Zograscope

A zograscope is an optical viewing device designed to enhance the illusion of depth in a single flat image. It typically consists of a large positive lens combined with a mirror, mounted on a stand. The zograscope was most popular during the eighteenth century and was primarily used to view perspective prints, engravings, maps, and landscapes.

The zograscope and the stereoscope both aim to increase the perception of depth, but they employ fundamentally different methods. A zograscope presents a single image to both eyes and relies on existing pictorial depth cues within that image. The depth effect is therefore an enhancement of a two-dimensional picture rather than a reconstruction of binocular vision. A stereoscope, by contrast, presents two slightly different images, one to each eye. The brain combines these images into a single scene and interprets the differences between them as depth. This process produces a stronger and more realistic three-dimensional effect.