Wearable PPG Sensor with Tunable Laser and Waveguide
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Solution Overview
Problem
Conventional wearable devices for photoplethysmogram measurement face challenges in power management and accuracy due to inefficient light emission and error-prone sensing methodologies, leading to inaccurate health metrics and reduced battery life during physical activities or movements.
Innovation Solution
A wearable device employing a tuneable laser with an optical waveguide and metasurface to direct different wavelengths to various body entry points, combined with multiple detector optical waveguides to increase interaction with vascular features, enhancing signal quality and accuracy without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light emitters are used to provide better illumination and output signal, then the illumination quality and signal output are improved, but the power consumption increases and battery life decreases
Solution Approach 1:
The patent implements periodic illumination by controlling the light emitter to illuminate only during specific time intervals (e.g., during exercise periods or when motion is detected) rather than continuous operation. This periodic action maintains adequate illumination quality when needed while significantly reducing overall power consumption and extending battery life.
2Measurement precision
If more power is fed to the light emitter to obtain acceptable signal quality during physical activity, then the signal quality is improved, but the battery drains faster and the device cannot measure over extended periods
Solution Approach 1:
The patent dynamically adjusts the illumination power and detection parameters based on the user's activity state. During physical exercise or motion, the system increases power to the light emitter and activates multiple detectors to maintain high measurement precision. During rest periods, the system reduces power consumption while maintaining adequate monitoring capability, thus achieving both high signal quality during activity and extended measurement duration overall.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor signal quality and activity levels in real-time. Based on this feedback, the control system automatically adjusts the illumination power and detection frequency to optimize the balance between measurement precision and battery life, allowing extended measurement duration without compromising signal quality when needed.
3Device complexity
If conventional sensing methodology is used, then the device structure is simple, but the accuracy in determining photoplethysmogram is poor due to body feature variations and motion artifacts
Solution Approach 1:
The patent merges multiple detection approaches by combining data from multiple light detectors positioned at different locations, and by integrating information from both optical absorption and scattering measurements. This combination compensates for variations in individual body features and reduces the impact of motion artifacts, significantly improving photoplethysmogram accuracy while maintaining relatively simple device architecture.
Solution Approach 2:
The sensing system is segmented into multiple independent detection channels, each with its own light detector and optical path. By segmenting the measurement into multiple spatial locations and optical paths, the system can select or combine the most reliable signals while rejecting those affected by motion or anatomical variations, thereby improving measurement precision without substantially increasing overall system complexity.
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 achieves improved power management and accurate photoplethysmogram determination, reducing motion artifacts and ensuring consistent health metric monitoring across different body features without battery drain, even during physical activities.
Implementation Method 1
at least a first optical waveguide arranged to receive light from the light source and deliver the received light to the light detector
Implementation Method 2
at least a first light source arranged to provide light towards at least one point on the proband's body
Implementation Method 3
at least a first photodetector arranged to detect light received from the light source through the proband's body
Data Source
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AI summary
A wearable device for determining a photoplethysmogram, includes at least a first light source arranged to provide light towards at least one entry point on a proband's body when the wearable device is used by the proband. The wearable device further includes at least first light detector arranged to detect light received from the light source through the proband's body. The wearable device further includes a control means arranged to calculate a photoplethysmogram based on the detected light. The wearable device further includes at least a first and a second detector optical waveguide arranged to detect light in at least two different positions on the proband's body when the wearable device is used by the proband and feed it to the at least first light detector.