Selection of preset filter parameters based on signal quality

1. In a system for measuring a physiological parameter, a method of reducing noise effects, comprising:

receiving input signals of more than one wavelength;

obtaining an assessment of the signal quality of the input signals by obtaining a measure of the correlation between the signals of different wavelengths;

selecting coefficients for a digital filter using the assessment of signal quality; and

filtering the input signals using the digital filter, without comparing the filter's output signal with the input signals.

2. The method of claim 1 wherein selecting comprises selecting coefficients from a plurality of discrete preset values.

3. The method of claim 1 wherein selecting comprises selecting coefficients from a plurality of constant and preset values.

4. The method of claim 1 wherein filtering comprises operating a digital filter having a linear input-output relationship.

5. The method of claim 1 wherein filtering comprises operating a digital filter having a non-linear input-output relationship.

6. The method of claim 1 wherein selecting is performed in real time, with the coefficients of the digital filter being determined using a current input sample.

7. The method of claim 1 wherein selecting is performed using a previously stored input signal sample.

8. The method of claim 1 wherein receiving comprises receiving signals from an oximeter, wherein the signals are a function of an oxygen saturation.

9. The method of claim 1 wherein receiving comprises receiving signals from an oximeter, wherein the signals are a function of a pulse rate.

10. The method of claim 1 wherein receiving the input signals comprises receiving signals corresponding to sensed optical energies from a plurality of wavelengths.

11. In a system for a measuring a physiological parameter, an apparatus for reducing noise effects, comprising:

means for receiving input signals of more than one wavelength;

means for obtaining an assessment of the signal quality of the input signals by obtaining a measure of the correlation between the signals of different wavelengths;

means for selecting coefficients for a digital filter using the assessment of signal quality; and

means for filtering the input signals using the digital filter, without comparing the filter's output signal with said input signals.

12. The apparatus of claim 11 wherein the means for selecting are configured to select the coefficients from a plurality of discrete preset values.

13. The apparatus of claim 11 wherein the means for selecting are configured to select the coefficients from a plurality of constant and preset values.

14. The apparatus of claim 11 wherein the means for filtering comprise a digital filter having a linear input-output relationship.

15. The apparatus of claim 11 wherein the means for filtering comprise a digital filter having a non-linear input-output relationship.

16. The apparatus of claim 11 wherein the means for selecting are configured to select the coefficients in real time, with the coefficients for the digital filter being determined using a current input sample.

17. The apparatus of claim 11 wherein the means for selecting are configured to select the coefficients using a previously stored input signal sample.

18. The apparatus of claim 11 wherein the means for receiving are configured to receive signals from an oximeter, wherein the signals are a function of an oxygen saturation.

19. The apparatus of claim 11 wherein the means for receiving are configured to receive signals from an oximeter, wherein the signals are a function of a pulse rate.

20. The apparatus of claim 11 wherein the means for receiving are configured to receive signals corresponding to sensed optical energies from a plurality of wavelengths.