Optical PPG Monitoring with Activity-Based Sampling Control
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Solution Overview
Problem
Conventional photoplethysmography devices face challenges in maintaining consistent skin contact during physical activity, leading to reduced signal quality due to motion artifacts and high power consumption, especially when used in wearable forms like earbuds.
Innovation Solution
A monitoring device with a processor that adjusts signal analysis frequency and sensor interrogation power based on detected changes in activity, using optical sensors with adjustable algorithms and power management to optimize data collection during varying activity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical sensor continuously operates at high sampling frequency and high power to maintain signal quality during physical activity, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The patent implements dynamic adjustment of the optical sensor's operating parameters based on detected activity levels. The processor monitors motion artifacts and automatically modifies sampling frequency and power consumption settings in real-time, transitioning between high-precision mode during activity and low-power mode during rest, thereby resolving the contradiction between maintaining signal quality and reducing energy use
Solution Approach 2:
The system changes operational parameters (sampling frequency, power level) based on detected physiological and motion states. By adjusting these parameters dynamically rather than maintaining fixed high settings, the system achieves high measurement precision only when necessary while minimizing overall power consumption
2Measurement precision
If the optical sensor operates at high power to capture accurate physiological data, then measurement precision is improved, but duration of action decreases
Solution Approach 1:
The patent employs periodic high-power sampling interspersed with low-power intervals. The sensor operates at high power only during detected activity periods or when physiological changes are anticipated, and switches to low-power mode during stable states, thereby extending battery life while maintaining measurement accuracy when needed
Solution Approach 2:
The system dynamically adjusts power consumption levels based on activity detection and signal quality assessment, allowing the device to operate efficiently over extended periods while preserving battery life for critical measurement periods
3Stability of the object's composition
If the earbud incorporates spring features to dampen acceleration during vigorous activity, then stability is improved, but optical skin coupling efficiency deteriorates
Solution Approach 1:
The patent replaces reliance on mechanical spring features with an optical-mechanical sensing system. The optical sensor detects motion artifacts and physiological signals, and the processor compensates for motion effects through signal processing algorithms, eliminating the need for mechanical damping features that would compromise optical coupling
Solution Approach 2:
The system introduces motion artifact detection and signal processing as an intermediary between the physical motion and the physiological measurement. By detecting and compensating for motion effects through software algorithms, the system maintains measurement accuracy without requiring mechanical stabilization features
4Stability of the object's composition
If conventional photoplethysmography devices use spring clips to maintain skin contact, then stability is improved, but device complexity increases
Solution Approach 1:
The patent eliminates mechanical spring clip structures by using motion-sensitive optical sensing and digital signal processing to maintain contact consistency. The system detects motion artifacts and compensates for variable contact conditions through algorithms, replacing complex mechanical retention mechanisms with simpler electronic sensing and processing
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
Improves signal quality and reduces power consumption by increasing sampling frequency and power during active periods and decreasing it during inactive periods, enhancing accuracy and extending battery life.
Implementation Method 1
Photoplethysmography (PPG) is based upon shining light into the human body and measuring how the scattered light intensity changes with each pulse of blood flow
Implementation Method 2
measuring how the scattered light intensity changes with each pulse of blood flow
Data Source
AI summary
A monitoring device configured to be attached to a subject includes a photoplethysmography (PPG) sensor configured to measure a plurality of physiological parameters from the subject, a motion sensor configured to detect an activity state of the subject, and a processor coupled to the PPG sensor and the motion sensor. The PPG sensor is configured to measure each physiological parameter in a respective one of a plurality of time intervals. The processor instructs the PPG sensor to measure a first one of the plurality of physiological parameters if the activity state is at or above a threshold, and to measure a second one of the plurality of physiological parameters if the activity state is below the threshold.