| 摘要 |
PURPOSE:To obtain a high-capacity lens which is bright and has less aberration variance due to feeding of a front group and has less various aberrations, especially, distortion by using meniscus lenses whose surfaces of higher curvature face each other as two negative lenses of a rear group. CONSTITUTION:This lens system is constituted of the front group of triplet and the rear group of two negative lenses, namely, 5 lenses in total. Two negative lenses of the rear group are meniscus lenses whose surfaces of higher curvature face each other. Conditions 0<f1.2, 0.7<¦fR¦/f<1.35<nu3<50, and -8<r8/r9<-4 are satisfied where (f) is the focal length of the whole of the system and f1.2 is the resultant focal length of the first and the second lenses in the object side and fR is the focal length of the rear group and ri is the radius of curvature of the i-th surface in the object side and nui is the Abbe's number of the i-th lens in the object side.
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