Microelectromechanical mirror, method for producing a microelectromechanical mirror, method for operating a microelectromechanical mirror, projection apparatus, and use of a microelectromechanical mirror

Abstract

The invention relates to a microelectromechanical mirror (1) comprising: - a mirror element (2); and - at least one tuning element (7), which is designed for adjusting at least one resonant frequency of the mirror element (2). The invention also relates to: a method for producing a microelectromechanical mirror; a method for operating a microelectromechanical mirror; a projection apparatus; and the use of a microelectromechanical mirror.

Description

[0001] Description

[0002] Microelectromechanical mirror, method for producing a microelectromechanical mirror, method for operating a microelectromechanical mirror, projection device and use of a microelectromechanical mirror

[0003] A microelectromechanical mirror, a method for producing a microelectromechanical mirror, a method for operating a microelectromechanical mirror, a projection device and a use of a microelectromechanical mirror are specified.

[0004] Microelectromechanical mirrors are used, for example, in laser projectors for the targeted deflection of a laser beam in order to display static or moving images. For example, laser projectors are used in the automotive sector to project information onto a road surface, in HUD display systems (head-up display) for matrix illumination or for LIDAR applications (light detection and ranging). This requires a particularly high depth of field, which laser projectors can provide. Laser projectors are also used, for example, as hologram projectors, in VR glasses (virtual reality) or AR glasses (augmented reality). Here the deflected laser beam is coupled into a waveguide lens, for example.The direction and not the position of the laser beam determines the position of the image point for the viewer, so that no additional optics are required. Laser projectors that are insensitive to vibrations and can be manufactured cost-effectively are particularly advantageous for mobile applications, for example in the automotive sector or for VR or AR glasses. A laser projector, for example, has a microelectromechanical mirror that can be rotated in two directions and deflects a time-modulated laser beam to create an image in the far field. In particular, the projected image is always in focus for a viewer and one of the viewer's eyes does not have to be accommodated.

[0005] At least one object of certain embodiments is to provide a microelectromechanical mirror whose vibration properties can be adjusted, in particular during operation or at the end of a manufacturing process. At least one further object of certain embodiments is to provide a method for manufacturing such a microelectromechanical mirror. At least one further object of certain embodiments is to provide a method for operating such a microelectromechanical mirror.

[0006] At least one further object of certain embodiments is to specify a projection device having such a microelectromechanical mirror. At least one further object of certain embodiments is to specify a use of such a microelectromechanical mirror.

[0007] These tasks are performed by a microelectromechanical

[0008] Mirror, a method for producing a microelectromechanical mirror, a method for operating a microelectromechanical mirror, a projection device and a use of a microelectromechanical mirror according to the independent patent claims. Advantageous embodiments and developments of the microelectromechanical mirror, the method for producing a microelectromechanical mirror, the method for operating a microelectromechanical mirror, the projection device and the use of a microelectromechanical mirror are specified in the dependent claims and are further evident from the following description and the drawings.

[0009] According to at least one embodiment, the microelectromechanical mirror has a mirror element. The mirror element has, in particular, a main extension plane. For example, the mirror element has a circular, elliptical, oval, square, rectangular or polygonal shape in plan view onto the main extension plane. The mirror element comprises, for example, a substrate with a reflective layer applied thereto. For example, the substrate comprises silicon, diamond, cubic boron nitride (BN), silicon nitride (SiN) or boron, or consists of at least one of these materials. For example, the reflective layer comprises a metal or consists of a

[0010] Metal .

[0011] In particular, the reflective layer is designed for at least partial reflection and / or deflection of electromagnetic radiation in a spectral range between infrared and ultraviolet light. For example, the reflective layer has a reflectance of at least 90%, or of at least 99%, for electromagnetic radiation in the spectral range between infrared and ultraviolet light. The reflective layer extends in particular in a plane which corresponds to the main extension plane of the mirror element or lies parallel to this. Here and in the following, the main extension plane is defined with respect to a rest position of the mirror element.

[0012] The mirror element is, in particular, movably mounted. For example, the mirror element is at least partially rotatable about at least two axes of rotation. For example, the two axes of rotation are perpendicular to one another. For example, during operation of the microelectromechanical mirror, the mirror element performs a torsional oscillation about each of the at least two axes of rotation. The mirror element has, in particular, an associated resonant frequency for each of the torsional oscillations.

