spectra for valve-closed-orifice, minisac and microsac nozzle geometries, and injection pressures ranging from 60 to 160MPa, hence offering unprecedented insight into cyclic cavitation and internal mechanical dynamic processes. A peak was consistently f...

  5. Elasticity Evaluation of Regenerating Cartilage Sample Based on Laser Doppler Measurement of Ultrasonic Particle Velocity

    Science.gov (United States)

    Nitta, Naotaka; Misawa, Masaki; Homma, Kazuhiro; Shiina, Tsuyoshi

    2012-07-01

    It is important for regenerative medicine to evaluate the maturity of regenerating tissue. In the maturity evaluation of regenerating cartilage, it is useful to measure the temporal change of elasticity because the maturity of regenerating tissue is closely related to its elasticity. In this study, an elasticity evaluation method for the extracted regenerating cartilage sample, which is based on the laser Doppler measurement of ultrasonic particle velocity, was experimentally investigated using agar-based phantoms with different elastic moduli and the regenerating cartilage samples extracted from beagles in animal experiments. In addition, the experimentally-obtained elasticity was compared with the result of a static compression test. These results verified the feasibility of the proposed method in the elasticity evaluation of regenerating cartilage samples.

  6. Measurement of fluid velocity development in laminar pipe flow using laser Doppler velocimetry

    International Nuclear Information System (INIS)

    In this paper we present a non-intrusive experimental approach for obtaining velocity gradient profiles in a transparent smooth pipe under laminar flow conditions (Re = 925) using a laser Doppler velocimeter (LDV). Measurements were taken within the entrance region of the pipe at l = 300 mm and l = 600 mm from the pipe inlet, in addition to measurements of the fully developed flow at l = 1800 mm. The obtained results show how the velocity profile from upstream of the pipe develops into a classical laminar profile downstream, which matches the theoretical profile well. Additionally, a brief summary of historical information about the development of flow measurement techniques, in particular LDV, is provided. (paper)

  7. Flow characteristics in spacer grids measured by rod-embedded fiber laser doppler velocimetry

    International Nuclear Information System (INIS)

    Precise measurement of velocity in fuel bundles is required to improve the thermal-hydraulic properties of Pressurized Water Reactor (PWR) spacer grids. To better understand the cross-flow characteristics in rod bundles for developing spacer grids, we used the rod-embedded fiber laser Doppler velocimetry (rod LDV) to measure the flow velocities inside the spacer grid flow channels. As the result of measurement, we found that the flow distribution inside the spacer grid depends on the local flow resistance of the grid straps and is clearly affected by the presence of a mixing vane. We also clarified the relationship between cross-flow velocity in the fuel bundle downstream of the spacer grid and the axial flow inside the spacer grid. (author)

  8. Simulating translation-induced laser speckle dynamics in photon Doppler velocimetry.

    Science.gov (United States)

    Warren, Will J; Moro, Erik A; Briggs, Matthew E; Flynn, Eric B

    2014-07-20

    Historically, single-beam optical velocimetry has been limited to measuring only the component of velocity along the beam. However, theoretical work and recent experimental results have shown that laser speckle dynamics may be exploited to measure lateral motion, thereby gaining information about surface dynamics across an additional degree of freedom. In the use of photon Doppler velocimetry (PDV), this new information is considered "free" in that it is already contained within the PDV signal, needing only to be extracted and interpreted correctly. In this manuscript, we relate speckle dynamics to the lateral motion of a planar scattering surface in the PDV coordinate system via the space-time correlation function of the diffracted electric field. Next, we relate the characteristic time scale of speckle intensity fluctuations in the PDV signal to the rate of lateral surface translation and to parameters characterizing the optical probe. Analytical results are compared with a numerical simulation and found to be in close agreement. PMID:25090201

  9. Generation and fluid dynamics of scattering aerosols in laser Doppler velocimetry

    Science.gov (United States)

    Mazumder, M. K.; Hoyle, B. D.; Kirsch, K. J.

    1974-01-01

    An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited flow field where the particle Reynolds numbers were controlled to simulate the corresponding values of fluid turbulence. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. The present study indicates that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

  10. An experimental study of a three-dimensional thrust augmenting ejector using laser Doppler velocimetry

    Science.gov (United States)

    Storms, Bruce Lowell

    1989-01-01

    Flow field measurements were obtained in a three-dimensional thrust augmenting ejector using laser Doppler velocimetry and hot wire anemometry. The primary nozzle, segmented into twelve slots of aspect ratio 3.0, was tested at a pressure ratio of 1.15. Results are presented on the mean velocity, turbulence intensity, and Reynolds stress progressions in the mixing chamber of the constant area ejector. The segmented nozzle was found to produce streamwise vortices that may increase the mixing efficiency of the ejector flow field. Compared to free jet results, the jet development is reduced by the presence of the ejector walls. The resulting thrust augmentation ratio of this ejector was also calculated to be 1.34.

  11. Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets

    Science.gov (United States)

    Cahoy, Kerri; Fischer, Debra; Spronck, Julien; DeMille, David

    2010-07-01

    Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the "noise" from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.

  12. Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

    Science.gov (United States)

    Campo, Adriaan; Dirckx, Joris

    2014-05-01

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation.

  13. Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

    Energy Technology Data Exchange (ETDEWEB)

    Campo, Adriaan; Dirckx, Joris [University of Antwerp, Laboratory of Biomedical Physics, Groenenborgerlaan 171 2020 Antwerp (Belgium)

    2014-05-27

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation.

  14. Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

    International Nuclear Information System (INIS)

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between waveforms. Immediately after LDV measurements, PWV was measured with US. Additionally, carotid-femoral PWV was measured. As a validation, PWV results of the different techniques were compared with each other, and with medical background of the test subjects. Since data acquisition is still ongoing, data from only 20 patients will be discussed. No trends between measurement methods for PWV are apparent. However, a positive trend was detected between PWV as measured with LDV and blood pressure. More data, including additional experiments will be needed to verify this observation

  15. Cost-effectiveness of laser Doppler imaging in burn care in the Netherlands

    Directory of Open Access Journals (Sweden)

    Hop M Jenda

    2013-02-01

    Full Text Available Abstract Background Early accurate assessment of burn depth is important to determine the optimal treatment of burns. The method most used to determine burn depth is clinical assessment, which is the least expensive, but not the most accurate. Laser Doppler imaging (LDI is a technique with which a more accurate (>95% estimate of burn depth can be made by measuring the dermal perfusion. The actual effect on therapeutic decisions, clinical outcomes and the costs of the introduction of this device, however, are unknown. Before we decide to implement LDI in Dutch burn care, a study on the effectiveness and cost-effectiveness of LDI is necessary. Methods/design A multicenter randomised controlled trial will be conducted in the Dutch burn centres: Beverwijk, Groningen and Rotterdam. All patients treated as outpatient or admitted to a burn centre within 5 days post burn, with burns of indeterminate depth (burns not obviously superficial or full thickness and a total body surface area burned of ? 20% are eligible. A total of 200 patients will be included. Burn depth will be diagnosed by both clinical assessment and laser Doppler imaging between 2–5 days post burn in all patients. Subsequently, patients are randomly divided in two groups: ‘new diagnostic strategy’ versus ‘current diagnostic strategy’. The results of the LDI-scan will only be provided to the treating clinician in the ‘new diagnostic strategy’ group. The main endpoint is the effect of LDI on wound healing time. In addition we measure: a the effect of LDI on other patient outcomes (quality of life, scar quality, b the effect of LDI on diagnostic and therapeutic decisions, and c the effect of LDI on total (medical and non-medical costs and cost-effectiveness. Discussion This trial will contribute to our current knowledge on the use of LDI in burn care and will provide evidence on its cost-effectiveness. Trial registration NCT01489540

  16. Adaptation of laser-Doppler flowmetry to measure cerebral blood flow in the fetal sheep.

    Science.gov (United States)

    Lan, J; Hunter, C J; Murata, T; Power, G G

    2000-09-01

    The purpose of this study was to devise a means to use laser-Doppler flowmetry to measure cerebral perfusion before birth. The method has not been used previously, largely because of intrauterine movement artifacts. To minimize movement artifacts, a probe holder was molded from epoxy putty to the contour of the fetal skull. A curved 18-gauge needle was embedded in the holder. At surgery, the holder, probe, and skull were fixed together with tissue glue. Residual signals were recorded after fetal death and after maternal death 1 h later. These averaged <5% of baseline flow signals, indicating minimal movement artifact. To test the usefulness of the method, cerebral flow responses were measured during moderate fetal hypoxia induced by giving the ewes approximately 10% oxygen in nitrogen to breathe. As fetal arterial PO(2) decreased from 21.1 +/- 0.5 to 10.7 +/- 0.4 Torr during a 30-min period, cerebral perfusion increased progressively to 56 +/- 8% above baseline. Perfusion then returned to baseline levels during a 30-min recovery period. These responses are quantitatively similar to those spot observations that have been recorded earlier using labeled microspheres. We conclude that cerebral perfusion can be successfully measured by using laser-Doppler flowmetry with the unanesthetized, chronically prepared fetal sheep as an experimental model. With this method, relative changes of perfusion from a small volume of the ovine fetal brain can be measured on a continuous basis, and movement artifacts can be reduced to 5% of measured flow values. PMID:10956352

  17. Development of the immersed sodium flowmeter

    International Nuclear Information System (INIS)

    An immersed sodium flowmeter of the range 3 m3/h is developed. It is a flowmeter of entire-sealed construction, it can be operated in sodium. Its construction, the theoretical calculation of the calibration characteristic and the pressure loss, the test facility and the calibration test are presented in detail. It analytical expression of the calibration characteristic in the temperature limit 200?600 degree C and the error analysis are given. The basic error of this immersed sodium flowmeter is below +-2.3% of the measuring range. The immersed sodium flowmeter can be used to resolve the sodium flowrate measuring problems of the in-reactor component of LMFBR, for example, the flowrate measuring of the in-reactor sodium purification loop, the flowrate measuring of the immersed sodium pump and the flowrate measuring of the in-reactor test component

  18. Efficient sub-Doppler transverse laser cooling of an indium atomic beam

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Ihn

    2009-07-23

    Laser cooled atomic gases and atomic beams are widely studied samples in experimental research in atomic and optical physics. For the application of ultra cold gases as model systems for e.g. quantum many particle systems, the atomic species is not very important. Thus this field is dominated by alkaline, earthalkaline elements which are easily accessible with conventional laser sources and have convenient closed cooling transition. On the other hand, laser cooled atoms may also be interesting for technological applications, for instance for the creation of novel materials by atomic nanofabrication (ANF). There it will be important to use technologically relevant materials. As an example, using group III atoms of the periodical table in ANF may open a route to generate fully 3D structured composite materials. The minimal requirement in such an ANF experiment is the collimation of an atomic beam which is accessible by one dimensional laser cooling. In this dissertation, I describe transverse laser cooling of an Indium atomic beam. For efficient laser cooling on a cycling transition, I have built a tunable, continuous-wave coherent ultraviolet source at 326 nm based on frequency tripling. For this purpose, two independent high power Yb-doped fiber amplifiers for the generation of the fundamental radiation at {lambda}{sub {omega}} = 977 nm have been constructed. I have observed sub-Doppler transverse laser cooling of an Indium atomic beam on a cycling transition of In by introducing a polarization gradient in the linear-perpendicular-linear configuration. The transverse velocity spread of a laser-cooled In atomic beam at full width at half maximum was achieved to be 13.5{+-}3.8 cm/s yielding a full divergence of only 0.48 {+-} 0.13 mrad. In addition, nonlinear spectroscopy of a 3-level, {lambda}-type level system driven by a pump and a probe beam has been investigated in order to understand the absorption line shapes used as a frequency reference in a previous two-color spectroscopy experiment. For the analysis of this atomic system, I have applied a density matrix theory providing an excellent basis for understanding the observed line shapes. (orig.)

  19. Efficient sub-Doppler transverse laser cooling of an indium atomic beam

    International Nuclear Information System (INIS)

    Laser cooled atomic gases and atomic beams are widely studied samples in experimental research in atomic and optical physics. For the application of ultra cold gases as model systems for e.g. quantum many particle systems, the atomic species is not very important. Thus this field is dominated by alkaline, earthalkaline elements which are easily accessible with conventional laser sources and have convenient closed cooling transition. On the other hand, laser cooled atoms may also be interesting for technological applications, for instance for the creation of novel materials by atomic nanofabrication (ANF). There it will be important to use technologically relevant materials. As an example, using group III atoms of the periodical table in ANF may open a route to generate fully 3D structured composite materials. The minimal requirement in such an ANF experiment is the collimation of an atomic beam which is accessible by one dimensional laser cooling. In this dissertation, I describe transverse laser cooling of an Indium atomic beam. For efficient laser cooling on a cycling transition, I have built a tunable, continuous-wave coherent ultraviolet source at 326 nm based on frequency tripling. For this purpose, two independent high power Yb-doped fiber amplifiers for the generation of the fundamental radiation at ?? = 977 nm have been constructed. I have observed sub-Doppler transverse laser cooling of an Indium atomic beam on a cycling transition of In by introducing a polarization gradient in the linear-perpendicular-linear configuration. The transverse velocity spread of a laser-cooled In atomic beam at full width at half maximum was achieved to be 13.5±3.8 cm/s yielding a full divergence of only 0.48 ± 0.13 mrad. In addition, nonlinear spectroscopy of a 3-level, ?-type level system driven by a pump and a probe beam has been investigated in order to understand the absorption line shapes used as a frequency reference in a previous two-color spectroscopy experiment. For the analysis of this atomic system, I have applied a density matrix theory providing an excellent basis for understanding the observed line shapes. (orig.)

  20. Improvements in or relating to vortex-shedding fluid flowmeters

    International Nuclear Information System (INIS)

    A fluid flowmeter has a conduit and an obstacle in the fluid flow which extends to outside the conduit. Successive vortices break away from the obstacle transmitting movement to the obstacle outside the conduit. This movement is sensed e.g. by a laser interferometer or a piezoelectric sensor which may be outside a containment wall. The obstacle may be symmetrical in a cross-section taken parallel to the flow and eg of rectangular or circular shape or it may be of semi-circular cross-section. (author)

  1. Sub-Doppler diode laser frequency stabilization with the DAVLL scheme on the D1 line of a 87Rb vapor-cell

    OpenAIRE

    Giannini, R.; Breschi, E.; Affolderbach, C.; Bison, G.; Mileti, G.; Herzig, Hans-Peter; Weis, A.(Physics Department, University of Fribourg, Fribourg, CH-1700, Switzerland)

    2007-01-01

    We established an experimental set-up that allows laser stabilization using the Doppler1 and sub-Doppler2,3 Dichroic Atomic Vapor Laser Locking (DAVLL) and the Saturated Absorption (SA) scheme. In this report we present comparative studies between Doppler and sub-Doppler DAVLL using heterodyne frequency stability measurements with an independently SA stabilized laser. Some major sources of frequency instability are discussed together with ways to improve the stability. Special focus is laid o...

  2. Design of a Geothermal Downhole Magnetic Flowmeter

    Energy Technology Data Exchange (ETDEWEB)

    Glowka, Dave A.; Normann, Randy A.

    2015-06-15

    This paper covers the development of a 300°C geothermal solid-state magnetic flowmeter (or magmeter) to support in situ monitoring of future EGS (enhanced geothermal system) production wells. Existing flowmeters are simple mechanical spinner sensors. These mechanical sensors fail within as little as 10 hrs, while a solid-state magmeter has the potential for months/years of operation. The design and testing of a magnetic flow sensor for use with existing high-temperature electronics is presented.

  3. Application possibilities of laser Doppler anemometry in the investigation of the transonic interaction between shock wave and boundary layer

    Science.gov (United States)

    Schaefer, H. J.; Horny, G.; Pfeifer, H. J.; Stanewsky, E.

    1983-12-01

    A laser Doppler anemometer was used in a transonic wind tunnel to investigate the flows about wing profiles containing shock waves and separated zones. Flow states characterized by the absence or the presence of a shock-induced separation were created. The results of the laser anemometry are presented in the form of two-dimensional Mach number distributions. The good agreement with analogous results obtained by classical probe measurements and model calculations indicate that the laser anemometer can be successfully utilized for the quantitative analysis of shock-boundary layer interferences about transonic wing profiles.

  4. Feasibility of Laser Doppler Vibrometry as potential diagnostic tool for patients with abdominal aortic aneurysms.

    Science.gov (United States)

    Schuurman, T; Rixen, D J; Swenne, C A; Hinnen, J-W

    2013-04-01

    The application of laser measurements in medical applications makes it possible to measure even very small vibrations without contacting the skin surface. In the present work we investigate the use of a scanning vibrometer to measure the mechanical wave of the abdominal wall caused by the heart beat and blood pressure pulse. A Laser Doppler Vibrometer, triggered by cardiac signals, is used to scan points on a grid positioned on the abdomen of human subjects. The proposed procedure is intended for detecting anomalies in the abdominal cavity such as aortic aneurysms. Here, we outline the technical setup used in our preliminary in vivo experiments and present some preliminary results. This feasibility study shows that the proposed measurement procedure allows for measuring the skin motion, that the skin motion measured is related to the heart activity, and that there are indication that the presence of an abdominal aortic aneurysm significantly modifies the relation between blood pressure pulsations and skin motion on the abdomen. PMID:23466177

  5. Broadband measurement of translational and angular vibrations using a single continuously scanning laser Doppler vibrometer.

    Science.gov (United States)

    Salman, Muhammad; Sabra, Karim G

    2012-09-01

    A continuous scanning laser Doppler velocimetry (CSLDV) technique is used to measure the low frequency broadband vibrations associated with human skeletal muscle vibrations (typically f laser beam over distances that are short compared to the characteristic wavelengths of the vibrations. The high frequency scan (compared to the vibration frequency) enables the detection of broadband translational and angular velocities at a single point using amplitude demodulation of the CSDLV signal. For instance, linear scans allow measurement of the normal surface velocity and one component of angular velocity vector, while circular scans allow measurement of an additional angular velocity component. This CSLDV technique is first validated here using gel samples mimicking soft tissues and then applied to measure multiple degrees of freedom (DOF) of a subject's hand exhibiting fatigue-induced tremor. Hence this CSLDV technique potentially provides a means for measuring multiple DOF of small human body parts (e.g., fingers, tendons, small muscles) for various applications (e.g., haptic technology, remote surgery) when the use of skin-mounted sensors (e.g. accelerometers) can be problematic due to mass-loading artifacts or tethering issues. PMID:22978867

  6. Field performance of an all-semiconductor laser coherent Doppler lidar

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    We implement and test what, to our knowledge, is the first deployable coherent Doppler lidar (CDL) system based on a compact, inexpensive all-semiconductor laser (SL). To demonstrate the field performance of our SL-CDL remote sensor, we compare a 36 h time series of averaged radial wind speeds measured by our instrument at an 80 m distance to those simultaneously obtained from an industry-standard sonic anemometer (SA). An excellent degree of correlation (R2=0.994 and slope=0.996) is achieved from a linear regression analysis of the CDL versus SA wind speed data. The lidar system is capable of providing high data availability, ranging from 85% to 100% even under varying outdoor (temperature and humidity) conditions during the test period. We also show the use of our SL-CDL for monitoring the dependence of aerosol backscatter on relative humidity. This work points to the feasibility of a more general class of low-cost, portable remote sensors based on all-SL emitters for applications that require demanding laser stability and coherence.

  7. Characterization and demonstration of a 12-channel Laser-Doppler vibrometer

    Science.gov (United States)

    Haist, T.; Lingel, C.; Osten, W.; Bendel, K.; Giesen, M.; Gartner, M.; Rembe, C.

    2013-04-01

    Scanning laser-Doppler vibrometry is the standard optical, non-contact technology for vibration measurement applications in all areas of mechanical engineering. The vibration signals are measured from the different measurement points at different time points. This requires synchronization and the technology is limited to repeatable or periodic events. We have explored a new solution for the optical setup of the sensing system of a multi-channel vibrometer that we present in this paper. Our optical system is a 12-channel vibrometer and consists of a 12-channel interferometer unit which is connected with 12 optical fibers to a sensor head with 12 fiber-coupled objective lenses. Every objective lens can be focused manually and is placed in a sphere which can be tilted and fixed by a blocking screw. Thus it is possible to adjust a user defined measurement grid by hand. The user can define the geometry of the measurement grid in a camera image displayed in the software by just clicking on the laser foci. We use synchronous analog-digital conversion for the 12 heterodyne detector signals and a digital 12-channel-demodulator which is connected via USB to a computer. We can realize high deflection angles, good sensitivity, proper resolution, sufficient vibration bandwidth, and high maximum vibration amplitudes. In this paper, we demonstrate the optical and electrical setup of the manually adjustable 12-channel vibrometer, we present the experimentally evaluated performance of our device, and we present first measurements from real automotive applications.

  8. Laser Doppler velocimetry measurements in coaxial, co- and counter-swirling, isothermal jets

    Science.gov (United States)

    Robinson, P. A.; Cusworth, R. A.; Sislian, J. P.

    1986-05-01

    Measured values of the three components of mean velocity and the six components of the turbulent stress tensor are reported in free, co-axial, isothermal, co- and counter-swirling jet flows representative of combustor flows. The effects of specific radial distributions of mean swirl velocity, and co- and counter-swirling annular flows on the flow field are investigated. A one-dimensional laser Doppler velocimeter is used to obtain the measurements. It consists of a 15mW He-Ne laser, DISA 55x modular optics with a Bragg cell and electronic frequency shifting to handle high turbulence intensities and reverse flow regions, and a TSI model 1980A counter processor. Measured values are presented for two tangential velocity profiles in co- and counter-swirling annular flows, in all, for four different cases. A central recirculation zone occurs in each case. Streamlines are calculated from the measured velocity distribution, and contours of turbulent kinetic energy are presented. The former show the structure of the CRZ, and the latter indicate the zones of high turbulence intensity. Experimental data indicate that the flows are more affected by the direction of rotation of the annular flow than by altering the radial distribution of mean swirl velocity. Counter-swirl tends to increase the turbulent stresses with the maxima occuring near the boundary of the CRZ.

  9. Skin blood flow from gas transport: helium xenon and laser Doppler compared

    International Nuclear Information System (INIS)

    A study was designed to compare three independent measures of cutaneous blood flow in normal healthy volunteers: xenon-133 washout, helium flux, and laser velocimetry. All measurements were confined to the volar aspect of the forearm. In a large group of subjects we found that helium flux through intact skin changes nonlinearly with the controlled local skin temperature whereas helium flux through stripped skin, which is directly proportional to skin blood flow, changes linearly with cutaneous temperature over the range 33 degrees to 42 degrees. In a second group of six volunteers we compared helium flux through stripped skin to xenon-133 washout (intact skin) at a skin temperature of 33 degrees, and we found an essentially linear relationship between helium flux and xenon measured blood flow. In a third group of subjects we compared helium flux blood flow (stripped skin) to laser doppler velocimetric (LDV) measurements (intact skin) at adjacent skin sites and found a nonlinear increase in the LDV skin blood flow compared to that determined by helium over the same temperature range. A possible explanation for the nonlinear increases of helium flux through intact skin and of LDV output with increasing local skin temperature is that they reflect more than a change in blood flow. They may also reflect physical changes in the stratum corneum, which alters its diffusional resistance to gas flux and its optical characteristics

  10. Glass-fiber self-mixing intra-arterial laser Doppler velocimetry: signal stability and feedback analysis

    Science.gov (United States)

    de Mul, Frits F. M.; Scalise, Lorenzo; Petoukhova, Anna L.; van Herwijnen, Marc; Moes, Paul; Steenbergen, Wiendelt

    2002-02-01

    We have developed a blood velocimeter based on the principle of self-mixing in a semiconductor laser diode through an optical fiber. The intensity of the light is modulated by feedback from moving scattering particles that contain the Doppler-shift frequency. Upon feedback the characteristics of the laser diode change. The threshold current decreases, and an instable region may become present above the new threshold. The amplitude of the Doppler signal turns out to be related to the difference in intensity between situations with and without feedback. This amplitude is highest just above feedback. The suppression of reflection from the glass-fiber facets is of paramount importance in the obtaining of a higher signal-to-noise ratio. Using an optical stabilization of the feedback, we optimized the performance of the laser-fiber system and the Doppler modulation depth and clarified its behavior with a suitable physical model. We also investigated the effect of the finite coherence length of the laser. We tested the efficiency of the self-mixing velocimeter in vivo with the optical glass fiber inserted in the artery with endoscopic catheters, both in upstream and in downstream blood flow conditions. For the latter we used a special side-reflecting device solution for the fiber facet to allow downstream measurements.

