| 摘要 |
PURPOSE:To permit optional changing of the telphoto end and wide end of a zoom lens, and to make zooming operation fast by adding a window comparator, etc. to a speed control servo circuit. CONSTITUTION:A switch SW1 is turned on to connect a window comparator consisting of operational amplifiers 2 and 3 to a servo circuit. When a servomotor M is driven by the operations for setting of potentiometers P2-P4, the input terminal voltage of an amplifier 1 is made zero by the bias applied upon a diode D1 and the motor M stops. In this case, the zoom lens operates as a speed control type servo between the set value W1 and a telephoto position T1, and operates as an optionally settable position control type servo circuit at the value W1 and the position T1. |
