Illumination system for optical reader

• US 5,430,285 A
• Filed: 08/20/1993
• Issued: 07/04/1995
• Est. Priority Date: 08/20/1993
• Status: Expired due to Term

• Current Assignee: Welch Allyn Incorporated
• Original Assignee: Welch Allyn Incorporated
• Inventors: McClaude, Mark A., Powers, Jeffrey B., West, Theresa M., Karpen, Thomas W., Lagerway, William H., Beckhusen, Gerard F., Wright, Kenneth A.
• Primary Examiner(s): Willis, Davis L.
• Assistant Examiner(s): RASHID, PETER
• Application Number:
  US08/109,735
• Time in Patent Office: 683 Days
• Field of Search: 235/462, 235/472
• US Class Current: 235/462.42
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners

Abstract

There is disclosed an apparatus for illuminating a sensing region having an object therein, comprising a reflector that is elongated in a first plane, the reflector having a width dimension that is less than a width dimension of a sensing region to be illuminated, and further having a first curved profile in the first plane about a center of curvature. In a preferred embodiment the reflector is disposed between the center of curvature and the sensing region. In a second plane which is orthogonal to the first plane and includes the center of curvature, a reflecting surface of the reflector has a second curved profile. A plurality of substantially Lambertian light sources each face the reflector for directing light thereto generally in a direction of the center of curvature for reflection toward the sensing region. The second profile preferably comprises a portion of an ellipse and a light source is disposed substantially at a primary focus thereof. The second profile preferably has a gap for transmitting retroreflected light generated within the sensing region therethrough. An upper portion of the second profile comprises a portion of a first surface of revolution selected from the group of ellipse and parabola, and the lower portion of the second profile can comprise a portion of a second surface of revolution selected from the group of ellipse and parabola, a light source being disposed at a focus of each of the first surface of revolution and the second surface of revolution. The assembly is combined in a scanner for reading optical patterns.

Claims

1. An apparatus for illuminating a sensing region having an object therein, comprising:

a reflector that is elongated in a first plane, said reflector having a width dimension that is less than a width dimension of a sensing region to be illuminated, and further having a first curved profile in said first plane about a center of curvature, said reflector being disposed between said center of curvature and the sensing region, a reflecting surface of said reflector further comprising a second curved profile in a second plane that is orthogonal to said first plane and includes said center of curvature;

a plurality of substantially Lambertian light sources, each facing said reflector for directing light thereto for reflection toward the sensing region.

2. The apparatus in accordance with claim 1, wherein said second profile comprises a portion of an ellipse and a said light source is disposed substantially at a primary focus thereof.

3. The apparatus in accordance with claim 1, wherein said second profile comprises a portion of an parabola and a said light source is disposed substantially at a focus thereof.

4. The apparatus in accordance with claim 1, wherein said second profile has a gap for transmitting retroreflected light from the sensing region therethrough, said gap defining an upper and a lower portion of said second profile.

5. The apparatus in accordance with claim 4, wherein said upper portion of said second profile comprises a portion of a first surface of revolution selected from the group of ellipse and parabola, and said lower portion of said second profile comprises a portion of a second surface of revolution selected from the group of ellipse and parabola, a said light source being disposed at a focus of each of said first surface of revolution and said second surface of revolution.

6. The apparatus in accordance with claim 4, wherein said upper portion of said second profile comprises a planar surface, and said lower portion of said second profile comprises a portion of a second surface of revolution selected from the group of ellipse and parabola, a said light source being disposed at a focus of said second surface of revolution.

7. An optical scanner for reading externally located indicia that are disposed in a sensing region comprising:

a housing having a median longitudinal plane and a scanning axis disposed in a cross-longitudinal plane;

a source of substantially Lambertian illumination;

an elongated reflector aligned generally in said scanning axis for reflecting light incident thereon, said reflector having a width dimension that is less than a width dimension of a sensing region to be illuminated, said light travelling along a path extending to said reflector from said source of illumination, and being reflected generally toward the sensing region, said reflector being elongated generally along said scanning axis, and having a central portion, two end portions, a focal line connecting a plurality of primary focal points, a reflecting profile in a plane orthogonal to said focal line, said source of illumination being disposed in said focal line;

window means in said housing for transmitting said reflected light to illuminate the sensing region and for admitting light from said sensing region therethrough, a frontal plane orthogonal with said median longitudinal plane being defined at an intersection of said median longitudinal plane with said window means, a displacement of each said end portion from said frontal plane differing from a displacement of said central portion therefrom;

a photodetector disposed in said housing in a path of said admitted light and producing an output responsive thereto; and

optical means disposed in a path of said admitted light for projecting an image of the indicia onto said photodetector.

