Patent GB-605481-A (GB)
Title: Improvements in or relating to range finders
IPC: G03D7/00
Filed: 1945-12-20
Abstract: 605,481. Range-finders. KODAK, Ltd. Dec. 20, 1945, No. 34560. Convention date, Jan. 19, 1943. [Class 97 (i)] In finders having two spaced windows from which beams are respectively directed to form images in comparison planes by portions of an optical system which includes at least one lens, to compensate for errors caused by disarrangement of the parts the range scale comprises a scale and index light from one of which is projected through both portions of the optical system to form an image adjacent the other or adjacent an image thereof. Alternatively the scale and index are projected respectively by the two portions of the system. The projected image or images may be visible in the eyepiece or eyepieces of the rangefinder or at a different viewing position. Various applications of the invention to coincidence and stereoscopic finders are described. In the coincidence finder shown in Fig. 2 the object beams from prisms 60 are focussed by lenses 61 on to the surface 65 of a double prism 63 for observation through an eyepiece 66 by cross reflectors 62, a light deviator 71 being moved to effect coincidence. The prism 63 bears an index 69 illuminated by lamp 68, light from the index being reflected at the semi-transparent surface 64 and thence via one of the mirrors 62 to one of the prisms 60 and thence via a small prism 72 cemented thereto to a similar prism 72 on the other entrance prism 60 whence the beam forms an image on the surface 65 adjacent a scale engraved thereon. Movement of the adjuster 71 also moves the index image and enables,the range to be seen in the eyepiece, any movement of the object images being accompanied by a similar movement of the index. Mirrors 62 may be replaced by a prism system movable transversely to effect coincidence and incorporating both scale and index or they may both be carried by the eyepiece graticule images of scale and index being projected, one through each branch of the finder on to a reflector between prisms 72 and thence to a screen. Alternatively the backs of the mirrors 62 may also be reflecting and a separate system employed for projecting the index and for observation of the scale and index image. Other modifications of this arrangement are described. The ortho-pseudo stereoscopic finder shown in Fig. 15 comprises reflectors 181 and objectives 182 forming images 184 at field lenses 183 observed in eyepieces 189 by lenses 185, 186 and prisms 187, 188. Light from each of the images 184 is intercepted by prisms 191 and a lens 192 thereby forms an inverted image of each image 184 below the other, these images also being seen in the eyepieces. A light deviator 190 is adjustable to effect stereoscopic coincidence of the images. One of the lenses 183 carries an index 196 light from which after passing throughout the system by reflectors 181 and prisms 197, 198 forms an image adjacent a scale 200 on the lens 183 observed through an eyepiece 202. Alternatively the scale and index may be seen in the eyepieces 189. An ortho stereoscopic range-finder is also described in which the prisms 191 and lenses 185 and 192 are omitted, the illuminated index is on one of the comparison planes 184 and an image thereof is formed against a scale on the other to be observed through a separate eyepiece. Specifications 605,482, 605,483, 605,484, 605,485, 605,486 and 605,487 are referred to. The Specification as open to inspection under Sect. 91 describes the modification shown in Fig. 21 (Cancelled) comprising a coincidence finder in which images from mirror 120 and semi-transparent mirror 121 are superimposed on the object plane 124 of an eyepiece 126 by a lens 122 and erecting prism 123. Coincidence is effected by rotating mirror 120 by rod 254 and cam and follower 252 and 253. The shaft 251 of the cam also rotates a disc bearing a spiral range scale 257. Light from a lamp 258 passes through the scale and is reflected by prism 143 into the prism system 123 whence it passes through mirror 121 and is reflected by the surface of a prism 133 on the mirror 120 to pass through a dove prism 135 on mirror 121 and thence be focussed adjacent fiducial marks 260 on the plane 124. When in adjustment the image of the scale will fall between the marks 260 and the range be read thereat, but should the parts be derranged the image of the scale will be displaced and the finder may be readjusted by moving the mirror 121 until the scale image once more falls between the marks 260. Alternatively both scale and index may be carried on the plane 124 or on the adjacent face of the prism system 123 an image of the index after reflection throughout the system being formed adjacent the scale. This subjectmatter does not appear in the Specification as accepted.