Miniature laser diode focusing module using micro-optics

• US 6,092,728 A
• Filed: 07/12/1999
• Issued: 07/25/2000
• Est. Priority Date: 03/30/1992
• Status: Expired due to Fees

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Katz, Joseph, Krichever, Mark, Tan, Chin, Li, Yajun, Bard, Simon
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US09/352,542
• Time in Patent Office: 379 Days
• Field of Search: 235/462.32, 235/462.36, 235/462.35, 235/462.27, 235/462.38, 235/462.39, 235/462.4, 235/462.41, 235/462.42, 235/454, 359/986, 359/387
• US Class Current: 235/454
• CPC Class Codes: G06K 7/10811 Focalisation

Abstract

A miniature module emits and focuses a divergent light beam. The focusing module consists of a small-sized light emitter, such as a laser diode, and a micro-optical element seated in a lens holder. The outside diameter of the micro-optical element is 4 mm or less and preferably less than or equal to 2.5 mm. The micro-optical element may be a small conventional lens, a gradient index lens, or one of several types of diffractive optical element. The focal length of the module relative to the light from the emitter is set by sliding the lens holder along its central axis and permanently adhering it in place with respect to the emitter after focusing. During focal adjustment, axial rotation between the lens holder and between the base of the emitter is prevented by a series of notches. The miniature focusing module is smaller, lighter, costs less and may provide a larger relative aperture than the conventional structures currently used for example in solid state laser scanners.

Claims

1. Light emitting and focusing elements for an optical scanner of the type used for scanning optical indicia such as bar codes, the light emitting and shaping elements comprising:

a light emitting element;

one or more light focusing elements for focusing light emitted from the light emitting element, the focusing elements comprising a phase contrast plate positioned generally perpendicularly to the path of light emitted from the light emitting element,

wherein the phase contrast plate has at least a first region and a second region, and

wherein the phase delay of light passing through the first region differs from the phase delay of light passing through the second region.

2. The light emitting and focusing elements of claim 1 incorporated in an optical scanner of the type used for scanning optical indicia such as bar codes.

3. The light emitting and focusing elements of claim 1 wherein the light emitting and one or more light focusing elements are mounted in a module.

4. The light emitting and focusing elements of claim 1 further comprising a lens collimator.

5. The optical scanner of claim 4 wherein the phase contrast plate is placed in front of the lens collimator.

6. The light emitting and focusing elements of claim 1 wherein the light emitted from the light emitting element generally follows a longitudinal axis, and wherein the first region of the phase contrast plate is closer to the longitudinal axis than the second region, and the second region surrounds the first region.

7. The light emitting and focusing elements of claim 6 wherein the phase delay of light passing through the first and second regions differ by π

.

8. The light emitting and focusing elements of claim 6 wherein the phase delay of the first and second region are matched.

9. The light emitting and focusing elements of claim 7 wherein the elements are configured to generate truncated J₀ Bessel beams for scanning distant optical indicia.

10. The light emitting and focusing elements of claim 6 wherein the phase delay of light passing through the first and second regions differ such that α

_Z -α

_O =-π

, where α

_Z is the phase delay of light passing through the first region and α

_O is the phase delay of light passing through the second region.

11. The light emitting and focusing elements of claim 10 wherein the light emitted from the light emitting element generally follows a longitudinal axis, and wherein the first region of the phase contrast plate is closer to the longitudinal axis than the second region, and the second region surrounds the first region.

12. The light emitting and focusing elements of claim 6 Wherein the phase contrast plate is an optically flat plate with one or more optical coating that provides the different phase delays in the first and second regions.

13. The light emitting and focusing elements of claim 12 wherein the optical coating of the second region has a transmittance of absolute value less than one.

14. The light emitting and focusing elements of claim 1 wherein the phase contrast plate is configured to provide an increased working range for the optical scanner.

15. The light emitting and focusing elements of claim 14 wherein the light emitting element generates a laser beam.

16. The light emitting and focusing elements of claim 15 wherein the light emitting element comprises a laser diode.

21. The optical scanner of claim 4 wherein the phase contrast plate is placed in front of the lens collimator.

17. An optical scanner of the type used for scanning optical indicia such as bar codes, the optical scanner comprising:

a light emitting element;

one or more light focusing elements for focusing light emitted from the light emitting element, the focusing elements comprising a phase contrast plate positioned generally perpendicularly to the path of light emitted from the light emitting element,

wherein the phase contrast plate has at least a first region and a second region, and

wherein the phase delay of light passing through the first region differs from the phase delay of light passing through the second region.

18. The optical scanner of claim 17 wherein the phase contrast plate is configured to provide an increased working range for the optical scanner.

19. The optical scanner of claim 17 wherein the light emitting element generates a laser beam.

20. The optical scanner of claim 17 wherein the light emitting and focusing elements are configured to generate truncated J₀ Bessel beams for scanning distant optical indicia.