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Signal processing apparatus

  • US 8,046,041 B2
  • Filed: 06/21/2007
  • Issued: 10/25/2011
  • Est. Priority Date: 03/07/1991
  • Status: Expired due to Fees
First Claim
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1. A pulse oximetry system comprising:

  • an optical probe including light emitting elements and a light detecting element, said light detecting element configured to output a signal representative of light attenuated by tissue of a patient, said signal comprising signal portions and noise portions, said detecting element further configured to output a signal representative of an ambient light signal;

    a control circuit configured to supply control signals to the light emitting elements, the control signals configured to alternately generate light at two different wavelengths using a modulation frequency; and

    a patient monitor comprising;

    a sensor port communicating with said optical probe to receive said signal; and

    a processing circuit configured to process the output signal to generate a processed signal, the processing circuit comprising;

    an analog-to-digital converter configured to digitize the output signal to produce a digital signal,a demodulator configured to remove the modulation frequency from the digital signal,a filter having an effective cut-off frequency higher than a human pulse rate and configured to attenuate the demodulated digital signal at an ambient light frequency nearest the modulation frequency, anda calculation module configured to identify a physiological parameter of interest based at least on the filtered, demodulated digital signal;

    wherein the calculation module includes a self-adapting processor configured to optimize the filtered demodulated digital signal.

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