High-resolution optical code imaging using a color imager

• US 8,118,226 B2
• Filed: 02/11/2010
• Issued: 02/21/2012
• Est. Priority Date: 02/11/2009
• Status: Active Grant

• Current Assignee: Datalogic Adc, Inc. (Datalogic S.p.A.)
• Original Assignee: Datalogic Scanning Incorporated (Datalogic S.p.A.)
• Inventors: Olmstead, Bryan L., Shearin, Alan
• Primary Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US12/704,313
• Publication Number:
  US 20100200658A1
• Time in Patent Office: 740 Days
• Field of Search: 235/455, 235/462.01, 235/462.09, 235/462.21, 235/462.42, 235/470
• US Class Current: 235/455
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks

Abstract

An optical code or other data reading device includes a color image sensor array positioned to sense light reflected from an object, and to produce image data. In one configuration, the color image sensor array has multiple sets (e.g., first and second sets) of sensor elements that are sensitive to corresponding visible wavelength bands of light (e.g., first and second wavelength bands), the sets also being sensitive to light within an infrared wavelength band. An artificial illumination source is positioned to illuminate the field of view with light that is reflected off an object in the field of view toward the image sensor array, the illumination source being operable to produce infrared light having wavelengths within the infrared wavelength band so that, upon illumination, at least some sensor elements of each of the sets are sensitive to the infrared light and contribute to production of the image data.

Claims

1. A method of imaging an object in a field of view of an optical code reading device, the optical code reading device having a color image sensor array, the method comprising:

illuminating the field of view of the optical code reading device with artificial infrared light that is incident upon the object, thereby producing reflected infrared light, the reflected infrared light having wavelengths within an infrared wavelength band;

sensing the reflected infrared light with a first set of sensor elements of the color image sensor array, the first set of sensor elements being sensitive to the infrared light and to visible light having wavelengths within a first visible wavelength band;

sensing the reflected infrared light with a second set of sensor elements of the color image sensor array, the second set of sensor elements being sensitive to the infrared light and to visible light having wavelengths within a second visible wavelength band different from the first visible wavelength band; and

producing image data from the first and second sets of sensor elements, the image data being derived from the infrared light sensed by the first and second sets of sensor elements and representing a high-resolution infrared image of the object.

2. A method according to claim 1, further comprising:

sensing the reflected infrared light with a third set of sensor elements of the color image sensor array, the third set of sensor elements being sensitive to the infrared light and to visible light having wavelengths within a third visible wavelength band different from each of the first and second visible wavelength bands; and

producing the image data from the first, second and third sets of sensor elements, the image data being derived from the infrared light sensed by the first, second and third sets of sensor elements.

3. A method according to claim 2, wherein the resolution of the infrared image represented by the image data is substantially equal to a resolution produced by a monochrome image sensor array having the same number of sensor elements as the sum of the numbers of sensor elements in the first, second and third sets of sensor elements.

4. A method according to claim 2, wherein the first, second and third visible wavelength bands correspond to the colors red, green and blue.

5. A method according to claim 1, wherein the infrared wavelength band includes 850 nm.

6. A method according to claim 1, wherein upon illumination of the field of view, sensor elements of each of the first and second sets of sensor elements are sensitive to the infrared light to a sufficiently equal extent such that an average intensity value of light sensed by the first set of sensor elements is substantially equal to an average intensity value of light sensed by the second set of sensor elements.

7. A method according to claim 1, further comprising:

intermittently blocking the reflected infrared light from reaching the sensor elements of the first and second sets by a mechanical shutter.

8. An optical code reading device comprising:

a color image sensor array positioned to sense light reflected from an object in a field of view of the optical code reading device and to produce from the sensed reflected light image data representing an infrared image of the object, the color image sensor array comprising;

a first set of sensor elements that are sensitive to a first visible wavelength band of light, and

a second set of sensor elements that are sensitive to a second visible wavelength band of light, wherein the first and second sets of sensor elements are sensitive to light within an infrared wavelength band; and

an artificial illumination source positioned to illuminate the field of view of the optical code reading device with light that is incident upon and reflected from the object in the field of view toward the color image sensor array, the artificial illumination source being operable to produce infrared light having a wavelength within the infrared wavelength band so that, upon illumination of the field of view, at least some sensor elements of each of the first and second sets are sensitive to the infrared light and contribute to production of the image data.

9. An optical code reading device according to claim 8, wherein the color image sensor array includes a third set of sensor elements that are sensitive to a third visible wavelength band of light and to light within the infrared wavelength band.

10. An optical code reading device according to claim 9, wherein the first, second and third visible wavelength bands correspond to the colors red, green and blue.

