Biological Signal Measurement Device Intermittent PPG Light Emission
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Solution Overview
Problem
PPG sensors used for measuring pulse transit time consume more power than other biological sensors, leading to battery capacity issues when used for continuous blood pressure monitoring during sleep, resulting in incomplete measurements due to battery depletion, and increasing the device's size and weight to address this issue is not desirable.
Innovation Solution
Implementing intermittent light emission in PPG sensors, synchronized with the detection timing of features in ECG signals, reduces power consumption by optimizing the light emitting period based on the time correlation between ECG and PPG signals, ensuring reliable feature detection without continuous light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PPG sensor uses continuous light emission to ensure reliable pulse transit time measurement, then measurement reliability is improved, but power consumption increases leading to battery capacity shortage
Solution Approach 1:
The PPG sensor implements intermittent light emission synchronized with the ECG signal rhythm, emitting light only during specific cardiac cycles when pulse wave detection is most reliable. This periodic action pattern reduces overall power consumption while maintaining sufficient measurement reliability by concentrating light emission during critical detection windows rather than continuous emission
Solution Approach 2:
The system performs preliminary detection using the ECG sensor to identify optimal timing for PPG light emission. By detecting ECG features first and using this information to trigger subsequent PPG measurements, the system prepares and coordinates the light emission timing in advance, ensuring reliable pulse wave capture only when cardiac activity is detected, thereby reducing unnecessary power consumption
2Duration of action of moving object
If the battery capacity is increased to support continuous measurement, then measurement duration is extended, but device size and weight increase
Solution Approach 1:
By implementing intermittent light emission synchronized with cardiac rhythm, the system significantly reduces average power consumption of the PPG sensor. This extended battery operation capability allows continuous monitoring throughout sleep periods (8+ hours) without requiring larger battery capacity, thereby avoiding increased device weight and size
Solution Approach 2:
The system uses the ECG sensor's continuous monitoring capability to self-regulate the PPG light emission timing. The ECG signal serves as a trigger mechanism that automatically activates PPG measurements only when needed, eliminating the need for external control or larger power reserves, thus maintaining compact device design while extending measurement duration
3Loss of information
If the PPG sensor operates continuously to capture all pulse waves, then data completeness is improved, but energy consumption increases
Solution Approach 1:
The ECG sensor performs preliminary detection of cardiac events and provides timing information that triggers PPG light emission. This preliminary action ensures that light is emitted only during cardiac cycles when pulse wave propagation is occurring, maintaining data completeness by capturing all relevant pulse waves while avoiding energy waste during non-cardiac periods
Solution Approach 2:
The system establishes a feedback loop where ECG detection results control PPG light emission timing. The ECG signal provides real-time feedback about cardiac rhythm, which is used to dynamically adjust PPG measurement timing, ensuring complete pulse wave data capture synchronized with actual cardiac activity while minimizing energy consumption by avoiding fixed continuous operation
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 allows for extended use of the device without increasing size or weight, ensuring continuous and reliable biological signal measurement, particularly during prolonged monitoring periods like sleep, by minimizing power consumption while maintaining accurate data collection.
Implementation Method 1
the light emitting element of the second sensor is driven to perform intermittent light emission
Implementation Method 2
a photoelectric sensor applying plethysmography (PPG) attached to the person's ear
Data Source
AI summary
A device can be used for a long period of time without increasing the size and weight, and a biological signal is surely measured. An aspect of the present invention includes acquiring, from a first sensor, a first biological signal related to a heartbeat of a subject, acquiring, from a second sensor, a second biological signal related to the heartbeat of the subject, detecting a first feature from the first biological signal acquired, setting a light emission control pattern based on a detection timing of the first feature and information indicating time correlation between the first biological signal and the second biological signal, and driving a light emitting element of the second sensor to perform intermittent light emission based on the light emission control pattern set.