Autodiscrimination and line drawing techniques for code readers

• US 6,405,925 B2
• Filed: 03/16/2001
• Issued: 06/18/2002
• Est. Priority Date: 06/12/1998
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Cai, Joseph, He, Duanfeng, Joseph, Eugene
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): FRANKLIN, JAMARA ALZAIDA
• Application Number:
  US09/809,216
• Publication Number:
  US 20010025886A1
• Time in Patent Office: 459 Days
• Field of Search: 235/462-1-4
• US Class Current: 235/462.25
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

Optical image readers have a two-dimensional image sensor and an auto-discrimination function. The auto-discrimination function identifies optical codes by type for pixel clusters and, in some cases, tilt angle and start/stop coordinates. The clustered pixel data is passed to an appropriate decoder identified by the auto-discrimination function based upon a likelihood that the cluster contains an optical code of a particular type. Line drawing technique provide for adequate sampling of the clustered pixel data code based on the tilt angle of the code relative to an image sensor array.

Claims

1. A method for reading an optical code comprising the steps of:

obtaining pixel data;

dividing said pixel data into sub-images;

evaluating at least one non-binarized statistic associated with each sub-image;

grouping together sub-images having similar statistics into a cluster; and

processing pixel data associated with said cluster to read said optical code.

2. The method of claim 1, wherein said at least one statistic is one of black level, white level and threshold level.

3. A method for sampling an optical code comprising the steps of:

estimating a tilt angle of said optical code relative to an axis associated with optical sensing elements;

using a first line drawing selection technique for sampling said optical code if said tilt angle is less than a predetermined angle; and

using a second line drawing selection technique for sampling said optical code if said tilt angle is greater than said predetermined angle.

4. The method of claim 3, wherein said predetermined angle is about 18 degrees.

5. The method of claim 3, wherein said second selection technique results in selection of a greater percentage of pixels neighboring an ideal scanning line than said first selection technique.

6. A method for reading an optical code comprising the steps of:

obtaining non-binarized pixel data;

dividing said non-binarized pixel data into non-binarized sub-images;

evaluating at least one statistic associated with each non-binarized sub-image;

grouping together non-binarized sub-images having similar statistics into a cluster; and

processing pixel data associated with said cluster to read said optical code.

7. A method for sampling an optical code comprising the steps of:

estimating a tilt angle of said optical code relative to an axis associated with optical sensing elements;

using a thin line drawing selection technique for sampling said optical code if said tilt angle is less than a predetermined angle; and

using a thick line drawing selection technique for sampling said optical code if said tilt angle is greater than said predetermined angle.