Adaptive digitizer for optical reader

• US 7,471,828 B1
• Filed: 03/19/2007
• Issued: 12/30/2008
• Est. Priority Date: 03/16/2001
• Status: Expired due to Fees

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Meier, Timothy P.
• Primary Examiner(s): Couso; Jose L
• Application Number:
  US11/725,598
• Time in Patent Office: 652 Days
• Field of Search: 382/173, 382/214, 382/270, 382/273, 382/312, 382/313, 382/318, 358/473, 358/474, 235/454, 235/462.1, 235/460, 235/462.07, 235/462.25, 235/462.27, 235/470, 235/487, 23547201-47203, 235/462.08, 235/462.15, 235/462.16, 235/462.01
• US Class Current: 382/173
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/162 Quantising the image signal

Abstract

The present invention is an optical reader configured to adaptively digitize a set of image data in a manner that depends of characteristics of the image data. According to the invention, an optical reader subjects a set of image data to preliminary processing for developing peak characterizing data. From the peak characterizing data, the optical reader determines at least one digitization parameter and utilizes the at least one digitization parameter in the digitization of the image data.

Claims

1. An optical reader comprising:

a hand held housing;

a trigger for initiating reading of decodable indicia;

means for generating an array of multibit pixel values;

means for establishing max and min peak tracking lines for said array of pixel values;

means for subjecting said array of multibit pixel values to a peak characterizing data development routine, wherein said subjecting means including means for sensing peaks of said array of multibit pixel values using iteratively aggressive peak sensing thresholds;

means responsive to said subjecting means for developing peak characterizing data characterizing peaks of said array of multibit pixel values;

means for determining a plurality of digitization parameters based on said developed peak characterizing data, wherein said plurality of digitization parameters include a peak sensing threshold parameter, and grey band position parameters, said grey band position parameters defining a grey band; and

means for finding a first plurality of edge positions and a second plurality of edge positions represented by said array of pixel values utilizing said plurality of digitization parameters

wherein the edge positions composing said first plurality of edge positions are located outside said grey band; and

wherein the edge positions composing said second plurality of edge positions are located within said grey band.

2. The reader of claim 1, wherein said generating means generates an array of pixel values corresponding to a row of pixels of a 1D image sensor.

3. The reader of claim 1, wherein said generating means generates an array of pixel values corresponding to a line of pixels of a 2D image sensor.

4. The reader of claim 1, wherein said establishing means comprises means for establishing a forward tracking line, a backward direction tracking line, and means for compositing said forward and backward tracking lines.

5. The reader of claim 1, wherein said subjecting means includes means for subjecting said array of pixel values to peak sensing thresholds that depend on a difference between said max and min peak tracking lines.

6. The reader of claim 1, wherein said subjecting means includes means for subjecting said array of pixel values to a first peak sensing threshold, a second peak sensing threshold, and a third peak sensing threshold.

7. The reader of claim 1, wherein said determining means determines said peak sensing threshold to be a previous data development peak sensing threshold if a present data development peak sensing threshold senses no new peaks.

8. The reader of claim 1, further comprising means for calculating an average max peak value and an average min peak value.

9. The reader of claim 1, further comprising means for calculating an average max peak value and an average min peak value, wherein said finding means is responsive to said calculating means.

10. The reader of claim 1, wherein said reader is operative for calculating an average max peak value and an average min peak value, wherein said finding means is responsive to said calculating.

11. A method for digitizing image data corresponding to a bar code symbol, the method comprising the steps of:

generating an array of multibit pixel values which define a pattern including a set of oscillating peaks that are attributable to bar-space transitions of the bar code symbol;

establishing a max peak tracking line and a min peak tracking line for the array of multibit pixel values;

establishing a first grey band tracking line and a second grey band tracking line dependent upon the max peak tracking line and the min peak tracking line;

determining a first plurality of edge positions represented by the array of multibit pixel values for peaks which fall outside the grey band tracking lines; and

determining a second plurality of edge positions represented by the array of multibit pixel values for peaks which fall within the grey band tracking lines.

12. The method of claim 11, wherein the max peak tracking line and the min peak tracking line are not significantly dependent on a level of noise within the image data.

13. The method of claim 11, wherein the edge positions comprising the first plurality of edge positions depend upon at least one peak sensitivity threshold.

14. The method of claim 11, wherein the edge positions comprising the first plurality of edge positions depend upon at least one peak sensitivity threshold, the at least one peak sensitivity threshold determined as a fraction of a difference between the max peak tracking line and the min peak tracking line.

15. The method of claim 11, wherein the edge positions comprising the first plurality of edge positions are determined iteratively using at least one of:

a set of increasing peak sensitivity thresholds, a set of decreasing peak sensitivity thresholds.

