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Method and apparatus for detecting liquid presence on a reflecting surface using modulated light

  • US 5,508,521 A
  • Filed: 12/05/1994
  • Issued: 04/16/1996
  • Est. Priority Date: 12/05/1994
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting the application of liquid to an optical reflecting surface in the presence of ambient light, the invention comprising, in combination:

  • a light source;

    electronic modulation means controlling the current to said light source to produce a plurality of intensity levels including one off level having no intensity;

    an optical detector for producing electrical signals proportional to light intensity;

    a reaction chamber containing a reflecting surface capable of receiving liquid, said surface positioned so that some light from the source reflects into the optical detector;

    conversion means coupled to the optical detector, and synchronized to the modulation means, for producing at least one intensity sample for each of said intensity levels;

    processing means for computing differences between intensity samples representing light levels and intensity samples representing the off level, said differences being proportional to reflectivity of the reflecting surface in the presence of ambient light;

    reporting means for reporting the presence of liquid on the reflecting surface when said differences change by a predetermined amount.

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