8. The scanner in accordance with claim 7, wherein said reflecting profile is nonlinear.

9. The scanner in accordance with claim 8, wherein said source of illumination comprises a plurality of light emitting diodes.

10. The scanner in accordance with claim 9, wherein said reflecting profile comprises a first reflecting profile in a first plane including a first light emitting diode and a second reflecting profile in a second plane including a second light emitting diode, said first reflecting profile and said second reflecting profile having non-identical configurations in said first and second planes.

11. The scanner in accordance with claim 7, wherein said reflecting profile has a gap disposed in said path of admitted light for transmission of said admitted light therethrough, said gap defining an upper and a lower portion of said reflecting profile.

12. The scanner in accordance with claim 11, wherein said upper portion of said reflecting profile is parabolic, and said lower portion of said reflecting profile is elliptical.

13. The scanner in accordance with claim 11, wherein said upper portion of said reflecting profile is linear, and said lower portion of said reflecting profile is elliptical.

14. The scanner in accordance with claim 11, wherein said upper portion of said reflecting profile is linear, and said lower portion of said reflecting profile is parabolic.

15. The scanner in accordance with claim 7, wherein said reflector has a curvature in said cross-longitudinal plane.

16. The scanner in accordance with claim 15, wherein said curvature comprises an arc of a circle.

17. The scanner in accordance with claim 7, wherein said reflector has a central portion and two angulated end portions, said central portion and said end portions being linear in said cross-longitudinal plane.

18. The scanner in accordance with claim 7, wherein said displacement of each said end portion from said frontal plane exceeds said displacement of said central portion therefrom.

19. The scanner in accordance with claim 7, wherein said displacement of each said end portion from said frontal plane is less than said displacement of said central portion therefrom.

20. An optical scanner for reading externally located indicia that are disposed in a sensing region comprising:

a housing having a median longitudinal plane and a scanning axis in a cross-longitudinal plane;

a source of substantially Lambertian illumination comprising a plurality of quasi-monochromatic light emitting diodes;

an elongated reflector aligned generally in said scanning axis for reflecting light incident thereon, said reflector having a width dimension that is less than a width dimension of a sensing region to be illuminated, said light travelling along a path extending to said reflector from said source of illumination, and being reflected generally toward the sensing region, said reflector being elongated generally along said scanning axis, and having a central portion, two end portions, a focal line connecting a plurality of primary focal points, and a nonlinear reflecting profile in a plane orthogonal to said focal line, said light emitting diodes being disposed in said focal line;

window means in said housing for transmitting said reflected light to illuminate the sensing region and for admitting light from without the scanner therethrough, a frontal plane orthogonal with said median longitudinal plane being defined at an intersection of said median longitudinal plane with said window means, said reflecting profile having a gap disposed in said path of admitted light for transmission of said admitted light therethrough, said gap defining an upper and a lower portion of said reflecting profile;

a photodetector disposed in said housing in a path of said admitted light and producing an output responsive thereto; and

optical means disposed in a path of said admitted light for projecting an image of the indicia onto said photodetector;

said reflector having a curvature in said cross-longitudinal plane, and a displacement of each said end portion from said frontal plane exceeding a displacement of said central portion therefrom.

21. The scanner in accordance with claim 20, wherein said upper portion of said reflecting profile is parabolic, and said lower portion of said reflecting profile is elliptical.

22. The scanner in accordance with claim 20, wherein said upper portion of said reflecting profile is elliptical and said lower portion of said reflecting profile is parabolic.

23. The scanner in accordance with claim 20 wherein said upper portion of said reflecting profile is linear, and said lower portion of said reflecting profile is elliptical.