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Structure and method usable for differentiating a plant from soil in a field

  • US 5,389,781 A
  • Filed: 11/10/1993
  • Issued: 02/14/1995
  • Est. Priority Date: 07/28/1992
  • Status: Expired due to Term
First Claim
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1. Structure comprising:

  • a first light emitting diode providing light of a first wavelength, said light of said first wavelength being modulated with a first modulation signal, said light of said first wavelength being incident on an area of a surface, said surface being substantially stationary;

    a second light emitting diode providing light of a second wavelength, said light of said second wavelength being modulated with a second modulation signal, said second modulation signal being phase shifted with respect to said first modulation signal, said light of said second wavelength being incident on said area of said substantially stationary surface;

    a light detector detecting a portion of said light of said first wavelength and a portion of said light of said second wavelength reflecting from said area of said surface, said light detector having an output lead;

    a circuit having an input lead and an output lead, said input lead of said circuit being coupled to said output lead of said light detector;

    an electro-mechanical device coupled to said output lead of said circuit and controlled by said circuit; and

    means for moving said first light emitting diode, said second light emitting diode, said light detector, said circuit, and said electro-mechanical device over said area of said surface.

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