Illumination apparatus for optical readers

• US 5,623,137 A
• Filed: 03/30/1995
• Issued: 04/22/1997
• Est. Priority Date: 08/20/1993
• Status: Expired due to Fees

• Current Assignee: Welch Allyn Data Collection Inc (Welch Allyn Incorporated)
• Original Assignee: Welch Allyn Incorporated
• Inventors: Powers, Jeffrey B., Havens, William H., Karpen, Thomas W.
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): TREMBLAY, MARK STEPHEN
• Application Number:
  US08/413,609
• Time in Patent Office: 754 Days
• Field of Search: 235/462, 235/472, 235/455
• US Class Current: 235/462.23
• 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

An apparatus for illuminating an indicia in a sensing region of an object plane. A housing has a median longitudinal vertical plane and a horizontal scanning plane. A reflector for reflecting light directed thereagainst toward the sensing region has a first approximately curvilinear profile in a plane parallel to the scanning plane, and a second approximately curvilinear profile in a plane parallel to the median longitudinal plane. The central portion of the reflector defines an opening whereby light from the sensing may return in generally the same plane as light directed toward the sensing region.

Claims

1. An apparatus for illuminating a sensing region located in an object plane, comprising:

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

a reflector mounted within said housing for reflecting light directed thereagainst toward the sensing region, said reflector having a first curvilinear profile in a plane parallel to said scanning plane and a second curvilinear profile in a plane parallel to said median longitudinal plane, said reflector being elongated generally along said scanning axis and having a central portion, two end portions, and a focal line connecting a plurality of focal points, the central portion of said reflector defining an opening for the passage of light from said sensing region through said reflector; and

a plurality of sources of substantially Lambertian illumination disposed in said focal line for directing light against the reflector.

2. The apparatus of claim 1 further including a photodetector, and focusing means for focusing light from said sensing region onto said photodetector.

3. The apparatus of claim 2 in which said photodetector is offset to one side of said scanning plane, and in which the apparatus further includes a auxiliary reflector for reflecting light incident on the focusing means toward said photodetector.

4. The apparatus of claim 3 in which said photodetector is located between the focusing means and the sensing region, whereby the optical path between the sensing region and the photodetector is folded back on itself.

5. The apparatus of claim 2 in which light from said sensing region must pass through said opening before being focused onto said photodetector.

6. The apparatus of claim 1 in which said focusing means, said opening and said sensing region lie approximately in said scanning plane.

7. The apparatus of claim 1 in which said reflector has a single piece structure and in which said opening occupies only the central portion of said reflector.

8. The apparatus of claim 1 in which more sources of illumination are located adjacent to the end portions of said reflector than are located adjacent to the central portion of said reflector.

9. The apparatus of claim 8 in which said sources of illumination are located only adjacent to the end portions of said reflector.

10. The apparatus of claim 1 further including light diffusing means disposed in the optical path between said sources and the sensing region for substantially removing from light illuminating the sensing region image information depicting said sources.

11. The apparatus of claim 10 in which said diffusing means comprises a diffusing member positioned between the reflector and the sensing region.

12. The apparatus of claim 10 in which said diffusing means comprises a textured surface formed in said reflector.

13. An apparatus as set forth in claim 1 further including a circuit board within said housing for supporting said sources of illumination in said focal line.

14. An apparatus as set forth in claim 13 in which the illumination axes of said sources of illumination are aligned approximately perpendicular to the plane of said circuit board.

15. An apparatus as set forth in claim 13 in which at least one edge of said reflector is attached to said circuit board.

16. An apparatus as set forth in claim 14 in which at least one edge of said reflector is attached to said circuit board.

