Adaptive Sampling PPG Ring Sensor for Power Efficiency
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Solution Overview
Problem
Wearable health monitoring devices using photoplethysmogram (PPG) technology face challenges in power efficiency and signal quality due to user movement causing ambient light artifacts, and the need for continuous operation requiring substantial battery power.
Innovation Solution
An apparatus and method employing a ring structure with photon sources and detectors, using adaptive sampling rates based on preliminary PPG measurements to determine the number and distribution of samples, and applying DC offset dynamically to maintain signal quality while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous PPG measurement is performed to monitor user health parameters, then health monitoring reliability is improved, but power consumption increases substantially
Solution Approach 1:
The patent implements periodic measurement cycles with alternating high and low sampling rates. The controller alternates between a first measurement cycle using a first sampling rate and a second measurement cycle using a second sampling rate, enabling continuous health monitoring while reducing average power consumption through periodic low-power operation.
Solution Approach 2:
The patent dynamically adjusts the sampling rate based on detected motion artifacts. When motion artifacts are detected in PPG signals, the system automatically switches to a higher sampling rate to capture the distorted waveform characteristics, and returns to lower sampling rate when motion artifacts are absent, optimizing the balance between measurement reliability and power consumption.
2Measurement precision
If high sampling rate is used to capture motion artifacts accurately, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system periodically switches between high and low sampling rates based on detected motion artifacts. During periods without motion artifacts, low sampling rate is used to conserve power. When motion artifacts are detected, high sampling rate is activated temporarily to accurately capture the distorted PPG waveform, then returns to low sampling rate afterward.
Solution Approach 2:
The patent changes the sampling rate parameter dynamically based on motion artifact detection. The controller adjusts the sampling rate from a first value to a second value (and vice versa) depending on the presence of motion artifacts, optimizing measurement precision only when necessary while maintaining power efficiency during normal conditions.
3Measurement precision
If DC offset is applied to remove ambient light artifacts, then signal quality is improved, but signal distortion occurs
Solution Approach 1:
The patent dynamically adjusts the DC offset value based on detected motion artifacts. When motion artifacts are present, the system modifies the DC offset to account for the additional distortion, and uses this adjusted offset during subsequent signal processing. This dynamic adjustment allows the system to maintain signal quality by compensating for motion-induced variations while minimizing information loss.
4Ease of operation
If wearable device is made lightweight for user comfort, then ease of operation is improved, but battery capacity is reduced
Solution Approach 1:
The patent implements periodic alternation between high and low sampling rates, enabling the use of smaller batteries in lightweight wearable devices. By switching to low sampling rate during periods without motion artifacts, the average power consumption is reduced, extending battery life and allowing for smaller, lighter battery compartments while maintaining continuous monitoring capability.
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 provides power-efficient PPG measurement with improved signal quality by adjusting sampling rates and DC offset, extending battery life and minimizing artifacts, allowing for precise health monitoring without distorting signal quality.
Implementation Method 1
One such example includes a device, which uses photoplethysmogram (PPG) technology for deriving various health monitoring related information such as respiration, pulse, oxygen saturation, user's movement and the like. A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption.
Implementation Method 2
A pulse oximeter monitors the perfusion of blood to the dermis and subcutaneous tissue of the skin... illuminates the skin and measures changes in light absorption
Data Source
AI summary
Disclosed is an apparatus for measuring photoplethysmogram. The apparatus includes a ring structure with at least one photon source and at least one photon detector positioned on an inner surface of the ring structure. The apparatus further includes a controller configured to measure a preliminary photoplethysmogram during a first time period by taking a first number of samples, determine a form factor from said preliminary photoplethysmogram, determine an inter beat interval from said preliminary photoplethysmogram, and use the form factor and the inter beat interval to determine a second number of samples to be taken during a second time period of measurement of the photoplethysmogram and the distribution of the samples to be taken in function of time.