| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom optical system by which a high-quality image is obtained while making the best use of the characteristic of a non-axis optical system and also keeping the center position of an image surface nearly constant during zooming. SOLUTION: An imaging optical system ZL has a plurality of optical surfaces and a diaphragm ST, and has eccentric reflection surfaces S10 and S13 as at least one surface of the plurality of optical surfaces. Second and third prisms P2 and P3 have the eccentric reflection surfaces S10 and S13, and perform the parallel movement and the rotational movement as the moving groups (second group Gr2 and third group Gr3) having positive power or negative power, whereby the focal length of the entire system is changed while keeping an image forming position on an axis and an incident angle of an axial principal ray on the image surface S15 nearly constant. COPYRIGHT: (C)2008,JPO&INPIT
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