17. An apparatus for illuminating a sensing region located in an object plane, comprising:

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

a reflector mounted within said housing for reflecting light directed thereagainst toward the sensing region, said reflector having a first reflective surface made up of a plurality of first linear component reflective surfaces which together have a profile that approximates a first curvilinear profile in a plane parallel to said scanning plane and a second reflective surface made up of a plurality of second linear component reflective surfaces which together have a profile that approximates a second curvilinear profile in a plane parallel to said median longitudinal plane, said reflector being elongated generally along said scanning axis and having a central portion, two end portions, and a focal line connecting a plurality of focal points, the central portion of said reflector defining an opening for the passage of light from said sensing region through said reflector; and

a plurality of sources of substantially Lambertian illumination disposed in said focal line for directing light against the reflector.

18. An apparatus for illuminating a sensing region located in an object plane, comprising:

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

a plurality of discrete reflectors mounted within said housing for reflecting light directed thereagainst toward the sensing region, each of said reflectors having a first reflective surface made up of a plurality of first linear component reflective surfaces which together have a profile that approximates a first curvilinear profile in a plane parallel to said scanning plane and a second reflective surface made up of a plurality of second linear component reflective surfaces which together have a profile that approximates a second curvilinear profile in a plane parallel to said median longitudinal plane, said reflectors each having reflective surfaces which extend generally along said scanning axis and define respective focal lines connecting respective pluralities of focal points, said reflectors together defining a gap for the passage of light from said sensing region between said reflectors; and

a plurality of sources of substantially Lambertian illumination disposed in the focal lines of each of said reflectors for directing light against the respective reflectors.

19. The apparatus of claim 18 in which said first linear component reflective surfaces are disposed secantially with respect to respective portions of a curve lying in said scanning plane.

20. An apparatus for illuminating a sensing region located in an object plane, comprising:

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

a plurality of discrete reflectors mounted within said housing for reflecting light directed thereagainst toward the sensing region, each of said reflectors having a first curvilinear profile in a plane parallel to said scanning plane and a second curvilinear profile in a plane parallel to said median longitudinal plane, said reflectors each having reflective surfaces which extend generally along said scanning axis and define respective focal lines connecting respective pluralities of focal points, said reflectors together defining a gap for the passage of light from said sensing region between said reflectors;

a photodetector for receiving light from said sensing region, through said gap, and converting said light into an electrical signal; and

a plurality of sources of substantially Lambertian illumination disposed in the focal lines of each of said reflectors for directing light against the respective reflectors;

wherein the path along which light travels from said sensing region to said detector lies in approximately the same plane as the path along which light travels from said reflectors to said sensing region.

21. The apparatus of claim 20 in which said reflectors are disposed substantially symmetrically with respect to said median longitudinal plane.

22. The apparatus of claim 20 in which said gap extends generally along said scanning axis and includes no reflective surface.

23. The apparatus of claim 20 further including a photodetector, and focusing means for focusing light from said sensing region onto said photodetector.

24. The apparatus of claim 23 in which said photodetector is offset to one side of said scanning plane, and in which the apparatus further includes an auxiliary reflector for reflecting light incident on the focusing means toward said photodetector.

25. The apparatus of claim 24 in which said photodetector is located between the focusing means and the sensing region, whereby the optical path between the sensing region and the photodetector is folded back on itself.

26. The apparatus of claim 23 in which light from said sensing region must pass through said opening before being focused onto said photodetector.

27. The apparatus of claim 20 in which the first profiles of said reflectors define curves that lie along respective portions of a curve lying in said scanning plane.

28. The apparatus of claim 20 further including light diffusing means disposed in the optical path between said sources and the sensing region for substantially removing from light illuminating the sensing region image information depicting said sources.

29. The apparatus of claim 28 in which said diffusing means comprises a diffusing member positioned between the reflector and the sensing region.

30. An apparatus as set forth in claim 20 further including a circuit board within said housing for supporting said sources of illumination in said focal lines.

31. An apparatus as set forth in claim 30 in which the illumination axes of said sources of illumination are aligned approximately perpendicular to the plane of said circuit board.

32. An apparatus as set forth in claim 30 in at least one of the edges of said reflectors is attached to said circuit board.

33. An apparatus as set forth in claim 31 in at least one of the edges of said reflectors is attached to said circuit board.