Optical instrument with ambient light removal
First Claim
1. A method of processing a physiological signal to determine a physiological parameter of a subject, the method comprising:
- receiving, using a pulse oximeter, a light signal attenuated by a subject, wherein the light signal comprises a first component corresponding to a desired component and a second component corresponding to an undesired component;
performing, using a pulse oximeter, a first filtering operation on the light signal to remove at least a portion of the undesired component using a first analog filter having a first transfer function to generate a filtered analog signal;
converting, using the pulse oximeter, the filtered analog signal into a digital signal;
performing, using the pulse oximeter, a second filtering operation on the digital signal using a second digital filter having a second transfer function to generate a filtered digital signal, wherein the second transfer function is substantially an inverse of the first transfer function; and
determining, using the pulse oximeter, the physiological parameter based on the filtered digital signal.
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Abstract
Processing circuitry may process a physiological signal such as a light signal attenuated by a subject. The physiological signal may include a desired component and an undesired component. A first filtering operation may be performed to remove at least a portion of the undesired component and a second filtering operation may be performed to reduce an undesired distortion introduced by the first filter. The transfer function of the second filter may be substantially the inverse of the transfer function of the first filter. One or more physiological parameters may be determined based on the filtered physiological signal.
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Citations
21 Claims
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1. A method of processing a physiological signal to determine a physiological parameter of a subject, the method comprising:
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receiving, using a pulse oximeter, a light signal attenuated by a subject, wherein the light signal comprises a first component corresponding to a desired component and a second component corresponding to an undesired component; performing, using a pulse oximeter, a first filtering operation on the light signal to remove at least a portion of the undesired component using a first analog filter having a first transfer function to generate a filtered analog signal; converting, using the pulse oximeter, the filtered analog signal into a digital signal; performing, using the pulse oximeter, a second filtering operation on the digital signal using a second digital filter having a second transfer function to generate a filtered digital signal, wherein the second transfer function is substantially an inverse of the first transfer function; and determining, using the pulse oximeter, the physiological parameter based on the filtered digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A pulse oximetry system for processing a physiological signal to determine a physiological parameter of a subject, the system comprising:
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a pulse oximetry sensor configured to receive a light signal attenuated by a subject, wherein the light signal comprises a first component corresponding to a desired component and a second component corresponding to an undesired component; and a pulse oximeter coupled to the pulse oximetry sensor, wherein the pulse oximeter comprises; a first analog filter having a first transfer function, wherein the first analog filter is configured to perform a first filtering operation on the light signal to remove at least a portion of the undesired component to generate a filtered analog signal; an analog-to-digital converter configured to convert the filtered analog signal into a digital signal; a second digital filter having a second transfer function, wherein the second filter is configured to perform a second filtering operation on the digital signal to generate a filtered digital signal, wherein the second transfer function is substantially an inverse of the first transfer function; and a processor configured to determine the physiological parameter based on the filtered digital signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of processing a physiological signal to determine a physiological parameter of a subject, the method comprising:
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receiving, using a pulse oximeter, a light signal attenuated by a subject, wherein the light signal comprises a first component corresponding to a desired component and a second component corresponding to an undesired component; performing, using a pulse oximeter, a first filtering operation on the light signal to remove at least a portion of the undesired component using a first analog filter to generate a first filtered signal, wherein the first filtering operation introduces a distortion to the first filtered signal; converting, using the pulse oximeter, the first filtered signal into a digital signal; performing, using a pulse oximeter, a second filtering operation on the digital signal to remove at least a portion of the distortion using a second digital filter to generate a second filtered signal; and determining, using the pulse oximeter, the physiological parameter based on the second filtered signal.
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Specification