| 摘要 |
PROBLEM TO BE SOLVED: To obtain a fish-eye lens system showing excellent resolution from an on-axis state to an off-axis state as a fish-eye lens system constituted of a front group having a negative focal distance, a diaphragm and a rear group having a positive focal distance in order from an object side, and having a half viewing angle of 90°. SOLUTION: In the fish-eye lens system, the front group has at least 1st, 2nd and 3rd negative meniscus lenses turning their convex surfaces to the object side in order from the object side, and satisfies conditional expressions (1) to (3). (1) 0.2<SF1<0.6 (2) 0.8<SF2/SF1<1.4 (3) 0.8<SF3/SF1<2.0, provided that SFi=the shaping factor of the i-th negative meniscus lens, SFi=(R1i-R2i)/(R1i+R2i), R1i: the radius of curvature of the object-side surface of the i-th lens, and R2i: the radius of curvature of the image-side surface of the i-th lens. COPYRIGHT: (C)2006,JPO&NCIPI
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