16. The method of claim 11, wherein the first grey band tracking line and the second grey band tracking line are dependent upon an average max peak value and an average min peak value.

17. The method of claim 11, wherein the edge positions comprising the second plurality of edge positions depend upon at least one peak sensitivity threshold.

18. The method of claim 11, wherein the edge positions comprising the second plurality of edge positions depend upon at least one peak sensitivity threshold, the at least one peak sensitivity threshold determined by a pre-defined number of grey scale positions.

19. The method of claim 11, wherein the edge positions comprising the first plurality of edge positions depend upon a first peak sensitivity threshold;

wherein the edge positions comprising the second plurality of edge positions depend upon a second peak sensitivity threshold; and

wherein the second peak sensitivity threshold is more sensitive to peaks than the first peak sensitivity threshold.

20. The method of claim 11, wherein the array of multibit pixel values includes interpolated pixel values.

21. A method for digitizing image data corresponding to a bar code symbol, the method comprising the steps of:

generating an array of multibit pixel values which define a pattern including a set of oscillating peaks that are attributable to bar-space transitions of the bar code symbol;

establishing a max peak tracking line and a min peak tracking line for the array of multibit pixel values;

iteratively determining a first plurality of edge positions represented by the array of multibit pixel values using at least one first peak sensitivity threshold;

establishing a first grey band tracking line and a second grey band tracking line dependent upon the max peak tracking line and the min peak tracking line; and

determining a second plurality of edge positions represented by the array of multibit pixel values for peaks which fall within the grey band tracking lines.

22. The method of claim 21, wherein the max peak tracking line and the min peak tracking line are not significantly dependent on a level of noise within the image data.

23. The method of claim 21, wherein the step of determining edge positions is followed by a step of calculating an average max peak value and an average min peak value;

and

wherein the first grey band tracking line and the second grey band tracking line are further dependent on the average max peak value and the average min peak value.

24. The method of claim 21, wherein the at least one first sensitivity threshold is determined as a fraction of a difference between the max peak tracking line and the min peak tracking line.

25. The method of claim 21, wherein the at least one first peak sensitivity threshold is provided by at least one of:

a set of increasing peak sensitivity thresholds, a set of decreasing peak sensitivity thresholds.

26. The method of claim 21, wherein the edge positions comprising the second plurality of edge positions depend upon at least one second peak sensitivity threshold.

27. The method of claim 21, wherein the edge positions comprising the second plurality of edge positions depend upon at least one second peak sensitivity threshold, the at least one second peak sensitivity threshold determined by a pre-defined number of grey scale positions.

28. The method of claim 21, wherein the edge positions comprising the second plurality of edge positions depend upon at least one second peak sensitivity threshold;

and

wherein the second peak sensitivity threshold is more sensitive to peaks than the first peak sensitivity threshold.

29. The method of claim 21, wherein the array of multibit pixel values includes interpolated pixel values.

36. The method of claim 21, wherein the array of multibit pixel values includes interpolated pixel values.

30. A method for digitizing image data corresponding to a bar code symbol, the method comprising the steps of:

generating an array of multibit pixel values which define a pattern including a set of oscillating peaks that are attributable to bar-space transitions of the bar code symbol;

determining a plurality of edge positions represented by the array of multibit pixel values using a peak sensitivity threshold;

determining a digitizing peak sensing level for the plurality of edge positions;

conditionally, upon satisfying a condition dependent upon the digitizing peak sensing level, changing the peak sensitivity threshold and looping back to the step of determining a plurality of edge positions.

31. The method of claim 30, wherein the condition dependent upon the digitizing peak sensing level is selected from the group consisting of:

the peak sensing level decrease, the peak sensing level increase.

32. The method of claim 30, wherein the step of generating an array of multibit pixel values is followed by a step of establishing a max peak tracking line and a min peak tracking line for the array of multibit pixel values;

and

wherein the peak sensitivity threshold is determined as a fraction of a difference between the max peak tracking line and the min peak tracking line.

33. The method of claim 30, wherein the peak sensitivity threshold is determined by a pre-defined number of grey scale positions.

34. The method of claim 30, further comprising the steps of:

establishing a first grey band tracking line and a second grey band tracking line dependent upon at least one of;

the peak sensitivity threshold, an average max peak value, and an average min peak value; and

determining a second plurality of edge positions represented by the array of multibit pixel values for peaks which fall within the grey band tracking lines.

35. The method of claim 30, further comprising the steps of:

establishing a first grey band tracking line and a second grey band tracking line dependent upon an average max peak value and an average min peak value; and

determining a second plurality of edge positions represented by the array of multibit pixel values for peaks which fall within the grey band tracking lines.