| 摘要 |
PURPOSE:To achieve an accurate recording and reproducing function, by locking the output level of a semiconductor laser at a previously set prescribed level at the time of power on and/or standby mode of an information recording and reproducing device and controlling the optical output of the laser at the time of recording and/or reproducing by using the locked level. CONSTITUTION:The level of an optical output from a semiconductor laser 21 is detected by a photodetector 22 and its detected signal is supplied to a comparator 24-2 through an amplifier 23. The detected signal is compared with a previously set reference voltage VR2 at the comparator 24-2. When the signal inputted into the comparator 24-2 exceeds the reference voltage VR2, the comparator 24-2 outputs an inverse signal and a counter 25-2 is set to the counted value at the moment by the inverse signal and, therefore, the optical output level of the semiconductor laser 21 at the high condition of a record signal (a) is set to a prescribed level. By using the output level of the semiconductor laser maintained under such a condition, recording and reproduction of information are performed. |