[0013] According to at least one further embodiment, the microelectromechanical mirror has at least one tuning element that is designed to adapt at least one resonant frequency of the mirror element. For example, a torsional oscillation of the mirror element about a first axis of rotation has a first resonant frequency. For example, a torsional oscillation of the mirror element about a second axis of rotation has a second resonant frequency. The first resonant frequency and / or the second resonant frequency correspond in particular to resonant frequencies of different oscillation modes of the mirror element. For example, these oscillation modes are resonantly excited during operation. Preferably, the first resonant frequency and the second resonant frequency are different from one another. The tuning element is designed, for example, to adapt or set the first resonant frequency and / or the second resonant frequency.

[0014] For example, the Ab tuning element is configured to adjust a frequency ratio between the first resonant frequency and the second resonant frequency. For example, the first resonant frequency and / or the second resonant frequency can be increased or decreased by up to 1% or up to 10% by the Ab tuning element. By adjusting the frequency ratio, a refresh rate and / or an image resolution of an image generated during operation with the aid of the microelectromechanical mirror can be changed, for example.

[0015] For example, the Ab tuning element can be used to independently adjust the moments of inertia of the mirror element with respect to the respective axes of rotation. Alternatively or additionally, the Ab tuning element can be used to adjust, for example, the stiffness of spring elements, wherein the mirror element is suspended and / or mounted via the spring elements, for example. Thus, the Ab tuning element can be used to adjust at least one resonance frequency and / or a resonance frequency ratio of oscillation modes of the mirror element. For example, the resonance frequencies lie in a range between 0.5 kHz and 100 kHz.

[0016] According to a preferred embodiment, the microelectromechanical mirror comprises:

[0017] - the mirror element, and

[0018] - at least one tuning element which is configured to adapt at least one resonant frequency of the mirror element. The microelectromechanical mirror described here is based on the idea of ​​being able to adapt at least one resonant frequency of an oscillation mode of the mirror element, in particular during operation and / or at the end of a manufacturing process, at least within a certain range. For example, the microelectromechanical mirror is configured for image projection by means of Lissajous scanning. In this case, for example, a laser beam is deflected during operation of the microelectromechanical mirror in such a way that the laser describes a Lissajous figure on a projection surface. By temporal modulation of the laser beam in conjunction with the Lissajous scanning, an image can thus be generated on the projection surface.

[0019] The density as well as the refresh rate of a scanning pattern in the Lissajous scanning method are particularly sensitive with regard to the resonance frequencies of the mirror element. The resonance frequency can, for example, be broken down into a product of the refresh rate and the number of oscillation periods of the scanning pattern. The refresh rate is derived in particular from the largest common factor of the resonance frequencies with respect to two orthogonal axes of rotation. For example, a Lissajous figure with a high refresh rate has a small number of oscillations, which at the same time limits the achievable image resolution and image quality, and vice versa. For example, a frequency pair with the resonance frequencies 27 kHz and 5.5 kHz for the rotational oscillations about the respective axes of rotation results in a refresh rate of approximately 1 kHz, but an approximate image resolution of only 27 x 5.5 pixels.In contrast, a frequency increase of 10 Hz on the slow axis results in a refresh rate of 30 Hz and an image resolution of 900 x 167 pixels.

[0020] Due to the high mechanical quality, the resonances of the oscillation modes of the mirror element have a narrow frequency bandwidth of, for example, a few Hertz. This severely limits the choice of operating frequencies, i.e., resonance frequencies of the mirror element, particularly with a large field of view (FOV). The microelectromechanical mirror described here allows the resonance frequency ratio to be adjusted, whereby the refresh rate and the image resolution can be specifically set without having to restrict the field of view. In addition, the resonance frequency ratio can be readjusted over the operating time of the microelectromechanical mirror, which advantageously increases the service life of the microelectromechanical mirror.

[0021] The resonance frequencies of the mirror element can depend, for example, on a temperature of the microelectromechanical mirror, on an accuracy of a manufacturing process for the microelectromechanical mirror, on a deposition of dust particles on the mirror element, on an ambient medium of the mirror element, on aging effects of the microelectromechanical mirror, on the influence of ambient air pressure, and / or on the assembly of the microelectromechanical mirror. By adjusting at least one resonance frequency of the mirror element by means of the tuning element either at the end of a manufacturing process and / or during operation of the microelectromechanical mirror, optimal image quality can advantageously be achieved with constant maximum deflection angles of the mirror element.

[0022] According to at least one further embodiment, the microelectromechanical mirror has a drive element which surrounds the mirror element and is connected to the mirror element via first spring elements. For example, the mirror element is connected to the drive element via two first spring elements. For example, the drive element is a piezoelectric drive ring. For example, the mirror element is arranged in a center of the drive element. In particular, the drive element completely surrounds the mirror element in its main extension plane when the mirror element is at rest.

