GB453758A - Improvements in supplementary devices for binocular rangefinders - Google Patents

Abstract

453,758. Rangefinders. ZEISS, C., Carl-Zeiss-Strasse, Jena, Germany. June 2, 1936, No. 15313. Convention date, June 7, 1935. [Class 97 (i)] In a binocular rangefinder, in order to detect differences of height of the two images and thus to facilitate correction of these differences by means provided in the rangefinder, there is provided a supplementary device enabling both images to be viewed through a single eyepiece, the said device having at least one reflecting system for deflecting a pencil of imaging rays, an optical system combining the pencils of imaging rays of the two eyepieces, and an adjustable optical system for varying the height direction of one of the pencils. Figs. 1 and 2 show one form of the invention as applied to a stereoscopic rangefinder having pentagonal prisms 3 with roof-edged reflecting surfaces, objectives 4, reflecting-prisms 6 bearing measuring-marks 7, eyepieces 8, and a measuring device comprising a pair of prisms 10 which can be rotated in opposite directions by a head 9 bearing a scale 11. The instrument also contains means, consisting of prisms 14 rotatable in opposite directions by a head 13, for neutralizing differences of height of the two images relatively to their respective marks 7. The device according to the invention consists of a casing 15 which can be attached to the rangefinder and has windows 16 corresponding to the eyepieces 8, a reflecting prism 17 being mounted behind one window and a block 23 with a semi-reflecting surface 24 behind the other, so that all the imaging rays pass through a single viewing-aperture 25. The mount 18 of the prism 17 can be rotated about a pin 19 by a screw 22. To detect and correct errors of height of the images, the screw 22 is adjusted until the two measuring marks 7 have the same height when viewed through the aperture 25. Then if the images as seen through this aperture do not coincide as to height the prisms 14 are rotated until such coincidence is obtained. Other forms of the optical elements within the casing 15 are described; for example in Fig. 3, these elements comprise at one end a pentagonal prism 28 with a roof-edge, and at the other end a block 29 as above described. Between the prism 28 and block 29 is a telescope 32 of unit magnification which can be rotated about a pin 33 to bring the mark images to the same height. The casing 15 may form a permanent part of the rangefinder instead of being separate as above described, in which case it is provided with a pair of eyepieces and the optical elements within it are so mounted that they can be turned into their position of use to direct all the rays into one eyepiece, or out of this position so that both eyepieces are used in the ordinary way. A construction is also described for applying the invention to a binocular rangefinder in which measurements are effected by giving the same virtual distance to two stereoscopic images produced by two rangefinder systems of different bases, such an instrument not having measuring marks.