Stereoscope (redirected from stereoscopically)

stereoscope (stĕr`ēəskōp'), optical instrument that presents to a viewer two slightly differing pictures, one to each eye, to give the effect of depth. In normal vision the two eyes, being a certain distance apart, see slightly different aspects of a scene. The impression of depth is obtained when the brain combines the images. A single photograph shows no more than what one eye would see. In a stereoscope two photographs, taken from positions related approximately as the positions of a person's two eyes, are placed side by side. When a person observes these photographs, his brain combines the separate images from each eye into a single three-dimensional one. Scientists, among them the English physicist Sir Charles Wheatstone in 1838, constructed stereoscopes for use with drawings, but suitable views were not generally available until the development of photography. In 1849, Sir David Brewster, a Scottish physicist, improved the stereoscope and invented the double camera for taking stereoscopic views. Oliver Wendell Holmes invented the kind of stereoscope that, together with a collection of stereoscopic views, became a popular instrument of home entertainment in the United States until the advent of the home phonograph and the radio. The principle of the stereoscope is applied in binocular field glasses and binocular microscopes.

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stereoscope

A handheld viewer that provides the illusion of a 3D image by using two 2D images (stereo images). Dating back to the 1890s and only for still images, stereoscopes were the first attempts at going beyond 2D. For more details about 3D, see 3D visualization and 3D glasses.

3D Viewers

In the first half of the 20th century, the stereoscope (top) used two lenses at slight angles to view 3D still images. In the 1940s and 1950s, the popular View-Master used a rotating paper disc with film frames, like 35 mm slides, but smaller. All 3D movies use 3D glasses and the dual-lens stereoscopic principle (bottom). For details, see 3D glasses and 3D visualization.

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stereoscope [′ster·ē·ə‚skōp]

(optics)

An optical instrument in which each eye views one of two photographs taken with the camera or object of study displaced, or simultaneously with two cameras, or with a stereoscopic camera, so that a sensation of depth is produced.

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Stereoscope 

an optical device for the three-dimensional viewing of photographs of landscapes or individual objects. The photographs must be taken from two different points and must overlap in order to reproduce objects in a manner corresponding to that in which they are individually seen by the right and left eyes. All stereoscopes are constructed with regard to the deviation of the rays from common points observed in the photographs in such a way that such points are perceived coincidentally (Figure 1). In some cases, this is achieved by using correspondingly mounted lenses; in other cases, mirrors are used. Stereoscopes

Figure 1. Diagrams of stereoscopes: (A) lens stereoscope, (B) mirror stereoscope; (1) lenses, (2) and (2a) mirrors, (3a) and (3b) identical points on the right and left photographs of a stereopair, (4) point at which the points 3a and 3b are seen stereoscopically as coincident, (5) ocular axes of the observer

Table 1. Types of stereoscopes
Type	Magnification	Field of view (cm)
Portable models
portable and pocket field models . . . . . . . . . . . . . .	2.5–3	6 × 6
stereoscopic eyeglasses . . . . . . . . . . . . . .	1.5–2	11 × 15
Tabletop models
without additional accessories . . . . . . . . . . . . . .	1–1.5	12 × 16
with binocular head and other accessories	4.5–6	from 4.5 × 4.5 to 3 × 3
Stationary models
topographic plotters and similar types . . . . . . . . . . . . . .	2–15	from 10 × 10 to 1.3 × 1.3

are used mainly for aerial photo interpretation. There are more than 100 different designs of stereoscopes. The major types are given in Table 1.

Some tabletop and stationary models, called scanning stereoscopes, are designed to permit rapid sequential viewing of a series of stereoscopic photographs by means of mutual displacements of the bed of the device and of the optical system. Stereomicroscopes are used for especially detailed study of scientific and technical photographs. They provide variable magnification up to 70 × (for a field of view of 2.5–3 mm) and up to 200 × with additional attachments. Pantographic stereoscopes are used in cartography. They are combinations of stereoscopes with variable magnification and optical pantographs. In the USSR and other countries, several models of portable and tabletop stereoscopes are produced as part of a system with measuring accessories (parallax instruments) and drafting attachments.

REFERENCES

Gol’dman, L. M., and R. I. Vol’pe. Deshifrirovanie aerosnimkov: Topograficheskoe i otraslevoe. (Itogi nauki: Geodeziia.) Moscow, 1968.
Gol’dman, L. M. Deshifrirovanie aerosnimkov za rubezhom. Moscow, 1970.
Narkevich, V. I. “’Obzorzarubezhnykh priborov dlia deshifrirovaniia aerofotosnimkov.” In the collection Primenenie aerofoios”emkipri izuchenii lesnogo i bolotnogo meliorativnogo fondov. Leningrad, 1973.

L. M. GOL’DMAN