HIGH PERFORMANCE, LARGE APERTURE RATIO IMAGING LENS OF TWO-LENS CONFIGURATION AND F VALUE OF 3 OR LESS

摘要

PROBLEM TO BE SOLVED: To provide a high performance and large aperture ratio imaging lens that satisfactorily corrects chromatic aberration by the use of a diffracting optical face which is a lens system composed of two groups of two lenses, has wide band light, and is optimum for photographing an object at a wide angle of a view. SOLUTION: The imaging lens is composed of the lens system that includes, in order from an object side, a first lens, a diaphragm 4, and a second lens. The first face and the second face of the first lens are convex and concave, respectively. The first face and the second face of the second lens are concave and convex, respectively. Faces of the lenses are aspherical. The first face of the second lens is formed of the diffracting optical face that exhibits a chromatic dispersion function. The lens satisfies an expression (1): 0.11<(L/R)/(V1/V2)<-0.07 where R is the average curvature radius of the first face of the second lens, L is a distance from a diaphragm to the first face of the second lens, V1 is the Abbe number on the line (e) of the first lens material, and the V2 is the Abbe number on the line (e) of the second lens material. The lens also satisfies an expression (2): 0.09