What determines the reference framework for stereopsis

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What determines the reference framework for
stereopsis?

• Andrew Glennerster, Martin Birch
• and Suzanne McKee
• University Laboratory of Physiology, Oxford
• Smith-Kettlewell Eye Research Institute, San
  Francisco

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Viewing geometry
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Depth in fronto-parallel coordinates
L
R
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Depth relative to a local surface
Mitchison and McKee (85, 87) Mitchison and
Westheimer (84)
L
R
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Depth perpendicular to a local surface
L
R
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Prediction
L
R
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Prediction
L
R
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Interleaved psychometric functions
L
R
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Stimulus details
Task

• is central column in front or behind the plane
  of the grid?

Stimulus

• dot size 2 arcmin
• pixel size 0.45 arcmin
• anti-aliased
• viewing distance 2.65 m
• exposure 600 ms
• grid disparity gradient /- 0.1
• slant about a vertical axis
• modified Wheatstone stereoscope

Target column
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Results grid disparity gradient -0.1
Subject MDB
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Grid disparity gradient 0.1
Subject MDB
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Grid disparity gradient -0.1
Subject AG
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Grid disparity gradient 0.1
Subject AG
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Summary of thresholds
MDB
Threshold (arcmin)
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Summary of thresholds
AG
Threshold (arcmin)
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Summary

• Thresholds for detecting relative disparity
  depend on the local surface slant
• Thresholds are lowest when the displacement is
  more orthogonal to the surface

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Conclusion

• The visual system may represent depth in a
  surface-based coordinate frame ...
• and hence be much less sensitive to rotations
  and translations of the head

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Conclusion

• The visual system may represent depth in a
  surface-based coordinate frame ...
• and hence be much less sensitive to rotations
  and translations of the head

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Comparison with lateral displacement thresholds
Key
Width of grid in the eye in which the target was
displaced (arcmin)
Subject MDB
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Sensitivity to lateral displacement
Subject MDB
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and to disparity lateral displacement
Subject MDB
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and to disparity lateral displacement
Subject MDB
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Grid gradient 0.1
Subject MDB
Subject SPM
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Grid gradient 0.1 and -0.1
Subject MDB
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Local surface model
0.1 gradient
-0.1 gradient
Subject MDB
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Interleaved slants
0.4 arcmin disparity
-0.4 arcmin disparity
Subject MDB
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Effect of perceived slant
Grid perceived as fronto-parallel
Grid perceived as slanted
Subject MDB