| 摘要 |
PURPOSE:To reproduce an image with resulting high resolution and high accuracy even when an error exists in the focal distance of an image forming lens, by correcting the error in the focal distance of the image forming lens by adjusting the rotating speed of a rotary polygon mirror and a photosensitive drum. CONSTITUTION:The frequency demultiplication factor of a variable frequency demultiplier is adjusted corresponding to the error in the focal distance (f) of an Ftheta lens. In other words, the angular velocity omegas=fs/ns of the polygon mirror and the angular velocity m=fs/KDnd are adjusted by the frequency demultiplication factor. Therefore, even when the error exists in the focal distance (f) of the Ftheta lens 5, it is possible to image form the image with resulting the high resolution and high accuracy on the photosensitive drum by adjusting the angular velocity of the polygon mirror 3 and the photosensitive drum 6 by adjusting the frequency demultiplication factor of a variable frequency oscillator 18.
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