Edge effect compensating bar code reader

• US 6,119,071 A
• Filed: 06/27/1997
• Issued: 09/12/2000
• Est. Priority Date: 06/28/1996
• Status: Expired due to Fees

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Dolash, Thomas M., Garvey, John J., Gorenflo, Ronald L.
• Primary Examiner(s): ASSOUAD, PATRICK J
• Application Number:
  US08/883,909
• Time in Patent Office: 1,173 Days
• Field of Search: 364/571.07, 235/375, 235/435, 235/454, 235/456, 235/462, 235/463, 235/468, 235/470, 250/483.1, 250/484.2, 250/472.1, 250/473.1, 250/492.1, 382/100, 382/101, 382/102, 382/155, 382/156, 382/173, 382/181, 382/190, 702/85
• US Class Current: 702/85
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1452 detecting bar code edges

Abstract

Apparatus and method for reading a luminescent bar code on a background surface whose reflectance may vary over the coded area, including a light source for providing light to scan, and to excite luminescence in the bar code or to reflect from the background surface of the coded area; a first detector responsive to reflected non-luminescent light for providing a first signal; a second detector responsive to luminescent light for providing a second signal; and memory having stored calibration indicia of reflectance and luminescence, the memory responsive to the first and second signals for providing an output signal substantially independent of background reflectance, and substantially free of bar code edge distortion.

Claims

1. Apparatus for reading a luminescent bar code on a background surface whose reflectance may vary over the coded area, comprising:

a. means for providing light to scan, and to excite luminescence in said bar code and/or to reflect from said background surface of said coded area;

b. means responsive to reflected non-luminescent light for providing a first signal;

c. means responsive to luminescent light for providing a second signal;

d. memory means having stored calibration indicia of reflectance and luminescence, said memory means responsive to said first and second signals for providing a compensated output signal; and

e. means for digital signal processing for providing calibration indicia for said memory means.

2. Apparatus according to claim 1, further comprising:

e. means for interfacing data having said calibration indicia with said memory means.

3. Apparatus according to claim 2, further comprising:

e. means for digital signal processing for providing calibration indicia for said memory means, wherein signals to be processed are obtained through the scanning of calibration cards.

4. Apparatus according to claim 1, wherein said means for digital signal processing further comprises neural network software.

5. Apparatus for reading a luminescent bar code on a background surface whose reflectance may vary over the coded area, comprising:

a. means for providing light to scan, and to excite luminescence in said bar code and/or to reflect from said background surface of said coded area;

b. means responsive to reflected non-luminescent light for providing a first signal;

c. means responsive to luminescent light for providing a second signal;

d. memory means having stored calibration indicia of reflectance and luminescence, said memory means responsive to said first and second signals for providing a compensated output signal; and

wherein said calibration indicia is stored in memory as one or more look-up tables.

6. Apparatus as in claim 5, comprising one or more look-up tables produced by a neural network.

7. Apparatus according to claim 5, wherein said stored calibration indicia of reflectance and luminescence comprises a look-up table configured to obtain a preselected signal of bar code edge information.

8. Apparatus according to claim 5, wherein said means for providing said first, second and output signals comprise digital means.

9. Apparatus according to claim 5, wherein said first, second and output signals are optical or electrical signals.

10. Apparatus according to claim 5, wherein said means for providing said first and second signals comprise means for separating said light into a first wavelength band corresponding to non-luminescent light and a second wavelength band corresponding to said luminescence, and optical means for collecting and focusing light in each wavelength band on separate means for providing separate output signals responsive to said light in each wavelength band.

11. Apparatus according to claim 10, wherein said light separating means comprises light filters.

12. Apparatus according to claim 11, wherein said light separating means comprises a dichroic beam splitter.

13. Apparatus according to claim 5, wherein said means for providing light to excite luminescence in said bar code comprises an ultraviolet light source that is activated briefly prior to scanning said bar code to provide phosphorescence in the material of the bars, and said means for providing light that is reflected without luminescence from said background surface during scanning of said bar code comprises a light source providing light of wavelength in the range of about 600 to 900 nanometers.

14. Apparatus according to claim 5, wherein said light providing means comprises laser means for providing light in the near infrared region that excites a dye in said bar code to fluoresce in a band of wavelengths in the infrared region longer than the wavelength of said excitation light.

15. Apparatus according to claim 5, wherein the same light excites said luminescence and provides said non-luminescent light that is reflected from the background surface.

16. Apparatus for reading a luminescent bar code on a background surface whose reflectance may vary over the coded area, comprising:

a. means for providing light to scan, and to excite luminescence in said bar code and/or to reflect from said background surface of said coded area;

b. means responsive to reflected non-luminescent light for providing a first signal;

c. means responsive to luminescent light for providing a second signal;

d. memory means having stored calibration indicia of reflectance and luminescence, said memory means responsive to said first and second signals for providing a compensated output signal; and

wherein said output signal is substantially compensated for background reflectance and/or substantially free of bar code edge distortion.

