Method and system for automatically calibrating a color-based machine vision system
US6016161A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 1, 1998 |
| Grant date | Jan 18, 2000 |
| Priority date | — |
| Expiry date | Apr 1, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N17/002
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A calibration algorithm is provided for calibrating a machine vision system including a color camera, a framegrabber and an illumination source wherein subsequently acquired images are processed on a pixel-by-pixel basis. After framegrabber offsets are measured to obtain initial or offset calibration data, the camera is pointed at a target monotone patch of known reflectance such as pure white and the camera outputs for red, green and blue are determined while observing the monotone patch to obtain spatial calibration data. The gain for each of the output channels of the color camera is automatically determined from the initial calibration data. Applying the three gain factors to a subsequent image on the pixel-by-pixel basis allows one to end up with a color-corrected image without incurring any time performance penalty. At any time during an inspection process, a small area of white reflectance can be observed. The resulting dynamic white calibration data is used to correct for any medium to long term temporal variation in imaging conditions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.