Perceived luminance contrast of stereoscopic patterns

Le résumé fourni par la source

Previous studies have shown that luminance contrast under monocular viewing appears comparable to that under binocular viewing above threshold. However, little attention has been paid to perceived luminance contrast under stereoscopic viewing. Here we compared perceived luminance contrast of patterns with binocular disparity to that of zero-disparity patterns. Two vertical Gabor patterns were successively presented in each trial. The first pattern was the standard stimulus that had no binocular disparity. The second pattern was the comparison stimulus that had -1, -0.5, -0.25, 0, 0.25, 0.5, or 1° of binocular disparity. Five observers judged which pattern had the higher luminance contrast. Luminance contrast of the standard stimulus was set to -26 or -8 dB re 1 (5 % or 40 % of Michelson contrast). Luminance contrast of the comparison stimulus was varied according to a one-up one-down staircase method with a step size of 1.5 dB. Each staircase terminated after 6 reversals. The PSEs were determined by averaging the last 4 reversals of two interleaved staircases (8 reversals in total). The results showed that the mean PSEs for -8 dB standard contrast significantly decreased as the absolute value of binocular disparity increased. The mean PSEs were -9.4 and -11.0 dB at -1 and 1° of binocular disparity, respectively, whereas it was -8.5 dB at zero disparity. That is, luminance contrast of the patterns with binocular disparity was perceived approximately 1.10 and 1.34 times higher than that of a zero-disparity pattern. There was a similar significant trend for -26 dB standard contrast, although the effect was relatively small. The results will be discussed in terms of interocular suppression and stereoscopic vision.

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