Symbology scanning system for efficiently locating coded symbologies

• US 6,508,404 B2
• Filed: 12/18/2001
• Issued: 01/21/2003
• Est. Priority Date: 03/07/1997
• Status: Expired due to Fees

• Current Assignee: Accu-Sort Systems Incorporated (Datalogic S.p.A.)
• Original Assignee: Accu-Sort Systems Incorporated (Datalogic S.p.A.)
• Inventors: Hecht, Kurt
• Primary Examiner(s): TREMBLAY, MARK STEPHEN
• Application Number:
  US10/024,409
• Publication Number:
  US 20020139851A1
• Time in Patent Office: 399 Days
• Field of Search: 235/462.08, 235/462.07, 235/462.16, 235/462.18, 235/462.19
• US Class Current: 235/462.08
• 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: G06K 7/1443 locating of the code in an image

Abstract

A scanner for optically scanning coded symbologies including a signal processing unit for pre-processing the scanned symbology information and a hardware symbology locating unit. An analog signal related to the reflectivity of the different portions of the coded symbology is obtained and is converted to digital gray-scale. The portion of the analog signal which corresponds to the substrate reflectance (absolute contrast) is removed, and the available dynamic range of the analog to digital converter is used only for the information-bearing portion of the signal (relative contrast). Since all of the decodable information is ultimately encoded in binary form, the information-bearing portion of the signal is retained. The hardware symbology locating unit includes a plurality of shift registers, each of which derives a value from an input seed which is based upon the width of a detected coded symbology element. The value of a subsequent input seed is compared to the values generated from a prior input seed. Based upon this comparison, the unit determines whether the size of a subsequent symbology element is a ratio match of a prior symbology element. The presence of a potential coded symbology candidate is likely when a plurality of ratio matches are detected.

Claims

1. A device for locating a bar code symbology on a presented surface, the device having a light source for illuminating the surface;

a detector for generating a light intensity signal that corresponds to transitions in reflected light from the surface; and

a processor for processing the light intensity signal to identify the potential location of the bar code symbology;

the processor comprising;

a signal generator for generating, from the light intensity signal, a series of counts which identify transitions in the light intensity;

a locator for determining a location of each of the counts;

a separator for separating the series of counts into alternating odd and even counts;

a multiplier for simultaneously multiplying each of the separated counts by a plurality of predetermined values to simultaneously generate a corresponding plurality of odd and even comparison values;

a comparator for comparing said plurality of odd comparison values to a subsequent odd count, and said even comparison values to a subsequent even count, determining whether a comparison is a valid match and outputting a valid match indicator for each valid odd/even match; and

a combiner for receiving the comparator outputs and, upon detection of consecutive odd/even comparator outputs, generating a potential bar code match indicator;

whereby the likelihood of the existence of the bar code symbology at a certain location increases with an increasing frequency of potential bar code match indicators.

2. The bar code locating device of claim 1 further comprising an encoder, and whereby said potential bar code match indicator comprises an encoded value corresponding to the width and type of a bar code symbology element.

3. The bar code locating device of claim 1 wherein said plurality of predetermined values comprise ¼

, ⅓

, {fraction (1/2.5)}, ½

, 2, 2.5, 3 and 4.

4. The bar code locating device of claim 1 wherein higher intensities correspond to areas of higher reflectivity and lower intensities correspond to areas of lower reflectivity.

5. The bar code locating device of claim 4 wherein areas of higher reflectivity correspond to spaces and areas of lower reflectivity correspond to bars.

6. The bar code locating device of claim 1 wherein said comparator determines a positive odd and even match when said compared values are within a predetermined tolerance from each other.

7. The bar code locating device of claim 6 wherein said tolerance is dynamically adjusted for each comparison value.