| 摘要 |
PURPOSE:To obtain a sufficient gain with any output light intensity and to control the intensity of laser beam stably by compensating output characteristics of an electrooptic modulator which varies in output light intensity with an impressed voltage artificially into linear characteristics. CONSTITUTION:The projection light R0 of a laser beam source 1 is converted into beam R1 with specific beam intensity by the electrooptic modulator 2 and the beam is inputted to an adder 6 through a photodetector 5, so that the voltage obtained by subtracting a detection output voltage from a reference signal voltage by the adder 6 is inputted to an attenuator 8 through a filter 7. The correcting signal of a microprocessor 10 to which the reference signal voltage is inputted is supplied to the attenuator 8 and the output voltage of the filter 7 is attenuated at an attenuation ratio corresponding to the reference voltage and supplied to an EOM 2 to compensate the output characteristics of the EOM 2 artificially into linear characteristics. Compensating circuits 8-9 for the compensation are provided in a feedback loop 11. Therefore, noise components are removed uniformly without reference to the output beam intensity and laser beam R1 with a stable prescribed level determined by the reference voltage is obtained. |
