Dual-Pixel Imaging System for Heart Rate Signal Separation
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Solution Overview
Problem
Existing non-contact video-based methods for measuring physiological status, such as heart rate and blood volume pulse, face challenges in accurately separating heart rate components from illumination variation components, especially under varying lighting conditions, due to overlapping signal distributions in traditional RGB filter-based systems.
Innovation Solution
The biological information measurement apparatus employs a dual-pixel imaging system with a first pixel sensitive in the 530 nm to 590 nm wavelength band and a second pixel with sensitivity on both shorter and longer wavelength sides of this range, generating separate time series signals to apply independent component analysis for precise separation of heart rate and illumination variation components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RGB filter-based systems are used for non-contact video-based measurement, then the device complexity is reduced and ease of manufacture is improved, but the measurement precision deteriorates due to overlapping signal distributions that prevent accurate separation of heart rate components from illumination variation components
Solution Approach 1:
The imaging device divides the pixel array into multiple pixel groups, where each group is assigned a different spectral sensitivity characteristic. This segmentation allows simultaneous capture of multiple wavelength bands across the image plane, enabling separation of heart rate and illumination components without requiring complex per-pixel filtering structures.
Solution Approach 2:
Different regions of the image plane are equipped with pixels having different spectral sensitivity characteristics tailored to local measurement needs. This local differentiation enables optimized signal separation in different spatial zones while maintaining overall system simplicity.
2Measurement precision
If multiple wavelength bands are captured simultaneously to improve heart rate detection accuracy, then the measurement precision is improved, but the device complexity increases due to the need for complex spectral filtering structures in each pixel
Solution Approach 1:
Instead of equipping each pixel with complex multi-band filtering structures, the system segments the pixel array into groups with different spectral sensitivities. This approach captures multiple wavelength bands simultaneously across the image plane while keeping individual pixel structures simple.
Solution Approach 2:
The imaging device uses standard image sensor pixels that can be assigned different spectral sensitivity characteristics through the imaging device's optical path design rather than requiring specialized multi-functional pixels. This universal approach simplifies pixel fabrication while achieving multi-wavelength capability.
3Reliability
If conventional RGB color channels are used for signal separation, then the ease of operation is maintained, but the reliability deteriorates under varying lighting conditions due to overlapping signal distributions between color channels
Solution Approach 1:
The system segments the captured image signal into multiple spectral components corresponding to different pixel groups. This segmentation provides distinct spectral signatures for heart rate and illumination variations, enabling more reliable separation than conventional RGB channels especially under varying lighting conditions.
Solution Approach 2:
The system changes the spectral parameter basis from conventional RGB color space to a customized spectral sensitivity space defined by the pixel groups. This parameter transformation optimizes the separation of physiological signals from illumination artifacts, improving reliability under diverse lighting 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
This approach allows for accurate and stable detection of heart rate and other biological information, robust against illumination variations, by effectively separating heart rate and illumination components with high accuracy, enhancing the reliability of non-contact physiological status measurement.
Implementation Method 1
a plurality of first pixels where each first pixel includes a sensitivity range in a hemoglobin absorption wavelength band and is configured to generate a first imaging signal based on received light
Implementation Method 2
a plurality of second pixels where each second pixel includes a longer wavelength-side sensitivity range on a longer wavelength side of the sensitivity range of the first pixel and a shorter wavelength-side sensitivity range on a shorter wavelength side of the sensitivity range of the first pixel
Data Source
AI summary
A biological information measurement apparatus includes: a plurality of first pixels configured to generate a first imaging signal based on received light; a plurality of second pixels configured to generate a second imaging signal based on the received light; a time series signal generation unit configured to generate a first time series signal by connecting representative values of first imaging signals in time series and generate a second time series signal by connecting representative values of second imaging signals in time series; a signal component separation unit configured to separate a plurality of signal components from each of the first and second time series signals; and a biological information component selector configured to select a signal component in accordance with the biological information, among the plurality of signal components separated by the signal component separation unit.