Optical scanning head

• US 5,354,977 A
• Filed: 10/23/1992
• Issued: 10/11/1994
• Est. Priority Date: 02/27/1992
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Alex Roustaei
• Inventors: Roustaei, Alex
• Primary Examiner(s): SHEPPERD, JOHN W
• Application Number:
  US07/965,991
• Time in Patent Office: 718 Days
• Field of Search: 235/462, 235/472, 250/553
• US Class Current: 235/462.11
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10742 including a diffuser for diffusing the light from the light source to create substantially uniform illumination of the target record carrier
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning

Abstract

The optical scanning head for scanning one- and two-dimensional bar codes includes at least one combination of light emitting diodes arranged so the LEDs emit light at different angles to create a fan of light. The combination and arrangement of the LEDs depends on whether one- or two-dimensional bar codes are to be read. A cylindrical lens optimizes the light impinging upon the bar code. An optical module includes a light shield or "dark room" and a lens/filter assembly which focusses reflected light on the detector, made up of a CCD module for detecting the light intensity in the reflected beam over a field of view across a bar code symbol. One or more combinations of linear CCD arrays in the CCD module generate an electrical signal indicative of the detected light intensity. A trigger mechanism allows selection of the number of LEDs or linear CCD arrays to efficiently scan one- or two-dimensional bar codes, where two-dimensional bar codes require more illumination for accurate scanning.

Claims

1. An optical scanning device for scanning one- and two-dimensional bar codes comprising:

a printed circuit board having a front and a rear;

an LED array having a plurality of LEDs disposed near said front of said printed circuit board wherein each LED of said plurality is oriented to emit light at an angle different than other LEDs of said plurality, said angle of each LED being a non-zero angle with respect to a reference line perpendicular to said front of said circuit board, said LED array projecting a fan of light forward in a direction along said reference line;

a cylindrical lens forward of said LED array having and input edge and an output edge for focussing said fan of light into a line of light at its focal distance for illuminating a bar code within a field of view within a range of said focal distance so that reflected light is reflected therefrom;

a detector comprising at least one linear CCD array disposed near rearward of said LED array on said printed circuit board for detecting a portion of reflected light from said bar code and generating an electrical signal in response thereto wherein said electrical signal is an analog representation of said bar code;

an optical assembly for receiving said reflected light and directing said reflecting light onto said detector;

a conversion assembly for converting said electrical signal into a signal corresponding to said bar code; and

a voltage source for providing a driving voltage to said LED array, said CCD detector and said conversion assembly.

2. An optical scanning device as in claim 1 wherein said LED array is arranged in a "V"-shape.

3. An optical scanning device as in claim 1 wherein said LED array is arranged in a generally linear fashion.

4. An optical scanning device as in claim 1 wherein said LED array is arranged in two discrete rows of LEDs.

5. An optical scanning device as in claim 4 wherein said two discrete rows are each parallel to said front of said printed circuit board.

6. An optical scanning device as in claim 4 wherein said two discrete rows are substantially perpendicular to said front of said printed circuit board.

7. An optical scanning device as in claim 1 wherein said LED array is arranged in a vertical plane perpendicular to said printed circuit board.

8. An optical scanning device as in claim 1 wherein said LED array comprises at least two groupings of LEDS, each grouping having an equal number of LEDs, and further comprising:

a clocking device for controlling a transfer of driving voltage from said voltage source to each grouping of LEDs wherein a first grouping of LEDs remains on and at least one second grouping of LEDs is periodically turned on and off according to a clocking signal generated by said clocking device.

9. An optical scanning device as in claim 8 wherein said clocking device further controls a timing of scanning by said CCD detector and transfer of said electrical signal from said CCD detector to said conversion assembly.

10. An optical scanning device as in claim 1 further comprising:

a clocking device for controlling transfer of driving voltage from said voltage source to said at least one grouping of LEDs; and

a gain controller responsive to a level of said electrical signal for controlling a level of driving voltage applied to said at least one grouping of LEDs.

11. An optical scanning device as in claim 10 wherein said gain controller ramps up said level of said driving voltage when said optical scanning device is at a greater distance from said bar code.

