| 摘要 |
PURPOSE:To obtain easily an AF lens system including an extender by making the relations between the moving extent of a focal plane and monitor pulses approximately coincident by the use of a simple multiplier for the extender. CONSTITUTION:An extender 14 assembled with a correcting means 16 is mounted between an interchangeable lens 1 and a camera 6, and signal terminals 1a and 14a are connected to 14b and 6a. The signal that goes high or low on 50% duty at 100mu pitch on, for example, the focal plane, on the lens side is received in the terminal 14a. This signal is pulled up by a pull-up resistor R1 and is applied through the terminal 14b to the camera side after the signal is multiplied twice with, for example, the extender of 1.4 times, with a multiplier consisting of a differentiating circuit of C1 and R2, a rectifier circuit 18 and a one-shot circuit 20, so that the pulse signal for monitoring is optically doubled in conformity with the moving extent (1.4)<2> of the focal plane by the extender and that the same number of the pulses with respect to the unit moving extent of the focal plane is obtained. The pulses are made correspondent with the moving extent of the focal plane with such simple multiplier. |
