[Method for measuring sensitivity to periodic spectral energy modulations in human]

The distribution of spectral energy of a visual stimulus can be subject to Fourier analysis. In this perspective, we have built a device which produces periodic variations in energy (square waves) over the visible spectrum (400-700 nm), and where the amplitude, phase and frequency of the stimuli can be independently controlled. From the non-modulated spectrum, supplying a white spot, for a given frequency and phase, there is a minimal amplitude modulation (contrast threshold) for which the spot becomes chromatic. As an illustrative example we present here a curve of optimal sensitivity values (inverse of contrast) as a function of frequency (from 0.5 to 3.6 cycles/300 nm) for a normal subject.