Rangefinder for photographic cameras - with measurement based on accurate marking of middle of pulse or batch of pulses

摘要

The rangefinder has a transmitter, a radiation receiver and a control circuit which on reception of a pulse or a batch of pulses by the receiver, delivers to an evaluation circuit a control pulse stopping a time measuring process. A signal evaluation stage (2-11) generates a signal marking the middle point of each received pulse (1) or batch of pulses. The input stage includes a differential unit with a capacitor (2), a diode (3) and a coupling capacitor (4) leading to a delay element (11) leading through a resistor (9) to an operational amplifier (5).