| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive optical scanner which has a function of detecting the subscanning position of a light beam without causing large size of a scanning optical system. SOLUTION: The optical scanner according to the present invention is provided with: a diffraction optical element 2283 which is arranged in an optical path through which a light beam deflected with a deflection means passes, and diffracts and splits the light beam into a plurality of beams to form a desired pattern of a diffracted image; and a photodetector 2284 which detects a part of the diffracted image in a subscanning direction, wherein the optical scanning is carried out with the deflection means and also the photodetector is scanned by the diffracted image, the diffracted image is set in a pattern that the signal of the diffracted image is detected with the photodetector 2284 at least twice by one optical scanning, and the time interval between the signals detected with the photodetector at least twice by one optical scanning of the diffracted image varies according to the relative positions of the photo detector and the diffracted image in the subscanning direction. COPYRIGHT: (C)2008,JPO&INPIT
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