| 摘要 |
PROBLEM TO BE SOLVED: To reduce bending of a scanning line and also to lighten the slit latitude by correcting the placing error of a mirror that is set in an optical path and accordingly correcting the Z-component of luminous flux that is made incident on a diffraction optical element to almost 0. SOLUTION: In an image reader, where the image information on an original, etc., is formed into an image on a solid-state image pickup device via an image- forming optical system and then the image information is read, a diffraction optical element is set in an image-forming optical path to perform color separation. A slit is disposed in the optical path to cut the out-of-axis luminous flux of the secondary scanning direction, and the diffraction optical element has a rotation management mechanism, which defines an axis that is parallel to the horizontal scanning direction as its rotating axis. Then the image forming luminous flux that is coming from a lens is made incident vertically on the diffraction optical element.
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