Patent ID: 9207440
Filing Date: 2015-12-08
Classification: G02B

Abstract:
1. An imaging lens consisting of: four groups, a first lens group having negative refractive power, a stop, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power being arranged in this order from the object side, wherein only the third lens group moves in the direction of the optical axis to perform focus adjustment, the first lens group consists of a biconvex lens, a cemented lens constituted by a lens having positive refractive power and a lens having negative refractive power, and a plurality of lenses which include at least one or more lenses having positive refractive power and at least one or more lenses having negative refractive power, in this order from the object side, the second lens group includes at least one or more cemented lenses constituted by a lens having positive refractive power and a lens having negative refractive power, the third lens group consists of a single lens having a meniscus shape with a convex surface toward the object side and negative refractive power or consists of a plurality of lenses having negative refractive power as a whole, which are configured in such a manner that the absolute value of the radius of curvature of a lens surface disposed on the most image side is smaller than the absolute value of the radius of curvature of a lens surface disposed on the most object side, the fourth lens group includes at least one or more lenses having positive refractive power, and conditional expression (1) is satisfied: f f: the focal length of the entire lens system in a state focused on an object point at infinity.