| 摘要 |
PURPOSE:To make it possible to perform high-speed control without offset by performing the control so that the total of the detection currents through shunt circuits, wherein the ratio between the current not for detection and the current for detecting is changed due to the power fluctuation of a light irradiation means, becomes a specified current. CONSTITUTION:When the power of a laser beam rises up, the outputs currents of photodiodes 11 and 12 increase and the output voltage of an adder 31 becomes lower than the voltage Vref of a DC power supply, the currents not for detection flowing through transistors 13A and 14A are increased, and the currents for detection flowing through transistors 13B and 14B are decreased. As a result, the output voltage of the adder 31 is also increased. This state continues until voltage becomes Vref. When the power of the laser beam is decreased and the output voltage of the adder 31 becomes higher than Vref, the currents not for detection through shunt circuits 13 and 14 are decreased, and the currents for detection are increased. The output voltage of the adder 31 is decreased and finally becomes Vref. The control is performed so that the total of the detection currents becomes a specified current. Thus, the light irradiation control system, which can perform the continuous control with a simple constitution, can be obtained. |
