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Methods and apparatus for estimating a physiological parameter using transforms

  • US 6,094,592 A
  • Filed: 05/26/1998
  • Issued: 07/25/2000
  • Est. Priority Date: 05/26/1998
  • Status: Expired due to Term
First Claim
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1. A method for use in a system for determining a physiological parameter, the system having a sensor for transmitting electromagnetic energy of first and second wavelengths toward a tissue sample and detecting the electromagnetic energy after scattering of the electromagnetic energy by the tissue sample, thereby generating a first signal corresponding to the first wavelength and a second signal corresponding to the second wavelength, the method comprising:

  • transforming the first and second signals into a frequency domain, thereby generating third and fourth signals;

    generating a ratio signal using the third and fourth signals;

    applying more than two variable weights to various parts of the ratio signal, the variable weights being derived with reference to at least one of the third and fourth signals;

    for each of a plurality of ratio values in the ratio signal, generating an associated weighted sum corresponding to each time the ratio signal coincides with the ratio value associated with the sum; and

    selecting a best ratio value from the plurality of ratio values based on the sums associated therewith.

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