A micromirror structure for reducing dynamic deformation

Abstract

The application discloses a kind of micro mirror structures for reducing dynamic deformation, including mirror surface, torsion beam, outer frame, connecting rod and ring connecting rod, the outer frame is set to the outside of the mirror surface, the outer frame connects the torsion beam;The connecting rod includes I-type connecting rod, II-type connecting rod and III-type connecting rod;The mirror surface is connected with the I-type connecting rod, the III-type connecting rod and the ring connecting rod between the outer frame, the inner end of the I-type connecting rod is connected with the mirror surface, the outer end of the I-type connecting rod is connected with the ring connecting rod, the inner end and outer end of the III-type connecting rod are connected with the mirror surface and the outer frame respectively, the ring connecting rod can be connected with adjacent two I-type connecting rods or adjacent two III-type connecting rods or adjacent I-type connecting rod and III-type connecting rod;Micro mirror structure for reducing dynamic deformation in the application can significantly reduce dynamic deformation when periodic rotation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-opto-electro-mechanical technology, in particular to a micro-mirror structure for reducing dynamic deformation. BACKGROUND

[0002] As a kind of very important device in micro-nano electro-mechanical system, micro-mirror has wide application in AR / VR, laser radar, projection display, 3D structured light and optical communication etc. According to driving mode, micro-mirror is roughly divided into four categories: electro-thermal micro-mirror, electrostatic micro-mirror, electromagnetic micro-mirror and piezoelectric micro-mirror. The performance of micro-mirror depends on mirror size, resonance frequency, mechanical angle, structural strength and dynamic deformation etc., especially dynamic deformation is crucial for high-performance projection display application.

[0003] During the rotation of micro-mirror, periodic inertial load acting on the mirror surface will cause dynamic deformation of the mirror surface. In the presence of dynamic deformation, the main peak intensity of micro-mirror reflected light beam profile is reduced, and the intensity of adjacent peaks becomes negligible. This effectively leads to changes in the spot size of the mirror reflected light beam, which in turn reduces the contrast between distinguishable spots, thereby limiting the use of micro-mirror in high-performance applications. However, in current research, there are very few structures that can reduce the dynamic deformation of micro-mirror, and the effect is very limited. Not only can it not be applied to different sizes of mirror, but it is also difficult to be used in high resonance frequency applications. In addition, many methods greatly increase the complexity of micro-nano processing and manufacturing.

[0004] In summary, in order to expand the use of micro-mirror in high-performance applications, it is an urgent technical problem for those skilled in the art to provide a micro-mirror structure for reducing dynamic deformation. SUMMARY

[0005] The purpose of the present application is to provide a micro-mirror structure for reducing dynamic deformation to solve the problems existing in the prior art, which can reduce the dynamic deformation of micro-mirror structure.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] The present application provides a micro-mirror structure for reducing dynamic deformation, comprising a mirror surface, a torsional beam, an outer frame, a connecting rod and a ring connecting rod, the outer frame is arranged outside the mirror surface, and the outer frame connects the torsional beam; the connecting rod comprises I-type connecting rod, II-type connecting rod and III-type connecting rod;

[0008] The I-shaped connecting rod, the III-shaped connecting rod and the ring connecting rod are arranged between the mirror surface and the outer frame, the inner end of the I-shaped connecting rod is connected with the mirror surface, the outer end of the I-shaped connecting rod is connected with the ring connecting rod, the inner end and the outer end of the III-shaped connecting rod are connected with the mirror surface and the outer frame respectively, and the ring connecting rod can be connected with two adjacent I-shaped connecting rods or two adjacent III-shaped connecting rods or adjacent I-shaped connecting rod and III-shaped connecting rod.

[0009] Alternatively, the I-shaped connecting rod, the II-shaped connecting rod and the ring connecting rod are arranged between the mirror surface and the outer frame, the inner end of the I-shaped connecting rod is connected with the mirror surface, the outer end of the I-shaped connecting rod is connected with the ring connecting rod, the inner end of the II-shaped connecting rod is connected with the ring connecting rod, the outer end of the II-shaped connecting rod is connected with the outer frame, and the ring connecting rod can be connected with two adjacent I-shaped connecting rods or two adjacent II-shaped connecting rods or adjacent I-shaped connecting rod and II-shaped connecting rod.

