GB562233A - Optical sighting or viewing devices - Google Patents

Abstract

562,233. Sighting devices. CURTIES, C. L., and OFFER, T. J., (trading as BAKER, C., and CURTIES, M. G. L.). Dec. 15, 1941,' No. 16188.' [Class 97 (i)] In sighting apparatus comprising a concaveconvex transmissive reflector in the sighting tube to produce an image at infinity of an illuminated graticule, the radii of the two surfaces of the reflector are so selected that the images they respectively produce are coincident; the graticule, may be an opaque background having a transparent pattern thereon, may be artificially or naturally lighted, or self luminous and its luminosity may be variable. As shown, a graticule 1 backed by a diffusing screen 2 is lighted by a lamp 3 and condenser 4 in a casing 5, and a transmissive concave-convex glass element 6 having its concave surface facing the graticule forms images of the graticule at infinity by reflections in each of its surfaces. The radii of the surfaces are such that the image reflected by the convex surface is coincident with that reflected by the concave surface, the element being lenticular but having a focal length so large as to be without adverse effect on the use of the instrument. A removable neutraltinted glass 7 may be provided. The graticule may be parallel with the sighting axis, a reflector being provided between it and the element 6. A system of lenses or mirrors may be used in conjunction with natural lighting to provide adequate illumination. Specifications 562,240 and 562,241 are referred to.