| 摘要 |
PURPOSE:To obtain a lens system which has aberrations compensated well and is easy to produce, by satisfying prescribed conditions in the lens system consisting of three lenses of two groups where the first lens group and the second lens group are arranged in order from the incidence side. CONSTITUTION:The first lens group I and the second lens group II arranged in order from the incidence side of a luminous flux constitute the lens system. The first lens group I consists of a cemented lens of the first positive lens L1 and the second negative lens L2, and the second lens group II consists of a positive meniscus lens L3 whose convex is directed to the incidence side of the luminous flux, and this lens system consists of three lenses of two groups. This lens system is constituted to satisfy conditions of formulas I and II where (f) is the focal length of the whole of the system and r2 and r5 are the radius of curvature of the cemented surface of the first lens group I and that of the condensing-side surface of the third lens L3 and n1, n2, and n3 are radiuses of curvature of the first lens L1, the second lens L2, and the third lens L3 respec tively.
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