From Big Medical Encyclopedia

STEREOSCOPIC DEVICES (Greek stereos firm, volume + skopeo to look, investigate) — binocular optical devices for receiving and a research of the volume image. Stereoscopes, stereoscopic cameras, stereopipes, etc. concern to them.

Stereoscopes are intended for examining of two flat objects (stereo pairs). The principle of action of a stereoscope consists in examining of two images of the same subject received from two various points of shooting. One image is considered by the right eye, and another — left, at the same time their images merge in one, and the represented object looks volume. Objects for the right and left eye shall have the distinctions (disparity) providing the binocular parallax corresponding to the located objects real spatially at solid vision (see). Using stereo pairs with various degree of disparity, it is possible to define the sharpness of solid deep vision equal to the minimum size of disparity, at a cut there is a feeling of dimensions (see. Squint ).

Fig. 1. Elementary optical diagrams of mirror, lens and mirror and lens stereoscopes: 1 — an object for the right eye; 2 — eyes of the observer; 3 — an object for the left eye; 4 — mirror reflectors; 5 — the observed combined stereoscopic image; 6 — lenses.
Fig. 2. A folding stereoscope with a mirror of SZ-1: 1 — an object for the left eye; 2 — a mirror on a mechanical divider of fields of vision; 3 — scales for definition of disturbances of solid vision; 4 — a rack with an object for the right eye (a white spot on top end of a rack).

There are mirror, lens and mirror and lens stereoscopes. The mirror stereoscope (fig. 1, a) was offered in 1831 to Uitstonom (S. by Wheatstone). The observer considers reflected from mirrors or prisms (for each eye) images of an object, to-rye thanks to convergence merge in one. In lens stereoscopes (fig. 1, b) the observer considers images of an object through the lenses or wedges creating their combined image. Lenses, napr, in a stereoscope of Karl Tseyss (GDR), allow to receive the enlarged image of the considered object. Use mirror and lens stereoscopes more often (fig. 1, c), to-rye provide the best division of fields of vision of the right and left eye and necessary blowup.

In the USSR the folding stereoscope with a mirror of SZ-1 (fig. 2) intended for identification and treatment of disturbances of solid vision is issued. It allows to develop fusional reserves, to reveal and train the wrong correspondence of retinas, to define existence and size of functional scotoma.

Stereoscopic cameras have two lenses or special mirror or prismatic nozzles allowing to receive simultaneous pictures of the photographed object from two points to provide the necessary binocular parallax corresponding to solid vision of the person. Stereoscopic cameras are used also in medicine, in particular to photography of microscopic objects, an eyeground, etc. In the USSR the stereoscopic camera is developed for shooting of the person and the head. Measurement of the received stereo pairs on a special stereoscope allows to determine the sizes of separate elements of the person and head of the person that is necessary at prosthetics, and also at establishment of average values of these parameters during the designing of-point frames, safety spectacles, etc.

Stereotruby are intended for observation of relief of the image of the area, dimensions of observed space objects. It is reached by means of the mirror or prismatic devices increasing distance between visual axes of eyes and respectively disparity between the pictures observed by the right and left eye.

Bibliography: Valyus N. A. Stereoscopy, M., 1962; Zaksenveger R. Anomalies of stereoscopic sight at squint and their treatment, the lane with it., M., 1963; Kravkov S. V. An eye and its work, M. — L., 1950.

A. D. Noskova.