WorldWideScience

Sample records for afterimage

  1. 'Mixing in' afterimage colors

    NARCIS (Netherlands)

    Lier, R.J. van; Vergeer, M.L.T.; Anstis, S.

    2008-01-01

    Coloured stimuli may reveal different afterimage colours at the same retinal location, depending on surface contours presented after the image (Van Lier and Vergeer, 2007 Perception 36 200 - 201). Here we demonstrate that the filling-in of the afterimage colour depends on the colours that are presen

  2. Continuous flash suppression reduces negative afterimages.

    Science.gov (United States)

    Tsuchiya, Naotsugu; Koch, Christof

    2005-08-01

    Illusions that produce perceptual suppression despite constant retinal input are used to manipulate visual consciousness. Here we report on a powerful variant of existing techniques, continuous flash suppression. Distinct images flashed successively at approximately 10 Hz into one eye reliably suppress an image presented to the other eye. The duration of perceptual suppression is at least ten times greater than that produced by binocular rivalry. Using this tool we show that the strength of the negative afterimage of an adaptor was reduced by half when it was perceptually suppressed by input from the other eye. The more completely the adaptor was suppressed, the more strongly the afterimage intensity was reduced. Paradoxically, trial-to-trial visibility of the adaptor did not correlate with the degree of reduction. Our results imply that formation of afterimages involves neuronal structures that access input from both eyes but that do not correspond directly to the neuronal correlates of perceptual awareness. PMID:15995700

  3. Luminance contours can gate afterimage colors and 'real' colors

    NARCIS (Netherlands)

    Anstis, S.; Vergeer, M.L.T.; Lier, R.J. van

    2012-01-01

    It has long been known that colored images may elicit afterimages in complementary colors. We have already shown (Van Lier, Vergeer, & Anstis, 2009) that one and the same adapting image may result in different afterimage colors, depending on the test contours presented after the colored image. The c

  4. Neural Correlates of an Auditory Afterimage in Primary Auditory Cortex

    OpenAIRE

    Noreña, A. J.; Eggermont, J. J.

    2003-01-01

    The Zwicker tone (ZT) is defined as an auditory negative afterimage, perceived after the presentation of an appropriate inducer. Typically, a notched noise (NN) with a notch width of 1/2 octave induces a ZT with a pitch falling in the frequency range of the notch. The aim of the present study was to find potential neural correlates of the ZT in the primary auditory cortex of ketamine-anesthetized cats. Responses of multiunits were recorded simultaneously with two 8-electrode arrays during 1 s...

  5. Visible light induced ocular delayed bioluminescence as a possible origin of negative afterimage

    CERN Document Server

    Bokkon, I; Wang, C; Dai, J; Salari, V; Grass, F; Antal, I

    2011-01-01

    The delayed luminescence of biological tissues is an ultraweak reemission of absorbed photons after exposure to external monochromatic or white light illumination. Recently, Wang, B\\'okkon, Dai and Antal (Brain Res. 2011) presented the first experimental proof of the existence of spontaneous ultraweak biophoton emission and visible light induced delayed ultraweak photon emission from in vitro freshly isolated rat's whole eye, lens, vitreous humor and retina. Here, we suggest that the photobiophysical source of negative afterimage can also occur within the eye by delayed bioluminescent photons. In other words, when we stare at a colored (or white) image for few seconds, external photons can induce excited electronic states within different parts of the eye that is followed by a delayed reemission of absorbed photons for several seconds. Finally, these reemitted photons can be absorbed by nonbleached photoreceptors that produce a negative afterimage. Although this suggests the photobiophysical source of negativ...

  6. Continuous flash suppression reduces negative afterimages

    OpenAIRE

    Tsuchiya, Naotsugu; Koch, Christof

    2005-01-01

    Illusions that produce perceptual suppression despite constant retinal input are used to manipulate visual consciousness. Here we report on a powerful variant of existing techniques, continuous flash suppression. Distinct images flashed successively at approx10 Hz into one eye reliably suppress an image presented to the other eye. The duration of perceptual suppression is at least ten times greater than that produced by binocular rivalry. Using this tool we show that the strength of the negat...

