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Central visual defect results in loss of vision in the region of retina with the highest resolution. Due to central visual field loss, these patients experience difficulty in visual tasks such as reading and recognizing faces. Age related macular degeneration (ARMD) and juvenile macular degeneration (JMD), destroy the function of the central retina. NASA Johnson Space Center has developed an electronic remapper that can warp from one coordinate system to another on a television screen. The remapper was used in this study to redistribute visual images projecting on the macular lesion to the still functioning peripheral retina. The purpose of this study was to investigate whether remapping of reading material around the central scotomas of patients with ARMD and JMD improved reading rates. Reading rates of nonremapped words and remapped words were compared under three viewing conditions: (1) Reading without stabilization under free viewing condition, (2) Reading with image stabilization through the eye tracker, (3) Reading without image stabilization through the eye tracker.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We discuss the use of an optical correlator with a highly coupled filter and dappled targets to track an object in a field of view cluttered by background noise and/or similar objects. The dappled targets are fractal images whose statistics are independent of scale. Each is unique for tracking the targets. We report the drop in correlation (hence recognition) of an object as a function of in-plane rotation and as a function of range. We discuss plans for an application in Johnson Space Center's Automation and Robotics group, in which correlation processing of these targets would distinguish an object and pass its position and orientation to a robot control system. Using MEDOF (minimum Euclidean distance optimal filter) to create filters on the coupled filter modulator, we show that background clutter can be optically filtered out.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Retinal pathology often results in visual field loss. Age related macular degeneration (ARMD) and Stargardt's disease (a congenital disease) typically affects the central macular region of the retina, resulting in visual field loss to the region of the retina with the highest resolution. Due to the central visual field losses, patients with ARMD and Stargardt's disease often experience difficulty in visual tasks, such as reading and facial recognition. NASA Johnson Space Center has developed an electronic remapper that can warp an image from one coordinate system to another on a television screen. The remapper can be used with patients with central visual field loss to redistribute information projecting off of the macular lesion (corresponding to the central scotoma) and onto the still functioning peripheral retina. The purpose of this research project was to investigate whether remapping of text around the central scotoma improved reading performance (increased reading rate) for patients with ARMD or Stargardt's disease. The subjects moved the text on the stage and read aloud random words of equal difficulty viewed on a closed circuit television screen. Reading speeds for normal and remapped text were obtained. Reading rates were determined for both free viewing and with stabilization of the position of the screen relative to the eye rotations. Results of these experiments are discussed.

We previously reported computer code designed to generate optical correlator filters by putting our optimization algorithm into practice. This code is MEDOF: Minimum Euclidean Distance Optimal Filter. MEDOF's version 1.0 demonstrated filters which maximize correlation peak intensity (INT). We also gave some discussion to the quadratic ratio metrics of signal to noise ratio (SNR) and peak to correlation energy ratio (PCE). These advanced metrics are now functional in the second version of MEDOF, which is publicly available through NASA's software distribution channel, COSMIC. This paper focuses on some of the practical issues faces when using MEDOF to generate filters. The underlying mathematical principles of MEDOF are discussed in passing while providing references to sources of more theoretical detail.

We use color for visual presentation of certain effects that are complex in nature but have previously been shown using only amplitude display. In particular we show (1) the field that results from complex encoding of an input object, and (2) the departure from ideal of the object that is actually correlated with the input object. The departures are caused by limitations of filter SLMs and by the algorithms that compute filters for them.

We show laboratory results showing coupled-filter improvements in certain correlator performance metrics: signal to noise ratio, peak correlation energy, and peak to total energy. We had previously shown improvements in correlation intensity. The filters were built using JSC computer code for minimum Euclidean distance optimal filters.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We desire to have a joint transform correlator track features in the image of a human retina. Previous binarized digital methods indicated unacceptable limitations in tracking through torsion motions of the eye. To create an extended range of response to eyeball rotation we tried several methods of processing the reference image. We compared laboratory measurements with digital simulations. Based on small statistics and our noiseless models, the results disagree; the digital method has less range, and the optical method has sufficient range (+/- 5 degree(s)) for our purpose.

Certain visual functions, such as reading, are dependent on the high resolution capability of the central visual field. When that area becomes dysfunctional the tasks become difficult or impossible. We have proposed an image warping prosthesis, in which the structure of the image that would otherwise be unseen owing to the scotoma is moved outward and onto portions of the retina that still function. Previously we used normally sighted volunteers with fixated foveation, synthetic scotomas, a limited form of image warping, and externally controlled reading saccades. Their reading rate showed improvement in a significant number of instances. In the next stage, we are prepared to use volunteers with actual, not synthesized, scotomas. The results will be used to design realistic prostheses. Different warpings may better help other visual tasks such as facial recognition. Some of the image warpings designed for reading are shown here and our rationale for considering them are given.

We report a computer code that affects several efficiencies in taking a recently developed filter optimization algorithm into practice. The algorithm (Richard D. Juday, `Optimal realizable filters and the minimum Euclidean distance principle,' Applied Optics, in press) analytically optimizes filters on arbitrary modulators (coupled, binary, full complex, fractional 2(pi) phase, etc.). Its quadratic ratio metrics include intensity, signal to noise, and peak to correlation energy. The user supplies necessary information to the program, and also certain common complex arithmetic functions. The code is to be available from COSMIC under the name `MEDOF -- Minimum Euclidean Distance Optical Filters,' NT control number MSC-22380.

NASA and the University of Houston College of Optometry are examining the efficacy of image warping as a possible prosthesis for at least two forms of low vision - maculopathy and retinitis pigmentosa. Before incurring the expense of reducing the concept to practice, one would wish to have confidence that a worthwhile improvement in visual function would result. NASA's Programmable Remapper (PR) can warp an input image onto arbitrary geometric coordinate systems at full video rate, and it has recently been upgraded to accept computer-generated video text. We have integrated the Remapper with an SRI eye tracker to simulate visual malfunction in normal observers. A reading performance test has been developed to determine if the proposed warpings yield an increase in visual function; i.e., reading speed. We will describe the preliminary experimental results of this reading test with a simulated central field defect with and without remapped images.