PURPOSE: To obtain the more accurate information of an object, by allowing flip- flop to store that the output of a threshold element is reversed from the initial value thereof while performing the continuity of a resetting transistor by the stored output thereof to reset the output of a photosensor.

CONSTITUTION: When a RESET signal comes to zero, a transistor 1 is brought to a discontinuity state and the charge of a capacitor 2 is discharged by the photocurrent of a photodiode 3 to be gradually increased as shown by the drawing (b). When this voltage Va becomes larger than the threshold voltage Vth of a threshold element, the output Vb thereof is reversed to zero as shown by the drawing (c) while a flip-flop 5 is set as shwon by the drawing (d) and Q becomes equal to 1. When the flip-flop 5 is set, the output of an OR gate 6 also comes to 1 as shown by the drawing (e) and, by this mechanism, a reseting transistor 1 is brought to a continuity state to form formulae Va=0, Vb=1. The flip-flop 5 stores and holds this state until the next reset signal RESET is applied and, therefore, Q(Q) can be employed as the output of a light receiving intensity measuring circuit.