Patent ID: 7889432
Filing Date: 2011-02-15
Classification: G02B

Abstract:
1. 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: where d 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: 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.