A high-aperture wide-angle lens assembly, comprising:
- a divergent front lens group consisting of at least one lens with considerable effect on distortion correction and relative luminous intensity having a negative refraction decreasing continuously from an optical axis of said assembly outwardly to an edge thereof and with an aspherical front surface;
- a relatively large air space following said front lens group and having a thickness of at least three times an overall focal length of the assembly;
- a rear lens group separated by said relatively large air space from said front lens group and consisting of at least three lenses including:
- a first convergent lens group consisting of a cemented element, and
- a second convergent lens group separated by a small air space from said first convergent lens group and having an effect on spherical aberration and image field convexity, said rear lens group having a positive refracting action continuously decreasing from said optical axis outwardly to an edge by reason of at least one aspherical surface of said second convergent lens group facing said cemented element, said cemented element consisting of two lenses;
- and
- an aperture diaphragm with vignetting action located substantially at the center of the thickness of said relatively large air space for image field correction, said divergent front lens group consisting of a single lens having a front surface which is aspherical and of a radius r 1, a thickness along said axis d 1, a refractive index n 1 and an Abbe coefficient v 1, and a rear surface with a radius of curvature r 2, said relatively large air space having a thickness d 2 between said front lens group and said diaphragm and a thickness d 3 from said diaphragm to a front surface of said cemented element, said diaphragm having an effective radius of curvature r 3, said front surface of said cemented element having a radius r 4 of a front lens of said cemented element with a thickness d 4 along said axis, a refractive index n 2 and an Abbe coefficient v 2, a rear surface of said front lens of said cemented element and a front surface of a rear lens thereof having a radius r 4, said rear lens having a thickness along said axis d 5, a refractive index n 3 and an Abbe coefficient v 3, a rear surface of said rear leans of said cemented element having a radius r 6 and being separated by said small air space d 6 from an aspherical front surface of said second convergent lens group having a radius r 7, a thickness d 7, a refractive index n 4, an Abbe coefficient v 4 and a rear surface with a radius r 8, the lens assembly being characterized by the following data .+-.5%:
- ______________________________________ r 1 = 1470.82 (aspherical) d 1 = 1.21 n 1 = 1.7292 v 1 = 54.70 r 2 = 5.902 d 2 = 9.00 r 3 = .infin. d 3 = 6.56 r 4 = 10.15 d 4 = 7.00 n 2 = 1.6405 v 2 = 60.10 r 5 = -6.32 d 5 = 0.86 n 3 = 1.8467 v 3 = 23.83 r 6 = -111.958 d 6 = 0.10 r 7 = 14.87 (aspherical) d 7 = 5.79 n 4 = 1.7725 v 4 = 49.60 r 8 = -8.64 F = 2.997 2w = 122 degrees Aspherical coefficients of the surface of radius r 1 K (cone constant) = 0 D 0.340428 .times. 10.sup.-3 E -0.432607 .times. 10.sup.-5 F 0.576946 .times. 10.sup.-7 G -0.356679 .times. 10.sup.-9 Aspherical coefficients of the surface of radius r 7 K (cone constant) = 0 D -0.852530 .times. 10.sup.-3 E -0.947159 .times. 10.sup.-5 F 0.151413 .times. 10.sup.-6 G -0.139941 .times. 10.sup.-8 and the aspherical surfaces are defined by the equation:
- ##STR3## z = pitch in relation to the axial perpendicular plane y = distance from the optical axis k = cone constant D, E, F, G = aspherical coefficients C = vertex curvature. ______________________________________