GB396664A - Improvements in stereoscopic rangefinders for photographic purposes - Google Patents

Abstract

396,664. Rangefinders ; cameras. ZEISS, C., [Firm of], Carl Zeiss-Strasse, Jena, Germany. April 3, 1933, No. 9924. Convention date, April 6, 1932. [Classes 97 (i) and 98 (i).] In a stereoscopic rangefinder for photographic purposes, two mark images are presented, one to each eye of the observer, at a great apparent distance, and at least one of these images is displaceable parallel to the rangefinder base so as to alter the apparent distance of the stereoscopic mark due to the fusion of the two mark images. In the form shown, the rangefinder base is equal to the distance between the observer's eyes, and means are provided for compensating the range readings for variations in interpupillary distance. The marks 31, 311 are formed on plates 30, 30<1> and lie at the foci of lenses 29, 29<1> cemented to cubes 32, 321 each consisting of two right-angled prisms, the hypotenuse surfaces 34, 34<1> being semi-reflecting. The optical elements are enclosed in housings 35, 351 having objective apertures 37, 371 and ocular apertures 36, 36<1> so that an observer looking through the oculars sees the object to be ranged on and also sees images of the marks 31, 311 projected to a great apparent distance by the lenses 29, 29<1> and reflecting surfaces 34, 341. The housing 35 is pivoted at 39 to an arm 38 extending from the housing 351. Brackets 40, 42 extend from the arm 38 and housing 35<1>, and a spindle 43 terminating in a disc 44 passes through the bracket 40 and has threaded engagement in the bracket 42. A bracket 41 extending from the housing 35 provides a bearing for a spindle 49 carrying a disc 50 having an eccentric projection 53 bearing on the disc 44. Rotation of the spindle 43 causes the housing 35 to be turned about its pivot 39 to effect lateral displacement of the image of the mark 31, the extent of the angular movement depending on the distance of the projection 53 from the pivot. This distance is adjusted according to the observer's interpupillary distance by turning the graduated head 52. The range of the observed object is read off on the graduated head 47. A diaphragm may be provided which is imaged at a great apparent distance with one of the mark images, and is of such size that it restricts the field of view to an area corresponding to the image area in the focal plane of the camera.