Patent GB-605111-A (GB)
Title: Improvements in or relating to range finders
IPC: G01C3/16
Filed: 1945-12-20
Abstract: 605,111. Range-finders. KODAK, Ltd. Dec. 20, 1945, No. 34569. Convention date, March 13, 1943. [Class 97 (i)] In a stereoscopic finder in which two images of the object are formed in comparison planes having reticle reference marks one or both of the marks is the real or vertical image of a portion of a spiral on a concentrically rotatable member, rotation of the member or members changing the relative positions of the marks in the stereoscopic field whereby the range can be measured. A finder having two such members is described adapted for height-finding. As shown in Fig. 1 the finder comprises objectives forming images in comparison planes 22, 23 by light from each prism 20 for observation in eyepieces 25. The plane 22 has a prism 32 the upper surface of which bears a reticle mask 34 illuminated by lamp 31 a virtual image of the mask being formed in the plane 22 by a reflecting surface 33 of the prism. The other mark is a portion of a translucent spiral 41 on an opaque rotatable disc 50 an image of the spiral being formed in the plane 23 by lens 43 and prisms 44, 45. On rotating the spiral until the marks and object appear to be at the same distance the range is indicated against an index 51. Fig. 8 shows a finder in which both marks comprise spirals 94, the two members 85 being simultaneously rotated for height-finding. Light from the left-hand spiral is reflected by prism 57, collinated by lens 60 and passes into the rangefinder by prism 62 to form an image in the right comparison plane. Similarly an image of the right spiral is formed in the left comparison plane by prism 58, lens 59 and prism 61. Each disc is on a shaft 87 having a sprocket 88, Fig. 9, driven by gears 89 on a ring 90. The ring may be rotated either by a gear 96 on a shaft 97 or by a gear 91 on a shaft 92 rotated by worm drive from shaft 95. The shaft 97 has a gear 100 engaging a fixed quadrant 101, Fig. 8, so that rotation of the instrument in elevation causes the gear 100 to ride over the quadrant and to rotate the shaft 97 and hence the discs 85 in opposite directions. The spirals are so designed that their displacement by such rotation is proportional to the sine of the angle of elevation. Rotation of the shaft 95 to effect stereoscopic coincidence is effected by knob 110 through gears 112, the height being read directly on a scale 113. In a modification, not adapted for height finding, one disc is omitted and is replaced by a fixed reticle mark an image of which is found by the lens in the other comparison plane. The Specification as open to inspection under Sect. 91 describes also the modification shown in Figs. 7, 8-(Cancelled), in which the object is observed directly by prisms 70, 70 and the reticle marks comprise respectively a circle 75 and a spiral 76 on a disc 74 rotatable in the roof of the casing. Light from the marks is directed by prisms 78 on to the concave reflecting surfaces 72 whereby it is collimated to pass through the observation aperture 73 so that the mark images appear at infinity. As before rotation of the disc permits measurement of the range. This subject-matter does not appear in the Specification as accepted.