| 摘要 |
PURPOSE:To perform good light recording, by detecting respective laser beam in time series with the photodetector for synchronous detection and by performing an optimum feedback control for each laser element. CONSTITUTION:Photodetector 11 having a photodetection area to which laser beam emitted from semiconductor laser elements LD1-LD3 can be incident simultaneously is used, and laser beam emitted successively from elements LD1-LD3 at fixed intervals is detected in time series. Detected outputs are amplified in 13, and respective voltage values are sample-held in 141-143, and outputs are compared with reference values of comparators 151-153, and difference voltages are sent to laser driving circuits 171-173 through LPFs 161-163. Circuits 171-173 adjust driving currents supplied to elements LD1-LD3 so that outputs of comparator 151-153 become zero, thereby performing good light recording without uneveness of exposure. |
