Stereoscopic Shadow-images

Abstract

THE following simple arrangement makes it possible to project, in stereoscopic depth, three-dimensional objects such as wire models of molecular or crystal structures. Small models may be presented enlarged in three dimensions, magnifications of ten or more times being possible. The optical arrangement consists of nothing but a pair of small bright light sources, separated horizontally by a few inches. The sources are placed behind ‘Polaroid filters’, set at orientations differing by 90°. The point polarized sources give a pair of shadow images of an object, such as a wire model, placed between them and a silver screen. Alternatively, back-projection with a ground-glass screen can be used; but the screen must not de-polarize the light. When the shadows are viewed through crossed ‘Polaroid’ glasses, they are fused by the brain to form a single stereoscopic shadow-image lying in space.