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Reflectance measurement apparatus with noise reduction circuitry

  • US 5,177,565 A
  • Filed: 02/11/1991
  • Issued: 01/05/1993
  • Est. Priority Date: 02/11/1991
  • Status: Expired due to Term
First Claim
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1. A reflectance measuring device comprising:

  • a photo-detector situated to detect light reflecting from a chemically treated target strip and producing an electrical signal in accordance with the intensity of light striking said photo-detector;

    a light source having a power input, said light source directed toward the target strip;

    an oscillator which produces an oscillator signal;

    a power source connected to said power input of said light source, said power source supplying a periodic power signal in accordance with said oscillator signal to said power input;

    amplifier means responsive to said electrical signal and producing an amplified electrical signal;

    a band pass filter responsive to said amplified electrical signal having an upper cutoff frequency below the frequency of oscillation of said oscillator and a lower cutoff frequency above zero hertz; and

    wherein said light source produces light in a predetermined range corresponding to a particular colorization response of a chemically treated target strip.

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