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Fresnel lens and lighting apparatus provided with the fresnel lens

  • US 20060056185A1
  • Filed: 09/14/2005
  • Published: 03/16/2006
  • Est. Priority Date: 09/16/2004
  • Status: Active Grant
First Claim
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1. A Fresnel lens having an optical axis comprising:

  • N pieces of Fresnel lens segments which are made of a lens material whose refraction index is n, and arranged concentrically around a common optical axis, configured to project light rays from a light source at a specified radiation view angle φ

    to an illumination area, and are made into ridge shapes respectively, wherein each Fresnel lens segment includes a lens surface which is curved into a concave surface toward the illumination area, and has a top area and a bottom area;

    a rise surface which is arranged between adjacent lens surfaces, and joints with the top area and the bottom area, the top area and a bottom area defining first and second tangent lines contacting the top and bottom areas of the each lens surface in a cross section including the optical axis, respectively, and the angle between these first and second tangent lines being defined as θ

    , and an inequality of θ



    φ

    /(2 n N) being established.

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