Stereoscope

an optical instrument used in the examination of double photographic pictures made for the purpose. It was invented by Wheatstone in 1838. The original instrument was based on two mirrors, which have been replaced, however, by two refracting lenses. With the aid of this instrument two photographic pictures, a left hand and a right hand view, are examined at the same time, one by each eye, so that they make an impression of one picture. In this way a picture may be made to stand out more clearly. Surfaces appear in relief instead of flat, and relative distances are shown up better than by the examination of a single photograph, however clear it may be.