  7. Opposing effects of attention and consciousness on afterimages

    OpenAIRE

    van Boxtel, Jeroen J. A.; Tsuchiya, Naotsugu; Koch, Christof

    2010-01-01

    The brain's ability to handle sensory information is influenced by both selective attention and consciousness. There is no consensus on the exact relationship between these two processes and whether they are distinct. So far, no experiment has simultaneously manipulated both. We carried out a full factorial 2 × 2 study of the simultaneous influences of attention and consciousness (as assayed by visibility) on perception, correcting for possible concurrent changes in attention and consciousnes...

  8. Depressive Tendencies in Childhood and Adolescence as Defined by Process-Oriented Experiments.

    Science.gov (United States)

    Smith, Gudmund J. W.; Danielsson, Anna

    An attempt to operationally define depressive retardation in 72 inpatients aged 4-16 used two percept-genetic tests. In a serial visual afterimage (AI) test retardation was defined as a successive reduction of AI size, and in a serial tachistoscopic presentation using the meta-contrast technique (MCT) it was seen as stereotyped repetitions of…

  9. The 1996 architecture biennale: the unfulfilled promise of Hans Hollein's exhibition concept

    OpenAIRE

    Liefooghe, Maarten

    2012-01-01

    Despite its faint historical afterimage and its mystifying rhetoric about the individual architect as seismograph, the Venice architecture biennale of 1996 is worth reconsidering. This article argues that the exhibition's premise that architecture culture is marked by a growing individualisation remains relevant. It evaluates the no less problematic translation of this sharp observation into concrete decisions concerning the selection and presentation of 'individual positions' in this biennale.

  10. Method for 3D Rendering Based on Intersection Image Display Which Allows Representation of Internal Structure of 3D objects

    OpenAIRE

    Kohei Arai

    2013-01-01

    Method for 3D rendering based on intersection image display which allows representation of internal structure is proposed. The proposed method is essentially different from the conventional volume rendering based on solid model which allows representation of just surface of the 3D objects. By using afterimage, internal structure can be displayed through exchanging the intersection images with internal structure for the proposed method. Through experiments with CT scan images, the proposed met...

  11. 'Flight of colours' in lesions of the visual system.

    Science.gov (United States)

    Feldman, M; Todman, L; Bender, M B

    1974-11-01

    A bright pocket flashlight was directed into one eye for 10 seconds; the subject then closed the eyelids and reported the sequence of after-image colours observed. Lesions of the visual system which compromised bilateral central colour vision also reduced or abolished the `flight of colours'. This simple bedside test of each eye independently is of value in detecting mild defects of central vision. PMID:4457619

  12. Mystery of the anti-McCollough effect.

    Science.gov (United States)

    Bedford, Felice L

    2011-10-01

    The McCollough Effect (ME) is a complex perceptual aftereffect that remains of interest half a century after its discovery. It is argued that a recently reported variant, dubbed the anti-McCollough effect, is not the reverse of the ME, with aftereffect colors in the same direction as the inducing stimuli. A red-horizontal stimulus leads to a reddish aftereffect not because of red-horizontal parings, but despite them. The anti-ME is a weak standard-direction ME produced by complementary afterimage colors (afterimage green with horizontal), rather than by environmental colors, first shown decades ago. It is not a new type of contingent aftereffect. The red-horizontal pair does not interfere with the afterimage green-horizontal pair it produces because a single color-orientation pairing provides more ambiguous input than does the standard two orientation-color pairings (red-horizontal, green-vertical) of the ME. It is also argued that not even one orientation-contingent color aftereffect is convincingly shown in the "anti"-ME, let alone, as has previously been suggested, two simultaneous orientation-contingent color aftereffects in opposite directions at different levels of the visual system, in which the higher-level effect suppresses the downstream effect from reaching consciousness. The "anti"-ME can be explained by existing theories of contingent aftereffects, including perceptual-learning theory. PMID:21691903

  13. Temporary blinding from bright light sources as a significant impact on occupational safety and health

    International Nuclear Information System (INIS)

