Micromechanical device

Limiting elements in micromechanical devices constrain mirror element movement to prevent spring element stress and maintain optical performance by restricting perpendicular motion, addressing the issue of uncontrollable acceleration and shadowing.

DE102017215575B4Active Publication Date: 2026-06-03ROBERT BOSCH GMBH
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Patent Information

Authority / Receiving Office
DE · DE
Patent Type
Patents
Current Assignee / Owner
ROBERT BOSCH GMBH
Filing Date
2017-09-05
Publication Date
2026-06-03

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Abstract

Micromechanical device (10) with a housing (12) and a deflectable mirror element (14) arranged in the housing (12) and connected to the housing by at least one spring element (24a, 24b), wherein the housing (12) has at least one opening (16) adjacent to a reflective surface (14a) of the mirror element (14), through which a light beam (15) can be directed onto the mirror element (14), wherein the housing (12) has at least one limiting element (18; 20a, 20b) in the region of the opening (16), which is configured to limit a movement of the mirror element (14) directed at least partially perpendicular to the opening (16), characterized in that the at least one limiting element (18;20a, 20b) extends continuously from a first wall surface (16a) of the opening (16) to a second wall surface (16b) of the opening (16) arranged opposite the first wall surface (16a) and wherein the at least one limiting element (18; 20a, 20b) is arranged in the region of a rotation axis (R) of the deflectable mirror element (14).
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Description

[0001] The invention relates to a micromechanical device. State of the art

[0002] Micromechanical devices, in particular so-called microelectromechanical structures (MEMS) intended for optical applications, conventionally comprise a housing and a deflectable mirror element arranged in the housing, wherein the housing has an opening adjacent to a reflective surface of the mirror element, through which a light beam can be directed onto the mirror element.

[0003] The aforementioned mirror element is usually attached to the housing by a plurality of spring elements and is rotatably mounted about a defined axis of rotation.

[0004] A mechanical shock to the housing can cause the mirror element to accelerate, thereby placing excessive stress on the spring elements connected to the mirror element.

[0005] DE 10 2015 224 812 A1 discloses a micromechanical device with a stationary element and a deflectable element. Furthermore, a light source is arranged on the deflectable element.

[0006] Documents US 2011 / 0 188 104 A1, DE 10 2016 200 599 A1, US 6 617 098 B, US 2015 / 0 355 458 A1 and DE 10 2012 212 503 A1 describe micromechanical devices that at least partially exhibit features of the preamble of the micromechanical device according to claim 1. Disclosure of the invention

[0007] The present invention provides a micromechanical device with a housing and a deflectable mirror element arranged in the housing and connected to the housing by at least one spring element, wherein the housing has at least one opening adjacent to a reflective surface of the mirror element, through which a light beam can be directed onto the mirror element, wherein the housing has at least one limiting element in the area of ​​the opening, which is designed to limit a movement of the mirror element directed at least partially perpendicular to the opening.

[0008] One aspect of the present invention is to prevent the mirror element from being accelerated uncontrollably, for example, by a vibration of the micromechanical device, by providing a limiting element. By providing at least one limiting element, it can advantageously be achieved that, when the micromechanical device is vibrated, the mirror element is only partially movable perpendicular to the opening of the housing to such an extent that the spring elements connecting the mirror element to the housing are not subjected to such stress that the spring elements are damaged or the geometry of the deflectable mirror element is altered, since the mirror element has a relatively high weight in relation to the spring elements.

[0009] Advantageous embodiments and further developments are described in the dependent claims and in the description with reference to the figures.

[0010] According to the invention, the at least one limiting element extends continuously from a first wall surface of the opening to a second wall surface of the opening arranged opposite the first wall surface, and the at least one limiting element is arranged in the region of a rotation axis of the deflectable mirror element. Because the at least one limiting element extends from wall surface to wall surface in the opening and is arranged essentially in a central region of the mirror element, a movement of the mirror element caused by acceleration of the mirror element, at least partially perpendicular to the opening, can be effectively limited by the limiting element.

