Remote PPG Skin Pixel Block Segmentation for Motion Artefact Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing remote photoplethysmography (PPG) devices face challenges in achieving a high signal-to-noise ratio, particularly in situations with severe motion, challenging environmental illumination, or high accuracy requirements, due to their inherently low signal quality and susceptibility to artefacts from subject movement.
Innovation Solution
The solution involves analyzing the spatial and temporal properties of the skin area to adjust parameters and algorithms for extracting vital sign information, using metrics such as spatial uniformity and temporal consistency to improve signal quality and reduce artefacts, by adapting post-processing methods based on the reliability of skin pixel blocks and their stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If remote PPG devices are used for unobtrusive measurements, then ease of operation and subject comfort are improved, but measurement precision and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent segments the skin area into multiple skin pixel blocks and processes each block independently to extract PPG signals. This segmentation allows the system to identify and weigh reliable blocks while excluding noisy ones, thereby improving measurement precision while maintaining the unobtrusive nature of remote PPG
Solution Approach 2:
The patent dynamically adjusts the weighing factors of different skin pixel blocks based on their temporal stability characteristics. Blocks with higher temporal stability receive higher weights, and this weighting scheme is continuously adapted during measurement, improving signal-to-noise ratio without requiring physical contact with the subject
2Device complexity
If conventional post-processing methods are used, then device complexity is kept low, but reliability of vital sign determination deteriorates in demanding conditions
Solution Approach 1:
The patent performs preliminary analysis of spatial and temporal properties of skin pixel blocks before extracting PPG signals. By pre-evaluating the reliability characteristics of each block and establishing weighting factors in advance, the system prepares optimized processing parameters that improve reliability without requiring complex real-time adjustments during measurement
3Productivity
If skin pixel blocks with low temporal stability are included in analysis, then productivity and signal extraction speed are improved, but measurement precision deteriorates due to increased artefacts
Solution Approach 1:
The patent implements a feedback mechanism where the temporal stability of each skin pixel block is continuously evaluated and used to adjust its weighting factor. Blocks showing low temporal stability automatically receive lower weights, preventing them from degrading the overall measurement precision while allowing the system to process all available pixels for maintained productivity
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 enhances the signal-to-noise ratio and reduces artefacts caused by subject motion, resulting in more accurate and reliable determination of vital signs like heart rate and blood oxygen saturation, even in demanding conditions.
Implementation Method 1
an imaging unit (28), in particular a camera, for remotely detecting electromagnetic radiation (16) reflected from a region of interest (14) including a skin area of the subject (12)
Implementation Method 2
the pulse rate can be determined from a movie at a single wavelength, whereas at least two movies at different wavelengths are required for determining the oxygen saturation... minute light absorption changes in the skin caused by the pulsating blood volume
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to a device and a method for determining a vital sign of a subject. The proposed device comprises an interface (32) for receiving a data stream (26) derived from detected electromagnetic radiation (16) reflected from a region of interest including a skin area of the subject (12), said data stream (26) comprising a data signal per skin pixel area of one or more skin pixels for a plurality of skin pixel areas of said region of interest, a data signal representing the detected electromagnetic radiation (16) reflected from the respective skin pixel area over time, an analyzer (34) for analyzing spatial and/or temporal properties of the skin area, a processor (36) for determining a vital sign information signal of the subject based on the data signals of skin pixel areas within the skin area, and a post-processor (38) for determining the desired vital sign from said vital sign information signal, wherein said determined spatial and/or temporal properties are used by the processor for determining the vital sign information signal and/or by the post-processor for determining the desired vital sign.