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

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Lucera, Mark, Ralph, Joseph
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US10/045,605
• Publication Number:
  US 20030052172A1
• Time in Patent Office: 1,068 Days
• Field of Search: 235/462, 235/472, 235/461-1-4, 235/472-1-4, 235/454, 235/455, 235/434
• US Class Current: 235/462.25
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G07G 1/0054 with control of supplementary check-parameters, e.g. weight or number of articles

Abstract

A laser scanning system including a multi-path scan data signal processor having multiple signal processing paths. Each signal processing path processes the same data signal (which is derived from the output of a photodetector) to detect bar code symbols therein and generate data representing the bar code symbols. And each signal processing path has different operational characteristics (such as low-pass filter cutoff frequencies, amplifier gain characteristics, and/or positive and negative signal thresholds). The varying operational characteristics of the signal processing paths are optimized to provide different signal processing functions (e.g., minimize paper noise, or maximize the scan resolution of the system). The data signal derived from laser scanning is supplied to each path of the multi-path scan data processor, where it is processed (preferably in parallel) to identify signal level transitions therein. A digital scan data signal that encodes such signal level transitions is provided to digitizing circuitry, which converts the digital scan data signal into a corresponding sequence of digital words (i.e., a sequence of digital count values) suitable for bar code symbol decoding.

Claims

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.

2. A laser scanning system comprising:

a photodetector for detecting the intensity of a light beam reflected and/or scattered off a bar code symbol 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 paths,

wherein each said signal processing path includes circuitry for processing said analog scan data signal generated from said photodetector so as 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 performs low pass filtering, and

wherein the cut-off frequency of said low pass filtering for one of the respective signal processing paths is different than the cut-off frequency of said low pass filtering for another of the respective signal processing paths.

3. A laser scanning system comprising:

a photodetector for detecting the intensity of a light beam reflected and/or scattered off a bar code symbol 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 paths,

wherein each said signal processing path includes circuitry for processing said analog scan data signal generated from said photodetector so as 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;

wherein each said signal processing path performs voltage amplification, and

wherein gain of said voltage amplification for one the respective signal processing paths is different than gain of said voltage amplification for another of the respective signal processing paths.

4. A laser scanning system comprising:

a photodetector for the intensity of a light beam reflected and/or scattered off a bar code symbol 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 paths,

wherein each said signal processing path includes circuitry for processing said analog scan data signal generated from said photodetector so as 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 signals level 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 zero crossing circuitry that indentifies zero crossings in a second derivative signal, derived from said analog scan data signal, and data gate logic that gates said zero crossings to output only those zero crossings that occur substantially concurrent with a peak in a first derivative signal derived from said analog scan data signal.

5. A laser scanning system comprising;

a photodetector for detecting the intensity of a light beam reflected and/or scattered off a bar code symbol 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 paths,

wherein each said signal processing path includes circuitry for processing said analog scan data signal generated from said photodetector so as 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 level 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 is performed concurrently using digital signal processing circuitry; and

wherein each said signal processing path is performed sequentially based on real-time status of a working buffer that stores data values for processing.