[0011] According to a further preferred embodiment, the housing has a first limiting element and a second limiting element in the area of ​​the opening, wherein the first limiting element extends from a first wall surface of the opening towards a second wall surface of the opening, and wherein the second limiting element extends from a second wall surface of the opening towards the first wall surface of the opening. By providing the first limiting element and the second limiting element, it is advantageously possible to position them relative to the mirror element in such a way as to achieve a limiting effect at least equivalent to that achieved by providing a limiting element extending continuously from wall surface to wall surface of the opening.

[0012] According to a further preferred embodiment, the first and second limiting elements are arranged in the region of a rotation axis of the deflectable mirror element, with a gap formed between adjacent end sections of the first and second limiting elements. By providing the first and second limiting elements with dimensions such that the gap is formed between their respective end sections, it is advantageously possible to limit the movement of the mirror element caused by a vibration, at least partially perpendicular to the opening, and simultaneously to provide reduced shadow formation by the limiting element on a surface of the mirror element.

[0013] According to a further preferred embodiment, the at least one limiting element is essentially rod-shaped. The rod-shaped design of the at least one limiting element offers the advantage of good strength, depending on the material chosen, as well as minimal shadowing on the surface of the deflectable mirror element.

[0014] According to a further preferred embodiment, the at least one limiting element has a quadrilateral, in particular trapezoidal, cross-section. The trapezoidal cross-section of the limiting element has the advantage that, due to the inclined orientation of the side surfaces of the limiting element, minimal shadow formation by the limiting element on the surface of the deflectable mirror element can be achieved when light is incident obliquely.

[0015] According to a further preferred embodiment, the housing is formed from a substrate, preferably a semiconductor substrate, wherein the opening on both sides of the at least one limiting element is etched into the housing. Thus, the limiting element can advantageously be formed integrally with the housing and therefore exhibits high strength due to the manufacturing process.

[0016] According to a further preferred embodiment, the width of at least one limiting element can be determined based on the diameter of the reflecting surface of the mirror element, a maximum angle of incidence of the light beam, a tolerable distortion of the light beam, and / or the mechanical strength of the at least one limiting element. Thus, the width of the at least one limiting element can advantageously be determined based on the respective systemic and / or structural requirements of the micromechanical device.

[0017] According to a further preferred embodiment, the at least one limiting element is arranged outside the deflection range of the mirror element, wherein the width of the at least one limiting element is between 10 micrometers and 100 micrometers, preferably between 25 micrometers and 75 micrometers, and wherein the diameter of the reflecting surface of the mirror element is between 1 mm and 2 mm, preferably between 1.5 mm and 1.75 mm. The width of the at least one limiting element is therefore so small in relation to the diameter of the reflecting surface of the mirror element that there is no significant impairment of the optical properties of the mirror element due to shadowing caused by the at least one limiting element.

[0018] According to a further preferred embodiment, the total width of a shadow cast by the at least one boundary element on the reflecting surface of the mirror element is formed by a first width of the shadow cast by the at least one boundary element on the reflecting surface of the mirror element and a second width of light reflected by the mirror element that is blocked by the at least one boundary element. The geometry of the at least one boundary element can thus be advantageously selected such that the total width of the shadow cast by the at least one boundary element on the reflecting surface of the mirror element is as small as possible. The geometry of the at least one boundary element can, for example, be designed depending on a deflection range and / or a maximum angle of incidence of the light ray.

[0019] The described configurations and training programs can be combined in any way desired.

[0020] Further possible embodiments, developments and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments that are not explicitly mentioned. Brief description of the drawings

[0021] The accompanying drawings are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention.

[0022] Other embodiments and many of the aforementioned advantages become apparent with reference to the drawings. The elements depicted in the drawings are not necessarily shown to scale.

[0023] They show: Fig. 1 a schematic representation of a micromechanical device according to a first embodiment of the invention; Fig. 2 a cross-sectional view of the micromechanical device according to the first embodiment of the invention; Fig. 2a a top view of a micromechanical device according to the first embodiment of the invention; Fig. 3 a top view of a micromechanical device according to a second embodiment of the invention; Fig. 4 a cross-sectional view of the micromechanical device according to the second embodiment of the invention; and Fig. 5 a cross-sectional view of the micromechanical device according to the second embodiment of the invention.

