Vision-System Color Filter Generation for Accurate RGB-to-XYZ Mapping
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Solution Overview
Problem
Existing digital camera systems do not accurately replicate human color perception due to non-linear mapping between their spectral sensitivities and human visual system matching functions, leading to inaccuracies in color reproduction, especially for saturated colors, and existing solutions are either complex, expensive, or require additional image capture steps.
Innovation Solution
A method and system for generating a color filter that modifies the spectral response of a vision system by solving a bilinear optimization problem to determine a color correction matrix and filter parameters, using Alternating Least-Squares (ALS) optimization to create a filter that transforms RGB signals to XYZ color space, ensuring the camera's spectral sensitivities are a linear combination of human visual system matching functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a linear correction transform is applied to map RGB to XYZ, then color correction is simple and fast, but color accuracy fails for saturated colors
Solution Approach 1:
The patent applies a color filter to the camera sensor before image capture to pre-modify the spectral sensitivities. This preliminary action ensures that the RGB signals captured are already closer to human visual perception, making subsequent linear color correction more effective and accurate, especially for saturated colors that fail with standard linear correction alone.
Solution Approach 2:
The patent changes the spectral parameters of the camera system by introducing a color filter with specific transmittance characteristics. This modifies the spectral sensitivities of the RGB channels to better match human visual system matching functions, thereby improving color accuracy while maintaining linear correction simplicity.
2Measurement precision
If multispectral or hyperspectral camera systems are used to increase measurement dimensionality, then color accuracy improves, but system complexity and cost increase significantly
Solution Approach 1:
The patent introduces a color filter as an intermediary component between the light source and the camera sensor. This filter modifies the spectral content of incoming light to match human visual perception characteristics, enabling accurate color measurement using a standard three-channel RGB camera without requiring complex multispectral or hyperspectral systems.
Solution Approach 2:
The patent creates a simplified copy of the human visual system's spectral response characteristics using a color filter. Instead of implementing the full complexity of human vision or multispectral imaging, the filter reproduces the essential spectral sensitivity patterns needed for accurate color perception using only three RGB channels.
3Measurement precision
If two pictures are captured with and without a colored filter to increase dimensionality, then color prediction accuracy improves, but capture time increases and image registration becomes more difficult
Solution Approach 1:
The patent applies the color filter during the initial image capture process rather than requiring a separate capture step. This preliminary application of the filter allows the RGB image to directly encode color information in a way that is closer to human perception, eliminating the need for a second capture with and without the filter and thus avoiding registration problems and increased capture time.
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 proposed filter significantly improves color accuracy in digital cameras, making them almost colorimetric, with a Vora-Value improvement from 0.950 to 0.992 and NRMSE reduction from 0.250 to 0.052, allowing them to capture colors closer to human perception without increasing complexity or cost.
Implementation Method 1
A method and system for generating a color filter that modifies the spectral response of a vision system
Data Source
AI summary
A system and method for generating a colour filter for modifying the spectral response of a vision system are disclosed. The method includes receiving an RGB spectral response of the vision system for a colour target under predetermined illumination and executing, by a processor of a computer system, computer program instructions configured to apply the RGB spectral response to a bilinear optimisation problem that simultaneously determines: i) a colour correction matrix to transform the RGB spectral response to XYZ colour space; and, ii) parameters of the colour filter. The method further executes computer program instructions configured solving the bilinear optimisation problem; and then provides the parameters or causes a colour filter to be formed using the parameters.