SYSTEMS AND METHODS OF OPTICAL CODE READING USING A COLOR IMAGER

• US 20100213259A1
• Filed: 02/18/2010
• Published: 08/26/2010
• Est. Priority Date: 02/20/2009
• Status: Active Grant

• Current Assignee: Datalogic Adc, Inc. (Datalogic S.p.A.)
• Original Assignee: Datalogic Scanning Incorporated (Datalogic S.p.A.)
• Inventors: Gao, WenLiang
• Granted Patent: US 8,800,874 B2
• Time in Patent Office: Days
• US Class Current: 235/469
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• CPC Class Codes: G06K 7/10841 Particularities of the light-sensitive elements semiconductor devices H01L
• CPC Class Codes: G06K 7/1096 the scanner having more than one scanning window, e.g. two substantially orthogonally placed scanning windows for integration into a check-out counter of a super-market
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks

Abstract

Systems and methods of optical code reading include production of image data by a color image sensor array and processing of the image data to decode an optical code. In one configuration, the color image sensor array includes first and second sets of sensor pixels sensitive to light having wavelengths within, respectively, first and second wavelength bands, reflected light is focused by an optical system to form an image of an optical code on the color image sensor array, first and second sets of image data representing light intensity levels sensed by, respectively, the first and second sets of sensor pixels are produced, and the first set of image data is processed to determine whether the second set of image data is to be used in combination with the first set of image data to decode the optical code.

Claims

1. A method of data reading comprising the steps of:

illuminating a field of view of an optical code reader to produce light reflected from an optical code toward an optical system of the optical code reader;

focusing with the optical system the reflected light to form an image of the optical code on a color image sensor array of the optical code reader, the color image sensor array including;

a first set of sensor pixels sensitive to light having a wavelength within a first wavelength band, and

a second set of sensor pixels sensitive to light having a wavelength within a second wavelength band different from the first wavelength band;

producing multiple sets of image data including a first of image data representing light intensity values sensed by the first set of sensor pixels and a second set of image data representing light intensity values sensed the second set of sensor pixels;

selecting from the multiple sets of image data a target set of image data by comparing statistical characteristics of the light intensity values of the first and second sets of image data, the statistical characteristics corresponding to intensity variations of the light intensity values; and

processing the target set of image data to decode the optical code.

2. The method of claim 1, wherein the statistical characteristics correspond to (a) a first standard deviation of the light intensity values of the first set of image data and (b) a second standard deviation of the light intensity values of the second set of image data.

3. The method of claim 2, further comprising:

calculating the first standard deviation based on a first portion of the first set of image data, the first portion representing light intensity values produced by sensor pixels of the first set located in a subarea of the color image sensor array; and

calculating the second standard deviation based on a second portion of the second set of image data, the second portion representing light intensity values produced by sensor pixels of the second set located in the subarea of the color image sensor array.

4. The method of claim 2, wherein the first standard deviation is higher than the second standard deviation, and the first set of image data is selected as the target set of image data.

5. The method of claim 1, wherein the color image sensor array includes a third set of sensor pixels sensitive to light having a wavelength within a third wavelength band, the multiple sets of image data include a third set of image data representing light intensity values sensed by the third set of sensor pixels, and the selecting step includes selecting one of the first, second, and third sets of image data as the target set of image data.

6. A method of data reading, comprising:

illuminating a field of view of an optical code reader to produce light reflected from an optical code toward an optical system of the optical code reader;

focusing with the optical system the reflected light to form an image of the field of view on an array of sensor pixels of a color image sensor array positioned in the optical code reader, the image of the field of view including an image of the optical code, and the array of sensor pixels including;

a first set of sensor pixels sensitive to light having a wavelength within a first wavelength band,

a second set of sensor pixels sensitive to light having a wavelength within a second wavelength band different from the first wavelength band, and

a third set of sensor pixels sensitive to light having a wavelength within a third wavelength band different from the first and second wavelength bands;

producing first, second, and third sets of image data representing light intensity values sensed by, respectively, the first, second, and third sets of sensor pixels;

processing the first set of image data to identify a feature of the optical code that enables categorization of the optical code into one of a number of symbology types;

estimating a size of an image of the feature representing a number of sensor pixels of the first, second, and third sets on which the image of the feature is formed to thereby determine whether the image of the optical code is sufficiently large relative the array of sensor pixels to enable decoding of the optical code using a combination of the first, second, and third sets of image data.

