Patent ID: 9170401
Filing Date: 2015-10-27
Classification: G02B

Abstract:
1. A wide angle lens, substantially consisting of three lens groups, which are: a first lens group having a positive refractive power which is fixed in the direction of an optical axis during focusing operations; a second lens group that moves along the optical axis during focusing operations; and a third lens group which is fixed in the direction of the optical axis during focusing operations, provided in this order from an object side; the first lens group comprising: a first lens having a positive refractive power and is of a meniscus shape having a convex surface toward the object side; a second lens having a negative refractive power and is of a meniscus shape having a convex surface toward the object side; a third lens having a negative refractive power and a concave surface with a radius of curvature having the smaller absolute value toward an image side; and a fourth lens having a negative refractive power, provided in this order from the object side; the wide angle lens further comprising: a cemented lens formed by cementing a lens having a positive refractive power and a lens having a negative refractive power together, provided more toward the image side than the fourth lens; and an aperture stop provided adjacent to the cemented lens toward the image side thereof; the second lens group substantially consisting of two or fewer lenses; the third lens group comprising at least one positive lens; and the wide angle lens satisfying the following conditional formula: wherein f1 is the focal length of the first lens group, and f is the focal length of the entire system in a state focused on infinity.