GB423742A - Improvements in or relating to light projectors - Google Patents

Abstract

423,742. Vehicle-lamps, searchlights, &c. COOKE, A. G., 101, Brondesbury Road, Kilburn, London. Aug. 2, 1933, No. 21746. [Classes 39 (ii), 75 (ii), and 75 (iv)] A motor vehicle headlamp, searchlight, or other light projector comprises a light source, an ellipsoidal reflector 2, a concave lens 5 of short focus, and a convex lens 8 or lens system or equivalent mirror or mirror system of longer focus than the concave lens, so disposed that the angle of divergence or convergence of the rays is successively reduced. The centre of the filament is at one focus of the ellipsoidal reflector and at the centre of a spherical part 7 formed in one with the ellipsoidal part of the reflector, and the second focus of the ellipsoidal part is at 4. The containing bulb of the lamp may be suitably shaped and silvered to act as the reflector. The concave lens 5 has its boundary surface shaped as a cone of about 30‹ extended by a silver cone 51, for internal reflection of widely divergent rays. In another form, an electric arc is the light source, and an additional short convex lens is provided within the ellipsoidal reflector to bring light rays to the same focus as the reflector. A concave reflector which replaces the convex lens 8 can be turned through a considerable angle to vary the direction of the beam. A narrow horizontal strip of blue glass may be placed in front of the concave lens at the point where the light is concentrated. According to the Provisional Specification, instead of the spherical part 7 a hyperboloidal reflector confocal with the ellipsoidal reflector 2 is provided. A small convex reflector facing the aperture reflects the rays reflected by the hyperboloidal reflector.