Subjective evaluation by human observers is usually used to analyze and select an edge detector parametric setup when real-world images are considered. In this paper, we propose a statistical objective performance analysis and detector parameter selection, using detection results produced by different detector parameters. Using the correspondence between the different detection results, an estimated best edge map, utilized as an estimated ground truth (EGT), is obtained. This is done using both a receiver operating characteristics (ROC) analysis and a Chi-square test, and considers the trade off between information and noisiness in the detection results. The best edge detector parameter set (PS) is then selected by the same statistical approach, using the EGT. Results are demonstrated for several edge detection techniques, and compared to published subjective evaluation results. The method developed here suggests a general tool to assist in practical implementations of parametric edge detectors where an automatic process is required.

INTRODUCTION A growing number of people suffer from visual impairments. These impairments and the resulting disabilities greatly affect the quality of life of many older, otherwise healthy people. The rehabilitation needs of people with visual impairments cover a wide scope of activities including reading, face recognition, independent mobility, attending to daily activities, and watching television (TV). Traditionally, vision rehabilitation has been aimed at improving mobility and reading skills. The incorporation of computerized image enhancement to improve video images for people with visual impairments was first proposed by Peli and Peli. Although image enhancement may be used in portable mobility devices, 2,3 in the near future we see the main value of image enhancement in providing people with visual impairments with access to the growing volume of video images presented on stationary monitors. TV is an important means of obtaining information and sharing in our culture. S

With the aging of the population, the prevalence of eye diseases and thus of vision impairment is increasing. The TV watching habits of people with vision impairments are comparable to normally sighted people, 1 however their vision loss prevents them from fully benefiting from this medium. For over 20 years we have been developing video image-enhancement techniques designed to assist people with visual impairments, particularly those due to central retinal vision loss. A major difficulty in this endeavor is the lack of evaluation techniques to assess and compare the effectiveness of various enhancement methods. This paper reviews our approaches to image enhancement and the results we have obtained, with special emphasis on the difficulties encountered in the evaluation of the benefits of enhancement and the solutions we have developed to date.

attended scene

Abstract not found

We have proposed a novel concept of vision multiplexing for the visually impaired – superimposing contour images over their natural view of a scene or over original images presented on a TV screen. We have implemented the concept using an optical see-through head mounted display to provide either visual field expansion to patients with peripheral field loss or vision enhancement to patients with central vision loss. We have also implemented the concept in a video player with dynamic magnification for patients with central vision loss. Results of initial testing in the lab and on the street are promising.

Vision-model-based image foveation and motion estimation

This paper aims at describing a new framework which allows for the quantitative combination of different edge detectors based on the correspondence between the outcomes of a pre-selected set of operators. This is inspired from the problem that despite the enormous amount of literature on edge detection techniques, there is no single one that performs well in every possible image context. The so-called Kappa Statistics are employed in a novel fashion to enable a sound performance evaluation of the edge maps emerged from different parameter specifications. The proposed method is unique in the sense that the balance between the false detections (False Positives and False Negatives) is explicitly assessed in advanced and incorporated in the estimation of the optimum threshold. Results of this technique are demonstrated and compared to individual edge detection methods. 1.

Abstract not found

Purpose. Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonious anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion, we documented torsional strabismus and torsional HARC. Methods. Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter. The dichoptic visual field was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50 ° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared with that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results. Torsional anomalous retinal correspondence documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50 ° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit.