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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Binocular vision | 6/6 | https://en.wikipedia.org/wiki/Binocular_vision | reference | science, encyclopedia | 2026-05-05T15:53:38.467964+00:00 | kb-cron |
Hering's Cyclopean projection is intended as a description of what he observed and not as an explanation of how the egocentric image is formed in the brain. How the images from the two eyes are merged has been extensively investigated using a theoretical model, the geometric horopter. The geometric horopter is a circle through the fixation point and both eyes. Points on this circle have been shown to project (approximately) onto corresponding points in both eyes. These are points that look in the same visual direction in both eyes. In empirical research it has been established that it is possible to measure and compare the visual directions in both eyes and thus determine the observed horopter (empirical horopter). It turns out that this horopter is not a line but a vertical (frontoparallel) plane through the fixation point and that the shape of this plane differs per person. At short fixation distances the plane as seen from the observer is concave (hollow), at slightly greater distances flatter and at greater distances flat or convex. Furthermore, the plane curves towards the observer at the top and away from the observer at the bottom. It is generally assumed that these are adaptations to the environment, including how the eyes move in the recesses in the skull.
=== Sensory fusion ===
Observational research shows that points with unequal visual directions in both eyes are sometimes not seen double, but single, in a direction that lies between the two visual directions. This phenomenon is called sensory fusion. With a strong dominant eye, the perceived direction of the fused image is closer to the direction seen by the dominant eye.
=== Hering's experiment ===
Hering described an experiment to test Panum's theory. In the experiment, a thin rod is held straight ahead in the direction of view in the midsagittal plane. If the center of the rod is fixed, then the center of the rod should appear single and the ends double and receding in depth, as in the figure. Hering did not find this and thus rejected the theory. Hering's experiment is a special case of the midsagittal-strip illusion. This illusion explains that and why the fused image is seen transversely to the direction of view and not as Hering assumed.
=== Vergence horopter === As soon as a point that has the attention threatens to move outside Panum's fusion area, an automatic eye movement (vergence movement) ensures that the point comes to lie in the middle of Panum's fusion area again. In research on this reflex, the vergence horopter is defined as the set of points within Panum's fusion range that do not elicit a reflex. The measured horopter falls centrally within Panum's fusion range. In the vertical plane, the vergence horopter is less inclined than the corresponding fusion range.
=== Explanation === The existence of fusion is not explained by classical theory. Theories that make use of the fact that neurons have been found in the visual cortex that look in a specific visual direction via each eye seem to be able to explain this phenomenon better.
== See also == Stereopsis Binocular illusions Ophthalmology
== References ==
== Bibliography == Julesz, Bela (1971). Foundations of cyclopean perception. University of Chicago Press. ISBN 978-0-226-41527-7. Steinman, Scott B. & Steinman, Barbara A. & Garzia, Ralph Philip (2000). Foundations of Binocular Vision: A Clinical perspective. McGraw-Hill Medical. ISBN 0-8385-2670-5. Howard, I. P., & Rogers, B. J. (2012). Perceiving in depth. Volume 2, Stereoscopic vision. Oxford: Oxford University Press. ISBN 978-0-19-976415-0 Cabani, I. (2007). Segmentation et mise en correspondance couleur – Application: étude et conception d'un système de stéréovision couleur pour l'aide à la conduite automobile. ISBN 978-613-1-52103-4
== External links == Middlebury Stereo Vision Page VIP Laparoscopic / Endoscopic Video Dataset (stereo medical images) Archived 2011-05-12 at the Wayback Machine What is Stereo Vision? Learn about Stereograms then make your own Magic Eye International Orthoptic Association