Bar code reader configured to read fine print bar code symbols

• US 6,655,595 B1
• Filed: 03/06/2001
• Issued: 12/02/2003
• 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:
  US09/799,896
• Time in Patent Office: 1,001 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. An imaging device comprising a controller and an imaging assembly in communication with said controller, said device being adapted to:

capture a first grey scale image map corresponding to a scene;

define a region of interest within said image map comprising a subset of pixels of said first grey scale image map;

interpolate 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

binarize 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 binary 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 device of claim 1, wherein said device establishes said region of interest to correspond to an aiming pattern of said device.

3. The device of claim 1, wherein said device is further adapted to adjust at least one of a size, a shape, or a position of said region interest.

4. The device of claim 1, wherein said device is further adapted to read 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 device of claim 1, wherein said device is further adapted, when interpolating pixel values, to average pixel values from said initial image map which border positions of said constructed pixel values.

6. The device of claim 1, wherein said device is further adapted to locate a symbology indicator, and define said region of interest about said indicator.

7. The device of claim 1, wherein said device is further adapted to compare pixel values in said binarized interpolated image map to a threshold within a grey scale range.

8. The device of claim 1, wherein said device is further adapted to adjust said region of interest in response to sensed features of said first grey scale image map.

9. The device of claim 1, wherein said device is further adapted to ascertaining whether an entire symbol is contained within said region of interest, and expand said region of interest if an entire symbol is not contained within said region of interest.

10. The device of claim 1, wherein said device is further adapted to, when defining said region of interest, sense a feature of said first grey scale image map, and establish said region of interest based on said sensed feature of said first grey scale image map.

11. The device of claim 1, wherein said device is further adapted to sense transitions of said first grey scale image map.

12. The device of claim 1, wherein said device is further adapted to attempt to decode decodable image data represented in said binary image map.

13. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map.

14. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said imaging device defines an initial region of interest at a center of said grey scale image map.

15. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said imaging device defines an initial region of interest at a center of said grey scale image map, and wherein said imaging device is adapted to adjust a position of said region of interest in response to processing Of image data.

16. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said imaging device defines an initial region of interest at a center of said grey scale image map, and wherein said imaging device is adapted to expand said region of interest if while analyzing image data, said imaging device determines that an entire symbol representation is not included in a present region of interest.

17. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein a dimension of said region of interest is predetermined.

18. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein a size of said region of interest is predetermined.

19. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device establishes said region of interest to correspond to an aiming pattern of said device.

20. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to adjust at least one of a size, a shape, or a position of said region interest.

21. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to read a region of interest menu symbol to adjust at least one of a size, a shape, or a position of said region of interest.

22. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said imaging device is further adapted to define a region of interest by measuring a number of transitions in an area of said first grey scale image map.

23. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted, when interpolating pixel values, to average pixel values from said initial image map which border positions of said constructed pixel values.

24. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to locate a symbology indicator, and define said region of interest about said indicator.

25. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to compare pixel values in said binarized interpolated image map to a threshold within a grey scale range.

26. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to adjust said region of interest in response to sensed features of said first grey scale image map.

27. The device of claim 25, wherein said device is further adapted to ascertain whether an entire symbol is contained within said region of interest, and expand said region of interest if an entire symbol is not contained within said region of interest.

28. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to, when defining said region of interest, sense a feature of said first grey scale image map, and establish said region of interest based on said sensed feature of said first grey scale image map.

29. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to sense transitions of said first grey scale image map.

30. The imaging device of claim 1, further including a hand held housing encasing said imaging assembly and further being adapted to attempt to decode a bar code symbol within said binarized interpolated image map, wherein said device is further adapted to attempt to decode decodable image data represented in said binary image map.

31. A method for processing image data using an imaging device, said method comprising the steps of:

capturing a first multipixel image representation corresponding to a scene, wherein each pixel value of said multipixel image representation comprises at least two data bits;

utilizing a subset of pixel values of said first multipixel image representation, interpolating constructed pixel values from existing pixel values of said multipixel image representation to form an interpolated multipixel image representation, wherein each pixel value of said interpolated multipixel image representation comprises at least two data bits; and

binarizing pixel values of said interpolated multipixel image representation to form a binarized interpolated image representation, each pixel value of said interpolated multipixel image representation comprising one data bit having either a logic “

1”

value or a logic “

0”

value, wherein said binarized interpolated multipixel image representation comprises a greater number of pixel values per unit scene area than said first multipixel image representation.

32. The method of claim 31, wherein at least one pixel value of said first multipixel image representation comprises a grey scale pixel value.

33. The method of claim 31, wherein said subset of pixel values utilized for interpolating constructed pixel values is selected to correspond to an aiming pattern of said imaging device.

34. The method of claim 31, further comprising the step of adjusting said subset of pixel values utilized for interpolating constructed pixel values.

35. The method of claim 31, wherein said interpolating step includes the step of detecting for a symbology indicia representation in said first image representation and selecting said subset of interpolated constructed pixel valued based on a location of said symbology indicator representation.

36. The method of claim 31, wherein said interpolating step includes the step of ascertaining whether an entire symbol is representation by pixels of said subset of pixels, and expanding said subset of pixels if an entire symbol is not represented by said subset of pixels.

37. The method of claim 31, wherein said interpolating step includes the step of selecting said subset of pixels based on an analysis of said first multipixel image representation.

38. The method of claim 31, further comprising the step of attempting to decode a decodable symbol represented in said binarized interpolated multipixel image representation.