  11. Use of Wigner-Ville transformations for fluid particles in laser Doppler flow accelerometry

    International Nuclear Information System (INIS)

    Flow acceleration with Lagrangian description is crucial to understanding particle movements in turbulent jet flows or dissipation statistics in isotropic turbulence. Laser Doppler anemometry is regarded as a suitable experimental tool for measuring flow acceleration, because scattering particles generate trajectories in the measurement volume, which process gives rise to flow acceleration at a fixed measuring point with the Lagrangian description. The most useful algorithm for processing Doppler signals is either the quadrature demodulation technique (QDT) or the iterative parametric method (alternatively, the minimization of least squares, LSM) as in the literature. In the present study, another algorithm using the Wigner-Ville transform (W-V) is introduced to give more accurate estimation of flow acceleration than the QDT or the LSM. Five signal-processing algorithms, including the QDT, the LSM, the MC (maximization of correlation), and the W-V, were compared with each other in experiments with an impinging air jet flow with a cylindrical rod and a round free-air jet flow. Mean flow acceleration distribution in the stream wise direction was mainly investigated. Processing speeds for the above-mentioned signal-processing algorithms were checked to find the best algorithm, which has best performance with short processing time. Although QDT was found to be an accurate algorithm with short processing time, it has limited applications to flows with large acceleration anations to flows with large acceleration and high SNR. The MC was also found to be a good algorithm with moderate processing speed, which can be useful in flows with low SNR because the MC is an iterative parametric method. The W-V gave the most accurate values for flow acceleration; however, the processing time for this method was the slowest among the signal-processing algorithms

  12. Evaluation of algorithms for microperfusion assessment by fast simulations of laser Doppler power spectral density

    International Nuclear Information System (INIS)

    In classical laser Doppler (LD) perfusion measurements, zeroth- and first-order moments of the power spectral density of the LD signal are utilized for the calculation of a signal corresponding to the concentration, speed and flow of red blood cells (RBCs). We have analysed the nonlinearities of the moments in relation to RBC speed distributions, parameters of filters utilized in LD instruments and the signal-to-noise ratio. We have developed a new method for fast simulation of the spectrum of the LD signal. The method is based on a superposition of analytically calculated Doppler shift probability distributions derived for the assumed light scattering phase function. We have validated the method by a comparison of the analytically calculated spectra with results of Monte Carlo (MC) simulations. For the semi-infinite, homogeneous medium and the single Doppler scattering regime, the analytical calculation describes LD spectra with the same accuracy as the MC simulation. The method allows for simulating the LD signal in time domain and furthermore analysing the index of perfusion for the assumed wavelength of the light, optical properties of the tissue and concentration of RBCs. Fast simulations of the LD signal in time domain and its frequency spectrum can be utilized in applications where knowledge of the LD photocurrent is required, e.g. in the development of detectors for tissue microperfusion monitoring or in measurements of the LD autocorrelation function for perff the LD autocorrelation function for perfusion measurements. The presented fast method for LD spectra calculation can be used as a tool for evaluation of signal processing algorithms used in the LD method and/or for the development of new algorithms of the LD flowmetry and imaging. We analysed LD spectra obtained by analytical calculations using a classical algorithm applied in classical LD perfusion measurements. We observed nonlinearity of the first moment M1 for low and high speeds of particles (v ?1, v > 10 mm s?1). It was also noted that the first moment M1 is less sensitive to the change of the mean RBC speed for flat speed distributions. The low-pass filter frequency f2 implemented in the LD instrument has a significant influence on the first moment of the spectrum. In particular, for a cut-off frequency lower than 10 kHz the M1 value is strongly underestimated.

  13. Response analysis of electromagnetic flowmeter

    International Nuclear Information System (INIS)

    In liquid-metal-cooled fast breeder reactors (LMFBRs), electromagnetic flowmeters (EMFs) have been extensively used to measure the coolant flow rate. Because the coolant flow rate is one of the most important parameters, a high accuracy and a fast response are required for the flow rate measurement. However, it was thought that the response might become slower when the pipe diameter of the EMF was increased. Therefore, a quantitative evaluation of the response was needed. To evaluate the response time of EMFs, an equation of the transient response was derived based on the realistic approximation that the EMF pipe is made of nonconductive material. The response is expressed as a function of the reciprocal of the square of the pipe radius a and of the length L of the external magnetic field along the pipe axis. However, when the aspect ratio L/2a is larger than two, the length of the external magnetic field has an almost insignificant effect on the response, and the response time increases with increasing a2. The transient response can be calculated with an uncertainty of less than a few percent. A first-order approximation of the derived equation is given by the first lag term with the time constant of ??a2/3.832 with permeability ? and conductivity ? of the coolant. Even though the EMF has a diameter as large as 30 in., the response time is 45 ms and sufficiently fast compared with other sensors used in LMFBRss used in LMFBRs

  14. Observation of a critically refracted converted SP wave using laser Doppler interferometer

    Science.gov (United States)

    Gurevich, Boris; Lebedev, Maxim; Madadi, Mahyar; Bona, Andrej; Pevzner, Roman

    2015-04-01

    Laboratory measurements of elastic properties of rocks are important for calibration of seismic data and for corroboration of theoretical models of rocks. The most common way of determining the elastic properties of rock samples in laboratory settings is to estimate the velocities of ultrasonic waves propagating in different directions. The wave velocities are usually obtained from the travel times of waves generated and recorded by ultrasonic piezoelectric transducers. This approach has a large uncertainty associated with shear-wave travel time estimation and separation of differently polarised shear waves, as well as uncertainty as to whether phase or group velocity is measured. The problems are caused by the relatively large size and small number of transducers. One way to address some of these issues is by using laser Doppler interferometer, which records a particle like movement that can serve to separate the waves and to pick the travel times from which the ray velocities cab be estimated reliably, and with a huge data redundancy. In this paper, laser Doppler interferometer is used to record wave propagation in an anisotropic rock sample by measuring three orthogonal components of particle velocity on the sample surface. These measurements allow a clear separation of different wave types. The travel time of these waves are used for estimation of anisotropy parameters of the sample. A key observation is the very strong wave which at small offsets has traveltimes equal to those of the S-wave, but at large offsets travels with a velocity close to that of the P-wave. We interpret this wave as a converted SP wave critically refracted at the free surface. The nature and characteristics of this wave are confirmed by numerical simulations in both isotropic and anisotropic media. These simulations show the same traveltimes as measured in the experiment, but the amplitude of the converted SP wave is much stronger in the measured data. Analysis of this inconsistency is part of the future research, but perhaps one possible explanation is a complex radiation pattern of the source. Such a non-trivial radiation pattern is probably also the reason for the different frequency content in the SH and P-waves compared to the SV and the critically refracted SP wave. Knowledge of the radiation pattern of the source will allow it to be deconvolved from the observed data. Based on our preliminary results, such a deconvolution would also allow us to use semblance as a fitting algorithm, which would eliminate the need to pick the travel times and make the fitting more robust.

  15. Multi-channel laser Doppler velocimetry using a two-dimensional optical fiber array for obtaining instantaneous velocity distribution characteristics

    Science.gov (United States)

    Kyoden, Tomoaki; Yasue, Youichi; Ishida, Hiroki; Akiguchi, Shunsuke; Andoh, Tsugunobu; Takada, Yogo; Teranishi, Tsunenobu; Hachiga, Tadashi

    2015-01-01

    A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.

  16. Doppler velocimetry using self-mixing effect in a short Er Yb-doped phosphate glass fiber laser

    Science.gov (United States)

    Laroche, M.; Kervevan, L.; Gilles, H.; Girard, S.; Sahu, J. K.

    2005-04-01

    Accurate and highly sensitive speed measurements have been successfully demonstrated by the optical feedback velocimetry technique using the self-mixing modulation effect in a double-clad Er Yb-doped fiber laser. The sensitivity to back-scattered light has been investigated regarding the Doppler frequency shift or the target distance, and it has been shown that the velocimeter is still sensitive to a target located at 20 m and for speeds as high as 13 m s-1.

  17. Applying Laser Doppler Anemometry inside a Taylor-Couette geometry - Using a ray-tracer to correct for curvature effects

    OpenAIRE

    Huisman, Sander G.; van Gils, Dennis P. M.; Sun, Chao

    2012-01-01

    In the present work it will be shown how the curvature of the outer cylinder affects Laser Doppler anemometry measurements inside a Taylor-Couette apparatus. The measurement position and the measured velocity are altered by curved surfaces. Conventional methods for curvature correction are not applicable to our setup, and it will be shown how a ray-tracer can be used to solve this complication. By using a ray-tracer the focal position can be calculated, and the velocity ...

  18. Measurement of flow velocities in a model of blood vessel by laser doppler anemometer (1D LDA)

    International Nuclear Information System (INIS)

    In this paper results of measuring velocities in a simple profile by laser doppler anemometer (1D LDA) are presented. Further work on the project will include research in models of normal and changed configurations related to human pathology. The profile of flow velocities and level of turbulence are determined for a cylindrical tube with 18 mm diameter, which approximately presents an usual radius of aorta. (author)

  19. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    International Nuclear Information System (INIS)

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  20. Material properties identification using ultrasonic waves and laser Doppler vibrometer measurements: a multi-input multi-output approach

    International Nuclear Information System (INIS)

    In this paper a multi-input multi-output approach able to determine the material properties of homogeneous materials is presented. To do so, an experimental set-up which combines the use of multi harmonic signals with interleaved frequencies and laser Doppler vibrometer measurements has been developed. A modeling technique, based on transmission and reflection measurements, allowed the simultaneous determination of longitudinal wave velocity, density and thickness of the materials under test with high levels of precision and accuracy. (paper)

  1. A comparison of pulse oximetry and laser Doppler flowmetry in monitoring sequential vascular occlusion in a rabbit ear model

    OpenAIRE

    Hallock, Geoffrey G.; Rice, David C.

    2003-01-01

    The ultimate success of any free flap transfer depends not only on the experience of the given surgical team, but also requires constant vigilance in the perioperative period to assure continued anastomotic patency. Clinical acumen remains the ‘industry’ standard, but adjunctive monitoring devices are important to reinforce these subjective evaluations. We routinely use laser Doppler flowmetry in spite of known drawbacks, including expense. On the other hand, we know that pulse oximetry is a ...

  2. Development of a laser-Doppler system for measurement of velocity fields in PVT crystal growth systems

    Science.gov (United States)

    Jones, O. C.; Glicksman, M. E.; Lin, J. T.; Kim, G. T.; Singh, N. B.

    1991-01-01

    A laser-Doppler velocimetry (LDV) system capable of measuring velocities as low as 10 exp -5 m/s is presented, and a calibration system for determining the accuracy of the LDV system at these velocities is described. The results obtained in mercurous chloride crystal grown in cylindrical ampoules at 300 C, using physical vapor transport (PVT) methods, are presented. It is concluded that the overall flow pattern observed is a unicellular, asymmetric pattern between Rayleigh number of 125 and 250.

  3. Microvascular involvement in systemic sclerosis: laser Doppler evaluation of reactivity to acetylcholine and sodium nitroprusside by iontophoresis

    OpenAIRE

    Civita, L; Rossi, M.; Vagheggini, G; F. Storino; Credidio, L; Pasero, G; Giusti, C.; C Ferri

    1998-01-01

    OBJECTIVES—To investigate the skin vasodilatory response to iontophoretically applied acetylcholine (Ach), an endothelium dependent vasodilator, and to sodium nitroprusside (SNP), an endothelium independent vasodilator, in patients with systemic sclerosis (SSc).?METHODS—Eleven SSc patients were preliminarily studied (10 females, mean age 40.5; mean disease duration 6.5 years), and 16 age and sex matched control subjects. By means of laser Doppler flowmetry skin blood flow was evaluat...

  4. A Tool for the Spectral Analysis of the Laser Doppler Anemometer Data of the Cambridge Stratified Swirl Burner

    OpenAIRE

    Zhou, Ruigang; Balusamy, Saravanan; Hochgreb, Simone

    2012-01-01

    A series of flow fields generated by a turbulent methane/air stratified swirl burner are investigated using laser Doppler anemometer (LDA). The LDA provides flow field measurements with comparatively high temporal resolutions. However, processing of the power spectral energy density (PSD) and autocorrelation functions (ACF) of the flow velocity by LDA is complicated by the random, intermittent nature of the LDA signal caused by random arrival of particles at the measuring volume. A tool is de...

  5. Single-point relative process using Laser-Doppler velocimetry for calibration of flow sensors at temperatures above 100 C

    International Nuclear Information System (INIS)

    Due to technical difficulties, the calibration of flow sensors of heat meters above 100 C cannot be performed by the gravimetric standard method. A novel method using a laser Doppler velocimeter (LDV) was therefore developed, based on the gravimetric method below 100 C and on Reynolds' similarity law. This method allows a turbine meter to be calibrated as a secondary flowrate standard with a relative uncertainty below 0,2% for temperatures of up to 180 C. (orig.)

  6. Laser Doppler Velocimetry for Joint Measurements of Acoustic and Mean Flow Velocities : LMS-based Algorithm and CRB Calculation

    OpenAIRE

    Laurent SIMON; Richoux, Olivier; Degroot, Anne; Lionet, Louis

    2007-01-01

    This paper presents a least mean square (LMS) algorithm for the joint estimation of acoustic and mean flow velocities from laser doppler velocimetry (LDV) measurements. The usual algorithms used for measuring with LDV purely acoustic velocity or mean flow velocity may not be used when the acoustic field is disturbed by a mean flow component. The LMS-based algorithm allows accurate estimations of both acoustic and mean flow velocities. The Cram\\'er-Rao bound (CRB) of the asso...

  7. The direction discrimination of single-mode VCSEL self-mixing laser Doppler velocimeters using automatic tracking triangular wave modulation

    Science.gov (United States)

    He, Deyong; Xu, Jun; Gui, Huaqiao; Lv, Liang; Zhao, Tianpeng; Ming, Hai; Xie, Jianping

    2005-01-01

    SM-LDV (Self-Mixing Type Laser Doppler Velocimeter) using single mode VCSEL (Vertical Cavity Surface Emitting Lasers) has many characteristic such as high accuracy of velocity measurement, low power dissipation and low cost. The saw-tooth waveform of Doppler signal can be used to discriminate the motion direction. Because of low light power of single mode VCSEL, the backscattered light is so weak that the saw-tooth waveform is not good enough to discriminate the motion direction. SM-LDV direction discrimination using single mode VCSEL modulated by triangular wave is not obviously dependent on the light power of Laser and its reliability is better. The dynamic range is very narrow when the VCSEL is modulated by constant frequency triangular wave. We present a method that VCSEL is modulated by triangular wave whose frequency is tracking the divided frequency of Doppler frequency shift (fD) and it can expand the dynamic range more than one order of magnitude. The results show that the dynamic range of direction discrimination can reach 5-500mm/s when the wavelength of single mode VCSEL is 850nm and the operating current is 8.6mA, the frequency of triangular wave is fD/16,the modulation current of triangular wave is 0.042mA.

  8. Effect of angle of incidence on self-mixing laser Doppler velocimeter and optimization of the system

    Science.gov (United States)

    Huang, Wei; Gui, Huaqiao; Lu, Liang; Xie, Jianping; Ming, Hai; He, Deyong; Wang, Huanqin; Zhao, Tianpeng

    2008-03-01

    Based on the theory of speckle and self-mixing interference in laser-diode, three-facet cavity model is introduced to analyze laser Doppler effect based on self-mixing interference in the case of a rough surface, and numerical solution of the signal is obtained. Simulation results of speckle-modulated Doppler signal based on self-mixing effect and tracking accuracy at different incident angles are given using parameters employed in the experiment. Simulation results indicate incident angle of around 30° is most suitable when both tracking accuracy and signal amplitude are considered. Experimental waveforms agree well with simulation results, and similar conclusions as simulation predictions about changing trend of tracking accuracies of the system at different incident angles can be made. Combining with difference frequency analog phase-lock loop (PLL) technique and appropriate sampling time, a laser Doppler velocimeter with tracking accuracy better than 1.3% in the range of 10-470 mm/s is realized.

  9. Resonant Doppler velocimeter

    Science.gov (United States)

    Miles, R. B.

    1975-01-01

    Narrow linewidth tunable lasers augur a new kind of laser Doppler velocimetry employing resonant absorption and fluorescence from trace atomic species rather than scattering from particles. This technique may provide better turbulence and small volume information than present velocimetry.

  10. The “Swiss-cheese Doppler-guided laser tonsillectomy”: a new safe cribriform approach to intracapsular tonsillectomy

    OpenAIRE

    Palmieri, B.; Iannitti, T.; Fistetto, G.; Rottigni, V.

    2012-01-01

    Outpatient laser ablation of palatine tonsils is a very interesting procedure that has been recently introduced as a routine in head and neck surgery departments. The aim of this study was to describe a new strategy using a Doppler-guided fibre optic neodymium-yttrium–aluminium–garnet (YAG) laser to remove up to 80 % of tonsillar tissue, as assessed in the long-term postoperative clinical evaluation of the volume of the tonsils at the follow-up, and leaving the capsule in place, thus avo...

  11. Sub-Doppler Two-Photon Laser Spectroscopy of Antiprotonic Helium and the Antiproton-to-Electron Mass Ratio

    International Nuclear Information System (INIS)

    The ASACUSA collaboration of CERN has recently irradiated antiprotonic helium atoms with two counter-propagating laser beams. This excited some non-linear two-photon transitions of the antiproton at the deep UV wavelengths ? = 139.8–197.0 nm. The counterpropagating geometry of the laser beams reduced the thermal Doppler broadening of the observed resonances. Their narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3–5 parts in 109. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). (author)

  12. Directional-sensitive differential laser Doppler vibrometry for in-plane motion measurement of specular surface

    Science.gov (United States)

    Agusanto, Kusuma; Lau, Gih-Keong; Wu, Kun; Liu, Ting; Zhu, Chuangui; Yuan, Ling

    2015-03-01

    A new method for measuring in-plane vibration velocity of glossy and specular surface using differential laser Doppler vibrometer (LDV) is proposed in this work. A standard tangential LDV using similar differential configuration is only able to measure in-plane velocity of objects with rough surface, due to its inherent on-axis optical design that collects backscatter light along its optical axis. The proposed method adopts an off-axis detection scheme, in which the photodetector is decoupled from LDV, and placed along the dominant direction of the scattered light. For optimal placement, the bidirectional reflectance distribution function (BRDF) of the sample must be considered ideally, but in our measurement tests, the off-axis detection along the direction of specular reflection is sufficient to obtain good measurement results. Another advantage with this setup is that it also works with the objects with rough surface. Experimental works using the standard tangential LDV and a prototype of this method were conducted to measure the in-plane motion of four different samples representing rough, glossy and mirror-like surface. An electrodynamic shaker was used to provide the in-plane motion of the samples at three different frequencies. A single point axial vibrometer was used to validate the in-plane velocity of the measurement from both in-plane LDVs. Some preliminary results showed that the in-plane motion of the object with glossy and specular surface can be measured using the proposed method.

  13. Physiological effects of indomethacin and celecobix: an S-transform laser Doppler flowmetry signal analysis

    International Nuclear Information System (INIS)

    Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing of laser Doppler flowmetry (LDF) signals using the S-transform. The approach is motivated by the excellent localization, in both time and frequency, afforded by the wavelet basis functions. Suitably chosen Gaussian wavelet functions are used to characterize the subspace of signals that have a given localized time-frequency support, thus enabling a time-frequency partitioning of signals. In this paper, the goal is to study the influence of various pharmacological substances taken by the oral way (celecobix (Celebrex (registered) ), indomethacin (Indocid (registered) ) and placebo) on the physiological activity behaviour. The results show that no statistical differences are observed in the energy computed from the time-frequency representation of LDF signals, for the myogenic, neurogenic and endothelial related metabolic activities between Celebrex and placebo, and Indocid and placebo. The work therefore proves that these drugs do not affect these physiological activities. For future physiological studies, there will therefore be no need to exclude patients having taken cyclo-oxygenase 1 inhibitions

  14. Fractal scaling of laser Doppler flowmetry time series in patients with essential hypertension.

    Science.gov (United States)

    Esen, Ferhan; Ca?lar, Sayin; Ata, Necmi; Ulus, Taner; Birdane, Alpaslan; Esen, Hamza

    2011-11-01

    The full diagnostic potential of the fractal complexity measure, ?, of detrended fluctuation analysis (DFA) has not been realized yet. To reveal the impaired mechanisms in the blood flow regulation in patients with essential hypertension (EHT), we studied the laser Doppler flowmetry (LDF) time series by applying DFA. Forearm microvascular blood flow was measured by LDF during supine rest. After a 15 min baseline recording, microvascular response to thermal hyperemia was measured over 30 min. We found three distinct scaling regions; corresponding to the integration of local mechanisms, cardiac effect on local blood flow, and the coupling of extrinsic factors (cardiac and respiratory) to local blood flow by myogenic mechanism. In the control group, local scaling exponent, ?(L)=0.96 ± 0.08, did not change but cardiac scaling exponent, ?(C)=1.53 ± 0.05, for baseline signal was increased to ?(CT)=1.73 ± 0.10 and cardio-respiratory scaling exponent, ?(CR)=0.73 ± 0.19, was decreased to ?(CRT)=0.24 ± 0.06 during vasodilatation in response to local heating. However, we found significantly different scaling exponents, ?(LT)0.5 in patients with EHT. Our findings suggest that the local regulatory and the cushioning peripheral vascular functions are impaired in patients with EHT, and vascular/microvascular pathology can be evaluated by applying DFA to LDF signal. PMID:21854788

  15. Absorption and scattering coefficient dependence of laser-Doppler flowmetry models for large tissue volumes

    International Nuclear Information System (INIS)

    Based on quasi-elastic scattering theory (and random walk on a lattice approach), a model of laser-Doppler flowmetry (LDF) has been derived which can be applied to measurements in large tissue volumes (e.g. when the interoptode distance is >30 mm). The model holds for a semi-infinite medium and takes into account the transport-corrected scattering coefficient and the absorption coefficient of the tissue, and the scattering coefficient of the red blood cells. The model holds for anisotropic scattering and for multiple scattering of the photons by the moving scatterers of finite size. In particular, it has also been possible to take into account the simultaneous presence of both Brownian and pure translational movements. An analytical and simplified version of the model has also been derived and its validity investigated, for the case of measurements in human skeletal muscle tissue. It is shown that at large optode spacing it is possible to use the simplified model, taking into account only a 'mean' light pathlength, to predict the blood flow related parameters. It is also demonstrated that the 'classical' blood volume parameter, derived from LDF instruments, may not represent the actual blood volume variations when the investigated tissue volume is large. The simplified model does not need knowledge of the tissue optical parameters and thus should allow the development of very simple and cost-effective LDF hardware

  16. Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow

    Scientific Electronic Library Online (English)

    Marcos, Pinotti; Edna M. de, Faria.

    2006-09-01

    Full Text Available Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA) is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurem [...] ents in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiments were conducted for non-pulsate flow (to study the valve performance in the peak flow) for the aorta Reynolds number ranging from 3300 to 6800. LDA interrogation volume visited five thousand and one hundred points along the flow (2500 points upstream and 2600 points downstream) for each Reynolds number. Post-processing methodology was employed to obtain haemolytic potential colour-coded maps, which were related to turbulent quantities. It was observed that haemolytic regions tend to move downstream the valve when the flow rate is increased.

  17. In-field use of laser Doppler vibrometer on a wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Rumsey, M.; Hurtado, J.; Hansche, B. [and others

    1998-12-31

    One of our primary goals was to determine how well a laser Doppler vibrometer (LDV) could measure the structural dynamic response of a wind turbine that was parked in the field. We performed a series of preliminary tests in the lab to determine the basic limitations of the LDV for this application. We then instrumented an installed parked horizontal axis wind turbine with accelerometers to determine the natural frequencies, damping, and mode shapes of the wind turbine and rotor as a baseline for the LDV and our other tests. We also wanted to determine if LDV modal information could be obtained from a naturally (wind) excited wind turbine. We compared concurrently obtained accelerometer and LDV data in an attempt to assess the quality of the LDV data. Our test results indicate the LDV can be successfully used in the field environment of an installed wind turbine, but with a few restrictions. We were successful in obtaining modal information from a naturally (wind) excited wind turbine in the field, but the data analysis requires a large number of averaged data sets to obtain reasonable results. An ultimate goal of this continuing project is to develop a technique that will monitor the health of a structure, detect damage, and hopefully predict an impending component failure.

  18. Laser Doppler vibrometry measures of physiological function: evaluation of biometric capabilities

    Science.gov (United States)

    Chen, Mei; O'Sullivan, Joseph A.; Singla, Naveen; Sirevaag, Erik J.; Rohrbaugh, John W.

    2009-05-01

    A novel approach using mechanical physiological activity as a biometric marker is described. Laser Doppler Vibrometry is used to sense activity in the region of the carotid artery, related to arterial wall movements associated with the central blood pressure pulse. The non-contact basis of the LDV method has several potential benefits in terms of the associated non-intrusiveness. Several methods are proposed that use the temporal and/or spectral information in the signal to assess biometric performance both on an intra-session basis, and on an intersession basis involving testing repeated after delays of 1 week to 6 months. A waveform decomposition method that utilizes principal component analysis is used to model the signal in the time domain. Authentication testing for this approach produces an equal-error rate of 0.5% for intra-session testing. However, performance degrades substantially for inter-session testing, requiring a more robust approach to modeling. Improved performance is obtained using techniques based on time-frequency decomposition, incorporating a method for extracting informative components. Biometric fusion methods including data fusion and information fusion are applied in multi-session data training model. As currently implemented, this approach yields an inter-session equal-error rate of 9%.

