Patent ID: 8441529

Claim:
An endoscope objective lens unit comprising a front lens group and a rear lens group with an aperture stop interposed therebetween, wherein the front lens group includes a first lens having a negative refractive power and a second lens having a positive refractive power in this order from an object side, wherein the rear lens group includes a third lens having a positive refractive power, and a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, the fourth lens and the fifth lens being cemented to each other, and wherein the endoscope objective lens unit satisfies expressions (1A), (2), (3) and (4) below: −3<SF≦−1; (1A) −3.0 <Fr/Ff<− 1.1; (2) −1.6 <Ff/f<− 0.6; and (3) Ff/f 1<1.6, (4) where SF is a shape factor of (R 2 +R 1 )/(R 2 −R 1 ), in which R 1 is an object-side radius of curvature of the second lens and R 2 is an image-side radius of curvature of the second lens, Ff is a focal length of the front lens group, Fr is a focal length of the rear lens group, f is a focal length of the entire unit, and f 1 is a focal length of the first lens.