Multispectral Skin Imaging Alignment Using Cross-Channel Motion Vectors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for aligning image frames in multi-spectral imaging of human skin are hindered by the spectral variation of skin reflectance, leading to misalignment due to movement during sequential illumination with different wavelengths, which complicates image registration.
Innovation Solution
A method and apparatus that utilize a multi-channel imaging device with separate light detection channels for different spectral bands, calculating motion vectors from one channel to align frames in another, ensuring consistent alignment across frames using multi-spectral light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential multi-spectral illumination is used to capture image frames at different wavelengths, then detailed spectral decomposition of skin chromophores is achieved, but subject movement during the scan causes misalignment between frames
Solution Approach 1:
The patent introduces an intermediary alignment process that uses a reference wavelength frame to establish a common coordinate system for all spectral frames. This mediator frame serves as the basis for registering all other wavelength-specific frames, ensuring they are properly aligned despite subject movement during the sequential scanning process.
Solution Approach 2:
The patent performs preliminary alignment by first capturing a reference frame at a selected wavelength, then using this reference frame to pre-establish the coordinate system before processing and aligning all other spectral frames. This preliminary action ensures that subsequent spectral analysis is performed on properly aligned data.
2Ease of operation
If simple alignment algorithms are used for non-varying illumination, then alignment is easy to implement, but these algorithms fail when images are illuminated by different wavelengths due to spectral variations in skin reflectance
Solution Approach 1:
The patent applies local quality by selecting specific wavelength ranges (e.g., green light around 530-560nm) that provide optimal contrast and feature visibility for alignment purposes. Different wavelength regions are used for different aspects of the imaging process, with the reference wavelength optimized specifically for alignment tasks rather than general imaging.
Solution Approach 2:
The patent changes the parameter of illumination wavelength to create distinct reference frames with varying spectral characteristics. By deliberately using different wavelengths for reference frames compared to other spectral frames, the system exploits spectral variations rather than being hindered by them, enabling robust alignment through wavelength-specific feature detection.
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
Effectively aligns image frames despite spectral variations, enabling accurate spectral analysis of skin properties by maintaining consistent subject positioning across frames.
Implementation Method 1
Reflectance spectroscopy is the study of light as a function of wavelength. It finds many uses in medical applications, material analysis and soil analysis. Reflectance spectroscopy is enabled by the fact that different materials have different absorption and scattering spectra.
Implementation Method 2
different materials have different absorption and scattering spectra. This also holds for the chromophores in the human skin, such as oxygenated and deoxygenated haemoglobin, carotenoids, melanin, bilirubin, etc.
Implementation Method 3
different materials have different absorption and scattering spectra. This also holds for the chromophores in the human skin
Data Source
Figure 1
Figure 2
Figure 3
AI summary
According to an aspect, there is provided a method for aligning image frames in a sequence of image frames of a subject. The method comprises controlling (101) one or more light sources to emit multi-spectral light to illuminate the subject, wherein the multi-spectral light comprises at least a first light component having a first illumination wavelength, and a second light component having a second illumination wavelength; controlling (103) a multi-channel imaging device to obtain two or more sequences of image frames of the subject, wherein each sequence of image frames is obtained using a respective light detection channel of the multi-channel imaging device, wherein the multi-channel imaging device comprises a first light detection channel that is responsive to light in a first spectral band to generate a first sequence of frames of the subject, and a second light detection channel that is responsive to light in a second spectral band to generate respective a second sequence of frames of the subject, wherein the first illumination wavelength is within the first spectral band, and the second illumination wavelength is within the second spectral band; processing (105) the first sequence of frames to calculate motion vectors for each frame, wherein each motion vector represents a movement of the subject between frames in the first sequence; and aligning (107) the frames in the second sequence of frames according to the corresponding determined motion vectors such that the subject is aligned across the frames in the second sequence of frames.