| 摘要 |
PURPOSE:To attain a superwide angle lens where the field angle is about 100 deg. and various aberrations are compensated well, by satisfying prescribed conditions in the lens system consisting of a concave meniscus lens, a convex lens, a concave meniscus lens, a convex lens, a compound convex lens, and a convex lens which are arranged in order from the object side. CONSTITUTION:Conditions (A)-(D) are satisfied in the lens system consisting of 7 lenses divided to 6 groups, namely, the concave meniscus lens, the convex lens, the concave meniscus lens, the convex lens, the compound convex lens consisting of a concave lens and a convex lens, and the convex lens which are arranged in order from the object side. In expressions (A)-(D), (f), f1, f2, n1, and nu2 are the focal length of the whole of the system, the focal length of the first lens, the focal length of the second lens, the refractive index of the first lens, and the Abbe's number of the second lens respectively. The increment of the front lens diameter is prevented by the condition (A), and the distortion, the curvature of field, and the chromatic aberration of magnification are compensated well by the condition (B). The coma, the curvature of field, and the chromatic aberration of magnification are compensated by conditions (C) and (A), and the chromatic aberration is compensated by the condition (D), and thus, a superwide angle lens where the field angle is about 100 deg. is attained. |
