GB664250A - Optical device for obtaining even illumination in space - Google Patents

Abstract

664,250. Lighting apparatus. GRETENER, E. Aug. 30, 1948 [Sept. 3, 1947], No. 22775/48. Class 75(ii) A means for illuminating a space of predetermined dimensions by means of a single light source comprises a light reflecting or refracting surface in association with the light source, the said surface being so constructed that all rays reflected or refracted by said surface and disposed in a common vertical plane intersect at or near one common point in front of the space to be illuminated, whereas all reflected or refracted rays disposed in a common horizontal or approximately horizontal plane intersect at or near one common point at the rear of the said space. Fig. 3 shows one form of the optical system In sectional elevation and in plan view, respectively. A reflector 2, having a radius of curvature in the horizontal plane different from that in the vertical plane, receives light fom a source 1 and forms a virtual image 71 in a vertical plane and a real image 80 in a horizontal plane. The image 71 is disposed behind the space to be illuminated, which has the form of a rectangular prism having sides 3, 4 and 5, and the image 80 is disposed in front of said space. Alternatively, the images may be produced by. a prismatic refracting element 52, Fig. 4, having vertical prisms crossed by horizontal prisms. The vertical prisms refract light rays from a source 51 to produce a real image 80 behind the space to be illuminated and the horizontal prisms produce a virtual image 71 in front of said space. The light source may comprise one or more lamps radiating a fan-shaped beam, and the light-refracting surface may be formed on an element made of translucent or transparent material.