Image-based code reader for acquisition of multiple views of an object and methods for employing same

• US 8,608,077 B2
• Filed: 11/30/2012
• Issued: 12/17/2013
• Est. Priority Date: 12/26/2008
• Status: Active Grant

• Current Assignee: Datalogic Adc, Inc. (Datalogic S.p.A.)
• Original Assignee: Datalogic Adc, Inc. (Datalogic S.p.A.)
• Inventors: Olmstead, Bryan L.
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): LY, TOAN C
• Application Number:
  US13/691,282
• Publication Number:
  US 20130098998A1
• Time in Patent Office: 382 Days
• Field of Search: 235/462.41
• US Class Current: 235/462.41
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/10801 Multidistance reading
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48

Abstract

Fold mirrors permit the imagers to be closer to each other and permit an optical code reader, such as a tunnel scanner, to confine them to a smaller housing volume or capacity. A plurality of sets of fold mirrors can also be employed to convey at least a portion of at least two different perspectives or two different depths of field of a composite view volume to different regions of an image field of a common imager. The sets of fold mirrors may also include split mirrors that have mirror components that reflect images from different view volumes to different imagers or different regions of an image field of a single imager.

Claims

1. A method for decoding first and second optical codes from respective first and second objects passing through a view volume, the method comprising:

capturing a first field of view of a view volume through a housing window onto a first region of an imager via a first set of a first number of first fold mirrors along a first image path, the first field of view having a first depth of field within the view volume;

capturing a second field of view of the view volume through the housing window onto a second region of the imager via a second set of a second number of second fold mirrors along a second image path, the second field of view having a second depth of field within the view volume, wherein the first number of first fold mirrors is greater than the second number of second fold mirrors, and wherein a first internal path length from the housing window to the imager along the first image path is longer than a second internal path length from the housing window to the imager along the second image path, thereby causing the second depth of field to extend more distally from the housing window into the view volume than the first depth of field extends from the housing window into the view volume;

forming a first image at the first region;

forming a second image at the second region; and

processing the first optical code based on at least the first image from the first field of view and processing the second optical code based on at least the second image from the second field of view, wherein the first and second optical codes are captured at different ones of arbitrary locations and angular orientations of a variety of possible locations and angular orientations of the first and second optical codes in the view volume.

2. The method of claim 1, wherein the first and second image paths propagate through a shared stationary lens to reach the first and second regions of the imager, wherein the first image path is divided into multiple first image path segments, the first image path segments determined by the first set of first fold mirrors, wherein the second image path is divided into multiple second image path segments, the second image path segments determined by the second set of second fold mirrors, and wherein at least one of the first image path segments or second image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager.

3. The method of claim 2, wherein the first image path includes a first internal path from the housing window to the imager along the first image path, wherein the first internal path includes at least one of the first image path segments including a first internal image path segment, wherein the second image path includes a second internal path from the housing window to the imager along the second image path, wherein the second internal path includes at least one of the second image path segments including a second internal image path segment, and wherein the first internal image path segment or the second internal image path segment traverses one of the first image path segments and one of the second image path segments.

4. The method of claim 1, wherein the first set of first fold mirrors includes at least a first set primary mirror and a first set secondary mirror such that an image propagates in a first path primary direction from the view volume along the first image path to the first set primary mirror and in a first path secondary direction from the first set primary mirror along the first image path to the first set secondary mirror, wherein the second set of second fold mirrors includes at least a second set primary mirror and a second set secondary mirror such that an image propagates in a second path primary direction from the view volume along the second image path to the second set primary mirror and in a second path secondary direction from the second set primary mirror along the second image path to the second set secondary mirror, and wherein the first path secondary direction and the second path secondary direction lead away from each other in substantially opposite directions.

5. The method of claim 4, wherein the first image path includes a first internal path from the housing window to the imager along the first image path, wherein the first internal path includes a first internal image path, wherein the second image path includes a second internal path from the housing window to the imager along the second image path, wherein the second internal path includes a second internal image path segment, wherein first internal image path segment correlates with the first path secondary direction, and wherein the second internal image path segment correlates with the second path secondary direction.

6. The method of claim 4, wherein the first set primary mirror and the second set primary mirror lie in different planes and form a split mirror.

7. The method of claim 1, wherein one of the first fold mirrors adjoins one of the second fold mirrors to form a split mirror and wherein the first and second adjoining fold mirrors lie in different planes.

