Patent ID: 8508856

Claim:
An immersion microscope objective that has, in order from an object side, a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group, wherein: the first lens group includes a cemented lens consisting of a positive lens on the side nearest an object and a meniscus lens having its concave surface on the object side, and a single lens; the second lens group has positive refractive power; and the following conditions are satisfied: 0.15 >n 1 −nw> 0.05 4 >|rb/dt 3|>0.9 fs/f< 1.99 where n 1 is the refractive index of a positive lens nearest the object side in the first lens group, nw is the refractive index of a medium that fills a space between the first lens group and the object, rb is the radius of curvature of a cemented surface of the cemented lens, dt 3 is a distance along an optical axis, in mm, between an object surface and the cemented surface, fs is the focal length of the cemented lens, and f is the focal length of the immersion microscope objective.