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Estimating heart rate by tracking optical signal frequency components

  • US 10,342,441 B2
  • Filed: 02/01/2016
  • Issued: 07/09/2019
  • Est. Priority Date: 02/27/2015
  • Status: Active Grant
First Claim
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1. A method of estimating heart rate of a user comprising:

  • obtaining a plethysmogram (PG) signal;

    computing a frequency-domain PG based on the obtained PG signal, wherein the frequency-domain PG is an amplitude-versus-frequency representation of the PG signal;

    identifying a plurality of features from the frequency-domain PG, wherein the plurality of features are peaks or troughs;

    applying a set of criteria to identify a subset of the plurality of features as being qualified features, wherein the set of criteria are applied to the frequency-domain PG and include an amplitude based threshold and a bandwidth based threshold, and wherein applying the set of criteria comprises selecting, as qualified features, those features that meet the amplitude based threshold and the bandwidth based threshold;

    after identifying the qualified features, constructing a plurality of traces in a frequency-versus-time mapping using the qualified features, each qualified feature representing a position in the frequency-versus-time mapping, wherein each trace comprises a group of related positions, and wherein the constructing of the plurality of traces comprises, for each qualified feature;

    adding the qualified feature to any trace whose most recent frequency differs from the qualified feature'"'"'s frequency by less than a threshold frequency difference; and

    starting a new trace using the qualified feature when there are no existing traces for which the most recent frequency differs from the qualified feature'"'"'s frequency by less than the threshold frequency difference;

    wherein each trace is started as a new trace using a single qualified feature, and wherein at least one of the traces includes an additional qualified feature added based on a most recent frequency of the trace differing from a frequency of the additional qualified feature by less than the threshold frequency difference;

    selecting a trace from the plurality of traces as representative of the heart rate for a given period of time; and

    using the selected trace to estimate the heart rate of the user.

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