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Multipath scan data signal processor having multiple signal processing paths with different operational characteristics to enable processing of signals having increased dynamic range

  • US 6,830,190 B2
  • Filed: 01/11/2002
  • Issued: 12/14/2004
  • Est. Priority Date: 02/02/1999
  • Status: Expired due to Term
First Claim
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1. A laser scanning system comprising:

  • a photodetector for detecting the intensity of a light beam reflected and/or scattered off a bar code system consisting of bars and spaces of different light reflectivity, and generating an analog scan data signal representative of the detected intensity of the reflected and/or scattered light beam; and

    a scan data signal processor having a plurality of signal processing path, wherein each said signal processing path includes circuitry for processing said analog scan data generated from said photodetector so as a to detect the presence of and transitions in the bars and spaces associated with the bar code symbol scanned by said light beam, and generate a digital scan data signal having first and second signal levels corresponding to the bars and spaces associated with the bar code symbol scanned by said light beam;

    wherein each said signal processing path in said plurality of signal processing paths has different operational characteristics; and

    wherein each said signal processing path includes a peak detector that identifies time periods during which a first derivative signal, derived from said analog scan data signal, exceeds at least one threshold level, wherein the at least one threshold level for one of the respective signal processing paths is different than the at least one threshold level for another of the respective signal processing paths;

    wherein the at least one threshold level for a respective signal processing path is a dynamic threshold that changes as said first derivative signal changes; and

    wherein the dynamic threshold is based upon a DC bias value and a portion of said first derivative signal.

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