| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-magnification microscope objective lens which is constituted so that flare is reduced and the aberration of an exit pupil is excellently corrected even when the pupil is made to near to an object side, whose NA is large and whose operating distance is long. SOLUTION: This objective lens is provided with a 1st lens group G1 having positive refractive power, a 2nd lens group G2 having negative refractive power, an object-side lens G21 and an imageside lens G22 and being the joined meniscus lens whose convex surface faces an object side, a 3rd lens group G3 having negative refractive power, an objet side lens G31 and an image-side lens G32 and being the joined meniscus lens whose concave surface faces an image side and a 4th lens group G4 having positive refractive power in turn from the object side. When the Abbe number of the group G1 is defined as (ν1), the radius of the curvature of the object-side surface thereof is defined as (r1), that of the image-side surface is defined as (r2), the refractive index of the lens G21 of the group G2 is defined as (n2), the radius of the curvature of the most object side thereof is defined as (r3) and the focal distance of a whole lens system at a (d) line is defined as (f), the conditions of 60<=ν1<=70, -0.06<=(r2+r1)/(r2-r1)<=0.06 and 5.9<=n2.f/r3<=6.4 are satisfied.
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