11. An optical code reading device according to claim 8, wherein the infrared wavelength band includes 850 nm.

12. An optical code reading device according to claim 8, wherein upon illumination of the field of view, sensor elements of each of the first and second sets of sensor elements are sensitive to the infrared light to a sufficiently equal extent such that an average intensity value of light sensed by the first set of sensor elements is substantially equal to an average intensity value of light sensed by the second set of sensor elements.

13. An optical code reading device according to claim 8, wherein the color image sensor array is part of a rolling-reset CMOS imager.

14. An optical code reading device according to claim 8, further comprising:

a mechanical shutter positioned between the color image sensor array and the field of view.

15. An optical code reading device comprising:

a color image sensor array positioned to sense light reflected from an object in a field of view of the optical code reading device and to produce from the sensed reflected light image data representing an image of the object, the color image sensor array having a first set, a second set, and a third set of sensor elements, wherein;

the first set of sensor elements are characterized by a first spectral sensitivity that varies as a first function of wavelength, the first function having a local peak at a first peak sensitivity wavelength and also having a local peak near a first non-visible wavelength;

the second set of sensor elements are characterized by a second spectral sensitivity that varies as a second function of wavelength, the second function having a local peak at a second peak sensitivity wavelength and also having a local peak near the first non-visible wavelength;

the third set of sensor elements are characterized by a third spectral sensitivity that varies as a third function of wavelength, the third function having a local peak at a third peak sensitivity wavelength and also having a local peak near the first non-visible wavelength; and

the first, second and third peak sensitivity wavelengths being different wavelengths; and

an artificial illumination source positioned to illuminate the field of view of the optical code reading device with light that is incident upon and reflected from the object in the field of view toward the image sensor array, the illumination source being operable to produce radiation including light having the first non-visible wavelength.

16. An optical code reading device according to claim 15, wherein the first non-visible wavelength is an infrared wavelength.

17. A method of calibrating light emission of an optical code reading device, the optical code reading device including a color image sensor array and an artificial illumination source, the color image sensor array including a first set of sensor elements that are sensitive to a first visible wavelength band of light and a second set of sensor elements that are sensitive to a second visible wavelength band of light different than the first visible wavelength band of light, the artificial illumination source operable to emit visible light having a first light component corresponding to a wavelength in the first visible wavelength band of light and a second light component corresponding to a wavelength in the second visible wavelength band of light, comprising:

illuminating the color image sensor array with visible light having the first light component and the second light component;

sensing the first light component with the first set of sensor elements, the first set of sensor elements characterized by a first quantum efficiency;

sensing the second light component with the second set of sensor elements, the second set of sensor elements characterized by a second quantum efficiency that is less than the first quantum efficiency;

producing a first set of image data representing light intensities sensed by the first set of sensor elements and a second set of image data representing light intensities sensed by the second set of sensor elements;

determining a difference between the first and second quantum efficiencies by comparing the first and second sets of image data; and

selecting for the artificial illumination source a first light emission intensity level corresponding to the first light component and a second light emission intensity level corresponding to the second light component, the second light emission intensity level being different than the first light emission intensity level by an amount proportional to the difference between the first and second quantum efficiencies of the first and second sets of sensor elements.

18. The method of claim 17, further comprising selecting the first and second light emission intensity levels of the first and second light components so that, upon illumination, an average intensity of light sensed by the first set of sensor elements is substantially the same as an average intensity level of light sensed by the second set of sensor elements.

19. The method of claim 17, wherein the illuminating step further comprises illuminating with the artificial illumination source an object in a field of view of the optical code reading device, the visible light reflecting off the object toward the color image sensor array to thereby illuminate the color image sensor array.

20. An optical code reading device comprising:

a color image sensor array positioned to sense light reflected from an object in a field of view of the optical code reading device, the color image sensor array comprising;

a first set of sensor elements that are sensitive to a first visible wavelength band of light, the first set of sensor elements characterized by a first quantum efficiency; and

a second set of sensor elements that are sensitive to a second visible wavelength band of light, the second set of sensor elements characterized by a second quantum efficiency, the first and second quantum efficiencies having a difference therebetween in which the second quantum efficiency is less than the first quantum efficiency; and

an artificial illumination source positioned to illuminate the field of view of the optical code reading device with light that is incident on and reflected from the object in the field of view toward the color image sensor array, the artificial illumination source being operable to produce light including;

a first light component having a first light emission intensity level and a wavelength in the first visible wavelength band of light, and

a second light component having a second light emission intensity level and a wavelength in the second visible wavelength band of light, wherein the second light emission intensity level is different than the first light emission intensity level of the first light component by an amount that is proportional to the difference between the first and second quantum efficiencies.