STEREOSCOPE

(Fr.), n. Sta-ra-o-skop. See STEREOSCOPE. - S. a charniere. Ger.,Spfegel-Stereos kop. A stereoscope devised by Javal for the subjective determination of the squinting angle. Around a vertical hinge two mirrors may be rotated. Each of these mirrors is firmly fastened at its other end at an angle of 45 with a plate or tablet. Upon the inner surface of the latter are placed the objects of fixation, which are to be reflected by the mirrors. If an observer looks with one eye toward one mirror and the other toward the other, then by a proper arrangement of the angle of the hinge he can fuse the two reflected images. If this angle is 90 the eyes must stand parallel, if it is greater than 90 they must diverge, if it is smaller they must converge, in order to see binocularly. The position of the mirrors in which each eye is directed toward one of the images is thus found, and the included angle may be read off on a graduated arc. ["Ann. d'ocul.," liv, p. 14, Ixv, p. 124 (F).] [s. 537]