Method and apparatus for compensating for fixed pattern noise in an imaging system

• US 7,304,670 B1
• Filed: 03/28/1997
• Issued: 12/04/2007
• Est. Priority Date: 03/28/1997
• Status: Expired due to Fees

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Havens, William H., Hussey, Robert M.
• Primary Examiner(s): Ometz; David
• Assistant Examiner(s): Nguyen; Luong T.
• Application Number:
  US08/828,340
• Time in Patent Office: 3,903 Days
• Field of Search: 348/241, 348/243, 348/247, 348/250, 348/251, 348/254, 382/261, 382/373, 358/406, 358/504, 235/462.11, 235/462.24
• US Class Current: 348/241
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/671 for non-uniformity detection or correction
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise
• CPC Class Codes: H04N 5/76 Television signal recording

Abstract

There is described a pixel value adjustment method and apparatus. In one embodiment, pixel values can be adjusted by execution of an algorithm for adjusting pixel values. In one embodiment, an apparatus capable of executing an algorithm for adjusting pixel values is capable of operating in a decoding operating application. In one embodiment, an apparatus capable of executing an algorithm for adjusting pixel values is capable of operating in a video display operating application.

Claims

1. A method for configuring an imaging system in a setup mode of operation so that in a run mode of operation said imaging system compensates image signals generated by said imaging system for fixed pattern noise, said imaging system having an image sensor including a pixel array and being in communication with a control processor, said method comprising the steps of:

exposing said pixel array to a scene having a known radiance;

capturing a predetermined number of image signal frames of said known radiance scene and finding a column white value for each column of said pixel array when said each frame is captured, wherein said finding step includes the step of discarding a predetermined number of pixel values in at least one column based on gray scale values of said pixel values;

averaging said column white values to determine an average column white value for each column of said pixel array;

comparing said each average column white value to a predetermined reference value for each column, and therefrom determining a correction value for each column of said array; and

storing said each correction value into a storage location for retrieval by said processor when said processor processes image signals from said image sensor in said run mode of operation.

2. The method of claim 1, wherein said finding step further includes the step of discarding a predetermined number of highest gray scale valued pixel values in a column, and identifying the highest gray scale value present out of the remaining pixel values of the column.

3. The method of claim 1, wherein said finding step includes the step of discarding a predetermined number of highest gray scale valued pixel values in a column, and averaging the gray scale values of the remaining pixel values.

4. The method of claim 1, wherein said predetermined reference value of each column is a constant value in the range of column white values for said array.

5. The method of claim 1, wherein said comparing step includes the step of determining a reference value for each column based on an average column white value associated with at least one column positionally related to said column for which a reference value is currently being determined.

6. The method of claim 1, wherein said comparing step includes the step of determining a reference value for each column based on an average column white value associated with the column for which a reference value is currently being determined and on average column white values associated with columns positionally related to said column for which a reference value is currently being determined.

7. The method of claim 1, wherein the method is a method for configuring a monochrome imaging system.

8. The method of claim 1, wherein the method is a method for configuring a bar code reading device imaging system.

9. The method of claim 1, wherein said pixel array includes a plurality of rows and plurality of columns of pixels.

10. A method for configuring an imaging system in a setup mode of operation so that in a run mode of operation said imaging system compensates image signals generated by said imaging system for fixed pattern noise, said imaging system having an image sensor including a pixel array and being in communication with a control processor, said method comprising the steps of:

exposing said pixel array to a first scene having a first known radiance;

capturing a predetermined number of image signal frames of said first scene into predetermined storage locations of said processor and finding a first column white value for at least one column of said array when said each frame is captured, said each frame comprising a plurality of pixel values, wherein said finding step includes the step of discarding a predetermined number of pixel values in said at least one column;

averaging column white values of at least one of said columns to determine a first average column white value for said at least one column of said pixel array when said pixel array is exposed to said first scene;

subjecting said pixel array to a second scene having a second known radiance;

reading a predetermined number of image signal frames of said second scene into predetermined storage locations of said processor and identifying a second column white value for at least one column of said array when said each frame is captured, said each frame comprising a plurality of pixel values;

calculating an average of column white values of at least one of said columns to determine a second average column white value for said at least one column of said pixel array when said pixel array is exposed to said second scene;

determining additive term and multiplicative term correction values for said at least one pixel based on a relationship between said first and second average white values pertaining to said at least one pixel and on said first and second scene radiances; and

storing said multiplicative term and said additive term correction values into predetermined storage locations of said processor for retrieval by said processor when said processor processes image signals from said image sensor in a run mode of operation.

