Camera focus detecting device

摘要

An automatic focus detecting device for a camera in which a self-scanning photoelectric element array is scanned at a rate depending upon the average amount of light reflected from an object being photographed so that accurate focus detection is maintained over a wide range of illumination conditions. An average illumination detecting element is disposed at a position near or at a position optically equivalent to that of the microphotoelectric elements of the element array. A low-pass filter couples the output of the average illumination detecting element to a clock pulse generator which produces clock pulse signals of which the frequency varies according to the smoothed output signal from the low-pass filter representing the average illumination. As the brightness of the object increases the frequency of the clock pulse signal correspondingly increases to compensate for variations in brightness of the object.