Method and apparatus for synchronizing the polarization control signal of an AC-polarized arc-discharge lamp with the exposure timing signals of a CCD line sensor
AssigneeAgfa Division, Bayer Corporation
InventorMarc L. Cresens
Life of this patent
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Abstract
A method and apparatus for synchronizing the line time and color channel exposure timing signals of a CCD line sensor with the polarization control signal of an AC-polarized arc-discharge lamp in a scanning system. The scanning system comprises a scanner illumination system, including an AC-polarized arc-discharge lamp, for illuminating a document to be scanned, and a scanner imaging system for scanning the illuminated document in a line-wise manner. The scanning system of the present invention is designed to minimize brightness fluctuations on the document being scanned, improving the quality of the scanned image.
Claims11
In a scanning system including an array of light sensitive sensors and a polarized arc-discharge lamp arrangement for illuminating said array of light sensitive sensors during a plurality of successive scan lines, a method for synchronizing a periodic polarization control signal of said polarized arc-discharge lamp arrangement with an exposure time of said array of light sensitive sensors, comprising the steps of:
- synchronizing a polarity change of the periodic polarization control signal of said polarized arc-discharge lamp arrangement with a start time of each scan line, said polarity change occurring a predetermined time after the start time of each scan line;
- exposing said array of light sensitive sensors for a predetermined length of time during each scan line;
- and
- initiating said exposure step a predetermined time after the start time of each scan line.
A method for scanning an image comprising the steps of:
- illuminating said image with a polarized arc-discharge lamp;
- driving said polarized arc-discharge lamp with a periodic polarization control signal;
- scanning successive lines of said illuminated image with a light sensitive sensor arrangement to provide ..t. digital representation of a series of scan lines each scan line occurring for a first predetermined time T.sub.1 ;
- and
- synchronizing a polarity change of said periodic polarization control signal with a start time of each scan line, said polarity change occurring a predetermined time T.sub.2 after the start of each scan line, wherein T.sub.2 /T.sub.1 remains constant.
Dependencies are inferred from the claim text.