| 摘要 |
PURPOSE:To correct a face deflection error of a rotary polygon mirror by detecting a scanning line position by two photodetectors arranged at a prescribed interval in a direction perpendicular to a deflection face so as to drive a face deflection correcting moving mirror based on the detection. CONSTITUTION:A divergent luminous flux from a laser diode 2 is formed into a converged flux by an image forming lens l and scanned by a polygon mirror 3 driven in the direction of arrow A. The luminous flux is made incident in photodetectors ll,12 via a reflection mirror 9 before the scanning reaches the recording state onto a photosensitive drum 5 and currents i1, i2 proportional to the received luminous amount are outputted. A controller 10 sends the recording information to the diode 2 as on/off information at a prescribed time elapsed after a signal of the current i1+i2 is received. The controller 10 applies a voltage V proportional to a current i1-i2 to a driver 8 of a moving mirror 7, the driver 8 drives the moving mirror 7 by a quantity proprotional to the voltage V so as to apply face deflection correction of the polygon mirror 3.
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