    Low power laser and high-brightness LEDs (HB-LEDs) have been applied in specially developed and computer assisted test setups in order to determine the duration and progression of colours in afterimages, the disturbance of visual acuity as well as the impairment of colour and contrast vision. Interrelationships between wavelength, exposure duration, optical power and energy have been investigated. Afterimage durations up to 300 seconds were found if the fovea of the human retina is irradiated from a laser beam at less than 30 μW, whereas lower values are valid in the Parafoveal region and in the periphery. The visual acuity was strongly reduced during about 30 % of the afterimage time. The time-dependent progression of the afterimage colours was determined for 4 different dominant wavelengths of HB-LEDs, i.e. 455 nm, 530 nm, 590 nm and 625 nm, in the power range between 0.05 m W and 0.5 m W for exposure durations between 0.5 s and 5 s. The flight of colours obtained with 5 test persons is given as 8-bit RGB-values and illustrated as a function of the applied optical energy in the CIE chromaticity diagram together with the respective total afterimage durations. The colour contrast capability was investigated for 3 volunteers with specially developed test charts in 7 colours, namely without and after glare from 4 coloured high-brightness LEDs. Each subject completed 56 time-consuming tests since adequate adaptation was necessary between the respective tests. Glare increases the identification times about 14 s and 16 s and even stronger impairment is observable especially at low colour contrast. Tests with 40 subjects and 4 different pseudoisochromatic colour plates have shown that colour vision was impaired for periods between 27 s and 186 s depending on the applied colour plate and respective LED colour. Such relatively long lasting visual disturbances could be of particular concern connected with performing safety critical operations such as working with machines

  14. Disturbance of visual functions as a result of temporary blinding from low power lasers

    Science.gov (United States)

    Reidenbach, Hans-Dieter

    2010-04-01

    Although it is well-known that dazzle, flash-blindness and afterimages may be caused by bright optical radiation, only sparse quantitative data are available with regard to the effects arising from low power laser products. Indirect effects like temporary blinding might result in serious incidents or even accidents due to the alteration of visual functions like visual acuity, contrast sensitivity and color discrimination. In order to determine the degree and duration of impairment resulting from dazzle, flash-blindness and afterimages, caused by a laser beam, an investigation has been performed with the goal to improve the current knowledge as far as especially the visual acuity recovery duration is concerned. Two different test set-ups were designed and applied in order to determine the afterimage duration and the recovery time for visual acuity after temporary blinding from a laser, respectively. In order to get the desired information a helium-neon laser was mounted on a movable assembly where the respective beam position and direction could be set up on a semicircle. In addition the mount could be inclined in a vertical plane in order to increase the variability of feasible settings. The power was adjusted in several steps in order to investigate the respective dependence of the afterimage. The investigations were relatively time consuming, since re-adaptation of about half an hour was necessary after every exposure in order not to falsify the results. The trials have been done with several volunteers in the laboratory. After the experimental mapping of the local afterimage duration for the various sites on the retina the foveal afterimage duration taf,fv produced by a red laser beam was determined. The investigations have shown a strong dependence on the angle between the line of sight and the beam direction. Besides a maximum of 300 s the dose relationship taf,fv/s ~ 50.6•ln[(P•texp)/μJ] - 13.4 for laser output powers P between 10 μW and 30 μW with

  15. How Were Eye Movements Recorded Before Yarbus?

    Science.gov (United States)

    Wade, Nicholas J

    2015-01-01

    Alfred Yarbus introduced a new dimension of precision in recording how the eyes moved, either when attempts were made to keep them stationary or when scanning pictures. Movements of the eyes had been remarked upon for millennia, but recording how they move is a more recent preoccupation. Emphasis was initially placed on abnormalities of oculomotor function (like strabismus) before normal features were considered. The interest was in where the eyes moved to rather than determining how they got there. The most venerable technique for examining ocular stability involved comparing the relative motion between an afterimage and a real image. In the late 18th century, Wells compared afterimages generated before body rotation with real images observed following it when dizzy; he described both lateral and torsional nystagmus, thereby demonstrating the directional discontinuities in eye velocities. At around the same time Erasmus Darwin used afterimages as a means of demonstrating ocular instability when attempting to fixate steadily. However, the overriding concern in the 19th century was with eye position rather than eye movements. Thus, the characteristics of nystagmus were recorded before those of saccades and fixations. Eye movements during reading were described by Hering and by Lamare (working in Javal's laboratory) in 1879; both used similar techniques of listening (with tubes placed over the eyelids) to the sounds made during contractions of the extraocular muscles. Photographic records of eye movements during reading were made by Dodge early in the 20th century, and this stimulated research using a wider array of patterns. Eye movements over pictures were examined by Stratton and later by Buswell, who drew attention to the effects of instructions on the pattern of eye movements. In midcentury, attention shifted back to the stability of the eyes during fixation, with the emphasis on involuntary movements. The suction cap methods developed by Yarbus were applied

