Biosignal Measurement Using Wavelength-Selective Inserted Layer
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Solution Overview
Problem
Current biosignal measurement technologies, such as PPG and ECG, face challenges in accurately distinguishing between deep and surface reflections to effectively measure vascular volume changes and contact forces, especially in dynamic environments like wearable devices.
Innovation Solution
The apparatus employs an inserted layer that selectively transmits long-wavelength light and reflects short-wavelength light, allowing for the separation of deep and surface reflected waves, and includes a signal processor to extract biosignal information from these signals, which can be integrated into mobile or wearable devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical detector is used to measure biosignals, then the device structure is simple, but it cannot distinguish between deep and surface reflections, leading to poor measurement precision
Solution Approach 1:
The patent divides the optical measurement into two separate detection paths: one for deep tissue reflection (first optical detector) and one for surface reflection (second optical detector). This segmentation allows independent measurement of deep and surface signals, enabling precise biosignal extraction by separating the desired signal from noise.
Solution Approach 2:
The patent extracts the surface reflection component (which contains motion artifacts and noise) from the total reflected light using the second optical detector. By taking out this interfering component, the system can isolate and measure the deep tissue biosignal more accurately using the first optical detector.
2Measurement precision
If wavelength-selective layers are added to separate deep and surface reflections, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent introduces wavelength-selective layers with different optical properties at different locations in the optical path. The first wavelength-selective layer transmits deep reflected light while blocking surface light, and the second layer performs the opposite function. This local differentiation of optical properties enables precise signal separation.
Solution Approach 2:
The patent changes the wavelength transmission parameters of the optical path by using wavelength-selective layers with specific transmission characteristics. By adjusting which wavelengths are transmitted or blocked at different stages, the system can selectively isolate deep and surface reflected light components.
3Measurement precision
If motion artifacts are not corrected, then the device operation is simple, but biosignal measurement precision deteriorates in dynamic environments
Solution Approach 1:
The patent uses the surface reflection signal detected by the second optical detector as feedback to identify and remove motion artifacts from the deep tissue signal. The surface signal serves as a reference that correlates with motion-induced noise, enabling real-time correction of the biosignal measurement.
Solution Approach 2:
The patent introduces an intermediary processing step where the surface reflection signal acts as a mediator to characterize and eliminate motion artifacts. By using this intermediate measurement, the system can separate true biosignals from motion-induced noise without requiring complex external sensors.
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 enables accurate measurement of biosignals like heartbeats and blood oxygen saturation by distinguishing between deep and surface reflections, improving signal quality and reducing motion artifacts, thus enhancing the reliability of biosignal monitoring in various applications.
Implementation Method 1
an inserted layer that selectively transmits long-wavelength light and reflects short-wavelength light, allowing for the separation of deep and surface reflected waves
Implementation Method 2
measuring light reflected from a body tissue or light transmitted through the body tissue
Data Source
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AI summary
An apparatus for and a method of measuring a biosignal are provided. The apparatus of measuring a biosignal includes an optical source configured to emit a first light and a second light towards a target, an inserted layer configured to transmit the first light and to reflect the second light, and an optical detector configured to detect a first received light that corresponds to the first light reflected by or transmitted through the target, and to detect a second received light that corresponds to the second light reflected by the inserted layer.