Spectral scanner employing light paths of multiple wavelengths for scanning objects, such as bar code symbols, and associated method

• US 6,345,765 B1
• Filed: 06/30/2000
• Issued: 02/12/2002
• Est. Priority Date: 06/30/2000
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: Wiklof, Christopher A.
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US09/608,999
• Time in Patent Office: 592 Days
• Field of Search: 235/454, 235/472.01, 235/469
• US Class Current: 235/472.01
• CPC Class Codes: G06K 7/10613 by rotation, e.g. polygon
• CPC Class Codes: G06K 7/10623 Constructional details
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks

Abstract

An optical system, such as a bar code scanner, illuminates an image with a multi-wavelength device. Under a first embodiment, a tunable laser is optically coupled with a prism or other wavelength separation device. As the laser beam wavelength varies, the transmission path through the prism changes, resulting in a scanning of the beam across an image. A photodetector captures light reflected from the image and sends it to a microprocessor for decoding. Under another embodiment, a broad band light source transmits light through a prism, thus shining a “rainbow” on the image. A spectrometer measures reflected light as a function of wavelength and sends the resultant signal to a microprocessor for decoding. Neither embodiment relies on moving parts to scan the image.

Claims

1. A reader for reading a bar code symbol, comprising:

a housing;

a light source at least partially retained by the housing and projecting light of a plurality of wavelengths therefrom;

a prism positioned with respect to the housing to receive the light from the light source and produce a plurality of paths of light based on the plurality of wavelengths of the light, wherein the plurality of paths of light impinge on the bar code symbol external to the housing;

at least one light detector secured to the housing that receives light reflected from the bar code symbol and produces an output signal based on the light reflected from the bar code symbol, wherein the light reflected from the bar code symbol represents bars and spaces in the bar code symbol and the plurality of wavelengths of the light; and

a microprocessor coupled to the light source and the light detector that receives the output signal from the light detector and decodes the bar code symbol based on the output signal.

2. The reader of claim 1 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths ranging from amber to red colors based on an input signal produced by the reader, and wherein the prism deflects the laser beam along the plurality of paths of light based on the plurality of wavelengths of the laser beam, and

wherein the reader includes an automatic gain control circuit coupled to the light detector and the microprocessor, wherein the control circuit automatically normalizes the output signal despite fluctuations in the output signal based on differences in output verses wavelength for the tunable laser or light detector.

3. The reader of claim 1 wherein the photodetector is a spectrometer, wherein the light source is a broadband light source that produces light over a range of wavelengths, and wherein the prism is configured or includes optics to produce adjacent bands of light having different wavelengths, wherein each band is approximately alignable to be coincident with one of the bars or spaces of the bar code symbol.

4. The reader of claim 1 wherein the housing is sized and configured to be hand-held and wherein the reader includes a trigger switch secured to the housing, coupled to the microprocessor and configured to activate the reader upon actuation thereof.

5. A reader for reading a symbol, comprising:

a light source producing light of a plurality of wavelengths;

a wavelength separation device positioned and configured to receive the light from the light source and produce a plurality of paths of light based on the plurality of wavelengths of the light, wherein the plurality of paths of light impinge on the symbol;

at least one light detector positioned and configured to receive light reflected from the symbol and produce an output signal based on the light reflected from the symbol; and

a processor coupled to the light source and coupled to the light detector, wherein the processor receives the output signal from the light detector and analyzes the symbol based on the output signal.

6. The reader of claim 5 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal, and wherein the wavelength separation device deflects the laser beam along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

7. The reader of claim 5, further comprising an automatic gain control circuit coupled to the light detector and the processor, wherein the control circuit automatically adjusts the output signal despite fluctuations in the output signal based on differences in output verses wavelength for the light source or the light detector.

8. The reader of claim 5 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal produced by the reader, and wherein the wavelength separation device is a plurality of prisms constructed and positioned in a cascaded arrangement to deflect the light along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

9. The reader of claim 5 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal, and wherein the wavelength separation device is an acousto-optic modulator coupled to the processor that deflects the laser beam along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

10. The reader of claim 5 wherein the light detector is a spectrometer.

11. The reader of claim 5 wherein the light source is a broadband light source that produces light over a range of wavelengths, and wherein the reader includes optics configured to produce adjacent bands of light having different wavelengths.

12. The reader of claim 5 wherein the light source is a broadband light source that produces light over a range of wavelengths, and wherein the apparatus includes a filter that produces light having a plurality of wavelengths ranging from amber to red colors.

13. The reader of claim 5, further comprising optics to direct the plurality of paths of light along a first axis with respect to the symbol, and wherein the reader further comprises a light deflector to deflect the paths of light along a second axis differing from the first axis.

14. The reader of claim 5 wherein the symbol is a machine-readable symbol having a plurality of elements encoding information, and wherein the processor is configured to find elements in the symbol based on the output signal to identify and decode the information encoded by the elements of the symbol.

15. The reader of claim 5 wherein the symbol is a machine-readable symbol having a plurality of elements encoding information, and wherein the processor is configured to process the output signal to enhance identification of the elements of the symbol within the output signal.

