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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 57, Iss. 6 — Jun. 1, 1967
  • pp: 819–826

Extension of Panum’s Fusional Area in Binocularly Stabilized Vision

DEREK FENDER and BELA JULESZ  »View Author Affiliations

JOSA, Vol. 57, Issue 6, pp. 819-826 (1967)

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A novel phenomenon in stereopsis can be observed when viewing binocularly stabilized retinal images. This phenomenon is particularly impressive for random-dot stereoscopic images in foveal vision. If initially the left and right images are brought within Panum's fusional area (6-min arc alignment), fusion and stereopsis are perceived; the images can then be pulled apart symmetrically by about 2 deg in the horizontal direction without loss of stereopsis or fusion. The images are actually pulled apart on the retinae, since the binocular retinal stabilization compensates for the convergence-divergence motions of the eyes; hence a supra-retinal function must be responsible for this type of fusion. If the pulling proceeds too fast, or exceeds the 2-deg limit, or if the stimulus is occluded briefly, the fusional mechanism fails and the fused image abruptly breaks apart into two separate images which have to be brought within Panum's area again to re-establish fusion. For line stimuli, the maximum disparity without loss of fusion is much less than for random-dot patterns; it is always largest for disparity in the horizontal direction and is less in the vertical direction. These findings indicate that stereopsis and the classically conceived corresponding points greatly depend both on the class of stimulus used and on the recent history of the stimulation.

DEREK FENDER and BELA JULESZ, "Extension of Panum’s Fusional Area in Binocularly Stabilized Vision," J. Opt. Soc. Am. 57, 819-826 (1967)

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  1. H. W. Dove, Ber. Preuss. Akad. Wiss. 1841, 251 (1841) and Ann. Physik, Ser. 2, 110, 494 (1860).
  2. K. N. Ogle, Researches in Binocular Vision (Saunders, Philadelphia, 1950).
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  4. B. Julesz, Bell System Tech. J. 39, 1125 (1960). For an upto-date review see: Science 145, 356 (1964).
  5. D. H. Fender and P. W. Nye, Kybernetik. 1, 81 (1961).
  6. S. L. Polyak, The Retina (The University of Chicago Press, Chicago, 1941), Ch. 15, p. 204.
  7. G. H. Byford, Nature 184, 1493 (1959).
  8. G. D. McCann and D. H. Fender, Neural Theory and Modeling (Stanford University Press, Stanford, California, 1964), p. 232.
  9. Subject G was unable to obtain more than fleeting glimpses of the stereoscopic effect in stabilized vision despite considerable training. Most subjects can examine a considerable area of a stabilized image with high acuity even though they cannot shift their line of regard over the target. This area is usually elliptical, subtending about 2 deg horizontally by 1 deg vertically; outside of this area, acuity in stabilized vision falls off rapidly. Subject G does not have this faculty; his area of high acuity in stabilized vision is at most 20-min arc wide; thus very rarely is he able to resolve a sufficient number of picture elements belonging to the central square and some belonging to the surround at the same time a condition which appears to be necessary for perception of the stereoscopic effect. Subject G showed normal stereopsis with line targets in normal and in stabilized vision, and also with random-dot targets in normal vision.
  10. B. Julesz, J. Opt. Soc. Am. 53, 994 (1963).
  11. The actual binocular parallax in these targets was 8-min arc, so some of these saccadic changes of disparity may have been purposeful. The probability of a saccade changing the disparity by less than 5-min arc or more than 11-min arc is 0.65.
  12. G. W. Beeler, Ph.D. thesis (California Institute of Technology, 1965).

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