Part Defect Detection Using Polarized Light and Color Channels
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Solution Overview
Problem
Existing image acquisition systems for detecting defects and unwanted materials on parts are hindered by glare caused by reflections, especially in closed environments, leading to imprecise detection.
Innovation Solution
A device and method using polarized light sources and filters, combined with image processing, to distinguish between materials based on their light repolarization properties, and a colored background to eliminate glare, allowing precise identification of defects and unwanted materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarized light source and polarized filter are used to eliminate glare, then detection precision is improved, but the system cannot correctly detect dark colored parts or materials that do not repolarize light as they appear black against the black background
Solution Approach 1:
The patent divides the detection process into two distinct channels: a first channel (e.g., red wavelength) for detecting the shape and position of the part against the background, and a second channel (e.g., green wavelength) for detecting defects and unwanted materials. This segmentation allows each channel to be optimized for its specific detection task, solving the contradiction between glare elimination and dark part visibility.
Solution Approach 2:
The patent introduces a colored background surface (first color in first wavelength, second color in second wavelength) as an intermediary element that provides contrast for dark parts in the first channel while allowing the polarized filter to eliminate glare in the second channel. This intermediary enables both detection goals to be achieved simultaneously.
2Measurement precision
If front illumination is used to accentuate defects, then detection sensitivity is improved, but glare from surface reflections increases and hinders surface analysis
Solution Approach 1:
The patent changes the polarization parameter of the light source and filter to eliminate glare while maintaining defect visibility. By using polarized light at specific angles with a corresponding polarized filter, the system can distinguish between specular reflections (glare) and diffuse reflections from defects, resolving the contradiction between defect accentuation and glare reduction.
Solution Approach 2:
The patent employs multiple light sources with different polarization orientations that can be activated in sequence or combination. This periodic or alternating illumination strategy allows the system to capture multiple images with different glare characteristics and process them to extract defect information while eliminating glare artifacts.
3Object-affected harmful factors
If a black background surface is used to absorb light and prevent polarization changes, then glare is eliminated, but dark colored parts become indistinguishable from the background
Solution Approach 1:
The patent segments the background into different colored regions that respond differently to polarized light at different wavelengths. The colored background provides contrast for dark parts in the first channel while the polarized filter eliminates glare in the second channel, allowing both goals to be achieved simultaneously through channel-specific optimization.
Solution Approach 2:
The patent adds a spectral dimension to the background by using different colors (wavelengths) for different regions or aspects of the background. This dimensional change allows the background to serve multiple functions: providing contrast in one wavelength range while eliminating glare in another wavelength range through polarization.
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 solution enables precise detection of defects and unwanted materials on parts by eliminating glare, ensuring accurate differentiation and identification without interference from reflections.
Implementation Method 1
the optic of the at least one camera comprises a linearly polarized light polarizer
Implementation Method 2
this glare disappears from the images (since the reflection is not aligned with the filter of the camera or cameras)
Implementation Method 3
the background surface has a color corresponding to the first wavelength... said surface would thereby absorb all the light it receives, preventing the polarization of the light from changing
Data Source
AI summary
The present invention relates to a device for determining the presence of defects in a part and/or of unwanted materials adhered to the surface of the part. The present invention also relates to a method for determining the defects and/or unwanted materials adhered to the part, the method being carried out by the device.