Electro-Optical Sensor Layout for Motion Artifact Cancellation
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Solution Overview
Problem
Conventional optical and electrode-based physiologic sensors suffer from motion-induced noise during activities, making it difficult to accurately measure biometrics such as blood pressure, heart rate, oxygen saturation, and other physiologic parameters simultaneously and accurately.
Innovation Solution
The electro-optical physiologic sensor integrates co-located electrode-based and optical-based sensing elements, allowing for superior motion noise correlation and cancellation, providing a robust, virtually noise-free signal by using a printed circuit board with a light emitter and photodetector, and incorporating a tissue contact sensor to conserve battery power and enhance sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical and electrode-based sensors are used separately, then each sensor can measure its respective parameter, but motion-induced noise degrades measurement accuracy for both
Solution Approach 1:
The patent combines optical sensing elements (light emitter and photodetector) with electrode-based sensing elements on a single substrate, creating an integrated sensor that simultaneously captures both optical and electrical signals. This merging allows the system to leverage both sensing modalities to measure the same physiologic parameter, enabling noise correlation and cancellation between the two independent measurement pathways, thereby improving measurement accuracy under motion conditions
Solution Approach 2:
The integrated sensor enables feedback-based noise cancellation by using signals from one sensing modality (e.g., electrode-based) to correct and cancel motion-induced noise in the other modality (e.g., optical). The co-located sensors provide correlated noise signals that can be processed to identify and eliminate motion artifacts, creating a feedback loop that continuously improves signal quality during physical activity
2Measurement precision
If multiple sensing elements are integrated on a single substrate, then motion noise correlation and cancellation improve, but device complexity increases
Solution Approach 1:
The patent merges multiple sensing elements (light emitter, photodetector, first electrode, second electrode) onto a single substrate, integrating both optical and electrode-based sensing pathways in one compact structure. This consolidation reduces the overall system complexity compared to using separate sensors, while maintaining the capability for noise correlation and cancellation through the co-located arrangement of all sensing elements
Solution Approach 2:
The integrated substrate serves multiple functions simultaneously: it supports optical sensing for photoplethysmographic measurements, electrode-based sensing for electrical impedance or ECG measurements, and provides a common reference plane for noise cancellation. This multi-functionality eliminates the need for separate sensor modules, reducing device complexity while enhancing noise rejection capabilities
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 arrangement effectively reduces motion artifacts, enhances battery life in small devices, and provides accurate biomarker readings by canceling optical and electrical sensor signal noise, enabling precise measurement of physiologic parameters like blood pressure, heart rate, oxygen saturation, and others.
Implementation Method 1
a light emitter mounted to the PCB and a first optical window through which light produced by the light emitter can pass into tissue of a subject
Implementation Method 2
a photodetector mounted to the PCB and a second optical window through which light received from the subject's tissue resulting from the light produced by the light emitter can pass
Implementation Method 3
at least a tissue contacting surface of the first and second optical windows comprises optically transparent and electrically conductive material
Implementation Method 4
at least a tissue contacting surface of the first and second optical windows comprises optically transparent and electrically conductive material
Data Source
AI summary
An electro-optical physiologic sensor comprises a printed circuit board (PCB) and a light emitter and a photodetector respectively mounted to the PCB. A first sensor element is disposed on the PCB and comprises a first electrode configured to contact tissue of a subject and a first light channel co-located with the first electrode, the first light channel optically coupled to the light emitter and configured to direct light into the subject's tissue. A second sensor element is disposed on the PCB and comprises a second electrode configured to contact the subject's tissue and a second light channel co-located with the second electrode, the second light channel optically coupled to the photodetector and configured to receive light from the tissue of the subject resulting from the light generated by the light emitter.