Optical MEMS scanning micro-mirror with anti-speckle cover

1. An Optical micro-electro mechanical system (MEMS) scanning micro-mirror device comprising:

a movable scanning micro-mirrors for deflecting a light beam;

a layer of deformable transparent material arranged to be traversed by said light beam; and

a piezo-actuator cooperating with said transparent material so that when actuated, the piezo-actuator causes micro-deformation of the transparent material.

2. The optical MEMS scanning micro-mirror according to claim 1 , further comprising: a package with a transparent window substantially above a reflection side of the micro-mirrors, said layer of deformable transparent being unitary with said window.

3. The optical MEMS scanning micro-mirror according to claim 2 , further comprising:

a substrate under a back face of said mirror; wherein said piezo-actuator and said layer of deformable transparent material are provided on an outer portion of said window; and

wherein said piezo-actuator is arranged at a periphery of the layer of deformable transparent material.

4. The optical MEMS scanning micro-mirror according to claim 1 , wherein the piezo-actuator is substantially circumferential.

5. The optical MEMS scanning micro-mirror according to claim 1 , wherein the piezo-actuator is provided with a plurality of piezo-elements circumferentially arranged around the layer of deformable transparent material.

6. The optical MEMS scanning micro-mirror according to claim 2 , wherein the window is provided with a substantially flat outer face on which the piezo-actuator and the layer of deformable transparent material are attached.

7. The optical MEMS scanning micro-mirror according to claim 2 , wherein the piezo-actuator, the layer of deformable transparent material and the window are fabricated at wafer-level.

8. A method for reducing speckle in a micro-projection system adapted for projecting light on a projection surface, comprising:

providing a light with at least one coherent light source; directing light from the light source to the projection surface;

providing a scanning micro-mirror for deviating light from said light source so as to scan a projected image onto said projecting surface; and

providing a layer of deformable transparent material arranged to be traversed by said light; and providing a piezo-actuator assembly cooperating with said transparent material so that when actuated, the piezo-actuator assembly causes micro-deformation of the transparent material so as to reduce speckle.

9. The method for reducing speckle in a micro-projection system according to claim 8 , wherein the piezo-actuator is actuated so as to create deformations of the transparent material with a spatial wavelength shorter than an average outer dimension of the transparent material, thus creating waves in said transparent material.

10. The method for reducing speckle in a micro-projection system according to claim 8 , wherein the piezo-actuator is actuated with a temporal frequency adapted to change the deformation within one single pixel, between each pixel or between each successive frame.

11. A system, comprising:

a light source to emit a light beam;

a transparent material;

a moveable mirror to receive the light beam and scan the light beam across the transparent material;

an actuator coupled to the transparent material and arranged to deform the transparent material.

12. The system of claim 11 , the actuator to cause micro-deformations in the transparent material to reduce speckle.

13. The system of claim 11 , further comprising a package having an aperture, at least the moveable mirror disposed inside the package such that the aperture is above a reflection side of the moveable mirror, the transparent material covering the aperture.

14. The system of claim 13 , wherein the actuator is disposed at a periphery of the transparent material.

15. The system of claim 13 , wherein the aperture comprises a substantially flat outer face, the actuator and the transparent material attached to the substantially flat outer face.

16. The system of claim 11 , wherein the actuator is a piezo-actuator.

17. The system of claim 11 , wherein the actuator comprises a plurality of piezo-actuator elements circumferentially arranged around the transparent material.

18. The system of claim 11 , comprising a substrate, the moveable mirror, the actuator and the transparent material formed on the substrate.

19. The system of claim 11 , wherein the light beam is a coherent light beam.

20. The system of claim 11 , wherein the transparent material comprises borosilicate and the actuator comprises at least one of zirconate titanate and aluminum nitride.