  16. Method for 3D Rendering Based on Intersection Image Display Which Allows Representation of Internal Structure of 3D objects

    Directory of Open Access Journals (Sweden)

    Kohei Arai

    2013-06-01

    Full Text Available Method for 3D rendering based on intersection image display which allows representation of internal structure is proposed. The proposed method is essentially different from the conventional volume rendering based on solid model which allows representation of just surface of the 3D objects. By using afterimage, internal structure can be displayed through exchanging the intersection images with internal structure for the proposed method. Through experiments with CT scan images, the proposed method is validated. Also one of other applicable areas of the proposed for design of 3D pattern of Large Scale Integrated Circuit: LSI is introduced. Layered patterns of LSI can be displayed and switched by using human eyes only. It is confirmed that the time required for displaying layer pattern and switching the pattern to the other layer by using human eyes only is much faster than that using hands and fingers.

  17. Apparent rotation and jazzing in Leviant's Enigma illusion.

    Science.gov (United States)

    Hamburger, Kai

    2007-01-01

    In 1981 Leviant devised Enigma, a figure that elicits perceived rotary motion in the absence of real motion. However, despite its striking appearance there is no good explanation for this motion illusion to date. Gregory (1993 Proceedings of the Royal Society of London B 253 123) pointed out a similarity to MacKay's 'complementary' afterimage in his ray pattern and suggested accommodative fluctuations and small eye movements as a potential origin for these phenomena. Furthermore, Zeki et al (1993 Proceedings of the Royal Society of London B 252 215-222) found PET-activation in response to Enigma in visual area V5 and immediately surrounding areas (called V5 complex) suggesting that the illusory motion could be mediated by the same neurons as real motion. In the experiments reported here, I show that the rotary motion is perceived on coloured as well as achromatic annuli intercepting the radial lines. More importantly, the illusory streaming motion continues to be seen with a cycloplegic lens as well as through a pinhole (ie ruling out transient changes of accommodation), and in the positive after-image (ie in the absence of eye movements). Apparent rotation is strongest with radial inducers impinging at right angles onto the annuli, but persist, although to a lesser degree, when the inducing lines are tilted in opposite directions, non-collinear, or replaced by dotted lines or lines with rounded terminators. For an explanation, the Enigma illusion requires a neural mechanism that uses lines abutting an empty annulus to elicit orthogonal streaming motion in one or the other direction. PMID:17718359

  18. Follow-up of hearing thresholds among forge hammering workers

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, A.A.; Mikael, R.A.; Faris, R. (Ain Shams Univ., Abbasia, Cairo (Egypt))

    1989-01-01

    Hearing threshold was reexamined in a group of forge hammering workers investigated 8 years ago with consideration of the age effect and of auditory symptoms. Workers were exposed to impact noise that ranged from 112 to 139 dB(A)--at an irregular rate of 20 to 50 drop/minute--and a continuous background noise that ranged from 90 to 94 dB(A). Similar to what was observed 8 years ago, the present permanent threshold shift (PTS) showed a maximum notch at the frequency of 6 kHz and considerable elevations at the frequencies of 0.25-1 kHz. The age-corrected PTS and the postexposure hearing threshold were significantly higher than the corresponding previous values at the frequencies 0.25, 0.5, 1, and 8 kHz only. The rise was more evident at the low than at the high frequencies. Temporary threshold shift (TTS) values were significantly less than those 8 years ago. Contrary to the previous TTS, the present TTS were higher at low than at high frequencies. Although progression of PTS at the frequencies 0.25 and 0.5 kHz was continuous throughout the observed durations of exposure, progression at higher frequencies occurred essentially in the first 10 to 15 years of exposure. Thereafter, it followed a much slower rate. Tinnitus was significantly associated with difficulty in hearing the human voice and with elevation of PTS at all the tested frequencies, while acoustic after-image was significantly associated with increment of PTS at the frequencies 0.25-2 kHz. No relation between PTS and smoking was found. PTS at low frequencies may provide an indication of progression of hearing damage when the sensitivity at 6 and 4 kHz diminishes after prolonged years of exposure. Tinnitus and acoustic after-image are related to the auditory effect of forge hammering noise.

