Patent ID: 8023198

Claim:
A lens system comprising, in order from an object: a first lens group having negative refractive power, and a second lens group having positive refractive power, the first lens group including, in order from the object, a lens having negative refractive power, a plastic aspherical lens and a lens having positive refractive power, and the following conditional expression being satisfied: 7.0 <|fp/f 1|≦12.4 where fp denotes a focal length of the plastic aspherical lens, and f 1 denotes a focal length of the first lens group, and wherein the plastic aspherical lens of the first lens group satisfies the following conditional expression: p2>4.5 where p 2 denotes a form factor (the form factor p 2 is defined, by p 2 =|(r 2 +r 1 )/(r 2 −r 1 )|, where r 1 denotes a radius of curvature of the plastic aspherical lens on an object side lens surface on an optical axis, and r 2 denotes a radius of curvature of the plastic aspherical lens on an image side lens surface on the optical axis.