Method for locating and reading a two-dimensional barcode

• US 6,565,003 B1
• Filed: 06/02/2000
• Issued: 05/20/2003
• Est. Priority Date: 12/16/1998
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ma, Yue
• Primary Examiner(s): Lee, Diane I.
• Application Number:
  US09/586,299
• Time in Patent Office: 1,082 Days
• Field of Search: 235/462.08, 235/462.1, 235/462.11, 235/437, 235/438, 235/456, 235/460, 235/494, 382/237, 382/270, 382/281, 382/289
• US Class Current: 235/462.1
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• 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 7/1417 2D bar codes
• CPC Class Codes: G06K 7/1443 locating of the code in an image
• CPC Class Codes: G06K 7/1456 determining the orientation of the optical code with respect to the reader and correcting therefore

Abstract

Two-dimensional barcodes surrounded by a quiet zone of white space which may or may not include a border, each barcode having encoded digital information in a bitmap representing preferably randomized encoded data bits, are printed onto a printed medium. To extract the encoded digital information from the printed medium, the printed medium is scanned, then the bitmap is located within the printed medium by moving a window, in stepwise fashion in a predetermined pattern across the printed medium. At each step the portion of the printed medium which is encompassed by the window is tested to determine whether it conforms to one or more characteristics of the bitmap. The skew of the bitmap, if any, is determined, by using a finite-state recognizer in combination with a Hough Transform calculation. In one embodiment, the candidate region is divided into a plurality of horizontal regions, preliminary skew angles are calculated for each region, and the actual skew angle is selected using a voting scheme. Once the skew angle is calculated, the bitmap is deskewed if necessary, cropped, and the randomized digital information is read from the bitmap. Finally, the digital information is derandomized and any error correction codes are removed, in the process correcting and/or recording any errors discovered, thereby reproducing the original encoded digital information.

Claims

1. A method of locating a two-dimensional barcode within a scanned binary image comprising:

(A) moving a window across said image in stepwise fashion in a predetermined pattern;

(B) testing at each step a portion of said image which is encompassed by said window to determine whether said portion of said image conforms to one or more characteristics of said two-dimensional barcode;

(C) cropping said portion of said image which is encompassed by said window and comparing dimensions of said cropped portion to predetermined dimensions when said portion of said image does conform to said one or more characteristics of said two-dimensional barcode;

(D) moving said window to avoid said cropped portion when said dimensions of said cropped portion do not conform to said predetermined dimensions; and

(E) setting boundaries of said two-dimensional barcode within said scanned binary image as the boundaries of said window when said portion of said image does conform to said one or more characteristics of said two-dimensional barcode and when said dimensions of said cropped portion conform to said predetermined dimensions.

2. The method of claim 1, wherein said moving step comprises the steps of:

(1) identifying the location of an object within said window;

(2) comparing the distance between a left edge of said window and a left edge of said object;

(3) moving said window to a next normal position when the distance between a left edge of said window and a left edge of said object is greater than a predetermined dimension; and

(4) moving said window such that said left edge is beyond a right edge of said object when the distance between the left edge of said window and the left edge of said object is less than or equal to a predetermined dimension.

3. A method of locating a two-dimensional barcode within a scanned binary image comprising the steps of:

(A) moving a window across said image in stepwise fashion in a predetermined pattern;

(B) testing at each step a portion of said image which is encompassed by said window to determine whether said portion of said image conforms to one or more characteristics of said two-dimensional barcode;

(C) cropping, prior to setting the boundaries of said two-dimensional barcode within said scanned binary image, said portion of said image which is encompassed by said window and comparing dimensions of said cropped portion to predetermined dimensions when said portion of said image does conform to said one or more characteristics of said two-dimensional barcode;

(D) setting boundaries of said digitized bitmap two-dimensional barcode as the boundaries of said window when said dimensions of said cropped portion conform to said predetermined dimensions;

(E) identifying and storing in memory the location of an object within said window when said dimensions of said cropped portion do not conform to said predetermined dimensions;

(F) prior to performing said testing step at each subsequent window position, determining whether said object falls within the boundaries of said window; and

(G) skipping said testing step and said cropping step whenever said object falls within the boundaries of said window.