Low vibration resonant scanning unit for miniature optical display apparatus

• US 5,009,473 A
• Filed: 11/13/1989
• Issued: 04/23/1991
• Est. Priority Date: 05/31/1988
• Status: Expired due to Fees

• Current Assignee: Reflection Technology, Inc.
• Original Assignee: Reflection Technology, Inc.
• Inventors: Feldstein, Michael A., Hunter, Gregory H., Wells, Benjamin A.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Ben, Loha
• Application Number:
  US07/434,351
• Time in Patent Office: 526 Days
• Field of Search: 350/6.6, 350/6.91, 350/486, 350/487, 250/234, 250/235, 358/208, 310/38, 310/39, 340/755, 340/752, 156/425, 156/175
• US Class Current: 359/214.1
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G06K 7/10653 using flexible or piezoelectric means

Abstract

A resonant scanning unit utilizes a "tuning fork" design with a mirror mounted on one arm of the tuning fork and a counterbalance mass mounted on the other arm. A voice coil electromagnetic motor mounted between the arms causes the arms to move in opposite directions. Light generated by a line of LEDs is reflected from the oscillating mirror to generate a raster display. Reaction forces generated by the motions of the mirror and counterbalance mass cancel at the device base, reducing vibration. In addition, the inventive structure allows placement of the mirror pivot point away from the center of the mirror which allows display devices constructed with the structure to be reduced in size. A second embodiment is disclosed in which molded construction reduces assembly cost and time and allows precise tuning of the reaction forces.

Claims

1. In a resonant electromechanical scanning unit having a base, a mirror, a mirror frame attached to said mirror, a first spring connecting said mirror frame to said base to allow said mirror and said mirror frame to oscillate relative to said base, a counterbalance mass, a second spring connecting said counterbalance mass to said base to allow said counterbalance mass to oscillate relative to said base and a drive motor for causing said mirror and said counterbalance mass to oscillate, the improvement wherein at least a portion of said mirror frame and said base are comprised of a moldable material and are fabricated by a molding process and said first spring is inserted into said base and into said portion of said mirror frame during said molding process to form an integral mirror mount unit.

2. In a resonant electromechanical scanning unit, the improvement according to claim 1 wherein at least a portion of said counterbalance mass and said base are comprised of a moldable material and are fabricated by a molding process and said second spring is inserted into said base and into said portion of said counterbalance mass during said molding process to form an integral counterbalance mass unit.

3. In a resonant electromechanical scanning unit, the improvement according to claim 2 wherein said counterbalance mass comprises a first portion into which said second spring is inserted and a second portion which comprises most of the mass of said counterbalance mass.

4. In a resonant electromechanical scanning unit, the improvement according to claim 3 wherein said counterbalance mass second portion is comprised of a moldable material and is fabricated by a molding process.

5. In a resonant electromechanical scanning unit, the improvement according to claim 1, wherein said first spring has a plurality of holes therein so that, during said molding process, said moldable material comprising said base and said mirror frame enters said plurality of holes in said first spring to lock said first spring and said mirror frame together and to lock said first spring and said base together.

6. In a resonant electromechanical scanning unit, the improvement according to claim 2, wherein said second spring has a plurality of holes therein so that, during said molding process, said moldable material comprising said base and said counterbalance mass enters said plurality of holes in said second spring to lock said second spring and said counterbalance mass together and to lock said second spring and said base together.

7. In a resonant electromechanical scanning unit, the improvement according to claim 2, further comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said second spring to change the frequency at which said counterbalance mass oscillates relative to said base.

8. In a resonant electromechanical scanning unit, the improvement according to claim 7, wherein said movable tuning mass comprises a manually-bendable tuning wire.

9. In a resonant electromechanical scanning unit, the improvement according to claim 2, further comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said first spring to change the frequency at which said mirror and mirror frame oscillate relative to said base.

10. In a resonant electromechanical scanning unit, the improvement according to claim 9, wherein said movable tuning mass comprises a manually-bendable tuning wire.

