METHOD AND PORTABLE APPARATUS FOR RECOGNIZING BAR CODES

• US 20110297748A1
• Filed: 01/11/2010
• Published: 12/08/2011
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Scandit AG
• Original Assignee: ETH Zurich
• Inventors: Adelmann, Robert
• Granted Patent: US 8,596,540 B2
• Time in Patent Office: Days
• 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 barcode pattern, wherein the method proceeds from a blurred raw picture and comprises the following steps:

taking a raw picture of the barcode pattern;

pre-processing the raw picture for producing a single output pattern or a sequence of output patterns;

comparing the output patterns or the single output pattern with stored reference patterns, wherein the reference patterns in each case correspond to blurred images of non-blurred nominal patterns, and at least one symbol is assigned to each reference pattern;

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

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

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

producing a total output pattern corresponding to a brightness course along the barcode pattern, and division of the complete output pattern into the sequence of output patterns.

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

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

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

producing the brightness course along the 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.

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

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

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

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

8. The method according to claim 7, 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 patterns.

9. The method according to claim 1, wherein the reference 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 patterns with the reference patterns, not only is a correct assignment of an output pattern to a reference 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 pattern.

10. The method according to claim 8, wherein with the comparison of a sequence of output patterns, after a first output pattern has been assigned to a reference symbol, for a neighbouring output pattern, the set of the reference patterns which are available for selection is limited to those reference patterns, whose assigned neighbouring symbol is equal to the reference symbol corresponding to the first output pattern.

11. 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.

12. The method according to claim 1, further comprising the step that symbol sequences to be recognised and corresponding reference 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.

13. A portable apparatus for the optical detection of a linear barcode pattern and for determining a symbol sequence which is coded by the 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.

14. A computer program for the optical detection of a linear barcode pattern and for determining a symbol sequence, which is coded by the barcode pattern, wherein the computer program may be loaded and carried out on a data processing unit (14), and which on implementation, carries out the method according claim 1.