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UNIFORM ILLUMINATION WITH EDGE LIGHTING

  • US 3,752,974 A
  • Filed: 12/13/1971
  • Issued: 08/14/1973
  • Est. Priority Date: 12/13/1971
  • Status: Expired due to Term
First Claim
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1. A method of providing substantially uniform illumination from an edge lighted optical medium of thickness T, comprising the steps of:

  • a. diffusing one surface portion normally providing internal reflection of the light such that at least some of the light rays striking the diffused surface are reflected through the opposite surface and some are refracted through the one surface to escape out of the medium;

    b. providing a cleared area about the source of light free of the diffusion; and

    , c. treating the cleared area by providing an interface for the surfaces of the optical medium defining the cleared area, said interface having an index of refraction less than that of the medium to assure internal reflection of light rays in the cleared area such that light is channeled by internal reflection between the surfaces and inhibited from escaping from the medium in the vicinity of the cleared area, the channeled light rays expanding towards the diffused surface portion so that the light escaping from the medium as a consequence of the diffused surface portion is substantially uniform with increasing distance from the lighted edge as measured in a plane parallel to the plane of the medium.

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