  19. Are there multiple visual short-term memory stores?

    Directory of Open Access Journals (Sweden)

    Ilja G Sligte

    Full Text Available BACKGROUND: Classic work on visual short-term memory (VSTM suggests that people store a limited amount of items for subsequent report. However, when human observers are cued to shift attention to one item in VSTM during retention, it seems as if there is a much larger representation, which keeps additional items in a more fragile VSTM store. Thus far, it is not clear whether the capacity of this fragile VSTM store indeed exceeds the traditional capacity limits of VSTM. The current experiments address this issue and explore the capacity, stability, and duration of fragile VSTM representations. METHODOLOGY/PRINCIPAL FINDINGS: We presented cues in a change-detection task either just after off-set of the memory array (iconic-cue, 1,000 ms after off-set of the memory array (retro-cue or after on-set of the probe array (post-cue. We observed three stages in visual information processing 1 iconic memory with unlimited capacity, 2 a four seconds lasting fragile VSTM store with a capacity that is at least a factor of two higher than 3 the robust and capacity-limited form of VSTM. Iconic memory seemed to depend on the strength of the positive after-image resulting from the memory display and was virtually absent under conditions of isoluminance or when intervening light masks were presented. This suggests that iconic memory is driven by prolonged retinal activation beyond stimulus duration. Fragile VSTM representations were not affected by light masks, but were completely overwritten by irrelevant pattern masks that spatially overlapped the memory array. CONCLUSIONS/SIGNIFICANCE: We find that immediately after a stimulus has disappeared from view, subjects can still access information from iconic memory because they can see an after-image of the display. After that period, human observers can still access a substantial, but somewhat more limited amount of information from a high-capacity, but fragile VSTM that is overwritten when new items are presented

  20. Hazards in air-, rail-, and road traffic arising from laserpointers; Gefaehrdungen des Luft-, Schienen- und Strassenverkehrs durch Laserpointer

    Energy Technology Data Exchange (ETDEWEB)

    Reidenbach, H.D. [Fachhochschule Koeln (Germany). Forschungsschwerpunkt Medizintechnik und Nichtionisierende Strahlung; Deutsch-Schweizerischer Fachverband fuer Strahlenschutz e.V., Garching (Germany). Arbeitskreis Nichtionisierende Strahlung (AKNIR)

    2012-07-01

    Visible laser radiation with sufficient irradiance or radiant exposure might result in permanent damage of the eyes especially in the retina. In order to prevent this exposure limit values have been established based on current scientific knowledge. In addition visible laser radiation might result in effects like temporary blinding at even much lower exposure values. In this case irritations, flash-blindness and afterimages appear whose extent might exceed the respective damage level while vision is temporarily compromised in critical visual tasks more or less. The easy accessibility of hand-held laser products (laser pointers) with relatively high power might result in a modification of the security situation especially in air traffic via thoughtless and careless use of such products or in terroristic acts. In addition an increasing number of incidents in rail and road traffic where not only temporary blinding might be anticipated but permanent damage of the eyes as a result of overexposure due to laser pointer irradiation cannot be excluded any longer. Using laser pointers, which are available on the market in the power range up to 1 watt and at different wavelengths new hazard scenarios and threats with serious consequences are possible. Here the radiation protection is in great demand. (orig.)

  1. Removing the remaining ridges in fingerprint segmentation

    Institute of Scientific and Technical Information of China (English)

    ZHU En; ZHANG Jian-ming; YIN Jian-ping; ZHANG Guo-min; HU Chun-feng

    2006-01-01

    Fingerprint segmentation is an important step in fingerprint recognition and is usually aimed to identify non-ridge regions and unrecoverable low quality ridge regions and exclude them as background so as to reduce the time expenditure of image processing and avoid detecting false features. In high and in low quality ridge regions, often are some remaining ridges which are the afterimages of the previously scanned finger and are expected to be excluded from the foreground. However, existing segmentation methods generally do not take the case into consideration, and often, the remaining ridge regions are falsely classified as foreground by segmentation algorithm with spurious features produced erroneously including unrecoverable regions as foreground. This paper proposes two steps for fingerprint segmentation aimed at removing the remaining ridge region from the foreground. The non-ridge regions and unrecoverable low quality ridge regions are removed as background in the first step, and then the foreground produced by the first step is further analyzed for possible remove of the remaining ridge region. The proposed method proved effective in avoiding detecting false ridges and in improving minutiae detection.

