Miniature optical scanner for a two axis scanning system

• US 5,557,444 A
• Filed: 10/26/1994
• Issued: 09/17/1996
• Est. Priority Date: 10/26/1994
• Status: Expired due to Term

• Current Assignee: University of Washington, Washington University In St Louis
• Original Assignee: University of Washington
• Inventors: Kollin, Joel S., Johnston, Richard S., Melville, Charles D.
• Primary Examiner(s): Phan, James
• Application Number:
  US08/329,508
• Time in Patent Office: 692 Days
• Field of Search: 359/198, 359/199, 359/112-114, 359/223, 359/224, 310/36, 310/208
• US Class Current: 359/199.1
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 7/1821 for rotating or oscillating mirrors

Abstract

A miniature optical scanner includes an electromagnetic drive having stationary magnets and stationary drive coils to minimize the rotational inertia of the scanner and increase the scanner'"'"'s resonant frequency. The scanner is such that the resonant frequency is manually tunable as well as automatically adjustable to compensate for variables causing frequency drift. The optical scan angle is increased by employing a multiplying mirror with the optical scanner. For a two axis scanning system, the multiplying mirror may be formed of a second optical scanner to increase the optical scan angle relative to both of the axes.

Claims

1. A miniature optical scanner comprising:

a ferromagnetic base with a first stator and a second stator formed thereon, said first and second stators being generally parallel to each other,

a first electrical coil wound about said first stator in a first direction;

a second electrical coil wound about said second stator in a second direction opposite said first direction;

first and second magnets disposed on said base on opposite sides of said first and second stators and equidistant to said first and second stators;

a spring plate having first and second support portions mounted respectively on said first and second magnets and having a centrally located mirror mounting portion disposed above said starors with an axis of rotation equidistant to said stators; and

a mirror mounted on said mirror mounting portion of said spring plate, said mirror being oscillated about said axis of rotation when an alternating drive signal is coupled to said first and second electrical coils.

2. A miniature optical scanner as recited in claim 1 wherein said mirror is a reflective surface coated on said mirror mounting portion of said spring plate.

3. A miniature optical scanner as recited in claim 1 wherein said mirror and spring plate are integrally formed.

4. A miniature optical scanner as recited in claim 1 wherein said mirror mounting portion of said spring plate forms an armature having one end generally above said first stator and an opposite end generally above said second stator such that when said one end is attracted to said first stator the opposite end of said mirror mounting portion is repulsed by said second stator.

5. A miniature optical scanner as recited in claim 1 wherein said mirror mounting portion of said spring plate has a resonant frequency of oscillation and further including means coupled to said spring plate for adjusting said resonant frequency of oscillation.

6. A miniature optical scanner as recited in claim 5 further including means responsive to variations in temperature for applied various amounts of tension in said spring plate to maintain said resonant frequency constant over a given range of temperatures.

7. A miniature optical scanner as recited in claim 1 including a tension adjuster for adjusting the tension in said spring plate.

8. A miniature optical scanner as recited in claim 7 wherein said tension adjuster allows manual adjustments of said tension.

9. A miniature optical scanner as recited in claim 7 wherein said tension adjuster is responsive to variations in temperature to vary the tension in said spring plate.

10. A miniature optical scanner as recited in claim 1 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said housing forming a vacuum chamber for said scanner.

11. A miniature optical scanner as recited in claim 1 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said window is disposed at an angle with respect to said base to minimize the effect of reflections from said window.

12. A miniature optical scanner as recited in claim 11 wherein said angle is greater than the maximum optical scan angle of said mirror.

13. A miniature optical scanner comprising:

a ferromagnetic base with a first stator and a second stator formed thereon, said first and second stators being generally parallel to each other and centrally disposed on said base;

a first electrical coil wound about said first stator;

a second electrical coil wound about said second stator;

first and second magnets disposed on said base on opposite sides of said first and second stators and equidistant to said first and second stators;

a spring plate having first and second support portions mounted respectively on said first and second magnets and having a centrally located mirror mounting portion disposed above said stators with an axis of rotation equidistant to said stators;

a mirror mounted on said mirror mounting portion of said spring plate; and

means for driving said coils to generating alternating magnetic fields of opposite polarity in said first and second stators to oscillate said mirror about said axis of rotation.

14. A miniature optical scanner as recited in claim 13 wherein said mirror is a reflective surface coated on said mirror mounting portion of said spring plate.

