LENS SYSTEM, IMAGE PICKUP DEVICE, MOBILE BODY, AND SYSTEM

WIPO Patent Application WO/2018/150522

A1

This lens system is provided with, in the following order from the object side, a first lens group, an aperture stop, and a second lens group having positive refractive power. The first lens group is provided with, in the following order from the object side, a first (a) lens group having negative refractive power, and a first(b) lens group having positive refractive power. The first (a) lens group includes three negative single lenses, i.e., a meniscus-shaped first negative lens having the convex surface on the object side, a second negative lens having the concave surface on the image side, and a third negative lens having the concave surface on the image side, said three negative single lenses being included in this order from the object side to the image side. The first (b) lens group includes at least one positive lens. The second lens group includes at least two cemented lenses. When the focal point distance of the whole lens system is represented by f, and the focal point distance of the first (a) lens group is represented by f1a, conditional expression of -1.2