Patent GB-223610-A (GB)
Title: Improvements in and relating to gyroscopic stabilisation as applied to cameras and other optical instruments
IPC: G01C21/18
Filed: 1923-08-31
Abstract: 223,610. Henderson, Sir J. B. Aug. 31, 1923. Aeronautical apparatus.- Consists in gyroseopicallycontrolled optical apparatus for use on a moving platform, whereby the effects on the field of view of any angular movement of the body are annulled. The optical apparatus is rigidly attached to the platform, and a gyroscope controls a prism in the optical system to eliminate lateral movement of the image and the effects of pitching. The effects of rolling or yawing are eliminated by gyroscopically controlling a rotary member in the focal plane, for example by means of a relay device controlled by a gyro-compass. The prism is adjustable about its stabilized axes to compensate for straying of the gyro axis ; this compensation may alternatively be effected by manual means for causing precession of the gyroscope. In the. form shown, as applied to a camera mounted on aircraft, the camera 40 is mounted, with its axis fore and aft,. on a frame 13 on which is trunnioned at 10, 11 about an horizontal axis, a frame 7 supporting a gyroscope 1 in a gimbal ring 4. The trunnion 5 of the ring 4 is hollow, and contains a spindle 15 the ends of which carry forks 16, 17. The fork 17 has pivots 20, collinear with the trunnion axis 10, 11, supporting a right-angle prism 18 of the roof type having its roof edge uppermost and its two pentagonal faces vertical and horizontal, the vertical face being opposite the camera objective 41, and the horizontal face directed towards the earth. The spindle 15 is bored axially to receive a pin 22 pressed by a spring against bell. crank lever 52 adjustable by a screwed pin 53 passing axially through the trunnion 10. An arm 28 on t'he pin 22 carries rollers 27 resting between projections 25, 26 on arms 24, 23 carried respectively by the spindle 15 and the trunnion 5 and drawn together by a spring. The surfaces of the projections 25, 26 in contact with the rollers 27 are oppositely inclined to the vertical plane of the trunnion axis 5, 6, This arrangement stabilizes the prism about the axis 15. The fork 16 has pivots 31 supporting an arched arm 30 straddling the gyroscope and carryving at its free end on an axis 33 a roller resting on a plate 34 on the gyro casing, the surface of the plate, and the line joining the centre of suspension of the gyroscope to the centre of the axis 33 being equally inclined to the plane of rotation of the gyroscope. The axes 36, 33 being equidistant from the gyro axis 2, any angular movement of the frame 7 about the axis 2, produces an angular movement of the arm 30 of half the extent and this movement is communicated to the prism 18 by a parallel linkage 35, 37. This arrangement " semi-stabilizes " the prism about the axis 20, and the image in the focal plane of the camera is therefore completely stabilized as regards lateral movements and the effects of pitching. Straying of the gyro axis from the vertical is detected by telescopes 45<1>, 46<1> viewing the air or haze horizon, or low-lying distant clouds, in directions at' right angles through prisms 45, 46, the mounting being such that the fields of view are stabilized. Correction for straying is made either by manual means for causing precession of the gyroscope, or by adjusting the prism about the axes 15, 20 respectively by operating the screwed pin 53 to cause the rollers 27 to vary the angle between the arms 23. 24. and bv manipulating an adjusting-nut 50 to tilt' the whole frame 7 round the trunnions 10. 11. Rotation of the stabilized image in the focal plane relative to the unstabilized sensitive surface due to yaw is compensated by mounting the camera back 62, Fig. 3<a>, carrying the plateholder 60, so that it may rotate about the optical axis of the camera, and controlling its angular position through sector and pinion gearing 63, 64 from a step-by-step motor 65 automatically controlled from a gyro compass, such as that described in Specification 188,390, [Class 97 (iii), Thermometers &c.]. Relative rotation of the image and sensitive surface due to roll is compensated, in the modified arrangement shown in Fig. 4, by introducing between the frame 7 and the gimbal ring 4 a follow-up ring 70 carrying a worm sector 71 gearing with a worm 76 on the shaft of a motor 75 on the frame 7. The direction of rotat'ion of the motor is controlled by the gyroscope (not shown) by means of a two-part commutator 72 on the sector 71, cooperating with a contact roller 74 on the gimbal ring 4. The motor shaft carries the armature of a transmitter driving a motor 79 which effects rotation of the shutter frame 62 through the .sector and pinion gear 63, 77. The corrections for yaw and roll are communicated simultaneously to the sector 63 by causing the motors 65, 79 to actuate the driving pinions of a differential gear 78, the differential shaft of which carries a pinion gearing with the sector. Stops are fitted between the gimbal ring 4 and the gyroscope and frame 7 to limit the freedom of the gyroscope and avoid fouling of the parts in the even of a heavy bank or dip of the aircraft. Specifications 6977/15; and 16669/15, 155,053, and 165,028, [all in Class 97 (iii), Thermometers &c.] also are referred to.