Optical reader exposure control apparatus comprising illumination level detection circuitry
US6254003A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 1998 |
| Grant date | Jul 3, 2001 |
| Priority date | — |
| Expiry date | Jun 18, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K7/10851
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An exposure control apparatus for use with optical readers, such as bar code readers, which utilize photosensitive image sensors. An illumination signal generating circuit generates an illumination signal having a magnitude that varies in accordance with the illumination level at the image sensor. A window detecting circuit samples the illumination signal during a predetermined part of each scan to determine whether the illumination signal is within the window, has exited the window, or has re-entered the window. Exposure control circuitry uses the output of the window detecting circuit to control which of a plurality of the subdivisions of the exposure control range of the image sensor will be used. Changes in exposure time are made only between adjacent subdivisions of the exposure control range. Together with a predetermined hysteresis between the exit and re-entry thresholds of the window, the latter changes stabilize the operation of the reader by reducing exposure control "hunting".
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.