Optical sensor system and measurement method
First Claim
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1. A method for measuring a signal produced by an optical sensor comprising a light source and a light detector, the method comprising:
- setting an integration time interval to an initial time interval programmed to obtain a voltage amplitude-based optical signal sample point;
applying a drive current to activate the light source during the integration time interval;
integrating a current induced on the light detector to obtain a voltage signal during the integration time interval, wherein the current is induced in response to a light transmitted from the light source to the light detector;
comparing the voltage signal to a threshold during the integration time interval;
converting the voltage signal to the optical signal sample point at the expiration of the integration time interval;
adjusting an optical sensor control parameter in response to the voltage signal crossing the threshold during the integration time interval; and
operating the optical sensor using the adjusted control parameter,wherein adjusting the optical sensor control parameter comprises;
measuring a time interval for the voltage signal to reach the threshold during the integration time interval by measuring a duration of the integration time interval that has elapsed when the threshold is reached,computing a light detector current using the measured time interval, andcomputing the adjusted optical sensor control parameter using the computed light detector current.
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Abstract
A medical device including an optical sensor is configured to measure an optical signal by integrating a current induced on a light detector of the optical sensor to obtain a voltage signal. The voltage signal is compared to a threshold. Responsive to the voltage signal reaching the threshold, an optical sensor control parameter is adjusted. The optical sensor is operated to produce the voltage signal using the adjusted control parameter.
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Citations
24 Claims
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1. A method for measuring a signal produced by an optical sensor comprising a light source and a light detector, the method comprising:
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setting an integration time interval to an initial time interval programmed to obtain a voltage amplitude-based optical signal sample point; applying a drive current to activate the light source during the integration time interval; integrating a current induced on the light detector to obtain a voltage signal during the integration time interval, wherein the current is induced in response to a light transmitted from the light source to the light detector; comparing the voltage signal to a threshold during the integration time interval; converting the voltage signal to the optical signal sample point at the expiration of the integration time interval; adjusting an optical sensor control parameter in response to the voltage signal crossing the threshold during the integration time interval; and operating the optical sensor using the adjusted control parameter, wherein adjusting the optical sensor control parameter comprises; measuring a time interval for the voltage signal to reach the threshold during the integration time interval by measuring a duration of the integration time interval that has elapsed when the threshold is reached, computing a light detector current using the measured time interval, and computing the adjusted optical sensor control parameter using the computed light detector current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A medical device for monitoring a patient using an optical sensor signal, the device comprising:
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an optical sensor comprising a light source and a light detector; a timer set to an initial integration time interval programmed to obtain a voltage amplitude-based optical signal sample point; an integrator configured to integrate a current induced on the light detector to obtain a voltage signal, wherein the current is induced in response to a light transmitted from the light source to the light detector; a converter configured to convert the voltage signal to the optical signal sample point at the expiration of the integration time interval; a comparator configured to compare the voltage signal to a threshold during the integration time interval; and a controller configured to adjust an optical sensor control parameter in response to the voltage signal reaching the threshold during the integration time interval, and operate the optical sensor to produce the optical sensor signal using the adjusted control parameter, wherein adjusting the optical sensor control parameter comprises; measuring a time interval for the voltage signal to reach the threshold during the integration time interval by measuring a duration of the integration time interval that has elapsed when the threshold is reached, computing a light detector current using the measured time interval, and computing the adjusted optical sensor control parameter using the computed light detector current. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A medical device for monitoring a patient using an optical sensor signal, the device comprising:
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an optical sensor comprising a light source and a light detector; an integrator configured to integrate a current induced on the light detector to obtain a voltage signal; a timer configured to set an initial integration time interval programmed to obtain a voltage amplitude-based optical signal sample point; a converter configured to convert the voltage signal to the optical signal sample point at the expiration of the integration time interval; a comparator configured to compare the voltage signal to a threshold during the integration time interval; and a controller configured to adjust an optical sensor control parameter in response to the voltage signal reaching the threshold during the integration time interval and operate the optical sensor to produce the optical sensor signal using the adjusted control parameter, wherein adjusting the optical sensor control parameter comprises; measuring a first voltage signal when the optical sensor light source is not activated to emit light; comparing the first voltage signal to a first threshold; adjusting a first control parameter in response to the first voltage signal reaching the first threshold, the first control parameter adjusted to cause the first voltage signal to fall within a first target range; initiating the integration time interval responsive to activation of the optical sensor light source; measuring a second voltage signal during the integration time interval responsive to activating the optical sensor light source to emit light; comparing the second voltage signal to a second threshold; responsive to the second voltage signal reaching the second threshold during the integration time interval, measuring a duration of the integration time interval that has elapsed responsive to the second voltage signal reaching the threshold, computing a light detector current using the measured time interval, adjusting a second control parameter value using the computed light detector current to cause the second voltage signal to fall within a second target range, the second control parameter different than the first control parameter.
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Specification