Scanner with synchronously switched optics

• US 6,266,175 B1
• Filed: 04/27/1999
• Issued: 07/24/2001
• Est. Priority Date: 04/27/1999
• Status: Expired due to Term

• Current Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Original Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Inventors: McQueen, Alexander M.
• Primary Examiner(s): Phan, James
• Application Number:
  US09/300,629
• Time in Patent Office: 819 Days
• Field of Search: 359/209-211, 359/212, 359/216-219, 359/16-19, 359/15, 359/900, 235/467
• US Class Current: 359/216.1
• CPC Class Codes: G02B 26/123 Multibeam scanners, e.g. using multiple light sources or beam splitters
• CPC Class Codes: G06K 7/10623 Constructional details
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A method of and system a system for generating scan lines having different beam characteristics. In one embodiment, the beam is focused at different distances depending upon the scan line. A system may comprise a light source generating a reading beam, a suitable scanning mechanism such as a polygon mirror having a plurality of mirror facets, a beam correction plate in the beam path mounted to the facet wheel and rotating therewith. The reading beam passes through the correction plate and is then reflected off the mirror facet, the correction plate adjusting a beam characteristic, such as beam focus, scan angle, or beam power, for each mirror facet or portion of a mirror facet.

Claims

1. A scanning system comprising

a light source producing a light beam along a beam path;

a polygon mirror scanning mechanism disposed in the beam path for scanning the light beam;

an optical correction element mounted to rotate with the polygon mirror and positioned in the beam path between the scanning mechanism and the light source, the optical correction element having a plurality of zones of varying optical properties.

2. A scanning system according to claim 1 wherein the optical correction element comprises an optical plate, the zones comprising portions of the optical plate having different thickness.

3. A scanning system according to claim 1 further comprising a focusing lens proximate the light source for focusing the light beam, wherein the optical correction element is positioned between the light source and the focusing lens.

4. A scanning system according to claim 1 wherein the polygon mirror comprises a plurality of mirror facets rotating about a rotational axis, wherein the beam path of the light beam is parallel to the rotational axis, wherein a first mirror facet is constructed and arranged at an angle to the rotational axis such that the light beam parallel to the rotational axis is reflected and scanned by the first mirror facet, wherein a second mirror facet is constructed and arranged such that the light beam parallel to the rotational axis bypasses the second mirror facet and is re-routed onto the second mirror facet along a path generally perpendicular to the rotational axis whereby it is scanned by the second mirror facet.

5. A scanning system according to claim 4 further comprising first and second fold mirrors for routing the light beam onto the second mirror facet.

6. A scanning system according to claim 4 wherein the first mirror facet is arranged at an angle of about 45°

to the rotational axis and wherein the second mirror facet is arranged nearly parallel to the rotational axis.

7. A scanning system according to claim 4 further comprising a focusing lens, wherein the optical correction element is positioned between the light source and the focusing lens.

8. A scanning system according to claim 1 wherein the polygon mirror comprises first, second, third and fourth facets, the first and second facets being of like size and arranged at a first angle on opposite sides of the polygon, the third and fourth facets being of like size and arranged at a second angle on opposite sides of the polygon.

9. A scanning system according to claim 8

wherein the light beam is directed toward the polygon mirror along a parallel path to the rotational axis,

wherein the first and second mirror facets are disposed at the first angle to the rotational axis such that the first and second mirror facets are passed through the parallel path of the light beam as the polygon mirror is rotated,

wherein the third and fourth mirror facets are disposed at the second angle to the rotational axis such that the third and fourth mirror facets do not pass through the parallel path of the light beam as the polygon mirror is rotated whereby the light beam bypasses the third and fourth mirrors,

and wherein the scanning system further comprises routing mirrors for reflecting the light beam back toward the third and fourth mirror facets along a path generally perpendicular to the rotational axis whereby the light beam is scanned by the third and fourth mirror facets as the polygon mirror is rotated.

10. A scanning system according to claim 1 further comprising a stationary control module disposed in the beam path for selectively modifying waist location of the light beam.

11. A scanning system according to claim 1 wherein the optical correction element comprises a holographic disk.

12. A scanning system according to claim 1 wherein the light beam is focused to a waist at a first position when the light beam is passed through a first zone of the optical correction plate and the light beam is focused to a waist at a second position nearer to the scanning system when the light beam is passed through a second zone of the optical correction plate.

13. A scanning system according to claim 1 wherein the optical property varied by the zones of the optical correction element is selected from the group consisting of:

focal distance, scan angle, beam power, beam polarization, wavelength, transmissiveness.

14. A scanning system according to claim 1 wherein the optical correction plate and the facet wheel are co-molded plastic forming a single integrally formed structure.

15. A scanning system according to claim 1 wherein one or more of the zones comprises a void.

16. A scanning system according to claim 1 wherein the optical correction plate further comprises windage elements.

17. A scanning system according to claim 1 wherein the optical correction plate further comprises assembly elements for assisting in attachment of elements of the polygon mirror.

