| 摘要 |
PURPOSE:To obtain a telephoto lens which has extremely small aberrations, specially, chromatic aberration and excellent image forming performance by allowing three lens groups to meet specific requirements. CONSTITUTION:The lens system consists of the 1st convergent lens group and divergent lens group and the 2nd convergent lens group. The 1st convergent lengs group consists of the 1st and the 2nd convergent lens and divergent lens and the 3rd convergent lens, the divergent lens group consists of a cemented or single divergent lens and a cemented divergent lens, and the 2nd convergent lens group consists of a convergent lens and a cemented divergent lens. Then, the gap D between both divergent lenses in the divergent lens group is varied while satisfying an inequality I to perform focusing. In the inequality, phi2 is the power of the divergent lens group.
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