| 摘要 |
PROBLEM TO BE SOLVED: To make a wide-angle and a large aperture compatible in a lens group having a positive refractive power, a specified lens group having a positive refractive power and a lens group having a negative refractive power by moving them to increase/decrease the intervals of these lens groups at the time of zooming from the wide-angle end to the telescopic end. SOLUTION: This lens system is provided, in order from the object side, with a positive lens group G1, a positive lens group G2 provided with a negative meniscus lens and a biconvex lens and a negative lens group G3. At the time of zooming from the wide-angle end W to the telescopic end T, the lens groups G1-G3 are moved to the object side so that an interval between the lens group G1 and the lens group G2 is increased and an interval between the lens group G2 and the lens group G3 is decreased. By representing the focal distance of the negative meniscus lens in the lens group G2 by fa, the radius of curvature of a surface on the object side by r21, the focal distance of the biconvex lens in the lens group G2 by fb and the focal distance of the lens group G1 by f1, relations: 0.4<fb/|fa|<0.8 and 0.2<|r21|/f1<0.4 are satisfied.
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