| 摘要 |
PROBLEM TO BE SOLVED: To provide an afocal zoom lens for a microscope, which has an overall length reduced to simultaneously realize a high variable power ratio and improvement of aberration performance in all variable power areas and not only has an exit pupil less varied at a high power end from a low power end but also has the quantity of light like the quantity of peripheral light less reduced to improve systematizability as an optical system. SOLUTION: The afocal zoom lens for a microscope comprises five lens groups G1 to G5 having positive, negative, negative, positive, and negative refracting powers respectively in order from the object side. When the power is varied from the low power end to the high power end, thr first and fifth lens groups G1 and G5 are fixed, and the second lens group G2 is moved to the image side, and the fourth lens group G4 is moved to the object side. The second and third lens groups satisfy 0≤F2/F3≤2.5 wherein F2 is the focal length of the second lens group and F3 is that of the third lens group. The third lens group G3 comprises at least one negative lens L3<SB>1</SB>having a concave directed to the object side. COPYRIGHT: (C)2005,JPO&NCIPI
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