Oversampling pulse oximeter
First Claim
1. A pulse oximeter, comprising:
- a first source for emitting light having a first spectral content;
a second source for emitting light having a second spectral content different than said first spectral content;
a drive system for pulsing each of said first and second sources according to first and second non-alternating modulation signals, respectively such that said first and second sources output first and second optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods;
a detector for receiving said first and second optical signals and providing a detector signal representative of said received fist and second optical signals; and
a digital sampler, operatively associated with said detector, for providing multiple digital values based on said detector signal corresponding to said series of high output periods and a low output periods of said first and second sources;
a phase detector operative to receive said multiple digital values and identify a synchronized time period where said first and second non-alternating modulation signals are synchronized about a common point; and
a processor for using said multiple digital values associated with said synchronized time period in performing processing steps related to determining an oxygen saturation related value.
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Accused Products
Abstract
An oversampling pulse oximeter includes an analog to digital converter with a sampling rate sufficient to take multiple samples per source cycle. In one embodiment, a pulse oximeter (100) includes two or more light sources (102) driven by light source drives (104) in response to drive signals from a digital signal processing unit (116). The source drives (104) may drive the sources (102) to produce a frequency division multiplex signal. The optical signals transmitted by the light sources (102) are transmitted through a patient'"'"'s appendage (103) and impinge on a detector (106). The detector (106) provides an analog current signal representative of the received optical signals. An amplifier circuit (110) converts the analog current signal to an analog voltage signal in addition to performing a number of other functions. The amplifier circuit (110) outputs an analog voltage signal which is representative of the optical signals from the sources (102). This analog voltage signal is received by a fast A/D converter (112) which samples the analog voltage signal to generate a digital voltage signal which can be processed by the digital signal processing unit (116). The fast A/D converter (112) operates at a rate sufficient to take multiple samples per source cycle and may have a sampling frequency, for example, of over 41 kHz. The digital signal processing unit (116) implements software for averaging the samples over a source cycle for improved measurement consistency, improved signal to noise ratio and reduced A/D converter word length.
123 Citations
23 Claims
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1. A pulse oximeter, comprising:
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a first source for emitting light having a first spectral content; a second source for emitting light having a second spectral content different than said first spectral content; a drive system for pulsing each of said first and second sources according to first and second non-alternating modulation signals, respectively such that said first and second sources output first and second optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods; a detector for receiving said first and second optical signals and providing a detector signal representative of said received fist and second optical signals; and a digital sampler, operatively associated with said detector, for providing multiple digital values based on said detector signal corresponding to said series of high output periods and a low output periods of said first and second sources; a phase detector operative to receive said multiple digital values and identify a synchronized time period where said first and second non-alternating modulation signals are synchronized about a common point; and a processor for using said multiple digital values associated with said synchronized time period in performing processing steps related to determining an oxygen saturation related value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A pulse oximeter, comprising:
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a first source for emitting light having a first spectral content; a second source for emitting light having a second spectral content different than said first spectral content; a drive system for pulsing each of said first and second sources according to first and second non-alternating modulation signals, respectively, such that said fist and second sources output first and second non-alternating optical signals, respectively, each of said first and second non-alternating optical signals including a series of high output periods separated by low output periods; a detector for receiving said first and second optical signals and providing a detector signal representative of said received first and second non-alternating optical signals; a digital sampler, operatively associated with said detector, for providing multiple digital values based on said detector signal corresponding to a series of cycle states including non-alternating high Output periods and low output periods of said first and second sources; and a processor for using said multiple digital values in performing processing steps related to determining an oxygen saturation related value, said processing steps including using said multiple digital values to synchronize first and second demodulation functions with said first and second non-alternating modulating signals, respectively, and implementing said first demodulating function for extracting a first set of data from said digital signal corresponding to said first source and implementing said second demodulating function for extracting a second set of data from said digital signal corresponding to said second source. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification