Patent GB-637080-A (GB)
Title: Improvements in or relating to reflex view finders and focussing devices and to photographic cameras incorporating such devices
IPC: G03B19/12
Filed: 1945-10-11
Abstract: 637,080. Photographic reflex view-finders; cameras and stereoscopic cameras. WOUTERS D'OPLINTER, J. G. DE. Oct. 11, 1945, Nos. 26538 and 26539. Convention dates, Feb. 11. 1941, and May 29, 1941. [Classes 98 (i) and 98 (ii)] To avoid lateral inversion of the image a reflex view-finder comprises an object lens, a plane mirror projecting an image on to a ground glass screen parallel or inclined at an angle to the optical axis of the lens, a dihedral mirror or a prism whose faces make between them an angle of 90 degrees disposed beyond the ground glass screen to redress the image, an auxiliary mirror on to which the redressed image is projected, and an eye-piece for observing the redressed image. As shown in Fig. 1, a single lens reflex camera has object lens 1, movable plane mirror 2 behind which is the film 3, ground glass screen 4 and above this a roofprism 5 with its apex edge 6 parallel to the optical axis, auxiliary mirror 7 and eye-piece lens 8. Two such eye-piece lenses may be provided to permit binocular observation of the image, and they may, conveniently, be located above the film spools, leaving, between them a depression in the outer casing of the camera to provide clearance for the nose of the observer. In Fig. 3, a miniature reflex camera, the ground glass screen 4, auxiliary mirror 7 and ocular lens 8 are constituted by the several surfaces of a single prism, the upper faces of which, meeting at apex edge 6, form the dihedral mirror. The stereoscopic camera, Fig. 6, is essentially'two single-lens cameras as of Fig. 1 arranged side by side in one unit, but each with its own eye-piece directed to the separate left and right eye images formed in the two camera portions, both of these images being upright and laterally redressed. Focusing.-Two small and similar marks 12. engraved one on each ground glass 4 of the stereoscopic camera; the marks being, preferably, short lines parallel to the planes of symmetry, are taken in by the eyes as part of the images and merged by binocular vision; and by provision of mechanism (Figs. 4 and 5, not shown) to vary the distance apart from each other of the two object lenses in combination with the normal fore-and-aft focusing movements of these lenses, focusing may be effected on the principle of a stereoscopic range-finder. The Specification as open to inspection under Sect. 91 comprises also, as shown in Fig. 7 (Cancelled), a system of control of the movement of the film which is intended for use with unperforated film. In this the film 18 takes along with it, by adherence, an endless band 16 of elastic material which turns freely on revolving rollers 17. The band carries appropriate markings which show through an aperture 19 as the film is displaced by appropriate lengths, when it is rolled up on the spool 9. The elastic band also protects the rear face of the film from friction, causes it to rest elastically against the focal wall of the camera and prevents light from entering through the aperture 19. This subject-matter does not appear in the Specification as accepted.