CN112782845B

CN112782845B - MEMS scanning mirror and laser projector

Info

Publication number: CN112782845B
Application number: CN202011635207.8A
Authority: CN
Inventors: 林育菁; 畠山庸平
Original assignee: Goertek Inc
Current assignee: Goertek Inc
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2023-02-21
Anticipated expiration: 2040-12-31
Also published as: CN112782845A

Abstract

The invention discloses an MEMS scanning mirror and a laser projector. The MEMS scanning mirror comprises a support, a reflecting mirror, a first piezoelectric actuator and a second piezoelectric actuator, wherein the first piezoelectric actuator and the second piezoelectric actuator are respectively used as a cantilever, the first piezoelectric actuator and the second piezoelectric actuator are used for enabling the reflecting mirror to rotate around a first rotating shaft, the MEMS scanning mirror further comprises a first sensing beam, one end of the first sensing beam is connected with the support, the other end of the first sensing beam is connected with one side of the reflecting mirror, and a first angle sensor used for sensing the deflection angle of the reflecting mirror rotating around the first rotating shaft is arranged on the first sensing beam. The implementation mode can avoid the obstruction to the rotation of the reflector, improve the precision of the deflection angle detection of the reflector and is beneficial to realizing the miniaturization of the MEMS scanning mirror.

Description

MEMS scanning mirror and laser projector

Technical Field

The invention relates to the technical field of laser projection. And more particularly, to a MEMS scanning mirror and a laser projector.

Background

The laser projector adopting the MEMS (Micro Electro Mechanical System) scanning mirror has the advantages of low cost, miniaturization and the like, and has wide market prospect.

The traditional MEMS scanning mirror usually adopts a torsion bar actuating mode, the reflecting mirror is driven by two, three or more torsion bars supporting the reflecting mirror to incline and twist so as to execute optical scanning, a resonance drive is adopted to realize a large scanning angle, and the resonance frequency of the inclined movement of the reflecting mirror needs to be matched with the driving frequency through structural design.

In order to maintain a resonance state when driving the MEMS scanning mirror or monitoring the mirror angle, it is a current practice to provide an angle sensor for sensing the deflection angle of the mirror, and a driver controls a driving voltage or a driving frequency applied to an actuator according to a signal output from the angle sensor to drive the mirror to rotate. For a traditional torsion bar type MEMS scanning mirror, the angle sensor is an angle sensor adopting piezoelectric effect or piezoresistive effect and arranged at the edge position of a torsion bar.

For applications with relatively low driving frequencies, it is necessary to use a lower resonance frequency, for which reason the prior art also proposes a solution using an external piezoelectric actuator forming a curved cantilever (i.e. a folded spring structure, a plate hinge) as a design suitable for low frequency driving to lower the resonance frequency. For example, as shown in fig. 1, the two-dimensional MEMS scanning mirror includes: a reflector 10; a movable support 11 (inner movable frame), the movable support 11 surrounding the mirror 10 to support the mirror 10 by a pair of

torsion bars

12a and 12 b; first and second internal

piezoelectric actuators

13a and 13b, the first and second internal

piezoelectric actuators

13a and 13b being fixed between the movable support 11 and the

torsion bars

12a and 12b, respectively, and serving as cantilevers for rotating the mirror 10 about the X-axis by the

torsion bars

12a and 12b, respectively; a fixed support 14 (outer fixed frame), the fixed support 14 surrounding the movable support 11; and first and second external

piezoelectric actuators

15a and 15b, respectively, fixed between the fixed support 14 and the movable support 11 and respectively serving as a bending cantilever for rotating the mirror 10 around the Y axis (the Y axis is perpendicular to the X axis) via the movable support 11, thereby implementing two-dimensional scanning, wherein the driving signal for driving the first and second internal

piezoelectric actuators

13a and 13b is typically a sine wave or rectangular wave signal having a frequency of 20kHz or more, and the driving signal for driving the first and second external

piezoelectric actuators

15a and 15b is typically a sawtooth wave signal having a frequency of about 60Hz (i.e., the X axis is a fast axis and the Y axis is a slow axis), thereby implementing fast lateral scanning and slow longitudinal scanning of the two-dimensional MEMS scanning mirror. In the two-dimensional MEMS scanning mirror structure as shown in fig. 1 using an external piezoelectric actuator forming a bent cantilever, for the detection of the deflection angle of the mirror 10 rotating around the Y axis, as shown in fig. 2, it is a conventional way to provide the edge of the movable support 11 with a sensing beam 16, and to provide an angle sensor (not shown in fig. 2) on the sensing beam 16 for sensing the deflection angle of the mirror 10 rotating around the Y axis. However, this method causes an obstacle to the rotation of the mirror 10, and it is difficult to accurately drive the mirror 10 while following the resonance frequency.