15. A miniature optical scanner as recited in claim 13 wherein said mirror and spring plate are integrally formed.

16. A miniature optical scanner as recited in claim 13 wherein said mirror mounting portion of said spring plate forms an armature having one end generally above said first stator and an opposite end generally above said second stator such that when said one end is attracted to said first stator the opposite end of said mirror mounting portion is repulsed by said second stator.

17. A miniature optical scanner as recited in claim 13 wherein said mirror mounting portion of said spring plate has a resonant frequency of oscillation and further including means coupled to said spring plate for adjusting said resonant frequency of oscillation.

18. A miniature optical scanner as recited in claim 17 further including means responsive to variations in temperature for applied various amounts of tension in said spring plate to maintain said resonant frequency constant over a given range of temperatures.

19. A miniature optical scanner as recited in claim 13 including a tension adjuster for adjusting the tension in said spring plate.

20. A miniature optical scanner as recited in claim 19 wherein said tension adjuster allows manual adjustments of said tension.

21. A miniature optical scanner as recited in claim 19 wherein said tension adjuster is responsive to variations in temperature to vary the tension in said spring plate.

22. A miniature optical scanner as recited in claim 13 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said housing forming a vacuum chamber for said scanner.

23. A miniature optical scanner as recited in claim 13 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said window is disposed at an angle with respect to said base to minimize reflections from said window.

24. A miniature optical scanner as recited in claim 23 wherein said angle is greater than the maximum optical scan angle of said mirror.

25. A miniature optical scanner comprising:

a ferromagnetic base with a first stator and a second stator formed thereon, said first and second stators being generally parallel to each other and each including a respective stator electrical coil wound thereon to produce magnetic fields in said first and second starors of opposite polarity in response to a drive signal applied to each coil;

first and second magnets disposed on said base on opposite sides of said first and second stators and equidistant to said first and second stators;

a spring plate having first and second support portions mounted respectively on said first and second magnets and having a centrally located mirror mounting portion disposed above said stators with an axis of rotation equidistant to said stators;

a mirror mounted on said mirror mounting portion of said spring plate, said mirror being oscillated about said axis of rotation when an alternating drive signal is coupled to said first and second electrical coils; and

clamping means for attaching said spring plate and said first and second magnets to said base.

26. A miniature optical scanner as recited in claim 25 wherein said clamping means includes a first cap mounted over said first support portion of said spring plate and said first magnet, a second cap mounted over said second support portion of said spring plate and said second magnet.

27. A miniature optical scanner as recited in claim 26 including a spring plate tension adjustor with at least one elongated member extending between said first and second caps to vary the distance between said caps to increase or decrease the tension in said spring plate.

28. A miniature optical scanner as recited in claim 27 wherein said tension adjuster includes a screw extending through one of said caps into said elongated member to allow said tension to be manually adjusted by tightening or loosening said screw.

29. A miniature optical scanner as recited in claim 27 wherein said elongated member is responsive to variations in temperature to vary its length so as to automatically vary the tension in said spring plate in response to variations in temperature.

30. A miniature optical scanner as recited in claim 27 wherein said elongated member includes means responsive to an electrical control signal to vary its size to cause the distance between said caps to vary.

31. A miniature optical scanner as recited in claim 25 wherein said mirror is a reflective surface coated on said mirror mounting portion of said spring plate.

32. A miniature optical scanner as recited in claim 25 wherein said mirror and spring plate are integrally formed.

33. A miniature optical scanner as recited in claim 25 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said housing forming a vacuum chamber for said scanner.

34. A miniature optical scanner as recited in claim 25 including a housing for said scanner with a window being disposed therein to allow light to enter said housing and be reflected out of said housing by said mirror, said window is disposed at an angle with respect to said base to minimize the effect of reflections from said window.

35. A miniature optical scanner as recited in claim 34 wherein said angle is greater than the maximum optical scan angle of said mirror.

36. A miniature optical scanner as recited in claim 25 wherein said spring plate includes a first connecting portion disposed on one side of said mirror mounting portion between said first and second support portions of said spring plate and a second connecting portion disposed on a side of said mirror mounting portion opposite said first connecting portion, said second connecting portion having a gap therein and means for varying the size of said gap to vary the tension in said spring plate.

37. A miniature optical scanner as recited in claim 36 wherein said clamping means includes a plurality of screws extending through said base into said spring plate.