| 摘要 |
PURPOSE:To take a high-accuracy measurement by converting part of a laser beam photoelectrically by a monitoring photodetecting element and shaping the waveform of the output of a measuring photodetecting element with a reference signal generated by processing said photoelectrically converted signal. CONSTITUTION:Part of the laser beam 12 from a beam generator 10 is converted into a parallel scanning beam 20 through a half-mirror 15, a polygon mirror 16, etc. The remaining part of the beam 12, on the other hand, is transmitted through the half-mirror 15, converted photoelectrically by the monitoring photodetecting element 27, and inputted to a microprocessor 48 through an A/D converter 70a. Further, the light and shade of the beam 20 is detected as the output variation of the measuring photodetecting element 26 and the maximum value of an output A is inputted to the processor 48 by the operation of a diode 77 through an amplifier 28a. Then, a gain adjustment is made at the stage of adjustment so that the maximum value of the output of the amplifier 20a is equal to the output of the amplifier 28d and when a measurement is taken, the output of the converter 70a is inputted to the processor 48, the value is set in an A/D converter 72 to generate a reference signal B, and the waveform of the output A is shaped.
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