  2. Hazards in air-, rail-, and road traffic arising from laserpointers

    International Nuclear Information System (INIS)

    Visible laser radiation with sufficient irradiance or radiant exposure might result in permanent damage of the eyes especially in the retina. In order to prevent this exposure limit values have been established based on current scientific knowledge. In addition visible laser radiation might result in effects like temporary blinding at even much lower exposure values. In this case irritations, flash-blindness and afterimages appear whose extent might exceed the respective damage level while vision is temporarily compromised in critical visual tasks more or less. The easy accessibility of hand-held laser products (laser pointers) with relatively high power might result in a modification of the security situation especially in air traffic via thoughtless and careless use of such products or in terroristic acts. In addition an increasing number of incidents in rail and road traffic where not only temporary blinding might be anticipated but permanent damage of the eyes as a result of overexposure due to laser pointer irradiation cannot be excluded any longer. Using laser pointers, which are available on the market in the power range up to 1 watt and at different wavelengths new hazard scenarios and threats with serious consequences are possible. Here the radiation protection is in great demand. (orig.)

  3. Robust Foreground Detection: A Fusion of Masked GreyWorld, Probabilistic Gradient Information and Extended Conditional Random Field Approach

    Directory of Open Access Journals (Sweden)

    David Rawlinson

    2012-05-01

    Full Text Available Foreground detection has been used extensively in many applications such as people counting, traffic monitoring and face recognition. However, most of the existing detectors can only work under limited conditions. This happens because of the inability of the detector to distinguish foreground and background pixels, especially in complex situations. Our aim is to improve the robustness of foreground detection under sudden and gradual illumination change, colour similarity issue, moving background and shadow noise. Since it is hard to achieve robustness using a single model, we have combined several methods into an integrated system. The masked grey world algorithm is introduced to handle sudden illumination change. Colour co-occurrence modelling is then fused with the probabilistic edge-based background modelling. Colour co-occurrence modelling is good infiltering moving background and robust to gradual illumination change, while an edge-based modelling is used for solving a colour similarity problem. Finally, an extended conditional random field approach is used to filter out shadow and afterimage noise. Simulation results show that our algorithm performs better compared to the existing methods, which makes it suitable for higher-level applications.

  4. True Detective Stories: Media Textuality and the Anthology Format between Remediation and Transmedia Narratives

    Directory of Open Access Journals (Sweden)

    Cristina Demaria

    2014-12-01

    Full Text Available Through the analysis of the recent HBO first season TV series True Detective (2014-, the essays focuses on the renewed anthology format of contemporary seriality as a way to inscribe the form of the novel in the transmedia imagination and its narrative models. While the first part of the essay concentrates on Media and Literary Studies’ debates on the statute of media texts, their materiality and the transformations of their contents in the participatory and convergent culture of prosumers, the second part is devoted to an in-depth reading of some of the main features of True Detective’s first season: from the ways it remediates many other genres and media, to how – as an audiovisual sychretyc text -  it plays with dialogues, cinematography, music and its temporal, spatial and seeing enunciative strategies and positions in order to construct a (quasidystopic narrative of America as an after-image, or, better, a post-collapse America and its Southern Gothic landscapes. In the lst paragraph, this writing briefly engages with how this particular format of TV series helps developing narrative models that fan we bpages and fanfic archives are still struggling not so much to comprehend, but to actually transform into an expanded textuality  able to tell a more ‘true’ story.