18. A method of scanning an item in a scan volume, comprising the steps of

generating a light beam from a light source along a beam path;

locating a scanning mechanism comprising a rotating facet wheel in the beam path, the facet wheel having a plurality of mirror facets;

mounting an optical plate in the beam path between the light source and the facet wheel;

rotating the optical plate and the facet wheel together, the optical plate having a plurality of sectors of different optical properties wherein each mirror facet has a corresponding sector of the optical plate; and

for each mirror facet, (1) adjusting an optical characteristic of the-light beam by passing the light beam through a corresponding sector of the optical plate and (2) scanning the light beam over a given scan angle to generate a given scan beam having the adjusted optical characteristic.

19. A method according to claim 18 further comprising mounting the optical plate to the facet wheel.

20. A method according to claim 19 further comprising integrally forming the mirror facets and the optical plate in a single molding operation.

21. A method according to claim 18 further comprising

focusing the light beam to a given waist location by positioning a focusing lens in the beam path;

positioning the optical plate between the light source and the focusing lens.

22. A method according to claim 18 wherein the light source comprises a laser diode.

23. A method according to claim 18 wherein the step of adjusting an optical characteristic comprises

focusing the light beam to a waist at a first position when the light beam is passed through a first sector of the optical plate and focusing the light beam to a waist at a second position nearer to the light source when the light beam is passed through a second sector of the optical plate.

24. A method according to claim 18 wherein the step of adjusting an optical characteristic comprises adjusting beam power.

25. A method according to claim 18 wherein the step of adjusting an optical characteristic comprises adjusting scan angle.

26. A method according to claim 18 wherein the step of adjusting an optical characteristic comprises adjusting beam polarization.

27. A method according to claim 18 wherein the step of adjusting an optical characteristic comprises adjusting beam wavelength.

28. A method according to claim 18 wherein one or more of the sectors comprises a void.

29. A method of scanning an item in a scan volume, comprising the steps of

generating a light beam from a light source;

providing a rotating facet wheel for scanning the light beam, the facet wheel having at least a first mirror facet and a second mirror facet;

rotating the facet wheel about a rotating axis;

directing the light beam along a first beam path parallel to the rotational axis;

rotating the facet wheel to place the first mirror facet proximate the first beam path;

arranging the first mirror facet in the first beam path and at an angle to the rotational axis such that the light beam parallel to the rotational axis is reflected and scanned by the first mirror facet;

rotating the facet wheel to place the second mirror facet proximate the first beam path;

arranging the second mirror facet at an angle to the rotational axis such that the light beam parallel to the rotational axis bypasses the second mirror facet and re-routing the light beam onto the second mirror along a path generally perpendicular to the rotational axis whereby it is scanned by the second mirror facet.

30. A method according to claim 29 further comprising

positioning an optical plate between the light source and the facet wheel, the optical plate having a plurality of sectors;

rotating the optical plate along with the facet wheel;

for each mirror facet, (1) adjusting an optical characteristic of the light beam by passing the light beam through a corresponding sector of the optical plate and (2) scanning the light beam over a given scan angle to generate a given scan beam having the adjusted optical characteristic.

31. A method according to claim 29 further comprising

focusing the light beam to a given waist location by positioning a focusing lens in the beam path;

positioning an optical plate between the light source and the focusing lens.

32. A method according to claim 31 further comprising

mounting the optical plate onto the facet wheel, the optical plate having a plurality of sectors of different thickness;

focusing the light beam to a near focal distance by passing the light beam through a thin sector;

focusing the light beam to a far focal plane by passing the light beam through a thick sector.

33. A method according to claim 29 wherein the optical plate comprises a holographic disk.

34. A method according to claim 29 further comprising

controlling focus of the light beam depending upon which mirror facet is scanning.

35. A method according to claim 29 further comprising

controlling beam power of the light beam depending upon which mirror facet is scanning the light beam.

36. A method according to claim 29 further comprising

switching between (a) scanning over a narrow angle focused at a far plane and (b) scanning over a wide angle focused at a near plane.

37. A method according to claim 36 further comprising

providing a manually-actuated switch for switching between (a) scanning over a narrow angle focused at a far plane and (b) scanning over a wide angle focused at a near plane.

38. A method of scanning an item in a scan volume, comprising the steps of

generating a light beam from a light source;

providing a facet wheel for scanning the light beam, the facet wheel having at least a first mirror facet and a second mirror facet;

directing the light beam along a first beam path toward the facet wheel;

scanning with the first mirror facet by arranging the first mirror facet such that as the facet wheel is rotated, the first mirror facet is moved to pass through the first beam path for scanning the light beam;

scanning with the second mirror facet by

arranging the second mirror facet such that as the facet wheel is rotated, the second mirror facet is moved without passing through the first beam path, the light beam bypassing the second mirror facet, and

redirecting the light beam that has bypassed the second mirror facet along a second beam path and onto the second mirror facet for scanning the light beam.

39. A method according to claim 38 further comprising

controlling focus of the light beam depending upon which mirror facet is scanning.

40. A method according to claim 38 further comprising

switching between (a) scanning over a narrow angle focused at a far plane and (b) scanning over a wide angle focused at a near plane.