11. The method of claim 10, wherein said finding step includes the step of discarding a predetermined number of highest gray scale valued pixel values in the column, and identifying the highest gray scale value present out of the remaining pixel values of the column.

12. The method of claim 10, wherein said finding step includes the step of discarding a predetermined number of highest gray scale valued pixel values in a column, and averaging the gray scale values of the remaining pixel values.

13. The method of claim 10, wherein the method is a method for configuring a monochrome imaging system.

14. The method of claim 10, wherein the method is a method for configuring a bar code reading device imaging system.

15. The method of claim 10, wherein said pixel array includes a plurality of rows and a plurality of columns of pixels.

16. The method for operating an imaging system so that said imaging system compensates image signals generated by said imaging system for fixed pattern noise, said imaging system having an image sensor including a pixel array and a control processor, said method comprising the steps of:

in a setup mode of operation,

determining a plurality of correction values corresponding to a plurality of pixels or columns of said array; and

storing said plurality of correction values in a first predetermined memory location of said control processor;

in a run mode of operation,

capturing a frame of image data comprising uncorrected pixel values into a second predetermined memory location of said processor; and

applying correction values only to selected pixel values of said frame when reading said selected pixel values from said second predetermined memory location for further processing, wherein said selected pixel values comprise less than all pixel values of said frame.

17. The method of claim 16, wherein said method further includes the step of locating a region of interest comprising a subset of pixel values of said frame of image data, and wherein said selected pixel values comprise positionally related pixels within said region of interest.

18. The method of claim 16, wherein said selected pixel values are corrected for using said correction values when said pixel values are read out of said second predetermined memory location for attempting to decode for any decodable indicia which may be represented in said captured frame of image data.

19. The method of claim 16, wherein the method is a method for operating a monochrome imaging system.

20. The method of claim 16, wherein the method is a method for operating a bar code reading device imaging system.

21. The method of claim 16, wherein said pixel array includes a plurality of rows and plurality of columns of pixels.

22. A method for configuring an imaging system in a setup mode of operation so that in a run mode of operation said imaging system compensates image signals generated by said imaging system for fixed pattern noise, said imaging system having an image sensor including a pixel array and being in communication with a control processor, said method comprising the steps of:

exposing said pixel array to a scene having a known radiance;

capturing a predetermined number of image signal frames of said known radiance scene and finding a column white value for each column of said array when said each frame is captured;

averaging said column white values to determine an average column white value for each column of said pixel array;

comparing said each average column white value to a reference value for each column, and therefrom determining a correction value for each column of said array, wherein said reference value for each column is found by considering average column white values in columns in positional proximity with said column for which said reference value is presently being determined preferentially to those columns not in positional proximity with said column for which said reference value is presently being determined; and

storing said each correction value into a storage location of said processor for retrieval by said processor when said processor processes image signals from said image sensor in said run mode of operation.

23. The method of claim 22, wherein said comparing step includes the step of finding said reference value for each column based on an average column white value associated with the column for which a reference value is currently being determined and on average column white values associated with columns positionally related to said column for which a reference value is currently being determined.

