| 摘要 |
PURPOSE:To reduce a laser noise. CONSTITUTION:A signal is recorded and reproduced by irradiating a magnetooptic disk 18 with the light emitted by a laser diode LD through a separation optical system 20. A layer photodiode PD 4 which detects the quantity of the light emitted by the laser diode is provided and its photodetection output is negatively fed back to a laser driving amplifier 56 through a wide-band current-voltage amplifier 60 to reduce a diode noise due to return light from the disk. A high frequency signal generating circuit 58 is provided and its high frequency signal is supplied to a laser driving amplifier 56 to drive the laser diode LD with the high frequency signal. The quantity of the light emitted by the laser diode which is varied with the return light is detected and the detection output is negatively fed back to the laser driving amplifier 56, so the quantity of the emitted light is stabilized, and consequently the laser noise is reducible. When a high frequency signal is superposed, the reduction effect is increased more. |
