| 摘要 |
PURPOSE:To reduce the number of photodetecting elements, to facilitate adjustment and to reduce cost by projecting light for detecting sycnrhonzing signal to an intermittent grating slit and intermittently obtained reference pulses for phase lock from a one-line scanning region by the exit light therefrom. CONSTITUTION:A grating 33 is provided intermittently with slit arrays 34a-34c arranged with many slits. A laser beam for detecting the synchronizing signal from an ftheta lens scans the grating 33 having light shieldability and passes the slit arrays 34a-34c. Lenses 35a-35c and the photodetecting elements 36a-36b are disposed behind the slit arrays 34a-34c so as to correspond thereto. The beams past the respective arrays 34a-34c are condensed respectively by the lenses 35a-35c to the elements 36a-36c by which the beams are photoelectrically converted. The output signal fro the elements 36a-36b are added 37 and are waveform-rectified by a a waveform rectifier 38 to form the intermittent reference pulses P1 for phase lock. A PLL (Phase Locked Loop) circuit 39 generates picture element clocks Po by the reference pulses P1 transmits the same to a character generator. The number of the lenses and photodetecting elements is thereby reduced and the adjustment is facilitated.
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