  5. New methods in order to determine the extent of temporary blinding from laser and LED light and proposal how to allocate into blinding groups

    Science.gov (United States)

    Reidenbach, Hans-Dieter; Ott, Günter; Brose, Martin; Dollinger, Klaus

    2010-02-01

    Indirect effects arising from bright artificial optical sources like temporary blinding might result in serious incidents or even accidents due to accompanying alteration of visual functions like visual acuity, contrast sensitivity and color discrimination. In order to determine the degree and duration of impairment resulting from glare, dazzle, flash-blindness and afterimages, caused by a beam from a laser or lamp product, particularly under low ambient light conditions, an investigation has been performed with the goal to improve the current knowledge as far as especially recovery duration of visual acuity is concerned. For this two different test set-ups were designed and engineered in order to be able to determine the time duration after which visual acuity returns to its previous value after temporary blinding with a laser or an LED and in addition to search for functional relations as far as wavelength, optical power and exposure duration are concerned. Instead of normal visual acuity measurement, which is the standard test done by eye care professionals, and which has been applied in order to determine the recovery time after irradiation with a high brightness LED (HB-LED) with the aid of a modified commercially available binoptometer with Landolt-C rings as optotypes, a special reading test on a computer monitor was developed for the case of laser irradiation. Two different laser were applied, one with a wavelength of 632.8 nm and the other with 532 nm. Red, green, royal blue and white HB-LEDs were used as stimulating light sources. The maximum applied optical power in a 7-mm aperture, which is equivalent to the pupil diameter of a dark adapted eye, was 0.783 mW (laser) and 3 mW (LED). The exposure durations were chosen as 0.25 s, 0.5 s, 1 s, 5 s, and 20 s in the case of laser irradiation and 0.25 s, 1 s, 5 s, and 10 s for LEDs, respecting maximum permissible exposure (MPE) and/or limit exposure levels (ELVs) in all exposure situations. The visual acuity

  6. Analysis of Multipath Pixels in SAR Images

    Science.gov (United States)

    Zhao, J. W.; Wu, J. C.; Ding, X. L.; Zhang, L.; Hu, F. M.

    2016-06-01

    As the received radar signal is the sum of signal contributions overlaid in one single pixel regardless of the travel path, the multipath effect should be seriously tackled as the multiple bounce returns are added to direct scatter echoes which leads to ghost scatters. Most of the existing solution towards the multipath is to recover the signal propagation path. To facilitate the signal propagation simulation process, plenty of aspects such as sensor parameters, the geometry of the objects (shape, location, orientation, mutual position between adjacent buildings) and the physical parameters of the surface (roughness, correlation length, permittivity)which determine the strength of radar signal backscattered to the SAR sensor should be given in previous. However, it's not practical to obtain the highly detailed object model in unfamiliar area by field survey as it's a laborious work and time-consuming. In this paper, SAR imaging simulation based on RaySAR is conducted at first aiming at basic understanding of multipath effects and for further comparison. Besides of the pre-imaging simulation, the product of the after-imaging, which refers to radar images is also taken into consideration. Both Cosmo-SkyMed ascending and descending SAR images of Lupu Bridge in Shanghai are used for the experiment. As a result, the reflectivity map and signal distribution map of different bounce level are simulated and validated by 3D real model. The statistic indexes such as the phase stability, mean amplitude, amplitude dispersion, coherence and mean-sigma ratio in case of layover are analyzed with combination of the RaySAR output.

  7. Pavlovian conditioning with proximal stimuli.

    Science.gov (United States)

    Lachnit, H; Bohn, A

    1986-01-01

    This experiment was conducted with the objective of demonstrating that the effective stimuli in Pavlovian Conditioning are not environmental stimuli but internal physiological processes elicited by environmental input (proximal stimuli). In order to achieve the objective, afterimages in color vision were used: looking at a diffuse lightened circle after seeing a red circle yields an image of a green circle. A differential conditioning paradigm with two sequential compounds was run. In one group (G+B-: n1 = 10), a red circle followed by a green circle was paired with shock, whereas a red circle followed by a blue circle remained unpaired. A second group (G-B+: n2 = 10) received red-blue paired trials and unpaired red-green trials. Immediately after that training, subjects were tested with a new, never trained sequential compound: a red circle followed by a diffuse lightened circle. Furthermore, they were tested with the already trained compounds. Taking the environmental point of view, the never trained stimulus should elicit an orienting response lying in between the excitatory reaction to the paired stimulus and the inhibitory reaction to the unpaired stimulus. From the proximal point of view, the diffuse light should elicit an excitatory reaction in group G+B- and an inhibitory reaction in group G-B+. Electrodermal conditioned anticipatory and omission responses were measured. The results supported the proximal hypothesis. Hence, defining input in environmental terms may be the wrong way. Instead, in conceptualizing the stimulus in conditioning, the following should be considered: the processing organism itself is creating the effective stimuli. PMID:3785989