[0010] Preferably, the ring connecting rod is a circular ring connecting rod or an inverted ring connecting rod or a straight ring connecting rod.

[0011] Preferably, the I-shaped connecting rod and the III-shaped connecting rod are each provided with four, wherein two I-shaped connecting rods are arranged at intervals on the left side of the mirror surface, the other two I-shaped connecting rods are arranged at intervals on the right side of the mirror surface, two III-shaped connecting rods are arranged at intervals on the top of the mirror surface, and the other two III-shaped connecting rods are arranged at intervals on the bottom of the mirror surface.

[0012] Preferably, the ring connecting rod is connected between adjacent I-shaped connecting rods, adjacent III-shaped connecting rods and adjacent I-shaped connecting rod and III-shaped connecting rod.

[0013] Preferably, the ring connecting rod is connected between adjacent I-shaped connecting rods and adjacent III-shaped connecting rods.

[0014] Preferably, the ring connecting rod is a tangent ring connecting rod which can be tangent to the outer circle of the mirror surface.

[0015] Preferably, the I-shaped connecting rod is provided with eight, the II-shaped connecting rod is provided with six, and the eight I-shaped connecting rods are uniformly distributed on the outer periphery of the mirror surface, three II-shaped connecting rods are arranged at intervals on the top of the mirror surface, and the other three II-shaped connecting rods are arranged at intervals on the bottom of the mirror surface.

[0016] Preferably, the I-shaped connecting rods and the II-shaped connecting rods are connected in sequence by the ring connecting rod.

[0017] Preferably, the 2 I-type connecting rods and 3 II-type connecting rods on the top of the mirror surface are arranged alternately along the circumference and connected in sequence by the ring connecting rods, the 2 I-type connecting rods and 3 II-type connecting rods on the bottom of the mirror surface are arranged alternately along the circumference and connected in sequence by the ring connecting rods, and the 2 I-type connecting rods on the left side of the mirror surface and the 2 I-type connecting rods on the right side of the mirror surface are connected by the ring connecting rods.

[0018] Preferably, the mirror surface, the torsional beam, the outer frame, the connecting rods and the ring connecting rods are in the same plane.

[0019] The present application has the following technical effects relative to the prior art:

[0020] The micro-mirror structure for reducing dynamic deformation in the present application can significantly reduce dynamic deformation during periodic rotation. The micro-mirror structure not only realizes decoupling of the mirror surface and the torsional beam structure, but also adds a ring connecting rod displacement limiting structure. In high resonance frequency applications, i.e. high frequency rotation of the micro-mirror, dynamic deformation can still be significantly reduced.

[0021] Further, by reasonably reducing or enlarging the outer frame and the ring connecting rod during molding, the dynamic deformation reduction effect can be achieved for mirror surfaces of different sizes, i.e. the mirror surface size has universality.

[0022] Further, each structure is a planar structure and is in the same plane as the mirror surface structure, without adding extra photoetching layers, thus without increasing the complexity of micro-nano processing and manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort based on these drawings.

[0024] Figure 1 FIG. 1 is a structural schematic diagram of a micro-mirror structure for reducing dynamic deformation in an embodiment of the present application;

[0025] Figure 2 FIG. 2 is a structural schematic diagram of a micro-mirror structure for reducing dynamic deformation in an embodiment of the present application;

[0026] Figure 3 FIG. 3 is a structural schematic diagram of a micro-mirror structure for reducing dynamic deformation in an embodiment of the present application;

[0027] Figure 4 FIG. 4 is a structural schematic diagram of a micro-mirror structure for reducing dynamic deformation in an embodiment of the present application;

[0028] Figure 5 Structure diagram of the micro-mirror structure for reducing dynamic deformation in the fifth embodiment of the present application;

[0029] Figure 6 Structure diagram of the micro-mirror structure for reducing dynamic deformation in the sixth embodiment of the present application;

