| 摘要 |
PURPOSE:To control the output of plural semiconductor lasers at prescribed reference values respectively, by detecting laser beams emitted to the rear sides of three semiconductor lasers for erasure, recording, and reproduction by one optical detector, amplifying them, and comparing them with reference voltages. CONSTITUTION:The laser beams emitted to the rear sides of the semiconductor lasers 17, 18, and 19 for erasure, recording, and reproduction are detected by the optical detector 20 consisting of one photodiode, and are amplified by an amplifier 21. The output of the amplifier 21 are compared with the reference voltages Vref1, Vref2, and Vref3, respectively, and their error output are sample- held at sample/hold circuits 28, 29 and 30 by timing signals T1, T2, and T3 via low-pass filters 25, 26, and 27, respectively. Semiconductor laser driving circuits 32, 33, and 34 control optical output by controlling the driving currents of the semiconductor lasers 17, 18, and 19 by the output signals of the sample/ hold circuits 28, 29, and 30. |
