Patent ID: 6833968
Filing Date: 2004-12-21
Classification: G02B

Abstract:
An image pickup lens, having an aperture diaphragm S1; a first lens L1, having a meniscus shape with concave surface on the object side, and having positive refractive power; a second diaphragm S2; and a second lens L2, having a meniscus shape with concave surface on the image side, and having negative refractive power; and configured by arranging in order, from the object side, the aperture diaphragm S1, the first lens L1, the second diaphragm S2, and the second lens L2; and wherein at least one surface of said first lens L1 is aspherical, and at least one surface of said second lens L2 is aspherical, overall at least two lens surfaces are aspherical, and the following conditions are satisfied:0.091/f2|<0.37â€ƒâ€ƒ(1) 1.331/f|<47.77â€ƒâ€ƒ(2) 3.081/r2|<113.12â€ƒâ€ƒ(3) 0.63<0.87â€ƒâ€ƒ(4) where f is the focal length of the entire system (the combined focal length of the lens system comprising the first and second lenses); f1 is the focal length of the first lens; f2 is the focal length of the second lens; D is the distance from the aperture diaphragm plane to the second surface (image-side surface) of the second lens (lens center length); r1 is the radius of curvature of the object-side surface of the first lens L1 in the vicinity of the optical axis (axial radius of curvature); and r2 is the radius of curvature of the image-side surface of the first lens L1 in the vicinity of the optical axis (axial radius of curvature).