[0030] Figure 7 Structure diagram of the micro-mirror structure for reducing dynamic deformation in the seventh embodiment of the present application;

[0031] Figure 8 Structure diagram of the micro-mirror structure for reducing dynamic deformation in the eighth embodiment of the present application;

[0032] Figure 9 Diagram of the angle between the I-type connecting rod and the rotating shaft, and the angle between the III-type connecting rod and the orthogonal shaft in the present application;

[0033] Figure 10 Diagram of the angle between the I-type connecting rod and the rotating shaft, and the angle between the II-type connecting rod and the orthogonal shaft in the present application;

[0034] Figure 11 Process flow chart for manufacturing the micro-mirror structure for reducing dynamic deformation in the present application;

[0035] In the figure: 1, mirror surface; 2, torsion beam; 3, outer frame; 4, ring connecting rod; 5, I-type connecting rod; 6, II-type connecting rod; 7, III-type connecting rod; 8, device layer; 9, insulating layer; 10, substrate layer. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0037] The purpose of the present application is to provide a micro-mirror structure for reducing dynamic deformation to solve the problems existing in the prior art.

[0038] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Embodiment one

[0040] The micro-mirror structure for reducing dynamic deformation in the present embodiment is as shown in the figure Figure 1As shown, including mirror 1, torsion beam 2, outer frame 3, connecting rod and ring connecting rod 4, the outer frame 3 is arranged outside the mirror 1, the outer frame 3 connects the torsion beam 2; connecting rod includes I type connecting rod 5 and III type connecting rod 7;

[0041] The I type connecting rod 5, the III type connecting rod 7 and the ring connecting rod 4 are arranged between the mirror 1 and the outer frame 3, the inner end of the I type connecting rod 5 is connected with the mirror 1, the outer end of the I type connecting rod 5 is connected with the ring connecting rod 4, the inner end and the outer end of the III type connecting rod 7 are connected with the mirror 1 and the outer frame 3 respectively, and the ring connecting rod 4 can be connected with two adjacent I type connecting rods 5 or two adjacent III type connecting rods 7 or adjacent I type connecting rod 5 and III type connecting rod 7. The combined structure of the I type connecting rod 5 and the ring connecting rod 4 can limit the vertical displacement of the I type connecting rod 5, thereby limiting the vertical displacement of the mirror 1 at the position of the I type connecting rod 5.

[0042] In this embodiment, the mirror 1 is not directly connected with the torsion beam 2, and the mirror 1 is connected with the outer frame 3 through the connecting rod and the ring connecting rod 4, and rotates together with the outer frame 3 in working, and has a certain mechanical rotation angle, wherein the rotation axis is the central axis of the torsion beam 2 structure; the mirror 1 is a structure of dynamic deformation, and the mirror 1 can significantly reduce the dynamic deformation under the existence of the connecting rod and the ring connecting structure, reduce the main peak intensity of the reflected light beam, and increase the contrast between the distinguishable light spots.

[0043] In this embodiment, the mirror 1, the torsion beam 2, the outer frame 3, the connecting rod and the ring connecting rod 4 can be scaled in proportion when forming, and have universality for different sizes of mirror 1.

[0044] In this embodiment, the mirror 1, the torsion beam 2, the outer frame 3, the connecting rod and the ring connecting rod 4 structure are in the same plane, without additional increase of photoetching layout, without increase of the complexity of micro-nano processing and manufacturing

[0045] In this embodiment, the ring connecting rod 4 is a circular ring connecting rod 4, the center of which coincides with the center of the mirror 1, and the I type connecting rod 5 and the III type connecting rod 7 are provided with four, wherein two I type connecting rods 5 are arranged at intervals on the left side of the mirror 1, and the other two I type connecting rods 5 are arranged at intervals on the right side of the mirror 1, two III type connecting rods 7 are arranged at intervals on the top of the mirror 1, and the other two III type connecting rods 7 are arranged at intervals on the bottom of the mirror 1, and the ring connecting rod 4 is connected between adjacent I type connecting rods 5, between adjacent III type connecting rods 7 and between adjacent I type connecting rod 5 and III type connecting rod 7, that is, the ring connecting rod 4 is a full ring structure connected together to form a circular ring concentric with the mirror 1.