  19. Hidden state models for noncontact measurements of the carotid pulse using a laser Doppler vibrometer.

    Science.gov (United States)

    Kaplan, Alan D; O'Sullivan, Joseph A; Sirevaag, Erik J; Lai, Po-Hsiang; Rohrbaugh, John W

    2012-03-01

    The method of laser Doppler vibrometry (LDV) is used to sense movements of the skin overlying the carotid artery. When pointed at the skin overlying the carotid artery, the mechanical movements of the skin disclose physiological activity relating to the blood pressure pulse over the cardiac cycle. In this paper, signal modeling is addressed, with close attention to the underlying physiology. Segments of the LDV signal corresponding to single heartbeats, called LDV pulses, are extracted. Hidden Markov models (HMMs) are used to capture the dynamics of the LDV pulses from beat to beat based on pulse morphology; under resting conditions these dynamics are primarily due to respiration-related effects. LDV pulses are classified according to state, by computing the optimal state path through the data using trained HMMs. HMM state dynamics are examined within the context of respiratory effort using strain gauges placed around the abdomen. This study presented here provides a graphical model approach to modeling the dependence of the LDV pulse on latent states. PMID:22167558

  20. Critical flow regions in tissue artificial heart valve assessed by laser doppler anemometer in continuous flow

    Directory of Open Access Journals (Sweden)

    Pinotti Marcos

    2006-01-01

    Full Text Available Flow diagnosis using non-invasive techniques such laser Doppler anemometer (LDA is an important tool to improve the design of artificial heart valves. In the present study, an experimental protocol to obtain flow velocity field and colour coded maps of turbulent eddies dimensions using LDA measurements in a 25 mm bovine pericardium bio prosthesis valve is reported. A transparent Plexiglas chamber was specially designed to allow optical access to the flow passing through the valve. Experiments were conducted for non-pulsate flow (to study the valve performance in the peak flow for the aorta Reynolds number ranging from 3300 to 6800. LDA interrogation volume visited five thousand and one hundred points along the flow (2500 points upstream and 2600 points downstream for each Reynolds number. Post-processing methodology was employed to obtain haemolytic potential colour-coded maps, which were related to turbulent quantities. It was observed that haemolytic regions tend to move downstream the valve when the flow rate is increased.

  1. Quantifying the correlation between photoplethysmography and laser Doppler flowmetry microvascular low-frequency oscillations

    Science.gov (United States)

    Mizeva, Irina; Di Maria, Costanzo; Frick, Peter; Podtaev, Sergey; Allen, John

    2015-03-01

    Photoplethysmography (PPG) and laser Doppler flowmetry (LDF) are two recognized optical techniques that can track low-frequency perfusion changes in microcirculation. The aim of this study was to determine, in healthy subjects, the correlation between the techniques for specific low-frequency bands previously defined for microcirculation. Twelve healthy male subjects (age range 18 to 50 years) were studied, with PPG and LDF signals recorded for 20 min from their right and left index (PPG) and middle (LDF) fingers. Wavelet analysis comprised dividing the low-frequency integral wavelet spectrum (IWS) into five established physiological bands relating to cardiac, respiratory, myogenic, neurogenic, and endothelial activities. The correlation between PPG and LDF was quantified using wavelet correlation analysis and Spearman correlation analysis of the median IWS amplitude. The median wavelet correlation between signals (right-left side average) was 0.45 (cardiac), 0.49 (respiratory), 0.86 (myogenic), 0.91 (neurogenic), and 0.91 (endothelial). The correlation of IWS amplitude values (right-left side average) was statistically significant for the cardiac (?=0.64, p<0.05) and endothelial (?=0.62, p<0.05) bands. This pilot study has shown good correlation between PPG and LDF for specific physiological frequency bands. In particular, the results suggest that PPG has the potential to be a low-cost replacement for LDF for endothelial activity assessments.

  2. Measurement of acceleration and multiple velocity components using a laser Doppler velocity profile sensor

    International Nuclear Information System (INIS)

    For the investigation of turbulent flows, the measurement of Lagrangian acceleration is of great interest as it represents a direct component of the Navier–Stokes equations. The presented sensor is based on the common laser Doppler technique, but offers in addition combined high spatial resolution in the micrometre range and the possibility of measuring the velocity component along the optical axis. As a result of the sensor setup, signals of particles with inclined trajectories show frequency modulation within a single burst similar to the signal of an accelerated particle. A model-based approach to distinguish between both quantities is presented, and a signal processing technique based on the Hilbert transform has been developed. The processing is comparatively fast and showed good agreement with preset values, even for signals of poor quality. The variance of velocity and acceleration measurements nearly reaches the Cramér–Rao lower bound. Experimental verification is done by the measurement of a harmonic oscillator with known parameters and a stagnation flow within a free jet

  3. Dynamic Rotor Deformation and Vibration Monitoring Using a Non-Incremental Laser Doppler Distance Sensor

    International Nuclear Information System (INIS)

    Monitoring rotor deformations and vibrations dynamically is an important task for improving the safety and the lifetime as well as the energy efficiency of motors and turbo machines. However, due to the high rotor speed encountered in particular at turbo machines, this requires concurrently a high measurement rate and high accuracy, which can not be fulfilled by most commercially available sensors. To solve this problem, we developed a non-incremental laser Doppler distance sensor (LDDS), which is able to measure simultaneously the in-plane velocity and the out-of-plane position of moving rough solid objects with micrometer precision. In addition, this sensor concurrently offers a high temporal resolution in the microsecond range, because its position uncertainty is in principle independent of the object velocity in contrast to conventional distance sensors, which is a unique feature of the LDDS. Consequently, this novel sensor enables precise and dynamic in-process deformation and vibration measurements on rotating objects, such as turbo machine rotors, even at very high speed. In order to evidence the capability of the LDDS, measurements of rotor deformations (radial expansion), vibrations and wobbling motions are presented at up to 50,000 rpm rotor speed.

  4. Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry

    International Nuclear Information System (INIS)

    The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances

  5. The photo-electric current in laser-Doppler flowmetry by Monte Carlo simulations

    International Nuclear Information System (INIS)

    Monte Carlo (MC) simulations significantly contributed to a better understanding of laser-Doppler flowmetry (LDF). Here it is shown that the data obtained from standard MC simulations can be reinterpreted and used to extract more information such as the photo-electric current (i(t)). This is important because i(t) is the starting point for evaluating any existing or new algorithm to be used in LDF instrumentation. This circumvents the tedious procedure of generating a specific model (often approximated if possible at all) each time a different algorithm is considered. By a series of tutorial examples, the influence of various parameters is investigated, e.g. sampling rate, total acquisition time and dc filtering. These cases also demonstrate the fundamental role played by the photons' random phase in the shaping of the LDF signal. In particular, it is demonstrated by MC simulation that when the number of photon-moving red blood cell interactions is too low, then the Siegert relation that exists between the field and photo-electric current autocorrelation functions does not hold. This is an important point because the validity of the Siegert relation is implicitly admitted in the majority of the classical analytical models for the autocorrelation function in LDF (the classical MC approach does not allow one to study this problem). The proposed method and examples could stimulate new ideas and help the scientific community develop, test and validate new approaches in LDop, test and validate new approaches in LDF. (note)

  6. Estimation of scattering phase function utilizing laser Doppler power density spectra

    International Nuclear Information System (INIS)

    A new method for the estimation of the light scattering phase function of particles is presented. The method allows us to measure the light scattering phase function of particles of any shape in the full angular range (0°–180°) and is based on the analysis of laser Doppler (LD) power density spectra. The theoretical background of the method and results of its validation using data from Monte Carlo simulations will be presented. For the estimation of the scattering phase function, a phantom measurement setup is proposed containing a LD measurement system and a simple model in which a liquid sample flows through a glass tube fixed in an optically turbid material. The scattering phase function estimation error was thoroughly investigated in relation to the light scattering anisotropy factor g. The error of g estimation is lower than 10% for anisotropy factors larger than 0.5 and decreases with increase of the anisotropy factor (e.g. for g = 0.98, the error of estimation is 0.01%). The analysis of influence of the noise in the measured LD spectrum showed that the g estimation error is lower than 1% for signal to noise ratio higher than 50 dB. (paper)

  7. Laser Doppler Blood Flow Imaging Using a CMOS Imaging Sensor with On-Chip Signal Processing

    Directory of Open Access Journals (Sweden)

    Cally Gill

    2013-09-01

    Full Text Available The first fully integrated 2D CMOS imaging sensor with on-chip signal processing for applications in laser Doppler blood flow (LDBF imaging has been designed and tested. To obtain a space efficient design over 64 × 64 pixels means that standard processing electronics used off-chip cannot be implemented. Therefore the analog signal processing at each pixel is a tailored design for LDBF signals with balanced optimization for signal-to-noise ratio and silicon area. This custom made sensor offers key advantages over conventional sensors, viz. the analog signal processing at the pixel level carries out signal normalization; the AC amplification in combination with an anti-aliasing filter allows analog-to-digital conversion with a low number of bits; low resource implementation of the digital processor enables on-chip processing and the data bottleneck that exists between the detector and processing electronics has been overcome. The sensor demonstrates good agreement with simulation at each design stage. The measured optical performance of the sensor is demonstrated using modulated light signals and in vivo blood flow experiments. Images showing blood flow changes with arterial occlusion and an inflammatory response to a histamine skin-prick demonstrate that the sensor array is capable of detecting blood flow signals from tissue.

  8. A study of perfusion of the distal free-TRAM flap using laser Doppler flowmetry.

    Science.gov (United States)

    Booi, Darren I; Debats, Iris B J G; Boeckx, Willy D; van der Hulst, Rene R W J

    2008-01-01

    The aim of this study was to characterise microcirculatory changes in the distal part of a flap and to evaluate whether measurement of the microcirculation may predict flap complications (FC). In this prospective study, 30 patients undergoing a delayed breast reconstruction were included. Perioperative data were recorded and with the laser Doppler flowmetry (LDF; Perimed) blood flow was recorded in the central part (zone I) and the distal part (zone IV) of the flap. A lower blood flow was observed in zone IV of patients with flap complications compared to patients without flap complications (P=0.013). In addition, LDF demonstrated different flow trends in zone I compared to zone IV indicating a delayed opening of the choke vessels connecting the angiosomes in the distal part of the flap. The LDF has proven to be a useful investigative tool to monitor microcirculatory changes. In future studies it will be used to evaluate interventions aimed at decreasing distal ischaemia and reducing flap complications. PMID:18037360

  9. Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry

    Science.gov (United States)

    Maxwell, B. R.

    1975-01-01

    A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

  10. Particle flow in blade passages of turbomachinery with application to laser-Doppler velocimetry

    Science.gov (United States)

    Maxwell, B. R.

    1974-01-01

    A theoretical analysis was conducted of the dynamic behavior of micron size particles entrained in gas flow on the two-dimensional blade-to-blade surface of a circular stationary cascade of turbine stator blades. The particle velocity lag and angular deviation relative to the gas was determined as a function of particle diameter and mass density. Particles size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that velocity lag and angular deviation increased whenever particle size or mass density increased, and that particle tracking was more sensitive to a change in particle diameter than to a change in mass density. Results indicated that LDV applications employing 1 gm/cc tracer particles with diameters greater than approximately 1 micron, or 0.5 micron diameter particles with mass densities greater than 4 gm/cc would experience velocity and angular deviations generally greater than 2 percent and 1 degree, respectively.

  11. Non-invasive technique for assessment of vascular wall stiffness using laser Doppler vibrometry

    Science.gov (United States)

    Campo, Adriaan; Segers, Patrick; Heuten, Hilde; Goovaerts, Inge; Ennekens, Guy; Vrints, Christiaan; Baets, Roel; Dirckx, Joris

    2014-06-01

    It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter is best known when estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery in the groin, but may also be determined locally from short-distance measurements on a short vessel segment. In this work, we propose a novel, non-invasive, non-contact laser Doppler vibrometry (LDV) technique for evaluating PWV locally in an elastic vessel. First, the method was evaluated in a phantom setup using LDV and a reference method. Values correlated significantly between methods (R ? 0.973 (p ? 0.01)); and a Bland-Altman analysis indicated that the mean bias was reasonably small (mean bias ? -2.33 ms). Additionally, PWV was measured locally on the skin surface of the CCA in 14 young healthy volunteers. As a preliminary validation, PWV measured on two locations along the same artery was compared. Local PWV was found to be between 3 and 20 m s-1, which is in line with the literature (PWV = 5-13 m s-1). PWV assessed on two different locations on the same artery correlated significantly (R = 0.684 (p technique to measure local vascular stiffness in a fully non-invasive way, providing new opportunities for clinical diagnosing.

  12. Ray tracing model for the estimation of power spectral properties in laser Doppler velocimetry of retinal vessels and its potential application to retinal vessel oximetry

    Science.gov (United States)

    Petrig, Benno L.; Follonier, Lysianne

    2005-12-01

    A new model based on ray tracing was developed to estimate power spectral properties in laser Doppler velocimetry of retinal vessels and to predict the effects of laser beam size and eccentricity as well as absorption of laser light by oxygenated and reduced hemoglobin. We describe the model and show that it correctly converges to the traditional rectangular shape of the Doppler shift power spectrum, given the same assumptions, and that reduced beam size and eccentric alignment cause marked alterations in this shape. The changes in the detected total power of the Doppler-shifted light due to light scattering and absorption by blood can also be quantified with this model and may be used to determine the oxygen saturation in retinal arteries and veins. The potential of this approach is that it uses direct measurements of Doppler signals originating from moving red blood cells. This may open new avenues for retinal vessel oximetry.

  13. Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model. M.S. Thesis, Final Report

    Science.gov (United States)

    Dwenger, Richard Dale

    1995-01-01

    An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

  14. Doppler line shapes in the photolysis of laser excited, aligned molecules: Application to the vibrationally mediated photodissociation of HN3

    Science.gov (United States)

    Barnes, Rhett James; Sinha, Amitabha; Dagdigian, Paul J.; Lambert, H. Mark

    1999-07-01

    A general expression for the Doppler profile for fragments produced in the photodissociation of laser excited, aligned molecules, as in vibrationally mediated photodissociation (VMP), is presented. In contrast to one-photon dissociation, for which the Doppler profile depends only on the second moment of the fragment molecular-frame angular distribution, the profile in the case of VMP is sensitive to several moments of the angular distribution, up to k=4. In addition, the profile for a near-prolate molecule depends on the angle ?a between the electronic transition moment ? and the a inertial axis. This theory is applied to the analysis and interpretation of Doppler profiles in the laser fluorescence detection of NH(a 1?) fragments, of rotational angular momenta N=7 and 10, from the 532 nm VMP of HN3 excited to the second N-H stretch overtone level (3?1). For both ?-doublets of these rotational levels, the second moment of the molecular-frame angular distribution ?2,0= was found to be positive, in agreement with previous results for high-J fragments from one-photon photolysis of HN3. The profiles are consistent with a value of ˜0° for the angle ?a. These values for ?a and ?2,0 are inconsistent with simple expectations based on planar, prompt dissociation upon excitation to the lowest singlet excited state (1A?) and suggest the importance of nonplanar geometries in the dissociation dynamics.

  15. Development and Application of an Ultrasonic Gas Flowmeter

    International Nuclear Information System (INIS)

    This paper describes the development and the field application of the ultrasonic gas flowmeter for accurate measurement of the volumetric flow rate of gases in a harsh environmental conditions in iron and steel making company. This ultrasonic flowmeter is especially suited for measuring LDG, COG, BFG gases produced in iron and steel making process. This is a transit time type ultrasonic flowmeter. We have developed the transmitting and receiving algorithm of ultrasonic wave and the ultrasonic signal processing algorithm to develope a transit time type ultrasonic flowmeter. We have evaluated the performance of ultrasonic flowmeter by the calibration system with Venturi type standard flowmeter. We has confirmed its reliability by extensive field tests for a year in POSCO, iron and steel making company. Now we have developed the commercial model of ultrasonic flowmeter and applied to the POSCO gas line

  16. Development of permanent-magnet sodium flowmeter

    International Nuclear Information System (INIS)

    Two permanent-magnet sodium flowmeters of rangs 5 m3/h and 0.5 m3/h are developed. Their constructions, the theoretical calculations of calibration characteristic and pressure loss, the calibration test and the error analysis are presented. The analytical expressions of the calibration characteristic are given

  17. A laser-lock concept to reach cm/s-precision in Doppler experiments with Fabry-Perot wavelength calibrators

    CERN Document Server

    Reiners, A; Ulbrich, R G

    2014-01-01

    State-of-the-art Doppler experiments require wavelength calibration with precision at the cm/s level. A low-finesse Fabry-Perot interferometer (FPI) can provide a wavelength comb with a very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling the FPI cavity, we propose to passively stabilize the interferometer and track the time-dependent cavity length drift externally. A dual-finesse cavity allows drift tracking during observation. The drift of the cavity length is monitored in the high-finesse range relative to an external standard: a single narrow transmission peak is locked to an external cavity diode laser and compared to an atomic frequency. Following standard locking schemes, tracking at sub-mm/s precision can be achieved. This is several orders of magnitude better than currently planned high-precision Doppler experiments. It allows freedom for relaxed designs rendering this approach particularly interesting...

  18. Studies on a Laser Doppler Interferometry gravity mission by a semi-analytical approach

    Science.gov (United States)

    Lisa, Pertusini; Mirko, Reguzzoni; Fernando, Sansò

    2010-05-01

    In the last decade, three satellite missions (CHAMP, GRACE and GOCE) have been successfully launched for the Earth gravity field observation from space. In particular, GOCE will provide a very accurate static model in terms of spherical harmonic expansion up to degree 200 and beyond, while GRACE is more sensible to time variations of the gravity field at lower resolution. A possible goal for a future mission is to measure both gravity and its variations at high resolution. This can be reached by a GRACE-like mission concept, with GOCE-quality accelerometers on board and a link between the two co-orbiting satellites based on a Laser Doppler Interferometer. In 2005 an early study on this future mission was conducted by Thales Alenia Space, leading to the definition of a possible mission profile. In that study a time-wise approach was used with the approximation of considering separately each harmonic degree of the potential in the Fourier solution of the Hill equations. This was done to obtain a fully analytical solution. In this work this approximation has been removed and the error budget of the mission has been recomputed by a semi-analytical approach. It comes out that the main effect of the approximation was in the zonal harmonics, meaning that the effect of polar gaps due to the orbit inclination was underestimated. For the other coefficients the degradation was of one order of magnitude at most, especially at low-medium harmonic degrees. An alternative mission profile based on two couples of satellites flying on two orbits with different inclination is also evaluated.

  19. Vibration transmissibility on rifle shooter: A comparison between accelerometer and laser Doppler vibrometer data

    Science.gov (United States)

    Scalise, L.; Casacanditella, L.; Santolini, C.; Martarelli, M.; Tomasini, E. P.

    2014-05-01

    The transmission of mechanical vibrations from tools to human subjects is known to be potentially dangerous for the circulatory and neurological systems. It is also known that such damages are strictly depending on the intensity and the frequency range of the vibrational signals transferred to the different anatomical districts. In this paper, very high impulsive signals, generated during a shooting by a rifle, will be studied, being such signals characterised by a very high acceleration amplitude as well as high frequency range. In this paper, it will be presented an experimental setup aimed to collect experimental data relative to the transmission of the vibration signals from the rifle to the shoulder of subject during the shooting action. In particular the transmissibility of acceleration signals, as well as of the velocity signals, between the rifle stock and the subject's back shoulder will be measured using two piezoelectric accelerometers and a single point laser Doppler vibrometer (LDV). Tests have been carried out in a shooting lab where a professional shooter has conducted the experiments, using different experimental configurations: two different types of stocks and two kinds of bullets with different weights were considered. Two uniaxial accelerometers were fixed on the stock of the weapon and on the back of the shoulder of the shooter respectively. Vibration from the back shoulder was also measured by means of a LDV simultaneously. A comparison of the measured results will be presented and the pros and cons of the use of contact and non-contact transducers will be discussed taking into account the possible sources of the measurement uncertainty as unwanted sensor vibrations for the accelerometer.

  20. New on-site calibration technique for large district heating meters using Laser Doppler Velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Drysdale, A.; Frederiksen, J.; Rasmussen, M.A. [Danish Technological Institute, Aarhus (Denmark)

    2004-07-01

    This paper presents a new method of calibrating district heating (DH) meters of 100 to 1000 mm diameter whilst on-site and in operation using Laser Doppler Velocimetry (LDV). The technique has been tested and demonstrated in the laboratory and in the field. Calibration of large DH meters using traditional methods is difficult, if not impossible. It is often a labour demanding, time consuming and costly task to remove and send a meter for off-site calibration. Using LDV for on-site calibration is an attractive alternative. LDV is an established optical technique for measuring point velocity in clear gasses and fluids and is used in a wide range of R and D applications. Using LDV it is now possible to carry out accredited on-site calibration of large DH flow meters with water flow velocities from 0.01 to 6.0 m/s. Using the LDV technique field measurements can be carried out with an uncertainty of {+-}0.9% depending on specific flow conditions and accuracy requirements. Calibration is based on a series of measurements taken over 2 to 4 diameters and optical access to the DH water is obtained by installing specially designed windows close to the flow meter. Point velocity measurements are converted to volume flow rate by using known flow rate estimation techniques. In addition to flow rate estimates the LDV technique can also be utilised to map flow conditions, such as the result of disturbances such as pipe bends and valves. By rotating the LDV measurement instrument about the optical axis the tangential or swirl velocity component can be measured and the degree of swirl and flow disturbance can be mapped. The technique and practical experience from measurements will be presented. Examples of laboratory and field measurements, including examples of flow profiles for non-disturbed and disturbed flow conditions will be given. (orig.)

  1. Effect of captopril on skin blood flow following intradermal bradykinin measured by laser Doppler flowmetry.

    Science.gov (United States)

    Li Kam Wa, T C; Almond, N E; Cooke, E D; Turner, P

    1989-01-01

    The effect of captopril on skin response to intradermal injection of bradykinin was investigated by laser Doppler flowmetry (LDF) and weal and flare measurements in this randomised, double-blind, placebo-controlled, cross-over balanced study. Intradermal injections of 1 and 2.5 micrograms of bradykinin and normal saline were made into the forearm skin of six healthy volunteers between 1 and 2 h (t1) and between 3 and 4 h (t2) after either 25 mg captopril or placebo. Skin blood flow outside the induced weal was monitored continuously by LDF for 15 min and the mean LDF values over the last 15 s were used for analysis. Weal and flare sizes were measured at 15 min. On the placebo days, the mean LDF output, weal volume and flare area increased with incremental bradykinin dose. Pre-treatment with captopril significantly increased LDF output following intradermal bradykinin at t1 but not at t2. At both t1 and t2, captopril significantly increased weal volume. There was no significant difference between treatments in flare areas. Skin response following intradermal normal saline, measured by the above parameters, was not affected by captopril. This study showed that captopril potentiated the effects of intradermal bradykinin both with respect to blood flow changes and weal formation. The non-invasive technique of LDF can be used to detect the skin blood flow changes induced by intradermal bradykinin and the potentiation of this effect by captopril. It appears to be a useful and more objective method of quantifying local cutaneous blood flow changes than measurement of flare area. PMID:2532136

  2. Velocity measurement inside a motored internal combustion engine using three-component laser Doppler anemometry

    Science.gov (United States)

    Chan, V. S. S.; Turner, J. T.

    2000-10-01

    A three-component laser Doppler anemometry (LDA) system has been employed to investigate the structure of the flow inside the cylinder of a motored internal combustion engine. This model engine was reasonably representative of a typical, single cylinder, spark ignition engine although it did not permit firing. It was equipped with overhead valve gear and optical access was provided in the top and side walls of the cylinder. A principal objective was to study the influence of the inlet port design on the flow within the cylinder during the induction and compression strokes of the engine. Here, it can be noted that results obtained in an unfired engine are believed to be representative of the flow behaviour before combustion occurs in a fired engine (see P.O. Witze, Measurements of the spatial distribution and engine speed dependence of turbulent air motion in an i.c. engine, SAE Paper No. 770220, 1977; Witze, Sandia Laboratory Energy Report, SAND 79-8685, Sandia Laboratories, USA, 1979). Experimental data presented for an inclined inlet port configuration reveal the complex three-dimensional nature of the flow inside the model engine cylinder. Not surprisingly, the results also show that the inclined inlet port created flow conditions more favourable to mixing in the cylinder. Specifically, the inclined inlet flow was found to generate a region with a relatively high shear and strong recirculation zones in the cylinder. Inclining the inlet port also produced a more nearly homogeneous flow structure at top dead centre during the compression stroke. The paper identifies the special difficulties encountered in making the LDA measurements. The experimental findings are examined and the problems that arise in presenting time-varying three-dimensional data of this type are discussed. Finally, the future potential of this experimental approach is explored.

