Phase difference detecting apparatus

摘要

A phase difference-detecting apparatus for detecting a relative distance between a pair of focused images obtained from a subject luminous flux passed through an objective lens to thereby judge a focusing state of the objective lens. The apparatus includes a pair of signal generating sections which receive the subject flux and provide first and second time series signals. A switching-capacitor integrator is provided including a plurality of capacitive elements and switching elements for intermittently connecting the capacitive elements to each other, and for receiving the first and second time series signals. A control device compares the sizes of the first and second time series signals with each other to thereby generate a control signal corresponding to a relation of size between the first and second time series signals. The switching elements are controlled on the basis of the control signal to cause the switching-capacitor integrator to generate an electric charge corresponding to an integrated value of an absolute value of a difference between the first and second time series signals, and to cause the switching-capacitor integrator to generate, as a correlation value, an integrated value on the basis of the first and second time series signals in predetermined numbers whenever the quantity of relative movement is changed. The switching-capacitor integrator includes a gain control including a plurality of switchable capacitances.