GB460039A - Improvements relating to optical appliances - Google Patents

Abstract

460,039. Viewing - appliances. WINGATE, G. H., and HAMBLIN, Ltd., T. July 23, 1935, No. 20960. [Class 97 (i)] An appliance enabling objects to be viewed when at a considerable angle to the direct line of vision comprises a prism mounted in a wearing frame and having a mirrored face which reflects back light on to the entrance face by which it is totally reflected to enter the eye through a third face. The appliance is particularly intended to enable a supine person, such as a spinal patient, to observe objects placed immediately above his chest while he looks substantially vertically upwards. The device shown comprises a frame 1, similar to a spectacle frame, carrying a pair of triangular prisms. The angles A, B, C of each prism are preferably 75‹, 70‹, and 35‹ respectively and the prism is mounted so that rays from the object to be viewed are incident on the longest face BC. The face AB is silvered so as to reflect the rays back to the face BC by which they are totally reflected to pass out through the face AC. Each prism is provided with a shield having a part 3 covering the face AB, parts 6 covering the end faces and a part 4 extending downwardly in front. The shield has lugs 11 by which the prisms can be adjusted laterally in their frames 2. The side arms of the frame are connected to the front by hinges 12 enabling the inclination of the prisms to be adjusted, and the bridge is preferably adjustable as to height. Visual correction may be effected by providing the frame with separate lenses or by grinding lens surfaces on the prisms. The frame may be provided with hoods to exclude strong light from the eyes.