Patent ID: 8570671

Claim:
A single focus lens system comprising a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, sequentially arranged in order from an object side, wherein the first lens group comprises first and second air lenses having a negative refractive power, a meniscus shape and a convex surface toward the object side, and the second lens group comprises a lens that has a positive refractive power, is disposed closest to the object side, and has a convex surface toward the object side, wherein the single focus lens system satisfies the following expressions, −10 <F air1 /F<− 2.5 −6 <F air2 /F<− 1 0.6 <Fp 2 /F< 1.5, where F denotes an overall focal length, Fair 1 denotes a focal length of the first air lens of the first lens group, Fair 2 denotes a focal length of the second air lens of the first lens group, and Fp 2 denotes a focal length of the lens of the second lens group.