| 摘要 |
PROBLEM TO BE SOLVED: To sufficiently assure luminous flux separation in a sub-scanning direction on an imaging optical element surface, and to suppress the height of an apparatus in the sub-scanning direction. SOLUTION: An optical scanner has: a light source means; a deflection means; an incident optical system; and an imaging optical system equipped with at least one sheet of a transmission type imaging optical element and at least one sheet of a reflection type optical element. In the imaging optical element, a luminous flux subjected to deflection scanning by the deflection means successively passes through a first transmission surface and a second transmission surface of the imaging optical element, is reflected by a reflection surface of the reflection type optical element, and then successively passes through a third transmission surface and a fourth transmission surface of the imaging optical element again. The first transmission surface and the fourth transmission surface of the imaging optical element are constituted of surfaces at least having different shapes in the sub-scanning direction. The luminous flux subjected to deflection scanning by the deflection means in a sub-scanning cross section is refracted or diffracted at the first transmission surface in a direction where the luminous flux reflected by the reflection type optical element passes through the third transmission surface. COPYRIGHT: (C)2011,JPO&INPIT
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