11. A resonant electromechanical scanning unit comprising:

a base having a first subunit comprised of a moldable material and being fabricated by a first molding process and a second subunit comprised of a moldable material and being fabricated by a second molding process;

a mirror;

a mirror frame attached to said mirror having at least a portion thereof comprised of a moldable material and being fabricated by said first molding process;

a first spring being inserted into said first base subunit and into said portion of said mirror frame during said first molding process to form an integral mirror mount unit in which said mirror frame can oscillate relative to said first base subunit;

a counterbalance mass having at least a portion thereof comprised of a moldable material and being fabricated by said second molding process;

a second spring inserted into said second base subunit and into said portion of said counterbalance mass during said second molding process to form an integral counterbalance mass unit wherein said counterbalance mass can oscillate relative to said second base subunit;

a drive motor for causing said mirror mount unit and said counterbalance mass unit to oscillate.

12. A resonant electromechanical scanning unit according to claim 11, wherein said first base subunit is attached to said second base subunit to complete said scanning unit.

13. A resonant electromechanical scanning unit according to claim 12, wherein said counterbalance mass comprises a first portion into which said second spring is inserted and a second portion which comprises most of the mass of said counterbalance mass.

14. A resonant electromechanical scanning unit according to claim 13, wherein said counterbalance mass second portion is comprised of a moldable metal and is fabricated by a third molding process.

15. A resonant electromechanical scanning unit according to claim 14, wherein said first spring has a plurality of holes therein so that, during said first molding process, said moldable material comprising said first base subunit and said mirror frame enters said plurality of holes in said first spring to lock said first spring and said mirror frame together and to lock said first spring and said first base subunit together.

16. A resonant electromechanical scanning unit according to claim 15, wherein said second spring has a plurality of holes therein so that, during said second molding process, said moldable material comprising said second base subunit and said counterbalance mass enters said plurality of holes in said second spring to lock said second spring and said counterbalance mass together and to lock said second spring and said second base subunit together.

17. A resonant electromechanical scanning unit according to claim 16, further comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said second spring to change the frequency at which said counterbalance mass oscillates relative to said second base subunit.

18. A resonant electromechanical scanning unit according to claim 17, wherein said movable tuning mass comprises a manually-bendable tuning wire.

19. A resonant electromechanical scanning unit according to claim 16, further comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said first spring to change the frequency at which said mirror and mirror frame oscillate relative to said first base subunit.

20. A resonant electromechanical scanning unit according to claim 19, wherein said movable tuning mass comprises a manually-bendable tuning wire.

21. In a resonant electromechanical scanning unit having a base, a mirror, a mirror frame attached to said mirror, a first spring connecting said mirror frame to said base to allow said mirror and said mirror frame to oscillate relative to said base, a counterbalance mass, a second spring connecting said counterbalance mass to said base to allow said counterbalance mass to oscillate relative to said base and a drive motor for causing said mirror and said counterbalance mass to oscillate, the improvement comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said second spring to change the frequency at which said counterbalance mass oscillates relative to said base.

22. In a resonant electromechanical scanning unit, the improvement according to claim 21, wherein said movable tuning mass comprises a manually-bendable tuning wire.

23. In a resonant electromechanical scanning unit having a base, a mirror, a mirror frame attached to said mirror, a first spring connecting said mirror frame to said base to allow said mirror and said mirror frame to oscillate relative to said base, a counterbalance mass, a second spring connecting said counterbalance mass to said base to allow said counterbalance mass to oscillate relative to said base and a drive motor for causing said mirror and said counterbalance mass to oscillate, the improvement comprising a movable tuning mass attached to said counterbalance mass, which movable tuning mass can be manually moved toward or away from said first spring to change the frequency at which said mirror and said mirror frame oscillate relative to said base.

24. In a resonant electromechanical scanning unit, the improvement according to claim 23, wherein said movable tuning mass comprises a manually-bendable tuning wire.