| 摘要 |
PROBLEM TO BE SOLVED: To provide a small imaging lens used in imaging equipment for a portable phone, a personal digital assistant and an electronic still camera or the like, which gives priority to the miniaturization of configuration firstly, which has excellent imaging performance and distortion aberration characteristic, sufficient peripheral light quantity and appropriate back focus, and which realizes the miniaturization while securing the position of an exit pupil as long as possible. SOLUTION: The small imaging lens is constituted of an aperture diaphragm and a 1st positive lens succeeding it, a 2nd negative lens and a 3rd positive or negative lens in order from an object side, and the respective lenses have at least one or more aspherical surfaces. The imaging lens satisfies following conditional expressions. (1) 0.9<f/f1<1.3, (2) 1.0<TL/f<1.6, (3) 0.25<fB/f<0.65 and(4) 45<ν1, provided that f: the focal distance of an entire lens system, f1: the focal distance of the 1st lens, TL: length from the first surface of the lens to an imaging surface (parallel plane part is converted to air length) fB: length from the final surface of the lens to the imaging surface (parallel plane part is converted to air length), andν1: the Abbe number of the material of the 1st lens. COPYRIGHT: (C)2005,JPO&NCIPI
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