Registers – Coded record sensors – Particular sensor structure
Patent
1995-10-23
1999-09-07
Le, Thien Minh
Registers
Coded record sensors
Particular sensor structure
23546201, 23546226, 23546206, 23546227, G06K 710
Patent
active
059490543
ABSTRACT:
A bar code reader is provided which can read bar code symbols of varying contrast, from high to medium to low contrast. The bar code reader includes a digitizing circuit which digitizes an analog signal representing the reflectance function of a scanned bar code by comparing the analog signal to a threshold signal. In the present invention, the threshold signal is switchable between a first state wherein the threshold signal is a standard threshold signal suitable for digitizing analog signals representing medium to high contrast bar code symbols and a second state wherein the threshold signal is a non-standard threshold signal suitable for digitizing analog signals representing low contrast bar code symbols. In one embodiment of the invention, the threshold signal is manually adjustable. In another embodiment, a bar code reader is provided which automatically digitizes and decodes bar code symbols of varying contrast by repetitively scanning bar code symbols, using first and second alternating threshold signal states to digitize the analog signal resulting from each scan.
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Havens William H.
Jovanovski Brian L.
Karpen Thomas W.
McEnery Dennis W.
Le Thien Minh
Rodriguez Douglas X.
Welch Allyn Inc.
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