GB1442773A - Optical stabilizer - Google Patents

Abstract

1442773 Automatic control OPTICAL RESEARCH & DEVELOPMENT CORP 9 July 1973 32597/73 Heading G3N [Also in Division H4] In an optical device for observing an object ( a telescope) subject to accidental motion (e.g. hand held) one of the elements (a mirror B) is angularly movable relative to the optical axis 16 and its deviations are detected by sensors whose signals control means for adjusting a restoring force, the restoring force being varied in proportion to the time averaged angular displacement. The arrangement is such that small, rapid movements are compensated by the inertia of the mirror while the invention causes the mirror to follow up slower movements. The mirror is suspended by an axial filament and is immersed in a damping fluid. As shown the sensors comprise "metal detectors" 27, 29 which co-operate with a metallic ring 25 on the back of the mirror. They are oscillators arranged to give a D.C. output whose polarity depends upon the direction of the displacement and zero output for no displacement. The signals control motor driven potentiometers 40, 60 which adjust the current through electromagnet coils 50, 70 whose fields react with a permanent magnet J on the back of the mirror. Stiction in gearing between motors and potentiometers provides a dead band. It is stated that the electro and permanent magnets may be interchanged. In one alternative embodiment, Fig. 4, (not shown) the motors rotate permanent magnets in a gap in each yoke K, L to vary the strength of the resulting field; this replaces the electromagnets. In another embodiment, Fig. 3, (not shown) the sensors are photo-electric devices in a bridge circuit and receive light from a solid state source reflected from a mirror attached to the back of the permanent magnet J. Control is effected as in Fig. 2 except that the output of the bridge is connected through separately adjustable proportional, differential and integrator networks. In a final embodiment Fig. 5, (not shown) the suspension filament is attached at its rear end to a rod, pivoted in a diaphragm, whose further end is moved orthogonally by servo-motors through rack and pinion links, the detectors being as in Fig. 2.