Optical inspection system utilizing dynamic analog-to-digital thresholding
US5377282A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 19, 1991 |
| Grant date | Dec 27, 1994 |
| Priority date | — |
| Expiry date | Sep 19, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/403
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical imaging surface inspection system and method are provided. The system comprises an illumination source for illuminating an image pattern on a surface to be inspected, a video camera for detecting a portion of the light reflected from the surface and outputting an analog video signal, a dynamic thresholding circuit for converting the analog video signal into a digital representation of the image pattern, and means to compare a known accurate digital representation of the image pattern to the digital representation provided by the dynamic thresholding circuit. The method includes the steps of illuminating the surface, scanning the surface with the video camera, separating the video signal into a black level signal component and a white level signal component, detecting successive peak levels in the white level signal component and outputting a corresponding variable peak voltage. A variable threshold voltage is determined by selecting a percentage of the variable peak voltage. This variable threshold voltage is then compared with a delayed portion of the analog video signal to provide the digital representation of an image pattern on the surface being inspected.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.