12. An optical scanning device as in claim 1 wherein said field of view has a depth in the range of 0 to 22 inches.

13. An optical scanning device as in claim 1 wherein said input edge of said cylindrical lens has a knurled surface.

14. An optical scanning device as in claim 13 wherein said output edge of said cylindrical lens is concave.

15. An optical scanning device as in claim 13 wherein said output edge of said cylindrical lens is convex.

16. An optical scanning device as in claim 1 wherein said output edge of said cylindrical lens has a double radius wherein a first portion of said output edge has a first focal length and a second portion of said output edge has a second focal length different from said first focal length.

17. An optical scanning device as in claim 1 wherein said detector comprises two parallel linear CCD arrays.

18. An optical scanning device as in claim 1 wherein said detector comprises an area array of CCDs.

19. An optical scanning device as in claim 1 wherein said optical assembly comprises a plurality of lenses and filters for collecting and optimizing said reflected light for detection by said detector.

20. An optical scanning device as in claim 19 wherein said optical assembly further comprises a spatial filter having at least one air slit.

21. An optical scanning device as in claim 20 wherein said spatial filter has two crossed slits.

22. An optical scanning device as in claim 1 wherein said conversion assembly includes an automatic gain control for amplifying said electrical signal when a level of said electrical signal falls below a pre-determined level.

23. An optical scanning device as in claim 1 wherein said conversion assembly includes an automatic comparator control.

24. An optical scanning device as in claim 1 further comprising a light shield for blocking stray light from said optical assembly.

25. An optical scanning device as in claim 1 wherein a housing retains components of said optical scanning device, said housing having a configuration to be held in a user'"'"'s hand so that said fan of light is directed towards said bar code.

26. An optical scanning device as in claim 1 wherein said conversion assembly includes an analog-to-digital converter and an microprocessor for manipulating said electrical signal.

27. An optical scanning device as in claim 1 further comprising an electronic shutter for periodically blocking light from impinging upon said detector when one of said optical scanning device and said bar code is in motion with respect to the other.

28. An optical scanning device as in claim 1 further comprising a memory buffer for storing an electronic image of a two-dimensional bar code.

29. An optical scanning device as in claim 1 further comprising a signal converter having a dark reference for calibration of said electrical signal.

30. An optical scanning device as in claim 29 further comprising a flat field for comparison with said dark reference to provide shading correction.

31. An optical scanning device as in claim 1 wherein said CCD detector includes an anti-blooming device to decrease excess charges caused by overillumination.

32. An optical scanning device as in claim 1 wherein said CCD detector includes a pixel defect corrector.

33. An optical scanning device as in claim 1 wherein said CCD detector includes a binning means for enhancing a depth of field of said optical scanning device.

34. An optical scanning device as in claim 1 wherein said conversion assembly includes a gain control means for controlling an amplitude of said electrical signal.

35. An optical scanning device as in claim 1 wherein said conversion assembly includes means for highly adaptive thresholding.

36. An optical scanning device as in claim 1 wherein said conversion assembly includes a multi-pole active filter.

37. An optical scanner for reading and decoding information encoded in one-dimensional and/or two-dimensional bar codes comprising alternating lines of light and dark, said optical scanner comprising:

a printed circuit board having a front, a center and a rear;

an array of light emitting diodes comprising at least one combination of light emitting diodes disposed near said front of said printed circuit board in an arrangement wherein each light emitting diode of said at least one combination emits light at an angle different from other light emitting diodes of said at least one combination so that a fan of light is projected from said array along a line perpendicular to said front of said printed circuit board;

a cylindrical lens having an input edge and an output edge disposed forward of said array of light emitting diodes for focussing said fan of light into a line of light at its focal distance onto a reference plane within a field of view containing said bar code so that light is reflected therefrom;

an optical assembly disposed at a center of said printed circuit board for receiving, concentrating and directing reflected light toward said rear of said board;

a CCD array disposed at said rear of said printed circuit board for detecting a portion of said reflected light directed thereon by said optical assembly and generating an analog representation of said bar code;

a conversion assembly for receiving and converting said analog representation into an electrical signal corresponding to said bar code; and

a voltage source for providing a driving voltage to said array of light emitting diodes, said CCD array and said conversion assembly.

