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Method and apparatus for adjusting the focal length of a optical system

  • US 5,091,801 A
  • Filed: 10/19/1989
  • Issued: 02/25/1992
  • Est. Priority Date: 10/19/1989
  • Status: Expired due to Fees
First Claim
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1. A nearly index matched (NIM) optic, comprising:

  • means for receiving light from a light source, the light having a given range of wavelengths;

    means for transferring the light across at least a first surface into a first material having a first index of refraction;

    means for refracting the light across at least a first boundary formed in the first material, each point on the first boundary having an optical curvature of a given sign; and

    means for refracting the light at a second boundary formed in a second material that has a second index of refraction, each point on the second boundary corresponding to a point on the first boundary, each point on the second boundary having an optical curvature that is equal to the curvature of the corresponding point on the first boundary but opposite in sign, said first and second indices selected such that a difference between the second index of refraction and the first index of refraction is less than 0.1 and substantially the same over the range of wavelengths of the light, whereby the absolute value of the optical curvature at corresponding points on the first and second boundaries is reduced by the absolute value of the difference between the first and second indices of refraction thereby permitting control of focal length through selection of said indices.

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