Abstract

In certain circumstances, the visual system can detect the pattern space variance, which is smaller than a single cell’s dimension on the retina, and has a threshold much lower than the normal acuity, e.g., visual hyperacuity.¹ Recent physiological experiments² have shown that there are two kinds of receptive field in the cortex: symmetric and asymmetric. They can be expressed as a pair of Gabor functions having orthogonal character in both spatial and spatial frequency domains. Receiving the input signal of a spatial pattern, for example, a bar in a certain position, the two kinds of cell create two responses perpendicular to each other in the spatial frequency domain. Then the phase information of input can be considered a reconstruction of the spatial frequency responses. Calculations show a linear relationship between the input and output in the example of a bar which fits the experimental results of Westheimer.³ According to this explanation, the hypothesis of phase channels which are independent of spatial frequency channels is not necessary.

© 1987 Optical Society of America