| 摘要 |
PURPOSE:To generate a shift pulse at invariably constant timing on the same brightness condition by providing a reference signal generating circuit which is similar to a monitor circuit in terms of characteristics of elements and circuit constitution, and generating a reference signal to be compared with the output of the monitor circuit. CONSTITUTION:The photoelectric conversion block of a focus detector consists of a self-scanning type image sensor PA such as CCD, image signal output circuit VS, brightness monitor circuit MC which operates according to a photodetecting element MP for brightness monitoring, and a reference signal generating circuit RS, etc. This circuit RS is constituted similarly to the circuit MC in terms of characteristics of elements and circuit constitution, and the signal that the circuit RS outputs in a steady state after the initialization wherein the stored charge of the sensor PA is cleared with an integral pulse goes to the reference signal to be compared with the output of the circuit MC, performing focusing detection. Consequently, a shift pulse is generated at invariably constant timing on the same brightness condition without any influence to be exerted upon source voltage variation, etc., which generates a noise, so that the focusing detection is performed excellently. |