  3. Laser Doppler measurement and CFD validation in 3 × 3 bundle flow

    International Nuclear Information System (INIS)

    Highlights: • Five-beam LDV is operated in the three-beam mode to measure 3 × 3 bundle flow. • Correlation and FFT techniques are applied to analyze the flow structure. • Large coherent structure is observed in gaps between different subchannels. • The Reynolds stress models predict weak mixing between different subchannels. - Abstract: The five-beam three-component laser Doppler system is operated in the three-beam two-component mode to measure the 3 × 3 bundle flow with simple grid spacer. Experiment has been conducted at Re = 15,200 and 29,900. According to the experiment result, the root mean square (RMS) of axial velocity fluctuation shows large value in the gap and the near-wall region of the edge sub-channel which is induced by the axial velocity gradient. Significant intensity of lateral velocity fluctuation is observed which indicates the strong lateral mixing in a 3 × 3 rod bundle. Through the correlation analysis coherent structures have been observed in the gap region. The spectral analysis shows that the LDV measurement complies to the Komogorov spectrum law, f?5/3, well. The low-frequency peak spectral density of the axial velocity fluctuation has been observed in the gap region connecting sub-channels with velocity difference. The performance of the SSG model and the baseline Reynolds stress model are investigated based on the experiment result. The models predict higher axial velocity in the interior sub-channel and lower in the edge and corner ones than the experiment result. Large discrepancy between the calculated and measured axial flow velocity is resulted from failure in calculating the strong negative u?w?¯ in the gap region connecting different sub-channels

  4. Experimental investigation of a vertical planar jet by ultrasound and laser Doppler velocimetry

    International Nuclear Information System (INIS)

    An experimental investigation on the velocity field of a water-jet injected vertically into a water pool was conducted. The jet flowed from a thin rectangular nozzle and was considered to be quasi-planar as it was confined along two parallel planes. Velocity measurements of the jet and the surrounding entrained flow regions were made respectively by ultrasound and laser Doppler velocimetries (UDV and LDV). In contrast to LDV, UDV operates on the principle of pulsed ultrasound echography and in our experiment, a single transducer held at a 10deg angle with respect to horizontal (x-axis) was vertically traversed. The measured velocity thus represents the velocity component along this beam angle. The hydraulic diameter (D) based Reynolds numbers of flow were, Re=1.79 x 104 (UDV), 3.58 x 104 (LDV), 7.15 x 104 (LDV), corresponding to average exit velocities of 0.5, 1.0 and 2.0 m/s. Comparisons of the traditional jet parameters, such as the decay of the centerline and jet's half-radius vs. axial distance (z-axis), against established data confirmed proper jet-like behavior of our test facility. The conclusions from the experiments were as follows: (1) that UDV shows trends and magnitudes similar to data obtained by LDV; both velocimetry methods are applicable to this type of experimental flow configuration, (2) data presented as the axial decay of centerline velocity and jet half-radius, are consistent and similar to past experimental data, nt and similar to past experimental data, mostly of gas jets, and (3) radial profiles show agreement with a past correlation up to R/R1/2=1. There are differences however, between the correlation and the data, for R/R1/2?1, the latter which were showed consistent trends. (author)

  5. Laser-Doppler-measurements of power-density-spectra in a turbulent channel flow

    International Nuclear Information System (INIS)

    In this paper the results of measurements in a turbulent channel flow are presented. A Laser-Doppler-Anemometer is used. The fluid is water. The velocity component in the direction of the main flow and one component perpendicular to it are recorded. Both the Reynolds-number and the distance to the wall are varied. Particularly, the power-density-spectra of the velocity fluctuations are evaluated. These spectra are investigated in details distinguishing three different wavenumber ranges. The range of lower wavenumbers, respectively frequencies are presented by an approximation equation, and an empirical length-scale appearing in that equation is determined. A subrange having an -1-exponent is also investigated. The theoretically predicted shape of the spectrum in the intermediate wavenumber range is verified by the measurements. The two wavenumbers representing the lower respectively the upper limit of that range are determined as a function of Reynolds-number. In the upper range, the spectra are contaminated by a significant amount of noise which is shown to be a consequence of the measurement-method itself. The reasons and possible method to eliminate the noise are discussed. The spectral variation of the energy ratio for the different velocity directions and the existence of isotropy were considered. The results are spectra in a Reynolds-number range where the validity of the common 'universal' relations cannot be generally assumed. The deductions can be used to support models which are employed for the numerical simulation of turbulent flows and which require the knowledge of power-density-spectra. (orig.)

  6. New laser Doppler velocimetry using self-mixing effect in a vertical-cavity surface-emitting laser modulated by triangular current

    Science.gov (United States)

    Gui, Huaqiao; Lv, Liang; Xu, Jun; He, Deyong; Li, Feng; Wang, Anting; Xie, Jianping; Zhao, Tianpeng; Ming, Hai

    2005-01-01

    A new, compact laser Doppler velocimetry is proposed, which is composed of a single-mode vertical-cavity surface-emitting laser modulated by a dynamical triangular current and a collimating lens. It can indicate the direction of velocity without ambiguity in the wide dynamic range of 5.2mm/s to 479.9mm/s when the sampling time is 0.1 second in the measurement. The accuracy of velocity measurement is better than 3.1% in the whole velocity range. What's more, this LDV works very well on different diffusing surfaces, even on a black glossy photographic paper.

  7. Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, Alexander D.; Banishev, Alexandr A.; Shaw, William L.; Dlott, Dana D., E-mail: dlott@illinois.edu [School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2014-04-15

    We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s{sup ?1} impacts with transparent target materials. Laser-launching Al flyers 25–100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.

  8. Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry

    International Nuclear Information System (INIS)

    We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s?1 impacts with transparent target materials. Laser-launching Al flyers 25–100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns

  9. Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry

    Science.gov (United States)

    Curtis, Alexander D.; Banishev, Alexandr A.; Shaw, William L.; Dlott, Dana D.

    2014-04-01

    We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s-1 impacts with transparent target materials. Laser-launching Al flyers 25-100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.

  10. Laser-driven flyer plates for shock compression science: launch and target impact probed by photon Doppler velocimetry.

    Science.gov (United States)

    Curtis, Alexander D; Banishev, Alexandr A; Shaw, William L; Dlott, Dana D

    2014-04-01

    We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s(-1) impacts with transparent target materials. Laser-launching Al flyers 25-100 ?m thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns. PMID:24784627

  11. Microsurgical laser Doppler probe for simultaneous intraoperative monitoring of cochlear blood flow and electrocochleography from the round window

    Science.gov (United States)

    Abiy, Lidet; Telischi, Fred; Parel, Jean-Marie A.; Manns, Fabrice; Saettele, Ralph; Morawski, Krzysztof; Ozdamar, Ozcan; Borgos, John; Delgado, Rafael; Miskiel, Edward; Yavuz, Erdem

    2003-06-01

    The aim of this project is the development of a microsurgical laser Doppler (LD) probe that simultaneously monitors blood flow and Electrocochleography (ECochG) from the round window of the ear. The device will prevent neurosensory hearing loss during acoustic neuroma surgery by preventing damage to the internal auditory nerve and to the cochlear blood flow supply. A commercially available 0.5 mm diameter Laser-Doppler velocimetry probe (LaserFlo, Vasamedics) was modified to integrate an ECochG electrode. A tube for suction and irrigation was incorporated into a sheath of the probe shaft, to facilitate cleaning of the round window (RW) and allow drug delivery to the round window membrane. The prototype microprobe was calibrated on a single vessel model and tested in vivo in a rabbit model. Preliminary results indicate that the microprobe was able to measure changes in cochlear blood flow (CBF) and ECochG potentials from the round window of rabbits in vivo. The microprobe is suitable for monitoring cochlear blood flow and auditory cochlear potentials during human surgery.

  12. Continuous-scanning laser Doppler vibrometry: Extensions to arbitrary areas, multi-frequency and 3D capture

    International Nuclear Information System (INIS)

    To date, differing implementations of continuous scan laser Doppler vibrometry have been demonstrated by various academic institutions, but since the scan paths were defined using step or sine functions from function generators, the paths were typically limited to 1D line scans or 2D areas such as raster paths or Lissajous trajectories. The excitation was previously often limited to a single frequency due to the specific signal processing performed to convert the scan data into an ODS. In this paper, a configuration of continuous-scan laser Doppler vibrometry is demonstrated which permits scanning of arbitrary areas, with the benefit of allowing multi-frequency/broadband excitation. Various means of generating scan paths to inspect arbitrary areas are discussed and demonstrated. Further, full 3D vibration capture is demonstrated by the addition of a range-finding facility to the described configuration, and iteratively relocating a single scanning laser head. Here, the range-finding facility was provided by a Microsoft Kinect, an inexpensive piece of consumer electronics

  13. Continuous-scanning laser Doppler vibrometry: Extensions to arbitrary areas, multi-frequency and 3D capture

    Energy Technology Data Exchange (ETDEWEB)

    Weekes, B.; Ewins, D. [University of Bristol, Queen' s Building, University Walk, Bristol, BS8 1TR (United Kingdom); Acciavatti, F. [Universita' Politecnica Delle Marche, Via Brecce Bianche 12, 60131 Ancona (Italy)

    2014-05-27

    To date, differing implementations of continuous scan laser Doppler vibrometry have been demonstrated by various academic institutions, but since the scan paths were defined using step or sine functions from function generators, the paths were typically limited to 1D line scans or 2D areas such as raster paths or Lissajous trajectories. The excitation was previously often limited to a single frequency due to the specific signal processing performed to convert the scan data into an ODS. In this paper, a configuration of continuous-scan laser Doppler vibrometry is demonstrated which permits scanning of arbitrary areas, with the benefit of allowing multi-frequency/broadband excitation. Various means of generating scan paths to inspect arbitrary areas are discussed and demonstrated. Further, full 3D vibration capture is demonstrated by the addition of a range-finding facility to the described configuration, and iteratively relocating a single scanning laser head. Here, the range-finding facility was provided by a Microsoft Kinect, an inexpensive piece of consumer electronics.

  14. Repeatability of the evaluation of systemic microvascular endothelial function using laser doppler perfusion monitoring: clinical and statistical implications

    Scientific Electronic Library Online (English)

    Eduardo, Tibiriçá; Alessandra SM, Matheus; Bruno, Nunes; Sandro, Sperandei; Marilia B., Gomes.

    Full Text Available OBJECTIVE: An awareness of the repeatability of biological measures is required to properly design and calculate sample sizes for longitudinal interventional studies. We investigated the day-to-day repeatability of measures of systemic microvascular reactivity using laser Doppler perfusion monitorin [...] g. METHODS: We performed laser Doppler perfusion monitoring in combination with skin iontophoresis using acetylcholine and sodium nitroprusside as well as post-occlusive reactive and thermal hyperemia twice within two weeks. The repeatability was assessed by calculating the within-subject standard deviations, limits of agreement, typical errors and intra-class correlation coefficients between days 1 and 2. The ratio of the within-subject standard deviation to the mean values obtained on days 1 and 2 (within-subject standard deviation/GM) was used to determine the condition with the best repeatability. RESULTS: Twenty-four healthy subjects, aged 24.6 + 3.8 years, were recruited. The area under the curve of the vasodilatory response to post-occlusive reactivity showed marked variability (within-subject standard deviation/GM = 0.83), while the area under the curve for acetylcholine exhibited less variability (within-subject standard deviation/ GM = 0.52) and was comparable to the responses to sodium nitroprusside and thermal treatment (within-subject standard deviations/GM of 0.67 and 0.56, respectively). The area under the blood flow/time curve for vasodilation during acetylcholine administration required the smallest sample sizes, the area under the blood flow/time curve during post-occlusive reactivity required the largest sample sizes, and the area under the blood flow/time curves of vasodilation induced by sodium nitroprusside and thermal treatment required intermediate sizes. CONCLUSIONS: In view of the importance of random error related to the day-to-day repeatability of laser Doppler perfusion monitoring, we propose an original and robust statistical methodology for use in designing prospective clinical studies.

  15. Repeatability of the evaluation of systemic microvascular endothelial function using laser doppler perfusion monitoring: clinical and statistical implications

    Directory of Open Access Journals (Sweden)

    Eduardo Tibiriçá

    2011-01-01

    Full Text Available OBJECTIVE: An awareness of the repeatability of biological measures is required to properly design and calculate sample sizes for longitudinal interventional studies. We investigated the day-to-day repeatability of measures of systemic microvascular reactivity using laser Doppler perfusion monitoring. METHODS: We performed laser Doppler perfusion monitoring in combination with skin iontophoresis using acetylcholine and sodium nitroprusside as well as post-occlusive reactive and thermal hyperemia twice within two weeks. The repeatability was assessed by calculating the within-subject standard deviations, limits of agreement, typical errors and intra-class correlation coefficients between days 1 and 2. The ratio of the within-subject standard deviation to the mean values obtained on days 1 and 2 (within-subject standard deviation/GM was used to determine the condition with the best repeatability. RESULTS: Twenty-four healthy subjects, aged 24.6 + 3.8 years, were recruited. The area under the curve of the vasodilatory response to post-occlusive reactivity showed marked variability (within-subject standard deviation/GM = 0.83, while the area under the curve for acetylcholine exhibited less variability (within-subject standard deviation/ GM = 0.52 and was comparable to the responses to sodium nitroprusside and thermal treatment (within-subject standard deviations/GM of 0.67 and 0.56, respectively. The area under the blood flow/time curve for vasodilation during acetylcholine administration required the smallest sample sizes, the area under the blood flow/time curve during post-occlusive reactivity required the largest sample sizes, and the area under the blood flow/time curves of vasodilation induced by sodium nitroprusside and thermal treatment required intermediate sizes. CONCLUSIONS: In view of the importance of random error related to the day-to-day repeatability of laser Doppler perfusion monitoring, we propose an original and robust statistical methodology for use in designing prospective clinical studies.

  16. Using ordinal logistic regression to evaluate the performance of laser-Doppler predictions of burn-healing time

    OpenAIRE

    Pape Sarah A; Monstrey Stan; Hoeksema Henk; Jeng James C; Weinand Christian; Baker Rose D; Spence Robert; Wilson David

    2009-01-01

    Abstract Background Laser-Doppler imaging (LDI) of cutaneous blood flow is beginning to be used by burn surgeons to predict the healing time of burn wounds; predicted healing time is used to determine wound treatment as either dressings or surgery. In this paper, we do a statistical analysis of the performance of the technique. Methods We used data from a study carried out by five burn centers: LDI was done once between days 2 to 5 post burn, and healing was assessed at both 14 days and 21 da...

  17. A laser-lock concept to reach cm s-1-precision in Doppler experiments with Fabry-Pérot wavelength calibrators

    Science.gov (United States)

    Reiners, A.; Banyal, R. K.; Ulbrich, R. G.

    2014-09-01

    State-of-the-art Doppler experiments require wavelength calibration with precision at the cm s-1 level. A low-finesse Fabry-Pérot interferometer (FPI) can provide a wavelength comb with a very large bandwidth as required for astronomical experiments, but unavoidable spectral drifts are difficult to control. Instead of actively controlling the FPI cavity, we propose to passively stabilize the interferometer and track the time-dependent cavity length drift externally using the 87Rb D2 atomic line. A dual-finesse cavity allows drift tracking during observation. In the low-finesse spectral range, the cavity provides a comb transmission spectrum tailored to the astronomical spectrograph. The drift of the cavity length is monitored in the high-finesse range relative to an external standard: a single narrow transmission peak is locked to an external cavity diode laser and compared to an atomic frequency from a Doppler-free transition. Following standard locking schemes, tracking at sub-mm s-1 precision can be achieved. This is several orders of magnitude better than currently planned high-precision Doppler experiments, and it allows freedom for relaxed designs including the use of a single-finesse interferometer under certain conditions. All components for the proposed setup are readily available, rendering this approach particularly interesting for upcoming Doppler experiments. We also show that the large number of interference modes used in an astronomical FPI allows us to unambiguously identify the interference mode of each FPI transmission peak defining its absolute wavelength solution. The accuracy reached in each resonance with the laser concept is then defined by the cavity length that is determined from the one locked peak and by the group velocity dispersion. The latter can vary by several 100 m s-1 over the relevant frequency range and severely limits the accuracy of individual peak locations, although their interference modes are known. A potential way to determine the absolute peak positions is to externally measure the frequency of each individual peak with a laser frequency comb (LFC). Thus, the concept of laser-locked FPIs may be useful for applying the absolute accuracy of an LFC to astronomical spectrographs without the need for an LFC at the observatory.

  18. Flow investigation by laser-Doppler velocimeter applied to vertical 180-degree bend of rectangular pipes, (1)

    International Nuclear Information System (INIS)

    When water flows around 1800-bend, centrifugal force acts on the flow resulting in secondary currents within the bend. This paper describes the results of an investigation of the spiral motion around the bend using a laser-Doppler velocimeter. Flow measurement in presence of swirl and manifestation of its velocity-vectors are difficult. This difficulty was solved by using a process such alike tomography and velocity-vactors could be represented stereo-graphically. Furthermore, an investigation was made of the occurrence of Dean's instability by measuring pressure distribution in the channel. This may be found to appear at lower Dean number in vertical channel than horizontal. (author)

  19. Non-mechanical scanning laser Doppler velocimetry with sensitivity to direction of transverse velocity component using optical serrodyne frequency shifting

    Science.gov (United States)

    Maru, Koichi; Watanabe, Kento

    2014-05-01

    This paper proposes a non-mechanical axial scanning laser Doppler velocimeter (LDV) with sensitivity to the direction of the transverse velocity component using optical serrodyne frequency shifting. Serrodyne modulation via the electro-optic effect of a LiNbO3 (LN) phase shifter is employed to discriminate the direction of the transverse velocity component. The measurement position is scanned without any moving mechanism in the probe by changing the wavelength of the light input to the probe. The experimental results using a sensor probe setup indicate that both the scan of the measurement position and the introduction of directional sensitivity are successfully demonstrated.

  20. Effect of clenbuterol on cardiopulmonary parameters and intramuscular blood flow by laser Doppler flowmetry in anesthetized ponies

    Science.gov (United States)

    Lee, Yong H.; Clarke, Kathleen W.; Alibhai, Hatim I. K.

    1994-09-01

    The cardiopulmonary affects and the affects on muscular microperfusion of the beta adrenergic agonist, clenbuterol (0.8 mcg/kg intravenously), were investigated in dorsally recumbent anesthetized ponies. Muscle microcirculation was measured by laser Doppler flowmetry, utilizing fine optical fiber probes. Other measurements included heart rate, cardiac output, arterial blood pressure, and arterial blood gas tensions. Clenbuterol injection caused a regular, but transitory rise in muscle microcirculation, an increase in heart rate, and cardiac output and a decrease in mean arterial blood pressure. Clenbuterol did appear to prevent the continuing fall in arterial blood oxygen tensions seen in the treatment groups, but had only minimal affects in reversing the hypoxia already present.

  1. Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry

    Science.gov (United States)

    Crua, Cyril; Heikal, Morgan R.

    2014-12-01

    Hydrodynamic turbulence and cavitation are known to play a significant role in high-pressure atomizers, but the small geometries and extreme operating conditions hinder the understanding of the flow’s characteristics. Diesel internal flow experiments are generally conducted using x-ray techniques or on transparent, and often enlarged, nozzles with different orifice geometries and surface roughness to those found in production injectors. In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a 3D laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working fluid, or limiting the fuel injection pressure. The vibrometer, which uses the Doppler effect to measure the velocity of a vibrating object, was used to scan injector nozzle tips during the injection event. The data were processed using a discrete Fourier transform to provide time-resolved spectra for valve-closed-orifice, minisac and microsac nozzle geometries, and injection pressures ranging from 60 to 160?MPa, hence offering unprecedented insight into cyclic cavitation and internal mechanical dynamic processes. A peak was consistently found in the spectrograms between 6 and 7.5?kHz for all nozzles and injection pressures. Further evidence of a similar spectral peak was obtained from the fuel pressure transducer and a needle lift sensor mounted into the injector body. Evidence of propagation of the nozzle oscillations to the liquid sprays was obtained by recording high-speed videos of the near-nozzle diesel jet, and computing the fast Fourier transform for a number of pixel locations at the interface of the jets. This 6–7.5?kHz frequency peak is proposed to be the natural frequency for the injector’s main internal fuel line. Other spectral peaks were found between 35 and 45?kHz for certain nozzle geometries, suggesting that these particular frequencies may be linked to nozzle dependent cavitation phenomena.

  2. Decoding carotid pressure waveforms recorded by laser Doppler vibrometry: Effects of rebreathing

    Science.gov (United States)

    Casaccia, Sara; Sirevaag, Erik J.; Richter, Edward; O'Sullivan, Joseph A.; Scalise, Lorenzo; Rohrbaugh, John W.

    2014-05-01

    The principal goal of this study was to assess the capability of the laser Doppler vibrometry (LDV) method for assessing cardiovascular activity. A rebreathing task was used to provoke changes within individuals in cardiac and vascular performance. The rebreathing task is known to produce multiple effects, associated with changes in autonomic drive as well as alterations in blood gases. The rise in CO2 (hypercapnia), in particular, produces changes in the cerebral and systemic circulation. The results from a rebreathing task (involving rebreathing the same air in a rubber bag) are presented for 35 individuals. The LDV pulse was measured from a site overlying the carotid artery. For comparison and validation purposes, several conventional measures of cardiovascular function were also obtained, with an emphasis on the electrocardiogram (ECG), continuous blood pressure (BP) from the radial artery, and measures of myocardial performance using impedance cardiography (ICG). During periods of active rebreathing, ventilation increased. The conventional cardiovascular effects included increased mean arterial BP and systemic vascular resistance, and decreased cardiac stroke volume (SV) and pulse transit time (PTT). These effects were consistent with a pattern of ?-adrenergic stimulation. During the immediate post-rebreathing segments, in contrast, mean BP was largely unaffected but pulse BP increased, as did PTT and SV, whereas systemic vascular resistance decreased-a pattern consistent with ?-adrenergic effects in combination with the direct effects of hypercapnia on the vascular system. Measures of cardiovascular activity derived from the LDV pulse velocity and displacement waveforms revealed patterns of changes that mirrored the results obtained using conventional measures. In particular, the ratio of the maximum early peak in the LDV velocity pulse to the maximum amplitude of the LDV displacement pulse (in an early systolic interval) closely mirrored the conventional SV effects. Additionally, changes in an augmentation ratio (computed as the maximum amplitude of the LDV displacement pulse during systole / amplitude at the end of the incident wave) were very similar to changes in systemic vascular resistance. Heart rates measured from the ECG and LDV were nearly identical. These preliminary results suggest that measures derived using the non-contact LDV technique can provide surrogate measures for those obtained using impedance cardiography.

  3. Laser Doppler vibrometry on rotating structures in coast-down: resonance frequencies and operational deflection shape characterization

    International Nuclear Information System (INIS)

    In rotating machinery, variations of modal parameters with rotation speed may be extremely important in particular for very light and undamped structures, such as helicopter rotors or wind turbines. The natural frequency dependence on rotation speed is conventionally measured by varying the rotor velocity and plotting natural frequencies versus speed in the so-called Campbell diagram. However, this kind of analysis does not give any information about the vibration spatial distribution i.e. the mode shape variation with the rotation speed must be investigated with dedicated procedures. In several cases it is not possible to fully control the rotating speed of the machine and only coast-down tests can be performed. Due to the reduced inertia of rotors, the coast-down process is usually an abrupt transient and therefore an experimental technique, able to determine operational deflection shapes (ODSs) in short time, with high spatial density and accuracy, appears very promising. Moreover coast-down processes are very difficult to control, causing unsteady vibrations. Hence, a very efficient approach for the rotation control and synchronous acquisition must be developed. In this paper a continuous scanning system able to measure ODSs and natural frequencies excited during rotor coast-down is shown. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the rotor surface, in order to measure the ODS, and to follow the rotation of the rotor itself even in coast-down. With a single measurement the ODSs can be recovered from the LDV output time history in short time and with huge data saving. This technique has been tested on a laboratory test bench, i.e. a rotating two-blade fan, and compared with a series of non-contact approaches based on LDV: - traditional experimental modal analysis (EMA) results obtained under non-rotating conditions by measuring on a sequence of points on the blade surface excited by an impact hammer,; - continuous scanning LDV measuring the ODS of the structure excited by an impact hammer modulating the laser output,; - tracking laser Doppler vibrometry (TLDV) operating at different rotation speeds under stationary conditions,; - tracking continuous scanning laser Doppler vibrometry (TCSLDV) operating at different rotation speeds under stationary conditions. EMA and TLDV have been performed over the same grid of points sufficiently dense to have ODSs with adequate spatial resolution, it requiring long measurement time. The application of different techniques allowed us to completely characterize the tested bladed rotor and to validate the continuous scanning application to transient rotator processes

  4. Laser Doppler vibrometry on rotating structures in coast-down: resonance frequencies and operational deflection shape characterization

    Science.gov (United States)

    Martarelli, M.; Castellini, P.; Santolini, C.; Tomasini, E. P.

