JPS55121413A - Focusing detector - Google Patents

Abstract

PURPOSE: To obtain focusing position with good accuracy by amplifying the output signals of a photoelectric transducer group by the use of the mean value signal in the previous scanning without deteriorating the S/N of the signals at the time of processing the output signals of said group.

CONSTITUTION: The time series video signals A obtained by scanning a photoelectric transducer group 1 are integrated by a mean value detecting circuit 2 and at the time when the integration is over, their mean voltage value B is held. Next, at the time of performing the second scanning, the comparison of the new time series video signals C with A is executed in a differential amplifier 3, by which the differential signal absolute value D is obtained. Next, the differential signal absolute value D is subjected to integration in an adder 5 via nonlinear type circuit 4, whereby the signal E is obtained. The scanning is done in this way, whereby the maximum value of the integration operation is displayed and the focusing point position detected. Here, the mean value signal of the previous scanning is used at the time of processing the output signal of the photoelectric transducer group and therefore the output difference is made large by the subject, hence the signals may be amplified without deteriorating their S/N and the focusing point position obtained with good accuracy.

COPYRIGHT: (C)1980,JPO&Japio