Alteration of resonant mode frequency response in mechanically resonant device

Patent metadata

Field	Value
Publication number	US-11287644-B2
Application number	US-201916275409-A
Country	US
Kind code	B2
Filing date	Feb 14, 2019
Priority date	Feb 14, 2019
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

Abstract

A mechanically resonant system exhibits a resonant mode frequency response. A conductor is included on a resonant member within the mechanically resonant system. A current in the conductor causes a modification of the resonant mode frequency response when in the presence of a magnetic field. The modification of the resonant mode frequency response may include an offset in the natural frequency of the mechanically resonant system.

First claim

What is claimed is:

1. An apparatus comprising:
a first scanning mirror assembly having a first mechanically resonant scanning mirror and a first actuator device, wherein the first mechanically resonant scanning mirror includes a first conductor thereupon, that when carrying a current in the presence of a magnetic field causes a change in a resonant mode frequency response of the first mechanically resonant scanning mirror;
a second scanning mirror assembly having a second mechanically resonant scanning mirror and a second actuator device; and
a drive circuit to provide an excitation signal to the first and second actuator devices to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency, and to provide a first resonant mode offset signal to the first conductor on the first mechanically resonant scanning mirror to modify the resonant mode frequency response of the first mechanically resonant scanning mirror, where the first resonant mode offset signal comprises an alternating current (AC) signal.

2. The apparatus of claim 1 further comprising:
at least one first laser light source to create laser light pulses to be reflected by the first mechanically resonant scanning mirror; and
at least one second laser light source to create laser light pulses to be reflected by the second mechanically resonant scanning mirror.

3. The apparatus of claim 1 wherein the second mechanically resonant scanning mirror includes a second conductor thereupon, that when carrying a current in the presence of a magnetic field causes a change in a resonant mode frequency response of the second mechanically resonant scanning mirror.

4. The apparatus of claim 3 wherein the drive circuit is configured to provide a second resonant mode offset signal to the second conductor on the second mechanically resonant scanning mirror to modify a resonant mode frequency response of the second mechanically resonant scanning mirror.

5. The apparatus of claim 1 wherein the first and second actuator devices comprise piezoelectric actuator devices.

6. The apparatus of claim 1 wherein the first and second mechanically resonant scanning mirrors are single axis mirrors.

7. The apparatus of claim 1 wherein the first and second mechanically resonant scanning mirrors are dual axis mirrors.

8. A method comprising:
providing an excitation signal to first and second mechanically resonant scanning mirrors to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency; and
providing a natural frequency offset drive signal to a first conductor on the first mechanically resonant scanning mirror to modify a resonant mode frequency response of the first mechanically resonant scanning mirror when the first mechanically resonant scanning mirror is in the presence of a magnetic field, where the natural frequency offset signal comprises an alternating current (AC) signal.

9. The method of claim 8 wherein providing a natural frequency offset drive signal comprises providing a natural frequency offset drive signal to move a natural frequency of the first mechanically resonant scanning mirror closer in frequency to a natural frequency of the second mechanically resonant scanning mirror.

10. The method of claim 8 wherein providing an excitation signal to first and second mechanically resonant scanning mirrors to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency comprises providing an excitation signal to a piezoelectric actuator device.

11. The method of claim 8 wherein providing an excitation signal to first and second mechanically resonant scanning mirrors to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency comprises providing an excitation signal to an electromagnetic actuator device.

12. The method of claim 8 further comprising providing a natural frequency offset drive signal to a second conductor on the second mechanically resonant scanning mirror to modify a resonant mode frequency response of the second mechanically resonant scanning mirror when the second mechanically resonant scanning mirror is in the presence of a magnetic field.

13. The method of claim 8 wherein the alternating current (AC) signal is in phase with the excitation signal.

14. The method of claim 8 wherein the alternating current (AC) signal is out of phase with the excitation signal.

15. The method of claim 12 further comprising providing a direct current (DC) signal to the first second conductor to modify an angular offset of the second mechanically resonant scanning mirror.

16. The method of claim 8 further comprising providing a direct current (DC) signal to the first conductor to modify an angular offset of the first mechanically resonant scanning mirror.

17. The method of claim 8 wherein providing an excitation signal to first and second mechanically resonant scanning mirrors to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency comprises providing excitation signals to the first and second mechanically resonant scanning mirrors to cause the first and second mechanically resonant scanning mirrors to oscillate at a common frequency and a phase relationship such that the first and second mechanically resonant scanning mirrors are synchronized both in time and angular position.

18. An apparatus comprising:
a first scanning mirror assembly having a first mechanically resonant scanning mirror and a first actuator device, wherein the first mechanically resonant scanning mirror includes a first conductor thereupon, that when carrying a current in the presence of a magnetic field causes a change in a resonant mode frequency response of the first mechanically resonant scanning mirror;
a second scanning mirror assembly having a second mechanically resonant scanning mirror and a second actuator device;
a drive circuit to provide an excitation signal to the first and second actuator devices, where the excitation signal is configured to drive the first mechanically resonant scanning mirror to oscillate at first frequency and drive the second mechanically resonant scanning mirror to oscillate at a second frequency, and wherein the drive circuit further provides a first natural frequency offset signal to the first conductor on the first mechanically resonant scanning mirror to modify the resonant mode frequency response of the first mechanically resonant scanning mirror, where the natural frequency offset signal comprises an alternating current (AC) signal that causes the first mechanically resonant scanning mirror to oscillate at a third frequency different than the first frequency and closer to the second frequency when driven by the excitation signal.

19. The apparatus of claim 18 wherein the second mechanically resonant scanning mirror includes a second conductor thereupon, and wherein the drive circuit further provides a second natural frequency offset signal to the second conductor on the second mechanically resonant scanning mirror to modify the resonant mode frequency response of the second mechanically resonant scanning mirror and cause the second mechanically resonant scanning mirror to oscillate at a fourth frequency different than the second frequency when driven by the excitation signal.

20. The apparatus of claim 19 wherein the first natural frequency offset signal and the second natural frequency offset signal are such that the first and second mechanically

Assignees

• Microvision Inc

Inventors

• Morarity Jonathan A
• Ellis Matthew
• Adkins Christopher Brian

Classifications

• G02B27/0172

  characterised by optical features · CPC title

• H04N3/08

  having a moving reflector · CPC title

• H04N9/3194

  including sensor feedback · CPC title

• G02B26/105

  with one or more pivoting mirrors or galvano-mirrors (G02B26/101 takes precedence) · CPC title

• G02B26/0833

  the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B) · CPC title