Automatic offset and gain control in a document scanner
US5331428A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 6, 1993 |
| Grant date | Jul 19, 1994 |
| Priority date | — |
| Expiry date | Apr 6, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/4076
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An automatic offset and gain control method for use in an electronic high quality scanning apparatus, operating on the source signal values outputted preferably in digitized form when the scanning apparatus scans a given source document and which represent on a pixel-related basis the density values of such source segment, produces corrected signal values representative of the full range of black and white or colors of the original. In the control method, first, a minimum density value relative to the source document is determined. Then, a high density value and a low density value are identified by reference to calibrated high and low density values and from these three values the control unit calculates and stores in a memory corrections for offset and gain. These corrections are applied to the source values to continuously correct the same and thus reproduce a corrected version of the source document.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.