Method for controlling position of a linear MEMS mirror with variable resolution and/or light intensity

• US 10,642,025 B2
• Filed: 09/29/2016
• Issued: 05/05/2020
• Est. Priority Date: 03/30/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Duvdevany, Offir, Sharon, Dadi, Sourani, Sason
• Primary Examiner(s): Won, Bumsuk
• Assistant Examiner(s): Washington, Tamara Y.
• Application Number:
  US15/280,691
• Publication Number:
  US 20170285327A1
• Time in Patent Office: 1,314 Days
• Field of Search: 3591961-2263
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 7/1821 for rotating or oscillating mirrors
• CPC Class Codes: G03B 21/008 using micromirror devices

Abstract

The method for controlling an angular position of a MEMS mirror, includes: applying a first driving moment to the MEMS mirror to generate a rotational scanning movement of the mirror; and, at a zooming instant, applying a second driving moment to the MEMS mirror, wherein the second driving moment is equal to the first driving moment plus an extra moment. The extra moment may be a DC offset. After a transient period of time from zooming instant, a third driving moment M₂=k{dot over (θ)}₂t is applied. The first and third driving moment are variable linearly with time. The driving moments are applied to torsional springs of the mirror.

Claims

1. A method for controlling an angular position of a MEMS mirror, comprising:

applying a first driving moment to the MEMS mirror, applying the first driving moment generating a rotational scanning movement of the mirror; and

performing a zooming, which modifies at least one of a resolution and a light intensity of the MEMS mirror, by applying a second driving moment to the MEMS mirror, wherein the second driving moment is equal to the first driving moment plus an extra driving moment, wherein the extra driving moment is a fixed moment.

2. The method according to claim 1, wherein the first driving moment is variable linearly with time.

3. The method according to claim 2, wherein the first and second driving moments are applied to torsional springs of the mirror and the first driving moment is given by the equation:

k{dot over (θ

)}₁t=M₁

wherein k is a stiffness constant of the springs, θ

is a first derivative of an angular position of the mirror, and t is time.

4. The method according to claim 1, wherein the first and second driving moments are applied to torsional springs of the mirror and the extra driving moment (M-M₁) is equal to:

5. The method according to claim 1, comprising applying a third driving moment M₂=k{dot over (θ

)}₂t after a transient period of time t from a zooming instant, wherein k is a stiffness constant of the springs, and {dot over (θ

)}₂ is a speed of the mirror.

6. The method according to claim 5, wherein applying the first driving moment comprises rotating the MEMS mirror at a first constant speed {dot over (θ

)}₁ and applying the third driving moment comprises rotating the MEMS mirror at the speed {dot over (θ

)}₂, which is constant.

7. The method according to claim 1, comprising:

reading from a conversion table a control electrical quantity corresponding to an instant driving moment; and

controlling rotation of the MEMS mirror according to the control electrical quantity read from the conversion table.

8. A method, comprising:

controlling an angular position of a MEMS mirror, the controlling including;

applying a first driving moment to the MEMS mirror, applying the first driving moment generating a rotational scanning movement of the mirror; and

modifying at least one of a resolution and a light intensity of the MEMS mirror by applying a second driving moment to the MEMS mirror, wherein the second driving moment is equal to the first driving moment plus a fixed moment.

9. The method according to claim 8, wherein the first driving moment is variable linearly with time.

10. The method according to claim 8, wherein the first and second driving moments are applied to torsional springs of the mirror and the first driving moment is given by the equation:

k{dot over (θ

)}₁t=M₁

wherein k is a stiffness constant of the springs, {dot over (θ

)}₁ is a first derivative of an angular position of the mirror, and t is time.

11. The method according to claim 8, wherein the first and second driving moments are applied to torsional springs of the mirror and the extra driving moment (M-M₁) is equal to:

12. The method according to claim 8, comprising applying a third driving moment M₂=k{dot over (θ

)}₂t after a transient period of time t from a zooming instant, wherein k is a stiffness constant of the springs, and {dot over (θ

)}₂ is a speed of the mirror.

13. The method according to claim 12, wherein applying the first driving moment comprises rotating the MEMS mirror at a first constant speed {dot over (θ

)}₁ and applying the third driving moment comprises rotating the MEMS mirror at the speed {dot over (θ

)}₂, which is constant.

14. The method according to claim 8, comprising:

reading from a conversion table a control electrical quantity corresponding to an instant driving moment; and

controlling rotation of the MEMS mirror according to the control electrical quantity read from the conversion table.

15. A method, comprising:

controlling an angular position of a MEMS mirror, the controlling including;

applying a first driving moment to the MEMS mirror, applying the first driving moment generating a rotational scanning movement of the mirror;

performing a zooming at a zooming instant by applying a second driving moment to the MEMS mirror, wherein the second driving moment is equal to the first driving moment plus an extra driving moment; and

applying a third driving moment M₂=k{dot over (θ

)}₂t after a transient period of time t from the zooming instant, wherein k is a stiffness constant of the springs, and {dot over (θ

)}₂ is a speed of the mirror.

16. The method according to claim 15, wherein the first and second driving moments are applied to torsional springs of the mirror and the first driving moment is given by the equation:

k{dot over (θ

)}₁t=M₁

wherein k is a stiffness constant of the springs, {dot over (θ

)}₁ is a first derivative of an angular position of the mirror, and t is time.

17. The method according to claim 15, wherein the first and second driving moments are applied to torsional springs of the mirror and the extra driving moment (M-M₁) is equal to:

18. The method according to claim 15, wherein applying the first driving moment comprises rotating the MEMS mirror at a first constant speed {dot over (θ

)}₁ and applying the third driving moment comprises rotating the MEMS mirror at the speed {dot over (θ

)}₂, which is constant.

19. The method according to claim 15, comprising:

reading from a conversion table a control electrical quantity corresponding to an instant driving moment; and

controlling rotation of the MEMS mirror according to the control electrical quantity read from the conversion table.