Metal Surface Inspection via Multi-Wavelength Signal Analysis
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Solution Overview
Problem
Existing surface inspection methods for metal materials struggle to accurately detect surface defects, particularly those with non-linear shapes and those that do not exhibit apparent unevenness, due to interference from harmless patterns and scales.
Innovation Solution
A surface inspection method that optically detects surface defects by irradiating the metal material with light, capturing reflected light in multiple wavelength bands, and analyzing the relative signal intensity between these images to identify defects, potentially utilizing machine learning for enhanced discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single wavelength light is used for surface inspection, then the inspection process is simple, but harmless patterns and scales are erroneously detected as surface defects
Solution Approach 1:
The inspection process is segmented into multiple wavelength bands, with each band capturing different characteristics of the surface. By dividing the spectral range into multiple segments (e.g., blue, green, red, near-infrared bands), the system can analyze different optical properties simultaneously, allowing discrimination between defects and harmless patterns based on their distinct spectral signatures
Solution Approach 2:
The inspection method changes the optical parameter being measured by using multiple wavelength bands. Different materials (defects vs. scales) have different reflectance characteristics across wavelengths. By varying the wavelength parameter and comparing reflectance ratios across multiple bands, the system can identify surface defects with high accuracy while filtering out false positives
2Measurement precision
If multiple wavelength bands are used for surface inspection, then surface defect detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The imaging device is designed with multi-functionality to capture images across multiple wavelength bands simultaneously or sequentially. By integrating multiple spectral sensing capabilities into a single inspection system, the device can perform comprehensive surface analysis without requiring separate inspection systems for each wavelength, thereby managing complexity while maintaining high detection accuracy
3Ease of operation
If simple image combination methods are used, then the processing is easy, but it is difficult to discriminate between scales, harmless patterns, and surface defects
Solution Approach 1:
The method transforms the inspection approach by using spectral ratio analysis instead of simple image combination. By calculating reflectance ratios between different wavelength bands, the system creates new diagnostic parameters that enhance the contrast between defects and harmless patterns. This parameter transformation maintains computational simplicity while dramatically improving discrimination accuracy
Solution Approach 2:
The patent introduces an intermediary processing step that calculates reflectance ratios as intermediate values before final defect identification. This intermediary calculation layer acts as a mediator that translates raw multi-wavelength image data into enhanced contrast images, making the subsequent defect discrimination process easier and more accurate
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 method enables complete and accurate detection of surface defects on metal materials, reducing false positives and ensuring high-quality materials free from surface imperfections.
Implementation Method 1
irradiating a surface of the metal material with light; obtaining a plurality of images by capturing reflected light from the surface of the metal material by the light emitted in the irradiating step
Data Source
AI summary
A surface inspection method for a metal material according to the present invention is a surface inspection method for material in which a surface defect of the metal material is optically detected, the method including: an irradiating step of irradiating a surface of the metal material with light; an image capturing step of obtaining a plurality of images by capturing reflected light from the surface of the metal material by the light emitted in the irradiating step in two or more different wavelength bands; and a detecting step of detecting a surface defect present on the surface of the metal material from information of a relative signal intensity between the plurality of images obtained from a same position on the surface of the metal material in the image capturing step.