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DE-112016004661-B4 - Electromechanical design of MEMS scanner mirrors

DE112016004661B4DE 112016004661 B4DE112016004661 B4DE 112016004661B4DE-112016004661-B4

Abstract

Device (100, 200, 300, 400, 500, 600, 700, 2000) that includes the following: a reflective section (102, 502, 602); a frame arranged at least partially around the reflective section (104, 504, 604); a drive coil (112, 512, 612) for receiving a first electric current to induce a movement of the reflecting section about a first axis in response to the received electric current; and a sensing coil (114, 514, 614) which is at least partially arranged around the drive coil and is physically separated from the reflecting section, wherein the induced motion serves to induce a second electric current in the sensing coil, wherein the second electric current serves to indicate a position of the reflecting section around the first axis (220, 720), wherein the drive coil is located on the reflective section and the sensing coil is arranged on the frame.

Inventors

  • Julien Gamet
  • ALEXANDRE FOTINOS
  • NICHOLAS ABELE

Assignees

  • Google LLC (n.d.Ges.d. Staates Delaware)

Dates

Publication Date
20260513
Application Date
20160930
Priority Date
20151221

Claims (19)

  1. Device (100, 200, 300, 400, 500, 600, 700, 2000) comprising: a reflecting section (102, 502, 602); a frame (104, 504, 604) arranged at least partially around the reflecting section; a drive coil (112, 512, 612) for receiving a first electric current to induce a movement of the reflecting section about a first axis in response to the received electric current; and a sensing coil (114, 514, 614) which is at least partially arranged around the drive coil and is physically separated from the reflecting section, wherein the induced movement serves to induce a second electric current in the sensing coil, wherein the second electric current serves to indicate a position of the reflecting section around the first axis (220, 720), where the drive coil is located on the reflecting section and the sensing coil is arranged on the frame.
  2. Device after Claim 1 , wherein the device forms a microelectromechanical (MEMS) mirror, wherein the reflecting section serves to receive a light beam (212, 712, 2005) from a light source (210, 710, 2003), wherein the induced motion serves to sweep the light beam over a projection surface (2010) in order to project an image.
  3. Device after Claim 1 , wherein the drive coil is located near the reflecting section.
  4. Device after Claim 3 , comprising a substrate (401) wherein the reflecting section is arranged on the substrate and the drive coil is embedded in the substrate below the reflecting section.
  5. Device after Claim 4 , comprising: an outer frame (506, 606) arranged at least partially around the frame; and an outer drive coil (516, 616) arranged at least partially around the sensing coil, the outer drive coil serving to receive a third electric current in order to induce a second movement of the reflecting section about a second axis in response to the received electric current.
  6. Device after Claim 5 , comprising torsion bars (542,642) to mechanically couple the frame to the outer frame, the torsion bars serving to provide the induced motion about the first axis.
  7. Device after Claim 6 , wherein the second electric current serves to indicate at least one of the positions of the reflecting section around the first axis or the second axis.
  8. Device after Claim 7 , comprising the following: a static section (546, 646) and external torsion bars (544, 644) to mechanically couple the outer frame to the static section, the external torsion bars serving to provide the induced second movement about the second axis.
  9. Device after one of the Claims 6 until 8 , wherein the outer drive coil comprises 5 to 120 individual coils, the individual coils being spaced 2 to 15 µm apart.
  10. Device after one of the Claims 1 until 8 , wherein the drive coil comprises 5 to 60 individual coils, the individual coils being spaced 2 to 15 µm apart.
  11. Device after one of the Claims 1 until 8 , wherein the sensing coil comprises 5 to 15 individual coils, the individual coils being spaced 2 to 15 µm apart.
  12. Device after one of the Claims 1 until 8 , wherein at least one perimeter of the reflecting section or frame comprises a square, a rectangle, an oval, a circle or a polygon.
  13. System (200, 700, 2000) comprising: a light source (210, 710, 2003) for emitting a light beam (212, 712, 2005); and a microelectromechanical (MEMS) mirror (100, 300, 400, 500, 600, 2006), the MEMS mirror comprising: a reflecting section (102, 502, 602) for receiving the light beam; a frame (104, 504, 604) arranged at least partially around the reflecting section; a drive coil (112, 512, 612) for receiving a first electric current to induce a movement of the reflecting section about a first axis in response to the received electric current, in order to project the light beam onto a projection surface (2010); and a sensing coil (114, 514, 614) which is arranged at least partially around the drive coil and is physically separated from the reflecting section, wherein the induced movement serves to induce a second electric current in the sensing coil, the second electric current serving to indicate a position of the reflecting section about the first axis (220, 720), where the drive coil is located on the reflecting section and the sensing coil is arranged on the frame.
  14. System according Claim 13 , wherein the drive coil is located near the reflecting section.
  15. System according Claim 14 , wherein the MEMS mirror comprises a substrate (401), wherein the reflecting section is arranged on the substrate and the drive coil is embedded in the substrate below the reflecting section.
  16. System according to Claim 15 , wherein the MEMS mirror comprises: an outer frame (506, 606) arranged at least partially around the frame; and an outer drive coil (516, 616) arranged at least partially around the sensing coil, the outer drive coil serving to receive a third electric current in order to induce a second movement of the reflecting section about a second axis in response to the received electric current.
  17. System according Claim 16 , wherein the MEMS mirror includes torsion bars (542, 642) to mechanically couple the frame to the outer frame, the torsion bars serving to provide the induced motion about the first axis.
  18. System according Claim 17 , wherein the second electric current serves to indicate at least one of the positions of the reflecting section around the first axis or the second axis.
  19. System according to Claim 18 , wherein the MEMS mirror comprises: a static section (546, 646) and external torsion bars (544, 644) to mechanically couple the outer frame to the static section, the external torsion bars serving to provide the induced second motion about the second axis.

