| 摘要 |
PROBLEM TO BE SOLVED: To obtain an objective lens for a microscope for middle and high magnification capable of reducing cost while maintaining an excellent image forming function by making a positive lens element in a 2nd lens group to satisfy a specified conditional expression. SOLUTION: This lens is composed of a 1st lens group G1 having negative refractive power as a whole, the 2nd lens group G2 provided with a 1st positive lens element L21 having biconvex shape whose powerful convex surface is faced to an image side and a 2nd positive lens element L22 having the biconvex shape whose powerful convex surface is faced to an object side, and a 3rd lens group G3 in order from the object side. When it is assumed that the radii of curvature of the lens surfaces of the element L21 on the object side and the image side are R1a and R1b, respectively, the center thickness thereof is D1, and the refractive index of optical material constituting the element L21 is N1, and the radii of curvature of the lens surfaces of the element L22 on the object side and the image side are R2a and R2b, respectively, the center thickness thereof is D2, and the refractive index of the optical material constituting the element L22 is N2, the lens satisfies the conditional expressions,|R1a|=|R2b|,|R1b|=|R2a|, D1=D2, N1=N2,|R1a|>|R1b|, and|R2a|<|R2b|.
|
