Indicia sensor system for optical reader

• US 20030218069A1
• Filed: 05/20/2003
• Published: 11/27/2003
• Est. Priority Date: 11/02/1999
• Status: Abandoned Application

• Current Assignee: Welch Allyn Incorporated
• Original Assignee: Welch Allyn Incorporated
• Inventors: Meier, Timothy P., Barber, Charles P., Hussey, Robert M.
• Application Number:
  US10/441,473
• Publication Number:
  US 20030218069A1
• Time in Patent Office: Days
• US Class Current: 235/462.25
• CPC Class Codes: G06K 2207/1018 Source control
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners
• CPC Class Codes: G06K 7/109 adaptations to make the hand-held scanner useable as a fixed scanner

Abstract

In the present invention, the control unit of an optical reader analyzes image data being generated by the imaging element of the reader and changes the mode of operation of the reader if the image data indicates that machine readable indicia, such as a bar code symbol or a text character, is likely in the field of view of the reader. Normally, analysis of image data includes the step of detecting for edge transitions in the image information. If the control unit determines that the image data includes more than a predetermined number of edge transitions, then the control unit imparts appropriate control over various reader elements to change the mode of operation of the reader. Normally, the control unit changes the mode of operation of the reader from a first mode, wherein the reader does not operate to decode or recognize image data to a second mode, wherein the reader operates to decode and/or recognize image data.

Claims

1. A method for operating an optical reading device, the optical reading device including an imaging assembly and a control system, the method including the steps of:

capturing a frame of imaging data using the imaging assembly;

applying at least one adaptive threshold to the imaging data to obtain edge transition data;

analyzing the edge transition data to detect the presence of machine readable indicia; and

changing a mode of operation of the device from a first mode of operation to at least one second mode of operation, if the step of analyzing indicates that the imaging data represents machine readable indicia.

2. The method of claim 1, wherein the step of applying further comprises:

obtaining a line of the imaging data;

applying the at least one adaptive threshold for the line of imaging data; and

recording an edge transition when said image information crosses the at least one adaptive threshold.

3. The method of claim 2, wherein the at least one adaptive threshold includes two adaptive thresholds.

4. The method of claim 3, wherein the two adaptive thresholds includes a maximum adaptive threshold and a minimum adaptive threshold.

5. The method of claim 4, wherein the edge transition data indicates an edge transition when the line of imaging data crosses both the maximum adaptive threshold and the minimum adaptive threshold.

6. The method of claim 4, wherein the maximum adaptive threshold is approximately 80% of the line.

7. The method of claim 4, wherein the minimum adaptive threshold is approximately 20% of the line.

8. The method of claim 1, wherein the at least one adaptive threshold is applied on a pixel-by-pixel basis, such that the adaptive threshold for a pixel is a function of pixel values proximate the pixel.

9. The method of claim 1, wherein the step of applying further comprises the step of performing a pixel variance measurement.

10. The method of claim 9, wherein the pixel variance measurement further comprises:

calculating a difference between a maximum pixel value and a minimum pixel value; and

comparing the difference to a predetermined value to determine whether the imaging data represents an edge transition.

11. The method of claim 10, wherein an edge transition is detected if the difference is greater than the predetermined value, and an edge transition is not detected if the difference is less that or equal to the predetermined value.

12. The method of claim 9, wherein the pixel variance measurement further comprises:

calculating a difference between an average local maximum pixel value and an average local minimum pixel value; and

comparing the difference to a predetermined value to determine whether the imaging data represents an edge transition.

13. The method of claim 12, wherein an edge transition is detected if the difference is greater than the predetermined value, and an edge transition is not detected if the difference is less that or equal to the predetermined value.

14. The method of claim 12, wherein the average local maximum pixel value and the average local minimum pixel value are pixel values taken from a line of imaging data.

15. The method of claim 9, wherein the imaging data represents a gray scale image if the difference is less that or equal to the predetermined value.

16. The method of claim 1, further comprising the step of recording detected edge transitions when a pixel value crosses the at least one adaptive threshold.

17. The method of claim 16, wherein the step of applying includes the step of setting a maximum threshold and a minimum threshold, and wherein the recording step includes the step of counting an edge transition if said image information rises above said maximum threshold or falls below said minimum threshold.

