| 摘要 |
PROBLEM TO BE SOLVED: To provide the zoom optical system of a two-group zoom constitution by which the variable power ratio of >=3 is attained, whose telephoto ratio is <=0.85, which is miniaturized and has an excellent image formation performance and a camera using it. SOLUTION: In the zoom optical system that is constituted of the first lens group G1 of positive refracting power and the second lens group G2 of negative refracting power in order from an object side and in which each lens group is moved to the object side so as to make an interval between the first lens group G1 and the second lens group G2 smaller at the time of variable power from a wide angle end to a telephoto end, the first lens group G1 is constituted of a first lens unit U1 having the positive refracting power, a second lens unit U2 having the negative refracting power and a third lens unit U3 having the positive refracting power in order from the object side, and a third lens unit U3 is constituted of a doublet and also satisfies conditional expression (1) of fT/fW>3...(1), and then, fT means the focal distance of the entire system of a most telephoto end and fW means the focal distance of the entire system of a most wide angle end.
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