Patent GB-670581-A (GB)
Title: Improvements in or relating to television cameras
IPC: H04N5/225
Filed: 1948-03-16
Abstract: 670,581. Lens turrets. JACKSON, D., GREEN, J. D. F., and PYE, Ltd. March 10, 1949 [March 16, 1948; Dec. 17, 1948], Nos. 7843/48 and 32765/48. Class 97 (i). [Also in Group XL (a)] In a television camera having several lenses of different focal lengths carried upon a turret which is movable to position the lenses selectively in optical alignment with the pickup tube, focusing is effected by a focus control member which moves the pick-up tube relative to the operating lens through a variable ratio gear or lever in the camera and the gear ratio or the position of the fulcrum of the lever is automatically changed in accordance with the particular lens which is operative and in such a manner that the focus control member is turned or moved through approximately the same distance for focusing the camera from close-ups to infinity irrespective of the lens which is operative. In the form shown, a television camera comprises a turret 4 which is rotatably mounted on a boss 7, projecting centrally from the front wall 8 of the camera body, and has detachably mounted thereon four lens barrels of which 5a, 5b, 5c are shown. The rear surface of the turret 4 has a central recess in which is fixed a gear 9 coupled to an idler gear 14, which is rotated by a gear 15 on a spring-urged rod 20 when a handle 22 is pulled rearwards against the pressure of a spring 23 and then rotated. Thus, turret 4 rotates to move a different lens 5 into operative position when the handle 22 is pulled rearwards. When handle 22 is released, the gear 15 is clutched to a gear 30 which is coupled by a chain 31 and gears 32, 34 to gears 36, 37 of which the three gears 37 mesh with the internal teeth of a ring 38, which meshes with a gear 40 attached to the iris diaphragm of the lens in use. Thus, rotation of handle 22 when in its forward position, causes adjustment of the diaphragm opening. Gear 40 is connected to a cam 109 on the surface of which rides a tappet, slidable in the boss 7 and connected by bell-crank levers to a sylphon bellows 118 coupled by an oil pipe line 120 to another bellows 119 which actuates the pointer of a diaphragm opening indicator 117 on the rear of the camera, as gear 40 and cam 109 are rotated. On the cam surface 79 of the plate 80, by means of which each lens barrel is detachably mounted on the turret 4 rides another tappet which is also slidable in the boss 7 and is coupled by rack-and-pinion mechanism and other gearing to a rack 93, which is spring- urged upwardly at 95 and carries a bracket 94 having a pin 75, which rides in slots in levers 74 and 100 and about which the lever 74 may rock. The surface 79 is at a different distance from the axis of the boss 7 for each plate 80 so that the position of pin 75 alters as a different lens is brought into operative position. Lever 74 is connected to one end 76 to the pick-up tube 58, which is slidable in the direction of the optical axis of the operative lens along rails 59; at its other end, lever 74 is connected by levers to a focusing handle 66, connected to a similar handle on the other side of the camera by a rod 67. Thus, on rotation of either handle 66, the pick-up tube moves along the rails 59 for focusing purposes and, since lever 74 rocks about the pin 75 which takes up a different position for each operative lens, the rotation of the handle 66, in focusing the camera from close-ups to infinity, is the same for each lens. A rod 51 is connected to a pointer which co-operates with a dial on the rear of the camera to indicate the lens in use, this rod being rotated, as the turret is moved, by a gear 50 which meshes with the gear 15, when rod 20 is pulled rearwardly by handle 22 and then rotated. The slotted lever 100 constitutes a manual focusing mechanism. Specifications 670,581 and 670,608 are referred to.