| 摘要 |
PURPOSE:To obtain a photographic lens which has excellently compensated chromatic aberration by providing the 1st - the 4th positive, negative, negative, and positive lenses successively from an object side, and allowing the optical system composed of the 3rd and the 4th cemented lenses to meet specific requirements. CONSTITUTION:The 1st lens has the convex surface on the object side and positive refracting power and the 2nd lens is a biconcave lens; and the 3rd lens is a meniscus lens which has the convex surface on the object side and negative refracting power, and the 4th lens is a biconvex lens. The 3rd and the 4th lens are cemented together. This lens system meets the various requirements shown by inequalities I -IX. In the inequalities, Ri is the radius of paraxial curvature of the (i)th lens surface counted from the object side and Di is the lens thickness or air gap of the (i)th lens counted from the object side; and Ni and nui are the refractive index and Abbe number of the (i)th lens and (f) is the focal length of the whole system. |
