GB203668A - - Google Patents

Abstract

203,668. Zeiss, C. [Firm of]. Sept. 6, 1922, [Convention date]. Addition to 147,107. Finders.-Modified constructions are described of the finder described in the parent Specification. In one construction, Figs. 1 and 2, the sighting- mark frame c is shaped to correspond to the image field, and the central part b of the lens b is flattened or pierced to enable the object to be seen directly and at the same time as the frame c is seen through the rest of the lens. Alternatively the lens may be formed of flat discs d<1>, d<2>, d<3>, d<4>, Fig. 3, cemented together so as to form plane steps with spherical margins, the frame being viewed through the spherical parts and the object directly seen through the plane portions. In another construction, Figs. 5 and 6, a semi-transparent concave mirror f, is placed in front of the eye-piece g which has a sight hole g<1>, and a portion of the rear surface of the eyepiece corresponding to the image field is painted black and has a white margin. The mirror may be formed by lightly silvering, smoking, or colouring the glass, or by silvering in strips or gratings so that the transparent and reflecting portions alternate. In another construction, Fig. 7, the sighting marks formed by gaps in an opaque coating in the glass plate k are projected by the lens i and viewed by reflection from the grating-mirrored glass plate m through which the object is directly viewed.