Document reading apparatus employing two subsequent samplings of the light source to insure stability of the light intensity level before scanning occurs
US5530239A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 13, 1994 |
| Grant date | Jun 25, 1996 |
| Priority date | — |
| Expiry date | Oct 13, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40056
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A document reading apparatus includes a reference member used for determining the reference gray scale of an image on a document; a fluorescent lamp for illuminating the reference member; an image sensor for receiving light from the fluorescent lamp via the reference member and for converting the received light into an electric signal; a circuit for obtaining the difference between the latest data corresponding to a specified pixel among the output of the image sensor and the data before a predetermined period corresponding to the specified pixel among the output of the image sensor; and a circuit for determining whether or not the read operation of the document should be started by comparing the difference and a predetermined value.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.