| 摘要 |
The invention concerns a zoom lens that has a zoom ratio of the order of 3, and is of sufficiently compact size and improved optical properties. The zoom lens comprises, in order from its object side, a first lens unit having negative refracting power, a second lens unit having positive refracting power and a third lens unit having positive refracting power, wherein the space between adjacent lens units is varied for zooming. The first lens unit consists of, in order from its object side, one positive lens and one negative lens, and the second lens unit consists of, in order from its object side, two positive lenses and one negative lens. The third lens unit consists of one positive lens, and satisfies the following condition. <?in-line-formulae description="In-line Formulae" end="lead"?>0.5<(R<SUB>1</SUB>-R<SUB>2</SUB>)/(R<SUB>1</SUB>+R<SUB>2</SUB>)<0.95<?in-line-formulae description="In-line Formulae" end="tail"?> Here R<SUB>1 </SUB>and R<SUB>2 </SUB>are the axial radii of curvature of the object- and image-side surfaces of the positive lens in the third lens unit, respectively.
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