Description

AREA OF INVENTION The embodiments described herein generally relate to microelectromechanical (MEMS) scanner mirrors and MEMS scanner mirror projection systems. The proposed solution is defined by claims 1 and 13. BACKGROUND MEMS scanner mirrors based on laser projection systems show great promise for use in ultra-small and portable applications. The use of a drive coil and a sensing coil in a MEMS scanner mirror is particularly advantageous in this context. WO 2011/095231 A1 , the EP 1 338 912 A1 and the US 6,464,363 B1 The basic principle is known. In one example of a MEMS scanner mirror projection system, a mirror can be arranged to rotate about two axes at right angles to each other to display pixels of a projected image onto a projection surface. Specifically, the exemplary MEMS scanner mirror can reflect light emitted from one or more light sources to project the image. In some MEMS scanner mirror projection systems, two mirrors can be used, each of which can be arranged to rotate about one of two axes at right angles to each other. Laser light sources can be modulated while the MEMS mirror rotates to effectively pulse and sequentially display pixels to produce a projected image. Specifically, the MEMS mirror can rotate to sweep across an entire area of the projected image with reflected light quickly enough to produce an image that appears stable to the human eye. Advantageously, pixels can be projected only when needed according to such a method, which is why the laser light source(s) can be turned off for parts of the projected image that are black, in order to save power. One factor that can affect the displayed image quality of a MEMS-based projection system is the precision of the synchronization of the modulated laser pulses with the rotation of the mirror. If the synchronization between the modulated laser pulses and the mirror's rotation is insufficient, the same pixel may be pulsed at a slightly different timing from one frame to the next, resulting in a blurred image. Precise synchronization of the modulated laser pulses with respect to the mirror's rotation may require accurate sensing of the mirror's rotational angular position. A second factor that can influence image quality is the degree to which the MEMS mirror remains optically flat during operation. During operation, a MEMS mirror may be subjected to forces that can induce its bending; this phenomenon is sometimes referred to as dynamic deformation. Bending or other curvature of the mirror can induce a corresponding distortion of the generated image pixels, which can also be a cause of perceived image blurriness. List of characters 1 shows a first example of a MEMS mirror.2 shows a first example of a MEMS scanner mirror projection system.3 shows a second example of a MEMS mirror.4 shows a third example of a MEMS mirror.5 This shows a fourth example of a MEMS mirror.6 shows a fifth example of a MEMS mirror.7 shows a second example of a MEMS scanner mirror projection system.8 shows a first logic flow example.9 shows a second logic flow example.10 shows an example of a computer-readable medium.11 shows a first example system.12 shows a second example system. DETAILED DESCRIPTION Several examples generally relate to electromechanical designs for MEMS scanner mirrors. In some examples, a drive coil may be arranged on a reflective portion of a MEMS scanner mirror. In some examples, a sensing coil may be arranged partially or completely on an outer frame portion of the MEMS scanner mirror. In other words, the drive coil may be located inside the sensing coil. In some examples, a multi-axis MEMS scanner mirror may be provided with a sensing coil arranged between two drive coils, each drive coil being configured to induce rotation of the MEMS scanner mirror in one direction along one of the axes. Further examples are described and claimed. 1 Figure 1 shows a block diagram of a MEMS scanner mirror 100 or “MEMS mirror” arranged according to various examples in the present disclosure. The MEMS mirror 100 can represent a MEMS mirror that may be implemented in a MEMS scanner mirror projection system. In particular, the MEMS mirror could be configured to sweep light beams across a projection surface while the light beams are modulated and/or pulsed to form pixels to display an image on the projection surface. As shown, the MEMS mirror 100 can comprise a reflective section 102 and a frame 104. In general, the reflective section 102 and the frame 104 can be freestanding, movable parts, with the frame 104 generally connected to a fixed, non-movable section. The reflective section 102 can generally comprise a section of the MEMS mirror 100 on which a reflective surface has been applied, deposited, or otherwise created. The frame 104 can generally comprise a section of the MEMS mirror 100 that surrounds the reflective section 102. The MEMS mirror 100 can comprise a drive coil 112 and a sensing coil 114. Generally, the drive coil 112 can be arranged ins