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Methods and apparatus for sorting workpieces according to their color signature

  • US 4,278,538 A
  • Filed: 04/10/1979
  • Issued: 07/14/1981
  • Est. Priority Date: 04/10/1979
  • Status: Expired due to Term
First Claim
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1. A method of sorting workpieces according to their colour, wherein positive colour determination is difficult for certain workpiece colours, comprising the steps of:

  • (a) advancing a workpiece to be sorted towards a workstation;

    (b) directing a beam of light at said workpiece to illuminate the same while said workpiece is positioned at said workstation;

    (c) measuring the amplitude of three different spectral components in the light which is diffusely reflected off said workpiece, the first and second ones of said components respectively corresponding to the first and second colours of any set of three colours which satisfy the Tristimulus Theory, said third component corresponding to at least the major lobe of the third one of said set of three colours, which satisfy the Tristimulus Theory;

    (d) synthesizing an amplitude which substantially corresponds to the amplitude of the spectral component that would have been measured for the third one of said set of three colours which satisfy the Tristimulus Theory, by adding the amplitude of said third component to a moiety of the amplitude of said first component;

    (e) comparing the amplitudes of said first and second spectral components, and said synthesized spectral component, to successive ones of a plurality of sets of spectral component amplitudes each set of which defines a possible colour for said workpiece, thereby to determine the colour of said workpiece when the results of the comparison indicate a match;

    (f) summing the amplitudes of said first and second spectral components, and said synthesized spectral component;

    (g) additionally comparing the sum of the amplitudes obtained in said summing step to the sum of the amplitudes in those ones of said plurality of sets of spectral component amplitudes of greatest interest, thereby to positively determine the colour of said workpiece when the results of said additional comparison indicate a match;

    (h) moving a discharge member, in accordance with the results of steps (c) through (g) until said discharge member is aligned with the receptacle assigned to receive workpieces of said determined colour; and

    then,(i) releasing said workpiece from said workstation so that said workpiece traverses said discharge member and is received within said receptacle.

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