    2011-11-01

    In rotating machinery, variations of modal parameters with rotation speed may be extremely important in particular for very light and undamped structures, such as helicopter rotors or wind turbines. The natural frequency dependence on rotation speed is conventionally measured by varying the rotor velocity and plotting natural frequencies versus speed in the so-called Campbell diagram. However, this kind of analysis does not give any information about the vibration spatial distribution i.e. the mode shape variation with the rotation speed must be investigated with dedicated procedures. In several cases it is not possible to fully control the rotating speed of the machine and only coast-down tests can be performed. Due to the reduced inertia of rotors, the coast-down process is usually an abrupt transient and therefore an experimental technique, able to determine operational deflection shapes (ODSs) in short time, with high spatial density and accuracy, appears very promising. Moreover coast-down processes are very difficult to control, causing unsteady vibrations. Hence, a very efficient approach for the rotation control and synchronous acquisition must be developed. In this paper a continuous scanning system able to measure ODSs and natural frequencies excited during rotor coast-down is shown. The method is based on a laser Doppler vibrometer (LDV) whose laser beam is driven to scan continuously over the rotor surface, in order to measure the ODS, and to follow the rotation of the rotor itself even in coast-down. With a single measurement the ODSs can be recovered from the LDV output time history in short time and with huge data saving. This technique has been tested on a laboratory test bench, i.e. a rotating two-blade fan, and compared with a series of non-contact approaches based on LDV: traditional experimental modal analysis (EMA) results obtained under non-rotating conditions by measuring on a sequence of points on the blade surface excited by an impact hammer, continuous scanning LDV measuring the ODS of the structure excited by an impact hammer modulating the laser output, tracking laser Doppler vibrometry (TLDV) operating at different rotation speeds under stationary conditions, tracking continuous scanning laser Doppler vibrometry (TCSLDV) operating at different rotation speeds under stationary conditions. EMA and TLDV have been performed over the same grid of points sufficiently dense to have ODSs with adequate spatial resolution, it requiring long measurement time. The application of different techniques allowed us to completely characterize the tested bladed rotor and to validate the continuous scanning application to transient rotator processes.

  5. Laser Doppler cross-sectional velocity distribution measurement combining 16-channel spatial encoding and non-mechanical scanning

    Science.gov (United States)

    Maru, Koichi

    2015-08-01

    This paper presents a differential laser Doppler velocimeter (LDV) for measuring the velocity distribution on a two-dimensional cross section. The author has proposed the LDV that combines non-mechanical scanning and simultaneous multipoint measurement using spatial encoding. In this paper, this method is expanded to a 16-channel system that facilitates more dense two-dimensional cross-sectional velocity distribution measurements. The spatially encoded measurement points aligned in the transverse direction are generated and scanned in the axial direction in a non-mechanical manner using diffraction gratings and a tunable laser. Multichannel serrodyne frequency shifting using a LiNbO3 phase-shifter array is used to generate spatially encoded points with a simple structure. An asymmetrical push-pull configuration is introduced to increase the number of the spatially encoded points. The experimental results indicate that the two-dimensional velocity distribution was successfully measured by the proposed configuration.

  6. Scanning Laser Doppler Vibrometer Measurements Inside Helicopter Cabins in Running Conditions: Problems and Mock-up Testing

    International Nuclear Information System (INIS)

    The present work deals with the analysis of problems and potentials of laser vibrometer measurements inside helicopter cabins in running conditions. The paper describes the results of a systematic measurement campaign performed on an Agusta A109MKII mock-up. The aim is to evaluate the applicability of Scanning Laser Doppler Vibrometer (SLDV) for tests in simulated flying conditions and to understand how performances of the technique are affected when the laser head is placed inside the cabin, thus being subjected to interfering inputs. Firstly a brief description of the performed test cases and the used measuring set-ups are given. Comparative tests between SLDV and accelerometers are presented, analyzing the achievable performances for the specific application. Results obtained measuring with SLDV placed inside the helicopter cabin during operative excitation conditions are compared with those performed with the laser lying outside the mock-up, these last being considered as 'reference measurements'. Finally, in order to give an estimate of the uncertainty level on measured signals, a study linking the admitted percentage of noise content on vibrometer signals due to laser head vibration levels will be introduced.

  7. Theoretical and experimental study of turbine flowmeters

    OpenAIRE

    Xu, Y. F.

    1992-01-01

    A vortex shedding model is developed to predict the flow fields around turbine flowmeter blades. This model is used to simulate the flow separation and reattachment in the leading edge areas and the wake flows of the blades. Lewis's inverse blade design method is developed and quite successfully applied to simulate the displacement effect of the separation bubbles in the leading edge areas. A new method is introduced to apply the Kutta condition in unsteady flows around t...

  8. Laser Radar Range-Doppler Imaging and Simulation on High-speed Target

    International Nuclear Information System (INIS)

    On the basic of the representation of the principle of Doppler imaging, an echo model of high-speed target illuminated by broadband linear frequency modulated (LFM) signal was established in this paper. For high-speed target, because of its nonlinear echo phase and time-varying Doppler frequency shift, the Doppler spectrum of the target acquired by the traditional Fourier method was ambiguous, and the same in the radar images of the target. Therefore, an adaptive Wigner-Ville time-frequency analysis method was presented in the paper, that is, the local fuzzy function could be obtained by applying the two-dimensional adding Window Fourier Transform to signal's Wigner-Ville distribution, which made the kernel function, not only be adaptive to time, but also to the frequency. Finally, the simulation results show that the method has a good time-frequency concentration, and effectively control the cross-term interference.

  9. Correlation analysis of laser Doppler flowmetry signals: a potential non-invasive tool to assess microcirculatory changes in diabetes mellitus.

    Science.gov (United States)

    Lal, Cerine; Unni, Sujatha Narayanan

    2015-06-01

    Measurement and analysis of microcirculation is vital in assessing local and systemic tissue health. Changes in microvascular perfusion if detected can provide information on the development of various related diseases. Laser Doppler blood flowmetry (LDF) provides a non-invasive real-time measurement of cutaneous blood perfusion. LDF signals possess fractal nature that represents the correlation in the successive signal elements. Changes in the correlation of flow and its associated parameters could be used as a tool in differentiating the ailments at different stages or assessing the treatment effectiveness of a particular ailment. Spectral domain analysis of LDF signals reveals five characteristic frequency peaks corresponding to local and central regulatory mechanisms of the human body, namely metabolic, neurogenic, myogenic, respiration, and heart rate. This paper investigates the changes in the fractal nature and constituent frequency bands of laser Doppler signals in diabetic and healthy control subjects acquired from the glabrous skin of the foot so as to provide an assessment of microcirculatory dynamics. As a pilot study, it was attempted on a set of healthy control and diabetic volunteers, and the obtained results indicate that fractal nature of LDF signals is less in diabetic subjects compared to the healthy control. The wavelet analysis carried out on the set of signals reveals the dynamics of blood flow which may have led to the difference in correlation results. PMID:25752769

  10. Laser Doppler visualisation of the fields of three-dimensional velocity vectors with the help of a minimal number of CCD cameras

    International Nuclear Information System (INIS)

    We discuss the possibility of laser Doppler visualisation and measurement of the field of three-dimensional velocity vectors by suppressing the multiparticle scattering influence on the measurement results, when using one CCD camera. The coordinate measuring basis is formed due to switching of the directions and the frequency of spatially combined laser sheets, the frequency being synchronised with the CCD-camera operation. The field of the velocity vectors without the contribution from the multiparticle scattering is produced from the linear combinations of normalised laser sheet images detected with a CCD camera in a frequency-demodulated scattered light. The method can find applications not only in laser diagnostics of gas and condensed media but also in the Doppler spectroscopy of light fields scattered by multiparticle dynamic structures. (laser applications and other topics in quantum electronics)

  11. A study of air-coupled ultrasonic flowmeter

    International Nuclear Information System (INIS)

    A non-contact flowmeter employing air-coupled ultrasonic is developed in this study. Flow rate of feed water and cooling water for the condenser are monitored to control the thermal output of the nuclear reactor. Ultrasonic flowmeter has an advantage in its accuracy compared with differential pressure flowmeter and venturi flowmeter. However, the performance of sensors decreases in high-temperature conditions such as nuclear power plants and thermal power plants, and measuring accuracy declines because a sensor lose a piezoelectricity over its Curie point. (author)

  12. Doppler diagnostics of nonstationary mass removal upon laser ablation of biotissues

    International Nuclear Information System (INIS)

    The possibilities of the use of autodyne detection of backscattered radiation for studies of nonstationary mass transfer upon ablation of biotissues by pulses from a CO2 laser are demonstrated. It is shown that the differences in the character of the laser-induced mass removal are caused by structural features of biotissues. (interaction of laser radiation with matter. laser plasma)

  13. Performance comparison of an all-fiber-based laser Doppler vibrometer for remote acoustical signal detection using short and long coherence length lasers.

    Science.gov (United States)

    Li, Rui; Madampoulos, Nicholas; Zhu, Zhigang; Xie, Liangping

    2012-07-20

    All-fiber laser Doppler vibrometer systems have great potential in the application of remote acoustic detection. However, due to the requirement for a long operating distance, a long coherence length laser is required, which can drive the system cost high. In this paper, a system using a short coherence length laser is proposed and demonstrated. Experimental analysis indicates that the multi-longitudinal modes of the laser cause detection noise and that the unequal length between two paths (local oscillator path and transmission path) increases the intensity and the frequency components of the noise. In order to reduce the noise, the optical length of the two paths needs to be balanced, within the coherence length of the source. We demonstrate that adopting a tunable optical delay to compensate the unequal length significantly reduces the noise. In a comparison of the detection results by using a short coherence laser and a long coherence laser, our developed system gives a good performance on the acoustic signal detection from three meters away. PMID:22858939

  14. Implementation and calibration of a laser Doppler velocimeter in order to measure liquids velocity

    Directory of Open Access Journals (Sweden)

    C.F. Ord\\u00F3\\u00F1ez Urbano

    2013-01-01

    Full Text Available Un sistema ? optico se aplic ? o y calibro con la t ? ecnica de l ? aser Doppler de diagnostico diferencial o configuraci ? on de doble haz, con detecci ? on hacia adelante, con el fin de medir un componente del vector de velocidad en l ? ?quidos transl ? ucidos. Este documento describe dos etapas, la primera es la calibraci ? on del veloc ? ?metro Doppler l ? aser a trav ? es de un objetivo rotatorio, y un acoplador ? optico que permiten verificar que las frecuencias que son detectados por el sistema ? optico, corresponden a las velocidades de rotaci ? on de dicho dispositivo. La segunda etapa es la medici ? on de la velocidad del l ? ?quido en un sistema de flujo estrecha que permite obtener r ? egimen de flujo laminar (bajo n ? umero de Reynolds, y se determin ? o la velocidad de componente ortogonal al patr ? on de interferencia franjas. Esta velocidad se calcula mediante la detecci ? on de la frecuencia de cambio en la intensidad que sufre la periferia (frecuencia Doppler donde las part ? ?culas artificiales o naturales (siembra sumergidos en el fluido a trav ? es de ellos. La radiaci ? on de la luz dispersa por la siembra conten ? ?a la se ? nal Doppler que se recoge con un fotodetector y se muestran en una computadora como un espectro de frecuencia.

  15. Using ordinal logistic regression to evaluate the performance of laser-Doppler predictions of burn-healing time

    Directory of Open Access Journals (Sweden)

    Pape Sarah A

    2009-02-01

    Full Text Available Abstract Background Laser-Doppler imaging (LDI of cutaneous blood flow is beginning to be used by burn surgeons to predict the healing time of burn wounds; predicted healing time is used to determine wound treatment as either dressings or surgery. In this paper, we do a statistical analysis of the performance of the technique. Methods We used data from a study carried out by five burn centers: LDI was done once between days 2 to 5 post burn, and healing was assessed at both 14 days and 21 days post burn. Random-effects ordinal logistic regression and other models such as the continuation ratio model were used to model healing-time as a function of the LDI data, and of demographic and wound history variables. Statistical methods were also used to study the false-color palette, which enables the laser-Doppler imager to be used by clinicians as a decision-support tool. Results Overall performance is that diagnoses are over 90% correct. Related questions addressed were what was the best blood flow summary statistic and whether, given the blood flow measurements, demographic and observational variables had any additional predictive power (age, sex, race, % total body surface area burned (%TBSA, site and cause of burn, day of LDI scan, burn center. It was found that mean laser-Doppler flux over a wound area was the best statistic, and that, given the same mean flux, women recover slightly more slowly than men. Further, the likely degradation in predictive performance on moving to a patient group with larger %TBSA than those in the data sample was studied, and shown to be small. Conclusion Modeling healing time is a complex statistical problem, with random effects due to multiple burn areas per individual, and censoring caused by patients missing hospital visits and undergoing surgery. This analysis applies state-of-the art statistical methods such as the bootstrap and permutation tests to a medical problem of topical interest. New medical findings are that age and %TBSA are not important predictors of healing time when the LDI results are known, whereas gender does influence recovery time, even when blood flow is controlled for. The conclusion regarding the palette is that an optimum three-color palette can be chosen 'automatically', but the optimum choice of a 5-color palette cannot be made solely by optimizing the percentage of correct diagnoses.

  16. Glucagon-like peptide-2 stimulates mucosal microcirculation measured by laser Doppler flowmetry in end-jejunostomy short bowel syndrome patients

    DEFF Research Database (Denmark)

    HØyerup, P; Hellström, P M

    2013-01-01

    In animal and human studies glucagon-like peptide-2 (GLP-2) has been shown to increase blood flow in the superior mesenteric artery and the portal vein. This study describes the effect of GLP-2 measured directly on the intestinal mucosal blood flow by laser Doppler flowmetry (LDF) in end-jejunostomy short bowel syndrome (SBS) patients.

  17. Slug flow measurement using a current-sensing electromagnetic flowmeter

    International Nuclear Information System (INIS)

    In order to investigate the characteristics of two-phase slug flow, a current-sensing electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. Theory of a current-sensing electromagnetic flowmeter with high temporal resolution was also developed. A flow pattern coefficient and a localization parameter were introduced for developing two-phase flow. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under singlephase flow was ±2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble

  18. Transient thermo-mechanical analysis of smart power switches by a laser Doppler vibrometer and numerical simulations

    International Nuclear Information System (INIS)

    In the paper, application of a laser Doppler vibrometry (LDV) technique for the surface thermal expansion measurement of the semiconductor power devices is presented. As the LDV method can provide a signal directly proportional to the velocity of the surface deformation even for step inputs, the study of a thermal deformation transient process has been accomplished. The time dependence of surface out-of-plane displacement was obtained by integration of the measured velocity time dependences for several discrete surface points. The LDV results of transient performance were confronted with those simulated by the finite-element method. Such a numerical/experimental analysis has been carried out on a composite multilayer structure of a smart power switch device operating under short circuit conditions. A good quantitative coincidence was achieved between thermo-mechanical modelling and LDV measurements

  19. Performance of eddy-viscosity turbulence models for predicting swirling pipe-flow: Simulations and laser-Doppler velocimetry

    CERN Document Server

    Díaz, Diego del Olmo

    2015-01-01

    We use laser-Doppler velocimetry (LDV) experiments and Reynolds-averaged Navier--Stokes (RANS) simulations to study the characteristic flow patterns downstream of a standardized clockwise swirl disturbance generator. After quantifying the impact of the mesh size, we evaluate the potential of various eddy-viscosity turbulence models in providing reasonable approximations with respect to the experimental reference. Our results suggest that models from the $k$-$\\epsilon$ family are more accurate in predicting swirling flows than models from the $k$-$\\omega$ family. For sufficiently resolved meshes, the realizable $k$-$\\epsilon$ model provides the most accurate approximation of the velocity magnitudes, although it fails to capture small-scale flow structures which are accurately predicted by the standard $k$-$\\epsilon$ model and the RNG $k$-$\\epsilon$ model. Throughout the article, we highlight practical guidance for the choice of RANS turbulence models for swirling flow.

  20. An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions

    Science.gov (United States)

    Chriss, R. M.; Hingst, W. R.; Strazisar, A. J.; Keith, T. G., Jr.

    1989-01-01

    Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case.

  1. Developing dual-beam laser Doppler interferometry system for opto-piezoelectric materials based ultrasonic parking sensors and optofluidics sensors

    Science.gov (United States)

    Lai, Po-Cheng; Lee, Chih-Kung

    2014-03-01

    Adopting opto-piezoelectric materials, which utilized optical illumination pattern to effect the spatial force distribution induced by piezoelectric materials, to ultrasonic parking sensors and optofluidic chips represent a new research direction in industrial sub-system development. To accommodate performance requirements include wide bandwidth, ultrahigh precision, non-contact measurement mode, linear and angular measurement, etc. associated with the evaluation of the above-mentioned systems, a laser Doppler interferometer was implemented to facilitate the system development. The completely orthogonal alignment design configuration, system performance verified, signal processing algorithms developed as well as the experimental results obtained were all discussed in this paper. Emphasis is on the experimental data obtained from the interferometer and the design changes developed based on the metrology outcome. The system performance improvements induced by the experimental verification achieved by the interferometer were discussed in detail.

  2. Laser Doppler Velocimetry for Joint Measurements of Acoustic and Mean Flow Velocities : LMS-based Algorithm and CRB Calculation

    CERN Document Server

    Simon, Laurent; Degroot, Anne; Lionet, Louis; 10.1109/TIM.2008.917670

    2009-01-01

    This paper presents a least mean square (LMS) algorithm for the joint estimation of acoustic and mean flow velocities from laser doppler velocimetry (LDV) measurements. The usual algorithms used for measuring with LDV purely acoustic velocity or mean flow velocity may not be used when the acoustic field is disturbed by a mean flow component. The LMS-based algorithm allows accurate estimations of both acoustic and mean flow velocities. The Cram\\'er-Rao bound (CRB) of the associated problem is determined. The variance of the estimators of both acoustic and mean flow velocities is also given. Simulation results of this algorithm are compared with the CRB and the comparison leads to validate this estimator.

  3. Electro-kinetics of charged-sphere suspensions explored by integral low-angle super-heterodyne laser Doppler velocimetry

    International Nuclear Information System (INIS)

    We investigated the flow behaviour of colloidal charged-sphere suspensions using a newly designed integral low-angle super-heterodyne laser Doppler velocimetry instrument, which combines the advantages of several previous approaches. Sample conditions ranged from strong electrostatic interactions with pronounced short-range order to individual particles with no spatial correlations. The obtained power spectra correspond to diffusion broadened velocity distributions across the complete sample cross section. The excellent performance of the instrument is highlighted in detail by the example of electro-kinetic flow of suspensions in a closed cell of a rectangular cross section. We demonstrate the excellent performance of our approach with the example of electro-phoretic-electro-osmotic experiments, showing that a comprehensive flow characterization becomes possible by analysing the measured electro-kinetic mobilities, the flow-profile, an effective diffusion coefficient and the integrated scattering density. We briefly discuss present limitations, possible extensions and interesting applications in other fields.

  4. Photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid

    International Nuclear Information System (INIS)

    The authors present an optically based method combining photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid. The frequency spectrum of a silicon cantilever measured in water over frequencies ranging up to 10 MHz shows that the method allows us to excite and detect higher modes, from fundamental to fifth flexural, without enhancing spurious resonances. By reducing the tip oscillation amplitude using higher modes, the average tip-sample force gradient due to chemical bonds is effectively increased to achieve high-spatial-resolution imaging in liquid. The method's performance is demonstrated by atomic resolution imaging of a mica surface in water obtained using the second flexural mode with a small tip amplitude of 99 pm; individual atoms on the surface with small height differences of up to 60 pm are clearly resolved.

  5. Investigations of slip in capillary flow by laser-Doppler velocimetry and their relations to melt fracture

    Science.gov (United States)

    Münstedt, Helmut

    2015-04-01

    Flow profiles within a slit capillary are measured by laser-Doppler velocimetry. They allow the direct determination of the slip velocity at the wall. It is demonstrated that the flow profile of the melt of a high density polyethylene (HDPE) already shows slip components at small shear rates. At high shear rates the slip is dominant and a plug flow is found. Furthermore, it is shown that the surface irregularity called "shark skin" is generated at the slit exit by the stretching of surface layers at pronounced elongational rates. These elongational rates are due to the differences between the flow velocities at the wall of the slit and those of the extruded strand. It is shown how "shark skin" may be avoided when the elongational rate is reduced by introducing slip of the melt in the slit using special additives.

  6. Laser Doppler line scanner for monitoring skin perfusion changes of port wine stains during vascular-targeted photodynamic therapy

    Science.gov (United States)

    Chen, Defu; Ren, Jie; Wang, Ying; Gu, Ying

    2014-11-01

    Vascular-targeted photodynamic therapy (V-PDT) is known to be an effective therapeutic modality for the treatment of port wine stains (PWS). Monitoring the PWS microvascular response to the V-PDT is crucial for improving the effectiveness of PWS treatment. The objective of this study was to use laser Doppler technique to directly assess the skin perfusion in PWS before and during V-PDT. In this study, 30 patients with PWS were treated with V-PDT. A commercially laser Doppler line scanner (LDLS) was used to record the skin perfusion of PWS immediately before; and at 1, 3, 5, 7, 10, 15 and 20 minutes during V-PDT treatment. Our results showed that there was substantial inter- and intra-patient perfusion heterogeneity in PWS lesion. Before V-PDT, the comparison of skin perfusion in PWS and contralateral healthy control normal skin indicated that PWS skin perfusion could be larger than, or occasionally equivalent to, that of control normal skin. During V-PDT, the skin perfusion in PWS significantly increased after the initiation of V-PDT treatment, then reached a peak within 10 minutes, followed by a slowly decrease to a relatively lower level. Furthermore, the time for reaching peak and the subsequent magnitude of decrease in skin perfusion varied with different patients, as well as different PWS lesion locations. In conclusion, the LDLS system is capable of assessing skin perfusion changes in PWS during V-PDT, and has potential for elucidating the mechanisms of PWS microvascular response to V-PDT.

  7. Time-resolved and doppler-reduced laser spectroscopy on atoms

    International Nuclear Information System (INIS)

    Radiative lifetimes have been studied in neutral boron, carbon, silicon and strontium, in singly ionized gadolinium and tantalum and in molecular carbon monoxide and C2. The time-resolved techniques were based either on pulsed lasers or pulse-modulated CW lasers. Several techniques have been utilized for the production of free atoms and ions such as evaporation into an atomic beam, sputtering in hollow cathodes and laser-produced plasmas. Hyperfine interactions in boron, copper and strontium have been examined using quantum beat spectroscopy, saturation spectroscopy and collimated atomic beam spectroscopy. Measurement techniques based on effusive hollow cathodes as well as laser produced plasmas in atomic physics have been developed. Investigations on laser produced plasmas using two colour beam deflection tomography for determination of electron densities have been performed. Finally, new possibilities for view-time-expansion in light-in-flight holography using mode-locked CW lasers have been demonstrated. (au)

  8. Microfluidic flowmeter based on micro "hot-wire" sandwiched Fabry-Perot interferometer.

    Science.gov (United States)

    Li, Ying; Yan, Guofeng; Zhang, Liang; He, Sailing

    2015-04-01

    We present a compact microfluidic flowmeter based on Fabry-Perot interferometer (FPI). The FPI was composed by a pair of fiber Bragg grating reflectors and a micro Co2+-doped optical fiber cavity, acting as a "hot-wire" sensor. Microfluidic channels made from commercial silica capillaries were integrated with the FPIs on a chip to realize flow-rate sensing system. By utilizing a tunable pump laser with wavelength of 1480 nm, the proposed flowmeter was experimentally demonstrated. The flow rate of the liquid sample is determined by the induced resonance wavelength shift of the FPI. The effect of the pump power, microfluidic channel scale and temperature on the performance of our flowmeter was investigated. The dynamic response was also measured under different flow-rate conditions. The experimental results achieve a sensitivity of 70 pm/(?L/s), a dynamic range up to 1.1 ?L/s and response time in the level of seconds, with a spatial resolution ~200 ?m. Such good performance renders the sensor a promising supplementary component in microfluidic biochemical sensing system. Furthermore, simulation modal was built up to analyze the heat distribution of the "hot-wire" cavity and optimize the FPI structure as well. PMID:25968776

  9. Doppler-free intermodulated fluorescence spectroscopy of 4He 23P-31,3D transitions at 588 nm with a 1-W compact laser system

    Science.gov (United States)

    Luo, Pei-Ling; Hu, Jinmeng; Feng, Yan; Wang, Li-Bang; Shy, Jow-Tsong

    2015-05-01

    We have demonstrated Doppler-free intermodulated fluorescence spectroscopy of helium 23P-31,3D transitions in an rf-discharged sealed-off cell using a compact laser system at 588 nm. An external cavity diode laser at 1176 nm was constructed to seed a Raman fiber amplifier. Laser power of more than 1 W at 588 nm was produced by frequency doubling of the fiber amplifier output using a MgO:PPLN crystal. A doubling efficiency of 23 % was achieved. The power-dependent spectra of the 23P-33D transitions were investigated. Furthermore, the Doppler-free spectrum of the spin-forbidden 23P-31D transitions was observed for the first time. Our results are crucial toward precision test of QED atomic calculations, especially for improving the determination of the helium 31D-33D separation.

