Bar code reader configured to read fine print barcode symbols

• US 6,264,105 B1
• Filed: 11/05/1998
• Issued: 07/24/2001
• Est. Priority Date: 11/05/1998
• Status: Expired due to Fees

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Welch Allyn Incorporated
• Inventors: Longacre, Andrew Jr., Hussey, Robert M.
• Primary Examiner(s): Frech, Karl D.
• Application Number:
  US09/187,722
• Time in Patent Office: 992 Days
• Field of Search: 235/462.1, 235/462.11, 235/462.12, 235/462.24, 235/462.25, 235/462.08, 235/462.09
• US Class Current: 235/462.1
• CPC Class Codes: G06F 18/28 Determining representative reference patterns, e.g. by averaging or distorting; Generating dictionaries
• 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 7/1469 using sub-pixel interpolation
• CPC Class Codes: G06V 10/25 Determination of region of interest [ROI] or a volume of interest [VOI]

Abstract

In the present invention, a bar code reader captures an initial image map corresponding to a scene, then subjects the initial image map to an interpolation step wherein values for constructed pixels positionally intermediate pixel values of the initial image map are interpolated as a function of the initial image map pixel values bordering the constructed pixels. After an interpolated image map is constructed, the interpolated image map is subjected to a binarization step wherein grey scale pixel values of the interpolated image map are converted into binary (1 or 0) pixel values by way of a thresholding process. In the thresholding process, grey scale pixel values are compared to a threshold in the grey scale range, then set to 1 if they are above the threshold and set to 0 if below the threshold. The pixel values of the resulting binarized interpolated image map are then analyzed to determine the identity of a message which may be encoded in any symbol which may be represented in the binarized interpolated image map.

Claims

1. A method for processing image data with use of an optical reader, said method comprising the steps of:

capturing a first gray scale image map corresponding to a scene including a symbol;

defining a region of interest within said image map comprising a subset of pixels of said first image map;

interpolating constructed pixel values only from those pixel values corresponding to pixel locations within said region of interest to form an interpolated image map within said region of interest; and

binarizing said interpolated image map to form a binarized interpolated image map so that a region of said scene corresponding to said region of interest is represented by a binarized image map comprising a greater number of pixel values per unit scene area than is represented by said first grey scale image map.

2. The method of claim 1, wherein said method further comprises the step of defining a region of interest, and wherein said interpolating step includes the step of interpolating constructed pixel values only from those pixel values within said region of interest.

3. The method of claim 2, further comprising the step of adjusting at least one of a size, a shape, or a position of said region of interest.

4. The method of claim 2, further comprising the step of reading a region of interest menu symbol to adjust at least one of a size, a shape, or a position of said region of interest.

5. The method of claim 1, wherein said interpolating step includes the step of interpolating values for said constructed pixel values by averaging pixel values from said initial image map which border positions of said constructed pixel values.

6. The method of claim 1, wherein said defining step includes the step of locating a symbology indicator, and defining said region of interest about said dicator.

7. The method of claim 1, wherein said binarization step includes the step of comparing pixel values in said binarized interpolated image map to a threshold within a grey scale range.

8. The method of claim 1, wherein said method further comprises the step of adjusting said region of interest in response to sensed features of said first grey scale image map.

9. The method of claim 8, wherein said method further includes the step, after said determining step of ascertaining whether an entire symbol is contained within said region of interest, and expanding said region of interest if an entire symbol is not contained within said region of interest.

10. The method of claim 1, wherein said defining step comprises the steps of sensing a feature of said first grey scale image map, and establishing said region of interest based on said sensed feature of said first grey scale image map.

11. The method of claim 10, wherein said sensing step includes the step of sensing transitions of said first grey scale image map.

12. A method for processing image data with use of an optical reader, said method of comprising the steps of:

capturing an first grey scale image map corresponding to a scene including a symbol;

binarizing said grey scale image map to form a binarized image map;

analyzing said binarized image map to determine a location of a symbology indicator;

establishing a region of interest about said located symbology indicator;

interpolating constructed pixel values from existing pixel values in said first grey scale image map within said region of interest to form an interpolated image map; and

binarizing said interpolated image map to form a binarized interpolated image map within said region of interest.

13. The method of claim 12, wherein said analyzing step includes the step of searching for a bullseye of a symbol.

14. The method claim 12, wherein said interpolating step includes the step of interpolating values for said constructed pixel values by averaging pixel values from said first image map which border constructed pixel positions of said constructed pixel values.

15. A method for processing image data using an optical reader, said method comprising the steps of:

capturing a first grey scale image map;

identifying pixel positions of said first grey scale image map that correspond to a symbol representation;

selectively interpolating constructed pixel values only from pixel values of said identified pixel positions of said image map that correspond to said symbol representation, said identified pixel positions comprising less than all pixels of said first grey scale image map; and

binarizing said constructed pixel values.

16. The method of claim 15, wherein said identifying step includes the steps of binarizing pixel values of said first grey scale image map to form a binarized image map, and finding a symbology indicator representation utilizing said binarized image map.

17. The method of claim 15, wherein said identifying step includes the step of finding a symbology indicator representation.

18. The method of claim 15, wherein said identifying step includes the step of finding a symbology indicator representation, and defining a region of interest about said symbology indicator representation.

19. The method of claim 15, further comprising the step of analyzing said binarized constructed pixel values to determine a message encoded in said symbol representation.