Non-invasive Optical Sensor Wavelength Sweeping
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Solution Overview
Problem
Existing non-invasive optical physiological monitoring sensors face challenges in accurately measuring blood and interstitial fluid constituents like glucose due to sensitivity to fluctuations in emitter power and temperature, leading to errors in spectral measurements.
Innovation Solution
The system employs a method where emitter temperature and power variations are intentionally controlled to enhance measurement precision, using multiple wavelengths and thermal controllers to stabilize both the emitter and tissue temperatures, and employs high-speed data collection with multiple detectors to reduce distortion and increase spectral information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emitter power and temperature are kept stable, then measurement reliability is improved, but spectral information quality deteriorates due to lack of wavelength variation
Solution Approach 1:
The system applies periodic modulation to the emitter current, causing the emitter temperature and wavelength to vary periodically. This periodic action allows the system to collect spectral information at multiple wavelengths while maintaining a stable average operating point, thus resolving the contradiction between measurement reliability and spectral information quality
Solution Approach 2:
The system intentionally changes the emitter temperature parameter through controlled current modulation, allowing wavelength variation to enhance spectral information collection. By carefully controlling the parameter changes and using differential pathlength measurements, the system maintains measurement reliability while improving spectral information quality
2Loss of information
If emitter temperature is varied to sweep wavelengths, then spectral information quality is improved, but measurement precision deteriorates due to temperature fluctuations
Solution Approach 1:
The system uses feedback by measuring the emitter temperature and using this information to compensate for wavelength shifts in the spectral analysis. A reference detector monitors the emitter output and provides feedback signals that allow the system to correct for temperature-induced wavelength variations, maintaining measurement precision while enabling spectral sweeping
Solution Approach 2:
The system introduces a reference detector as an intermediary that measures the emitter output directly. This reference measurement serves as a mediator between the emitter and the tissue measurement, allowing the system to separate emitter variations from tissue absorption characteristics and maintain precision during spectral sweeping
3Device complexity
If single wavelength measurement is used, then device complexity is reduced, but measurement precision deteriorates due to insufficient spectral information
Solution Approach 1:
The system uses a single emitter that can operate at multiple wavelengths through temperature modulation, making it universal rather than requiring multiple dedicated light sources. This multi-functionality allows the system to collect spectral information across a wavelength range while avoiding the complexity of multiple separate emitters and detectors
Solution Approach 2:
The system dynamically adjusts the emitter wavelength by varying its temperature, transforming a static single-wavelength measurement into a dynamic multi-wavelength measurement. This dynamic approach enables spectral information collection without requiring multiple static light sources, maintaining simplicity while improving precision
4Productivity
If fast data collection is implemented, then productivity is improved, but measurement precision deteriorates due to increased noise and distortion
Solution Approach 1:
The system uses periodic modulation of the emitter at a known frequency, allowing fast data collection through synchronous detection. By collecting data at multiple points during the periodic cycle and using the known modulation frequency to filter and reconstruct the signal, the system achieves both high productivity and maintained precision through noise rejection
Solution Approach 2:
The system implements continuous modulation and data collection rather than discrete intermittent measurements. This continuous action allows the system to maintain high productivity while using signal processing techniques to extract precise spectral information from the continuous data stream, reducing the impact of noise and distortion
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 allows for accurate and reliable non-invasive prediction of analyte levels, such as glucose, by minimizing errors and maximizing spectral data quality, providing frequent and precise measurements.
Implementation Method 1
a photodetection device(s) detects the attenuated light and outputs a detector signal(s) responsive to the detected attenuated light
Implementation Method 2
thermal controllers to stabilize both the emitter and tissue temperatures
Data Source
AI summary
An optical physiological sensor configured to perform high speed spectral sweep analysis of sample tissue being measured to non-invasively predict an analyte level of a patient. An emitter of the optical physiological sensor can be regulated to operate at different temperatures to emit radiation at different wavelengths. Variation in emitter drive current, duty cycle, and forward voltage can also be used to cause the emitter to emit a range of wavelengths. Informative spectral data can be obtained during the sweeping of specific wavelength regions of sample tissue.