| 摘要 |
PURPOSE:To surely control the quantity of light of a light beam with a high precision by switching the current/voltage conversion characteristic between the recording mode and the reproducing mode at the time of converting a light quantity detection current to a light quantity detection voltage. CONSTITUTION:When a user operates an operator for recording or reproducing after TOC data is read in from a reproduced signal processing circuit 24, a system control circuit 36 switches the operation mode of the whole of a device to the recording or reproducing mode. Simultaneously, the circuit 36 outputs control data to a D/A conversion circuit 4, and the circuit 4 generates a control voltage V3 to set the quantity of light of a light beam L1 to a recommended value. The circuit 36 outputs control data to a selecting circuit 32 to connect a half-fixed resistance 34 to a photo diode 8 in the case of the reproducing mode but to connect a half-fixed resistance 10 and a thermistor 12 to the diode 8 in the case of the recording mode. Thus, this current/voltage conversion characteristic is switched between the recording mode and the reproducing mode when the output current of the diode 8 is converted to a detection voltage V4. |
