| 摘要 |
PROBLEM TO BE SOLVED: To reduce the overall size of the apparatus and to make uniform the light spot diameter in a subscanning direction inside an effective scan region, as well as to ensure high-speed production of high-quality pictures. SOLUTION: The optical scanner includes a light source means, a condensing optical system, a deflection means and an imaging optical system having one or more optical elements, wherein, in at least one optical element A of the optical elements, the curvature of the opposite surfaces thereof changes continuously, inside an effective region, from the optical axis toward the peripheral portion thereof so that the sign of the curvature is reversed at the middle, and wherein, when the curvature radius of the surface of that optical element facing the deflection means at the optical axis and in the subscanning sectional plane is denoted by r10, while the least quantity of an absolute value of the curvature radius of the surface facing the scan surface side in an effective region of the portion where the sign of the curvature radius is reversed is denoted by ¾r 2¾<SB>min</SB>, the optical element satisfies respective specific relations for them. COPYRIGHT: (C)2007,JPO&INPIT
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