Therefore, it is desirable to provide a new MEMS scanning mirror and laser projector.

Disclosure of Invention

An object of the present invention is to provide a MEMS scanning mirror and a laser projector to solve at least one of the problems of the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides an MEMS scanning mirror, which comprises a support, a reflecting mirror, a first piezoelectric actuator and a second piezoelectric actuator, wherein the first piezoelectric actuator and the second piezoelectric actuator are respectively used as a cantilever, the first piezoelectric actuator and the second piezoelectric actuator are used for enabling the reflecting mirror to rotate around a first rotating shaft, the MEMS scanning mirror further comprises a first sensing beam, one end of the first sensing beam is connected with the support, the other end of the first sensing beam is connected with one side of the reflecting mirror, and a first angle sensor used for sensing a deflection angle of the reflecting mirror rotating around the first rotating shaft is arranged on the first sensing beam.

Optionally, one end of the first sensing beam connected to the support and the other end connected to the mirror are respectively located on the first rotating shaft.

Optionally, the first piezoelectric actuator and the second piezoelectric actuator form a bending cantilever respectively.

Optionally, the first sense beam is disposed around one side of the first piezoelectric actuator.

Optionally, the MEMS scanning mirror further includes a second sensing beam, one end of the second sensing beam is connected to the support, the other end of the second sensing beam is connected to the other side of the mirror, and a second angle sensor for sensing a deflection angle of the mirror rotating around the first rotation axis is disposed on the second sensing beam.

Optionally, the second sense beam is disposed to surround a side of the second piezoelectric actuator.

Optionally, the first angle sensor is disposed at a position near an end of the first sensing beam.

Optionally, the first angle sensor is disposed at a position close to one end of the first sensing beam connection support.

Optionally, the first and second piezoelectric actuators are first and second external piezoelectric actuators, respectively.

A second aspect of the invention provides a laser projector comprising a MEMS scanning mirror as provided in the first aspect of the invention.

The invention has the following beneficial effects:

the technical scheme of the invention can avoid the obstruction to the rotation of the reflector, improve the precision of the deflection angle detection of the reflector, is favorable for realizing the miniaturization of the MEMS scanning mirror, is particularly suitable for the MEMS scanning mirror adopting the bent cantilever, is favorable for realizing stable driving, and is suitable for realizing large-angle scanning at low-frequency driving frequency.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings;

FIG. 1 shows a schematic structure diagram of a prior two-dimensional MEMS scanning mirror.

FIG. 2 shows a schematic diagram of a sense beam used to position an angle sensor employed by a prior two-dimensional MEMS scanning mirror.

FIG. 3 illustrates a schematic diagram of a sense beam in a MEMS scanning mirror provided by embodiments of the present invention in a specific example.

Fig. 4 shows a schematic view of the connection of the first sensing beam to the fixed support in the specific example shown in fig. 3.

Fig. 5 shows a schematic view of the connection of the first sensing beam to the movable support in the specific example shown in fig. 3.

Detailed Description

In order to more clearly illustrate the present invention, the present invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

One embodiment of the invention provides a MEMS scanning mirror, which includes a support, a mirror, and a first piezoelectric actuator and a second piezoelectric actuator used as cantilevers, respectively, where the first piezoelectric actuator and the second piezoelectric actuator are used to rotate the mirror around a first rotation axis, the MEMS scanning mirror further includes a first sensing beam, one end of the first sensing beam is connected to the support, and the other end of the first sensing beam is connected to one side of the mirror, and the first sensing beam is provided with a first angle sensor used to sense a deflection angle of the mirror rotating around the first rotation axis.

The MEMS scanning mirror provided by the embodiment can avoid the interference on the rotation of the reflecting mirror, improves the precision of the detection of the deflection angle of the reflecting mirror, is favorable for realizing the miniaturization of the MEMS scanning mirror, is particularly suitable for the MEMS scanning mirror adopting a bent cantilever, is favorable for realizing stable driving, and is suitable for realizing large-angle scanning with low-frequency driving frequency.

