| 摘要 |
PURPOSE:To stably and safely execute control with simple constitution even when there is a returning light by detecting optical power, which is outgoing forward from a semiconductor laser, controlling the power to be constant, detecting optical power, which is outgoing backward, and detecting abnormal light emission. CONSTITUTION:For a light to be outgoing forward from a semiconductor laser 21, one part of the light is reflected by a half mirror prism 23 and a magnetic disk 25 is irradiated by the reflected light and the other part of the light is incoming to a forward outgoing light detector 26. Then, the power is detected. Next, the output of the detector 26 is compared with a control voltage Vref1 of a power source 29 by a control circuit 29 and the power of the semiconductor laser 21 is controlled to a target value through a power amplifier 30. The power is detected by a backward outgoing light detector 31 of a monitor photo-diode in the case of the semiconductor laser 21 and compared with a reference voltage Vref2 of a power source 34. When the power exceeds the reference voltage, the driving current of the semiconductor laser 21 is controlled to the zero by the control circuit 28. Thus, the control can be stably and safely executed with the simple constitution even when there is the returning light. |