  10. Measurements of ultrasonic waves by means of laser Doppler velocimeter and an experimental study of elastic wave propagation in inhomogeneous media; Laser doppler sokudokei ni yoru choonpa keisoku to ganseki wo mochiita fukinshitsu baishitsu no hado denpa model jikken

    Energy Technology Data Exchange (ETDEWEB)

    Nishizawa, O.; Sato, T. [Geological Survey of Japan, Tsukuba (Japan); Lei, X. [Dia Consultants Company, Tokyo (Japan)

    1996-05-01

    In the study of seismic wave propagation, a model experimenting technique has been developed using a laser Doppler velocimeter (LDV) as the sensor. This technique, not dependent on conventional piezoelectric devices, only irradiates the specimen with laser to measure the velocity amplitude on the target surface, eliminating the need for close contact between the specimen and sensor. In the experiment, elastic penetration waves with their noise levels approximately 0.05mm/s were observed upon application of vibration of 10{sup 6}-10{sup 5}Hz. The specimen was stainless steel or rock, and waveforms caught by the LDV and piezoelectric device were compared. As the result, it was found that the LDV is a powerful tool for effectively explaining elastic wave propagation in inhomogeneous media. The piezoelectric device fails to reproduce accurately the waves to follow the initial one while the LDV detect the velocity amplitude on the specimen surface in a wide frequency range encouraging the discussion over the quantification of observed waveforms. 10 refs., 7 figs.

  11. A New Approach to Laminar Flowmeters

    Directory of Open Access Journals (Sweden)

    Alvaro Deibe

    2010-11-01

    Full Text Available After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop.

  12. The "Swiss-cheese Doppler-guided laser tonsillectomy": a new safe cribriform approach to intracapsular tonsillectomy.

    Science.gov (United States)

    Palmieri, B; Iannitti, T; Fistetto, G; Rottigni, V

    2013-05-01

    Outpatient laser ablation of palatine tonsils is a very interesting procedure that has been recently introduced as a routine in head and neck surgery departments. The aim of this study was to describe a new strategy using a Doppler-guided fibre optic neodymium-yttrium-aluminium-garnet (YAG) laser to remove up to 80 % of tonsillar tissue, as assessed in the long-term postoperative clinical evaluation of the volume of the tonsils at the follow-up, and leaving the capsule in place, thus avoiding any haemorrhagic complication and minimize pain. A total of 20 patients (men, n=13; women, n=7), aged between 6 and 63, were recruited for the procedure. They were affected by chronic hypertrophic tonsillitis with a recurrent fever and other symptoms that were related to oral inflammation. Among the 20 patients, no serious adverse events, including haemorrhage-related complications, were observed. Treatment was well tolerated, even in patients displaying an overall low pain threshold. No dropout or uncompleted procedure occurred in the present study. Minor complications included sore throat, moderate oedema, mild acute pharynx inflammation, slight peritonsillar exudate and local burning. The postoperative pain, measured by Scott-Huskisson visual analogue scale, was between 5 and 40 mm and was easily counteracted by means of external ice packages and nonsteroidal anti-inflammatory drugs, according to the individual patient's need. During the 12-36-month follow-up patients showed improved symptoms (n=7) and complete recovery (n=13). A relapse episode was observed in two patients. This study supports fibre optic laser neodymium-YAG tonsil surgery, named "cribriform intracapsular tonsillectomy" or "Swiss-cheese laser tonsillectomy", as an effective alternative to the traditional cold knife approach or electrosurgery. This approach could become the gold standard for tonsil surgery in the third millennium for safety reasons, acceptable cost-benefit ratio, the precise targeting of the beam across the affected tissues and the short- and long-term recovery. PMID:22855380

  13. A remote and non-contact method for obtaining the blood-pulse waveform with a laser Doppler vibrometer

    Science.gov (United States)

    Desjardins, Candida L.; Antonelli, Lynn T.; Soares, Edward

    2007-02-01

    The use of lasers to remotely and non-invasively detect the blood pressure waveform of humans and animals would provide a powerful diagnostic tool. Current blood pressure measurement tools, such as a cuff, are not useful for burn and trauma victims, and animals require catheterization to acquire accurate blood pressure information. The purpose of our sensor method and apparatus invention is to remotely and non-invasively detect the blood pulse waveform of both animals and humans. This device is used to monitor an animal or human's skin in proximity to an artery using radiation from a laser Doppler vibrometer (LDV). This system measures the velocity (or displacement) of the pulsatile motion of the skin, indicative of physiological parameters of the arterial motion in relation to the cardiac cycle. Tests have been conducted that measures surface velocity with an LDV and a signal-processing unit, with enhanced detection obtained with optional hardware including a retro-reflector dot. The blood pulse waveform is obtained by integrating the velocity signal to get surface displacement using standard signal processing techniques. Continuous recording of the blood pulse waveform yields data containing information on cardiac health and can be analyzed to identify important events in the cardiac cycle, such as heart rate, the timing of peak systole, left ventricular ejection time and aortic valve closure. Experimental results are provided that demonstrates the current capabilities of the optical, non-contact sensor for the continuous, non-contact recording of the blood pulse waveform without causing patient distress.

  14. Acute Effects of Vascular Modifying Agents in Solid Tumors Assessed by Noninvasive Laser Doppler Flowmetry and Near Infrared Spectroscopy

    Directory of Open Access Journals (Sweden)

    Michael Kragh

    2002-01-01

    Full Text Available The potential of noninvasive laser Doppler flowmetry (LDF and near infrared spectroscopy (NIRS to detect acute effects of different vascular-modifying agents on perfusion and blood volume in tumors was evaluated. C3H mouse mammary carcinomas (?200 mm3 in the rear foot of CDF1 mice were treated with flavone acetic acid (FAA, 150 mg/kg, 5,6-dimethylxanthenone-4acetic acid (DMXAA, 20 mg/kg, combretastatin A-4 disodium phosphate (CAMP, 250 mg/kg, hydralazine (HDZ, 5 mg/kg, or nicotinamide (NTA, 500 mg/kg. Tumor perfusion before and after treatment was evaluated by noninvasive LDF, using a 41°C heated custombuilt LDF probe with four integrated laser/receiver units, and tumor blood volume was estimated by MRS, using light guide coupled reflectance measurements at 800±10 nm. FAA, DMXAA, CAMP, and HDZ significantly decreased tumor perfusion by 50%, 47%, 73%, and 78%, respectively. In addition, FAA, DMXAA, and HDZ significantly reduced the blood volume within the tumor, indicating that these compounds to some degree shunted blood from the tumor to adjacent tissue, HDZ being most potent. CAMP caused no change in the tumor blood volume, indicating that the mechanism of action of CAMP was vascular shut down with the blood pool trapped in the tumor. NTA caused no change in either tumor perfusion or tumor blood volume. We conclude that noninvasive LDF and MRS can determine acute effects of vascular modifying agents on tumor perfusion and blood volume.

  15. The ejector flowmeter: an evaluation of its accuracy.

    Science.gov (United States)

    Waaben, J; Thomsen, A

    1978-01-01

    The accuracy of five ejector flowmeters was assessed using three different gases and four flow-rates. A soap-bubble flowmeter was used for the calibaration. Significant variations were found between individual flowmeters and between different gas mixtures. No variation was found between the four different flowrates, indicating that the calibration is linear. The mean calibration factor was 84.8% +/- 4.1 (100% O2:87.4 +/- 3.4, 50% N2O/O2: 84.2 +/- 2.8, and 100% N2O: 83.0 +/- 4.6). PMID:151475

  16. Nd:YAG laser bloodless tonsillectomy by fiber optic doppler coupled handpiece beam delivery

    Science.gov (United States)

    Palmieri, Beniamino; Rottigni, Valentina

    2012-09-01

    Laser ablation of palatine tonsils is a relatively new technique recently performed in head and neck surgery departments, in order to treat recurrent tonsillar infections or obstructions from enlarged tonsils. In our study, we have investigated a new procedure using the fiber optic laser beam Nd:YAG to remove up to the 89% of tonsillar tissue, and leaving in place the capsule avoiding any hemorrhagic complication and limiting the pain.

  17. Decomposition of a laser-Doppler spectrum for estimation of speed distribution of particles moving in an optically turbid medium: Monte Carlo validation study

    International Nuclear Information System (INIS)

    A method for measurement of distribution of speed of particles moving in an optically turbid medium is presented. The technique is based on decomposition of the laser-Doppler spectrum. The theoretical background is shown together with the results of Monte Carlo simulations, which were performed to validate the proposed method. The laser-Doppler spectra were obtained by Monte Carlo simulations for assumed uniform and Gaussian speed distributions of particles moving in the turbid medium. The Doppler shift probability distributions were calculated by Monte Carlo simulations for several anisotropy factors of the medium, assuming the Hanyey-Greenstein phase function. The results of the spectra decomposition show that the calculated speed distribution of moving particles match well the distribution assumed for Monte Carlo simulations. This result was obtained for the spectra simulated in optical conditions, in which the photon is scattered with the Doppler shift not more than once during its travel between the source and detector. Influence of multiple scattering of the photon is analysed and a perspective of spectrum decomposition under such conditions is considered. Potential applications and limitations of the method are discussed

  18. Measurements of velocity profiles in a supersonic wind tunnel using the Laser-Doppler Method

    International Nuclear Information System (INIS)

    A laser-velocimeter has been installed on a 100 x 100-mm-supersonic wind tunnel for measurements of mean velocity distributions and intensities of turbulence in the boundary layer of the tunnel at supersonic Mach numbers M = 1.75 and 2.5. The measured values, being reduced by means of a double counter method, have been compared with those formerly found using a combined pressure and temperature probe. The good correspondence of both results confirms that the laser-velocimetry is available as a non-interfering method for surveying supersonic flows. (orig.)

  19. Impurity detection in the APEX tokamak by in-situ doppler shift laser fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Laser fluorescence spectroscopy (LFS) is a promising impurity atoms generated from surfaces exposed to fusion plasmas. Here the first continuous wave laser fluorescene measurement of impurities generated during a single tokamak pulse is reported. The results point out the promise of LFS as an essentially real time, in-situ diagnostic allowing a detailed comparison of impurity generation and transport with Tokamak parameters and operating conditions. Results presented will include the Zr-atom density and velocity distribution produced from a Zr-metal target during an Apex Tokamak discharge

  20. Three-component laser Doppler velocimeter measurements in a juncture flow

    Science.gov (United States)

    Kubendran, L. R.; Meyers, Jim F.

    1987-01-01

    A single-axis, five-beam, three-component laser velocimeter (LV) system was used in a major experiment. Satisfactory results were obtained with the LV system in the juncture flow. Limited optical access to the tunnel proved to be a problem for the three component LV system in determining the third component.

  1. Physical model experiment for wave field measurements by means of laser Doppler vibrometer. Measurement of three components; Laser Doppler shindokei ni yoru butsuri model jikken. Hado sanseibun no kenshutsu

    Energy Technology Data Exchange (ETDEWEB)

    Nishizawa, O.; Sato, T. [Geological Survey of Japan, Tsukuba (Japan); Lei, X. [DIA Consultant Co. Ltd., Tokyo (Japan)

    1997-05-27

    In this experiment, a beam incident from an oblique direction is reflected by a spherical lens toward the direction of incidence. When the surface of a matter is vibrated by elastic waves, the spherical lens comes into a translation motion that accompanies the vibration. It follows accordingly that the vibration on the surface of the matter may be detected by sensing the spherical lens travelling speed. Three components of the vibration may be determined if beams are focused at one spot from three directions. Detection of the S-wave component by LDV (laser Doppler vibrometer) discloses the complicated wave field in a heterogeneous material, and this physical model experiment may be utilized in various fields of study. For instance, information about problems that may surface in the field work may be collected beforehand in a physical model experiment for developing an S-wave-aided probing method. For the study of seismic wave propagation in a complicated three-dimensional ground structure, a numerical model is not enough, and a physical model experiment will be an effective method to fulfill the purpose. In the monitoring of cracks in a rock, again, not only elastic wave velocity but also waveform information collected from a physical model experiment should be fully utilized. 6 refs., 6 figs.

  2. An evaluation of borehole flowmeters used to measure horizontal ground-water flow in limestones of Indiana, Kentucky, and Tennessee, 1999

    Science.gov (United States)

    Wilson, John T.; Mandell, Wayne A.; Paillet, Frederick L.; Bayless, E. Randall; Hanson, Randall T.; Kearl, Peter M.; Kerfoot, William B.; Newhouse, Mark W.; Pedler, William H.

    2001-01-01

    Three borehole flowmeters and hydrophysical logging were used to measure ground-water flow in carbonate bedrock at sites in southeastern Indiana and on the westcentral border of Kentucky and Tennessee. The three flowmeters make point measurements of the direction and magnitude of horizontal flow, and hydrophysical logging measures the magnitude of horizontal flowover an interval. The directional flowmeters evaluated include a horizontal heat-pulse flowmeter, an acoustic Doppler velocimeter, and a colloidal borescope flowmeter. Each method was used to measure flow in selected zones where previous geophysical logging had indicated water-producing beds, bedding planes, or other permeable features that made conditions favorable for horizontal-flow measurements. Background geophysical logging indicated that ground-water production from the Indiana test wells was characterized by inflow from a single, 20-foot-thick limestone bed. The Kentucky/Tennessee test wells produced water from one or more bedding planes where geophysical logs indicated the bedding planes had been enlarged by dissolution. Two of the three test wells at the latter site contained measurable vertical flow between two or more bedding planes under ambient hydraulic head conditions. Field measurements and data analyses for each flow-measurement technique were completed by a developer of the technology or by a contractor with extensive experience in the application of that specific technology. Comparison of the horizontal-flow measurements indicated that the three point-measurement techniques rarely measured the same velocities and flow directions at the same measurement stations. Repeat measurements at selected depth stations also failed to consistently reproduce either flow direction, flow magnitude, or both. At a few test stations, two of the techniques provided similar flow magnitude or direction but usually not both. Some of this variability may be attributed to naturally occurring changes in hydraulic conditions during the 1-month study period in August and September 1999. The actual velocities and flow directions are unknown; therefore, it is uncertain which technique provided the most accurate measurements of horizontal flow in the boreholes and which measurements were most representative of flow in the aquifers. The horizontal heat-pulse flowmeter consistently yielded flow magnitudes considerably less than those provided by the acoustic Doppler velocimeter and colloidal borescope. The design of the horizontal heat-pulse flowmeter compensates for the local acceleration of ground-water velocity in the open borehole. The magnitude of the velocities estimated from the hydrophysical logging were comparable to those of the horizontal heat-pulse flowmeter, presumably because the hydrophysical logging also effectively compensates for the effect of the borehole on the flow field and averages velocity over a length of borehole rather than at a point. The acoustic Doppler velocimeter and colloidal borescope have discrete sampling points that allow for measuring preferential flow velocities that can be substantially higher than the average velocity through a length of borehole. The acoustic Doppler velocimeter and colloidal borescope also measure flow at the center of the borehole where the acceleration of the flow field should be greatest. Of the three techniques capable of measuring direction and magnitude of horizontal flow, only the acoustic Doppler velocimeter measured vertical flow. The acoustic Doppler velocimeter consistently measured downward velocity in all test wells. This apparent downward flow was attributed, in part, to particles falling through the water column as a result of mechanical disturbance during logging. Hydrophysical logging yielded estimates of vertical flow in the Kentucky/Tennessee test wells. In two of the test wells, the hydrophysical logging involved deliberate isolation of water-producing bedding planes with a packer to ensure that small horizontal flow could be quantified without the presence of vertical flow. The presence of verti

  3. Embedded Multi-Tone Ultrasonic Excitation and Continuous-Scanning Laser Doppler Vibrometry for Rapid and Remote Imaging of Structural Defects

    OpenAIRE

    Flynn, Eric B.

    2014-01-01

    We describe a novel method for rapidly measuring local wave dispersion properties using steady-state excitation continuous-scanning laser Doppler vibrometery (CSLDV). In our approach, we excite a structure with a periodic ultrasonic waveform constructed from the sum of several single-tone waveforms. The structure is excited continuously, bringing it to steady-state. We then measure the steady-state response of the structure through CLSDV. The continuous scan gives a one-dimensional time-histo...

  4. Simultaneous broadband laser ranging and photonic Doppler velocimetry for dynamic compression experiments.

    Science.gov (United States)

    La Lone, B M; Marshall, B R; Miller, E K; Stevens, G D; Turley, W D; Veeser, L R

    2015-02-01

    A diagnostic was developed to simultaneously measure both the distance and velocity of rapidly moving surfaces in dynamic compression experiments, specifically non-planar experiments where integrating the velocity in one direction does not always give the material position accurately. The diagnostic is constructed mainly from fiber-optic telecommunications components. The distance measurement is based on a technique described by Xia and Zhang [Opt. Express 18, 4118 (2010)], which determines the target distance every 20 ns and is independent of the target speed. We have extended the full range of the diagnostic to several centimeters to allow its use in dynamic experiments, and we multiplexed it with a photonic Doppler velocimetry (PDV) system so that distance and velocity histories can be measured simultaneously using one fiber-optic probe. The diagnostic was demonstrated on a spinning square cylinder to show how integrating a PDV record can give an incorrect surface position and how the ranging diagnostic described here obtains it directly. The diagnostic was also tested on an explosive experiment where copper fragments and surface ejecta were identified in both the distance and velocity signals. We show how the distance measurements complement the velocity data. Potential applications are discussed. PMID:25725828

  5. Simultaneous broadband laser ranging and photonic Doppler velocimetry for dynamic compression experiments

    Science.gov (United States)

    La Lone, B. M.; Marshall, B. R.; Miller, E. K.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2015-02-01

    A diagnostic was developed to simultaneously measure both the distance and velocity of rapidly moving surfaces in dynamic compression experiments, specifically non-planar experiments where integrating the velocity in one direction does not always give the material position accurately. The diagnostic is constructed mainly from fiber-optic telecommunications components. The distance measurement is based on a technique described by Xia and Zhang [Opt. Express 18, 4118 (2010)], which determines the target distance every 20 ns and is independent of the target speed. We have extended the full range of the diagnostic to several centimeters to allow its use in dynamic experiments, and we multiplexed it with a photonic Doppler velocimetry (PDV) system so that distance and velocity histories can be measured simultaneously using one fiber-optic probe. The diagnostic was demonstrated on a spinning square cylinder to show how integrating a PDV record can give an incorrect surface position and how the ranging diagnostic described here obtains it directly. The diagnostic was also tested on an explosive experiment where copper fragments and surface ejecta were identified in both the distance and velocity signals. We show how the distance measurements complement the velocity data. Potential applications are discussed.

  6. ALADIN: an atmosphere laser doppler wind lidar instrument for wind velocity measurements from space

    Science.gov (United States)

    Krawczyk, Rodolphe; Ghibaudo, Jean-Bernard; Labandibar, Jean-Yves; Willetts, David V.; Vaughan, M.; Pearson, G.; Harris, M. R.; Flamant, Pierre H.; Salamitou, P.; Dabas, Alain; Charasse, R.; Midavaine, Thierri; Royer, Michel; Heimel, H.

    1995-12-01

    AEROSPATIALE, leading a European team, has just conducted a successful study, under ESA contract, to demonstrate the feasibility of a spaceborne Doppler wind lidar instrument meeting the scientific requirements of wind velocity measurements from space with high spatial resolution. A first parametric investigation, based upon the initial set of mission requirements, and supported by dedicated models and detailed trade-off studies, took account of capabilities of the most promising signal processing algorithms and calibration/validation constrains: it yielded a large conically scanned instrument deemed technologically risky. A risk analysis was then carried out to propose a less challenging instrument meeting most key mission requirements. The fixed line-of-sight concept with return signal accumulation appeared as most attractive. A second set of requirements agreed upon by scientific users was therefore issued, with relaxed constraints mainly on horizontal resolution, keeping roughly the same level of wind velocity measurement accuracy. A second instrument and subsystem trade- off was then performed to eventually produce an attractive instrument concept based upon a pair of small diameter telescopes each one associated to one scanning mirror rotating stepwise around the telescope axis, which drastically reduces the detection bandwidth. Following the main contract, studies of accommodation on the International Space Station have been performed, confirming the interest of such an instrument for wind measurements from space.

  7. ALADIN: an atmospheric laser Doppler wind lidar instrument for wind velocity measurements from space

    Science.gov (United States)

    Krawczyk, Rodolphe; Ghibaudo, Jean-Bernard; Labandibar, Jean-Yves; Willetts, David V.; Vaughan, M.; Pearson, G.; Harris, M. R.; Flamant, Pierre H.; Salamitou, P.; Dabas, Alain; Lieutaud, F.; Charasse, R.; Midavaine, Thierri; Royer, Michel; Heimel, H.

    1996-10-01

    AEROSPATIALE, leading a European team, has just conducted a successful study, under ESA contract, to demonstrate the feasibility of a spaceborne Doppler wind lidar instrument meeting the scientific requirements of wind velocity measurements from space with high spatial resolution. A first parametric investigation, based upon the initial set of mission requirements, and supported by dedicated models and detailed trade-off studies, took account of capabilities of most promising signal processing algorithms and calibration/validation constraints: it yielded a large conically scanned instrument deemed technologically risky. A risk analysis was then carried out to propose a less challenging instrument meeting most key mission requirements. The fixed line-of-sight concept with return signal accumulation appeared as most attractive. A second set of requirements agreed upon by scientific users was therefore issued, with relaxed constraints mainly on horizontal resolution, keeping roughly the same level of wind velocity measurement accuracy. A second instrument and subsystem trade-off was then performed to eventually produce an attractive instrument concept based upon a pair of small diameter telescopes each one associated to one scanning mirror rotating stepwise around the telescope axis, which drastically reduces the detection bandwidth. Following the main contract, studies of accommodation on the International Space Station have been performed, confirming the interest of such an instrument for wind measurements from space.

  8. Time dependent Doppler shifts in high-order harmonic generation in intense laser interactions with solid density plasma and frequency chirped pulses

    Science.gov (United States)

    Welch, E. C.; Zhang, P.; Dollar, F.; He, Z.-H.; Krushelnick, K.; Thomas, A. G. R.

    2015-05-01

    High order harmonic generation from solid targets is a compelling route to generating intense attosecond or even zeptosecond pulses. However, the effects of ion motion on the generation of harmonics have only recently started to be considered. Here, we study the effects of ion motion in harmonics production at ultrahigh laser intensities interacting with solid density plasma. Using particle-in-cell simulations, we find that there is an optimum density for harmonic production that depends on laser intensity, which scales linearly with a0 with no ion motion but with a reduced scaling if ion motion is included. We derive a scaling for this optimum density with ion motion and also find that the background ion motion induces Doppler red-shifts in the harmonic structures of the reflected pulse. The temporal structure of the Doppler shifts is correlated to the envelope of the incident laser pulse. We demonstrate that by introducing a frequency chirp in the incident pulse we are able to eliminate these Doppler shifts almost completely.

  9. Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry

    OpenAIRE

    Crua, Cyril; Heikal, Morgan R.

    2015-01-01

    In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a three dimensional laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working...

  10. Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor

    OpenAIRE

    Cooper, W. A.; Spuler, S. M.; Spowart, M.; Lenschow, D. H.; Friesen, R. B.

    2014-01-01

    A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s?1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in thos...

  11. A near infrared laser frequency comb for high precision Doppler planet surveys

    Directory of Open Access Journals (Sweden)

    Bally J.

    2011-07-01

    Full Text Available Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV measurements, with the most stable visible light spectrographs reporting RV results the order of 1?m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

  12. Multiscale Compression Entropy of Microvascular Blood FlowSignals: Comparison of Results from Laser Speckle Contrastand Laser Doppler Flowmetry Data in Healthy Subjects

    Directory of Open Access Journals (Sweden)

    Anne Humeau-Heurtier

    2014-11-01

    Full Text Available Microvascular perfusion is commonly used to study the peripheral cardiovascular system. Microvascular blood flow can be continuously and non-invasively monitored with laser speckle contrast imaging (LSCI or with laser Doppler flowmetry (LDF. These two optical-based techniques give perfusion values in arbitrary units. Our goal is to better understand the perfusion time series given by each technique. For this purpose, we propose a nonlinear complexity analysis of LSCI and LDF time series recorded simultaneously in nine healthy subjects. This is performed through the computation of their multiscale compression entropy. The results obtained with LSCI time series computed from different regions of interest (ROI sizes are examined. Our findings show that, for LSCI and LDF time series, compression entropy values are less than one for all of the scales analyzed. This suggests that, for all scales, there are repetitive structures within the data fluctuations. Moreover, at the largest scales studied, LDF signals seem to have structures that are different from those Entropy 2014, 16 5778 of Gaussian white noise. By opposition, this is not observed for LSCI time series computed from small ROI sizes

  13. Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in laser-cooled fermionic isotopes of neutral mercury

    OpenAIRE

    Petersen, M.; Chicireanu, R.; Dawkins, S. T.; Magalhães, D. V.; Mandache, C.; Lecoq, Y.; Clairon, A; Bize, S.

    2008-01-01

    We have performed for the first time direct laser spectroscopy of the 1S0-3P0 optical clock transition at 265.6 nm in fermionic isotopes of neutral mercury laser-cooled in a magneto-optical trap. Spectroscopy is performed by measuring the depletion of the magneto-optical trap induced by the excitation of the long-lived 3P0 state by a probe at 265.6 nm. Measurements resolve the Doppler-free recoil doublet allowing for a determination of the transition frequency to an uncer- t...

