Method and apparatus for compensating for illumination variations of a lamp in a document scanning system following extended lamp inactivity
US5153745A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 28, 1990 |
| Grant date | Oct 6, 1992 |
| Priority date | — |
| Expiry date | Sep 28, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40056
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An illumination output from a fluorescent lamp used in a RIS type scanner is maintained at optimum by monitoring the lamp's on/off state and turning the lamp on for a time period following a specified cumulative off time. In one example, the lamp is turned on for a two minute interval following a one hour off time. Following the two minute on period, a diagnostic test is automatically performed to determine whether variations in the lamp output have resulted in an out of specification condition requiring that the lamp be recalibrated to the photosensor array. The calibration is automatically enabled by adjusting the gain of the photosensor array until the photosensor response is within the nominal percentage range. The scanner is then returned to a standby mode. All of the tests are performed automatically and normal operations can be accomplished while the lamp is in warm up phase.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.