Abstract

Several problems posed by spatial and temporally sampled moving images may be ameliorated when knowledge of visual motion direction is known. We extend prior analyses of sampled moving images through the following conjecture. For rigid motion in one direction, the image spatiotemporal Fourier transform is a surface which occupies only two diagonal quadrants of the spatiotemporal frequency plane. Although sampling introduces energy to all four quadrants, that which falls over the wrong diagonal quadrants is likely to be more detrimental to motion perception, since the energy tends to excite motion detectors signaling an incorrect direction. If the direction of motion is known at every point in an image, temporally undersampled images may be partially reconstructed by removing this incorrect energy. This conjecture serves to explain the demise of short-range motion perception at large displacements and interstimulus intervals. It also explains motion capture phenomena, cooperativity, and the coherence of sampled motion displays containing elements which are effectively undersampled.

© 1988 Optical Society of America