Variable Prism Stereoscope

Description Of Item: Instrument 310 mm x 180 mm x 410 mm consists of a heavy base (diameter 145 mm) with a vertical rod which carries a headpiece containing rotatable 15 prism dioptre prisms and an adjustable head rest. A knurled knob allows adjustment of the prisms and the effective prism can be read using the pointer on a scale showing a total of up to 60? Base In or Base Out. Auxiliary lens holders either side of the prism carrier can hold extra prims or trial lenses. A shaft at right angles to the rod carries a moveable stereogram holder and a moveable septum bracket. The septum required to separate the two visual fields is missing. The stereogram holder is designed to use two single image plates and height adjustment is by the use of two separate screw mechanisms. About 30 mm of the screws has been broken off reducing the range of movement significantly. The shaft carrying the slide holder and septum can be removed allowing the headpiece to be used to exercise vergences with a distant fixation target such as a spot-light or a test type letter.