Image data binarization methods enabling optical reader to read fine print indicia

• US 6,575,367 B1
• Filed: 07/13/2000
• Issued: 06/10/2003
• Est. Priority Date: 11/05/1998
• Status: Expired due to Term

• Current Assignee: Welch Allyn Data Collection Inc (Welch Allyn Incorporated)
• Original Assignee: Welch Allyn Data Collection Inc (Welch Allyn Incorporated)
• Inventors: Longacre, Andrew Jr.
• Primary Examiner(s): Frech, Karl D.
• Application Number:
  US09/615,505
• Time in Patent Office: 1,062 Days
• Field of Search: 235/462.1, 235/462.08, 235/462.11, 235/462.12, 235/462.24, 235/462.25, 235/467.09
• US Class Current: 235/462.11
• 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 using an optical reader, said method comprising the steps of:

capturing a grey scale image map;

dividing said image map into a plurality of tiles; and

binarizing pixels of at least one of said tiles in accordance with a certain binarization process when said reader is required to read a pixel of said image map in or in proximity with said at least one of said tiles not previously binarized in accordance with said certain binarization process.

2. The method of claim 1, wherein said certain binarization process is a low resolution binarization process wherein constructed pixel values are not interpolated from pixel values of said at least one tile.

3. The method of claim 1, wherein said certain binarization process is a high resolution binarization process wherein constructed pixel values are interpolated from pixel values of said at least one tile.

4. The method of claim 1, wherein said plurality of tiles are of substantially equal size.

5. The method of claim 1, wherein substantially each of said tiles is an N×

N pixel block.

6. The method of claim 1, wherein s aid reader binarizes said at least one of said tiles when said reader is required to read a first pixel value of said at least one tile not previously binarized in accordance with said binarization process.

7. The method of claim 1, wherein said reader binarizes said one of said tiles when said reader is required to read a pixel that neighbors said one tile not previously binarized in accordance with said certain binarization process.

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

capturing a grey scale image map;

dividing said image map into a plurality of tiles;

while executing a first type of image data processing operation, binarizing pixels of at least one of said tiles in accordance with a low resolution binarization process when said reader is required to read a pixel of said image map in or in proximity with said at least one of said tiles not previously binarized in accordance with said low resolution binarization process; and

while executing a second type of image data processing operation, subjecting pixels of at least one of said tiles to a high resolution binarization process when said reader is required to read a pixel of said image map in or in proximity with said at least one of said tiles not previously binarized in accordance with said high resolution binarization process.

9. The method of claim 8, wherein said first type of image data processing operation is the operation of searching for decodable indicia in said captured image map.

10. The method of claim 8, wherein said second type of image data processing operation is the operation of decoding decodable image data in said captured image map.

11. The method of claim 8, wherein said first type of image data processing operation is the operation of searching for decodable indicia in said captured image map and wherein said second type of image data processing operation is the operation of decoding decodable image data in said captured image map.

14. The method of claim 8, wherein said reader binarizes said one of said tiles when said reader is required to read a first pixel value of said one tile not previously binarized in accordance with said binarization process.

15. The method of claim 8, wherein said reader binarizes said one of said tiles when said reader is required to read a pixel that neighbors said one tile not previously binarized in accordance with said certain binarization process.

12. The method 8, wherein said plurality of tiles are of substantially equal size.

13. The method of 8, wherein substantially each of said tiles is an N×

N pixel block.