| 摘要 |
PURPOSE:To obtain a titled lens which has a 58-62 deg. view angle, the 1.8-2.0 maximum aperture ratio, and also is corrected each aberration satisfactorily, by constituting said lens so that a lens system constituted of 6 pieces consisting of the first and the second group lenses, an aperture, and the third and the fourth group lenses satisfies prescribed various conditions. CONSTITUTION:A titled lens consists of the first group L1 of a positive meniscus lens whose convex surface is directed to an object field side, the second group L2 of a negative meniscus lens whose convex surface is directed to the object field side, consisting of a positive meniscus lens and a negative meniscus lens cemented to said lens, an aperture, the third group L3 of a negative meniscus lens whose convex surface is directed to the object field side, consisting of a biconcave lens and a biconvex lens cemented to said lens, and the fourth group L4 of a biconvex lens, in order from the object field side. Various conditions of inequalitiesI-VIII are satisfied, and in the inequalities, (r), (d), (n), (nu), a subscript, and (f) denote a radius of curvature of each lens surface, the center thickness of a lens and a lens interval, a refractive index of glass to be used, Abbe number, sequence from an object side, and a composite focal distance of the first group L1 and the second group L2, respectively. |
