MATCHED-FILTERS IN HUMAN-VISION

The technique of subthreshold addition of sinusoidal gratings was used to analyze the visual system of man during the perception of edges, lines and bars. The experimentally obtained sensitivity function varied in close relationship to the test pattern, and could be factorized into the conjugate complex spectrum of the test pattern at threshold and a pattern-invariant function of spatial frequency. Interpreting the sensitivity function as transfer function, which was possible under certain conditions, the visual system was described as a matched filter which extracts an input signal contaminated with noise of specified spectral energy density. The spatial operations occurring in matched filters, the relationship between the modulation transfer function for sine-wave gratings and the pattern-invariant transfer component, the exact determination of elements within the theoretical concept and the realization of matched filters by the nervous system were discussed.