GB585819A - Improvements in or relating to range finders - Google Patents

Abstract

585,819. Range-finders. INTERNATIONAL POLAROID CORPORATION. April 6, 1944, No. 6515. Convention date, March 2, 1943. [Class 97 (i)] In a stereoscopic range-finder the image of a graticule formed by a collimating lens 24 positioned between the graticule and the eyes of the observer, is superimposed upon the field of view of the observer. Transparent mirrors 15, permitting the graticule image to be seen therethrough, are provided for reflecting the incident rays from other mirrors 12 which increase the effective interocular distance of the observer. The position of the graticule with respect to the focal plane of the lens being known, the apparent position of the graticule in the field of view is therefore known and hence the range of an object in the field of view, stereoscopically fusing with the graticule image, is also known. As shown, the mirrors 15 are at right angles to one another and the mirrors 12 are also at right angles, but these angles may be varied to provide different scales. In the form shown in Fig. 2, the graticule comprises simply a light source 22 preferably positioned within the focal plane of the lens 24. A plurality of ranges may be given by using the graticule shown in Fig. 3 which comprises a number of superimposed sheets each carrying a differently positioned mark A, B, C or D so that when the graticule is set up, each mark lies at a different distance from the focal plane of the lens; e.g. the mark A may lie in the focal plane and each successive mark predetermined distances within the focal plane so that if, for example, the focal length of the lens is 18" and the sheets are .0075" thick and the instrument has a base line of four feet, mark D appears to lie 600 yards and mark C 1200 yards from the instrument. The graticule may also be used with a range-finder not provided with means for increasing the interocular distance.