Wide-angle lens system and imaging apparatus

摘要

A wide-angle lens system includes a first lens group, an aperture stop, and a second lens group having positive optical power. The first lens group includes, at least, a first lens element that has a meniscus shape convex on the object side, and has negative optical power, a second lens element that has a meniscus shape convex on the object side, and has negative optical power, a third lens element that is concave on the image side and has negative optical power, and a posterior lens element. The second lens element is an aspherical lens, and the second lens element satisfies a conditional expression:
0.3<(R21−R22)/(R21+R22)<0.8
where
R21 is a radius of paraxial curvature on the object side of the second lens element, andR22 is a radius of paraxial curvature on the image side of the second lens element.

主权项

1. A wide-angle lens system comprising, in order from an object side to an image side:
a first lens group; an aperture stop; and a second lens group having positive optical power, wherein the first lens group includes
in order from the object side to the image side, at least,a first lens element that has a meniscus shape convex on the object side, and has negative optical power,a second lens element that has a meniscus shape convex on the object side, and has negative optical power,a third lens element that is concave on the image side and has negative optical power, anda posterior lens element, the second lens element is an aspherical lens, the second lens element satisfies a conditional expression (1):
0.45<(R21−R22)/(R21+R22)<0.65  (1) where
R21 is a radius of paraxial curvature on the object side of the second lens element, andR22 is a radius of paraxial curvature on the image side of the second lens element, and the wide-angle lens system satisfies a conditional expression (6):
3.0≦|Th/h|  (6) where
Th is an exit pupil position (a distance from an image surface), andh is an image height.