7. The method of claim 6, further comprising estimating a location of the image of the optical code relative to the array of sensor pixels based on a location of the image of the feature to thereby determine whether the location of the image of the optical code enables the decoding of the optical code using the combination of the first, second, and third sets of image data.

8. The method of claim 7, further comprising:

selecting portions of the first, second, and third sets of image data corresponding to sensor pixels of the first, second, and third sets on which the image of the optical code is formed; and

decoding the optical code using the portions of the first, second, and third sets of image data.

9. The method of claim 6, further comprising:

estimating from the size of the image of the feature a pixel-per-module ratio representing a number of sensor pixels of the first, second, and third sets on which an image of a module of the optical code is formed;

comparing the pixel-per-module ratio to a selected ratio representing a minimum number of sensor pixels of the first, second, and third sets on which the image of the module must be formed for the optical code to be decoded using the combination of the first, second, and third sets of image data; and

decoding the optical code when the pixel-per-module ratio is greater than or equal to the selected ratio.

10. The method of claim 6, wherein the first, second, and third wavelength bands corresponds to the colors red, green, and blue, respectively.

11. The method of claim 6, wherein the processing of the first set of image data includes attempting to decode the optical code using the first set of image data.

12. The method of claim 6, further comprising adjusting the light intensity values of the first set of image data relative to the light intensity values of the second set of image data to compensate for differences in a first quantum efficiency of the first set of sensor pixels and a second quantum efficiency of the second set of sensor pixels.

13. A method of data reading, comprising:

illuminating a field of view of an optical code reader to produce light reflected from an optical code toward an optical system of the optical code reader;

focusing with the optical system the reflected light to form an image of the optical code on a color image sensor array of the optical code reader, the color image sensor array including;

a first set of sensor pixels sensitive to light having a wavelength within a first wavelength band,

a second set of sensor pixels sensitive to light having a wavelength within a second wavelength band different from the first wavelength band, and

a third set of sensor pixels sensitive to light having a wavelength within a third wavelength band different from the first and second wavelength bands;

producing image data representing light intensity values sensed by at least one of the first, second, and third sets of sensor pixels;

calculating a percentage of the light intensity values below a selected light intensity threshold value;

comparing the percentage to a selected percentage to determine whether to process the image data and thereby attempt to decode the optical code; and

processing the image data to decode the optical code when the percentage is less than the selected percentage.

14. The method of claim 13, further comprising:

deriving a standard deviation of the light intensity values when the percentage is below the selected percentage;

comparing the standard deviation to a selected standard deviation threshold value to determine whether to perform the processing of the image data to decode the optical code; and

performing the processing when the standard deviation is higher than the selected standard deviation threshold value.

15. The method of claim 14, wherein the image data belong to a first set of image data representing light intensity values sensed by the first set of sensor pixels and the standard deviation is a first standard deviation of the light intensity values of the first set of image data, further comprising:

producing a second set of image data representing light intensity values sensed by the second set of sensor pixels and a third set of image data representing light intensity values sensed by the third set of sensor pixels;

deriving a second standard deviation of the light intensity values of the second set of image data and a third standard deviation of the light intensity values of the third set of image data;

comparing the second and third standard deviations to the selected standard deviation threshold value; and

processing at least one of the first, second, and third sets of image data when at least one of the first, second, and third standard deviations is higher than the selected standard deviation threshold value.

16. The method of claim 13, wherein the percentage is calculated and the standard deviation is derived from a portion of the image data representing a set of intensity values produced by sensor pixels of the first and second sets located in a subarea of the color image sensor array.

