Achromatic stereoscope in mahogany cabinet, made by R & J Beck of London. This stereoscope is of the Brewster form, but contains several improvements. The lenses are achromatic (to remove colour fringes from the images) and their distance from the picture is adjustable by means of a rack and pinion. A mirror is provided for obtaining greater illumination of the picture, and a transluscent (rather than opaque) dividing screen is provided for the same purpose.
© Science Museum / Science & Society Picture Library