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PHOTOPLETHYSMOGRAPHY

  • US 20140243622A1
  • Filed: 05/14/2014
  • Published: 08/28/2014
  • Est. Priority Date: 04/11/2006
  • Status: Active Grant
First Claim
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1. A photoplethysmograph device comprising:

  • a plurality of light sources each for illuminating a portion of a target object, each of the plurality of light sources having an optical output at a different wavelength;

    one or more modulators for driving the light sources such that the output intensity of each light source varies as a function of a modulation signal at a modulation frequency;

    one or more detectors for receiving light from the target object and generating one or more electrical outputs as a function of the intensity of received light;

    a plurality of demodulators each for receiving one or more of the electrical outputs, each one of the plurality of demodulators producing a demodulated output representative of the modulation signal and any sidebands thereof of a respective different one of the optical wavelengths, to thereby produce a plurality of demodulated outputs corresponding to the plurality of light sources and/or plurality of detectors;

    means for generating, from the demodulated outputs, photoplethysmogram signals indicative of blood volume as a function of time and/or blood composition for each of the demodulator outputs; and

    means for selecting one of the demodulated outputs that provides the best signal-to-noise ratio.

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