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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Binocular vision | 4/6 | https://en.wikipedia.org/wiki/Binocular_vision | reference | science, encyclopedia | 2026-05-05T15:53:38.467964+00:00 | kb-cron |
==== Binoculars ==== With binoculars, the world that we know up close can also be viewed from a distance. The optics in the binoculars ensure that the retinal images are enlarged. The perceived depth is reduced, the image appears flatter. In order to restore the normal aspect ratio, binocular binoculars must be used to view from two points that are further apart than the two eyes. In binocular binoculars, the front lenses are therefore placed further apart using optical means (prisms or mirrors). The enlargement of the depth dimension that can be achieved in this way is practically limited to the area in which stereopsis is possible. At greater depth (disparity), the image appears flat. For a natural depth experience, it is important that the distance between the two lenses is adjusted to the magnification factor of the binoculars.
==== Microscope ====
A binocular microscope can be used to magnify and view a microscopic world. In order to see depth in this small world that is in proportion to the size of the objects present, the distance between the front lenses of the microscope must be much smaller than the normal distance between our eyes. This is done with the same optical means as with binocular binoculars, but then in a mirrored arrangement, see figure.
==== Without depth ==== Even without seeing depth, binocular vision has advantages over seeing with one eye. If care is taken to ensure that the images from both eyes overlap well and are sharp, then the images from both eyes reinforce each other (binocular summation) and it is as if the image is brighter. This can be compared to increasing the light intensity by using larger lenses.
=== Stereo images === Binocular images can be captured by recording both the image seen by the left eye and the image seen by the right eye in a stereogram. The images can be recorded simultaneously (stereo photography) or one after the other (scout stereogram, moon stereogram). The advantage of recording the images of the left and right eyes simultaneously with a stereo camera is that no false disparities arise because the scene to be recorded has changed between the recordings.
==== Stereogram ====
A stereogram is a set of two images (pictures, videos, or computer-generated images), one for each eye, that can be used to evoke a binocular three-dimensional scene. In a stereogram, the two images can be attached to each other, with the left-eye image on the left and the right-eye image on the right (L-R stereogram), or with the right-eye image on the left and the left-eye image on the right (R-L stereogram). A stereogram can also consist of two separate images that are placed separately in a stereoscope, or that are specially prepared and placed on top of each other, with color filters, polarizing filterss, or optical ridges used to ensure that each eye sees only one of the images. Stereograms have been and continue to be widely used in depth perception research, for entertainment, and for education. Stereograms can be made by hand, by drawing with a computer program, or by taking pictures with one or two still cameras (stereo camera) or video cameras. The geometry used to design the correct disparities for these images is described in epipolar geometry and computer stereo vision. For natural scenes, the recordings for a stereogram are usually made from observation positions that are as far apart as the distance between the two eyes. In macro photography, this distance must be smaller to obtain a natural depth effect, and in a scout stereogram it must be larger. Another special stereogram is based on the movement of the moon relative to the sun (moon stereogram). A large number of stereograms are special because they represent a certain cultural period, a certain application or technique, or an important step in the research into binocular vision. The following stereograms belong to the latter category. Examples of more can be found on the Internet.
==== Line stereogram ====
A line stereogram is a drawn stereogram. The first stereogram was a line stereogram used by Charles Wheatstone in 1838 to show that binocular depth is caused by binocular disparity. This type of stereogram has been widely used for research ever since, and is still used for this purpose.
==== Moon stereogram ====
Whipple conceived in 1860 of taking a photograph of the moon on two different days and viewing the photographs in a stereoscope. In the stereoscope, the wobbling of the moon (lunar libration) and the shifting of the shadows make the mountains and craters clearly visible in the depths. (Krol, 1982, p. 2-3). This stereogram illustrates that there are many ways in which disparities can arise, not only through the parallax of our two eyes.
==== Reconnaissance stereogram ==== Stereograms have been used since World War I during reconnaissance flights. During the flight, photographs of the terrain are taken at regular time intervals. Consecutive photos are viewed in pairs in a stereoscope. Camouflaged objects can now be clearly seen in depth. This stereogram illustrates that a stereogram can also be made with one camera, and that binocular depth perception helps to see through camouflage.
==== Random dot stereogram ====
In a random dot stereogram the left and right images consist of dots that are randomly white and black. Dots that lie within a certain (invisible) shape in the left image, for example, a triangle, also appear in the right image, but are shifted by 1 or more pixels. If the stereogram is viewed with both eyes, the shape becomes visible due to the difference in depth with the surrounding dots. This shows, among other things, that depth perception precedest to seeing shapes (Julesz, 1960).
==== Stereotesting ==== Medical professionals use several types of stereograms to test whether someone has depth perception or is stereoblind, and how accurate their depth perception is.