| 摘要 |
PROBLEM TO BE SOLVED: To provide high magnification and high numerical aperture and to compensate aberration over wide visual field by relatively moving a specified lens group in an optical axis direction so that the fluctuation of the aberration can be compensated, and specifying a focal length and the axial distance of the specified lens group at the time of using a reference cover glass. SOLUTION: This lens includes the lens group G1 having positive refractive power, the lens group G2 consisting of a bonded lens obtained by bonding a negative meniscus lens with a biconvex lens, and a bonded lens obtained by bonding a biconcave lens with a biconvex lens, and the lens group G3 having negative refractive power. By relatively moving the lens group G2 in the axial direction with respect to the lens groups G1 and G3, the fluctuation of the aberration is compensated. Furthermore, expressions|f2/F|>50 and 0.3<D1/F<1.2 are satisfied. In the expressions, F means the focal length of the entire system of the objective lens of a microscope, f2 means the focal length of the leng group G2, and D1 means the axial distance of the lens groups G1 to G2 in the case of using the reference cover glass.
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