24. The method of claim 22, wherein the method is a method for configuring a monochrome imaging system.

25. The method of claim 22, wherein the method is a method for configuring a bar code reading device imaging system.

26. The method of claim 22, wherein said pixel array includes a plurality of rows and a plurality of columns of pixels.

27. A method for configuring an imaging system in a setup mode of operation so that in a run mode of operation said imaging system compensates image signals generated by said imaging system for fixed pattern noise, said imaging system having an image sensor including a pixel array and being in communication with a control processor, said method comprising the steps of:

exposing said pixel array to a scene having a known radiance, said pixel array comprising a plurality of pixels;

capturing a predetermined number of image signal frames of said scene into predetermined storage locations of said processor, said each frame comprising a plurality of white values, said each white value corresponding to one of said pixels;

averaging white values corresponding to at least one of said pixels to determine an average white value for said at least one pixel of said pixel array;

comparing said average white value to a reference value for said at least one pixel, and therefrom determining a correction value for said at least one pixel of said array, wherein said reference value is found by considering average white values of pixels in positional proximity with said pixel for which said reference value is currently being determined preferentially to those of pixels not in positional proximity with said pixel for which said reference value is presently being determined; and

storing said correction value into a storage location of said processor for retrieval by said processor when said processor processes image signals from said image sensor in said run mode of operation.

28. The method of claim 27, wherein said comparing step includes the step of finding a reference value for said at least one pixel based on the average white values of a predetermined number of pixels positionally related to and including said at least one pixel.

29. The method of claim 27, wherein the method is a method for configuring a monochrome imaging system.

30. The method of claim 27, wherein the method is a method for configuring a bar code reading device imaging system.

31. The method of claim 27, wherein said pixel array includes a plurality of rows and a plurality of columns of pixels.

32. A method for operating an imaging system, said imaging system having an image sensor including a pixel array and a control processor, said method comprising the steps of:

determining a correction value for at least one pixel or column of said array; and

storing said at least one correction value in a first predetermined memory location of said control processor;

in a run mode of operation, capturing a frame of image data into a second predetermined memory location of said processor;

correcting at least one pixel value of said frame using said correction value stored in said first memory location; and

launching a bar code decoding algorithm for attempting to decode for decodable bar code indicia which may be represented in said frame of image data including said at least one corrected pixel value corrected in said correcting step,

wherein said storing step includes the step of storing a column correction value for substantially each column of said pixel array.

33. The method of claim 32, wherein said control processor executes said correcting step substantially contemporaneously with said capturing step, by correcting said at least one pixel value using said correction value while storing said frame of image data into said second memory location.

34. The method of claim 32, wherein said control processor executes said correcting step subsequent to said capturing step, by storing, in said capturing step, an uncorrected frame of image data corresponding to a scene in said second memory location, and by executing said correcting step by correcting said at least one pixel value using said correction value while reading said uncorrected frame of image data from said second memory location.

35. The method of claim 32, wherein said storing step includes the step of storing a pixel correction value for substantially each pixel of said pixel array.

36. The method of claim 32, wherein said storing step includes the step of storing a column correction value for substantially each column of said pixel array.

37. The method of claim 32, wherein said determining step comprises an exposing step including the step of exposing said pixel array to at least two scenes having different radiances and wherein said storing step includes the step of storing a correction value having both a multiplication component and an additive component.

38. The method of claim 32, wherein the method is a method for configuring a monochrome imaging system.

39. The method of claim 32, wherein the method is a method for configuring a bar code reading device imaging system.

40. The method of claim 32, wherein said pixel array includes a plurality of rows and a plurality of columns of pixels.

41. A method for operating an imaging system, said imaging system having an image sensor including a pixel array and a control processor, said method comprising the steps of:

determining a correction value for at least one pixel or column of said array; and

storing said at least one correction value in a first predetermined memory location of said control processor;

in a run mode of operation;

capturing a frame of image data into a second predetermined memory location of said processor; and

correcting at least one pixel value of said frame using said correction value stored in said first memory location; and

launching a bar code decoding algorithm for attempting to decode for decodable bar code indicia which may be represented in said frame of image data including said at least one corrected pixel value corrected in said correcting step,

wherein said determining step comprises an exposing step including the step of exposing said pixel array to at least two scenes having different radiances and wherein said storing step includes the step of storing a correction value having both a multiplication component and an additive component.

