| 摘要 |
PURPOSE:To enable a constant peak output of a semiconductor laser to be maintained without depending on the duty ratio of a modulated input signal, by changing an average light output command of the semiconductor laser according to the duty ratio of the modulated input signal. CONSTITUTION:A photoelectric current, which varies directly with the light output of a semiconductor laser 5, flows through a photodiode 6 composing a means A for detecting light output to be converted into a voltage by a resistor 7. The laser 5 is drived by pulses produced through a modulated signal to vary a monitoring signal for the light output. This monitoring signal is smoothed and is converted the level thereof to be output as an average light output monitoring value by the means A. On the other hand, the modulated signal is supplied to a means B for outputting average light output command through an inverter 15 to become an average light output command at a variable resistor 23. An amplifier 12 amplifies the difference between the average light output command and the average light output monitoring value to drive a transistor 2. Therefore, the light output of the laser 5 is so controlled as to correspond to the average light output command, and the peak output thereof is so controlled as to be constant without depending on the duty ratio of the modulated signal. |
