Wearable PPG Sensor Network with Tilted Light Sources
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wearable PPG devices face challenges in maintaining signal strength when the wearer is moving, as the strength of optical signals received at the photodetector is easily compromised due to positional changes.
Innovation Solution
A network of reflectance-mode PPG sensors with tilted light sources and detectors, along with machine learning algorithms to dynamically select sensors generating reliable signals, ensuring consistent signal strength and quality even during movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wearable PPG devices use fixed-position light sources and detectors, then device structure is simple, but signal strength is compromised during movement
Solution Approach 1:
The PPG device is divided into multiple independent sensors, each with its own light source and detector positioned at specific angles. This segmentation allows the system to distribute sensing across multiple points, improving signal reliability during movement while managing complexity through modular sensor units.
Solution Approach 2:
The system dynamically selects and switches between active sensors based on real-time signal quality assessment. Machine learning algorithms continuously evaluate sensor performance and adaptively determine which sensors provide reliable signals, allowing the system to maintain optimal performance during user movement without requiring physical reconfiguration.
2Reliability
If multiple PPG sensors are deployed in a network, then signal reliability improves, but computing power requirements increase
Solution Approach 1:
The system extracts and eliminates sensors that fail to meet minimum signal quality thresholds. By identifying and removing unreliable sensors from the active network, the system reduces the computational burden of processing data from all sensors while maintaining reliability through selective use of only the most effective sensors.
Solution Approach 2:
The system changes operational parameters by dynamically adjusting which sensors are active based on signal quality metrics. This parameter change allows the system to optimize the balance between reliability and computing power consumption by activating only the necessary subset of sensors rather than continuously processing data from all sensors.
3Illumination intensity
If light sources are positioned at angled orientations, then optical signal strength is improved, but manufacturing precision requirements increase
Solution Approach 1:
Each sensor unit is designed with locally optimized light source positioning at specific angles relative to the detector. This local quality approach ensures that each individual sensor achieves optimal optical coupling and signal strength, while the overall system maintains robustness through redundancy across multiple sensors, reducing the impact of manufacturing variations.
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
The solution enhances the strength and reliability of detected optical signals, improving the accuracy of physiological parameter measurements and reducing computing power by eliminating unreliable sensors.
Implementation Method 1
A light source (e.g., a light emitting diode (LED)) transmits two different light wavelengths through the skin, and a detector (e.g., a photodiode (PD)) measures the non-absorbed light that is either transmitted through (transmission mode) or reflected by (reflectance/reflective mode) the bone, veins, and other tissues below the skin
Implementation Method 2
The non-absorbed light received at the detector is used to measure the actual difference in the absorption spectra of oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (Hb). HbO2 and Hb absorb different wavelengths. Hb has a higher absorption at 660 nm, and HbO2 has a higher absorption at 940 nm
Data Source
AI summary
Embodiments of the invention are directed to a photoplethysmogram (PPG) structure that includes a wearable component and a network of PPG sensors physically coupled to the wearable component. Each PPG sensor of the network includes a housing, a first light source and a light detector. The first light source is positioned in or on the housing such that, when the housing is positioned on a surface, the housing positions an illuminating surface of the first light source at a predetermined first-light-source angle with respect to the surface.