In some optional implementations of this embodiment, one end of the first sensing beam connected to the supporting member and the other end connected to the mirror are respectively located on the first rotating shaft. The realization mode can further ensure to avoid the interference on the rotation of the reflector and further improve the precision of the deflection angle detection of the reflector.

In some optional implementations of this embodiment, the first angle sensor is disposed proximate to an end of the first sense beam. Further, the first angle sensor is disposed at a position close to one end of the first sensing beam connected to the support. The realization mode can further ensure to avoid the interference on the rotation of the reflector and can further ensure the precision of the deflection angle detection of the reflector. It will be appreciated that the first sense beam may transmit a rotational torque of the mirror about the first rotational axis to the first angle sensor.

In some alternative implementations of this embodiment, the first piezoelectric actuator and the second piezoelectric actuator each form a curved cantilever.

In some optional implementations of this embodiment, the first sense beam is disposed around a side of the first piezoelectric actuator. The implementation mode is convenient for preparing the first sensing beam and can ensure the miniaturization of the whole MEMS scanning mirror.

In some optional implementations of this embodiment, the MEMS scanning mirror further includes a second sensing beam, one end of the second sensing beam is connected to the support, the other end of the second sensing beam is connected to the other side of the mirror, and a second angle sensor for sensing a deflection angle of the mirror rotating around the first rotation axis is disposed on the second sensing beam.

In some optional implementations of this embodiment, one end of the second sensing beam connected to the supporting member and the other end connected to the mirror are respectively located on the first rotating shaft. The realization mode can further ensure to avoid the interference on the rotation of the reflector and further improve the precision of the deflection angle detection of the reflector.

In some optional implementations of this embodiment, the second angle sensor is disposed proximate to an end of the second sense beam. Further, the second angle sensor is disposed at a position close to one end of the second sensing beam connecting support. The realization mode can further ensure to avoid the interference on the rotation of the reflector and can further ensure the precision of the deflection angle detection of the reflector.

In some optional implementations of this embodiment, the second sense beam is disposed around a side of the second piezoelectric actuator. The implementation mode is convenient for preparing the second sensing beam and can ensure the miniaturization of the whole MEMS scanning mirror.

In some alternative implementations of the present embodiment, the first angle sensor and the second angle sensor are each an angle sensor based on a piezoelectric effect or a piezoresistive effect.

In some optional implementations of this embodiment, the first piezoelectric actuator and the second piezoelectric actuator are a first external piezoelectric actuator and a second external piezoelectric actuator, respectively, that is, the first piezoelectric actuator and the second piezoelectric actuator are used in cooperation for slow scanning of the two-dimensional MEMS mirror. It is understood that, in the case where the first and second piezoelectric actuators are first and second external piezoelectric actuators, respectively, one end of the first sensing beam connected to the support member and the other end connected to one side of the mirror is understood as one end of the first sensing beam connected to the fixed support member and the other end connected to one side of the movable support member. In addition, the first piezoelectric actuator and the second piezoelectric actuator may also be a first internal piezoelectric actuator and a second internal piezoelectric actuator, respectively, and in this case, one end of the first sensing beam connected to the support and the other end connected to the side of the mirror should be understood as one end of the first sensing beam connected to the movable support and the other end connected to the side of the mirror. Certainly, the detection of the deflection angles of the rotation of the mirror around the X axis and the Y axis can also be implemented by using the structure of the MEMS scanning mirror provided in this embodiment, and further, the detection of the deflection angles of the rotation of the mirror around the X axis and the Y axis can be provided with two sensing beams in this embodiment, in this case, the structure of the MEMS scanning mirror provided in this embodiment can be described as follows: the MEMS scanning mirror comprises a fixed support, a movable support, a reflecting mirror, a first internal piezoelectric actuator, a second internal piezoelectric actuator, a first external piezoelectric actuator and a second external piezoelectric actuator, wherein the first internal piezoelectric actuator, the second internal piezoelectric actuator and the second internal piezoelectric actuator are respectively used as cantilevers and are used for enabling the reflecting mirror to rotate around a first rotating shaft (X axis), the first external piezoelectric actuator and the second external piezoelectric actuator are used for enabling the reflecting mirror to rotate around a second rotating shaft (Y axis) through the movable support, the MEMS scanning mirror further comprises a first sensing beam, a second sensing beam, a third sensing beam and a fourth sensing beam, one end of the first sensing beam is connected with the movable support, the other end of the second sensing beam is connected with the other side of the reflecting mirror, one end of the third sensing beam is connected with the fixed support, the other end of the fourth sensing beam is connected with the other side of the movable support, a deflection angle sensor for sensing the angle of the reflecting mirror rotating around the first rotating shaft and a deflection angle sensor for sensing the angle of the fourth sensing angle of the reflecting mirror around the rotating shaft, and angle sensor for sensing angle of the fourth angle sensor around the rotating angle sensor for the second angle sensor.

