Combined Transmissive Reflective PPG Vital Sign Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vital sign measurement technologies, particularly contact and remote photoplethysmography (PPG) systems, face challenges in achieving high signal-to-noise ratio and accuracy due to motion artifacts and ambient light disturbances, especially in critical healthcare situations where pulsatility is weak.
Innovation Solution
A system and method that combines transmissive and reflective PPG modes using a single detector, such as a camera, to measure reflected and transmitted light simultaneously, employing complementary wavelengths like green and red for reflection and infrared for transmission to enhance accuracy and robustness of vital sign measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact PPG devices are used to measure vital signs, then measurement accuracy can be maintained, but the devices become obtrusive and limit freedom of movement
Solution Approach 1:
The patent replaces contact-based mechanical PPG sensors with a camera-based optical system that captures reflected light from the subject's skin. This substitution eliminates the need for physical contact and cables, providing unobtrusive monitoring while maintaining measurement capability through optical detection of blood volume changes
Solution Approach 2:
The patent introduces ambient light as an intermediary medium to enable PPG measurements without direct contact. By using environmentally available light sources instead of dedicated illumination, the system achieves contactless measurement while reducing device complexity and improving ease of operation
2Ease of operation
If remote PPG devices are used for unobtrusive measurements, then freedom of movement is improved, but signal-to-noise ratio decreases
Solution Approach 1:
The patent makes the detection unit versatile by enabling it to process both reflected light (for remote PPG) and transmitted light (for contactless transmissive PPG) through the same camera sensor. This multi-functionality allows the system to adapt to different measurement scenarios and optimize signal quality based on conditions
Solution Approach 2:
The patent combines multiple light measurement approaches (reflected and transmitted light detection) into a unified system. By integrating different optical measurement modalities, the system compensates for the weaknesses of individual approaches and achieves improved signal-to-noise ratio while maintaining unobtrusive operation
3Reliability
If forehead sensors are used for PPG measurement, then robustness to centralization effect is improved, but positioning accuracy and measurement reliability depend heavily on correct sensor placement and pressure
Solution Approach 1:
The patent replaces contact-based forehead sensors with a camera-based optical system that detects PPG signals from reflected ambient light. This eliminates the need for precise mechanical positioning and pressure application, as the camera can capture signals from any distance within its field of view, greatly improving ease of operation
Solution Approach 2:
The system uses ambient light that is already present in the environment, eliminating the need for dedicated illumination devices. The camera automatically captures and processes the light reflected from the subject's skin, making the system self-sufficient and reducing device complexity
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 improves the accuracy and robustness of vital sign measurements by leveraging the advantages of both transmissive and reflective modes, reducing artifacts from motion and ambient light, and providing reliable data even in challenging conditions.
Implementation Method 1
a first light source (22) for illuminating a region of interest (26) with light in a first wavelength range to obtain reflected light from said region of interest (26)
Implementation Method 2
a second light source (24) for transmitting light through at least part of the region of interest (26) in a second wavelength range to obtain transmitted light
Implementation Method 3
a detection unit (30) for detecting light portions at different wavelength ranges
Implementation Method 4
PPG is based on the principle that blood absorbs light more than surrounding tissue, so variations in blood volume with every heartbeat affect transmission or reflectance correspondingly
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a device, system and method for determining vital signs of a subject. To improve accuracy and reliability, the device comprising a detection unit (30) for contactless detection of light in at least two different wavelength ranges from a region of interest of a subject, wherein said detection unit (30) is configured to detect a first light portion in a first wavelength range from light reflected from said region of interest in response to illumination by a first light source (22) and to detect a second light portion in a second wavelength range from light transmitted through said region interest in response to illumination by a second light source (24), wherein said detection unit (30) is configured to detect said first light portion and said second light portion simultaneously in response to illuminations that are at least temporarily simultaneous and wherein said first wavelength range and said second wavelength range are different. A processing unit (32) is provided for deriving plethysmography, PPG, signals from the detected light for said at least two different wavelength ranges. An analysis unit (34) is provided for deriving a desired vital sign from the PPG signals for at least two different wavelength ranges.