| 摘要 |
PROBLEM TO BE SOLVED: To attain a high-performance compact lens system by effectively using aspherical surfaces, even though the lens system is constituted of a small number of lenses. SOLUTION: A 1st positive lens G1 constituted of glass material, a diaphragm St, a 2nd positive lens G2 constituted of a plastic aspherical lens and a 3rd negative lens G3 constituted of a plastic aspherical lens are arranged in this order from an object side, and also, the system satisfies the following conditional inequalities: 0.6<R1/f<0.8 ...(1), -1.0<f3/f<0 ... (2) and 0.60<tanθ<0.70 ...(3), provided that f denotes the paraxial focal distance of the whole lens system, f3 denotes the paraxial focal distance of the 3rd lens G3, R1 denotes the curvature radius of the object side surface of the 1st lens G1 andθdenotes a half viewing angle at the maximum image height. COPYRIGHT: (C)2006,JPO&NCIPI
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