[0046] Embodiment two

[0047] As Figure 2As shown, the difference between this embodiment and the first embodiment is that the ring connecting rod 4 is connected between adjacent I-type connecting rods 5 and adjacent III-type connecting rods 7, that is, the ring connecting rod 4 does not connect the adjacent I-type connecting rods 5 and III-type connecting rods 7, and the ring connecting rod 4 is not a full ring structure.

[0048] Example 3

[0049] like Figure 3 As shown, the difference between this embodiment and the first embodiment is that the ring connecting rod 4 is an inverted ring connecting rod 4, and its center of circle is located outside the mirror surface 1. There are four I-type connecting rods 5 and four III-type connecting rods 7, among which two I-type connecting rods 5 are spaced apart on the left side of the mirror surface 1, and the other two I-type connecting rods 5 are spaced apart on the right side of the mirror surface 1, two III-type connecting rods 7 are spaced apart on the top of the mirror surface 1, and the other two III-type connecting rods 7 are spaced apart on the bottom of the mirror surface 1. The ring connecting rods 4 are connected between adjacent I-type connecting rods 5, between adjacent III-type connecting rods 7, and between adjacent I-type connecting rods 5 and III-type connecting rods 7, that is, the ring connecting rods 4 are a full ring structure, and when connected together, they form a polygon with circular arc edges.

[0050] Example 4

[0051] like Figure 4 As shown, the difference between this embodiment and the third embodiment is that the ring connecting rod 4 is connected between adjacent I-type connecting rods 5 and adjacent III-type connecting rods 7, that is, the ring connecting rod 4 does not connect the adjacent I-type connecting rods 5 and III-type connecting rods 7, and the ring connecting rod 4 is not a full ring structure.

[0052] Example 5

[0053] like Figure 5 As shown, the difference between this embodiment and the first embodiment is that the ring connecting rod 4 is a straight ring connecting rod 4, which is a rectangular rod.

[0054] There are four I-type connecting rods 5 and four III-type connecting rods 7, among which two I-type connecting rods 5 are spaced apart on the left side of the mirror 1, and the other two I-type connecting rods 5 are spaced apart on the right side of the mirror 1, two III-type connecting rods 7 are spaced apart on the top of the mirror 1, and the other two III-type connecting rods 7 are spaced apart on the bottom of the mirror 1; the ring connecting rods 4 are connected between adjacent I-type connecting rods 5, between adjacent III-type connecting rods 7, and between adjacent I-type connecting rods 5 and III-type connecting rods 7, that is, the ring connecting rods 4 are a full ring structure connected together to form a polygon.

[0055] Example 6

[0056] like Figure 6As shown, the difference between this embodiment and the fifth embodiment is that the ring connecting rod 4 is connected between adjacent I-type connecting rods 5 and adjacent III-type connecting rods 7, that is, the ring connecting rod 4 does not connect the adjacent I-type connecting rods 5 and III-type connecting rods 7, and the ring connecting rod 4 is not a full ring structure.

[0057] Example 7

[0058] like Figure 7 As shown, the difference between this embodiment and embodiment 1 is that: the connecting rod includes a type I connecting rod 5 and a type II connecting rod 6, and a type I connecting rod 5, a type II connecting rod 6 and a ring connecting rod 4 are arranged between the mirror surface and the outer frame. The inner end of the type I connecting rod 5 is connected to the mirror surface 1, the outer end of the type I connecting rod 5 is connected to the ring connecting rod 4, the inner end of the type II connecting rod 6 is connected to the ring connecting rod 4, and the outer end of the type II connecting rod 6 is connected to the outer frame 3. The ring connecting rod 4 can connect two adjacent type I connecting rods 5 or two adjacent type II connecting rods 6 or adjacent type I connecting rods 5 and type II connecting rods 6; the ring connecting rod 4 is a cut ring connecting rod 4, which is a rectangular rod and is tangent to the outer circle of the mirror surface 1.

