GB1450027A - Optical apparatus - Google Patents

Abstract

1450027 Stabilizing optical equipment; automatic control DEFENCE SECRETARY OF STATE FOR 9 July 1971 [9 July 1970] 33497/70 Headings G2J and G3N Optical apparatus includes means for compensating for movement thereof which would otherwise result in corresponding relative motion of the optical image in the apparatus. In one particular embodiment, a reference gyroscope 11 has a casing secured to an inner gimbal 12 for angular movement about a pitch axis 13 in an outer gimbal 14 supported for angular movement about a yaw axis 15 in a frame (represented by the ground sign 16). A television camera 17 is supported on the frame 16 and provides an optical image at a viewing presentation (not shown) of an object seen along its optical axis 18 by the camera. Two double Dove prisms 19, 20 are supported on the frame 16 for angular motion about mutually normal support axes 21, 22. These axes are normal to the axis 18 and are respectively parallel with the gimbal axes 13, 15. Pick-off means 23, 24 afford control signals responsive to angular motions of the gyroscope 11 with respect to the inner gimbal 12 and are connected through corresponding pitch and yaw amplifiers 25, 26 to pitch and yaw torque motors 27, 28, respectively, which are operative to drive the prisms 19, 20 through drive-shafts 29, 30, respectively. Pivoted linkages having arms 31, 32 and 33, 34 connect inner gimbal 12 to drive-shaft 29 and outer gimbal 14 to drive-shaft 30, respectively. The lengths of the arms 32, 34 are twice that of the arms of the gimbals 12, 14, respectively. In operation, if the apparatus is rotated with respect to the pitch and/or yaw axes 13, 15 the image produced by the camera 17 would normally move correspondingly on the viewing presentation, but in this case signals proportional to the angular displacement of the gyroscope rotor with respect to its casing are fed from the pick-off means 23, 24 through the amplifiers 25, 26 to the torque motors 27, 28. At the same time, the relative movements of the inner and outer gimbals 12, 14 with respect to the frame 16 are operative through the linkages 31, 32 and 33, 34 to rotate the prisms 19, 20 through half the corresponding angular motion of the gimbals. This double control movement of the prisms has the effect of compensating for image movement which would otherwise take place as a result of movement of the camera. The control signals fed to the torque motors 27, 28 effectively comprise negative feedback signals whereby the prisms 19, 20 and the gimbals 12, 14 are turned until the pick-off means 23, 24 agains give a zero output.