16. The reader of claim 5, further comprising a housing is sized and configured to be hand-held and wherein the reader includes a trigger switch secured to the housing, coupled to the processor and configured to activate the reader upon actuation thereof.

17. The reader of claim 5 wherein the light source is a tunable laser, and wherein the reader further comprises a beam deflection optical element configured to provide a folded optical path for a laser beam produced by the tunable laser.

18. An apparatus for imaging a symbol, comprising:

a light source producing light of a plurality of wavelengths;

a wavelength separation device positioned and configured to receive the light from the light source and produce a plurality of paths of light based on the plurality of wavelengths of the light, wherein the plurality of paths of light impinge on the symbol; and

at least one light detector positioned and configured to receive light reflected from the symbol and produce an output signal based on the light reflected from the symbol.

19. The apparatus of claim 18 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal and wherein the wavelength separation device deflects the laser beam along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

20. The apparatus of claim 18, further comprising an automatic gain control circuit coupled to the light detector, wherein the control circuit automatically adjusts the output signal despite fluctuations in the output signal based on differences in output verses wavelength for the light source or the light detector.

21. The apparatus of claim 18 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal produced by the apparatus, and wherein the wavelength separation device is a plurality of prisms constructed and positioned in a cascaded arrangement to deflect the light along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

22. The apparatus of claim 18 wherein the light source is a tunable laser that provides a laser beam having a plurality of wavelengths based on an input signal, and wherein the wavelength separation device is an acousto-optic modulator that deflects the laser beam along the plurality of paths of light based on the plurality of wavelengths of the laser beam.

23. The apparatus of claim 18 wherein the light detector is a spectrometer.

24. The apparatus of claim 18 wherein the light source is a broadband light source that produces light over a range of wavelengths, and wherein the apparatus includes optics configured to produce adjacent bands of light having different wavelengths.

25. The apparatus of claim 18 wherein the light source is a broadband light source that produces light over a range of wavelengths, and wherein the apparatus includes a filter that produces light having a plurality of wavelengths ranging from amber to red colors.

26. The apparatus of claim 18, further comprising optics to direct the plurality of paths of light along a first axis with respect to the symbol, and wherein the apparatus further comprises a light deflector to deflect the paths of light along a second axis differing from the first axis.

27. A method of reading a machine-readable symbol representing encoded information, the method comprising:

producing light of a plurality of wavelengths;

projecting a plurality of paths of light based on the plurality of wavelengths of the light, wherein the plurality of paths of light project onto the symbol;

producing an output signal based on the plurality of wavelengths of the light reflected from the symbol; and

decoding the symbol based on the output signal.

28. The method of claim 27 wherein producing light includes producing a laser beam having a plurality of wavelengths changeable based on an input signal.

29. The method of claim 27, further comprising automatically normalizing the output signal despite fluctuations in the output signal based on differences in output verses wavelength for the light.

30. The method of claim 27 wherein the symbol is a machine-readable symbol having a plurality of elements encoding information, and wherein the method further comprises finding elements in the symbol based on the output signal to identify and decode the information encoded by the elements of the symbol.

31. The method of claim 27 wherein the symbol is a machine-readable symbol having a plurality of elements encoding information, and wherein the method further comprises process enhancing identification of the elements of the symbol within the output signal.

32. The method of claim 27 wherein producing an output signal includes measuring an intensity of each wavelength of light reflected from the symbol.

33. The method of claim 27 wherein producing light includes producing broadband light over a range of wavelengths, and wherein projecting includes projecting adjacent bands of light having different wavelengths on the symbol.

34. The method of claim 27 wherein projecting includes directing the plurality of paths of light along a first axis with respect to the symbol, and wherein the method further comprises deflecting the paths of light along a second axis differing from the first axis.

35. The method of claim 27, further comprising folding the produced light.

36. A method of imaging an object, the method comprising:

producing light of a plurality of wavelengths;

projecting a plurality of paths of light based on the plurality of wavelengths of the light, wherein the plurality of paths of light project onto the object;

producing an output signal based on the plurality of wavelengths of the light reflected from the symbol; and

analyzing the object based on the output signal.

37. The method of claim 36 wherein producing light includes producing a laser beam having a plurality of wavelengths changeable based on an input signal.

38. The method of claim 36, further comprising automatically normalizing the output signal despite fluctuations in the output signal based on differences in output verses wavelength for the light.

39. The method of claim 36 wherein the object is a machine-readable symbol having a plurality of elements encoding information, and wherein the method further comprises finding elements in the symbol based on the output signal to identify and decode the information encoded by the elements of the symbol.

40. The method of claim 36 wherein producing an output signal includes measuring an intensity of each wavelength of light reflected from the object.

41. The method of claim 36 wherein producing light includes producing broadband light over a range of wavelengths, and wherein projecting includes projecting adjacent bands of light having different wavelengths on the object.

42. The method of claim 36 wherein projecting includes directing the plurality of paths of light along a first axis with respect to the object, and wherein the method further comprises deflecting the paths of light along a second axis differing from the first axis.

43. The method of claim 36, further comprising providing a folded optical path for the produced light.