Method and apparatus for providing illumination compensation in a document scanner
US5278674A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 1992 |
| Grant date | Jan 11, 1994 |
| Priority date | — |
| Expiry date | Dec 14, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40056
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A document scanner is disclosed wherein means are provided to dynamically compensate for any changes in document illumination intensity that may occur as a document is scanned. The compensation method and apparatus operates to measure the intensity of light that is reflected from a target area that borders an edge of the document being scanned. The target area is a narrow, elongated, area that extends in the scan direction. The target area is of a color to approximate the document's background area, i.e. the document's nonimage area. Since the target area is of a continuous and uniform color tone, any variation in the quantity of light that is reflected from the target area is caused by a variation in the intensity of illumination thereof by the scanning light source. The method and apparatus of the invention controls the scanning light source so as to maintain the light reflected from the target area at a substantially constant magnitude.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.