| 摘要 |
PURPOSE:To obtain easily a scanning light spot in the optimum state by selecting a timing pulse from many timing pulses generated from a grating sensor to control an optical path switching means and allowing the light spot to appear only in the position of a surface to be scanned and observing directly visually it with an optical device. CONSTITUTION:A counting circuit 18 counts pulses corresponding to scanning of a control beam L2 and sends data to comparators 19 arranged in parallel. Consequently, the comparator 191 outputs the output when a recording beam L1 reaches a position P1, and the comparator 192 outputs the output when the beam L1 reaches the position P2, and the comparator 193 outputs the output when the beam L1 reaches the position P3, and these outputs are inputted to a control circuit 22 of an optical modulator 5. The control circuit 22 controls the optical modulator 5 so that the recording beam L1 passes the optical modulator 5 only when the signal is inputted but the beam L1 is intercepted otherwise. The recording beam L1 reaches only three positions P1-P3 on the surface of a driving roll 11, and light spots appear continuously in the still state visually, and these light spots are observed visually with a microscope.
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