| 摘要 |
A light scanning unit includes a light source which emits light beam with a predetermined wavelength, a beam deflector which deflects and scans the light beam emitted by the light source toward a photosensitive body, and an f-theta lens which has at least one plastic lens and forms an image for the light deflected by the beam deflector on the photosensitive body, the light scanning unit satisfying a following formula 0<Lmax-Lmin<=[20x(cos theta)5+10]xlambda/(5x10-4) where Lmax and Lmin respectively represent a maximum value and a minimum value of a total light passing distance from a light axis of at least one plastic lens according to a deflection angle, theta is an angle formed between a polarization direction of the light beam emitted by the light source and a sub-scanning direction, and lambda is a wavelength of the light beam emitted by the light source.
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