FACTORS IN PHSIOLOGICAL OPTICS ON VISUAL FATIGUE IN DISPLAY WORK

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In Experiment I, increment threshold was measured on flickering background stimulus of which waveform was one of step, sinusoidal, on-ramp, or off-ramp function. At low flicker frequencies, increments vary sinusoidally independent from the waveform of background stimulus suggesting that the first Fourier component is the most important factor. At high frequencies, increments fluctuate randomly. Above CFF, where subject does not see perceptual flicker, increment threshold differs from that on steady background of equal luminance. It suggests that some kind of transient responses occur in visual pathway, even though the stimulus looks steady.In Experiment ll, a target letter pattern was superimposed on a noise letter parrern of different chromaticity and luminance, and the percent correct in recognition of the target letter was measured for two stimulus sizes and two durations. One letter was white and the other was one of red, green, yellow, or blue. For all subjects, decrease of percent correct was found where the target is in equal luminance and/or equal brightness with the noise. At equal luminance condition, recognition of colored stimulus is easier than white one except yellow which is almost same as white. These color effects increase with stimulus size and duration. The results of Experiment ll showed that condition where target and noise (or background) are equal luminance and/or brightness is undesirable condition for recognizing a target letter in display work.