Patent ID: 7034275

Claim:
A photoelectric detector comprising: a photodiode for generating a charge in response to a quantity of an incident light; an integrating circuit, having an integrating capacitor for accumulating charge outputted from the photodiode, for outputting a voltage in response to the quantity of the charge accumulated in the integrating capacitor; a comparison circuit for comparing the voltage with a prescribed threshold voltage by inputting the voltage outputted from said integrating circuit and for outputting, when the voltage reaches the threshold voltage, a saturation signal showing the status of the saturation of this voltage; a charge injection circuit for injecting a certain quantity of charge, whose polarity is inverse to that of the charge accumulated in the integrating capacitor of the integrating circuit, into the integrating capacitor on the basis of the saturation signal outputted from the comparison circuit; a counting circuit for counting the number of times of the voltage outputted from the integrating circuit reaching the threshold voltage on the basis of the saturation signal outputted from the comparison circuit, wherein a quantity of an incident light is detected on the basis of the value showing the number of times counted by the counting circuit and the voltage outputted from the integrating circuit; a P/S converting circuit which receives the number of times counted by said counting circuit as an input as a parallel digital value and which serially outputs said digital value; and an S/P converting circuit which receives a digital value serially outputted by said P/S converting circuit as an input and which converts said digital value to a parallel digital value and outputs said parallel digital value.