8. A method for decoding first and second optical codes from respective first and second objects passing through a view volume, the method comprising:

capturing a first field of view of a view volume through a housing window onto a first region of an imager via a first set of a first number of first fold mirrors along a first image path, the first field of view having a first depth of field within the view volume;

capturing a second field of view of the view volume through the housing window onto a second region of the imager via a second set of a second number of second fold mirrors along a second image path, the second field of view having a second depth of field within the view volume, wherein the first number of first fold mirrors is greater than the second number of second fold mirrors, and wherein a first internal path length from the housing window to the imager along the first image path is longer than a second internal path length from the housing window to the imager along the second image path, thereby causing the second depth of field to extend more distally from the housing window into the view volume than the first depth of field extends from the housing window into the view volume;

forming a first image at the first region;

forming a second image at the second region; and

processing the first optical code based on at least the first image from the first field of view and processing the second optical code based on at least the second image from the second field of view, wherein the first and second image regions of the image field have unequal area.

9. An optical code reader for obtaining images from different

depth of fields associated with similar perspectives of a view volume, comprising:

a housing having a housing window;

an imager located within the housing;

a first set of first fold mirrors located within the housing to reflect, along a first image path, a first view associated with a first depth of field within the view volume onto a first region of the imager, wherein the optical code reader is operable to capture the first optical code at a first arbitrary location and angular orientation from a variety of locations and angular orientations of the first optical code in the view volume; and

a second set of second fold mirrors located within the housing to reflect, along a second image path, a second view associated with a second depth of field within the view volume onto a second region of the imager, wherein the optical code reader is operable to capture the second optical code at a second arbitrary location and angular orientation from the variety of locations and angular orientations of the second optical code in the view volume, wherein the first and second arbitrary locations and angular orientations are different, wherein the first and second sets of fold mirrors have a different number of fold mirrors, and wherein a first internal path length from the housing window to the imager along the first image path is longer than a second internal path length from the housing window to the imager along the second image path, thereby causing the second depth of field to extend more distally from the housing window into the view volume than the first depth of field extends from the housing window into the view volume.

10. An optical code reader operative for viewing sides of a six-sided box-shaped object being passed through a view volume, the six-sided box-shaped object having a first top side facing one or more upper apertures, a second bottom side facing the lower aperture, a third side facing a left vertical aperture, a fourth side facing a right vertical aperture such that the fourth side is opposite the third side, a fifth leading side, and a sixth trailing side, the optical code reader comprising:

a top imaging unit for capturing images of at least the first top side, the fifth leading side, and the sixth trailing side of the object;

a bottom imaging unit for capturing images of at least the second bottom side of the object; and

left and right imaging units, each for capturing images of at least the respective third and fourth sides of the object, each of the left and right imaging units further including;

a housing having a housing window;

an imager located within the housing;

a first set of first fold mirrors located within the housing to reflect, along a first image path, a first view associated with a first depth of field within the view volume onto a first region of the imager, a second set of second fold mirrors located within the housing to reflect, along a second image path, a second view associated with a second depth of field within the view volume onto a second region of the imager, wherein the second region of the imager is different from the first region of the imager such that the imager is operable to capture the first and second images simultaneously, wherein the first and second sets have a different number of fold mirrors, and wherein a first internal path length from the housing window to the imager along the first image path is longer than a second internal path length from the housing window to the imager along the second image path, thereby causing the second depth of field to extend more distally from the housing window into the view volume than the first depth of field extends from the housing window into the view volume.

11. The optical code reader of claim 10, wherein the first and second optical codes are captured at different ones of arbitrary locations and angular orientations from a variety of possible locations and angular orientations of the first and second optical codes in the view volume.

12. The optical code reader of claim 10, wherein the first and second image paths propagate through a shared stationary lens to reach the first and second regions of the imager, wherein the first image path is divided into multiple first image path segments, the first image path segments determined by the first set of first fold mirrors, wherein the second image path is divided into multiple second image path segments, the second image path segments determined by the second set of second fold mirrors, wherein one of the first image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager, and wherein one of the second image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager.

