| 摘要 |
A zoom lens is equipped with: a first lens group having an overall negative refractive power and a second lens group having an overall positive refractive power in sequence from the object side to the image plane side. Zoom magnification is changed from a wide-angle end to a telephoto end by moving the first lens group to the image plane side and then reversing the motion to the object side while the second lens group is moved to the object side. The condition (1) 0.90<=(DG 1 +DG 2 )/fw<=2.30 and the condition (2) 0.5<=|fG 1 |/fG 2 <=1.6 are met, where DG 1 is the thickness of the first lens group; DG 2 is the thickness of the second lens group; fw is the focal length of the lens system at the wide-angle and; fG 1 is the focal length of the first lens group; and fG 2 is the focal length of the second lens group. With above structure, the power arrangements for the first and second lens groups are set appropriately providing a zoom magnification ratio of approximately 3x beside making the design of the zoon lens compact and thin.
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