Showing papers by "Eli Peli published in 2001"

Vision multiplexing: an engineering approach to vision rehabilitation device development.

Abstract: Multiplexing is the transmission of two or more messages simultaneously over the same communication channel in a way that enables them to be separated and used at the receiving end. The normal visual system provides us with a very wide field of view at an apparent high resolution. The wide field of view is continuously monitored at a low resolution, providing information for navigation and detection of objects of interest. These objects of interest are sampled over time using the high-resolution fovea. Most disabling visual conditions impact only one of the components, the peripheral low-resolution wide field or the central high-resolution fovea. The loss of one of these components prevents the interplay of central and peripheral vision needed for normal function and causes disability. Traditionally low-vision aids replace or supplement the missing function, but usually at a cost of a significant loss in the surviving function. For example, magnifying devices increase resolution but reduce the field of view, whereas minifying devices increase the field of view but reduce resolution. A proposal to resolve many of the problems of current visual aids by exploring a general engineering approach--vision multiplexing--that takes advantage of the dynamic nature of human vision is presented. Vision multiplexing seeks to provide both the wide field of view and the high-resolution information in ways that could be accessed and interpreted by the visual system. This paper describes the use of optical methods and computer technologies in the development of a number of new visual aids, all of which apply vision multiplexing to restore the interplay of central and peripheral vision using eye movements in a natural way.

Contrast sensitivity function and image discrimination.

Abstract: A previous study tested the validity of simulations of the appearance of a natural image (from different observation distances) generated by using a visual model and contrast sensitivity functions of the individual observers [J. Opt. Soc. Am. A 13, 1131 (1996)]. Deleting image spatial-frequency components that should be undetectable made the simulations indistinguishable from the original images at distances larger than the simulated distance. The simulated observation distance accurately predicted the distance at which the simulated image could be discriminated from the original image. Owing to the 1/f characteristic of natural images' spatial spectra, the individual contrast sensitivity functions (CSF's) used in the simulations of the previous study were actually tested only over a narrow range of retinal spatial frequencies. To test the CSF's over a wide range of frequencies, the same simulations and testing procedure were applied to five contrast versions of the images (10-300%). This provides a stronger test of the model, of the simulations, and specifically of the CSF's used. The relevant CSF for a discrimination task was found to be obtained by using 1-octave Gabor stimuli measured in a contrast detection task. The relevant CSF data had to be measured over a range of observation distances, owing to limitations of the displays.

Luminance artifacts of cathode-ray tube displays for vision research.

Abstract: Phosphor persistence, video bandwidth, DC restoration and high-voltage regulation affect the appearance of images presented on cathode-ray tubes (CRTs), potentially resulting in differences between nominal and actual stimuli. We illustrate these effects by measuring physical parameters of horizontal and vertical static and counter-phase flickering gratings, and we illustrate problems for vision research by measuring contrast sensitivity to these gratings. We also measured the extent to which calibration protocols actually result in the monitor being calibrated over its entire area regardless of image size. The results of our physical measurements indicate substantial differences between gratings that nominally differ only as to orientation. Consistent with these differences, our psychophysical measurements indicate different sensitivities when the bars of the gratings are parallel or orthogonal to raster lines, regardless of the retinal orientation of the gratings. The results of our calibration check show that only a small region around the target area of calibration can be regarded as effectively linearized, and only if the size of the test image used during the check is similar to the size of the calibration patch. Overall, our results indicate potentially severe problems with the use of CRTs in vision research, and we discuss some published results that are likely to have been affected by these problems.

Appearance of images through a multifocal intraocular lens

Abstract: The appearance of images through a multifocal intraocular lens (IOL) was simulated. The optical transfer function (OTF) of a model eye containing the multifocal lens was measured and divided by the OTF of the model eye with a monofocal IOL. This ratio was used to filter digital images, generating simulations that represent the retinal images seen through a multifocal intraocular lens when viewed through an eye with a monofocal lens. A dichoptic side-by-side display was used to present the original image to one eye, implanted with the multifocal lens, while the other eye, implanted with monofocal lens, viewed the simulations and variations on the simulations to derive a point of subjective equivalence. Four subjects with such bilateral lens implants were tested for near and distance vision. The results validate the test methodology and the simulations. Referenced to the nominal theoretical filter, the prediction was within a 0.25-diopter (D) blur for distance simulation and within a 0.50-D blur for the near-vision simulation.

P-16: Augmented View for Tunnel Vision: Device Testing by Patients in Real Environments

Abstract: ion device for patients with severely restricted peripheral visual field (tunnel vision) was proposed, combining a see-through HMD and minified contour detection. Implemented commercial off-the-shelf (COTS) configurations were tested in real environments by Retinitis Pigmentosa patients and normally sighted subjects. 1. Objective and Background

Discrimination of wide-field images as a test of a peripheral-vision model.

Abstract: In order to test a model of peripheral vision, various contrast sensitivity functions (CSF's) and fundamental eccentricity constants (FEC's) [see J. Opt. Soc. Am. A 8, 1762 (1991)] were applied to real-world, wide-field (6.4 degrees-32 degrees eccentricity) images. The FEC is used to model the change in contrast sensitivity as a function of retinal eccentricity. The processed test images were tested perceptually by determining the threshold FEC for which the observers could discriminate the test images from the original image. It was expected that higher CSF sensitivity would be associated with higher FEC's; and in fact, for images processed with low-pass (variable-window stimuli) CSF's, the threshold FEC's were larger for the higher-sensitivity (pattern-detection) CSF than for the lower-sensitivity (orientation detection) CSF. When two higher-sensitivity CSF's were compared, the bandpass (constant-window stimuli) CSF resulted in essentially the same FEC threshold as did the low-pass (variable-window stimuli) CSF. The fact that the FEC compensated for complex differences in the form of the CSF suggested that the discrimination task was mediated by a limited range of spatial frequencies over which the two CSF's were similar. Image contrast was then varied in order to extend the range of spatial frequencies tested. The FEC's estimated with the lower-contrast test images were unchanged for test images obtained with the high-sensitivity, bandpass CSF but increased for test images obtained with the high-sensitivity, low-pass CSF. These results suggest that peripheral contrast sensitivity as used in the present discrimination task is based on a high-sensitivity, bandpass CSF. The peripheral-vision model validated by the present analysis has practical applications in the evaluation of wide-field simulator images as well as area-of-interest or other foveating systems.

53.2: A Binocular Stereoscopic Display System with Coupled Convergence and Accommodation Demands

Abstract: Conflict between the accommodation and convergence demand in stereo display systems has been implicated as a cause of perceptual error (failure of size constancy), discomfort and visual system changes. A novel method is proposed for such displays, which, by utilizing a measured object of fixation can resolve the conflicts via computational approach. We implemented such a display system and used it to evaluate the feasibility of the approach.

Is there a preview benefit when reading scrolled text

Abstract: When we read, our eyes move systematically across the page. On average, we fixate on an area of text for about 250 msec, then move our eyes about seven letters to the right (Rayner, 1978).