Optical Filter Layout for Motion-Resistant Biometric Sensing
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Solution Overview
Problem
Existing biometric measurement devices struggle to accurately acquire biological information such as pulse wave data due to contamination from body motion information, particularly when using typical color filters and non-contact methods that are susceptible to environmental light, leading to inaccurate separation of pulse and motion signals.
Innovation Solution
A biometric measurement device employing a bandpass filter that suppresses transmission of light in the 550-600 nm range, combined with optical detection elements for red, green, and blue light, allows for accurate separation of biological information by comparing signals from different wavelength ranges to effectively remove body motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical color filter is used to detect reflected light for non-contact biometric measurement, then the device can acquire biological information such as pulse wave data, but the detected signal is contaminated with body motion information making accurate separation difficult
Solution Approach 1:
The patent segments the detected signal into distinct components by using multiple wavelength bands. The green light signal (500-560nm) contains both pulse information and body motion information, while the red light signal (600-700nm) contains primarily body motion information. By processing these segmented signals separately and then combining them, the system can extract pure pulse information through signal processing that removes the body motion component.
Solution Approach 2:
The patent extracts the body motion information component from the green light signal by using the red light signal as a reference. Since the red light signal contains predominantly body motion information, it can be used to isolate and remove this component from the green light signal, leaving only the pulse information.
2Ease of operation
If non-contact light detection method is used for biometric measurement, then the device can measure pulse waves without contact, but the measurement is highly susceptible to environmental light and body motion artifacts
Solution Approach 1:
The patent applies local quality by using different wavelength bands with different characteristics for different purposes. The green light band (500-560nm) is optimized for detecting pulse information due to hemoglobin absorption characteristics, while the red light band (600-700nm) is optimized for detecting body motion information. This local optimization of wavelength selection improves both ease of operation and reliability.
Solution Approach 2:
The patent introduces the red light signal as an intermediary that mediates between the green light signal and the body motion artifacts. The red light signal serves as a reference that allows the system to identify and remove body motion components from the green light signal, thereby improving measurement reliability while maintaining non-contact operation.
3Quantity of substance
If green light signal is used for pulse detection, then the signal contains large amount of pulse information, but it also contains significant body motion information that interferes with accurate measurement
Solution Approach 1:
The patent exploits the asymmetry in the composition of signals from different wavelength bands. The green light signal has a specific composition (high pulse information + high body motion information), while the red light signal has a different composition (low pulse information + high body motion information). This asymmetric relationship allows the system to mathematically separate the components and extract pure pulse information.
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 achieves more precise acquisition of biological information by minimizing the mixing of body motion information with pulse information, thereby enhancing the accuracy of pulse wave detection and other biological metrics.
Implementation Method 1
a bandpass filter that suppresses transmission of light in a wavelength range greater than or equal to 550 nm and less than or equal to 600 nm
Implementation Method 2
a method for acquiring biological information such as pulse wave information on the basis of reflected light generated by irradiating a living body with light
Data Source
AI summary
A biometric measurement device includes a bandpass filter, an optical detection device, and a processing circuit, the optical detection device includes a first filter configured to transmit red light, a second filter configured to transmit one of green light and blue light, a first optical detection element detecting light from a living body through the first filter, and a second optical detection element detecting the light through the second filter, the processing circuit generates biological information of the living body based on first light detected by the first optical detection element and second light detected by the second optical detection element, and the bandpass filter suppresses transmission of at least a part of light in a wavelength range greater than or equal to 550 nm and less than or equal to 600 nm included in light from the living body incident on the first optical detection element.