Browse Prior Art Database

Locating and Determining the Tilt of a Barcode in a Camera's Field of View

IP.com Disclosure Number: IPCOM000112929D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 105K

Publishing Venue

IBM

Related People

Kishi, GT: AUTHOR

Abstract

Disclosed is a method to find a barcode and its tilt in a camera's field of view.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 49% of the total text.

Locating and Determining the Tilt of a Barcode in a Camera's Field
of View

      Disclosed is a method to find a barcode and its tilt in a
camera's field of view.

      This article describes a method to find a barcode in a field of
view of a camera.  In addition, this method determines the tilt of
the barcode.  For the purposes of this article, the barcode is
assumed to be approximately vertical in the field of view, but this
method is applicable to a horizontal barcode, or to any bar- code
orientation if the analysis is performed approximately perpendicular
to the barcode.  The description of the method is separated into two
parts.

o   SEARCH LOCATIONS - the locations used to scan for the barcode and
    the techniques used to measure the tilt of the barcode are
    described.

o   BARCODE FINDER - the function(s) used to determine the location
    of the barcode for a specific search location are described.

      A section of a typical barcode label is shown below - where :
denotes the edge of the label, B is black, w is white, and everything
else is any shade of grey.  Note that the barcode is tilted in the
field of view.

     :     Bwwwwwwwwwww:
     :     BBBBBBBBBBBB:
     :     Bwwwwwwwwwww:
      :     BBBBBBBBBBBB:
      :     BBBBBBBBBBBB:           <-Search 1
      :     BBBBBBBBBBBB:
       :     Bwwwwwwwwwww:
       :     BBBBBBBBBBBB:
       :     Bwwwwwwwwwww:
        :     Bwwwwwwwwwww:         <-Search 2
        :     Bwwwwwwwwwww:
        :     BBBBBBBBBBBB:
         :     Bwwwwwwwwwww:
         :     BBBBBBBBBBBB:
         :     Bwwwwwwwwwww:        <-Search 3
          :     BBBBBBBBBBBB:
          :     BBBBBBBBBBBB:
          :     BBBBBBBBBBBB:
           :     Bwwwwwwwwwww:

o   SEARCH LOCATIONS

      Assuming the field of view of the camera is aimed at the
nominal center of the set of barcode labels being viewed, three
horizontal search heights are defined (more can be used depending on
the expected vertical shift of the window).  In the system used in
this method, three search heights are all that are required - they
are located so that all three cross the barcode when it is in its
nominal position.  For any label that is high and still fully in the
camera's field of view, at least Search 1 and Search 2 still cross
the label.  For any label that is low and still fully in the camera's
field of view, at least Search 2 and Search 3 still cross the label.

    -   All three levels are searched using the barcode finder.  A
        minimum threshold is defined that indicates a significant
        difference in barcode finding "quality".  The following rules
        are applied.

    -   If Search 2 is not significantly higher th...