[0023] The drive element is particularly designed to deflect the mirror element from its rest position during operation of the microelectromechanical mirror. In this case, the mirror element is preferably rotated relative to the drive element. For example, mechanical stresses are generated in the drive element, which transmit a bending moment and / or a torque to the mirror element via the first spring elements.

[0024] The drive element comprises, for example, a substrate on which a piezoelectric layer is applied at least in places. The substrate comprises, for example, silicon, diamond, cubic boron nitride (BN), silicon nitride (SiN) or boron, or consists of at least one of these materials. The piezoelectric layer is arranged in particular parallel to the main extension plane of the mirror element. The piezoelectric layer is arranged, for example, between a first electrode and a second electrode. The piezoelectric layer can comprise one or more piezoelectric materials. For example, the piezoelectric layer comprises a piezoelectric material, for example lead zirconate titanate (PZT), aluminum nitride (AIN), or bismuth ferrate barium titanate (BFO-BT), or consists of one of these materials.By applying an electrical voltage to the electrodes, the piezoelectric layer generates the mechanical stresses in the drive element. These mechanical stresses are used during operation of the microelectromechanical mirror, for example, to excite vibration modes of the mirror element in order to deflect the mirror element from its rest position.

[0025] According to at least one further embodiment, the microelectromechanical mirror has a frame that surrounds the drive element and is connected to the drive element via second spring elements. For example, the frame is connected to the drive element via two second spring elements. For example, the frame completely encloses the drive element in the main extension plane of the mirror element. The frame comprises, in particular, a substrate that comprises, for example, silicon, diamond, cubic boron nitride (BN), silicon nitride (SiN) or boron, or consists of one of these materials.

[0026] According to at least one further embodiment of the microelectromechanical mirror, at least one of the spring elements is designed as a torsion spring element. For example, the first spring elements and / or the second spring elements are each designed as a torsion spring element. Features of a torsion spring element are specified below. At least one or all of these features of a torsion spring element can apply to at least one or all of the spring elements.

[0027] The torsion spring element particularly comprises a torsion beam or consists of a torsion beam. For example, the torsion spring element comprises a substrate which, for example, comprises silicon, diamond, cubic boron nitride (BN), silicon nitride (SiN) or boron, or consists of one of these materials. The torsion spring element has, for example, an elongated, beam-like shape with an axis of rotation which, in particular, corresponds to a longitudinal direction of the torsion spring element. During operation, for example, a torsional moment acts on the torsion spring element with respect to the axis of rotation, causing the torsion spring element to twist about its axis of rotation. In this case, a restoring torsional moment builds up in the torsion spring element.

[0028] The axes of rotation of the first spring elements are preferably aligned along a common first axis of rotation. In other words, the first spring elements have a common first axis of rotation about which they twist during operation. In particular, the mirror element is rotatable about the first axis of rotation relative to the drive element at least within a first angular range. For example, two first spring elements are arranged on opposite sides of the mirror element.

[0029] The axes of rotation of the second spring elements are preferably aligned along a common second axis of rotation. In other words, the second spring elements have a common second axis of rotation about which they twist during operation. For example, the drive element, and thus also the mirror element, are rotatable relative to the frame about the second axis of rotation at least within a second angular range. For example, two second spring elements are arranged on opposite sides of the drive element.

[0030] The second axis of rotation is arranged, for example, transversely or orthogonally to the first axis of rotation. In the case where the piezoelectric drive ring and the mirror element are connected via a torsion suspension described in detail below, it is alternatively also possible for the first axis of rotation and the second axis of rotation to be identical or parallel to each other.

[0031] For example, the electrodes of the drive element have different, separate control areas. For example, different control areas are assigned to each rotational axis of the mirror element. By applying electrical voltages to the corresponding control areas, for example, torsional vibrations of the mirror element around the respective rotational axis can be excited independently of one another.

[0032] The mirror element, the drive element, the frame, the first spring elements and the second spring elements are, for example, formed as a one-piece component. In other words, the mirror element, the drive element, the frame and the first and second spring elements are monolithically integrated and / or formed from a common substrate. For example, the substrate is monocrystalline. For example, during production of the microelectromechanical mirror, the common substrate is structured such that a structure of the above-mentioned elements is formed in the common substrate.

[0033] According to at least one further embodiment of the microelectromechanical mirror, a torsion suspension is arranged between the drive element and the mirror element, which surrounds the mirror element, wherein the torsion suspension is connected directly to the drive element via the first spring elements and directly to the mirror element via third spring elements. For example, the torsion suspension is connected to the mirror element via two third spring elements. For example, the third spring elements are each designed as a torsion spring element as described above.

