GB867465A - Improvements in or relating to collimating view finders for photographic cameras - Google Patents

Abstract

867,465. Photographic viewfinders. LEITZ G.m.b.H., ERNST. June 10, 1959 [Aug. 29, 1958], No. 19858/59. Classes 97(1) and 98(1) A collimating viewfinder for a photographic camera, comprises means for imaging in the field of view of the finder an indication delimiting the image field of the finder, the indication being imaged by reflexion into the field of view from a marking carried by a marking plate, a transparent plate being arranged between the marking plate and the optical system of the viewer and having a deviating wedge-shaped portion arranged in a position adjacent to and parallel with the marking carried by the marking plate, the transparent plate being adjustable in its axial spacing from the marking plate in dependence on the focusing distance set on the objective of the camera, so as to vary the size of the delimiting indication in accordance with the focusing distance. As shown, the viewfinder and coupled short-home base rangefinder comprises viewfinder lenses 4 and 5, prisms 7-9, lens .10 pivoted in accordance with the focusing of objective 1 by lever arms 3a, 36, lenses 4a, 46, and mixing prisms 6a, 6b. The markings carried by marking plate 11, are in the form of translucent line slits and are illuminated through a window (not shown) in the camera front. Several sets of markings may be provided for indicating fields corresponding to objectives having different focal lengths. For correcting the viewfinder parallax, plate 11 is mounted in a carrier 14, and is adjusted in its own plane in accordance with the focusing of objective 1 by lever arm 3c. Also mounted in carrier 14 for adjustment with plate 11 is a transparent plate 12 having wedge shaped portions arranged in positions corresponding to the markings of plate 11. To correct for changes in image field associated with changes in distance of focus, plate 12 is connected by link 15 to lever arm 3b for adjustment of its distance of separation from plate 11 in accordance with the focusing of objective 1. An adjustable covering member described in Specification 746,674 may be provided in front of plate 11 to cover those markings not in use for a particular objective lens, and either a collecting lens 16 or equivalent wedge shaped elements, corresponding in their positions to the marking slits, may be provided either fixed to the covering member or to the plate 11. In modifications, markings on plate 11 may be illuminated by diffusely reflected light instead of transmitted light, plate 12 may be coloured, prism 9 may be adjusted instead of lens 10, the rangefinder may be dispensed with and other adjusting means provided for plates 11 and 12, and instead of displacing plate 11, an optical wedge may be adjusted in dependence on the setting of the camera objective.