PURPOSE: To entirely remove influence of shading, etc., and also to obtain a digital signal having image resolution corresponding to the number of photodetectors, as to an outputting circuit for the photodetector, which is used when fetching a picture signal generated as an analog signal, as a digital signal, in an automatic focus controller of a camera.

CONSTITUTION: An odd rank and an even rank being adjacent to each other form a pair as to plural photodetectors which are adhacent to each other and have been linearly arrayed, and each photodetecting output is sent out in order from the first shift register and the second shift register. Each output (a), (b) is held in order by capacitors C1, C2, and is reset in order after becoming in a mutually overlapped time relation. A comparator CP sends out a signal only when a level difference between 2 holding values has exceeded a prescribed value, that is to say, when there is such an incident light quantity difference. Accordingly, a slow incident light quantity variation generated by a circumferential aberration, etc. of a lens is neglected, and the purpose is attained.