18. The method of claim 17, wherein the maximum threshold is separated from the minimum threshold by a predetermined value.

19. The method of claim 1, wherein the optical reading device is not configured to decode imaging data in the first mode, but is configured to read optical indicia in the at least one second mode.

20. The method of claim 19, wherein the optical indicia includes bar code indicia.

21. The method of claim 20, wherein the bar code indicia includes a linear bar code and/or a two-dimensional bar code.

22. The method of claim 19, wherein the optical indicia is read using optical character recognition.

23. The method of claim 1, wherein the optical reading device is configured to provide increased illumination in the at least one second mode.

24. The method of claim 1, wherein the step of changing step further comprises:

determining a number of edge transitions in the edge transition; and

changing the mode if the number of edge transitions exceeds a predetermined amount.

25. The method of claim 1, wherein the step of changing step further comprises:

determining a number of edge transitions in the edge transition; and

changing the mode if the number of edge transitions changes by a predetermined amount.

26. The method of claim 1, wherein step of analyzing further comprises:

sequentially analyzing a plurality of lines of imaging data; and

Terminating the step of analyzing if one of the plurality of lines indicates the presence of edge transitions in excess of a predetermined amount.

27. The method of claim 1, wherein the step of analyzing includes the step of sequentially analyzing vertical, horizontal, and diagonal rows of image information.

28. The method of claim 1, wherein the step of analyzing includes the step of sequentially analyzing parallel lines of image information.

29. An optical imaging device for reading machine readable indicia disposed on an object, the device comprising:

an imaging assembly configured to capture a frame of imaging data corresponding to an image of the object; and

a control system coupled to the imaging assembly, the processor being configured to,

apply at least one adaptive threshold to the imaging data to thereby detect edge transitions in the imaging data,

analyze the edge transitions to determine whether the imaging data includes machine readable indicia, and

decode the machine readable indicia if the step of analyzing indicates the presence of machine readable indicia.

30. The optical imaging device of claim 29, wherein the control system is further configured to change a mode of operation of the optical reader if the step of analyzing indicates the presence of machine readable indicia.

31. The optical reading device of claim 29, wherein the control system is further configured to:

analyze at least one line of image information from the captured frame; and

change a mode of operation of the optical reading device if the number of edge transitions exceeds a predetermined amount.

32. The optical reading device of claim 31, wherein the control system is configured to sequentially analyze a plurality of the lines of image information in the captured frame

33. The optical reading device of claim 29, wherein the control system sequentially analyzes vertical, horizontal, and diagonal rows of image information.

34. The optical reading device of claim 29, wherein the control system is further configured to:

analyze at least one line of imaging data; and

record the edge transitions of the at least one line of imaging data.

35. The optical reading device of claim 34, wherein the at least one adaptive threshold includes a maximum threshold and a minimum threshold, the control system being configured to count an edge transition if a portion of the at least one line exceeds the maximum threshold or falls below the minimum threshold.

36. The optical reading device of claim 35, wherein a value of the maximum threshold and a value of the minimum threshold differ by a predetermined amount.

37. The optical reading device of claim 29, wherein the control system is further configured to:

analyze at least one line of image information from the captured frame; and

change the mode of operation of the optical reading device if the number of the edge transitions changes by a predetermined amount.

38. The optical reading device of claim 36, wherein the control system is further configured to sequentially analyze a plurality of lines of the captured frame.

39. The optical reading device of claim 36, wherein the control system is further configured to terminate detection of the edge transitions when the number of the edge transitions changes by a predetermined amount.

40. The optical reading device of claim 29, wherein the control system is configured to sequentially analyze vertical, horizontal, and diagonal rows of image information.

41. The optical reading device of claim 29, wherein the control system is further configured to analyze at least one line of imaging data and record the edge transitions based on crossings of the line of imaging data of the at least one adaptive threshold.

42. The optical reading device of claim 41, wherein the at least one adaptive threshold includes a maximum threshold and a minimum threshold, and the control system is configured to record the an edge transition if a portion of the line of imaging data exceeds the maximum threshold or falls below the minimum threshold.

43. The optical reading device of claim 42, wherein the maximum threshold and the minimum threshold are separated by a predetermined range of values such that edge transitions are not recorded from imaging data corresponding to a substantially uniform gray scale image.