Asymmetric Optical Pulse Sensor for Artifact Reduction
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Solution Overview
Problem
Existing pulse rate detection systems face challenges in providing reliable measurements due to movement artifacts and variations in tissue thickness and blood flow, especially when the skin is cold or warm, and they require a balance between minimizing tissue volume and maximizing active blood flow, while also considering portability and battery life.
Innovation Solution
A portable pulse measuring device with a lighting configuration featuring two light-emitting sources of different wavelengths and two light detectors, where the sources are asymmetrically disposed to optimize measurement depth, and a processing means that adjusts light intensity and selects the most reliable channel based on signal-to-noise ratio to minimize movement artifacts and maximize blood flow signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the tissue volume between light source and detector is minimized, then movement artifacts are reduced, but the proportion of active blood flow signal decreases
Solution Approach 1:
The patent implements dynamic adjustment of measurement parameters including light intensity and measurement depth based on detected conditions. The system adaptively modifies operational parameters in real-time to optimize the balance between minimizing movement artifacts and maximizing blood flow signal proportion.
Solution Approach 2:
The system changes physical parameters such as light intensity and measurement depth to optimize measurement quality. By adjusting these parameters dynamically, the system maintains optimal signal quality while adapting to varying tissue conditions and movement levels.
2Reliability
If multiple measurement channels are used to compensate for movement artifacts, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The patent divides the measurement system into multiple independent measurement channels, each capable of detecting photoplethysmographic signals. By segmenting the measurement function across multiple channels, the system can compare and compensate for movement artifacts while maintaining manageable complexity through modular architecture.
Solution Approach 2:
Multiple measurement channels serve dual purposes: primary pulse rate detection and movement artifact compensation. This multi-functionality allows the same hardware components to address multiple measurement challenges simultaneously, reducing overall system complexity.
3Measurement precision
If light intensity is increased to improve signal quality, then measurement accuracy improves, but power consumption increases
Solution Approach 1:
The system dynamically adjusts light intensity based on detected signal quality and movement levels. When movement artifacts are present or signal quality is sufficient, light intensity is reduced to minimize power consumption. When signal quality deteriorates, intensity is increased only as needed.
Solution Approach 2:
The patent implements adaptive parameter changes in light intensity based on measurement conditions. This allows optimization of the trade-off between signal quality and power consumption by adjusting intensity parameters in response to real-time tissue and movement conditions.
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 device provides reliable pulse rate measurements by dynamically adjusting measurement depth and light intensity to match individual conditions, reducing movement artifacts and optimizing power consumption, thus improving measurement accuracy and battery life.
Implementation Method 1
Photoplethysmography is an electro-optic technique of measuring the cardiovascular pulse wave found throughout the human body. The pulse wave is caused by the periodic pulsations of arterial blood volume and is measured by the changing optical absorption of radiant energy which this induces.
Implementation Method 2
In a homogeneous layer of blood, the Beer-Lambert law suggests light intensity to decay exponentially as a function of distance due to light absorption.
Implementation Method 3
However, no tissue is homogeneous, and hence in addition to light absorption factors such as light scatter, refraction and reflection, which all depend on the exact anatomy and geometry of the tissue, also affect the measured signal.
Implementation Method 4
However, no tissue is homogeneous, and hence in addition to light absorption factors such as light scatter, refraction and reflection, which all depend on the exact anatomy and geometry of the tissue, also affect the measured signal.
Implementation Method 5
However, no tissue is homogeneous, and hence in addition to light absorption factors such as light scatter, refraction and reflection, which all depend on the exact anatomy and geometry of the tissue, also affect the measured signal.
Data Source
Figure 1A~1C
Figure 1D~1E
Figure 2A~2B
AI summary
According to an aspect of the invention there is provided a portable pulse measuring device. The device comprises a lighting configuration comprising at least three elements (100, 102, 104, 106) selected from a light-emitting source (104, 106) for emitting radiant energy through a human body tissue and a light detector (100, 102) for detecting the intensity of said radiant energy after propagation through the human body tissue and for providing input signals representative of said propagation, wherein the lighting configuration comprises at least one light-emitting source (104, 106) and at least one light detector (100, 102); processing means for determining pulse rate in response to processing the input signals. The elements in the lighting configuration are arranged in the portable pulse measuring device in a configuration where the light-emitting sources (104, 106) in the lighting configuration are asymmetrically disposed in relation to the light detectors (100, 102) in the lighting configuration.