| 摘要 |
PROBLEM TO BE SOLVED: To accomplish drastic miniaturization for a zoom lens and to obtain a high performance by constituting the lens of three groups, each of which has a positive refractive power, a positive one and a negative one, respectively, from an object side, moving each group to the object side in the case of varying the power from a wide angle end to a telephoto end, and also, satisfying specified conditions. SOLUTION: The lens is constituted of the 1st to 3rd lens groups G1 to G3 having the positive refractive power, the positive one and the negative one, respectively from the object side in order, and in the case of varying the power from the wide angle end to the telephoto end, each lens group G1 to G3 is moved to the object side by taking the wide angle end as a reference. The 1st group G1 is constituted of negative and positive lenses, each of which has a convex face on the object side, the 2nd group G2 is constituted of a 1st lens which has a convex face on the object side and a 2nd positive lens which has a face of curvature on the image side, and the 3rd lens group G3 is constituted of a positive lens having a convex face on the image side and a negative lens having a face of curvature on the object side. Each lens group G1 to G3 is provided with at least one aspherical surface, and satisfies the following inequalities; 0.1<ϕ1 /ϕW<0.6 and 1.3<m3 T/m3 W<4W. Provided that the synthetic refractive power of the 1st group G1 at the wide angle end is expressed byϕ1 , the refractive power of the whole system is expressed byϕW, the horizontal magnification of the 3rd group G3 at the wide angle end is expressed by m3 W and the horizontal magnification at the telephoto end is expressed by m3 T.
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