The above implementation defines that the first piezoelectric actuator and the second piezoelectric actuator are respectively a first external piezoelectric actuator and a second external piezoelectric actuator, that is, the MEMS scanning mirror is a two-dimensional MEMS scanning mirror, and it can be understood that, for a one-dimensional MEMS scanning mirror, the MEMS scanning mirror structure provided in this embodiment may also be adopted.

In a specific example, in combination with the foregoing implementation manner, the two-dimensional MEMS scanning mirror is further described with the MEMS scanning mirror provided in this embodiment: on the basis of the conventional two-dimensional MEMS scanning mirror shown in fig. 1, as shown in fig. 3 to 5, in the two-dimensional MEMS scanning mirror of this example, a first sensing beam 26 is provided around a side of a first external piezoelectric actuator 25a forming a bent shaped cantilever, and a second sensing beam 27 is provided around a side of a second external piezoelectric actuator 25b forming a bent shaped cantilever. The first sensing beam 26 is connected to the fixed support 24 at one end, and the other end of the first sensing beam 26 is connected to one side of the movable support 21, and the one end of the fixed support 24 and the other end of the movable support 21 are connected to the first sensing beam 26, and the other end of the first sensing beam 26 is connected to the other end of the movable support 21, and are respectively located on the Y axis, as shown in fig. 4, the first angle sensor 30 for sensing the deflection angle of the mirror rotating around the Y axis is disposed on the first sensing beam 26 and is located near the end of the first sensing beam 26 connected to the fixed support 24.

In this example, the mirror is made of a single crystal silicon supporting layer serving as a vibration plate, a metal layer serving as a reflector, and a hard mask layer. The movable support 21 is composed of a single crystal silicon active layer and a silicon dioxide layer. The first external piezoelectric actuator 25a and the second external piezoelectric actuator 25b forming a bending cantilever are respectively constituted by a vibration plate, a lower electrode, a piezoelectric body (PZT), and an upper electrode. The fixed support 24 is composed of a single crystal silicon layer, an intermediate silicon layer, a single crystal silicon active layer, a silicon dioxide layer, and a hard mask layer.

Another embodiment of the present invention provides a laser projector, which includes the MEMS scanning mirror provided in the above embodiments, and further includes a laser light source, optical devices such as collimation shaping, a laser driving circuit, a MEMS scanning mirror driving circuit, and the like.

In the description of the present invention, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

It is further noted that, in the description of the present invention, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations and modifications can be made on the basis of the above description, and all embodiments cannot be exhaustive, and all obvious variations and modifications belonging to the technical scheme of the present invention are within the protection scope of the present invention.

Claims

1. A MEMS scanning mirror comprises a support, a reflecting mirror, a first piezoelectric actuator and a second piezoelectric actuator, wherein the first piezoelectric actuator and the second piezoelectric actuator are respectively used as a cantilever and used for enabling the reflecting mirror to rotate around a first rotating shaft;

one end of the first sensing beam connected with the supporting piece and the other end of the first sensing beam connected with the reflecting mirror are respectively positioned on the first rotating shaft;

the first sense beam is disposed to surround one side of the first piezoelectric actuator;

the first piezoelectric actuator and the second piezoelectric actuator form a bending cantilever respectively.

2. The MEMS scanning mirror according to claim 1, further comprising a second sensing beam having one end connected to the support and the other end connected to the other side of the mirror, wherein a second angle sensor is disposed on the second sensing beam for sensing a deflection angle of the mirror rotating about the first rotation axis.

3. The MEMS scanning mirror of claim 2, wherein the second sense beam is disposed around a side of the second piezoelectric actuator.

4. The MEMS scanning mirror of claim 1, wherein the first angle sensor is disposed proximate to an end of the first sense beam.

5. The MEMS scanning mirror of claim 4, wherein the first angle sensor is disposed proximate to an end of the first sense beam connection support.

6. The MEMS scanning mirror of claim 1, wherein the first and second piezoelectric actuators are first and second external piezoelectric actuators, respectively.

7. A laser projector comprising a MEMS scanning mirror as claimed in any one of claims 1 to 6.