Method and portable apparatus for recognizing barcodes

• US 8,596,540 B2
• Filed: 01/11/2010
• Issued: 12/03/2013
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Scandit AG
• Original Assignee: ETH Zurich
• Inventors: Adelmann, Robert
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): Habib, Asifa
• Application Number:
  US13/144,354
• Publication Number:
  US 20110297748A1
• Time in Patent Office: 1,422 Days
• Field of Search: 235/462.25, 235/462.01
• 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
• CPC Class Codes: G06K 7/1491 the method including a reconstruction step, e.g. stitching two pieces of bar code together to derive the full bar code

Abstract

A method for optical recording of a linear barcode pattern and determination of a symbol sequence as defined by the barcode pattern from a blurred raw image and includes the following steps: taking a raw image of the barcode pattern, preprocessing the raw image to generate a series of output patterns, comparing the output pattern with stored reference patterns, wherein the reference patterns correspond to blurred images of sharp nominal patterns and each reference pattern is provided with at least one symbol, determining for each of the output patterns the reference pattern which most closely resembles the output pattern outputting, transmitting or storing the symbols corresponding to the determined reference pattern and following the sequence of output patterns, as a symbol sequence.

Claims

1. A method for the optical detection of a linear barcode pattern and for determining a symbol sequence which is coded by the linear barcode pattern, wherein the method proceeds from a blurred raw picture and comprises the following steps:

taking a raw picture of the linear barcode pattern;

pre-processing the raw picture of the linear barcode pattern for producing a single output linear barcode pattern or a sequence of output linear barcode patterns, wherein each output linear barcode pattern corresponds to a brightness course along the linear barcode pattern and division of the complete output linear barcode pattern into sequence of output linear barcode patterns;

comparing the output linear barcode patterns or the single output linear barcode pattern with stored reference linear barcode patterns of linear barcode patterns, wherein the reference linear barcode patterns in each case correspond to a brightness course and division of the complete output linear barcode pattern into sequence of output linear barcode patterns of blurred images of non-blurred nominal linear barcode patterns, and at least one symbol is assigned to each reference linear barcode pattern;

determining, for the single output linear barcode pattern or for each of the sequence of output linear barcode patterns, in each case the reference linear barcode pattern which has the greatest similarity to the output linear barcode pattern;

outputting, transmitting or storing the symbols which correspond to the determined linear barcode reference patterns, according to the single output linear barcode pattern or the sequence of output linear barcode patterns, as a symbol sequence.

2. The method according to claim 1, wherein the step of pre-processing comprises at least the step:

producing a brightness course along the linear barcode pattern by way of selection of a picture of the raw picture or by way of averaging over several picture lines of the raw picture.

3. The method of according to claim 1, wherein the step of the pre-processing comprises at least the step:

producing the brightness course along the linear barcode pattern by way of carrying out a Hough transformation on the raw picture or a section of the raw picture, by which means a frequency distribution arises in an imaging plane spanned by angle and distance, and extraction of the brightness course according to the sequence of values on a straight line in the imaging plane, which leads through the maxima in the imaging plane and corresponds to a constant angle.

4. The method according to claim 1, wherein several stored reference linear barcode patterns in each case for different imaging parameters are present for each of the nominal linear barcode patterns;

and with the comparison of the output linear barcode patterns with stored reference linear barcode patterns, one uses a set of those reference linear barcode patterns which corresponds to an estimation of these imaging parameters.

5. The method according to claim 4, wherein the different imaging parameters correspond to different object distances.

6. The method according to claim 5, wherein an estimation of the object distance or a selection of the applied set of reference linear barcode patterns is effected by way of a measure for the blurredness of the raw picture.

7. The method according to claim 6, wherein the measure for the blurredness of the raw picture is a maximum of the brightness gradient at black-white transitions in the raw picture or in the output linear barcode patterns.

8. The method according to claim 1, wherein the reference linear barcode patterns in each case are assigned to a reference symbol and to at least one neighbouring symbol, and wherein with the comparison of a sequence of output linear barcode patterns with the reference linear barcode patterns, not only is a correct assignment of an output linear barcode pattern to a reference linear barcode pattern and thus also to a reference symbol required, but also at least one neighbouring symbol must agree with the reference symbol corresponding to a neighbouring output linear barcode pattern.

9. The method according to claim 7, wherein with the comparison of a sequence of output linear barcode patterns, after a first output linear barcode pattern has been assigned to a reference symbol, for a neighbouring output linear barcode pattern, the set of the reference linear barcode patterns which are available for selection is limited to those reference linear barcode patterns, whose assigned neighbouring symbol is equal to the reference symbol corresponding to the first output linear barcode pattern.

10. The method according to claim 1, wherein the steps from taking the raw picture to determining the recognised symbol sequence is repeated several times until a predefined number of results agree with one another.

11. The method according to claim 1, further comprising the step that symbol sequences to be recognised and corresponding reference linear barcode patterns, at a sales location, are transmitted in a wireless manner to a portable apparatus, and the portable apparatus carries out the method according to one of the preceding steps.

12. A portable apparatus for the optical detection of a linear barcode pattern and for determining a symbol sequence which is coded by the linear barcode pattern, comprising a camera and a data processing unit, wherein the data processing unit is programmed for carrying out the method according to claim 1.

13. A non-transitory machine readable medium encoded with program code that causes a data processing unit to carry out the method for the optical detection of a linear barcode pattern and for determining a symbol sequence, which is coded by the barcode pattern, according to claim 1.