| 摘要 |
PURPOSE:To enable the execution of detecting operation at a high accuracy corresponding to various luminous intensities, by performing a discharging of the energy charged in a photodiode by the amount corresponding to the quantity of input light after a precharging thereof. CONSTITUTION:A photodiode 11 is, first, precharged by a precharging command and then, discharged at a speed corresponding to the quantity of light detected to be inputted under a condition as existing at the end of the precharge. Then, in the process of the discharging, an electric charge level stored in the photodiode 11 is checked with a detection element 16. Then, with the electric level above a specified value, a counting circuit 22 is driven to count while with the electric charge level falling below the specified value, the counting operation is stopped. Thus, the counts of the counting circuit 22 correspond to the quantity of light to be detected to obtain a highly accurate light detection output corresponding to the counting state of the counting circuit 22. |
