Automatic focusing system with phase difference detecting unit employing correlation operating circuit

摘要

A phase difference detection unit for an automatic focusing system of a camera or the like. The phase difference detecting unit includes a pair of linear image pickup devices which receive a pair of optical images of an object formed by the lens in the automatic focusing system of a camera or the like. The detecting unit also has a correlation operating circuit which determines whether or not the lens of the focusing system is in a proper focus condition. The proper focus condition is determined by a minimum correlation value output by the correlation operating circuit, the value being indicative of the correlation between a pair of phase shifted analog electrical signals representative of the optical images received by the pickup devices. The correlation operating circuit is capable of operation at high speed with improved accuracy by maintaining the capacitive loads of the input terminals of the correlation operating circuit.