Image defect inspection method, image defect inspection apparatus, and appearance inspection apparatus
US7346207B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 8, 2005 |
| Grant date | Mar 18, 2008 |
| Priority date | — |
| Expiry date | Aug 28, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30148
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
In an image defect inspection method and apparatus which detects a gray level difference between corresponding portions of two images, automatically sets a threshold value based on the distribution thereof, compares the gray level difference with the threshold value, and judges one or the other of the portions to be defective if the gray level difference is larger than the threshold value, provisions are made to correct the threshold value when the distribution of the gray level difference is different from the usual distribution, thereby achieving high detection sensitivity while suppressing the occurrence of false defects. To achieve this object, the cumulative frequency of the gray level difference is computed (S3); a converted cumulative frequency is computed by converting the cumulative frequency so that the cumulative frequency shows a linear relationship with respect to the gray level difference when the gray level difference is assumed to exhibit a distribution that obeys a prescribed type of distribution (S4); an approximation curve of the converted cumulative frequency is derived (S11); the second derivative of the approximation curve with respect to the gray level differ…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.