Patent GB-768863-A (GB)
Title: Photogrammetric rectification projector
IPC: G03B27/68
Filed: 1954-12-29
Abstract: 768,863. Photogrammetry. ZEISS-STIFTUNG, C., [trading as ZEISS, C. [Firm of]]. Des. 29, 1954 [Jan. 2, 1954], No. 37509/54. Class 97(2) In a photogrammetrical rectification projection having angularly fixed objective 2 and tell-tale object and image planes (Figs. 1a and 1b respectively) and an inverter to maintain the image in focus at any angular position of the image plane, by tilting the object plane, the image of the centre point of the object is prevented from being displaced, or tilting the image plane, by moving the object in the object plane in two directions at right angles through distances determined by an approximate formula. The movement of a body 30 (Fig. 2), is proportional to one factor A, of the formula and means are provided whereby the product of this with the tangents W<SP>1</SP> and W<SP>2</SP> of the image table 3 inclination in two mutually perpendicular directions produce displacements V<SP>1</SP> and V<SP>2</SP> of the photograph 1 in the object plane 1 in these directions. As shown in Figs. la, 1b and 2 the multiplying is performed electrically. Table 3 is supported in spherical bearing 4 and both slides 6 and 7 move in the direction of W<SP>2</SP> whereas only slide 6 moves in the direction W<SP>1</SP>. On setting pointer 16 to the focal length fa of camera which took photograph 1, the angle through which the pointer is turned is proportional to fa<SP>2</SP>/fe<SP>2</SP> (fe being the focal length of the projection objective 2) and housing 18 is displaced proportionally by its screw-threaded engagement with shaft 17. The angle through which flexible shaft 21 is turned is proportional to the projection magnification n and cams 23 and 24 displace roller 29 through a distance proportional to 1/n<SP>2</SP> so that the total movement of body 30 (including an initial unit displacement from the zero position) can be arranged to be equal to A constant e.m.f. E 2  is applied to resistance 75 and a sliding contact 74 is connected so that the potential difference e 2  =E 2 A/L 2  is applied to the ends of resistances 71 and 73 having sliding contacts 70 and 72. The resulting potential differences are proportional to Aw 1  and Aw 2  servomotors 76 and 77 move sliding contacts 80 and 81 along resistances 82 and 83 until the potential at 80 is equal to the potential 70 and the potential at 81 is equal to the potential at 72. Cam 24 rotates at ten potential at 72. Cam 24 rotates at ten times the speed of cam 23 and is only operative for the smaller values of 1/n<SP>2</SP>, when cam 23 becomes inaccurate. As shown in Fig. 4b, the multiplying is performed mechanically and the inclination of bars 35 and 37 is set by the mechanism in housing 18 and the racks 39 and 51 are displaced along the axes of pinions 41 and 54 respectively by movements of the slides in the directions w 1  and w 2  respectively. Due to the slopes of bars 35 and 37, a perpendicular motion is imparted to the racks by these displacements and the pinions are thereby rotated through angles proportional to A.W. The latter rotation is transmitted to the photograph displacing means by shafts 42 and 57. Block 51 is slidable on rack 52 so that movements of slide 6 in the direction of w 1  are not imparted to it.