Telestereoscope
The telestereoscope is a special binocular telescope with which the observer's eye relief is enlarged. It was invented by Hermann von Helmholtz and presented in a lecture to the Niederrheinische Gesellschaft für Natur- und Heilkunde in 1857 .
Stereopsis
If a person looks at an object in their vicinity, the images that are displayed on the retina are slightly different due to the different viewing angles of the respective eyes (the so-called transverse disparity ). These different retinal images can be used to estimate the distance (depth) from objects in the image ( stereopsis ). The closer the object, the more different the images in the eyes. When objects are removed, the images in both eyes are so similar that no depth differences can be perceived.
With an eye relief of about 65 mm on average, differences in depth due to the transverse disparity can only be perceived up to a distance of about m. The depth of more distant objects can only be determined through experience, e.g. B. can be estimated via relative size, obscurations, shadows or aerial perspective (so-called monocular spatial perception ). If objects are further away, for example a mountain range on the horizon, they appear flat.
The telestereoscope increases the interpupillary distance many times over. The accompanying drastic amplification of the stereoscopic effect makes it possible to clearly perceive differences in depth even with objects that are further away. With the telestereoscope built by Hermann Helmholtz, the viewer is given “an eye distance of four feet instead of the usual three inches” and “objects that are a quarter to a half mile away clearly detach themselves from their background”.
Structure of the telestereoscope
The instrument consists of four plane mirrors, which are fixed vertically in a wooden box and inclined at 45 ° to its longest edge. The light coming from the distant object falls on the two outer large mirrors, is reflected by these at right angles onto the two inner ones and, after it has also been reflected at right angles by the small inner mirrors, reaches the eyes of the observer. Each eye sees in the small mirrors the image of the landscape reflected by the large mirrors in such a perspective projection as appears from the two large mirrors. If you want to enlarge the picture, you can let the light rays go through small telescopes before they reach the eyes.
A telescope that can also be used as a telestereoscope is mainly used as a scissor telescope in the military.
Individual evidence
- ^ Hermann Helmholtz: The telestereoscope . In: Annals of Physics and Chemistry . tape 178 , 1857, pp. 167-175 ( Wikisource ).
- ↑ a b Vossische Zeitung . June 30, 1857, p. 17 ( zefys.staatsbibliothek-berlin.de [PDF; accessed on January 13, 2012]).