Diffuse bright field illumination system for a barcode reader

• US 8,857,720 B1
• Filed: 10/24/2013
• Issued: 10/14/2014
• Est. Priority Date: 10/24/2013
• Status: Active Grant

• Current Assignee: The Code Corporation (Brady Corporation)
• Original Assignee: The Code Corporation (Brady Corporation)
• Inventors: Lei, Ming, Powell, George
• Primary Examiner(s): LEE, SEUNG H
• Application Number:
  US14/062,743
• Time in Patent Office: 355 Days
• Field of Search: 235/439, 235/462.06, 235/462.42, 23547201-47203
• US Class Current: 235/462.42
• CPC Class Codes: G06K 19/06028 using bar codes
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10742 including a diffuser for diffusing the light from the light source to create substantially uniform illumination of the target record carrier
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• CPC Class Codes: G06K 7/1413 1D bar codes

Abstract

One aspect of the present disclosure is related to a barcode reader that includes a bright field illumination system, a dark field illumination system, and an additional illumination system that is better able to illuminate an area of the reader'"'"'s field of view between the far zone (where bright field illumination is optimal) and the close zone (where dark field illumination is optimal). In this “center zone,” the dark field illumination may not be bright enough and the bright field illumination may not be diffuse enough for reading a barcode.

Claims

1. A barcode reader, comprising:

a housing;

a camera located within the housing configured to capture an image of a barcode within a field of view of the camera, the field of view being directed along an optical axis; and

an illumination system configured to illuminate the barcode while the camera captures the image of the barcode, the illumination system comprising;

at least one light source; and

an optical substrate, not within the field of view of the camera, having front and back major surfaces arranged generally perpendicular to the optical axis, and between which light introduced from the at least one light source is transferred by total internal reflection primarily in a direction transverse to the optical axis,

wherein the optical substrate comprises one or more extraction features configured to extract light from the optical substrate and into the field of view.

2. The barcode reader of claim 1, wherein the at least one light source introduces light into an edge of the optical substrate between the front and back major surfaces.

3. The barcode reader of claim 1, wherein the at least one light source introduces light into the optical substrate through the back major surface.

4. The barcode reader of claim 1, wherein the optical substrate includes at least one aperture positioned around the field of view of the camera.

5. The barcode reader of claim 4, wherein the optical substrate comprises an outer edge and an inner edge and the at least one light source introduces light into the outer edge of the optical substrate and the inner edge defines the aperture.

6. The barcode reader of claim 5, wherein the optical substrate comprises an outer edge comprising a chamfered surface configured to reflect light onto a path relatively perpendicular to the optical axis.

7. The barcode reader of claim 4, wherein the at least one light source introduces light into an edge of the optical substrate between the front and back major surfaces.

8. The barcode reader of claim 4, wherein the at least one light source introduces light into the optical substrate through the back major surface.

9. The barcode reader of claim 4, wherein the optical substrate includes a reflective backing adjacent the back major surface.

10. The barcode reader of claim 9, wherein the reflective backing is attached to the back major surface.

11. The barcode reader of claim 4, wherein a shape of at least one of the front major surface and the back major surface is at least one of concave, convex, and parabolic.

12. The barcode reader of claim 11, wherein the shape of at least one of the front major surface and the back major surface is not symmetrical about a plane perpendicular to the optical axis.

13. The barcode reader of claim 4, wherein the one or more extraction features comprise variation of the surface topography of the back major surface.

14. The barcode reader of claim 13, wherein the variation of surface topography of the back major surface comprises convex and concave indentations and protrusions of the back major surface.

15. The barcode reader of claim 4, wherein the illumination system additionally comprises at least one secondary light source, wherein the light from the at least one secondary light source is emitted by the illumination system at an angle less than 45°

from a plane perpendicular to the optical axis.

16. The barcode reader of claim 1, wherein the optical substrate includes a reflective backing adjacent the back major surface.

17. The barcode reader of claim 16, wherein the reflective backing is attached to the back major surface.

18. The barcode reader of claim 1, wherein the illumination system additionally comprises at least one secondary light source, wherein the light from the at least one secondary light source is emitted by the illumination system at an angle less than 45°

from a plane perpendicular to the optical axis.

19. The barcode reader of claim 1, wherein a shape of at least one of the front major surface and the back major surface is at least one of concave, convex, and parabolic.

20. The barcode reader of claim 19, wherein the shape of at least one of the front major surface and the back major surface is not symmetrical about a plane perpendicular to the optical axis.

21. The barcode reader of claim 1, wherein the one or more extraction features are within the optical substrate.

22. The barcode reader of claim 21, wherein the one or more extraction features within the optical substrate is a variation in an index of refraction of the optical substrate.

23. The barcode reader of claim 22, wherein the variation in the index of refraction comprises at least one of one or more particles within the optical substrate, and a planar surface within the optical substrate.

24. The barcode reader of claim 22, wherein the one or more extraction features are distributed non-uniformly throughout the optical substrate.

25. The barcode reader of claim 24, wherein the one or more extraction features are distributed throughout the optical substrate such that light is uniformly emitted from the front major surface of the optical substrate.

26. The barcode reader of claim 24, wherein the one or more extraction features are distributed throughout the optical substrate such that light is non-uniformly emitted from the front major surface of the optical substrate in a desired intensity pattern.

27. The barcode reader of claim 21, wherein the at least one light source introduces light into an edge of the optical substrate between the front and back major surfaces.

28. The barcode reader of claim 21, wherein the at least one light source introduces light into the optical substrate through the back major surface.

29. The barcode reader of claim 21, wherein a shape of at least one of the front major surface and the back major surface is at least one of concave, convex, and parabolic.

30. The barcode reader of claim 29, wherein the shape of at least one of the front major surface and the back major surface is not symmetrical about a plane perpendicular to the optical axis.

31. The barcode reader of claim 1, wherein the one or more extraction features comprise variation of the surface topography of the back major surface.

32. The barcode reader of claim 31, wherein the variation of surface topography of the back major surface comprises convex and concave indentations and protrusions of the back major surface.