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Method for the manufacture of fresnel lenses using light-sensitive materials

  • US 3,948,660 A
  • Filed: 08/02/1973
  • Issued: 04/06/1976
  • Est. Priority Date: 08/12/1972
  • Status: Expired due to Term
First Claim
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1. A method of forming a circular one-focal-point Fresnel lens from a layer of light-sensitive material of the type which after exposure to light can be made to undergo a change of optical path-length dependent upon the amount of exposure to light by subjecting the light-sensitive material to a predetermined reaction, comprising, in combination, the steps of positioning a layer of such light-sensitive material coincident with the focal surface of a circular phase zone lens comprised of concentric annular lens components whose successive radii are proportional to the square roots of successive integers and whose successive focal lengths are inversely proportional to the square roots of the respective integers so as to together define a focal surface each portion of which is spaced from the phase zone lens by a distance inversely proportional to the square root of the distance of the portion from the central symmetry axis of the circular phase zone lens;

  • directing light towards that side of the circular phase zone lens which faces away from the layer of light-sensitive material, so that the light emerges through that side of the circular phase zone lens which faces towards the layer of light sensitive material and impinges upon the layer of light-sensitive material; and

    converting the exposed layer of light-sensitive material into a circular one-focal-point Fresnel lens by subjecting the light-sensitive material to the predetermined reaction to cause each exposed portion of the layer of light-sensitive material to undergo a change of optical path-length corresponding to the exposure of such portion.

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