Adjustable read level threshold for optical mark scanning

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United States of America Patent

PATENT NO 5420407
SERIAL NO

08122152

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ATTORNEY / AGENT: (SPONSORED)

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Abstract

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To determine a read level threshold for discriminating those response bubbles on a scannable answer sheet intended to be marked from those response bubbles not intended to be marked, an adjustable read level threshold is dynamically determined based on the read levels of a designated pool of response bubbles. In an optical scanner the darkness (read level) of each response mark entered for a particular question is determined to make a profile. From this profile showing the various read levels present for the response marks, the system determines read level 'gaps,' i.e., read levels in the profile for which there are no marks present, and adjusts the threshold for discriminating intended marks based on the read level(s) comprising the gaps.

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Patent Owner(s)

Patent OwnerAddress
SCANTRON CORPORATION1313 LONE OAK RD EAGAN MN 55121

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Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Grundy, Jr John N Gilbert, AZ 2 40

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