Disparity filtering: proximity detection and segmentation

Simple stereo disparity filters can provide `proximity detectors' shaped like concave shells in front of the observer. Ideally, these are isodisparity surfaces. In practice, a narrowly tuned filter results in a thin shell. The special case of the zero-disparity surface is called the horopter. A disparity filter can also be useful for distinguishing an object that lies on an isodisparity surface from its surroundings. These filters are much less expensive than stereographic scene interpretation since they are local operations. Similarly, they are also less general. We analyze the expected proximity sensitivity of one simple version of the disparity filter and compare this to its empirical performance. We also present some feature based and correlation based disparity filters and compare their `segmentation' performance on various scenes.