Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1997-06-20
1999-10-19
Lee, John R.
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
25055936, G01N 2186
Patent
active
059693711
ABSTRACT:
A system and method for sensing a leading edge of a document in an imaging scanner includes detecting a shadow adjacent the leading edge, the shadow being cast as a result of the edge being exposed to a light source. Light is reflected off of a white drive roller support surface for the document and is sensed by a photo sensor array. As the document is processed through the scanner, the leading edge is exposed to the light such that the leading edge casts a shadow onto the drive roller. The shadow is sensed by the photo sensor array which sends a signal to a microprocessor for computing whether a threshold amount of shadow has been detected for initiating image scanning of the document. Prior to the medium being exposed to the light, a contrast sensitivity level of the photo sensor array is increased, relative to a normal level, for detecting the shadow. Upon detecting the threshold amount of shadow, the contrast sensitivity level is returned to its normal level for continuing with normal image processing of the document.
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Andersen Eric L.
Cox Darrell L.
Shabazz Rhasool
Hewlett--Packard Company
Lee John R.
Simmons Lane R.
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