  14. Laser Echosclerotherapy of varicose veins with haemodynamic echo-doppler evaluation : some rationale and short-term outcomes

    Science.gov (United States)

    Vettorello, Gianfranco; Marini, Leonardo

    2009-06-01

    Purpose: The aim is to verify short-term results in Endovenous Laser Treatment (EVLT) performed in haemodynamic way in patients belonging to C2, C3 classes and type I, II, III venous shunts, according respectively with CEAP and Teupitz classification. Methods: Minor changes of technique were applied to EVLT in order to provide haemodynamic conditions. Treatment efficacy, anatomical failure, complications, recurrence rate and clinical improvements were analyzed. 105 limbs were treated from November 2004 to November 2007. Clinical and Echo-Colour-Doppler (ECD) follow up was performed two weeks, one, two and three years after the surgery. Results: in 79 inferior limbs follow-up was concluded and this are the final data: a) no Deep Venous Thrombosis (DVT) was detected; b) a notable reduction of recurrence if compared with groin recurrence rate in traditional stripping; e) satisfactory cosmetic results and short recovery were found in all the patients. Conclusions: In selected patients haemodynamic-guided EVLT is equally safe and efficient than standard. Clinical and aesthetical outcomes are durable without statistical differences on the plan of disease progression and complications. The recurrence rate is lower in EVLT haemodynamic-guided surgery than in conventional stripping. Long-term outcomes should be investigated. We need studies camparison among the three different kind of surgery performed in haemodynamic way

  15. Experimental Study of the Applicability of the Remotely Positioned Laser Doppler Vibrometer to Rock-Block Stability Assessment

    Science.gov (United States)

    Ma, Gui-Chen; Sawada, Kazuhide; Yashima, Atsushi; Saito, Hideki

    2015-03-01

    This paper examines a new method for evaluating the stability of rock blocks on slopes using a remotely positioned Laser Doppler Vibrometer (LDV). A series of experiments using physical models were conducted to evaluate the validity of this new method. Based on the experimental studies, the applicability of LDV was examined by comparing results with a conventional seismometer measurement. To examine the quantitative correlations between vibration properties and the stability of a rock block, the effects on the vibration properties of the size of the rock block, the initial block position, the slope incline, and the type of ground surface were studied. The experimental results showed that LDV measurements agreed with conventional seismometer measurements. There was also a good correlation between vibration properties and rock-block stability. On the other hand, it was found that for a boulder on tightly compacted ground, the application of block stability assessment by tonometry was difficult when measuring microtremors or sloppy vibration due to nearby vehicle traffic. Furthermore, numerical analysis of the slope model was carried out to examine the validity of the model experiment and application of the suggested technique. The results of the analysis demonstrated that the suggested technique was effective for application to stability monitoring of a block and evaluation of the effect of stability measures.

  16. Multifractal analysis of central (electrocardiography) and peripheral (laser Doppler flowmetry) cardiovascular time series from healthy human subjects

    International Nuclear Information System (INIS)

    Analysis of the cardiovascular system (CVS) activity is important for several purposes, including better understanding of heart physiology, diagnosis and forecast of cardiac events. The central CVS, through the study of heart rate variability (HRV), has been shown to exhibit multifractal properties, possibly evolving with physiologic or pathologic states of the organism. An additional viewpoint on the CVS is provided at the peripheral level by laser Doppler flowmetry (LDF), which enables local blood perfusion monitoring. We report here for the first time a multifractal analysis of LDF signals through the computation of their multifractal spectra. The method for estimation of the multifractal spectra, based on the box method, is first described and tested on a priori known synthetic multifractal signals, before application to LDF data. Moreover, simultaneous recordings of both central HRV and peripheral LDF signals, and corresponding multifractal analyses, are performed to confront their properties. With the scales chosen on the partition functions to compute Renyi exponents, LDF signals appear to have broader multifractal spectra compared to HRV. Various conditions for LDF acquisitions are tested showing larger multifractal spectra for signals recorded on fingers than on forearms. The results uncover complex interactions at central and peripheral CVS levels

  17. Repeatability, Reproducibility and Standardisation of a Laser Doppler Imaging Technique for the Evaluation of Normal Mouse Hindlimb Perfusion

    Directory of Open Access Journals (Sweden)

    Arturo Brunetti

    2012-12-01

    Full Text Available Background. Preclinical perfusion studies are useful for the improvement of diagnosis and therapy in dermatologic, cardiovascular and rheumatic human diseases. The Laser Doppler Perfusion Imaging (LDPI technique has been used to evaluate superficial alterations of the skin microcirculation in surgically induced murine hindlimb ischemia. We assessed the reproducibility and the accuracy of LDPI acquisitions and identified several critical factors that could affect LDPI measurements in mice. Methods. Twenty mice were analysed. Statistical standardisation and a repeatability and reproducibility analysis were performed on mouse perfusion signals with respect to differences in body temperature, the presence or absence of hair, the type of anaesthesia used for LDPI measurements and the position of the mouse body. Results. We found excellent correlations among measurements made by the same operator (i.e., repeatability under the same experimental conditions and by two different operators (i.e., reproducibility. A Bland-Altman analysis showed the absence of bias in repeatability (p = 0.29 or reproducibility (p = 0.89. The limits of agreement for repeatability were –0.357 and –0.033, and for reproducibility, they were –0.270 and 0.238. Significant differences in perfusion values were observed in different experimental groups. Conclusions. Different experimental conditions must be considered as a starting point for the evaluation of new drugs and strategic therapies.

  18. [Blood flow, CO2 response and autoregulation in the rat spinal cord by laser-Doppler flowmetry and hydrogen clearance].

    Science.gov (United States)

    Wang, R; Ehara, K; Fujita, K; Tamaki, N; Matsumoto, S

    1991-07-01

    Spinal cord blood flow (SCBF) was measured simultaneously by laser Doppler flowmetry (LDF) and hydrogen clearance (HC) in the normal Wistar rats. Under normal physiological condition, SCBF values by HC was 45.0 +/- 1.7 ml/min/100 g at the level of Th-8. LDF values were well correlated (r = 0.78) to the SCBF measured by HC, where linear regression line was obtained as y = 14.2x - 1.58. Absolute SCBF values of LDF were also calculated as 43.7 +/- 1.3 mg/min/100 g using this equation. CO2 response of SCBF were 1.09 ml/min/100 g/mmHg by HC and 1.01 ml/min/100 g by LDF, respectively. Autoregulation of SCBF maintained at a range of 55 -155 mmHg of mean arterial pressure in both methods. In conclusion, LDF is a useful technique for continuous SCBF monitoring. Since absolute SCBF value in LDF has some variance, the relative value is more suitable for accurate evaluation of SCBF during time course of an experiment. PMID:1832914

  19. Study on Water Distribution Imaging in the Sand Using Propagation Velocity of Sound with Scanning Laser Doppler Vibrometer

    Science.gov (United States)

    Sugimoto, Tsuneyoshi; Nakagawa, Yutaka; Shirakawa, Takashi; Sano, Motoaki; Ohaba, Motoyoshi; Shibusawa, Sakae

    2013-07-01

    We propose a method for the monitoring and imaging of the water distribution in the rooting zone of plants using sound vibration. In this study, the water distribution measurement in the horizontal and vertical directions in the soil layer was examined to confirm whether a temporal change in the volume water content of the soil could be estimated from a temporal changes in propagation velocity. A scanning laser Doppler vibrometer (SLDV) is used for measurement of the vibration velocity of the soil surface, because the highly precise vibration velocity measurement of several many points can be carried out automatically. Sand with a uniform particle size distribution is used for the soil, as it has high plasticity; that is, the sand can return to a dry state easily even if it is soaked with water. A giant magnetostriction vibrator or a flat speaker is used as a sound source. Also, a soil moisture sensor, which measures the water content of the soil using the electric permittivity, is installed in the sand. From the experimental results of the vibration measurement and soil moisture sensors, we can confirm that the temporal changes of the water distribution in sand using the negative pressure irrigation system in both the horizontal and vertical directions can be estimated using the propagation velocity of sound. Therefore, in the future, we plan to develop an insertion-type sound source and receiver using the acceleration sensors, and we intend to examine whether our method can be applied even in commercial soil with growing plants.

  20. Studies of blood flow in human nasal mucosa with /sup133/Xe washout technique and laser doppler flowmetry

    International Nuclear Information System (INIS)

    The techniques were applied for studies of the influence of environmental temperature on the human nasal mucosa, for studies of mediators in nasal allergy and for studies of the sympathetic neurogenic control of blood flow in the nasal mucosa. The results show that the two techniques are complementary to one another. The /sup133/Xe washout technique is useful for semiquantitative estimations of blood flow in the deeper parts of the mucosa, while the laser doppler technique is especially suited for continuous recordings of relative blood flow changes in the superficial part of the mucosa. Vascular changes may take part in body temperature regulation changes may take part in body temperature regulation as well as in conditioning of respiratory air. The results support the theories that changes in nasal mucosal blood flow are related to body temperature control, while conditioning of inspiratory air may be more dependent on mucosal blood content. The observed dissociation between changes in the resistance and the capacitance vessels also illustrates that these vascular segments are regulated in different ways. The present results indicate that leukotriene D/sub4/ might contribute to an increased blood flow in the nasal mucosa and to blockage of the nasal airway in the acute allergic reaction. Vasomotion is demonstrated to be present in the nasal mucosa, and it appears to be partly dependent on sympathetic neurogenic activity. The development of the present techniques, means that vascular changes involved in normal nasal function and in nasal disease may be evaluated by a new approach. (author)

  1. Multifractal analysis of heart rate variability and laser Doppler flowmetry fluctuations:comparison of results from different numerical methods

    International Nuclear Information System (INIS)

    To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.

  2. Experimental determination of mode correction factors for thermal method spring constant calibration of AFM cantilevers using laser Doppler vibrometry

    International Nuclear Information System (INIS)

    Mode correction factors (MCFs) represent a significant adjustment to the spring constant values measured using the thermal cantilever calibration method. Usually, the ideal factor of 0.971 for a tipless rectangular cantilever is used, which adjusts the value by 3% for the first flexural mode. An experimental method for determining MCFs has been developed that relies on measuring the areas under the first few resonance peaks for the flexural mode type. Using this method, it has been shown that MCFs for the first flexural mode of commercially available atomic force microscope cantilevers actually vary from 0.95 to 1.0, depending on the shape and end mass of the cantilever. Triangular shaped cantilevers tend to lower MCFs with tipless versions providing the lowest values. Added masses (including tips) tend to increase the first flexural mode’s MCF to higher values with large colloid probes at the high extreme. Using this understanding and applying it to the recently developed laser Doppler vibrometry thermal calibration method it is now possible to achieve very accurate and precise cantilever spring constant calibrations (uncertainties close to ±1%) with commonly available commercial cantilevers such as tipped rectangular and triangular cantilevers, and colloid probes. (paper)

  3. Heterodyne laser Doppler distance sensor with phase coding measuring stationary as well as laterally and axially moving objects

    International Nuclear Information System (INIS)

    Both in production engineering and process control, multidirectional displacements, deformations and vibrations of moving or rotating components have to be measured dynamically, contactlessly and with high precision. Optical sensors would be predestined for this task, but their measurement rate is often fundamentally limited. Furthermore, almost all conventional sensors measure only one measurand, i.e. either out-of-plane or in-plane distance or velocity. To solve this problem, we present a novel phase coded heterodyne laser Doppler distance sensor (PH-LDDS), which is able to determine out-of-plane (axial) position and in-plane (lateral) velocity of rough solid-state objects simultaneously and independently with a single sensor. Due to the applied heterodyne technique, stationary or purely axially moving objects can also be measured. In addition, it is shown theoretically as well as experimentally that this sensor offers concurrently high temporal resolution and high position resolution since its position uncertainty is in principle independent of the lateral object velocity in contrast to conventional distance sensors. This is a unique feature of the PH-LDDS enabling precise and dynamic position and shape measurements also of fast moving objects. With an optimized sensor setup, an average position resolution of 240 nm was obtained

  4. Laser doppler velocimeter system for subsonic jet mixer nozzle testing at the NASA Lewis Aeroacoustic Propulsion Lab

    Science.gov (United States)

    Podboy, Gary G.; Bridges, James E.; Saiyed, Naseem H.; Krupar, Martin J.

    1995-01-01

    A laser Doppler velocimeter (LDV) system developed for the Aeroacoustic Propulsion Laboratory (APL) at the NASA Lewis Research Center is described. This system was developed to acquire detailed flow field data which could be used to quantify the effectiveness of internal exhaust gas mixers (IEGM's) and to verify and calibrate computational codes. The LDV was used as an orthogonal, three component system to measure the flow field downstream of the exit of a series of IEGM's and a reference axisymmetric splitter configuration. The LDV system was also used as a one component system to measure the internal axial flow within the nozzle tailpipe downstream of the mixers. These IEGM's were designed for low-bypass ratio turbofan engines. The data were obtained at a simulated low flight speed, high-power operating condition. The optical, seeding, and data acquisition systems of the LDV are described in detail. Sample flow field measurements are provided to illustrate the capabilities of the system at the time of this test, which represented the first use of LDV at the APL. A discussion of planned improvements to the LDV is also included.

  5. Non-invasive laser Doppler perfusion measurements of large tissue volumes and human skeletal muscle blood RMS velocity

    International Nuclear Information System (INIS)

    This study proposes the implementation of an algorithm allowing one to derive absolute blood root-mean-square (RMS) velocity values from laser Doppler perfusion meter (LDP) data. The algorithm is based on the quasi-elastic light scattering theory and holds for multiple scattering. While standard LDP measurements are normally applicable to a small region of interest (?1 mm2), the present method allows the analysis of both small and large tissue volumes with small and large interoptode spacings (e.g., 1.5 cm). The applicability and the limits of the method are demonstrated with measurements on human skeletal muscle using a custom-built near-infrared LDP meter. Human brachioradialis muscle RMS velocity values of 9.99 ± 0.01 and 5.58 ± 0.03 mm s-1 at 1.5 cm and of 5.18 ± 0.01 and 2.54 ± 0.09 mm s-1 at 2 cm were found when the arm was (a) at rest and (b) occluded, respectively. At very large optode spacings or very high moving particle densities, the theory developed here would need to be amended to take into account second-order effects

  6. A primary standard for the volume flow rate of natural gas under high pressure based on laser Doppler velocimetry

    Science.gov (United States)

    Mickan, B.; Strunck, V.

    2014-10-01

    In December 2003, the Physikalisch-Technische Bundesanstalt (PTB) started the development of an optical-based primary flow rate standard for application in natural gas under high pressures (up to 5.5 MPa). The concept underlying this technology will be presented in this paper. The technical approach is based on the application of a conventional laser Doppler velocimeter (LDV) as well as on a new LDV-based boundary layer sensor. Both technologies are used to determine the characteristic values of the core flow and the boundary layer in a nozzle flow in a separated approach. Because of the high relevance to the demonstration of traceability and to the evaluation of the uncertainty, the related data processing (especially for the boundary layer) is explained in detail. Finally, after summarizing the uncertainty budget for the optical-based primary standard, we will demonstrate the approval of the new primary standard by means of a comparison with the established conventional traceability of PTB for high-pressure natural gas.

  7. A novel laser-Doppler flowmetry assisted murine model of acute hindlimb ischemia-reperfusion for free flap research.

    Science.gov (United States)

    Sönmez, Tolga Taha; Al-Sawaf, Othman; Brandacher, Gerald; Kanzler, Isabella; Tuchscheerer, Nancy; Tohidnezhad, Mersedeh; Kanatas, Anastasios; Knobe, Matthias; Fragoulis, Athanassios; Tolba, René; Mitchell, David; Pufe, Thomas; Wruck, Christoph Jan; Hölzle, Frank; Liehn, Elisa Anamaria

    2013-01-01

    Suitable and reproducible experimental models of translational research in reconstructive surgery that allow in-vivo investigation of diverse molecular and cellular mechanisms are still limited. To this end we created a novel murine model of acute hindlimb ischemia-reperfusion to mimic a microsurgical free flap procedure. Thirty-six C57BL6 mice (n?=?6/group) were assigned to one control and five experimental groups (subject to 6, 12, 96, 120 hours and 14 days of reperfusion, respectively) following 4 hours of complete hindlimb ischemia. Ischemia and reperfusion were monitored using Laser-Doppler Flowmetry. Hindlimb tissue components (skin and muscle) were investigated using histopathology, quantitative immunohistochemistry and immunofluorescence. Despite massive initial tissue damage induced by ischemia-reperfusion injury, the structure of the skin component was restored after 96 hours. During the same time, muscle cells were replaced by young myotubes. In addition, initial neuromuscular dysfunction, edema and swelling resolved by day 4. After two weeks, no functional or neuromuscular deficits were detectable. Furthermore, upregulation of VEGF and tissue infiltration with CD34-positive stem cells led to new capillary formation, which peaked with significantly higher values after two weeks. These data indicate that our model is suitable to investigate cellular and molecular tissue alterations from ischemia-reperfusion such as occur during free flap procedures. PMID:23840492

  8. A new signal-processing approach to mine detection by multibeam laser Doppler vibrometer (MB-LDV)

    Science.gov (United States)

    Wagstaff, Ronald A.; Gilbert, Kenneth E.

    2004-09-01

    Exciting the ground with an acoustic tonal projected by a loud speaker is one method for detecting buried landmines. The subsequent ground motion is measured with a laser Doppler vibrometer (LDV). The LDV data contain the tonal in a frequency modulated form. One approach for demodulating the data and extracting the tonal uses a Hilbert transform. The ground velocity can be obtained from these data to identify mine presence or absence. An alternate approach to mine detection is to perform consecutive fast Fourier transforms on the modulated LDV data, and to average the output powers in each spectral bin. This results in a ground velocity distribution function in the spectrum that is manifested by a broadband of modulated frequencies. The proximity of the beams to a mine (over, near, not near) can be determined from the bandwidth of the modulation. Furthermore, the velocity distribution functions provide additional information that previous techniques do not. Such information may be useful for separating mines from false targets. This technique is discussed, and the results from measured MB-LDV data are presented. This paper is based upon work supported by the U. S. Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.

  9. Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor

    Directory of Open Access Journals (Sweden)

    W. A. Cooper

    2014-09-01

    Full Text Available A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s?1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the global positioning system, then indicate (via integrations of the hydrostatic equation during climbs and descents that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 °C. For airspeed, pressure and temperature, these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that although the initial calibration of the measured static and dynamic pressures requires a measured temperature, once calibrated these measured pressures and the measurement of airspeed from the new laser air-motion sensor provide a measurement of temperature that does not depend on any other temperature sensor.

  10. Performance of laser Doppler velocimeter with polydisperse seed particles in high-speed flows

    Science.gov (United States)

    Samimy, M.; Abu-Hijleh, B. A. K.

    1989-01-01

    The flowfield behind an oblique shock wave, where the LDV measured velocities are seed-particle-size dependent, was used to investigate the effects of LDV system parameters on the range of detectable polydisperse seed particles. The parameters included frequency shifting, laser power, scattered signal amplification level, and number of required fringe crossings. The results showed that with polydisperse seed particles ranging from 0.1 to 4.0 microns available in the flow, the average diameter of the detected particles could change from 0.2 to 3.0 microns by changing different LDV system parameters. The effects of this shift in the range of detectable particles on the frequency response of LDV are discussed.

  11. Performance of laser Doppler velocimeter with polydisperse seed particles in high speed flows

    Science.gov (United States)

    Samimy, M.; Bhattacharyya, S.; Abu-Hijleh, B. A./K.

    1988-01-01

    The flowfield behind an oblique shock wave, where the LDV measured velocities are seed particle size dependent, was used to investigate the effects of LDV system parameters on the range of detectable polydisperse seed particles. The parameters included frequency shifting, laser power, scattered signal amplification level, and number of required fringe crossings. The results showed that with polydisperse seed particles ranging from 0.1 to 4.0 microns available in the flow, the average diameter of the detected particles could change from 0.2 to 3.0 microns by changing different LDV system parameters. The effects of this shift in the range of detectable particles on the frequency response of LDV was discussed.

  12. Doppler Effect

    Science.gov (United States)

    Mrs. Brown

    2010-10-26

    Doppler effect followed from water waves to sound waves to light waves. Red shift of the universe is also explored. What is doppler effect? It is the change in frequency of a wave for an observer moving relative to the source of the wave. What does that mean? Watch this: moving doppler effect video What does the doppler effect look like in a stationary and moving object? dooppler effect views What does doppler effect have to do with stars and galaxies??? View the following ...

  13. A study on the uncertainty estimation of flowmeter calibrator with two master flowmeters

    International Nuclear Information System (INIS)

    Comparing to the gravimetric and volumetric method, the flowmeter calibration based on the master meter method is relatively economical and convenient, especially for high flowrate. The uncertainty of flow quantity and flowrate using the master meter method was evaluated according to the GUM (Guide to the expression of Uncertainty in Measurement). In order to apply for the wider flow range, two master meters (electromagnetic flow meter) were employed as reference flowmeters. The uncertainty of the master meter was obtained by combining the statistical variation of the repeated measurements and the variation of fluid density and pipe material due to temperature and pressure changes were scrutinized. For a practical application, the uncertainty of calibrator, whose measuring capacity of 1000 m3/h obtained by employing two 500 m3/h electromagnetic flow meters, was evaluated. The uncertainty budget shows the quantitative contribution of each uncertainty component to the overall uncertainty of the calibrator. As a result, it was found that the dominant uncertainties were from the master meter, which was evaluated statistically, and from the process of least squares fitting. On the contrary, the uncertainties arising from the variation of the fluid density and the pipe volume due to the temperature and pressure were negligible

  14. Laser Doppler velocimetry for measurement of nonlinearity in the vibrations of the middle ear

    Science.gov (United States)

    Peacock, John; Dirckx, Joris

    2014-05-01

    At audible Frequencies and at sound pressure below 96 dB SPL the mammalian middle ear is known to behave as an almost entirely linear system. However, as we go to higher sound pressure levels, smaller nonlinear distortions begin to appear, and increase with increasing pressure level. Some modern hearing aids seek to remedy hearing impairment by amplifying sounds to sound pressure levels as high as 130 or 140 dB SPL. Thus at these levels the small nonlinear distortions can become significant, and understanding their behaviour could help us to improve the design of these hearing aids. In order to measure the tiny vibration amplitudes of the middle ear, and to detect the even smaller nonlinear distortions, a very sensitive measurement and analysis method is needed. The tiny vibration amplitudes of the middle ear can easily be measured with laser vibrometry. Thanks to the highly linear response of LDV, the technique is also able to measure small nonlinearities. To detect the nonlinear distortions we developed a sophisticated measurement and analysis method based on the use of multisine excitation signals. These signals are specially designed to measure nonlinear systems. We will describe our set up and our stimulation and analysis method in detail, we will then go on to present some results of measurements at different points along the ossicular chain.

  15. A solid state laser system for Doppler-free spectroscopy of muonium

    CERN Document Server

    Bakule, P

    1998-01-01

    to 1MHz, was found to be of the order of 80-120 MHz for a 30-40 mJ output. This chirp was shown to be the result of a fast change of the refractive index in the alexandrite rods, and was found to be directly proportional to the population inversion change during the Q-switched pulse. A method of chirp compensation was developed leading to a reduction of the chirp by an order of magnitude i.e. to the level of 5-15 MHz. The alexandrite output was frequency tripled using LBO and BBO crystals with a conversion efficiency in excess of 10 %, yielding UV pulse energies of 3 to 6 mJ. The 1S-2S transition frequency has been measured to be 2,455,528,940.99 (9.75)(3.5) MHz which is in agreement with the theoretical value of 2,455,528,934.61 (3.44) MHz. Measurement of 1S-2S interval in deuterium, performed primarily to study systematic errors, represents the best pulsed measurement to date and is in an agreement with values obtained with cw lasers. The thesis describes a new high precision measurement of the 1S-2S transi...

  16. Localization of transient signal high-values in laser Doppler flowmetry signals with an empirical mode decomposition.

    Science.gov (United States)

    Humeau, Anne; Trzepizur, Wojciech; Rousseau, David; Chapeau-Blondeau, François; Abraham, Pierre

    2009-01-01

    The laser Doppler flowmetry (LDF) technique provides the monitoring of microvascular blood flow perfusion. However, LDF monitors based on fiber-optic transducers have the serious drawback of generating TRAnsient Signal High-values (TRASH) in signals. These TRASH correspond to artifacts for clinicians as they prevent interpretations of the signal when they are numerous. Moreover, TRASH exclude the possibility of direct signal processing and analyses. Therefore, in clinical routines, a human visual inspection of LDF signals is necessary to detect TRASH and to process the signals accordingly. This may be very time consuming. An algorithm able to localize TRASH automatically for their removal is therefore of interest. However, the development of such an algorithm is not an easy task as TRASH amplitude can be lower, higher, or in the same amplitude range as responses to stimuli such as post-occlusive hyperemia. The recently introduced empirical mode decomposition (EMD) has the advantage of splitting any kind of signal into fast and slow oscillations. Relying on these properties, the authors evaluate the possibility for EMD to localize TRASH automatically. For this purpose, LDF signals from 28 men of different ages are recorded at rest, during a vascular occlusion of 3 min, followed by a post-occlusive hyperemia. For each signal containing TRASH, the first intrinsic mode function obtained with the EMD is processed with a running window-based analysis in which a thresholding of the local maxima is carried out for the localization of TRASH. From the data, the use of a window width of 25 s is suggested. The results show effective and potential usefulness of this algorithm for an automatic localization of TRASH. Moreover, the method proposed has the advantage of being insensitive to the rapid increases of blood flow induced by post-occlusive hyperemia, which is of interest for clinicians. Because it is both local and fully data adaptive, EMD appears as an appealing processing technique for overcoming some of the limitations of the LDF. PMID:19235369

  17. Endothelin-1 induced middle cerebral artery occlusion model for ischemic stroke with laser Doppler flowmetry guidance in rat.

