| 摘要 |
PURPOSE:To keep the peak value and the bottom value of an optical output waveform at constant values, by controlling the peak value of an output waveform pulse-modulated at the time of recording invariably, and also controlling the bottom value based on a controlled error signal. CONSTITUTION:A photodetector 2 receives a pulse-modulated optical output wave from a semiconductor laser 1, and an operational amplifier 3 converts a received output to a voltage, and a peak holding circuit 10 holds its peak value. The signal waveform is compared and outputted with a reference voltage 7 at the time of recording by an operational amplifier 4, and a current which flows on the laser 1 is controlled by a transistor Tr15, then, the peak value is kept constant. Also, the controlled output waveform of the amplifier 4 is divided by a variable resistor 13, and the current is set at the one on the laser 1 equivalent to the bottom value. A voltage (e) divided and outputted by the resistor 13 is applied on a Tr14, and the Tr14 is connected in parallel with a Tr16. Therefore, a current value (f) which controls the bottom value of the optical output waveform is added on a current value (h), then, the peak value and the bottom value of the laser 1 can be controlled invariably.
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