[0059] In this embodiment, eight I-type connecting rods 5 and six II-type connecting rods 6 are provided. The eight I-type connecting rods 5 are evenly distributed around the periphery of the mirror surface 1. Three II-type connecting rods 6 are spaced apart at the top of the mirror surface 1, and another three II-type connecting rods 6 are spaced apart at the bottom of the mirror surface 1. The I-type connecting rods 5 and the II-type connecting rods 6 are sequentially connected by ring connecting rods 4; that is, the ring connecting rods 4 are a full ring structure, which, when connected together, form a polygon.

[0060] Example 8

[0061] like Figure 8 As shown, the difference between this embodiment and embodiment seven is that: the two I-type connecting rods 5 and the three II-type connecting rods 6 located at the top of the mirror 1 are alternately arranged along the circumference and are connected in sequence through the ring-link 4, the two I-type connecting rods 5 and the three II-type connecting rods 6 located at the bottom of the mirror 1 are alternately arranged along the circumference and are connected in sequence through the ring-link 4, and the two I-type connecting rods 5 located on the left side of the mirror 1 and the two I-type connecting rods 5 located on the right side of the mirror 1 are connected through the ring-link 4; that is, the ring-link 4 is not a full-ring structure.

[0062] like Figure 9-10 As shown, in the above embodiments, the I-type connecting rod is only connected to the mirror surface 1 except the ring-link 4 structure, and the I-type connecting rod makes an angle α with the rotation axis; the II-type connecting rod is only connected to the outer frame 3 except the ring-link 4 structure, and only the cut-ring structure has six II-type connecting rods, four of which make an angle β with the orthogonal axis, and two of which are located on the orthogonal axis; the III-type connecting rod is connected to the outer frame 3 and the mirror surface 1 at the same time except the ring-link 4 structure, and the III-type connecting rod makes an angle γ with the orthogonal axis.

[0063] In order to make the micro-mirror structure more reliable and stable, as preferred, the width of the outer frame 3 is between 0.12 and 0.25 times the radius of the mirror surface 1. In order to minimize dynamic deformation, as preferred, the angles a, b and g between the connecting rods and the rotation axes (or orthogonal axes) are between 20 and 25 degrees. As preferred, the micro-mirror structures for reducing dynamic deformation are all made of materials with high Young's modulus and low density in micro-nano processing manufacturing, such as monocrystalline silicon.

[0064] The working principle of the micro-mirror structure for reducing dynamic deformation in the present application is as follows:

[0065] When the micro-mirror works under the action of an applied periodic excitation electrical signal, the mirror surface makes periodic rotational motion around the rotation axis of the torsional beam, producing a certain mechanical rotation angle, and at the same time, the mirror surface is affected by the periodic inertial load and will produce dynamic deformation. After the light beam is reflected by the moving mirror surface, the scanning line is generated, and due to the non-planarity of the mirror surface caused by dynamic deformation, the spot shape of the reflected light beam will change.

[0066] When the mirror surface makes periodic rotational motion around the rotation axis of the torsional beam, the outer frame is connected to the mirror surface through the connecting rod and makes periodic rotational motion together, and at the same time, the outer frame is connected to the torsional beam to drive the torsional beam to make periodic torsional motion and produce a certain torsional angle.

[0067] When the micro-mirror works under the action of an applied periodic excitation electrical signal, the mirror surface and the torsional beam are structurally decoupled through the outer frame and the connecting rod, so that the dynamic deformation of the mirror surface is not affected by the torsion of the torsional beam. When the mirror surface makes periodic rotational motion, the dynamic deformation of the mirror surface is significantly reduced due to the displacement restriction of the ring connecting rod.

