Biosignal Sensor Polarizer Noise Reduction
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Solution Overview
Problem
Biosignal sensors face performance degradation due to noise caused by positional changes between the skin and the sensor resulting from motion, which affects the accuracy of bio-information acquisition.
Innovation Solution
A biosignal sensor design incorporating a light-transmitting layer with varying elastic moduli and polarizers oriented at specific angles to selectively block or transmit polarized light, reducing noise from skin motions and enhancing signal fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensor is made flexible to attach to skin, then ease of operation is improved, but measurement precision deteriorates due to positional changes from motion
Solution Approach 1:
The light-transmitting layer is divided into multiple regions with different elastic moduli (first region with higher elasticity, second region with lower elasticity). This segmentation allows different parts of the sensor to have different mechanical properties, enabling the sensor to accommodate skin motion while maintaining stable optical contact for accurate measurement.
Solution Approach 2:
Different regions of the light-transmitting layer are assigned different elastic moduli to perform different functions. The first region with higher elastic modulus provides structural stability for the optical components, while the second region with lower elastic modulus provides flexibility to accommodate skin motion, thus resolving the contradiction between flexibility and measurement stability.
2Measurement precision
If polarizers are added to reduce motion noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Polarizers are introduced as intermediary optical components between the light source and the skin, and between the skin and the light sensor. These polarizers selectively transmit or block light based on polarization direction, acting as mediators to filter out noise caused by skin motion while allowing the useful biosignal to pass through.
Solution Approach 2:
The polarization state of light is changed as it passes through the polarizers. By controlling the polarization parameters of the light (transmitting certain polarization directions and blocking others), the system can distinguish between light signals affected by skin motion and those containing useful biosignal information, thereby improving measurement precision.
3Measurement precision
If regions with different elastic moduli are used, then measurement precision is improved by reducing motion noise, but manufacturing precision requirements increase
Solution Approach 1:
The light-transmitting layer is segmented into distinct regions with different elastic moduli. This segmentation can be achieved through manufacturing techniques such as using different materials for different regions or creating structural variations (e.g., solid vs. mesh patterns). The clear regional division simplifies the control of elastic modulus distribution during manufacturing.
Solution Approach 2:
The light-transmitting layer employs composite material structures with different elastic moduli in different regions. By selecting appropriate materials or material configurations (such as varying the density or composition of the polymer matrix), the desired elastic modulus distribution can be achieved while maintaining manufacturability and consistency.
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 effectively reduces noise and improves the accuracy of bio-information acquisition by minimizing the impact of skin motions on the sensor's performance, leading to more reliable biosignal detection.
Implementation Method 1
a first polarizer configured to linearly polarize the light emitted from the light source
Implementation Method 2
a second polarizer configured to block the linearly polarized light passing through the first polarizer when a polarization direction of the second polarizer is different from a polarization direction of the linearly polarized light passing through the first polarizer
Data Source
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AI summary
A biosignal sensor includes a light sensor, a first polarizer configured to linearly polarize incident light emitted, and a second polarizer configured to linearly polarize light flowing into the light sensor. The biosignal sensor may include a light source that may emit light in a first direction and at least partially overlaps the first polarizer in the first direction, the light sensor at least partially overlapping the second polarizer in the first direction.