13. An optical code reader for obtaining images from different

depth of fields associated with similar perspectives of a view volume, comprising:

a housing;

an imager located within the housing;

a first set of first fold mirrors located within the housing to reflect, along a first image path, a first view associated with a first depth of field about a first focal plane within the view volume onto a first region of the imager, the first set of first fold mirrors including at least a first set primary mirror and a first set secondary mirror, the first image path having multiple first image path segments including at least a first primary image path segment and a first secondary image path segment, such that the first image path leads from the view volume in a first path primary direction along the first primary image path segment to the first set primary mirror and from the first set primary mirror in a first path secondary direction along the first secondary image path segment to the first set secondary mirror such that the first view having the first depth of field is directed in the first path primary direction along the first primary image path segment to the first set primary mirror and in the first path secondary direction along the first secondary image path segment to the first set secondary mirror; and

a second set of second fold mirrors located within the housing to reflect, along a second image path, a second view associated with a second depth of field about a second focal plane within the view volume onto a second region of the imager, the second focal plane being different from the first focal plane, the second set of fold mirrors including at least a second set primary mirror and a second set secondary mirror, the second image path having multiple second image path segments including at least a second primary image path segment and a second secondary image path segment, such that the second image path leads from the view volume in a second path primary direction along the second primary image path segment to the second set primary mirror and from the second set primary mirror in a second path secondary direction along the second secondary image path segment to the second set secondary mirror such that the second view having the second depth of field is directed in the second path primary direction along the second primary image path segment to the second set primary mirror and in the second path secondary direction along the second secondary image path segment to the second set secondary mirror, the first and second sets of mirrors having a different number of mirrors, and the first path secondary direction and the second path secondary direction leading away from each other in substantially opposite directions.

14. The optical code reader of claim 13, wherein the first and second fields of view into the view volume are from approximately the same perspective.

15. The optical code reader of claim 13, wherein the first field of view has a first bisecting plane and the second field of view has a second bisecting plane, wherein the first and second bisecting planes intersect each other at an angle of less than 5 degrees in the view volume.

16. The optical code reader of claim 13, wherein the magnitude of overlap of the first depth of field and the second depth of field is a minimum of 2% and a maximum of 50% of the sum of the magnitude of the first depth of field and the magnitude of the non-overlapping portion of the second depth of field.

17. The optical code reader of claim 13, wherein the first depth of field is defined by a first proximal range plane and a first distal range plane;

wherein the second depth of field is defined by a second proximal range plane and a second distal range plane;

wherein a total depth of field is defined by the first proximal range plane and the second distal range plane;

and wherein the first and second depths of field overlap by a minimum of 2% and a maximum of 35% of the total depth of field.

18. The optical code reader of claim 13, wherein one of the first fold mirrors is in close proximity to one of the second fold mirrors to form a split mirror.

19. The optical code reader of claim 13, wherein one of the first fold mirrors is connected to one of the second fold mirrors to form a split mirror.

20. The optical code reader of claim 13, wherein one of the first fold mirrors and one of the second fold mirrors form a monolithic mirror with a common plane.

21. The optical code reader of claim 13, wherein one of the first fold mirrors adjoins one of the second fold mirrors to form a split mirror and wherein the first and second adjoining fold mirrors lie in different planes.

22. The optical code reader of claim 13, wherein one of the first fold mirrors adjoins one of the second fold mirrors to form a split mirror and wherein the first and second adjoining fold mirrors lie in different planes.

23. The optical code reader of claim 13, wherein the first and second objects pass the housing window in a direction of travel;

wherein the first and second objects have window, leading, and trailing sides;

wherein the window side faces the housing window;

wherein the leading side passes the housing window in the direction of travel before the trailing side passes the housing window in the direction of travel; and

wherein at least one of the first or second fields of view is capable of receiving an image of the window side of the first or second objects in the view volume and is capable of receiving an image of at least a portion of a leading side or trailing side of the first or second objects in the view volume.

24. The optical code reader of claim 13, wherein the first and second fields of view are capable of receiving images from a top side of an object.

25. The optical code reader of claim 13, wherein a portion of the first optical code from the first image from the first field of view and a portion of the first optical code from a different image from the second field of view are stitched together to decode the first optical code.

26. The optical code reader of claim 13, wherein:

the first set of first fold mirrors includes at least a first set primary mirror and a first set secondary mirror;

the first image path has multiple first image path segments including at least a first primary image path segment and a first secondary image path segment, such that an image propagating along the first image path propagates from the view volume along the first primary image path segment to the first set primary mirror and from the first set primary mirror along the first secondary image path segment to the first set secondary mirror;

the second set of fold mirrors includes at least a second set primary mirror and a second set secondary mirror, such that an image propagating along the second image path propagates from the view volume along a second primary image path segment to the second set primary mirror and from the second set primary mirror along a second secondary image path segment to the second set secondary mirror;

the second image path has multiple second image path segments including at least a second primary image path segment and a second secondary image path segment, such that an image propagating along the second image path propagates from the view volume along the second primary image path segment to the second set primary mirror and from the second set primary mirror along the second secondary image path segment to the second set secondary mirror; and

one of the first fold mirrors is connected to a sequentially different one of the second fold mirrors to form a split mirror that is positioned along both the first and second image paths such that the split mirror is optically between noncorresponding pairs of first and second image path segments.

