Apparatus and method for increasing the scan accuracy and quality of the flatbed scanner by using close loop control
US6178015A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 5, 1998 |
| Grant date | Jan 23, 2001 |
| Priority date | — |
| Expiry date | Jun 5, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2201/04794
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical ruler is provided on the back surface side of the top housing and close to the transparent window along a scanning direction for providing a calibration reference. The optical ruler is formed with black and white blocks alternately arranged in an array. An image sensor which has a width larger than the width of the transparent window is provided for reading the image information of the optical ruler along with a scanned sheet while being progressively driven by a step motor. A determining element computes the actual moving steps of the step motor by calculating the number of black and white pixels from the scanned image of the optical ruler. When the actual moving steps of the step motor are fewer than a predetermined threshold value, or when the frequency of the occurrences of the scan line losses is higher than a predetermined threshold value, the image sensor is driven by the step motor to scan the sheet again. As a result, the step motor can be operated in response to a closed loop control signal depending on the actual moving steps of the step motor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.