| 摘要 |
A lens system comprising a first lens group with a negative refractive power, a second lens group with a positive refractive power, and a third lens group with a positive refractive power arranged in this order from an object side, wherein a focal length f 2 of the second lens group, a focal length f 3 of the third lens group and a radius of curvature Rm of an object side-surface of a lens that is closest to the object side in the second lens group satisfy following conditions <?in-line-formulae description="In-line Formulae" end="lead"?>0.30<Rm/f 2 <0.45<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.8<f 2/ f 3 <1.2.<?in-line-formulae description="In-line Formulae" end="tail"?> The present invention provides a lens system with favorable telemetric characteristics for a digital camera and a sufficient aberration performance using a total of just seven lenses without using an aspherical lens.
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