42. The method of claim 41, wherein said control processor executes said correcting step substantially contemporaneously with said capturing step, by correcting said at least one pixel value using said correction value while storing said frame of image data into said second memory location.

43. The method of claim 41, wherein said control processor executes said correcting step subsequent to said capturing step, by storing, in said capturing step, an uncorrected frame of image data corresponding to a scene in said second memory location, and by executing said correcting step by correcting said at least one pixel value using said correction value while reading said uncorrected frame of image data from said secondary memory location.

44. The method of claim 41, wherein said storing step includes the step of storing a pixel correction value for substantially each pixel of said pixel array.

45. The method of claim 41, wherein said storing step includes the step of storing a column correction value for substantially each column of said pixel array.

46. The method of claim 41, wherein the method is a method for configuring a monochrome imaging system.

47. The method of claim 41, wherein the method is a method for configuring a bar code reading device imaging system.

48. The method of claim 41, wherein said pixel array includes a plurality of rows and a plurality of columns of pixels.

49. An indicia decoding device configured to correct for fixed pattern noise, said indicia decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said indicia decoding device is configured to store into said memory unit at least one correction parameter for correcting a pixel value of a frame of image data, said at least one correction parameter having a value and being a pixel correction value or a column correction value, and wherein said indicia decoding device has an indicia decoding operating application and is operable in a run mode of operation; and

wherein said indicia decoding device when operated in said run mode of operation with said indicia decoding operating application active (i) stores into said memory unit said frame having a plurality of pixel values, (ii) utilizes said at least one correction parameter to correct at least one pixel value of said frame, and (iii) activates a decoding algorithm for attempting to decode decodable indicia represented in image data including at least one pixel value corrected utilizing said at least one correction parameter, wherein said value of said at least one correction parameter is determined prior to a time that said indicia decoding device is operated in said run mode of operation and wherein said value of said at least one correction parameter is independent of any image represented in said frame.

50. The indicia decoding device of claim 49, wherein said at least one correction parameter is a plurality of correction values and wherein said indicia decoding device further when operating in said run mode of operation utilizes said plurality of correction values to correct for pixel values corresponding to less than all of said plurality of pixels of said image sensor.

51. The indicia decoding device of claim 49, wherein said indicia decoding device further when operating in said run mode of operation avoids reading said at least one correction parameter from said memory unit to correct said at least one pixel value until said frame of pixel values is stored into said memory unit.

52. The indicia decoding device of claim 49, wherein said indicia decoding device further has a video display operating application, wherein said indicia decoding device is configured to execute a first fixed pattern noise correction algorithm when said video display operating application is active and a second fixed pattern noise correction algorithm when said indicia decoding operating application is active, the first fixed pattern noise correction algorithm being different from said second fixed pattern noise correction algorithm.

53. The indicia decoding device of claim 49, wherein said indicia decoding device further has a video display operating application, wherein said indicia decoding device is configured to execute a first algorithm for adjusting pixel values when said video display operating application is active and a second algorithm for adjusting pixel values when said indicia decoding operating application is active, the first algorithm being different from said second algorithm.

54. The indicia decoding device of claim 49, wherein said indicia decoding device further has a video display operating application, wherein said indicia decoding device is configured to execute a certain fixed pattern noise correction algorithm when said video display operating application is active, said indicia decoding device further being configured to avoid executing said certain fixed pattern noise correction algorithm when said indicia decoding operating application is active.

55. The indicia decoding device of claim 49, wherein said indicia decoding device further has a video display operating application, wherein said indicia decoding device is configured to execute a certain algorithm for adjusting pixel values when said video display operating application is active, said indicia decoding device further being configured to avoid executing said certain algorithm for adjusting pixel values when said indicia decoding operating application is active.

56. The indicia decoding device of claim 49, wherein said indicia decoding device further has a video display operating application, wherein said indicia decoding device is configured to correct for a cosine effect when said video display operating application is active, wherein said indicia decoding device is further configured to avoid correcting for said cosine effect when said decoding operating application is active.

