Multiple Source-Detector PPG Sensor Motion Artifact Isolation
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Solution Overview
Problem
Existing photoplethysmography (PPG) sensors face challenges in accurately measuring heart rate and other physiological metrics, particularly during motion, due to signal degradation caused by movement and varying local conditions, as they often rely on single spatial measurements or simple signal averaging without effectively isolating cardiac and motion components.
Innovation Solution
The use of multiple independently addressable source-detector combinations to acquire and process PPG signals from different spatial locations, employing techniques like motion component removal and confidence metric analysis to select the highest-quality signal for estimation, thereby improving signal quality and accuracy during motion and varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple source-detector combinations are used to improve signal quality during motion, then measurement precision improves, but device complexity increases
Solution Approach 1:
The PPG sensor is divided into multiple independent source-detector combinations, where each combination can be independently controlled and addressed. This segmentation allows the system to select or combine signals from different spatial locations to optimize measurement quality during motion while maintaining manageable device complexity through modular architecture.
2Reliability
If multiple PPG signals are acquired from different spatial locations to isolate cardiac signals, then reliability improves, but loss of information increases due to complex signal processing requirements
Solution Approach 1:
The system performs preliminary signal processing by acquiring multiple PPG signals from different spatial locations and preparing them for combination before motion occurs or during motion. This preliminary action includes separating cardiac and motion components in advance, allowing the system to reconstruct reliable physiological measurements without losing critical information during subsequent processing stages.
3Ease of operation
If simple signal averaging is used to process PPG signals, then ease of operation is maintained, but measurement precision deteriorates during motion due to inability to isolate cardiac components
Solution Approach 1:
The system extracts and separates the cardiac signal component from the motion artifact component by acquiring multiple PPG signals from different spatial locations. By taking out the cardiac component independently from motion artifacts, the system achieves accurate heart rate measurement during motion while maintaining operational simplicity through automated component separation algorithms.
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 enhances the accuracy of heart rate and other physiological metric estimations by isolating cardiac signals from motion artifacts and selecting the best signal based on quality metrics, leading to more reliable measurements even during user activities involving motion.
Implementation Method 1
A PPG sensor may be utilized to detect the volumetric change in blood vessels. A PPG sensor usually includes a light source, typically a light-emitting diode (LED), and a light-sensitive sensor, typically a photodiode. Blood passing through the vasculature between the light source and the sensor will modulate the light path between the two, resulting in a deviation in the current produced by the photodiode.
Implementation Method 2
Many wearable PPG devices use green light, as the hemoglobin absorption of light is up to 20 times greater at green wavelengths than at IR wavelengths.
Data Source
AI summary
Systems, devices, and methods for tracking one or more physiological metrics (e.g., heart rate, blood oxygen saturation, and the like) of a user are described. For example, one or more light sources and one or more light detectors may be positioned on a wearable device such that light can be emitted towards the user's skin and further such that light reflected back to the wearable device can be measured and used to generate values for the one or more physiological metrics.