Patent ID: 6016226
Filing Date: 2000-01-18
Classification: G02B

Abstract:
An objective lens for a microscope comprising:a first lens group positioned far from a surface of an object and having a negative refractive power;a second lens group disposed between the object and said first lens group and having a positive refractive power;said first lens group including a compound lens comprising a cemented doublet with a lens having a convex surface facing the object side and a lens having a concave surface facing the image side; andsaid second lens group including a single lens having a convex surface facing the object side, a compound lens comprising a cemented doublet with a lens having a convex surface facing the object side and a lens having a concave surface facing the image side, a first compound lens comprising a cemented triplet, and three meniscus lenses proximate to the object with a concave surface of the meniscus lens of said three meniscus lenses closest to the object facing the object;wherein said objective lens satisfies the following conditions:5F<D<15F;F<.vertline.F1.vertline.<2.5F;25<.nu.2p-.nu.2n<60;0.01F<1/r<0.06F;and1.6<n;where D is a distance between said first lens group and said second lens group, F is a focal length of said objective lens, F1 is a focal length of said first lens group, .nu.2p is an average Abbe number of all convex lenses of said second lens group, .nu.2n is an average Abbe number of all concave lenses of said second lens group, r is a radius of curvature of said concave surface of said meniscus lens, and n is a refractive index of an object side end of said objective lens at d-line.