Light collection systems in electro-optical readers

• US 5,923,021 A
• Filed: 08/10/1998
• Issued: 07/13/1999
• Est. Priority Date: 06/19/1995
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Dvorkis, Paul, McGlynn, Daniel R., Barkan, Edward, Snyder, William, Goren, David, Marwin, Gregg
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): TREMBLAY, MARK STEPHEN
• Application Number:
  US09/131,303
• Time in Patent Office: 337 Days
• Field of Search: 235/455, 235/462.06, 235/462.01, 250/208.6
• US Class Current: 235/455
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• 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

Abstract

An optical scanner for reading indicia of variable light reflectivity, such as bar code symbols, having a light source for producing a light beam for scanning a target; a sensor for collecting the reflected light from the target; and various light collection systems, including a louver formed from an array of thin slats positioned adjacent to the sensor so that light directed along substantially only one angle reaches the sensor, as well as imaging/diffusing optical systems.

Claims

1. An optical scanner, comprising:

a light source for directing a light beam to a target having an indicium to be read;

a sensor having a relatively small sensor area and a relatively large field of view, and operative for collecting reflected light from the indicium; and

a light collection system including an optical diffuser positioned adjacent to the sensor so that reflected light from the relatively large field of view is collected and focused onto the relatively small sensor area.

4. The arrangement as defined in claim 1;

and further comprising an anti-reflective coating on the front surface of the diffuser.

2. In an electro-optical scanner for reading indicia, a light collection arrangement for collecting light reflected off the indicia en route to a photodetector, said arrangement comprising:

a concave collecting reflector for focusing the reflected light along a first optical path at a focal point; and

a light diffuser at the focal point for redirecting the reflected light along a second optical path toward and past the reflector to the photodetector.

3. The arrangement as defined in claim 2, wherein the diffuser has a front surface facing toward the reflector, and a corrugated, rear reflecting surface facing away from the reflector.

5. The arrangement as defined in claim 2;

and further comprising an optical filter and a convex lens in the second optical path.

6. The arrangement as defined in claim 3, wherein the filter is mounted on the reflector.

7. A light collection arrangement for collecting light reflected off indicia to be read by an electro-optical scanner, said arrangement comprising:

a light reflector for receiving the light reflected off the indicia, and for directing the reflected light away from the reflector;

a light diffuser for receiving the reflected light directed away from the reflector, and for redirecting the directed light back toward the reflector; and

a light sensor for receiving the redirected light from the diffuser, and for generating an electrical signal indicative of the indicia.

8. The arrangement as defined in claim 7, wherein the reflector is a generally concave collecting mirror for focusing the light reflected off the indicia to a focal zone;

and wherein the diffuser is located at the focal zone.

9. The arrangement as defined in claim 8, wherein the collecting mirror has an opening through which the redirected light passes.

10. The arrangement as defined in claim 9, wherein the collecting mirror has opposite sides, and wherein the diffuser and the sensor are located at the opposite sides of the collecting mirror.

11. The arrangement as defined in claim 9;

and further comprising a focusing lens for focusing the redirected light onto the sensor.

12. The arrangement as defined in claim 11, wherein the lens is located at the opening of the collecting mirror.

13. The arrangement as defined in claim 11;

and further comprising a light filter for filtering the redirected light prior to being received at the sensor.

14. The arrangement as defined in claim 13, wherein the filter is located adjacent the lens.

15. The arrangement as defined in claim 14, wherein the collecting mirror has a mount adjacent the opening, for holding the filter.

16. The arrangement as defined in claim 13, wherein the opening is centrally located on the collecting mirror, and wherein the lens is fixedly mounted in the opening, and wherein the filter is fixedly mounted in the mount adjacent the lens.

17. The arrangement as defined in claim 7, wherein the diffuser has a light-transmissive body having front and rear surfaces closer and farther, respectively, relative to the reflector.

18. The arrangement as defined in claim 17, wherein the closer front surface has an anti-reflective coating.

19. The arrangement as defined in claim 17, wherein the farther rear surface has a reflective coating.

20. The arrangement as defined in claim 17, wherein the farther rear surface is corrugated.