Facial Skin Patch Illumination for Accurate In-Vehicle rPPG
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Solution Overview
Problem
The accuracy of remote photoplethysmography (rPPG) for determining heartbeat characteristics in vehicles is compromised by unpredictable and variable light conditions, including changing environmental lighting and internal vehicle light sources.
Innovation Solution
A method and system that identify and illuminate specific skin patches on a user's face using configurable light sources, optimizing light parameters to enhance rPPG accuracy by capturing and processing image frames with remote photo-plethysmography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rPPG is performed in vehicle environments with variable light conditions, then noncontact monitoring is enabled, but measurement precision deteriorates due to unpredictable lighting changes
Solution Approach 1:
The system performs preliminary actions by capturing a first set of image frames to identify suitable skin patches before the actual rPPG measurement. This preliminary identification allows the system to select optimal measurement locations that are less susceptible to lighting variations, thereby improving measurement precision while maintaining noncontact operation.
Solution Approach 2:
The patent applies local quality by focusing the light source specifically on identified skin patches rather than illuminating the entire face. This localized illumination approach ensures that only the most suitable areas for rPPG measurement are subjected to controlled lighting, reducing the impact of variable ambient light conditions and improving measurement precision.
2Measurement precision
If light sources are added to illuminate skin patches, then measurement precision improves, but device complexity increases
Solution Approach 1:
The light source is designed with multi-functionality, serving both as an illumination device for rPPG measurement and as a component that can be controlled based on identified skin patch locations. This universal approach allows the same hardware component to perform multiple functions, improving measurement precision without proportionally increasing device complexity.
Solution Approach 2:
The system dynamically adjusts the light source configuration based on the identified skin patch locations. The light source parameters (position, intensity, direction) are adaptively modified to match the identified optimal measurement areas, allowing the system to maintain high measurement precision while using a relatively simple light source component.
3Measurement precision
If skin patches are identified and selectively illuminated, then measurement precision improves, but difficulty of detecting and measuring increases
Solution Approach 1:
The system uses a simplified representation or copy of the facial structure and skin patch locations to guide the light source positioning. By creating a digital model or mapping of the face based on the first image frames, the system can accurately identify and select skin patches without requiring complex real-time analysis during the measurement process, thereby reducing the difficulty of detection and measurement.
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
Improves rPPG accuracy by reducing the impact of fluctuating light conditions, enabling precise determination of heartbeat parameters for applications like in-vehicle driving assistance.
Implementation Method 1
determining a light source configuration and transmitting the light source configuration to a first light source; illuminating, by the first light source, the at least one skin patch according to the light source configuration
Implementation Method 2
capturing a second set of image frames, wherein the second set of image frames includes a representation of the at least one skin patch illuminated by the first light source
Implementation Method 3
processing one or more of the second set of image frames using remote photo-plethysmography, rPPG
Data Source
AI summary
The disclosure relates to a method including: capturing a first set of image frames, wherein the first set of image frames includes a representation of a user's face; identifying at least one skin patch of the user's face that is represented in the first set of frames; determining a light source configuration and transmitting the light source configuration to a first light source; illuminating, by the first light source, the at least one skin patch according to the light source configuration; capturing a second set of image frames, wherein the second set of image frames includes a representation of the at least one skin patch illuminated by the first light source according to the light source configuration; and processing one or more of the second set of image frames using remote photo-plethysmography, rPPG. The disclosure also relates to a system configured to perform the method.