| 摘要 |
PROBLEM TO BE SOLVED: To improve the uniformity of a light quantity of a light beam at a surface to be scanned and to improve the uniformity of a beam diameter. SOLUTION: A grating element 24 of a transmission type is arranged between a semiconductor laser 12 and a polygon mirror 18 so that the diffraction angle of the diffracted light of the order made incident on the polygon mirror 18 is made smaller than the incident angle of the light beam on the grating element 24. As a result, the segment of the high light quantity distribution on a photoreceptor 20 may be corrected by expanding the beam diameter and changing the diffraction efficiency with respect to the optical axis, by which the uniformity of the light quantity of the light beam may be attained.
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