| 摘要 |
PURPOSE:To eliminate the influence of returning light quantity for a high output laser diode, to automatically perform constant optical output drive with a specified optical output, and to prevent a current injected to the laser diode from increasing and its quality from deteriorating by switching over between a photoelectric converter and a monitoring photodiode. CONSTITUTION:As a laser diode injecting current (b) supplied from a controller 10 to a laser diode 1 is increased proportionally to a time, an output voltage (c) from a photoelectric converter 4 and a photoelectric conversion voltage (e) from a monitoring photodiode 3 are similarly increased. The voltage (c) is inputted to the controller 10, compared with a reference voltage A (first reference voltage), the increase of the laser diode injecting current is stopped when the output voltage of the converter 4 coincides with the voltage A to hold its current value as it is. Then, a nonreflecting shutter 6 is closed by a signal (d), the monitoring photoelectric conversion voltage (e) obtained in this state is used as a reference voltage B (second reference voltage), and the laser diode injecting current (b) is so controlled that the monitoring output always becomes equal to the voltage B. |