[0024] In the figures of the drawings, identical reference symbols denote identical or functionally equivalent elements, parts or components, unless otherwise stated.

[0025] Fig. Figure 1 shows a schematic representation of a micromechanical device according to a first embodiment of the invention.

[0026] The micromechanical device 10 comprises a housing 12 and a deflectable mirror element 14 arranged in the housing 12. The housing 12 has an opening 16 adjacent to a reflective surface 14a of the mirror element 14. The opening 16 is designed such that a light beam can be directed through it onto the mirror element 14. A laser or an LED light source, for example, can serve as the light source.

[0027] Furthermore, the housing 12 has a limiting element 18 in the area of ​​the opening. The limiting element 18 is designed to limit a movement of the mirror element 14 that is at least partially perpendicular to the opening 16.

[0028] In the present embodiment, the limiting element 18 extends from a first wall surface 16a of the opening 16 to a second wall surface 16b of the opening 16, which is arranged opposite the first wall surface 16a. The limiting element 18 is further arranged in the region of a rotation axis R of the deflectable mirror element 14. This allows the limiting element to achieve a good limiting effect.

[0029] Furthermore, the boundary element 18 is essentially rod-shaped. Alternatively, the boundary element can, for example, have another suitable shape such as a meander or other complex geometry.

[0030] A width B of the limiting element can be determined depending on a diameter D of the reflecting surface 14a of the mirror element 14, a maximum angle of incidence of the light beam on the reflecting surface 14a of the mirror element 14, a tolerable distortion of the light beam and / or a mechanical strength of the at least one limiting element.

[0031] The limiting element is furthermore arranged outside the deflection range of the mirror element. The width B of the limiting element is between 10 micrometers and 100 micrometers, preferably between 25 micrometers and 75 micrometers. The diameter D of the reflecting surface 14a of the mirror element 14 is between 1 mm and 2 mm, preferably between 1.5 mm and 1.75 mm.

[0032] Fig. Figure 2 shows a cross-sectional view of the micromechanical device according to the first embodiment of the invention.

[0033] In the present embodiment, the limiting element 18 has a trapezoidal cross-section, wherein a bottom surface of the limiting element 18 located adjacent to the deflectable mirror element 14 has a smaller dimension than the opposite top surface of the limiting element, or the top surface facing away from the deflectable mirror element. Thus, the limiting element 18 causes the least possible shadow formation on the reflective surface 14a of the deflectable mirror element 14.

[0034] An incident light ray 15 is reflected by the reflecting surface 14a of the mirror element in a predetermined direction depending on an angle of incidence α.

[0035] A total width B Ga shadow of the limiting element 18 on the reflecting surface 14a of the mirror element 14 is formed by a first width B1 of a shadow of the at least one limiting element 18 on the reflecting surface 14a of the mirror element 14 and a second width B2 of a light reflected by the mirror element 14, which is blocked by the limiting element.

[0036] Fig. Figure 2a shows a top view of a micromechanical device according to the first embodiment of the invention. The housing 12 is formed from a substrate, preferably a semiconductor substrate. The opening 16 of the housing 12 is etched into the housing on both sides of the limiting element 18. The deflectable mirror element 14 is attached to the housing 12 by a first spring element 24a and a second spring element 24b. The spring elements 24a, 24b are preferably arranged at opposite end sections of the deflectable mirror element 14, each in the region of the opening 16 below the limiting element 18. The spring elements 24a, 24b are formed by silicon elements.

[0037] Fig. Figure 3 shows a top view of a micromechanical device according to a second embodiment of the invention.

[0038] The housing 12 has a first limiting element 20a and a second limiting element 20b in the area of ​​the opening 16. The first limiting element 20a extends from a first wall surface 16a of the opening 16 towards a second wall surface 16b of the opening 16. The second limiting element 20b extends from a second wall surface 16b of the opening 16 towards the first wall surface 16a of the opening 16.

[0039] The first limiting element 20a and the second limiting element 20b are arranged in the region of a rotation axis R of the deflectable mirror element 14. A gap 22 is formed between adjacent end sections 20a1, 20b1 of the first limiting element 20a and the second limiting element 20b.

