Patent GB-1100701-A (GB)
Title: Improvements in or relating to combined viewing and sighting instruments
Inventor: WALLER WILLIAM ALBERT
IPC: G02B23/10
Filed: 1953-12-24
Abstract: 1,100,701. Range finder systems. MINISTER OF TECHNOLOGY. Dec. 15, 1954 [Dec. 24, 1953], No. 35942/53. Heading G2J. [Also in Division F3] A viewing and sighting instrument comprises in combination a unit magnification periscopic system, a binocular periscopic system and a range finder unit which can inject into the binocular system the images of a range scale and of two pointers arranged at opposite ends of the base of the range finder unit, the images of the range scale and one of the pointers being movable to enable the range of a target to be indicated when the images of the pointers and the target are viewed in the binocular system in requisite relative positions. Referring to Fig. 1 the unit magnification periscope comprises prisms 5 and 6, and the binocular system comprises lenses and prisms 8, 9, 10, 11 and 12. Interposed between the ocular and object prism is a strip of transparent material 13 which can be turned about an axis so as to inject into the vision system an image either of the range finder scales from the range finder unit 14 or of applied tangent elevation from a unit 31. The range finder comprises block prisms 15, 16 (Fig. 3) having their diagonals half silvered and rearwardly divergent from each other. The outer faces of these block prisms, i.e. those remote from one another, are curved outwardly and are silvered, except for a small central portion, to form concave reflecting surfaces. The central unsilvered part of the outer faces of each block prism has arranged in register therewith a graticule disc. One graticule disc 17, which bears a transparent arrow-shaped part or wander mark is associated with the block prism 15 whilst a graticule disc 18, which has a transparent arrow-shaped part and a segmental part of about one quarter of the disc with an arrow adjacent thereto, is associated with the block prism 16. Some of the light entering the front of the periscope need not pass through the object prism 5 but can pass to two light collecting prisms 19, 20, in the range finder. These light collecting prisms are arranged one on each side of a median line between the two block prisms and are equi-distant therefrom. Lenses 21, 22, are preferably arranged one between each light collecting prism and the source of light. Light entering the light collecting prism 19 is directed downwardly to the first of a series of three prisms 23, 24, 25, by which the light is firstly directed outwardly below and beyond the block prism 15, then upwardly and then inwardly on to the graticule disc 17. Light passing through the transparent wander mark traverses both the block prisms 15, 16 on to the concave reflecting surface of the latter block prism which collimates the light, i.e. reflects it as parallel beams, to the half silvered diagonal of the block prism 16. Here the light is turned and directed on to the under face of the transparent strip 13 interposed between the object prism 5 and the ocular prism 6 which is inclined downwardly and forwardly. The reflection of the wander mark can thus be observed in the binocular system. In like manner light passing to the light collecting prism 20 is directed downwardly and thence through a series of three prisms 26, 27, 28, on to the graticule disc 18 associated with the block prism 16. Light passing through the transparent parts of the graticule disc (segmental portion and two arrows) is directed on to the concave reflecting surface of the block prism 15 and from thence on to the transparent strip 13 by way of the block prism diagonal so that this reflection can also be observed in the binocular system. The wander mark reflection injected into the binocular system from the diagonal of the block prism 16 also passes through a lens 29 adjacent and parallel to the front face of the said block prism, which lens is adapted to be moved laterally relatively to the block prism. This movement is controlled by rotation of a knob which also rotates a disc 30 which is provided with a transparent annular part ajacent its perimeter with a range or distance scale around it. This range scale disc is disposed parallel to the graticule disc 18 and extends between the said graticule disc and the prism 28 so that part of the annular transparent part and the range scale adjacent thereto is always in register with the segmental transparent part of the graticule disc. By this arrangement a part of the range scale is also injected into the binocular system from the diagonal of block prism 15, the part being so injected changing as the control disc 30 is rotated. By movement of the lens 29, with rotation of the range scale disc 30, the image of the wander mark can be deflected until, in the binocular system, it is brought into register with the corresponding mark or arrow injected into the binocular system from the diagonal of block prism 15 whereupon the distance of the target, which is also brought into into register with the marks, is indicated by the image of the second arrow on the graticule disc 18 on the part of the range scale reproduced in the binocular system.