PURPOSE:To obtain adequate quantity detection data without complicating a signal processing circuit, by judging the magnitude of reference voltage from obtained data to perform the onboard operation of reference voltage. CONSTITUTION:CCD11 is equipped with a photoelectric conversion part 1, a transfer electrode 4, a vertical transfer register 2, a horizontal transfer register 3, an output gate 5 and detection part 6. The star image condensed by an optical system 10 is formed to the light receiving surface of CCD11 and the charge signal thereof is supplied to an A/D converter circuit 13 and a comparator 19 through an amplifier 12. The comparator 19 sends out comparison output 19a at the time of an input signal large than star magnitude reference voltage 18, and A/D conversion data 13a and address data 15a are supplied to a processing circuit 17 on the basis of said output 19a through a multiple circuit 16. The circuit 17 performs judgement and control respectively so as to lower the voltage 18 when detection quantity data is little and to raise said voltage 18 when star data is much.
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