Optical Sensor System Hybrid Measurement for Blood Oxygen Saturation
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Solution Overview
Problem
Current implantable optical sensors face limitations in measuring blood oxygen saturation due to issues with time-based and amplitude-based measurement systems, such as slow sampling rates for low light intensities and signal clipping at high intensities, which affect the accuracy and efficiency of monitoring.
Innovation Solution
A method combining time-based and amplitude-based measurements in an optical sensor system, where the integration time interval and capacitance are adjusted to prevent signal clipping and maintain a consistent sampling rate, using a hybrid circuit board with multiple light sources and a light barrier to prevent spurious detection, and incorporating a sensor processor to automatically adjust control parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-based measurement is used for low light intensity, then measurement is possible, but sampling rate becomes slow
Solution Approach 1:
The measurement system dynamically switches between time-based and amplitude-based measurement methods depending on light intensity conditions. For low light intensity, time-based measurement is used to ensure measurement capability, while for high light intensity, amplitude-based measurement is used to maintain high sampling rate, thus resolving the contradiction between measurement capability and sampling rate.
Solution Approach 2:
The system changes the measurement parameter (from time-based to amplitude-based) based on light intensity levels. This parameter change allows the system to optimize for either measurement capability or sampling rate depending on the operating conditions, resolving the technical contradiction.
2Productivity
If amplitude-based measurement is used for high light intensity, then sampling rate is high, but signal clipping occurs
Solution Approach 1:
The system dynamically adjusts the measurement method based on light intensity. When light intensity is high, the system uses amplitude-based measurement to achieve high sampling rate, and when light intensity is low, it switches to time-based measurement to prevent signal clipping and maintain measurement accuracy, thus resolving the contradiction between sampling rate and measurement accuracy.
Solution Approach 2:
The system incorporates feedback mechanisms to monitor light intensity levels and automatically switch between measurement methods. This feedback control ensures that the appropriate measurement technique is selected based on current operating conditions, preventing signal clipping while maintaining high sampling rate when possible.
3Reliability
If integration capacitance is increased to prevent clipping, then measurement range increases, but sampling rate decreases
Solution Approach 1:
The system dynamically adjusts integration capacitance based on light intensity conditions. For low light intensity signals that require larger integration capacitance to prevent clipping, the system uses time-based measurement. For high light intensity signals where smaller capacitance can be used, the system employs amplitude-based measurement, thus maintaining both signal accuracy and high sampling rate.
Solution Approach 2:
The system changes the integration capacitance parameter dynamically based on the measurement method selected. This parameter change allows the system to optimize for either signal accuracy or sampling rate depending on the operating conditions and measurement method being used.
4Measurement precision
If integration time interval is extended to improve low light detection, then detection sensitivity increases, but sampling rate decreases
Solution Approach 1:
The system dynamically selects between time-based and amplitude-based measurement methods based on light intensity. For low light conditions, it uses time-based measurement with extended integration time to improve detection sensitivity. For high light conditions, it uses amplitude-based measurement with shorter integration time to maintain high sampling rate, thus resolving the contradiction between detection sensitivity and sampling rate.
Solution Approach 2:
The system changes the integration time interval parameter based on the selected measurement method and light intensity conditions. This parameter change allows the system to optimize detection sensitivity when needed while maintaining high sampling rate when possible.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate and efficient monitoring of blood oxygen saturation by avoiding signal clipping and maintaining a high sampling rate, even under varying light conditions, thereby improving the reliability and precision of physiological parameter estimation.
Implementation Method 1
The light source emits light from the sensor which is reflected or transmitted through an adjacent body tissue back to the sensor
Implementation Method 2
The light source emits light from the sensor which is reflected or transmitted through an adjacent body tissue back to the sensor
Implementation Method 3
The light detector, also referred to herein as a 'photodetector', is a light sensitive device that generates a current signal proportional to the intensity of light received by the light detector
Implementation Method 4
The attenuation of light emitted by the sensor, as measured by the light detector, allows a characteristic of the blood or tissue to be monitored
Data Source
AI summary
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.