Because we view the three-dimensional world from two horizontally separated eyes, each eye has a slightly different view of the environment. Wheatstone’s invention of the stereoscope showed that small differences between the images in the two eyes produced by viewing a three-dimensional scene from different vantage points allow recovery of the depth relationships that produced the differences. For many years the emphasis has been on what seemed like the simplest and most potent aspect of this information namely the horizontal differences in image width (horizontal disparity) produced by points at different depths. Since the invention of the random dot stereogram (Julesz) an accompanying preoccupation has been to model the processes by which the visual system decides which elements in the two eyes “correspond” in the sense of originating from the same configurations in the environment. Disparity can only be evaluated for corresponding images. Much more recently another aspect of stereoscopic vision has begun to receive attention. Another consequence of viewing a three dimensional scene from two laterally separated eyes is that surfaces and objects at different distances occlude one another to different extents in the two eyes, resulting in image points that are visible to one eye but not the other. These monocular features have no corresponding match in the other eye and therefore no binocular disparity can be calculated for these points. One might be tempted to view monocular features as uninformative noise that is tolerated by the stereoscopic system and perhaps allocated to a depth plane after depth is resolved binocularly. Some computational models of stereopsis, which will be discussed in Section 5, have attempted to incorporate monocular features in their recovery of depth. In the past 18 years, a number of findings have clearly indicated that monocular details contribute to binocular depth perception (for example: Gillam, Blackburn & Nakayama; Gillam & Borsting; Gillam & Nakayama; Grove, Gillam & Ono; Liu, Stevenson & Schor; Nakayama & Shimojo; Ono, Shimono & Shibuta; see also Howard and Rogers, 2002 for a full review). In all of these studies the monocular elements are clearly distinct from the binocular regions. However there are binocular stimulus conditions that are ambiguous with respect to whether monocular regions exist or not. For example a
[1]
Ken Nakayama,et al.
Quantitative depth for a phantom surface can be based on cyclopean occlusion cues alone
,
1999,
Vision Research.
[2]
B. Gillam,et al.
The induced effect, vertical disparity, and stereoscopic theory
,
1983,
Perception & psychophysics.
[3]
Geoffrey Egnal,et al.
Detecting Binocular Half-Occlusions: Empirical Comparisons of Five Approaches
,
2002,
IEEE Trans. Pattern Anal. Mach. Intell..
[4]
B. Julesz.
Binocular depth perception of computer-generated patterns
,
1960
.
[5]
B Gillam,et al.
The Role of Monocular Regions in Stereoscopic Displays
,
1988,
Perception.
[6]
H. Ono,et al.
Occlusion as a depth cue in the Wheatstone-Panum limiting case
,
1992,
Perception & psychophysics.
[7]
Barton L. Anderson,et al.
The role of partial occlusion in stereopsis
,
1994,
Nature.
[8]
J. E. W. Mayhew,et al.
A computational model of binocular depth perception
,
1982,
Nature.
[9]
Shinsuke Shimojo,et al.
Da vinci stereopsis: Depth and subjective occluding contours from unpaired image points
,
1990,
Vision Research.
[10]
B. Gillam,et al.
How Configurations of Binocular Disparity Determine Whether Stereoscopic Slant or Stereoscopic Occlusion is Seen
,
2005,
Perception.
[11]
G. Nyman,et al.
Occlusion Constraints and Stereoscopic Slant
,
1997,
Perception.
[13]
Philip M. Grove,et al.
Slant or occlusion: global factors resolve stereoscopic ambiguity in sets of horizontal lines
,
2004,
Vision Research.
[14]
K. N. Ogle.
Researches in binocular vision.
,
1950
.
[15]
I. Howard,et al.
Seeing in depth, Vol. 2: Depth perception.
,
2002
.
[16]
Hiroshi Ono,et al.
Content and context of monocular regions determine perceived depth in random dot, unpaired background and phantom stereograms
,
2002,
Vision Research.
[17]
Lei Liu,et al.
Quantitative stereoscopic depth without binocular correspondence
,
1994,
Nature.