Image reader with adjustable contrast range
US5329111A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 26, 1992 |
| Grant date | Jul 12, 1994 |
| Priority date | — |
| Expiry date | Jun 26, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N23/76
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An image input device photoelectrically reads a document and outputs digital data. This image reader includes a first voltage generating circuit for generating a first voltage for setting an upper limit of contrast, a second voltage generating circuit for generating a second voltage for setting a lower limit of contrast, and an A/D converter for converting an input analog signal to a digital signal in accordance with the first and second voltages. At least one of the voltages generated by the first voltage generating circuit and second voltage generating circuit is variable. Also disclosed is an image reader including a dark voltage memory circuit, storing dark voltages corresponding to color signals R, G and B, a first switching circuit sequentially switching the output of the dark voltage memory circuit and outputting a selected dark voltage, a second switching circuit adapted to synchronously output a selected color signal corresponding to the selected dark voltage, and a differential amplifier subtracting the selected dark voltage from said selected color signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.