17. The method of claim 13, wherein the percentage is calculated from a histogram of the light intensity values.

18. An optical code reader, comprising:

a color image sensor array including;

a first set of sensor pixels sensitive to light having a wavelength within a first wavelength band, the first set of sensor pixels operable to produce a first set of image data representing sensed light intensity values, and

a second set of sensor pixels sensitive to light having a wavelength within a second wavelength band different from the first wavelength band, the second set of sensor pixels operable to produce a second set of image data representing sensed light intensity values;

an optical system operable to direct light on the color image sensor array to form an image of an optical code on the color image sensor array;

a data processing system operable to receive the first and second sets of image data, the data processing system including;

a standard deviation calculation unit operable to calculate a first standard deviation of the intensity values of the first set of image data and a second standard deviation of the intensity values of the second set of image data,

a standard deviation comparison unit operable to compare the first and second standard deviations and identify a highest standard deviation among the first and second standard deviations,

a data set selection unit operable to select as a target set of image data one of the first and second sets of image data based the comparison performed by the standard deviation comparison unit, the target set of image data having the highest standard deviation among the first and second standard deviations, and

a low-resolution decoding unit operable to receive the target set of image data and process the target set of image data to thereby attempt to decode the optical code using only the target set of image data.

19. The optical code reader of claim 18, wherein the color image sensor array includes a third set of sensor pixels sensitive to light having a wavelength within a third wavelength band, the third set of sensor pixels operable to produce a third set of image data representing sensed light intensity values, the standard deviation calculation unit operable to calculate a third standard deviation of the intensity values of the third set of image data, the standard deviation comparison unit operable to compare the first, second, and third standard deviations and to identify the highest standard deviation among the first, second, and third standard deviations, and the data set selection unit operable to select as the target set of image data one of the first, second, and third sets of image data.

20. The optical code reader of claim 19, wherein the data processing system includes a threshold comparison unit operable to compare at least one of the first, second, and third standard deviations to a selected standard deviation threshold value to determine whether said at least one of the first, second, and third standard deviations is greater than the selected standard deviation threshold value, the data set selection unit operable to select the target set of image data and the low-resolution decoding unit operable to process the target set of image data to thereby decode the optical code when the threshold comparison unit determines that said at least one of the first, second, and third standard deviations is greater than the selected standard deviation threshold value.

21. The optical code reader of claim 19, wherein the data processing system includes a pixel selection unit that is operable to select portions of at least one of the first, second, and third sets of image data corresponding to light intensity values produced by sensor pixels of the first, second, and third sets located in a subarea of the color image sensor array, the standard deviation calculation unit operable to calculate the first, second, and third standard deviations from the portions of said at least one of the first, second, and third sets of image data.

22. The optical code reader of claim 19, wherein the data processing system includes a histogram comparison unit that is operable to:

generate a histogram of the light intensity values of the first, second, and third sets of image data,

determine a percentage of the light intensity values of the first, second, and third sets of image data that are below a selected light intensity threshold value, and

compare the percentage to a selected percentage, the data set selection unit operable to select the target set of image data and the low-resolution decoding unit operable to process the target set of image data to thereby decode the optical code when the histogram comparison unit determines that the percentage is below the selected percentage.

23. The optical code reader of claim 19, wherein the data processing system includes a low-resolution decode analysis unit that is operable to determine whether the low-resolution decoding unit decoded the optical code using only the target set of image data.

24. The optical code reader of claim 23, wherein the data processing system includes a full-resolution decoding unit that is operable to decode the optical code using a combination of the first, second, and third sets of image data when the low-resolution decode analysis unit determines that the optical code was not decoded by the low-resolution decoding unit.

25. The optical code reader of claim 24, wherein the low-resolution decoding unit is operable to identify a feature of the optical code based on the target set of image data and to categorize the optical code into one of a number of symbology types based on the feature when the low-resolution decoding unit cannot decode the optical code using only the target set of image data.

26. The optical code reader of claim 25, wherein the data processing system includes a pixel-per-module unit that is operable to estimate a size of an image of the feature representing a number sensor pixels of the first, second, and third sets on which an image of the feature is formed.

27. The optical code reader of claim 26, wherein the pixel-per-module unit is operable to estimate, from the size of the image of the feature, a pixel-per-module ratio representing a number of sensor pixels of the first, second, and third sets on which an image of a module of the optical code is formed to thereby determine if the image of the optical code is sufficiently large to enable the full-resolution decoding unit to decode the optical code.

