Patent GB-859886-A (GB)
Title: Improvements in or relating to cameras
Inventor: BAUER PETER
IPC: G03B19/18
Filed: 1958-10-01
Abstract: 859,886. Lens turrets. PYE Ltd. Sept. 29, 1959 [Oct. 1, 1958], No. 31364/58. Class 97(1) A camera provided with a lens turret on which is mounted a number of lenses, each incorporating an iris diaphragm, movable selectively into an operative position in which the optical axis of one lens is in alignment with the optical axis of the camera, wherein each iris diaphragm is provided with a control ring for the adjustment of the size of the aperture thereof, which, when the lens associated with that iris diaphragm is in the operative position, is rotatable by means of a servo motor controlled from the output of a bridge circuit including a pair of potentiometers, one of which is adapted for manual adjustment, and the other of which is adapted to be adjusted by the movement of a cam follower which engages the profile of a cam rotatable with the iris diaphragm control ring of the lens in the operative position. The invention is shown as applied to the lens turret described in Specification 706,922, the diaphragm control ring 5 of each lens having connected thereto a gear segment 59 and a cam 64. When the selected lens moves into operative position, the segment 59 and cam 64 associated therewith respectively engage a gear 60 and a cam follower 65, the gear 60 being coupled by a shaft 61 to a servo motor 11 and the cam follower forming the slider of the potentiometer 66. This potentiometer and a potentiometer 14 which has a manually adjustable slider 14a are connected in a bridge circuit 13 through a control device 12, such as an amplifier or a direction sensitive relay, to the motor 11. Hence, if the setting of the diaphragm of the operative lens does not correspond to that set by the slider 14a an unbalance voltage drives the motor 11 so as automatically to adjust the diaphragm setting. Conversely, an alteration of the manual adjustment of slider 14a unbalances the bridge and the motor 11 rotates the control ring 5 so as to displace the cam follower 65 and so adjust the potentiometer 66 to restore balance. The cam follower 65 is spring mounted in a spring loaded slide 50 formed with a nose 56 which rides on the inner surface 57 of the turret during rotation thereof and moves into a notch when the turret reaches an indexed position so that the cam follower 65 and the gear 60 will only then engage the cam 64 and segment 59. Lenses having different ranges of aperture size may be accommodated on the same turret by linking the cam 64 to the control ring 5 through a lost motion device, whereby the cam may be movable relative to the diaphragm control ring 5 to positions beyond the maximum or minimum useable aperture size. A second manually operable potentiometer may be positioned at a remote point and switched into the bridge network 13 in place of the manually operated potentiometer 14, 14a by a double pole switch. The cam follower 65 may be mounted on the camera body instead of in a boss 49 around which the turret rotates. And in addition to the iris diaphragm control, and as an alternative control of the light transmission, an optical wedge light filter may be rotatably mounted in front of the camera pick-up tube, rotation of this filter being controlled by another servo motor connected to a potentiometer, the slider of which is coupled to the filter so as to be moved when the filter is rotated. The potentiometer 14 used for manual adjustment of the diaphragm setting, may, through a changeover switch, alternatively be used to control the filter rotation from a maximum density to a minimum density position.