| 摘要 |
PURPOSE:To perform focusing while reducing aberrational variation over an object distance by extending a zoom lens wherein a lens group with negative refracting power precedes while decreasing the refracting power of the 1st lens group. CONSTITUTION:The 1st lens group I has negative refracting power and the 2nd lens group II has positive refracting power. when the focus is adjusted from an infinite distance body to a short-distance body, the 1st lens group I is moved out and the refracting power of at least one lens surface in the 1st lens group so as to decrease the negative refracting power of the 1st lens group I on the whole, reducing the aberrational variation. The 2nd lens with negative refracting power from the object side of the 1st lens group I is made of an optical elastic body such as silicone rubber and the object-side and image- side lens surfaces are varied in refracting power.
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