  8. In Search of Lost Community: The Literary Image between “Proust” and “Baudelaire” in Walter Benjamin’s Modernization Lament

    Directory of Open Access Journals (Sweden)

    Karyn Ball

    2015-02-01

    Full Text Available This essay takes up the encounter between philosophy and literature through a reconsideration of Walter Benjamin’s remarks from “On Some Motifs in Baudelaire” about Henri Bergson’s Matière et mémoire as an attempt “[t]owering above” other ventures into Lebensphilosophie to “lay hold of the ‘true’ experience, as opposed to the kind that manifests itself in the standardized, denatured life of the civilized masses”. Despite his initial affirmation of Bergson’s understanding of experience as connected with tradition, Benjamin criticizes the philosopher’s account for sidestepping “the alienating, blinding experience of the age of large-scale industrialism” in reaction to which, as Benjamin insists, Bergson’s philosophy of memory developed. Yet even as Bergson shuts out the historical import of modernization, according to Benjamin, he also spotlights a “complementary” visual experience “in the form of its spontaneous afterimage”. Benjamin subsequently defines Bergson’s philosophy as “an attempt to specify this afterimage and fix it as a permanent record”, an endeavor that inadvertently “furnishes a clue to the experience which presented itself undistorted to Baudelaire’s eyes, in the figure of his reader”. If the literary critic might be viewed here as weighing in on a long-running antagonism between philosophy and literature, then his assessment is resolute: by praising the self-conscious historicity of Baudelaire’s lyric, Benjamin declares that poetry succeeds where Lebensphilosophie fails. Notably, Baudelaire is not the only figure to upstage “ahistorical” Bergson, since Marcel Proust and Sigmund Freud facilitate this victory. To contextualize the second section of “Motifs”, where Benjamin discusses the novelist’s “immanent critique of Bergson” this essay offers a reading of “On the Image of Proust” as a propadeutic to Benjamin’s privileging of “Baudelaire” over

  9. 不同时距条件下面孔表情知觉的时间整合效应%Temporal Integration Effects in Facial Expression Recognition in Different Temporal Duration Condition

    Institute of Scientific and Technical Information of China (English)

    陈本友; 黄希庭

    2012-01-01

    通过把面孔表情分割成三部分,按照不同的时间间隔以及不同的呈现时间相继呈现,考察了被试对面孔表情的时间整合效果,以此探讨时间整合的加工过程和影响因素。结果发现:(1)面孔表情的时间整合效果受时间结构和刺激材料的影响。(2)分离呈现的面孔表情能否进行时间整合与S0A的大小有关。(3)面孔表情的时间整合存在类型差异。(4)面孔表情的时间整合是在一个有限的视觉缓冲器内进行的,图像记忆和长时记忆与面孔表情的时间整合过程关系密切。%Temporal integration is the process of perception processing,in which the successively separated stimuli are combined into a significant representation.It is a complicated process,which is known to be influenced by multiple factors,such as the temporal structure and stimulus components.Although this process has been explored in inter-stimulus interval in face perception,little is known about the temporal integration effect in facial expression recognition.More importantly,there has been no relevant evidence demonstrating that stimulus duration and stimulus category can affect the temporal integration of facial expression. In the present study,the part-whole judgment task was used to examine the influencing factors of temporal integration in the facial expression.In two experiments,each of three whole facial expression pictures was segmented into three parts,and each including a salient facial feature:eye,nose,or mouth.These parts were presented sequentially to the participants by some interval or presentation durations, with a fixed sequence:eye part first,nose followed,and mouth last.Following the last part,a mask,which eliminated effects of afterimages or other types of visual persistence was displayed.Then,participants were asked to judge the category of the facial expression, by pressing one of three number keys;"1","2" and "3",corresponding to anger,happy and