| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized, high-performance catadioptric lens, specially, using a diffraction optical element, and which is suitable to an image pickup lens for a small-sized imaging device for a digital camera etc. SOLUTION: As for the catadioptric lens L11 equipped wih the diffraction optical element, the lens L11 is provided with at least an annular incident surface S on which light is made incident, an annular primary mirror R11 whose concave faces the light transmitted through the incident surface S, and a secondary mirror R12 whose convex faces the light reflected by the primary mirror R11, arranged in this order in the light advancing direction. A gap between the primary mirror R11 and the secondary mirror R12 is filled with glass, and any optical surface other than the primary mirror R11 is provided with a diffraction optical surface Gf. Provided that the effective diameter (diameter) of the diffraction optical surface Gf is expressed byΦc and the effective diameter (diameter) of the primary mirror R11 is expressed byΦM, the lens is constituted so as to satisfy the conditional inequality 0.1<Φc/ΦM<1.0. COPYRIGHT: (C)2004,JPO&NCIPI
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