| 摘要 |
<p>When light enters a photodiode (PD), charge the amount of which corresponds to the intensity of the light is generated, and the level of the amount of charge is determined by an amount-of-charge level determining circuit (20). The capacitance of an integration capacitor section of an integrating circuit (10) is determined according to the determined level of the amount of charge by a capacitance setting circuit (30). The charge produced in the photodiode (PD) is accumulated in the integration capacitor section of the integration circuit (10), which outputs a voltage corresponding to the amount charge accumulated. When the net intensity of the background light is high and the net intensity of the incident light is high, the capacitance of a variable capacitor section of the integration circuit (10) is set to a relative large value, and therefore the intensity of the incident light is determined without saturation. When the intensity of the background light is low, the capacitance of the variable capacitor section is set to a relatively small value. Therefore the intensity of the incident light is determined with good sensitivity irrespective of the ambient condition.</p> |
