| 摘要 |
The two-group zoom lens comprises in order from the object side, the first negative lens group, and the second positive lens group. Change of magnification from a wide angle end to a telephoto end is performed by narrowing the interval between two lens groups, and the first negative lens group is moved toward the object side when focusing from focusing at the infinite object point to focusing at a short-distance object point performed, and the following conditions are satisfied. <?in-line-formulae description="In-line Formulae" end="lead"?>0.930<|f<SUB>1</SUB>|/√{square root over ((f<SUB>w</SUB>.f<SUB>T</SUB>)<0.990<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>L<SUB>T</SUB>/L<SUB>W</SUB>>1<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>1.0<(beta<SUB>2w</SUB>)<SUP>2</SUP>xf<SUB>T</SUB>/f<SUB>w</SUB><1.20<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>1.2<|beta<SUB>2T</SUB>|<5<?in-line-formulae description="In-line Formulae" end="tail"?> where f<SUB>1 </SUB>is a focal length of the first lens group, fW is a distance from the surface top of the surface nearest to the object side of the first lens group to an image forming surface at the wide angle end, f<SUB>T </SUB>is a focal length of the whole system of the zoom lens, Lw is a distance from the surface top of the surface nearest to the object side of the first lens group to an image forming surface at the wide angle end, L<SUB>T </SUB>is an actual distance from the surface top of the surface nearest to the object side of the first lens group to an image forming surface, beta<SUB>2w </SUB>is lateral magnification of the second lens group at the wide angle end and beta<SUB>2</SUB><SUB><SUP2>T </SUP2></SUB>is lateral magnification of the second lens group at the telephoto end, when focusing is performed at specified states.
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