Method of establishing thresholds for image comparison
US5798830A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 27, 1996 |
| Grant date | Aug 25, 1998 |
| Priority date | — |
| Expiry date | Nov 27, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B21/006
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method is described for optimizing intensity-comparison thresholds used to compare test and reference images for defect detection. Intensity differences between corresponding pixels in the two images that exceed a predefined threshold value are deemed defect pixels. According to the method, the pixels of the reference image are grouped according to their respective z values (elevation) to identify different physical layers of the reference surface. Because different surface layers can have different image properties, such as reflectance and image texture, the groups of pixels are analyzed separately to determine an optimal threshold value for each of the groups, and therefore for each layer of the reference surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.