38. An optical scanner as in claim 37 wherein said array of light emitting diodes comprises at least two combinations of light emitting diodes and further comprising:

a clocking device for controlling a transfer of driving voltage from said voltage source to each combination of light emitting diodes wherein a first said combination remains on when said optical scanner is activated and at least one second said combination is periodically turned on and off according to a clocking signal generated by said clocking device.

39. An optical scanner as in claim 38 wherein said clocking device further controls a timing of scanning of said CCD array and a transfer of said analog representation to said conversion assembly.

40. An optical scanner as in claim 37 further comprising:

a clocking device for controlling transfer of driving voltage from said voltage source to said at least one combination of light emitting diodes; and

a gain controller responsive to a level of said electrical signal for controlling a level of driving voltage applied to said at least one combination of light emitting diodes.

41. An optical scanner device as in claim 40 wherein said gain controller ramps up said level of said driving voltage when said optical scanner is at a greater distance from said bar code.

42. An optical scanner as in claim 37 wherein said field of view has a depth in the range of 0 to 22 inches.

43. An optical scanning device as in claim 37 wherein said input edge of said cylindrical lens has a knurled surface.

44. An optical scanning device as in claim 43 wherein said output edge of said cylindrical lens is concave.

45. An optical scanning device as in claim 43 wherein said output edge of said cylindrical lens is convex.

46. An optical scanning device as in claim 37 wherein said output edge of said cylindrical lens has a double radius wherein a first portion of said output edge has a first focal length and a second portion of said output edge has a second focal length different from said first focal length.

47. An optical scanning device as in claim 37 wherein said CCD array comprises two parallel rows of CCDs.

48. An optical scanning device as in claim 37 wherein said CCD array comprises an area array of CCDs.

49. An optical scanner as in claim 37 wherein said array of light emitting diode is disposed in a generally V-shaped arrangement.

50. An optical scanner as in claim 37 wherein said array of light emitting diodes is disposed in at least one generally straight row across said front of said printed circuit board.

51. An optical scanner as in claim 37 wherein said array of light emitting diodes is disposed in two rows perpendicular to said front of said printed circuit board.

52. An optical scanner as in claim 37 wherein said optical assembly comprises a plurality of lenses and filters for optimizing said reflected light for detection by said CCD array.

53. An optical scanner as in claim 52 wherein said optical assembly includes a bandpass filter for blocking light having a wavelength outside of a range around a predetermined wavelength at which said array of light emitting diodes emits.

54. An optical scanner as in claim 37 wherein each light emitting diode of said array emits visible red light.

55. An optical scanner as in claim 54 wherein said visible red light has a wavelength of 660 nanometers.

56. An optical scanner as in claim 37 wherein each light emitting diode of said array emits infrared light.

57. An optical scanner as in claim 37 wherein said conversion assembly includes an automatic gain control for controlling gain in response to a detected intensity level of said reflected light.

58. An optical scanner as in claim 37 wherein said optical assembly further comprises a light shield to block out stray light.

59. An optical scanner as in claim 37 wherein said optical assembly is slidable in a direction running from said front to said rear of said printed circuit board to permit variation in a depth of field of said optical scanner.

60. An optical scanner as in claim 37 wherein said CCD array has a density of elements selected according to a density of said alternating lines of said bar code.

61. An optical scanner as in claim 37 wherein said fan of light has an intensity distribution which is denser at a center of said fan.

62. An optical scanner as in claim 37 further comprising a housing for hand-held operation.

63. An optical scanner as in claim 37 further comprising a trigger for activating and de-activating said optical scanner.

64. An optical scanner as in claim 63 wherein said trigger comprises a dual trigger for selecting one-dimensional or two-dimensional scanning.

65. An optical scanner as in claim 37 wherein said conversion assembly includes a memory buffer for storing an electronic image of a two-dimensional bar code.

66. An optical scanner as in claim 37 wherein said conversion assembly includes a dark reference for calibration of said electrical signal.

67. An optical scanner as in claim 66 further comprising a flat field for comparison with said dark reference to provide shading correction.

