Patent GB-381091-A (GB)
Title: Improvements in, or relating to, range-finders
IPC: G01C3/14
Filed: 1932-03-17
Abstract: 381,091. Rauge-finders. ZEISS, C., [Firm of], Carl-Zeiss-Strasse, Jena, Germany. March 17, 1932, No. 7923. Convention date, March 28, 1931. [Class 97 (i).] A device for testing the adjustment of rangefinders, comprising two systems of reflectors for dividing the rays from a single source of light and directing them as parallel rays to the entrance apertures of the range-finder, the systems having two different positions of use giving equal and opposite reflective errors so that these errors can be neutralized, is characterized by the feature that each of the apertures receives rays from approximately the whole of the cross section of the rays from the source. The form shown in Figs. 1 and 2 consists of two light sources 1, 1<1>, provided with frosted screens 2, 2<1> at the foci of collimating lenses 3, 31. The reflector systems consist of two pairs of reflectors 5, 6 and 51, 61 which can be rotated about axes 7, 7<1>, each pair of reflectors being arranged to deviate the incident rays through 90‹. The reflectors 5, 6<1> have silvered surfaces 5<11>, 6<11> and the reflectors 6, 5<1> are partly transmitting. In the position shown in Fig. 1 the light source 1 is operative, the parallel beam leaving the collimator 3 being incident on the reflector 6 by which it is partly reflected to the mirror 5 and thereby directed into one entrance aperture of the range-finder. The light transmitted by the reflector 6 is received by the mirror 6<1> and thereby directed to the reflector 5<1> by which it is reflected into the other entrance aperture of the range-finder. By turning the reflector systems to the positions shown in Fig. 2 the light source 11 becomes operative, the reflector 5<1> directing part of the light to the mirror 6<1> and transmitting the remainder to the mirror 5. Tests are made in both positions of the reflector systems in order to neutralize the reflective errors. When the range-finder is to be used for making a measurement the reflectors are turned to the positions shown in Fig. 3 in which the system 5, 6 occupies the Fig. 2 position and the system 51, 6<1> the Fig. 1 position. The reflectors 6, 5<1> then transmit light from the observed object to the entrance apertures 9, 9<1> of the rangefinder. Fig. 6 shows an arrangement for use with a stereoscopic range-finder, in which the collimating lenses 23, 23<1> are the objectives of the two telescopes. Light from a source 30 is collimated by the lens 23 and after reflection by the end reflector 26, 27 of the range-finder is transmitted by the reflector 32 and is incident on a mirror 34 which returns it along itself. Part of the light passes back through the reflector 32 and enters the eyepiece 24 and the remainder is reflected to the mirror 31 and thence to the second reflector system 31<1>, 321 by which it is directed to the end reflector 26<1>, 271 and so into the eyepiece 24<1>. The reflector systems 31, 32 and 31<1>, 32<1> are rotatable about axes 33, 33<1> and each of the mirrors 34, 34<1> can be displaced in its own plane so as to occupy either its operative or its inoperative position. To make the second test, using the light source 30<1>, the reflector systems are turned anticlockwise through 90‹ and both mirrors 34, 34<1> are displaced to the right so that the mirror 34<1> becomes operative. In using the range-finder for measuring, the reflector systems are turned so that the reflectors 32, 31<1> lie in the paths of the incident rays, and both mirrors 34, 34<1> are moved to their inoperative positions.