17. Apparatus according to claim 16, wherein said means for providing said first and second electrical signals comprise photodetecting means.

18. A calibration card for use with luminescent bar code readers comprising:

a. a substrate;

b. a grey scale applied to a portion of said substrate, wherein said grey scale has increasing or decreasing light absorption characteristics from one end of said gray scale to the other; and

c. a luminescent material applied to a portion of said substrate and to a portion of said grey scale at a plurality of areas of gradually increasing or decreasing light absorption.

19. A calibration card for use with luminescent bar code readers comprising:

a step density card comprising,

a. a substrate;

b. a density wedge applied to said substrate, said density wedge comprising a plurality of light absorbing backgrounds on said substrate wherein each of said light absorbing backgrounds comprises a light absorbing material applied to said substrate, wherein said light absorbing backgrounds are placed substantially adjacent to one another and have a graduated increase in light absorption from one light absorbing background to another;

c. at least one luminescent area on a portion of said substrate and at least one luminescent area on a portion of each of said light absorbing backgrounds, wherein said luminescent area comprises a luminescent material applied to said substrate or said light absorbing material.

20. The step density card according to claim 19, wherein said luminescent area comprises a luminescent bar code.

21. The step density card according to claim 20, wherein said luminescent bar code has substantially the same characteristics as a luminescent bar code to be read by apparatus for reading bar codes with which said step density card is used.

22. The step density card according to claim 19, wherein said luminescent bar code is partially on said light absorbing background and partially on said substrate.

23. A method for reading a luminescent bar code on a background surface and correcting background reflectance to obtain a signal substantially free of bar code edge signal distortion, comprising:

a. providing a beam of light containing at least one predominant frequency band,

b. scanning said beam across said bar code,

c. selectively collecting reflected non-luminescent light in a first frequency band,

d. selectively collecting light in a second frequency band predominantly resulting from luminescence of said bar code,

e. converting said collected light in said first frequency band into a first signal responsive to the reflectance of the background surface,

f. converting said collected light in the second frequency band into a second signal responsive to the amount of luminescent light,

g. providing a compensated output signal corresponding to said first and second signals from a look-up table in memory.

24. A method according to claim 23, wherein said luminescent bar code contains dyes that luminesce in the far red and near infrared region and said light is provided by laser means that simultaneously stimulates luminescence while scanning said bar code to provide reflected light without luminescence responsive to the reflectance of the background surface.

25. A method according to claim 24, wherein said luminescent bar code is substantially transparent and is applied over a visible bar code, and both bar codes are read using the same light source and using separate signal processing means for each bar code.

26. A method according to claim 23, comprising scanning one ore more calibration cards with an apparatus for reading bar codes said apparatus having memory means for storing and accessing a look-up table, converting obtained signals into digital signals, processing said signals to provide calibration indicia for said memory means.

27. A method according to claim 26, comprising obtaining an output signal substantially independent of background reflectance, and substantially free of bar code edge distortion and reader system induced distortion.

28. Apparatus for reading a luminescent bar code on a background surface whose reflectance may vary over the coded area, comprising:

a. light source apparatus to scan, and to excite luminescence in said bar code or to reflect from said background surface of said coded area;

b. non-luminescent light detector apparatus responsive to non-luminescent light for providing a first signal;

c. luminescent light detector apparatus responsive to luminescent light for providing a second signal;

d. random access memory apparatus having stored calibration indicia of reflectance and luminescence, said memory means responsive to said first and second signals for providing a compensated output signal.

29. Apparatus according to claim 28, further comprising:

e. electronic interface circuitry interfacing said calibration indicia with said memory means.

30. Apparatus according to claim 28, further comprising:

e. digital signal processor for providing calibration indicia for said memory means.

31. Apparatus according to claim 30, further comprising:

e. digital signal processor that provides calibration indicia for said memory means, wherein signals to be processed are obtained through the scanning of calibration cards with said apparatus.

32. Apparatus according to claim 28, wherein a look-up table is configured in said random access memory to obtain a linearized signal of bar code edge information.

33. Apparatus according to claim 28 wherein calibration indicia is stored in random access memory as a look-up table, said first and second signals are used to access said look-up table, said random access memory providing an output signal in response to said first and second signals.

34. Apparatus according to claim 28, wherein a look-up table in random access memory is configured from a neural network to provide signal compensation data for a multitude of bar code, substrate, background, and/or apparatus variations.

35. Apparatus according to claim 28, wherein said first, second and output signals are optical or electrical signals.

36. Apparatus according to claim 28, wherein said output signal is substantially compensated for background reflectance and/or substantially free of bar code edge distortion.

37. Apparatus according to claim 30, wherein said digital signal processor is loaded with neural network software.