GB664831A - Improvements in and relating to optical projection apparatus - Google Patents

Abstract

664,831. Optical - projection apparatus. GRANT PRODUCTION CO., Ltd., and BYNG, R. C. Aug. 22, 1949 [Aug. 27, 1948], No. 22647/48. Class 97 (i). An episcope comprises a casing, a screen fixed thereto, a lens carrier and an object carrier, the two carriers being independently movable relatively to the screen so that an image of the object, of selected size, may be focused on the screen. In the form shown, the casing 1 has a lid 2 carrying the projection screen 3. The carrier 11 has a projection lens mounted at its centre and is connected to the screen by a flexible bellows. A lighting unit, consisting of lamps in a reflector 13, is detachably secured to this carrier, a sleeve 14 being interposed between the lamps and the lens. The carrier 11 and the object carrier 9 are vertically slidable on guides 7 and are separately adjustable by hand wheels 19. Each hand wheel operates a pulley 22 round which passes a wire cable 23, attached to one of the carriers, and passing also round pulleys 17, 18, its two ends being attached to a counterweight 24. Other cables attached to the carriers may be provided at the other side of the casing and coupled to the first pair by shafts 25. An auxiliary platform may be provided on which an object may be placed and illuminated by the unit 13 detached for the purpose. To produce on the screen an image of the elevation of such an object the platform is placed opposite an opening in the casing wall and light from the object entering therein is reflected by two mirrors successively into the lens. The two mirrors are mounted on a base to form an auxiliary unit to stand on the carrier 9. The auxiliary object platform may be mounted on wheels to be movable to focus the projected image. A foldable hood protects the screen 3 from stray light.