Photographic objective of reduced size

Claim 1

A photographic objective of reduced size including the following various conditions: from front to rear; a first lens in the form of a positive meniscus lens convex toward the front; a second lens in the form of a negative lens; a third lens in the form of a positive lens; a fourth lens with the front surface concave toward the front, said concave surface being aspheric and said aspheric surface being figured by the following equation: ##EQU2## where the axial direction is taken as the X-axis, the direction perpendicular to the optical axis as the Y-axis, the direction in which light advances as positive, and the intersection of the vertex and the X-axis at the original point, and the difference along the X-axis direction between the aspheric surface and the surface obtained by extrapolating the spherical surface contributing to the determination of the focal length is denoted by ΔX, the radius of curvature of the paraxial region by R, the radius of curvature of the standard spherical surface of the lens defined as R*=R/(1-2RA 1 ), the aspheric even coefficients by Ai and the aspheric odd coefficients by Bi; and being characterized by the following numerical values for the radii of curvature of the lens surface Ri numbered the i-th from the front, the lens thicknesses and axial air separations Di, the refractive indices for spectral d lines of the glasses of the lens elements Ni, and Abbe numbers νi of the glasses of the lens elements as related to a focal length of the entire lens system f=100: ______________________________________ F = 100 F-number = 1:3.5 Image Angle 2ω = 63° Radius of Thickness & Refractive Abbe Curvature Separation Index (Nd) Number (νd) ______________________________________ R1 = 28.32 D1 = 8.59 N1 = 1.77250 ν1 = 49.6 R2 = 86.00 D2 = 2.66 R3 = -159.52 D3 = 2.86 N2 = 1.80518 ν2 = 25.4 R4 = 43.65 D4 = 5.33 R5 = 69.12 D5 = 5.44 N3 = 1.60342 ν3 = 38.0 R6 = -69.12 D6 = 20.51 R7 = -16.56 D7 = 4.58 N4 = 1.49171 ν4 = 57.4 R8 = -22.20 ______________________________________ ______________________________________ Aspherical Coefficients (the Aspheric surface at R7) ______________________________________ A1 = -0.17023 × 10.sup.-2 B1 = -0.54318 × 10.sup.-4 A2 = 0.65538 × 10.sup.-5 B2 = 0.73458 × 10.sup.-7 A3 = -0.74579 × 10.sup.-7 B3 = 0.15509 × 10.sup.-8 A4 = 0.28740 × 10.sup.-9 B4 = -0.13024 × 10.sup.-10 A5 = 0.11786 × 10.sup.-12 ______________________________________