Yarn Quality Evaluation Using RGB to L*a*b* Color Space Transformation
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Solution Overview
Problem
Existing methods for assessing the quality of longitudinally moving yarns, such as EP 1143236 B1 and WO2007/012936 A2, fail to reliably detect dark impurities like black or brown fibers and diameter deviations, as they only evaluate color intensity without considering brightness, leading to inaccurate identification of defects.
Innovation Solution
A method using polychromatic light to detect the red, green, and blue color components of reflected light, transforming these into a color space that separates color from brightness, allowing for the evaluation of all three coordinates (color and brightness) to distinguish foreign substances and diameter deviations, enabling the detection of dark impurities and thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only color intensity is evaluated without brightness, then colored foreign fibers can be detected, but dark impurities like black or brown fibers cannot be reliably detected
Solution Approach 1:
The patent transitions from evaluating only color intensity (2D color space) to evaluating both color and brightness (3D color space with L* coordinate). This dimensional expansion allows the system to detect dark impurities by monitoring brightness changes, while still maintaining the ability to detect colored fibers through color coordinate analysis.
Solution Approach 2:
The patent changes the evaluation parameters from solely color intensity to include both color coordinates (a*, b*) and brightness coordinate (L*). This parameter expansion enables the detection system to distinguish between colored foreign fibers (affecting color coordinates) and dark impurities (affecting brightness coordinate), resolving the detection reliability issue.
2Measurement precision
If only color coordinates are used for evaluation, then diameter effects and variations can be compensated, but thick or thin areas cannot be detected
Solution Approach 1:
The patent adds the brightness dimension (L* coordinate) to the existing color evaluation system. Since brightness is affected by both color and diameter variations, while color coordinates are primarily affected by foreign substances, the combination of all three coordinates enables simultaneous detection of both colored impurities and diameter deviations.
Solution Approach 2:
The patent creates a composite evaluation approach by combining color coordinates (a*, b*) and brightness coordinate (L*) into a unified 3D color space assessment. This composite evaluation method leverages the different sensitivities of each coordinate to various defect types, enabling comprehensive quality assessment.
3Ease of operation
If brightness is eliminated from evaluation, then the perception of the sensor aligns better with human eye for color detection, but dark foreign materials cannot be detected
Solution Approach 1:
The patent modifies the evaluation parameters by including all three coordinates (L*, a*, b*) rather than eliminating brightness. This allows the system to maintain human-perception-aligned color evaluation while adding the capability to detect dark impurities through brightness monitoring, achieving both goals simultaneously.
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 allows for reliable detection of colored and dark foreign fibers, as well as diameter deviations, by considering the brightness coordinate, which remains unaffected by colored fibers but changes with dark impurities, and thickness, improving the accuracy of defect identification in yarn quality assessment.
Implementation Method 1
The material is exposed to polychromatic, preferably white, light. A measurement signal representing the red, green and blue color components of the light reflected by the object is acquired.
Data Source
Figure 3
AI summary
The present invention relates to a method for assessing the quality of a longitudinally moving strand-shaped material (1), in particular a yarn, comprising the steps of illuminating the material (1) with polychromatic, preferably white, light; acquiring a measurement signal representing the red, green, and blue color components (aR, bG, cB) of the light reflected by the material; and transforming the red, green, and blue color components (aR, bG, cB) into an evaluation color space in which measurement points (M) of the measurement signal are described by a first (a*) and a second (b*) coordinate representing the color, and by a third coordinate (L*) representing the brightness. According to the invention, the quality of the material (1) is assessed based on the first (a*), second (b*), and third (L*) coordinates of the measurement points (M) in the evaluation color space. The present invention also relates to an apparatus for carrying out the method.