STEREOGRAM DESIGN FOR TESTING LOCAL STEREOPSIS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 19  (7) , 802-809
Abstract
The basic ability to utilize disparity as a depth cue, local stereopsis, does not sufficiently respond to random dot stereograms. They demand complex perceptual processing to resolve the depth ambiguities which help mask their pattern from monocular recognition. This requirement may cause response failure in otherwise good stereo subject and seems to account for the long durations of exposure required for target disparities which are still much larger than the best stereo thresholds. Spatial stimuli to test local stereopsis were evaluated. Targets need separation by at least a 10 min arc to obtain good stereo thresholds. For targets with optimal separation of components and brief exposure duration (250 ms), thresholds fall in the range of 5-15 s arc. Intertrial randomization of target lateral placement can effectively eliminate monocular cues and allow excellent stereoacuity. Stereoscopic acuity is less seriously affected by a small amount of optical defocus when target elements are widely separated than when they are crowded, although the performance decrement is higher than for ordinary [human] visual acuity.

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