GB1457995A - Scanning element assembly - Google Patents

Abstract

1457995 Optical scanning PERKIN-ELMER CORP 23 May 1975 23025/75 Heading G2J [Also in Division F2] A scanning element, e.g. a mirror, or telescope, is mounted together with a counterbalance for rotation in opposite directions about parallel, preferably coincident axes, the element and counterbalance engaging, via a spring and a stop, at the limit of a scan such that the spring exerts a force to reverse the direction of motion of both the counterbalance and element, a motor being provided to initiate scanning motion at the required velocity. A scanning element may be mounted in this manner in a space vehicle so as to cause the minimum disturbance to its support and thus to minimize the risk of the vehicle's attitude being altered. In the embodiment illustrated, a mirror 10 carried in a mounting frame 15 and a counterbalance 11 are supported for independent rotation about the same axis on a pair of bifurcated brackets 12a, b and 13a, b mounted on a base 14, e.g. a portion of a space vehicle. Box-like portions 16, 17 projecting from the ends of the frame 15 each house a bracket bifurcation 12a, 13a while box-like portions 35, 39 projecting from the ends of the counterbalance 11 each house a bracket bifurcation 12b, 13b. The frame 15 is rotatably supported on the bifurcations 12a, 13a by short shafts 18, 28 journalled in bearings 19-21, 29-31, respectively, while the counterbalance 11 is rotatably supported on the bifurcations 12b, 13b by short shafts 32, 33 journalled in bearings 36- 38, 40-42, respectively. The cyclic reversal of the mirror 10 and counterbalance 11 is achieved by buffer leaf-springs 47-50 mounted on the frame 15 co-operating with limit stop pins (43a), 43b, (44a), 44b, (45a), 45b, (46a), 46b mounted on the counterbalance 11, which springs during each reversal absorb the kinetic energy of the system, convert it into potential strain energy, and then return it to kinetic energy again. In operation Figs. 3a, 3b and 3c, (not shown), the frame 15 and the counterbalance 11 oscillate in opposite directions, 180 degrees out-of-phase, the length of the scan path being determined by the spacing of the pins in each pair (43a), 43b, &c. Motive power is provided by a D.C. torque motor comprising a wound stator 55 mounted in the interior of a projecting portion 34 of the counterbalance 11 and a rotor 56, which is an annular permanent magnet mounted around a flange 57 projecting outwards from the portion 16. A second D.C. torque motor is provided between the-base 14 through bracket 13 and the counterbalance 11 for changing the midscan angle of the mirror 10 with respect to the base 14. This motor comprises a wound stator 58 mounted within an annular flange 59 projecting from the bifurcation 13b and a rotor 60, which is an annular permanent magnet mounted around a flange 61 that projects inwards from the outer endwall of the portion 39.