| 摘要 |
PURPOSE:To accurately detect a recording data even when a light output is varied due to internal and external dominant causes by providing an output control circuit capable of outputting a semiconductor laser in attenuating its variable frequency component and making no response to its data frequency component. CONSTITUTION:The subject device is composed of an output setting circuit SC and a semiconductor laser output control circuit (APC circuit) formed with a control loop (AC, LF, GC and IV), and a semiconductor laser LD and a photo detector PD are connected into the APC circuit. The laser LD is driven in response to a setting output from the circuit SC, and a variation of the laser output to be in response to return light via a recording surface is detected by the detector PD. The APC circuit is operated in such a manner that the variable frequency component S1 out of frequency components of a light output to be given to the detector PD from the laser LD is largely attenuated to be outputted, and the data frequency component S2 is outputted as it is. By this constitution, the component S2 is never amplitude-modulated by the component S1, and the recording data accurately is reproduced based on a detecting output of the detector. |
