| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging lens in which aberration is satisfactorily corrected, optical path length is short and moreover full back focus is secured. SOLUTION: The imaging lens is constituted by arranging a first lens L1, an aperture stop S1, a second lens L2 and a third lens L3, in this order, from an object side to an image side, and the first lens L1 is a meniscus lens turning its convex surface toward the object side and having positive refractive power, the second lens L2 is a meniscus lens turning its convex surface toward the image side and having negative refractive power, and the third lens L3 is a lens turning its convex surface toward the object side. Then the imaging lens satisfies following conditions. (1) 0.35<r<SB>1</SB>/r<SB>2</SB><0.45, (2) 0.07<D<SB>2</SB>/f<0.1, (3) 0.01<D<SB>4</SB>/f<0.04, (4) 1.00<d/f<1.30 and (5) 0.3<b<SB>f</SB>/f<0.5. If f: the composite focal distance of the imaging lens, r<SB>1</SB>: the radius of curvature (radius of curvature on the axis) near the optical axis on the object side surface of the first lens L1, r<SB>2</SB>: the radius of curvature (radius of curvature on the axis) near the optical axis on the image side surface of the first lens L1, D<SB>2</SB>: spacing between the first lens L1 and the second lens L2, D<SB>4</SB>: spacing between the second lens L2 and the third lens L3, d: the distance (in air) to an image surface from the object side surface of the first lens L1, and b<SB>f</SB>: the distance (in air) to the image surface from the image side surface of the third lens L3. COPYRIGHT: (C)2006,JPO&NCIPI
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