| 摘要 |
PROBLEM TO BE SOLVED: To satisfy high performance and miniaturization simultaneously in an image forming optical system used in combination with a solid-state image pickup element or the like and utilized for a compact camera or a monitor camera or the like. SOLUTION: In the image forming optical system, a 1st positive meniscus lens turning its convex surface toward an object side, a brightness diaphragm, a 2nd negative meniscus lens turning its convex surface toward an image side and a 3rd positive lens are arranged from the object side, and the surface of the 3rd positive lens on the object side is an aspherical surface whose curvature gets smaller toward the periphery and the surface thereof on the image side is an aspherical surface whose curvature gets larger toward the periphery. Thus, the deterioration of performance caused by manufacture errors is reduced and high performance is kept even when miniaturization is realized. COPYRIGHT: (C)2005,JPO&NCIPI
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