Patent ID: 8587879

Claim:
A fixed focus lens comprising, sequentially from an object side, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power, wherein the first lens group includes an aperture stop, the second lens group is configured by a single lens element, during focusing, the second lens group moves along an optical axis and the first lens group and the third lens group are fixed with respect to an imaging plane, a conditional expression (6) 0.3<F1/F<1.1 is satisfied, where F1 is a focal length of the first lens group and F is a focal length of the entire optical system, and a conditional expression (1) 0.7<|(1−β2G)×β3G|<7.0 is satisfied, where β2G is paraxial magnification of the second lens group, at infinity focus and β3G is paraxial magnification of the third lens group, at infinity focus.