| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive zoom lens for a microscope having a variable power ratio exceeding 5 times, and having the number of lenses which is small to the utmost. SOLUTION: The zoom lens has in due order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 in which a positive refractive power performing zoom action is moved, and a third lens group G3 in which a positive refractive power performing zoom action is moved, and satisfies following conditional formulas (1), (2) and (3): (1) 0.8<f2/f3<1.3; (2) 0.3<f1/(f2+f3)<1.4; and (3) 0.4<(f2+f3)/L<1.1; wherein f1 is a focal distance of the first lens group G1; f2 is a focal distance of the second lens group G2; f3 is a focal distance of the third lens group G3; and L is a distance from the sample to an image. COPYRIGHT: (C)2011,JPO&INPIT
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