[0068] The micro-mirror structure for reducing dynamic deformation in the present application is as shown in Figure 11 The manufacturing process flow is as follows:

[0069] 1) Prepare an SOI wafer including a device layer 8, an insulating layer 9 and a substrate layer 10 from top to bottom, wherein the device layer 8 and the substrate layer 10 are monocrystalline silicon materials, and the insulating layer 9 is silicon oxide;

[0070] 2) After metal sputtering on the top device layer, sputter a metal layer 11 for electrical connection;

[0071] 3) Front etching, etching the monocrystalline silicon material on the top of the insulating layer 9 to etch the mirror surface 1, the outer frame 3, the ring connecting rod 4 and the connecting rod (this process can be scaled according to the requirements of the mirror surface diameter, etc. all the above structures);

[0072] 4) Back etching, etching the single crystal silicon material at the bottom of the insulating layer 10 to provide space for the movable structures such as the mirror 1, the outer frame 3, the ring connecting rod 4 and the connecting rod;

[0073] 5) Structure release, removing the insulating layer 9 at the hollow part between the structures to complete the micro-mirror structure manufacturing process.

[0074] It should be noted that the mirror 1 is a reflective beam structure, which can be designed into any shape according to needs, and the present application is only taken as an example of circular design; the torsion beam 2 is a support structure for the rotational movement of the micro-mirror during operation, which is roughly divided into a straight beam structure and a folded beam structure, and is crucial to the resonant frequency of the micro-mirror, and the present application is taken as an example of the straight beam structure.

[0075] The principles and implementation modes of the present application are described by applying specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A micromirror structure for reducing dynamic deformation, characterized by: The mirror, the torsion beam, the outer frame, the connecting rod and the ring connecting rod, the outer frame is arranged outside the mirror, the outer frame connects the torsion beam; the connecting rod includes I type connecting rod, II type connecting rod and III type connecting rod; The mirror and the outer frame are provided with the I type connecting rod, the III type connecting rod and the ring connecting rod, the inner end of the I type connecting rod is connected with the mirror, the outer end of the I type connecting rod is connected with the ring connecting rod, the inner end and the outer end of the III type connecting rod are connected with the mirror and the outer frame respectively, and the ring connecting rod can be connected with two adjacent I type connecting rods or two adjacent III type connecting rods or adjacent I type connecting rod and III type connecting rod; The ring connecting rod is a circular ring connecting rod or an inverted ring connecting rod or a straight ring connecting rod; The I type connecting rod and the III type connecting rod are each provided with four, wherein two I type connecting rods are arranged at intervals on the left side of the mirror, and the other two I type connecting rods are arranged at intervals on the right side of the mirror, two III type connecting rods are arranged at intervals on the top of the mirror, and the other two III type connecting rods are arranged at intervals on the bottom of the mirror; The ring connecting rod is connected between adjacent I type connecting rods, adjacent III type connecting rods and adjacent I type connecting rod and III type connecting rod; or, the ring connecting rod is connected between adjacent I type connecting rods and adjacent III type connecting rods; Or, the mirror and the outer frame are provided with the I type connecting rod, the II type connecting rod and the ring connecting rod, the inner end of the I type connecting rod is connected with the mirror, the outer end of the I type connecting rod is connected with the ring connecting rod, the inner end of the II type connecting rod is connected with the ring connecting rod, the outer end of the II type connecting rod is connected with the outer frame, and the ring connecting rod can be connected with two adjacent I type connecting rods or two adjacent II type connecting rods or adjacent I type connecting rod and II type connecting rod; The ring connecting rod is a tangent ring connecting rod capable of being tangent to the outer circle of the mirror; The I type connecting rod is provided with eight, the II type connecting rod is provided with six, the eight I type connecting rods are uniformly distributed on the outer periphery of the mirror, three II type connecting rods are arranged at intervals on the top of the mirror, and the other three II type connecting rods are arranged at intervals on the bottom of the mirror; the I type connecting rods and the II type connecting rods are sequentially connected by the ring connecting rod; or, two I type connecting rods and three II type connecting rods on the top of the mirror are alternately arranged along the circumference and sequentially connected by the ring connecting rod, two I type connecting rods and three II type connecting rods on the bottom of the mirror are alternately arranged along the circumference and sequentially connected by the ring connecting rod, and two I type connecting rods on the left side of the mirror and two I type connecting rods on the right side of the mirror are connected by the ring connecting rod.

2. The micromirror structure for reducing dynamic deformation according to claim 1, characterized in that: The mirror, the torsion beam, the outer frame, the connecting rod and the ring connecting rod are in the same plane.

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