Patent ID: 6600610
Filing Date: 2003-07-29
Classification: G02B

Abstract:
A standard photographic lens comprising, in order from the object side, a front lens group, a diaphragm to regulate the brightness of the image, and a rear lens group, whereinthe front lens group is formed of a first lens element of negative refractive power and meniscus shape, with its convex surface on the object side, and a second lens element of positive refractive power and meniscus shape, with its convex surface on the object side; the rear lens group is formed of a third lens element of negative refractive power with a concave surface on the object side, a fourth lens element of positive refractive power with a convex surface on the image side, and a fifth lens element of meniscus shape with its concave surface on the image side, and the following Conditions (1)-(8) are satisfied: 0.75 < L/f < 1.0Condition (1)2.70 < fF/f < 4.0Condition (2)0.60 < f2/f < 1.0Condition (3)0.33 < f4/f < 0.43Condition (4)0.25 < R2/f < 0.40Condition (5)0.25 < R11/f < 0.45Condition (6)0.02 < D2/f < 0.12Condition (7)&ngr;1  > 50.0â€‰Condition (8)â€ƒwhere L is the back focus, f is the focal length of the standard photographic lens, fF is the focal length of the front lens group, f2 is the focal length of the second lens element, in order from the object side, f4 is the focal length of the fourth lens element, in order from the object side, R2 is the radius of curvature of the image-side surface of the first lens element, in order from the object side, R11 is the radius of curvature of the image-side surface of the fifth lens element, in order from the object side, D2 is the on-axis spacing between the first lens element and the second lens element, in order from the object side, and &ugr;1 is the Abbe number of the optical material of the first lens element.