| 摘要 |
PROBLEM TO BE SOLVED: To correct an image height error defect caused by the production error of a lens by providing an Fθlens consisting of a lens having negative refractive power and a lens having positive refractive power, rotating the lens having the positive refractive power on a scanning plane centered on an axis perendicular to an optical scanning surface and fixing it at an optional position after adjustment. SOLUTION: The light from a light source 1 is made into parallel beams by a collimator lens 2, passes through a cylinder lens 3 for correcting plane tilt and is deflected by a rotary polygon mirror 11 so as to perform scanning. Then, it is converged on a photoreceptor 8 by the Fθlens consisting of the lens 5 having the negative refractive power and the lens 6 having the positive refractive power. The lens 6 put on a lens adjusting device consisting of a rotatable base 9 is rotated and adjusted to the optional position on the scanning plane by a gear 10 rotated by a motor 11. Therefore, even when distortion is caused on printing due to the production error or arrangement error of the lens 6, the image height error is appropriately corrected by rotating, adjusting and fixing the base 9 while observing the printed result.
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