Linear summation of spatial harmonics in human vision.

Abstract Previous investigators Tolhurst, 1972 , Nachmias et al., 1973 used suprathreshold of adaptation to re-examine the validity of Fourier theory in the detection of gratings. We have shown that the method of subthreshold summation eliminates possible factors obviously distorting linearity in their analysis of spatial harmonics when the adaptation technique is applied. Our results, by demonstrating the applicability of Fourier theory in the detection of gratings, confirm that this process may be regarded as linear at threshold.