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Focusing method in optical lens system with variable focal length

  • US 4,726,667 A
  • Filed: 10/19/1984
  • Issued: 02/23/1988
  • Est. Priority Date: 10/19/1984
  • Status: Expired due to Fees
First Claim
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1. A zoom lens system having a variable focal length, said zoom lens system comprising, in order from an object:

  • a first lens group which is the front most lens group at the object side of the zoom lens, said first lens group having a negative refractive power; and

    a second lens group with a positive refractive power, with a first air gap between said first and second lens groups being variable for varying said refractive power of said optical system without varying any air gaps within said first lens group, said second lens group comprising at least first, second and third lens components, said first lens component having a positive refractive power, said second lens component having a negative refractive power and said third lens component having a positive refractive power, and with a second air gap between said second and third lens components being variable for focusing without varying the refractive power of said lens, said second air gap being contiguous with said second and third lens components with no intervening lens components in said second air gap between said second and third lens components.

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