| 摘要 |
A zoom lens is composed of, as counted from the object side of the lens, a first lens unit or group having a positive refractive power, a second lens unit or group having a negative refractive power, a third lens unit or group having a positive refractive power, a fourth lens unit or group having a negative refractive power and a fifth lens unit or group having a positive refractive power. Assuming that, when varying the magnifying power of the lens from a wide angle end to a telephoto end, an air space between an i-th lens unit and an i+l-th lens unit varies to a degree DELTA Di, the i-th lens unit has a focal length fi, the focal length of the whole lens system as obtained at the telephoto end is FT, and a space between the first and second lens units varies to a degree DELTA E1 between the wide angle end and the telephoto end, the zoom lens is arranged to satisfy the following conditions: DELTA D1>0 DELTA D2<0 DELTA D3>0 DELTA D4<0 0.046<¦f2/FT¦<0.093 0.22<¦f1/FT¦<0.6 2.1<¦ DELTA E1/f2¦<3.6.
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