27. The optical code reader of claim 26, wherein:

the first set of fold mirrors includes at least a first set tertiary mirror;

the first image path includes a first tertiary image path segment and a first quaternary image path segment, such that the first set tertiary mirror is optically between the first tertiary image path segment and the first quaternary image path segment;

the second image path includes a second tertiary image path segment; and

the split mirror includes the first set tertiary mirror and the second set secondary mirror such that the split mirror is optically between the first tertiary image path segment and the first quaternary image path segment along the first image path and such that the split mirror is optically between the second secondary image path segment and the second tertiary image path segment.

28. The optical code reader of claim 26, wherein the split mirror has a first mirror region for reflecting images along the first image path, a second mirror region for reflecting images along the second image path, and a nonreflective region between the first and second mirror regions.

29. The optical code reader of claim 13, wherein the first and second image paths propagate through a shared stationary lens to reach the first and second regions of the imager, wherein the first image path is divided into multiple first image path segments, the first image path segments determined by the first set of first fold mirrors, wherein the second image path is divided into multiple second image path segments, the second image path segments determined by the second set of second fold mirrors, and wherein at least one of the first image path segments or second image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager.

30. The optical code reader of claim 13, wherein each of the first and second sets of fold mirrors includes at least one fold mirror having a trapezoidal shape.

31. The optical code reader of claim 13, wherein the first and second regions of the imager overlap.

32. The optical code reader of claim 13, wherein the first and second image regions of the imager are nonoverlapping.

33. The optical code reader of claim 13, wherein one or more additional sets of respective one or more additional fold mirrors are located within a housing to reflect, along additional image paths, respective additional views associated with additional depths of field about additional focal planes within the view volume onto additional regions of the imager, the additional focal planes being different from the first and second focal planes and being different from each other.

34. The optical code reader of claim 13, wherein the first and second objects pass through the view volume at different distances from the housing window.

35. The optical code reader of claim 13, further comprising a conveyor belt operable to move the first and second objects through the view volume, and wherein the imager and the fold mirrors are stationary.

36. The optical code reader of claim 13, wherein the first image path includes a first internal path from the housing window to the imager along the first image path, wherein the first internal path includes the first secondary image path segment, wherein the second image path includes a second internal path from the housing window to the imager along the second image path, and wherein the second internal path includes the second secondary image path segment.

37. The optical code reader of claim 13, wherein the magnitude of overlap of the first depth of field and the second depth of field is a minimum of 2% and a maximum of 50% of one half of the sum of the magnitude of the first depth of field and the magnitude of the second depth of field.

38. The optical code reader of claim 13, wherein the first and second optical codes are captured at different ones of arbitrary locations and angular orientations from a variety of possible locations and angular orientations of the first and second optical codes in the view volume.

39. The optical code reader of claim 13, wherein the first and second image paths propagate through a shared stationary lens to reach the first and second regions of the imager, wherein the first image path is divided into multiple first image path segments, the first image path segments determined by the first set of first fold mirrors, wherein the second image path is divided into multiple second image path segments, the second image path segments determined by the second set of second fold mirrors, wherein one of the first image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager, and wherein one of the second image path segments traverses one of the first image path segments and one of the second image path segments before the first and second image path segments enter the shared stationary lens in a travel direction along the first and second image paths from the view volume to the imager.

40. The optical code reader of claim 13, wherein the first set primary mirror and the second set primary mirror lie in different planes and form a split mirror.

41. A method for decoding first and second optical codes from respective leading and trailing sides of an object passing through a view volume, the method comprising:

capturing a leading field of view of a leading view volume through a housing window onto a first region of an imager via a first set of one or more first fold mirrors along a first image path;

capturing a trailing field of view of a trailing view volume onto a second region of the imager via a second set of one or more second fold mirrors along a second image path, wherein the second region of the imager is different from the first region of the imager, wherein the trailing field of view is different from the leading field of view, and wherein the trailing field of view crosses the leading field of view between the housing window and the leading view volume;

forming a first image of a leading side of an object at the first region;

forming a second image of a trailing side of the object at the second region; and

processing at least a first portion of the first optical code based on at least the first image from the first field of view and processing at least a second portion of the second optical code based on at least the second image from the second field of view, wherein the first and second optical codes are captured at different ones of arbitrary locations and angular orientations of a variety of possible locations and angular orientations of the first and second optical codes in the respective leading and trailing view volumes.