Driving multiple resonance MEMS mirrors with a single frequency

Patent metadata

Field	Value
Publication number	US-11474425-B2
Application number	US-201916540557-A
Country	US
Kind code	B2
Filing date	Aug 14, 2019
Priority date	Aug 14, 2019
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

A control circuit includes a first control circuit generating a first drive control signal from a pre-drive signal (that is a frequency at which an opening angle of the first and second mirrors is equal) for the first mirror. A second control circuit generates a second drive control signal from the pre-drive signal for the second mirror. First and second drivers generate first and second drive signals for the first and second mirrors from the first and second drive control signals. The first and second drive control signals are generated so that the first and second drive signals each have a same frequency as the pre-drive signal but are different in amplitude from one another to cause the first and second mirrors to move at a same frequency, with a same and substantially constant given opening angle as one another, and in phase with one another.

First claim

The invention claimed is:

1. A projector, comprising:
a first microelectromechanical (MEMS) mirror;
a second MEMS mirror;
a mirror pre-driver configured to generate a pre-drive signal, the pre-drive signal having a frequency that is a frequency at which an opening angle of the first MEMS mirror is equal to an opening angle of the second MEMS mirror, wherein the frequency of the pre-drive signal is neither a resonance frequency of the first MEMS mirror nor a resonance frequency of the second MEMS mirror;
a first mirror control circuit configured to generate a first drive control signal from the pre-drive signal for the first MEMS mirror;
a first mirror driver configured to generate a first drive signal for the first MEMS mirror from the first drive control signal;
a second mirror control circuit configured to generate a second drive control signal from the pre-drive signal for the second MEMS mirror; and
a second mirror driver configured to generate a second drive signal for the second MEMS mirror from the second drive control signal;
wherein the first and second drive control signals are generated by the first and second mirror control circuits so that the first and second drive signals each have a same frequency as the pre-drive signal but each have a different amplitude and phase from one another so as to cause the first and second MEMS mirrors to move at a same frequency, with a same and substantially constant given opening angle, and in phase with one another.

2. The projector of claim 1 , wherein the frequency at which the opening angle of the first MEMS mirror is equal to the opening angle of the second MEMS mirror is an average of a resonance frequency of the first MEMS mirror and a resonance frequency of the second MEMS mirror.

3. The projector of claim 1 , wherein the first and second mirror control circuits generate the first and second drive control signals so that the first and second drive signals are different in amplitude and phase from one another.

4. The projector of claim 1 , further comprising a red-green-blue (RGB) laser source configured to project RGB laser beams that impinge upon the first and second MEMS mirrors; and further comprising a VR headset housing having the RGB laser source, the first and second MEMS mirrors, mirror pre-driver, first and second mirror control circuits, and first and second mirror drivers therein.

5. The projector of claim 1 ,
further comprising a first mirror position sensor associated with the first MEMS mirror and a second mirror position sensor associated with the second MEMS mirror;
further comprising a first zero cross detector associated with the first mirror position sensor and a second zero cross detector associated with the second mirror position sensor;
wherein the first and second mirror position sensors are configured to generate first and second mirror sense signals indicating peak opening angles of the first and second MEMS mirrors;
wherein the first mirror control circuit generates the first drive control signal as a function of the pre-drive signal, the first mirror sense signal, and detected zero crosses of a first mirror sense signal generated by the first MEMS mirror in response to the first drive signal; and
wherein second mirror control circuit generates the second drive control signal as a function of the pre-drive signal, the second mirror sense signal, and detected zero crosses of a second mirror sense signal generated by the second MEMS mirror in response to the second drive signal.

6. A projector, comprising:
a first microelectromechanical (MEMS) mirror;
a second MEMS mirror;
a mirror pre-driver configured to generate a pre-drive signal, the pre-drive signal having a frequency that is a frequency at which an opening angle of the first MEMS mirror is equal to an opening angle of the second MEMS mirror, wherein the frequency of the pre-drive signal is neither a resonance frequency of the first MEMS mirror nor a resonance frequency of the second MEMS mirror;
a first mirror control circuit configured to generate a first drive control signal from the pre-drive signal for the first MEMS mirror;
a first mirror driver configured to generate a first drive signal for the first MEMS mirror from the first drive control signal;
a second mirror control circuit configured to generate a second drive control signal from the pre-drive signal for the second MEMS mirror; and
a second mirror driver configured to generate a second drive signal for the second MEMS mirror from the second drive control signal;
wherein the first and second drive control signals are generated by the first and second mirror control circuits so as to cause the first and second MEMS mirrors to move at a same frequency, with a same and substantially constant given opening angle.

7. The projector of claim 6 , wherein the frequency at which the opening angle of the first MEMS mirror is equal to the opening angle of the second MEMS mirror is an average of a resonance frequency of the first MEMS mirror and a resonance frequency of the second MEMS mirror.

8. The projector of claim 6 , wherein the first and second mirror control circuits generate the first and second drive control signals so that the first and second drive signals are different in amplitude from one another.

9. The projector of claim 6 , further comprising a red-green-blue (RGB) laser source configured to project RGB laser beams that impinge upon the first and second MEMS mirrors; and further comprising a VR headset housing having the RGB laser source, the first and second MEMS mirrors, mirror pre-driver, first and second mirror control circuits, and first and second mirror drivers therein.

10. The projector of claim 6 ,
further comprising a first mirror position sensor associated with the first MEMS mirror and a second mirror position sensor associated with the second MEMS mirror;
wherein the first and second mirror position sensors are configured to generate first and second mirror sense signals indicating peak opening angles of the first and second MEMS mirrors;
wherein the first mirror control circuit generates the first drive control signal as a function of the pre-drive signal and the first mirror sense signal; and
wherein the second mirror control circuit generates the second drive control signal as a function of the pre-drive signal and the second mirror sense signal.

11. A control circuit for driving first and second movable mirrors, the control circuit comprising:
a mirror pre-driver configured to generate a pre-drive signal, the pre-drive signal having a frequency that is that is a frequency at which an opening angle of the first movable mirror is equal to an opening angle of the second movable mirror;
a first mirror control circuit configured to generate a first drive control signal from the pre-drive signal for the first movable mirror in response to an operating characteristic of the first movable mirror;
a first mirror driver configured to generate a first drive signal for the first movable mirror from the first drive control signal;
a second mirror control circuit configured to generate a second drive control signal from the pre-drive signal for the second movable mirror in response to an operating characteristic of the second movable mirror; and
a second mirror driver configured to generate a second drive signal for the second movable mirror from the second drive control signal;
wherein the first and second drive control signals are generated by the first and second mirror control circuits so that the first and second drive signals each have a same frequency as the pre-drive signal but are different in amplitude from one another so as to cause the first and sec

Assignees

• St Microelectronics Ltd

Inventors

• Yaser Eli
• Amor Guy
• Nachmias Yotam
• Sharon Dadi
• Nagola Sivan

Classifications

• 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

• G02B26/101 Primary

  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 title

• G03B21/28 Primary

  Reflectors in projection beam {(in illumination beam G03B21/2066)} · CPC title

• G03B21/2033

  LED or laser light sources · CPC title

• H04N9/3141 Primary

  Constructional details thereof (details not peculiar to the presence of an electronic spatial light modulator G03B21/14) · CPC title