28. The optical code reader of claim 27, wherein the pixel-per-module unit is operable to compare the pixel-per-module ratio to a selected ratio representing a minimum number of sensor pixels of the first, second, and third sets on which the image of the module must be formed to enable the full-resolution decoding unit to decode the optical code.

29. The optical code reader of claim 25, wherein the data processing system includes a location detection unit that is operable to detect a location on the color image sensor array at which an image of the feature is formed and estimate based on the location a position of the image of the optical code relative to the color image sensor array.

30. The optical code reader of claim 29, wherein the location detection unit is operable to determine whether the position of the image of the optical code enables the full-resolution decoding unit to decode the optical code.

31. An optical code reader comprising:

a color image sensor array including;

a first set of sensor pixels sensitive to a first wavelength of light, and

a second set of sensor pixels sensitive to a second wavelength of light different from the first wavelength of light; and

optics to provide for the optical code reader a first view of an object and a second view of the object, the optics operable to form on the color image sensor array a first image of the first view and a second image of the second view, wherein the first image is formed by light of the first wavelength emanating from the first view and the second image is formed by light of the second wavelength emanating from the second view, the optics substantially excluding from the first image light of the second wavelength emanating from the first view and substantially excluding from the second image light of the first wavelength emanating from the second view to thereby enable the sensor pixels of the first set to sense the first image without substantially sensing the second image and the sensor pixels of the second set to sense the second image without substantially sensing the first image.

32. The optical code reader of claim 31, wherein the optics include:

a first mirror positioned to provide the first view of the object, the first mirror arranged to direct along a first path the light of the first wavelength emanating from the first view;

a second mirror positioned to provide the second view of the object, the second mirror arranged to direct along a second path the light of the second wavelength emanating from the second view; and

wavelength selective reflective optics positioned to intersect the first and second paths, the wavelength selective reflective optics operable to substantially exclude from the first image the light of the second wavelength emanating from the first view and substantially exclude from the second image the light of the first wavelength emanating from the second view.

33. The optical code reader of claim 32, wherein the wavelength selective reflective optics include an optical coating operable to direct along the first path the light of the first wavelength emanating from the first view and to divert from the first path the light of the second wavelength emanating from the first view, the optical coating positioned so that the light of the first wavelength traveling along the first path is incident on the color image sensor array and the light of the second wavelength emanating from the first view travels out of the wavelength selective reflective optics in a direction away from the color image sensor array to thereby prevent the light of the second wavelength emanating from the second view from contributing to the formation of the first image on the color image sensor array.

34. The optical code reader of claim 33, wherein the optical coating is operable to reflect the light of the first wavelength traveling along the first path and to transmit the light of the second wavelength emanating from the first view to divert it from the first path.

35. The optical code reader of claim 33, wherein the optical coating is operable to transmit the light of the first wavelength traveling along the first path and to reflect the light of the second wavelength emanating from the first view to divert if from the first path.

36. The optical code reader of claim 33, wherein:

the optical coating is a first optical coating,

the direction away from the color image sensor array is a first direction, and

the wavelength selective reflective optics include a second optical coating operable to direct along the second path the light of the second wavelength emanating from the second view and to divert from the second path the light of the first wavelength emanating from the second view, the second optical coating positioned so that the light of the second wavelength traveling along the second path is incident on the color image sensor array and the light of the first wavelength emanating from the second view travels out of the wavelength selective reflective optics in a second direction away from the color image sensor array to thereby prevent the light of the first wavelength emanating from the second view from contributing to the formation of the second image on the color image sensor array.

37. The optical code reader of claim 36, wherein the second optical coating is operable to reflect the light of the second wavelength traveling along the second path and to transmit the light of the first wavelength emanating from the second view to divert it from the second path.

38. The optical code reader of claim 32, wherein the wavelength selective reflective optics include a beam splitter.

39. The optical code reader of claim 38, wherein the wavelength selective reflective optics include a dichroic prism.

40. The optical code reader of claim 31, wherein the color image sensor array includes a third set of sensor pixels sensitive to a third wavelength of light, the optics provide for the optical code reader a third view of the object, and the optics operate to form on the color image sensor array a third image of the third view wherein the third image is formed by light of the third wavelength emanating from the third view, the optics substantially excluding from the third image light of the first wavelength emanating from the third view and light of the second wavelength emanating from the third view.