57. The indicia decoding device of claim 49, wherein said image sensor is a monochrome image sensor.

58. A bar code decoding device, said bar code decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said bar code decoding device is configured to operate in accordance with a video display operating application and a decoding operating application; and

wherein said bar code decoding device is configured to execute a first fixed pattern noise correction algorithm when said video display operating application is active and a second fixed pattern noise correction algorithm when said decoding operating application is active, the first fixed pattern noise correction algorithm being different from said second fixed pattern noise correction algorithm.

59. The bar code decoding device of claim 58, wherein said first fixed pattern noise correction algorithm is an algorithm which corrects for fixed pattern noise attributable to a cosine effect.

60. The bar code decoding device of claim 58, wherein said first fixed pattern noise correction algorithm is a first algorithm which corrects for fixed pattern noise attributable to a cosine effect, and wherein said second fixed pattern noise correction algorithm is a second algorithm which does not correct for fixed pattern noise attributable to cosine effect.

61. A bar code decoding device, said bar code decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said bar code decoding device is configured to operate in accordance with a video display operating application and a decoding operating application; and

wherein said bar code decoding device is configured to execute a first algorithm for adjusting pixel values when said video display operating application is active and a second algorithm for adjusting pixel values when said decoding operating application is active, the first algorithm being different from said second algorithm.

62. The bar code decoding device of claim 61, wherein said first algorithm is an algorithm which corrects for fixed pattern noise attributable to a cosine effect.

63. The bar code decoding device of claim 61, wherein said second algorithm is an algorithm which does not correct for fixed pattern noise attributable to a cosine effect.

64. The bar code decoding device of claim 61, wherein said first algorithm is an algorithm which corrects for fixed pattern noise.

65. A bar code decoding device, said bar code decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said bar code decoding device is configured to operate in accordance with a video display operating application and a decoding operating application; and

wherein said bar code decoding device is configured to execute a certain fixed pattern noise correction algorithm when said video display operating application is active, said bar code decoding device further being configured to avoid executing said certain fixed pattern noise correction algorithm when said decoding operating application is active.

66. The bar code decoding device of claim 65, wherein said certain fixed pattern noise correction algorithm is an algorithm which corrects for fixed pattern noise attributable to a cosine effect.

67. A bar code decoding device, said bar code decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said bar code decoding device is configured to operate in accordance with a video display operating application and a decoding operating application; and

wherein said bar code decoding device is configured to execute a certain algorithm for adjusting pixel values when said video display operating application is active, said bar code decoding device further being configured to avoid executing said certain algorithm for adjusting pixel values when said decoding operating application is active.

68. The bar code decoding device of claim 67, wherein said certain algorithm is an algorithm which corrects for fixed pattern noise attributable to a cosine effect.

69. The bar code decoding device of claim 67, wherein said image sensor is a monochrome image sensor.

70. The bar code decoding device of claim 67, wherein said bar code decoding device is configured to adjust pixel values when said decoding operating application is active.

71. The bar code decoding device of claim 67, wherein said certain algorithm is an algorithm which corrects for fixed pattern noise.

72. A bar code decoding device, said bar code decoding device comprising:

an image sensor having a plurality of pixels formed in a two dimensional array of light sensitive pixels, said two dimensional array of light sensitive pixels including a plurality of rows and a plurality of columns of pixels;

a control processor processing image data, said control processor being in communication with said image sensor;

a memory unit including a program memory coupled to said control processor and a working memory coupled to said control processor;

wherein said bar code decoding device is configured to operate in accordance with a video display operating application and a decoding operating application; and

wherein said bar code decoding device is configured to execute a certain algorithm for adjusting pixel values when said decoding operating application is active, said bar code decoding device further being configured to avoid executing said certain algorithm for adjusting pixel values when said video display operating application is active.

73. The bar code decoding device of claim 72, wherein said bar code decoding device is configured to adjust pixel values when said video display operating application is active.