| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging optical system which is designed in a small size with low manufacture cost, aberrations, such as chromatic aberrations being corrected appropriately. SOLUTION: The imaging optical system has a first lens having positive power, a second lens having positive power, and a third lens having negative power with an aspherical surface on an image surface side, the aspherical surface, that is shaped in a concave shape, facing toward the image surface side in a vicinity of an optical axis and shaped into a convex shape, facing toward the image surface side in a surrounding of the optical axis on the image surface side in order from an imaging object side. The imaging optical system is designed to satisfy the relation;ν3-ν2>10, whereν3 denotes an Abbe number of the third lens andν2 denotes the Abbe number of the second lens. COPYRIGHT: (C)2007,JPO&INPIT
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