    Science.gov (United States)

    Ansari, Saeed; Azari, Hassan; Caldwell, Kenneth J; Regenhardt, Robert W; Hedna, Vishnumurthy S; Waters, Micheal F; Hoh, Brian L; Mecca, Adam P

    2013-01-01

    Stroke is the number one cause of disability and third leading cause of death in the world, costing an estimated $70 billion in the United States in 2009. Several models of cerebral ischemia have been developed to mimic the human condition of stroke. It has been suggested that up to 80% of all strokes result from ischemic damage in the middle cerebral artery (MCA) area. In the early 1990s, endothelin-1 (ET-1) was used to induce ischemia by applying it directly adjacent to the surface of the MCA after craniotomy. Later, this model was modified by using a stereotaxic injection of ET-1 adjacent to the MCA to produce focal cerebral ischemia. The main advantages of this model include the ability to perform the procedure quickly, the ability to control artery constriction by altering the dose of ET-1 delivered, no need to manipulate the extracranial vessels supplying blood to the brain as well as gradual reperfusion rates that more closely mimics the reperfusion in humans. On the other hand, the ET-1 model has disadvantages that include the need for a craniotomy, as well as higher variability in stroke volume. This variability can be reduced with the use of laser Doppler flowmetry (LDF) to verify cerebral ischemia during ET-1 infusion. Factors that affect stroke variability include precision of infusion and the batch of the ET-1 used. Another important consideration is that although reperfusion is a common occurrence in human stroke, the duration of occlusion for ET-1 induced MCAO may not closely mimic that of human stroke where many patients have partial reperfusion over a period of hours to days following occlusion. This protocol will describe in detail the ET-1 induced MCAO model for ischemic stroke in rats. It will also draw attention to special considerations and potential drawbacks throughout the procedure. PMID:23438950

  18. Nailfold capillaroscopy and blood flow laser-doppler analysis of the microvascular damage in systemic sclerosis: preliminary results

    Directory of Open Access Journals (Sweden)

    C. Pizzorni

    2011-06-01

    Full Text Available Objectives: Systemic sclerosis (SSc is characterized by altered microvascular structure and function. Nailfold videocapillaroscopy (NVC is the tool to evaluate capillary morphological structure and laser-Doppler Blood flowmetry (LDF can be used to estimate cutaneous blood flow of microvessels. The aim of this study was to investigate possible relationships between capillary morphology and blood flow in SSc. Methods: 27 SSc patients and 12 healthy subjects were enrolled. SSc microvascular involvement, as evaluated by NVC, was classified in three different patterns (“Early”, “Active”, “Late”. LDF analysis was performed at the II, III, IV, V hand fingers in both hands and both at cutaneous temperature and at 36°C. Statistical evaluation was carried out by non-parametric procedures. Results: Blood flow was found significantly lower in SSc patients when compared with healthy subjects (p<0.05. The heating of the probe to 36°C induced a significant increase in peripheral blood flow in all subjects compared to baseline (p <0.05, however, the amount of variation was significantly lower in patients with SSc, compared with healthy controls (p <0.05. The SSc patients with NVC “Late” pattern, showed lower values of peripheral blood flow than patients with NVC “Active” or “Early” patterns (p<0.05. Moreover, a negative correlation between the tissue perfusion score and the progression of the SSc microangiopathy was observed, as well as between the tissue perfusion and the duration of the Raynaud’s phenomenon (p <0.03. Conclusions: LDF can be employed to evaluate blood perfusion in the microvascular circulation in SSc patients. The blood flow changes observed with the LDF seem to correlate with the severity of microvascular damage in SSc as detected by NVC.

  19. Speckle noise influence on measuring turbulence spectra using time-resolved Doppler global velocimetry with laser frequency modulation

    International Nuclear Information System (INIS)

    A novel Doppler global velocimeter (DGV) with high temporal resolution is presented as a tool for measuring spatially resolved flow turbulence spectra for three components in order to characterize complex flows, e.g. in turbomachines. The proposed DGV technique is based on a sinusoidal laser frequency modulation. Its maximum available measurement rate equals the modulation frequency and amounts currently to 100 kHz. The harmonic analysis of the detector array signals reduces errors due to detector offset drifts, detector sensitivity changes, ambient light, camera misalignment and beam splitting errors in comparison with conventional DGV systems. The achievable statistical errors are considered by theoretical investigations and by experiments regarding detector noise as well as temporal and spatial scattered light fluctuations, e.g. due to speckles. An error propagation finally provides the determination of the noise power spectral density occurring as virtual turbulence in the measured turbulence spectra. It amounts to about 1.2 × 10?4 (m2 s?2) Hz?2 for mean flow velocities up to 40 m s?1 and 1 nW mean scattered light power per detector element. It rises for higher flow velocities in dependence on the flow turbulence. For the example of a nozzle flow with a mean velocity of 85 m s?1, which is disturbed by a cylinder, the final uncertainty is demonstrated to result in an effective bandwidth oflt in an effective bandwidth of the acquired turbulence spectra of 10 kHz and is thus sufficiently high for flow turbulence analysis. The measured velocity spectra agree well with comparison measurements using a hot-wire anemometer

  20. Photonic doppler velocimetry

    International Nuclear Information System (INIS)

    We are developing a novel fiber-optic approach to laser Doppler velocimetry as a diagnostic for high explosives tests. Using hardware that was originally developed for the telecommunications industry, we are able to measure surface velocities ranging from centimeters per second to kilometers per second. Laboratory measurements and field trials have shown excellent agreement with other diagnostics

  1. Experimental study of a vortex-shedding flowmeter

    Science.gov (United States)

    Thinh, Ngo D.; Howard, Robert M.

    1991-01-01

    A prototype of a vortex-shedding flowmeter with no moving parts is investigated for the loading of hypergolic fuels into the Space Shuttle Orbiter. Eliminating moving parts is intended to reduce the need for servicing the meter, and the vortex shedder is compared to the turbine flowmeter presently in use. A flow test loop is designed and employed to conduct experimental investigations in which the output characteristics are examined. The relationship between vortex frequency and flow rate is almost linear, as is the relationship between vortex shedding frequency and the Reynolds and Strouhal numbers. The results are consistent with calculations and suggest that the flowmeter is a possible replacement for measuring the loading of hypergols into the Space Shuttle Orbiter.

  2. Measurement of transitional flow in pipes using ultrasonic flowmeters

    Energy Technology Data Exchange (ETDEWEB)

    Zheng-Gang, Liu; Guang-Sheng, Du; Zhu-Feng, Shao; Qian-Ran, He; Chun-Li, Zhou, E-mail: lzhenggang@sdu.edu.cn [School of Energy and Power Engineering, Qian-Fo-shan campus, Shandong University, Jinan City 250061, Shandong Province (China)

    2014-10-01

    The accuracy of an ultrasonic flowmeter depends on the ratio k of average profile velocity of pipe and average velocity of an ultrasonic propagation path. But there is no appropriate method of calculating k for transition flow. In this paper, the velocity field of the transition flow in a pipe is measured by particle image velocimetry. On this basis, the k of U-shaped and V-shaped ultrasonic flowmeter is obtained when Reynolds number is between 2000 and 20?000. It is shown that the k is constant when the Reynolds number is in the range of 2000–2400 and 5400–20?000, and the k decreases with the increasing of Re when the Reynolds number is 2400–5400. The results of study can be used to improve the measurement accuracy of ultrasonic flowmeters when flow is transition flow and can provide help for the study of pipe flow. (paper)

  3. Measurement of transitional flow in pipes using ultrasonic flowmeters

    International Nuclear Information System (INIS)

    The accuracy of an ultrasonic flowmeter depends on the ratio k of average profile velocity of pipe and average velocity of an ultrasonic propagation path. But there is no appropriate method of calculating k for transition flow. In this paper, the velocity field of the transition flow in a pipe is measured by particle image velocimetry. On this basis, the k of U-shaped and V-shaped ultrasonic flowmeter is obtained when Reynolds number is between 2000 and 20?000. It is shown that the k is constant when the Reynolds number is in the range of 2000–2400 and 5400–20?000, and the k decreases with the increasing of Re when the Reynolds number is 2400–5400. The results of study can be used to improve the measurement accuracy of ultrasonic flowmeters when flow is transition flow and can provide help for the study of pipe flow. (paper)

  4. Study on the development of ultrasonic gas flowmeter

    International Nuclear Information System (INIS)

    Ultrasonic flowmeters have more advantages than the conventional method using pressure-difference. In these reasons, many advanced nations are already selling the commercial model. In RIST, we have been developed ultrasonic gas flow meter for the localization since a project was been contracted with POSCO in 1997. This paper describes a new ultrasonic gas flowmeter. This ultrasonic gas flowmeter is developed for accurate measurement of gases in a harsh environmental conditions. It is especially suited for measuring LDG, COG, BFG gases produced in iron and steel making process. In this study, we had developed the commercial model about the first tested model and applied a completed system to the POSCO gas line. Its performance has already well been proven by extensive field tests for several months in POSCO, iron and steel making company

  5. Measurement of blood flow velocity in a model of stenosis in vitro and in mesenteric vessels in vivo using non-invasive micro multipoint laser Doppler velocimetry

    International Nuclear Information System (INIS)

    Our research goal is to carry out two-dimensional (2D) and three-dimensional (3D) measurements of the velocity distribution within a single vessel. We modified a non-invasive beam laser Doppler velocimeter using near-infrared light, and linearized the laser to carry out simultaneous multipoint measurements. We also scanned the measurement line in the direction of depth to allow 3D imaging of vascular blood flow in opaque areas in vivo. We used micro multipoint laser Doppler velocimetry (LDV) and a device with improved spatial resolution from 250 to 125 µm. We compared actual and calculated values using a rotating disk with an attached microwire. To demonstrate the effectiveness of the proposed system, blood flowing at a constant rate through a glass capillary and the velocity distribution of flow in the capillary were measured and mapped. The average flow velocity was calculated from the cross-sectional area and flow rate in the glass capillary, and we compared the calculated and measured values. To obtain an image of blood flow velocity in vivo, we measured both 2D and 3D flow velocity distributions in mouse mesenteric vessels. (paper)

  6. Measurements of the electrophoretic mobility with a new laser Doppler cytopherometer (Lazypher) and critical evaluation of the electrophorese mobility-test (EMT)

    International Nuclear Information System (INIS)

    The new developed Laser Doppler Cytopherometer (Lazypher) allows the exact and objective measurement of the electrophoretic mobility of particles. Comparative experiments with the Free Flow Cell Electrophoresis instrument of Hannig showed identical results. The impression that the electrophoretic Mobility Test (EMT) is not valid for cancer diagnosis has been substantiated. But in its present form with the new instrument (Lazypher) possible improvements, e.g. isolation of lymphocytes, purification of antigens or indicator particles, can be estimated objectively for their value for the test system. (orig.)

  7. Random numbers free analytical implementation of Monte Carlo for laser-Doppler flowmetry at large interoptode spacing: application to human bone tissue.

    Science.gov (United States)

    Binzoni, Tiziano; Martelli, Fabrizio

    2015-03-20

    Classical Monte Carlo (MC) simulations for laser-Doppler flowmetry (LDF) often necessitate too long computation times and specialized hardware. This is particularly true for LDF at large interoptode spacing with low absorption coefficients and large anisotropic factors representing real biological tissues. For this reason, a random numbers free "analytical" implementation of the classical MC (MCan) is proposed. The MCan approach allows to obtain noise exempt LDF spectra in a short time and with a simple personal laptop. The proposed MCan holds for a diffusive regime of light propagation and it is practically implemented for a semi-infinite geometry. Its validity is demonstrated by comparisons with the classical MC. PMID:25968528

  8. In vivo Determination of Local Skin Optical Properties and Photon Path Length by Use of Spatially Resolved Diffuse Reflectance with Applications in Laser Doppler Flowmetry

    Science.gov (United States)

    Larsson, Marcus; Nilsson, Henrik; Strömberg, Tomas

    2003-01-01

    Methods for local photon path length and optical properties estimation, based on measured and simulated diffuse reflectance within 2 mm from the light source, are proposed and evaluated in vivo on Caucasian human skin. The accuracy of the methods was good (2% -7%) for path length and reduced scattering but poor for absorption estimation. Reduced scattering and absorption were systematically lower in the fingertip than in the forearm skin (633 nm). A maximum intrasite and interindividual variation of ~35% in an average photon path length was found. The methodology was applied in laser Doppler flowmetry, where path-length normalization of the estimated perfusion removed the optical property dependency.

  9. In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry

    OpenAIRE

    Larsson, Marcus; Nilsson, Henrik; Stro?mberg, Tomas

    2003-01-01

    Larsson, M., Nilsson, H. & Strömberg, T., In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry, 2003, Applied Optics, (42), 7-8, 124-134. http://dx.doi.org/10.1364/AO.42.000124. This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://ao.osa.or...

  10. An investigation of the motion of small particles as related to the formulation of zero gravity experiments. [experimental design using laser doppler velocimetry

    Science.gov (United States)

    Sastry, V. S.

    1980-01-01

    The nature of Brownian motion and historical theoretical investigations of the phenomemon are reviewed. The feasibility of using a laser anemometer to perform small particle experiments in an orbiting space laboratory was investigated using latex particles suspended in water in a plastic container. The optical equipment and the particle Doppler analysis processor are described. The values of the standard deviation obtained for the latex particle motion experiment were significantly large compared to corresponding velocity, therefore, their accuracy was suspect and no attempt was made to draw meaningful conclusions from the results.

  11. Integrated microfluidic flowmeter based on a micro-FBG inscribed in Co²?-doped optical fiber.

    Science.gov (United States)

    Liu, Zhengyong; Tse, Ming-Leung Vincent; Zhang, A Ping; Tam, Hwa-Yaw

    2014-10-15

    A novel microfluidic flowmeter integrated with microfiber Bragg grating (µFBG) is presented. Two glass capillaries and a short length of high-light-absorption Co²?-doped optical fiber were stacked inside a larger outer capillary tube. The stack was then drawn into a tapered device. Two microchannels with the diameter of ~50???m were formed inside the capillaries for flowing of microfluidics. An FBG was inscribed in the tapered Co²?-doped fiber with waist diameter of ~70???m, and acts as a flow-rate sensor. A pump laser with wavelength of 1480 nm was utilized to locally heat the µFBG, rendering the µFBG as miniature "hot-wire" flowmeter. The flow rate of the liquid in the microchannels is determined by the induced wavelength shift of the µFBG. The experimental results achieve a minimum detectable change of ~16??nL/s in flow rate, which is very promising in the use as part of biochips. PMID:25361108

  12. Study on the development and the application of ultrasonic gas flowmeter

    International Nuclear Information System (INIS)

    This paper describes tile development and the field application of the ultrasonic gas flowmeter for accurate measurement of the volumetric flow rate of gases in a harsh environmental conditions in iron and steel making company. This ultrasonic flowmeter is especially suited for measuring LDG, COG, BFG gases produced in iron and steel making process. This is a transit time type ultrasonic flowmeter. In this study, we have developed the signal processing algorithm for the transmitting and receiving method of ultrasonic wave and the ultrasonic signal processing to develop a transit time type ultrasonic flowmeter. We have evaluated the performance of ultrasonic flowmeter by the calibration system with Venturi type standard flowmeter. We has confirmed its reliability by extensive field tests for a year in POSCO, iron and steel making company. Now We have developed the commercial model of ultrasonic flowmeter and applied to the POSCO gas line.

  13. Effects of antipsoriatic treatment on cutaneous blood flow in psoriasis measured by 133Xe washout method and laser Doppler velocimetry

    International Nuclear Information System (INIS)

    In 8 patients with psoriasis vulgaris, the cutaneous blood flow (CBF) was measured simultaneously in both involved and uninvolved psoriatic skin before (i.e., on the first day of hospitalization) and on the 3rd, 7th, 14th, and 28th days of treatment with tar. The 133Xe washout method was used after epicutaneous labeling and compared to the laser Doppler velocimetry (LDV) technique. Control experiments were performed in 10 normal individuals. Before treatment the mean CBF in involved psoriatic skin was 62.6 +/- 18.7 SD ml X (100 g X min)-1, which is significantly higher than CBF of uninvolved skin in psoriatic patients, 9.5 +/- 4.0 SD ml X (100 g X min)-1, (p less than 0.01) and is 13.6 times higher than CBF in the normal individuals (p less than 0.01). Fifty hours following onset of treatment (i.e., after only 2 applications of tar), mean CBF of the involved psoriatic skin had decreased significantly to 35.0 +/- 13.9 SD ml X (100 g X min)-1, (p less than 0.01), which was not statistically different from the CBF on the 7th day. During the following weeks, the CBF in involved psoriatic skin decreased at a more moderate rate than that observed during the first week and was 15.0 +/- 6.1 SD ml X (100 g X min)-1 on the 28th day. This value is not significantly different from the CBF of uninvolved skin in these patients. At the end of treatment, the CBF of the uninvolved skin had decreased significantly (p less than 0.05) in all the patients to values similar to tin all the patients to values similar to those observed in the skin of normal individuals. A parallel decline was observed in a clinical psoriatic score index; however, it is not known whether the observed decrease in CBF was preceded or succeeded by the clinical improvement

  14. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Laura Butler

    2009-09-01

    A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag{sub 2}Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag{sub 2}Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3 {+-} 1.0 GPa. Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q{sub gas} is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag{sub 2}Ga nanoneedles is three times that of the MWNTs, the Ag{sub 2}Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag{sub 2}Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000. The epitaxial carbon that grows after heating (000{bar 1}) silicon carbide (SiC) to high temperatures (1450-1600) in vacuum was also studied. At these high temperatures, the surface Si atoms sublime and the remaining C atoms reconstruct to form graphene. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the quality of the few-layer graphene (FLG) surface. The XPS studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples. STM studies revealed a wide variety of nanometer-scale features that include sharp carbon-rich ridges, moire superlattices, one-dimensional line defects, and grain boundaries. By imaging these features with atomic scale resolution, considerable insight into the growth mechanisms of FLG on the carbon-face of SiC is obtained.

  15. Parameter optimization for Doppler laser cooling of a low-energy heavy ion beam at the storage ring S-LSR

    Science.gov (United States)

    Osaki, Kazuya; Okamoto, Hiromi

    2014-05-01

    S-LSR is a compact ion storage ring constructed at Kyoto University several years ago. The ring is equipped with a Doppler laser cooling system aimed at beam crystallization. Bearing in mind hardware limitations in S-LSR, we try to find an optimum set of primary experimental parameters for the production of an ultracold heavy ion beam. Systematic molecular dynamics simulations are carried out for this purpose. It is concluded that the detuning and spot size of the cooling laser should be chosen around -42 MHz and 1.5 mm, respectively, for the most efficient cooling of 40 keV ^{24}Mg^+ beams in S-LSR. Under the optimum conditions, the use of the resonant coupling method followed by radio-frequency field ramping enables us to reach an extremely low beam temperature on the order of 0.1 K in the transverse degrees of freedom. The longitudinal degree of freedom can be cooled to close to the Doppler limit; i.e., to the mK range. We also numerically demonstrate that it is possible to establish a stable, long one-dimensionally ordered state of ions.

  16. Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves / Velocimetria laser de escoamento permanente através de duas próteses cardíacas de duplo folheto

    Scientific Electronic Library Online (English)

    Ovandir, Bazan; Jayme Pinto, Ortiz; Francisco Ubaldo, Vieira Junior; Reinaldo Wilson, Vieira; Nilson, Antunes; Fabio Bittencourt Dutra, Tabacow; Eduardo Tavares, Costa; Orlando, Petrucci Junior.

    2013-12-01

    Full Text Available INTRODUÇÃO: A caracterização hidrodinâmica in vitro de próteses de válvulas cardíacas fornece informações importantes quanto ao seu funcionamento, sobretudo se realizada por meio de métodos não-invasivos de anemometria. Uma vez obtidos os perfis de velocidade para cada válvula, é possível compará-la [...] s quanto ao seu desempenho hidrodinâmico. Neste primeiro estudo experimental de anemometria laser com válvulas mecânicas, as simulações foram realizadas em bancada de testes para escoamento permanente. OBJETIVO: Comparar perfis de velocidade unidimensional no plano central de duas próteses aórticas de duplo folheto St. Jude (modelos AGN 21 - 751 e 21 AJ - 501) submetidas a um regime de fluxo permanente, para quatro seções distintas, três à jusante e uma à montante. MÉTODOS: Proporcionar condições de similaridade para o escoamento através de cada prótese, por meio de bancada hidrodinâmica para escoamento permanente (água, à vazão de 17 L/min.) e, por meio de anemometria laser unidimensional, obter os perfis de velocidades para as mesmas seções e varreduras. RESULTADOS: Verificou-se que as maiores velocidades correspondem à prótese de diâmetro interno menor e que as instabilidades do fluxo são maiores à medida que a seção de interesse encontra-se mais próxima da válvula. Também foram verificadas as regiões de recirculação, de estagnação do fluxo e de baixa pressão, além dos picos de velocidade para o escoamento em questão. CONCLUSÕES: Sob o aspecto hidrodinâmico e para todas as seções de interesse, foi possível concluir a preferência da válvula de modelo AGN 21 - 751 (RegentTM) sobre a 21 AJ - 501 (Master Series). Os resultados obtidos permitiram escolher, para os próximos trabalhos, um foco de estudo mais específico para regiões concretas dessas próteses. Abstract in english INTRODUCTION: In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hy [...] drodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. OBJECTIVE: To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. METHODS: To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min.) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. RESULTS: It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. CONCLUSIONS: Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.

  17. Doppler echocardiography

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, N.C.

    1985-01-01

    This text will serve to introduce the use of Doppler in clinical cardiology in a straightforward, practical format. The work features the following categories: a review and discussion of the fundamental principles and characteristics of ultrasound; examination techniques, including continuous and pulse modes; clinical application with acquired disease the focus; congenital disease, particularly defects, stenotic lesions, and complicated lesions; and fetal clinical applications of Doppler echocardiography.

  18. Doppler echocardiography

    International Nuclear Information System (INIS)

    This text will serve to introduce the use of Doppler in clinical cardiology in a straightforward, practical format. The work features the following categories: a review and discussion of the fundamental principles and characteristics of ultrasound; examination techniques, including continuous and pulse modes; clinical application with acquired disease the focus; congenital disease, particularly defects, stenotic lesions, and complicated lesions; and fetal clinical applications of Doppler echocardiography

  19. Method of assessing blood oxygenation in microcirculation vessels based on Doppler approach

    Science.gov (United States)

    Sokolov, Vladimir G.; Korsi, Larissa V.; Egorov, Sergei Y.

    2001-06-01

    Combination of laser Doppler flowmetry and pulse oximetry methods allows for the direct assessment of oxygen supply to tissues at the microcirculatory level, namely, in that part of the vascular network where the transcapillary exchange takes place that is responsible for saturating tissues with oxygen. The microcirculation system comprises arterial and venous microvascular parts that differ in blood flow velocities. Frequency separation of the photodetector signal components related to different velocity ranges makes possible to distinguish the hemodynamic processes in these two parts of the microvascular system. Moreover, numerous studies of collective oscillatory processes in hemodynamics reveal that cardio-oscillations are more pronounced in arterioles, whereas venous hemodynamics is mostly influenced by the breath rhythm. Taking account of the above phenomena allows developing a signal-filtration system for separate characterization of blood-oxygenation states in arterial and venous blood flows. Light absorbance in the skin depends on both light wavelength and blood-oxygenation level. Processing the signals obtained with a two-channel dual-wavelength (630 and 1115 nm) laser Doppler flowmeter provides information about blood oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygen consumption in tissues. In particular, this approach allows revealing pathogenic processes resulting from hyper- and hypo-oxygenation in tissues. For instance, rapidly growing malignant tumors are characterized by intensive metabolism, rapid formation of capillaries, and active transcapillary oxygen exchange that results in higher level of oxygen diffusion into tissue, while the level of oxygen is lowered in the microvascular veins.

  20. Izmerenie vektora skorosti lazernym dopplerovskim anemometrom (LDA s volokonno-opticheskimi traktami[Measurement of the velocity vector of the laser Doppler anemometer (LDA with fiber-optic tracts

    Directory of Open Access Journals (Sweden)

    S. N. Khotyaintsev

    1982-12-01

    Full Text Available The problems encountered in the development of laser Doppler velocity vector meter optical fiber paths. The scheme of the meter, including three-dimensional velocity meter made by differential circuit. Describes the experimental setup and the results of the experiment by measuring the two projections of the velocity vector.