| 摘要 |
PURPOSE:To perform stable monitoring in the stage of reading out and writing by providing an amplifier which takes out a DC component from a sensor for monitoring the output of a laser diode and a substractor which takes out a high- frequency component thereof and adds said output and the detection output for the envelope of the negative side component to a reversed polarity. CONSTITUTION:The high-frequency component is taken out of the output obtd. from the photodiode 1 which monitors the output of the laser diode by the AC amplifier 2. A half-wave rectifier 3 takes out only the part of the negative polarity from the output of the amplifier 2 and supplies the same to an envelope detector 4. The output of the detector 4 and the output of the amplifier 2 are added to the reversed polarity by the subtractor 5. The power monitor signal in the stage of reading out is thus taken out by the operational amplifier 6 without drift and the stable monitor signal having the extremely small waving and drift is taken out by the subtractor 5 for the monitor signal in the stage of writing for which high-speed response is requested. |
