All ETDs from UAB

Advisory Committee Chair

Allan C Dobbins

Advisory Committee Members

Timothy J Gawne

Richard A Gray

Document Type


Date of Award


Degree Name by School

Master of Science in Biomedical Engineering (MSBME) School of Engineering


The binocular disparity of an object slanted in depth from the frontoparallel plane is not constant and changes with coordinate. Objects oriented in such way have non-zero disparity gradient. The processes that take place in the brain to recover disparity gradient and to create the correct perception of slant in depth are not well understood. Changes in local disparity are an obvious disparity gradient cue. Here, we consider an alternative means of disparity gradient detection exploiting the differential projection of oriented edges to each eye. Two retinal images of an object slanted in depth differ by the amount of horizontal shear and horizontal expansion/contraction. Retinal images of a non-horizontal line slanted in depth differ in orientation, and images of a horizontal line just differ in length. We offer computational models of disparity gradient detectors that utilize orientation and length difference information instead of binocular disparity information to recover disparity gradient. These models are evaluated as possible mechanisms of how neurons in the visual cortex accomplish perception of slant in depth. The tuned orientation difference cell models we consider are selective to difference of orientation of the stimulus in the two eyes (and therefore to the disparity gradient) independent of average orientation of the images within a narrow range. We propose a model of disparity gradient estimation based on iii differences in length that is insensitive to small changes in horizontal position and disparity of the stimulus. We also describe models of length difference sensitive cells that have responses invariant to changes in overall length of the stimulus. We believe that the models we describe are candidates for neurons that may exist in the visual cortex. These disparity gradient detectors can signal slant of objects in depth and can be a part of the mechanism of perception of threedimensional orientation of objects in space.

Included in

Engineering Commons



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.