Patent ID: 7889432

Claim:
An immersion microscope objective lens comprising: in order from an object, a first lens group with positive refractive power, having a cemented lens of a plano convex lens having a plane facing the object and a meniscus lens having a concave surface facing the object, and a single meniscus lens having a concave surface facing the object; a second lens group with positive refractive power, having plurality of cemented lenses; and a third lens group with negative refractive power, having a cemented meniscus lens having a concave surface facing an image, and a cemented meniscus lens having a concave surface facing the object, the following conditional expression being satisfied: 0.12< d 0/ f< 0.25 where d 0 denotes a distance from the object surface to the first lens surface, and f denotes the focal length of the objective lens, and a positive lens and a negative lens which constitute at least one set of cemented lens in the second lens groups satisfying the following conditional expressions: 0.04<θ Ct ( p )−θ Ct ( n )<0.09 −0.03<θ hg ( p )−θ hg ( n )<0.00 where θCt(p) denotes a partial dispersion ratio of the F-line, C-line and t-line and θhg(p) denotes a partial dispersion ratio of the h-line, g-line, F-line and C-line of the positive lens, and θct(n) denotes a partial dispersion ratio of the F-line, C-line and t-line, and θhg(n) denotes a partial dispersion ratio of the h-line, g-line, F-line and C-line of the negative lens, where the partial dispersion ratio θCt and θhg are defined by θCt=(nC−nt)/(nF−nC) and θhg=(nh−ng)/(nF−nC), when nC denotes a refractive index of the glass material at the C-line, nt denotes a refractive index thereof at the t-line, nF denotes a refractive index thereof at the F-line, nh denotes a refractive index thereof at the h-line, and ng denotes a refractive index thereof at the g-line.