| 摘要 |
PURPOSE:To form a true circle on a CRT display device into complete roundness even on a member to be irradiated by changing independently a speed of beam scanning the member to be irradiated and a frequency of a picture signal so as to change the magnification of the picture. CONSTITUTION:A modulator 11 modulates a laser beam from a laser oscillator 12 by a picture signal and a rotary polygon mirror 13 is driven with a prescribed angular velocity by a motor 14 so as to deflect the laser beam from the modulator 11. When a print data and a control command are transferred from an external device, the control section 17 designates longitudinal magnification and lateral magnification of the picture and gives the print data to a modulator drive circuit 20. A clock signal from the oscillator 21 is frequency-divided by a motor control frequency division circuit 18, fed to a motor drive circuit 22, which drives the motor 14 in a speed proportional to the frequency of an output signal of the circuit 18.
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