41. The optical code reader of claim 40, wherein the optics include:

a first mirror positioned to provide the first view of the object, the first mirror arranged to direct along a first path the light of the first wavelength emanating from the first view;

a second mirror positioned to provide the second view of the object, the second mirror arranged to direct along a second path the light of the second wavelength emanating from the second view; and

a third mirror positioned to provide the third view of the object, the third mirror arranged to direct along a third path the light of the third wavelength emanating from the third view; and

wavelength selective reflective optics positioned to intersect the first, second, and third paths.

42. The optical code reader of claim 41, wherein the wavelength selective reflective optics include:

a first optical coating operable to direct along the first path the light of the first wavelength emanating from the first view and to divert from the first path at least one of the light of the second wavelength emanating from the first view and light of the third wavelength emanating from the first view, the first optical coating positioned so that the light of the first wavelength traveling along the first path is incident on the color image sensor array and the light diverted from the first path travels out of the wavelength selective reflective optics in a first direction away from the color image sensor array; and

a second optical coating operable to direct along the second path the light of the second wavelength emanating from the second view and to divert from the second path at least one of the light of the first wavelength emanating from the second view and light of the third wavelength emanating from the second view, the second optical coating positioned so that the light of the second wavelength traveling along the second path is incident on the color image sensor array and the light diverted from the second path travels out of the wavelength selective reflective optics in a second direction away from the color image sensor array.

43. The optical code reader of claim 42, wherein at least one of the first and second optical coatings is operable to direct along the third path the light of the third wavelength emanating from the third view and to divert from the third path at least one of the light of the first wavelength emanating from the third view and the light of the second wavelength emanating from the third view.

44. The optical code reader of claim 42, wherein the wavelength selective reflective optics include a trichroic prism.

45. The optical code reader of claim 31, wherein the optical code reader is a multi-window reader.

46. A method of data reading, comprising:

providing an optical code reader having light directing optics and a color image sensor array, the color image sensor array including a first set of sensor pixels sensitive to light of a first wavelength and a second set of sensor pixels sensitive to light of a second wavelength, the light directing optics providing a first view of an object positioned in a read region of the optical code reader and a second view of the object;

directing light emanating from the first view along a first path to the color image sensor array to form a first image of the first view on the color image sensor array, the light emanating from the first view including light of the first wavelength and light of the second wavelength;

directing light emanating from the second view along a second path to the color image sensor array to form a second image of the second view on the color image sensor array, the light emanating from the second view including light of the first wavelength and light of the second wavelength;

diverting from the first path in a first direction away from the color image sensor array the light of the second wavelength emanating from the first view so that the first image substantially excludes the light of the second wavelength emanating from the first view, the light of the first wavelength emanating from the first view continuing to travel along the first path to the color image sensor array to form the first image of the first view on the color image sensor array; and

diverting from the second path in second direction away from the color image sensor array the light of the first wavelength emanating from the second view so that the second image substantially excludes the light of the first wavelength emanating from the second view, the light of the second wavelength emanating from the second view continuing to travel along the second path to the color image sensor array to form the second image of the second view on the color image sensor array.

47. The method of claim 46, further comprising forming the first and second images on the color image sensor array at the same time.

48. The method of claim 46, further comprising:

sensing the first image using the first set of sensor pixels; and

sensing the second image using the second set of sensor pixels.

49. The method of claim 46, wherein the color image sensor array includes a third set of sensor pixels sensitive to light of a third wavelength and the light directing optics provide a third view of the object, further comprising:

directing light emanating from the third view along a third path to the color image sensor array to form a third image of the third view on the color image sensor array, the light emanating from the third view including light of the first wavelength, light of the second wavelength, and light of the third wavelength; and

diverting from the third path the light of the first wavelength emanating from the third view and the light of the second wavelength emanating from the third view so that the third image substantially excludes the light of the first wavelength emanating from the third view and the light of the second wavelength emanating from the third view, the light of the third wavelength emanating from the third view continuing to travel along the third path to the color image sensor array to form the third image of the third view on the color image sensor array.