| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily correct aberration at focusing from a point at infinity up to a close distance. SOLUTION: The macro lens is constituted of a 1st lens group G1 having a positive refractive power, a 2nd lens group G2 having a positive refractive power and a 3rd lens group G3 having a negative refractive power in this order from an object side, the 2nd lens group G2 is constituted of a front group G2f and a rear group G2b having a positive refractive power, and in the case of focusing from the point at infinity to the unmagnification -1, a distance between the front group G2f and the rear group G2b of the 2nd lens group G2 is shifted so as not to reduce but increase the distance at the boundary of the magnification -1/2 while fixing the 3rd lens group G3 with reference to an image field A and extending the 1st lens group G1 and the 2nd lens group G2 toward the object direction. COPYRIGHT: (C)2003,JPO
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