[0040] Alternatively, the first limiting element 20a and / or the second limiting element 20b can be arranged at a different position on the respective wall surfaces 16a, 16b of the opening 16 of the housing 12.

[0041] Fig. Figure 4 shows a cross-sectional view of the micromechanical device according to the second embodiment of the invention. The housing 12 is formed from a substrate, preferably a semiconductor substrate. The opening 16 of the housing 12 is etched into the housing on both sides of the limiting element 18.

[0042] The deflectable mirror element 14 is attached to the housing 12 by a first spring element (not shown) and a second spring element. The spring elements are preferably arranged at opposite end sections of the deflectable mirror element 14. The spring elements are formed by silicon elements.

[0043] Fig. Figure 5 shows a cross-sectional view of the micromechanical device according to the second embodiment of the invention.

[0044] In contrast to the one in Fig. In the embodiment shown in 4, the limiting element 18 is in a position different from the one shown in Fig. The shape of the limiting element 18 differs from the cross-sectional geometry shown in Figure 4. The shape of the limiting element 18 can be determined depending on its single-beam characteristics and / or its mechanical strength. Furthermore, the shape of the limiting element can be influenced or defined by an etching process to form the opening 16 of the housing 12. Although the present invention has been described above with reference to preferred embodiments, it is not limited to these embodiments but can be modified in a variety of ways. In particular, the invention can be altered or modified in many ways without deviating from the core of the invention.

[0045] For example, the shape, dimensions and / or properties of the components of the micromechanical device can be modified.

Claims

[1] Micromechanical device (10) with a housing (12) and a deflectable mirror element (14) arranged in the housing (12) and connected to the housing by at least one spring element (24a, 24b), wherein the housing (12) has at least one opening (16) adjacent to a reflective surface (14a) of the mirror element (14), through which a light beam (15) can be directed onto the mirror element (14), wherein the housing (12) has at least one limiting element (18; 20a, 20b) in the region of the opening (16), which is configured to limit a movement of the mirror element (14) directed at least partially perpendicular to the opening (16), characterized by, that the at least one limiting element (18; 20a, 20b) extends continuously from a first wall surface (16a) of the opening (16) to a second wall surface (16b) of the opening (16) arranged opposite the first wall surface (16a) and wherein the at least one limiting element (18; 20a, 20b) is arranged in the area of ​​a rotation axis (R) of the deflectable mirror element (14). [2] Micromechanical device according to the preceding claim, characterized by , that at least one limiting element (18; 20a, 20b) is essentially rod-shaped. [3] Micromechanical device according to any of the preceding claims, characterized by , that at least one boundary element (18; 20a, 20b) has a square, in particular trapezoidal, cross-section. [4] Micromechanical device according to any of the preceding claims, characterized by, that the housing (12) is formed from a substrate, preferably a semiconductor substrate, wherein the opening (16) is etched into the housing (12) on both sides of the at least one limiting element (18; 20a, 20b). [5] Micromechanical device according to any of the preceding claims, characterized by , that a width (B) of the at least one limiting element (18; 20a, 20b) can be determined as a function of a diameter (D) of the reflecting surface (14a) of the mirror element (14), a maximum angle of incidence (α) of the light beam (15), a tolerable distortion of the light beam and / or a mechanical strength of the at least one limiting element (18; 20a, 20b). [6] Micromechanical device according to any of the preceding claims, characterized by, that the at least one limiting element (18; 20a, 20b) is arranged outside a deflection range of the mirror element (14), wherein a width (B) of the at least one limiting element (18; 20a, 20b) is between 10 micrometers and 100 micrometers, preferably between 25 micrometers and 75 micrometers, and wherein the diameter (D) of the reflecting surface (14a) of the mirror element (14) is between 1 mm and 2 mm, preferably between 1.5 mm and 1.75 mm. [7] Micromechanical device according to any of the preceding claims, characterized by that a total width (B G) of a shadow of the at least one limiting element (18; 20a, 20b) on the reflecting surface (14a) of the mirror element (14) is formed by a first width (B1) of a shadow of the at least one limiting element (18; 20a, 20b) on the reflecting surface (14a) of the mirror element (14) and a second width (B2) of a light reflected by the mirror element (14) that is blocked by the at least one limiting element (18; 20a, 20b).