Method and apparatus for reading optical indicia

• US 8,701,999 B2
• Filed: 05/02/2008
• Issued: 04/22/2014
• Est. Priority Date: 05/02/2008
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Vinogradov, Igor R., Barkan, Edward
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US12/114,334
• Publication Number:
  US 20090272804A1
• Time in Patent Office: 2,181 Days
• Field of Search: 235/438, 235/439, 235/454, 235/455, 235/462.01, 23546241- 49, 358/401, 358/406, 358/443
• US Class Current: 235/455
• CPC Class Codes: G06K 2207/1018 Source control
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10752 Exposure time control

Abstract

A method and apparatus for reading optical indicia. The method includes generating calibration light, and measuring an intensity of the calibration light reflected into a detector system. The method also includes determining an optimum exposure level for the imaging system based on the measured intensity of the calibration light reflected into the detector system, and generating an illumination light with an illumination system. In addition, the method includes capturing an image of the optical indicia with the imaging system subjecting to the optimum exposure level.

Claims

1. A method of reading optical indicia on a surface of an object comprising:

generating a calibration light from an illumination source with an illumination system for determining an optimum exposure level of an imaging system that takes into account a reflectivity of the surface of the object when a measured intensity of ambient light is lower than a predetermined value;

measuring an intensity of the calibration light reflected into a detector system;

determining the optimum exposure level of the imaging system based on the measured intensity of the calibration light reflected into the detector system;

generating an illumination light from the illumination source with the illumination system; and

capturing an image of the optical indicia with the imaging system subjecting to the optimum exposure level while the optical indicia is illuminated by the illumination light from the illumination source.

2. The method of claim 1, further comprising:

measuring the ambient light with the detector system.

3. The method of claim 1, wherein the generating calibration light comprises:

generating the calibration light with the illumination system.

4. The method of claim 1, wherein the generating calibration light comprises:

generating the calibration light with a calibration illumination system.

5. The method of claim 1, wherein the generating calibration light comprises:

generating the calibration light modulated at a modulation frequency.

6. The method of claim 5, wherein the measuring an intensity of the calibration light comprising:

detecting the reflected calibration light to generate an electrical signal having an amplitude depending upon the intensity of the reflected calibration light from the object of interest being detected; and

passing the generated electrical signal through a band pass filter having a pass band including the modulation frequency.

7. The method of claim 1, wherein the measuring an intensity of the calibration light comprising:

passing the reflected calibration light through an optical filter to incident upon a photodetector.

8. The method of claim 1, wherein the generating an illumination light comprises:

generating a pulsed illumination light having intensity at lest two times larger than the average intensity of the calibration light.

9. The method of claim 1, wherein the determining an optimum exposure level comprises:

determining an optimum exposure time.

10. The method of claim 9, wherein the generating an illumination light comprises:

generate an illumination light with an illumination system during the determined optimum exposure time.

11. A method of reading optical indicia on a surface of an object with comprising:

generating a calibration light from an illumination source with an illumination system for determining an optimum exposure level of an imaging system that takes into account a reflectivity of the surface of the object;

measuring an intensity of the calibration light reflected into a detector system;

determining the optimum exposure level of the imaging system based on the measured intensity of the calibration light reflected into the detector system;

generating an illumination light from the illumination source with the illumination system; and

capturing an image of the optical indicia with the imaging system subjecting to the optimum exposure level while the optical indicia is illuminated by the illumination light from the illumination source.

12. The method of claim 11, wherein the generating calibration light comprises:

generating the calibration light with the illumination system.

13. The method of claim 11, wherein the generating calibration light comprises:

generating the calibration light with a calibration illumination system.

14. The method of claim 11, wherein the generating calibration light comprises:

generating the calibration light modulated at a modulation frequency.

15. The method of claim 14, wherein the measuring an intensity of the calibration light comprising:

detecting the reflected calibration light to generate an electrical signal having an amplitude depending upon the intensity of the reflected calibration light from the object of interest being detected; and

passing the generated electrical signal through a band pass filter having a pass band including the modulation frequency.

16. An imaging scanner for reading an optical indicia comprising:

an illumination system having at least two operation modes, wherein the illumination system in the first operation mode generates a calibration light from an illumination source, and the illumination system in the second operation mode generates an illumination light from the illumination source;

a detector system operable to measure intensity of the calibration light reflected into the detector system; and

an imaging system including an imaging sensor and having a first lens system defining a first field of view, wherein the imaging system is configured to capture an image of the optical indicia with an optimum exposure level that is determined based on the measured intensity of the calibration light reflected into the detector system.

17. The imaging scanner of claim 16, wherein the detector system comprises a second lens system defining a second field of view substantially overlap with the first field of view of the imaging system.

18. The imaging scanner of claim 16, wherein the detector system comprises an optical filter configured to filter light detected by the detector, wherein the optical filter has photo sensitivity spectrum substantially overlaps with the photo sensitivity spectrum of the imaging sensor.

19. The imaging scanner of claim 16, wherein the illumination system in the first operation mode generates a calibration light modulated at a modulation frequency.

20. The imaging scanner of claim 19, wherein the detector system comprises a photodetector having an output coupled to a band pass filter, wherein the band pass filter has a pass band including the modulation frequency.

21. The imaging scanner of claim 16, wherein the illumination system in the second operation mode generates a pulsed illumination light having intensity at least two times larger than the average intensity of the calibration light.

22. The imaging scanner of claim 16, further comprising:

a filter for ambient light coupled between the detector system and the imaging system.

23. The imaging scanner of claim 16, further comprising:

a filter for calibration light coupled between the detector system and the imaging system.

24. The imaging scanner of claim 16, further comprising:

a scan engine chassis having the illumination system, the detector system, and the imaging system mounted thereon.

25. The imaging scanner of claim 24, further comprising:

a portable enclosure having the scan engine chassis installed therein.

26. The imaging scanner of claim 24, further comprising:

a stationary enclosure having the scan engine chassis installed therein.

27. The imaging scanner of claim 16, further comprising:

a portable enclosure having the illumination system, the detector system, and the imaging system installed therein.

28. The imaging scanner of claim 16, further comprising:

a stationary enclosure having the illumination system, the detector system, and the imaging system installed therein.