Method for processing images captured with bar code reader having area image sensor

• US 6,814,290 B2
• Filed: 05/12/2003
• Issued: 11/09/2004
• Est. Priority Date: 11/05/1998
• Status: Expired due to Fees

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Longacre, Andrew
• Primary Examiner(s): Frech, Karl D.
• Application Number:
  US10/436,182
• Publication Number:
  US 20030197063A1
• Time in Patent Office: 547 Days
• Field of Search: 235/462.08, 235/462.1, 235/462.11
• 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 operating a bar code reader which captures a gray scale image map, said method including the step of:

(A) detecting a feature of said gray scale image map;

(B) defining a region of interest area about a detected feature detected in step (A);

(C) interpolating constructed pixel values within said region of interest area to develop an interpolated image map; and

(D) binarizing gray scale values of said interpolated image map to generate a binarized image map comprising binarized pixel values.

2. The method of claim 1, wherein said detecting step includes the step of measuring a strength and number of transitions in said gray scale image map.

3. The method of claim 1, wherein said method includes the step of utilizing a portable reader to capture said gray scale image map.

4. The method of claim 1, wherein said method includes the step of utilizing a stationary position reader to generate said gray scale image map.

34. The method of claim 1, wherein said searching step (B) includes the step of searching for a representation of a complete bar code symbol in said region of interest.

35. The method of claim 1, wherein said defining step (A) includes the step of defining said region of interest to be a rectangular arrangement of pixel positions in said M×

N array of pixel values.

36. The method of claim 1, wherein said defining step (A) includes the step of defining a region of interest area at a center of said initially captured frame of image data.

5. A method for operating a bar code reader which captures a frame of image data, said method comprising the steps of:

(A) programming said reader to operate in a low resolution binarization mode and in a high resolution binarization mode, wherein said reader, in said high resolution binarization mode interpolates constructed pixel values corresponding to constructed pixel locations intermediate original pixel locations;

(B) utilizing said low resolution binarization mode when searching said frame of image data to determine if a decodable symbol is represented in said frame; and

(C) driving said bar code reader into a high resolution binarization mode of operation if at step (B) a decodable symbol is determined to be represented in said frame.

6. The method of claim 5, wherein said utilizing step (B) includes the step of searching for a symbol indicator along a scan line.

7. The method of claim 5, wherein said driving step (C) includes the step of defining a region of interest about a position of said frame that includes a representation of a decodable symbol.

8. The method of claim 5, wherein said method includes the step of utilizing a portable reader to capture said frames of image data.

9. The method of claim 5, wherein said method includes the step of utilizing a stationary position reader to capture said frames of image data.

10. A method for operating a bar code reader having an image sensor said method including the steps of:

(A) obtaining a sample or pixel array;

(B) tracking local maxima of a row said array to generate row maximum tracking line data;

(C) tracking local minima of said array to generate a row minimum tracking line data; and

(D) utilizing said row maximum tracking line data and row minimum tracking line data to generate 2D maximum and minimum tracking lines which track, respectively, changes in said row maximum and row minimum tracking line data;

(E) establishing a threshold tracking line between said 2D maximum and minimum tracking lines;

(F) using said threshold tracking line to binarize pixel values in generating a binarized image map including binarized image data; and

(G) searching for a symbol indicator in said binarized image map.

11. The method of claim 10, wherein said searching step (G) includes the step of analyzing a line of pixel values.

12. The method of claim 10, wherein said searching step (G) includes the step of searching for a representation of a symbol bullseye.

13. The method of claim 10, wherein said method includes the step of utilizing a portable reader to obtain said sample or pixel array obtained at step (A).

14. The method of claim 10, wherein said method includes the step of utilizing a stationary position reader to obtain said sample or pixel array obtained at step (A).

15. A method for operating a bar code reader of the type having an area image sensor, said method comprising the steps of:

(A) capturing a gray scale image map;

(B) binarizing pixel values of said gray scale image map to develop a binarized image map while saving said gray scale image map;

(C) searching for a symbol indicator in said binarized image map; and

(D) establishing a region of interest area about a location of located symbol indicator;

(E) utilizing said gray scale image map, interpolating constructed pixel values from pixel values within said region of interest area to develop an interpolated image map; and

(F) binarizing pixel values of said interpolated image map to generate a binarized image map corresponding to said region of interest area.

16. The method of claim 15, wherein said searching step (C) includes the step of searching for a representation of a symbol bullseye.

17. The method of claim 15, wherein said searching step (C) includes the step of launching a scan line.

18. The method of claim 15, further including the step of launching a symbology specific decoding algorithm to decode a decodable symbol represented in said binarized image map generated at step (F).

19. The method of claim 15, wherein said method includes the step of utilizing a portable reader to capture said gray scale image map captured at step (A).

20. The method of claim 15, wherein said method includes the step of utilizing a stationary position reader to capture said gray scale image map captured at step (A).

21. A method for operating an area image sensor bar code reader which captures an image map, said method comprising the steps of:

(A) configuring said reader so that when searching for a symbol indicator in said image map, said reader searches for a symbol indicator within an adjustable region of interest area of said image map which may be adjusted in response to a user input command to adjust at least one of a position, size, or shape of said region of interest area; and

(B) manually inputting a user-input command to said reader to adjust at least one of a position, size or shape of said region of interest area.

22. The method of claim 21, wherein said manually inputting step includes the step of reading a menu symbol.

23. The method of claim 21, wherein said manually inputting step includes the step of actuating a keyboard of a host computer in communication with said reader.

24. The method of claim 21, wherein said method includes the step of inputting said user-input command to adjust said region of interest area when a reading depth of said reader is changed.

25. The method of claim 21, wherein said configuring step includes the step of configuring said reader so that a size of said region of interest area is manually adjustable, and wherein said inputting step includes the step of manually inputting a user-input command to adjust a size of said region of interest area.

26. The method of claim 21, wherein said configuring step includes the step of establishing said region of interest to be a rectangular shaped subset of a full frame image map.

27. A method for operating an area image sensor bar code reader which captures an image map, said method comprising the steps of:

(A) configuring said reader so that when searching for a symbol indicator in said image map, said reader searches for a symbol indicator within an adjustable region of interest of said image map; and

(B) adjusting at least one of a position, size or shape of said region of interest area in response to a change in a reader depth of said reader.

28. The method of claim 27, wherein said adjusting step (B) is executed in response to a receipt by said reader of a manually input user-input command to change at least one of a size, position, or shape of said region of interest.

29. The method of claim 27, wherein said adjusting step (B) includes the step of adjusting a size of said region of interest area.

31. The method of claim 27, further comprising the step of interpolating constructed pixel values from pixel values within said region of interest area.

32. The method of claim 27, wherein said method includes the step of utilizing a portable reader to capture said frames of image data.

33. The method of claim 27, wherein said method includes the step of utilizing a stationary position reader to capture said frames of image data.

30. A method of operating a bar code reader which captures frames of image data, said method comprising the steps of:

(A) defining a region of interest area in an initially captured frame of image data, said initially captured frame of image data including an M×

N array of pixel values, said region of interest area including a subset of said M×

N array of pixel values;

(B) searching for a decodable symbol representation within said region of interest area;

(C) maintaining an original dimension of said region of interest area if in said searching step (B) a decodable symbol representation is determined to be positioned entirely within said region of interest area; and

(D) automatically expanding a dimension of said region of interest area if at step (B) it is determined that an entire decodable symbol representation is not located within said region of interest area.