| 摘要 |
PURPOSE:To obtain a photographic lens which has less aberration due to eccentricity, by employing the four-group constitution of a positive, biconcave, biconvex, and a negative meniscus lens viewing from an object side in order, and allowing the lens to meet specific requirements. CONSTITUTION:This photographic lens consists of four groups, i.e. the 1st positive lens L1 having a large-curvature surface on the object side, the 2nd biconcave lens L2, the 3rd biconvex lens L3, and the 4th negative meniscus lens L4 having a convex surface on the image side successively from the object side. This lens meets the specific requirements as shown by inequalities I -III, where r7 and r8 are the radiuses of curvature of the 4th lens L4 on the object and image sides respectively, and d5 is the on-axis core thickness of the 3rd lens; and r2 is the radius of curvature of the 1st lens L1 on the image side, r3 is the radius of curvature of the 2nd lens L2 on the object side, and (f) is the total focal length of this system. |
