| 摘要 |
A variable magnification optical system and an imaging device are provided to obtain a high resolution imaging signal by outputting the imaging signal according to a high solution optical image. A variable magnification optical system includes first to fifth lens groups(G1-G5) which are sequentially arranged from an object side. The first lens group has a positive refractive power and is fixed when changing magnification and focusing. The second lens group has a negative refractive power and moves when changing the magnification. The third lens group has a positive refractive power and is fixed when varying the magnification and focusing. The fourth lens group has a positive refractive power, moves when changing the magnification, and has a focusing function. The fifth lens group has a negative refractive power and moves when changing the magnification. The variable magnification optical system satisfies conditional expressions: 0.4<fw/f1<0.8 and 0.5<f2/fw<0.8. The fw is a focal length of the whole system at a wide end. The f1 is a focal length of the first lens group. The f2 is a focal length of the second lens group.
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