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Color navigation system

  • US 8,111,004 B2
  • Filed: 06/22/2007
  • Issued: 02/07/2012
  • Est. Priority Date: 06/27/2006
  • Status: Expired due to Fees
First Claim
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1. A memory comprising discrete color points and suitable for use with a color navigation system generating light with a variable color, the color points defined according to three-dimensional CIELAB coordinates hue (H), lightness (L), chroma (C), with predefined intervals Δ

  • H between neighboring color points in the hue direction, with predefined intervals Δ

    L between neighboring color points in the lightness direction, and with predefined intervals Δ

    C between neighboring color points in the chroma direction, respectively;

    wherein Δ

    L is equidistant over the color space; and

    wherein Δ

    S is equidistant over the color space, with Δ

    C=Δ



    L, S indicating saturation;

    such that the perceptual color difference Δ

    EINV, defined according to the formula;


    Δ

    EINV=√

    {square root over ((Δ

    L)2+(fC(H

    Δ

    C)2+(Δ

    H)2)}{square root over ((Δ

    L)2+(fC(H

    Δ

    C)2+(Δ

    H)2)}{square root over ((Δ

    L)2+(fC(H

    Δ

    C)2+(Δ

    H)2)}is substantially constant over the color space for steps in the L direction and in the S direction;

    wherein fC(H) is a proportionality factor between 0 and 1 only depending on hue H;

    wherein, for hue values H between a first hue value (H1) corresponding to red and a second hue value (H2) corresponding to green, the proportionality factor fC(H) is equal to 1 and the number of color points in the hue direction in this range is equal to NH,RG;

    wherein, for hue values between the second hue value (H2) corresponding to green and a third hue value (H3) corresponding to blue, the proportionality factor fC(H) is set to a constant value fGB such that the number NH,GB(fGB) of color points in the hue direction in this range differs less than 50% from NH,RG, NH,GB(fGB being equal to NH,RG;

    wherein, for hue values between the third hue value (H3) and the first hue value (H1), the proportionality factor fC(H) is set to a constant value fBR such that the number NH,BR(fBR) of color points in the hue direction in this range differs less than 50% from NH,RG; and

    wherein Δ

    H is a function of H such that, for steps in the hue direction along the border of the color space, said perceptual color difference Δ

    EINV is substantially constant.

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