Hardness Tester Indentation Area Extraction via Pattern Matching
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Solution Overview
Problem
Conventional hardness testers face challenges in accurately extracting indentation areas due to changes in luminance and contamination, especially for small indentation areas, as they rely on binarization which can be affected by these factors.
Innovation Solution
A hardness tester that includes an indentation former, image capture controller, and a pattern matcher which reduces images at various scale ratios and performs pattern matching using a scanning model to extract indentation areas without binarization, allowing for accurate extraction regardless of luminance changes or contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If binarization is used to extract indentation area, then processing speed is improved, but measurement precision deteriorates due to luminance changes and contamination
Solution Approach 1:
The patent changes the parameter of image processing method from binarization to pattern matching with correlation calculation. This allows the system to maintain high processing speed while achieving accurate indentation area extraction that is not affected by luminance changes or contamination, as pattern matching compares actual image patterns against reference patterns rather than relying on threshold-based binarization
Solution Approach 2:
The patent uses template copying where a reference indentation pattern is created and copied across the image for comparison. This template matching approach allows the system to identify indentation areas by comparing against known patterns, maintaining speed while improving accuracy over binarization methods
2Device complexity
If binarization with threshold value is used, then device complexity is reduced, but reliability deteriorates in cases of small indentation areas or contamination
Solution Approach 1:
The patent changes the processing parameter from simple threshold-based binarization to correlation-based pattern matching. While this increases algorithmic complexity, it dramatically improves reliability by making the extraction process immune to luminance variations and contamination, especially for small indentation areas where binarization fails
3Measurement precision
If pattern matching with multiple scale ratios is used, then measurement precision is improved, but productivity decreases due to increased processing time
Solution Approach 1:
The patent applies preliminary action by first reducing the image to a smaller scale before performing pattern matching. This preliminary reduction step allows the system to achieve accurate indentation area extraction with improved processing efficiency, as the pattern matching operates on a computationally lighter reduced image while maintaining measurement precision
Data Source
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AI summary
A hardness tester has an indentation former forming an indentation by pressing an indenter against a surface of a sample; an image capture controller controlling a CCD camera to capture an image of the surface of the sample and obtain image data; an indentation area extractor extracting an indentation area based on the obtained image data; and a hardness calculator calculating hardness of the sample based on the extracted indentation area. The indentation area extractor has a reduced image generator reducing the image obtained from the image data of the surface of the sample at a scale ratio selected from a plurality of predetermined scale ratios and generating a reduced image; and a pattern matcher performing pattern matching with respect to the generated reduced image and extracting the indentation area.