68. An optical scanner as in claim 37 wherein said conversion assembly includes an anti-blooming device to decrease excess charges in said CCD array caused by overillumination.

69. An optical scanner as in claim 37 wherein said conversion assembly includes a pixel defect corrector.

70. An optical scanner as in claim 37 wherein said conversion assembly includes a binning means for enhancing a depth of field of said optical scanning head.

71. An optical scanner as in claim 37 wherein said conversion assembly includes a gain control means for controlling an amplitude of said electrical signal.

72. An optical scanner as in claim 37 further comprising a signal conditioning means having highly adaptive thresholding.

73. An optical scanning head as in claim 37 wherein said conversion assembly includes a multi-pole active filter.

74. An optical scanning head for inclusion in a bar code scanning system for scanning one-dimensional and two-dimensional bar codes comprising:

a printed circuit board having a front, a center and a rear portion;

an LED array disposed at said front portion of said printed circuit board for projecting a reference fan of light, each LED of said array being oriented to emit light at an angle different from other LEDs in said array;

a cylindrical lens having an input edge and an output edge for focussing said reference fan of light at its focal distance for illuminating a bar code within a field of view to be read so that light is reflected therefrom;

a CCD module disposed rearward on said printed circuit board having a CCD array for detecting a portion of reflected light from said bar code and generating an electrical signal in response thereto wherein said electrical signal is an analog representation of said bar code; and

an optical assembly for receiving said reflected light and directing said reflecting light onto said CCD module.

75. An optical scanning head as in claim 74 wherein said LED array is disposed in a generally V-shaped arrangement.

76. An optical scanning head as in claim 74 wherein said LED array is disposed in at least one generally linear arrangement.

77. An optical scanning head as in claim 76 wherein said LED array comprises two parallel linear arrangements parallel to said front of said printed circuit board.

78. An optical scanning head as in claim 76 wherein said LED array comprises two parallel linear arrangements perpendicular to said front of said printed circuit board.

79. An optical scanning head as in claim 74 wherein said optical assembly comprises a plurality of lenses and filters for collecting and optimizing said reflected light for detection by said CCD module.

80. An optical scanning head as in claim 74 wherein said input edge of said cylindrical lens has a knurled surface.

81. An optical scanning head as in claim 74 wherein said output edge of said cylindrical lens is concave.

82. An optical scanning head as in claim 74 wherein said output edge of said cylindrical lens is convex.

83. An optical scanning head as in claim 74 wherein said output edge of said cylindrical lens has a first radius and a second radius, each having a different focal length.

84. An optical scanning head as in claim 74 further comprising a light shield for blocking stray light from said optical assembly.

85. An optical scanning head as in claim 74 further comprising means for combining said optical scanning head with other optical scanning heads so that a bar code can be read at a number of different orientations.

86. An optical scanning head as in claim 74 further comprising an electronic shutter for periodically preventing charge from collecting in said CCD module when one of said optical scanning device and said bar code is in motion with respect to the other.

87. An optical scanning head as in claim 74 further comprising a memory buffer for storing an electronic image of a two-dimensional bar code.

88. An optical scanning head as in claim 74 further comprising a signal converter having a dark reference for calibration of said electrical signal.

89. An optical scanning head as in claim 88 further comprising a flat field for comparison with said dark reference to provide shading correction,

90. An optical scanning head as in claim 74 wherein said CCD module includes an anti-blooming device to decrease excess charges caused by overillumination.

91. An optical scanning head as in claim 74 wherein said CCD module includes a pixel defect corrector,

92. An optical scanning head as in claim 74 wherein said CCD module includes a binning means for enhancing a depth of field of said optical scanning head.

93. An optical scanning head as in claim 74 wherein said CCD module includes a gain control means for controlling an amplitude of said electrical signal.

94. An optical scanning head as in claim 74 further comprising a signal conditioning means having highly adaptive thresholding,

95. An optical scanning head as in claim 74 further comprising a signal converter having a multi-pole active filter.

96. An optical scanning head as in claim 79 wherein said optical assembly further comprises a spatial filter having at least one air slit.

97. An optical scanning head as in claim 79 wherein said spatial filter has two crossed slits.