Patent GB-747343-A (GB)
Title: Improvements in or relating to stereo-comparator apparatus
IPC: G01C11/00
Filed: 1952-01-24
Abstract: 747,343. Stereogrammetric apparatus. WASSEF, A. M. Jan. 21, 1953 [Jan. 24, 1952], No. 2025/52. Class 97 (1). Stereo - comparator apparatus is provided with electrical elements which register with the X and Y co-ordinate reference. lines of a reference grid and electrical contacts carried'by a member which is movable together with the optical unit of the apparatus, the contacts serving to connect together the elements corresponding to a selected reference point, the apparatus further comprising electrical storage or recording means which are energized through the elements and contacts. The apparatus may include a micrometer comprising a main driven element and subsidiary driven elements provided with contacts corresponding to integers and further contacts of brush or other slidable engagement form arranged to co-operate with the contacts to energize electromagnetic recording means. As shown in Fig. I, the apparatus comprises a stereo-comparator with an optical unit VS displaceable on a carriage CO at right-angles to the eye-base, and carriages C for carrying a pair of photographs each having a reference grid printed thereon. The carriages are displaceable in the X-direction (parallel to the eye base) and in the Y-direction (perpendicular thereto) by means of micrometers Mx, My, M<SP>1</SP>x, M<SP>1</SP>y. Each carriage, Fig. 5, has a frame F for the photograph, and septum 5 dividing the interior into two parts in which move arms A fixed to the carriage CO. Septum 5, which is of insulating material, has two sets of conducting strips 9, 10 embedded in its upper and lower surfaces respectively and corresponding to the lines of the reference grid on the photograph. The bottom and top inner surfaces of carriage C carry strips 7, 8 respectively, each of which is as wide as ten strips 9 or 10 and lie in the same direction. Arms A carry hemispherical contacts 1, 2, 3, 4 engaging the strips 8, 9, 10, 7. Strips 7, 8 are numbered from 0-9 and strips 9, 10 are numbered from 0-9 recurringly, so that when a point at a grid inter-section is brought to a reference mark in the eyepiece of the optical system, the co-ordinates of the intersection are recorded by the strips 7, 8, 9, 10 in engagement with contacts 1, 2, 3, 4 as a four-figure number. The micrometers not only displace the carriages by screw-threaded spindles but measure and register the displacements. As shown in Fig. 6, the screw-threaded spindle 11 of each micrometer carries a gear-wheel 12 engaging a gearwheel 13 with a gear ratio of 30: 1. The gear wheels are journalled in a fixed block 24 on the face a of which 30 radial contacts 21 (see also Fig. 8) are mounted and numbered from 0-9 recurringly, together with three other radial contacts 20 for indicating the tens digits. Contacts 21 are engaged by arcuate contacts mu, su carried by wheel 13, which contacts overlap slightly so that at least one of them is always in contact with at least one of the contacts 21. Wheel 13 also carries arcuate contacts mT, sT similarly engaging contacts 20. Contacts mu, su, mT, sT are connected to slip-rings 17 angaged by brushes bmu, bsu, bmT, bsT. By this means circuits may be established which indicate the number of revolutions of spindle 11 from a datum position. The fraction of a revolution through which spindle 11 turns is measured by means of a wheel 39, the shaft 27 of which is keyed to, but slidable in, a hollow extension 28 of spindle 11. The face b of block 24 carries a set of 50 radial contacts 50, Fig. 9, numbered recurrently on one side with even numbers 0-8 and on the other side with odd numbers 1-9. Two sets of contacts mh, sh, similar to contacts mu, su, are mounted diametrically opposite on wheel 39, and co-operate to indicate <SP>1</SP>/ 100 ths of a revolution. Tenths of a revolution are indicated by radial contacts 51 on block 24 and contacts mt, st on wheel 39. Block 24 also carries two sets of vernier contacts v0-v9 whereby 1/ 1000 th of a revolution can be indicated. The contacts on wheel 39 are connected to slip-rings 38 which are wiped by separate brushes. Normally, wheels 13, 39 are spaced from block 24, but a solenoid 26 is provided which, when energized, attracts the shaft 27 which slides in sleeve 28 until wheel 39 engages face b of block 24. Wheel 13 is also moved into engagement with block 24 by a pulley system which connects it to wheel 39. Arrangements are described (Fig. 11, not shown), whereby the micrometer readings, and also the grid square indications, are recorded. The contacts of the four micrometers are connected to contacts disposed on four symmetrical generators on the inside of a hollow cylinder. The two sets of contacts, 1, 2, 3, 4 on the arms A are connected to contacts on a pair of opposite generators.. A cylinder provided with brushes rotates inside the hollow cylinder to connect each set of contacts in turn to fixed contacts on a switch having a rotary arm bearing contacts which sweep over the fixed contacts, operating electromagnetic devices which print a series of figures giving a co-ordinate of a point to which the apparatus is set.