[0034] The axes of rotation of the third spring elements are preferably aligned along a common third axis of rotation. In other words, the third spring elements have a common third axis of rotation about which they twist during operation. For example, the mirror element is rotatable about the third axis of rotation relative to the drive element at least within a third angular range. For example, two third spring elements are arranged on opposite sides of the mirror element. In particular, the third axis of rotation is arranged transversely or perpendicularly to the first axis of rotation and the second axis of rotation is arranged, for example, parallel or identically to the first axis of rotation.

[0035] According to at least one further embodiment of the microelectromechanical mirror, the drive element or the torsion suspension has an elongated shape with a long axis and a short axis perpendicular thereto. In particular, the drive element or the torsion suspension has an elliptical shape. For example, a diameter of the drive element or the torsion suspension in the direction of the long axis is at least 5% larger, preferably at least 20% larger, and particularly preferably at least 40% larger, than a diameter in the direction of the short axis.

[0036] For example, the long axis of the drive element is parallel to the first axis of rotation and / or perpendicular to the second axis of rotation. For example, the long axis of the torsion suspension is parallel to the third axis of rotation and / or perpendicular to the first axis of rotation. An oscillation mode in which the mirror element performs a torsional oscillation about the long axis advantageously has a particularly low anharmonicity due to the elongated shape of the drive element or the torsion suspension.

[0037] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises a structuring on a rear side of the mirror element. In particular, the rear side of the mirror element is a side opposite the reflective layer. In other words, the rear side is arranged opposite a front side of the mirror element, wherein the front side is designed to reflect light during the intended operation of the microelectromechanical mirror. For example, the structuring is designed such that a thickness of the substrate of the mirror element is not constant along the main extension plane, while the reflective layer has a planar surface. The thickness here refers in particular to a spatial extent of the substrate in a direction perpendicular to the main extension plane of the mirror element.For example, the structuring has a cross structure that is arranged parallel to the rotation axes of the mirror element.

[0038] For example, the structuring is designed in such a way that the mass distribution of the mirror element differs with respect to the axes of rotation of the mirror element. In particular, by structuring the back side, elements of an inertia tensor of the mirror element can be adjusted independently of one another. The elements of the inertia tensor determine, for example, moments of inertia of the mirror element with respect to different axes of rotation. By adjusting the moment of inertia of the mirror element, its resonance frequency can be tuned, for example. For example, the structuring makes it possible to specifically set the resonance frequencies of the mirror element during the manufacturing process. For example, by arranging the structuring on the back of the mirror element, manufacturing tolerances of the resonance frequencies of the mirror element can be compensated.

[0039] According to at least one further embodiment of the microelectromechanical mirror, the structuring is further configured to mechanically stiffen the mirror element. For example, the structuring reduces or prevents deformation of the surface of the mirror element during its rotational oscillation about at least one of the axes of rotation. This can advantageously reduce or prevent distortion of a projected image due to curvature of the mirror element during operation of the microelectromechanical mirror. According to at least one further embodiment of the microelectromechanical mirror, the structuring is arranged along at least one axis of rotation of the mirror element.By adding or removing material from the mirror element along a rotational axis, for example, the moment of inertia of the mirror element with respect to this rotational axis is not changed or is hardly changed, while the moment of inertia and thus the resonance frequency of the mirror element with respect to an axis orthogonal to it is changed. Thus, the resonance frequencies of the mirror element with respect to different rotational axes can advantageously be adjusted independently of one another.

[0040] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises at least one substrate element, which surrounds the mirror element at least in places and is directly connected to the mirror element via a predetermined breaking point. The predetermined breaking point allows the substrate element or a part of the substrate element to be easily removed after the microelectromechanical mirror has been manufactured, whereby the moment of inertia and thus at least one resonant frequency of the mirror element can be easily tuned. For example, the substrate element has a well-defined mass.

[0041] According to at least one further embodiment of the microelectromechanical mirror, the tuning element is configured to adjust the at least one resonant frequency during normal operation of the microelectromechanical mirror. Thus, a refresh rate and / or an image resolution can advantageously be set or adjusted during operation of the microelectromechanical mirror without having to limit a maximum deflection of the mirror element. In particular, by adjusting the at least one resonant frequency during normal operation, influences of environmental parameters on the resonant frequency, for example, an ambient temperature, as well as aging phenomena, can be compensated.

[0042] According to at least one further embodiment, the microelectromechanical mirror additionally comprises a carrier, wherein the frame is arranged on the carrier. The carrier comprises, for example, a metal or consists of a metal, in particular copper or aluminum.

[0043] According to at least one further embodiment of the microelectromechanical mirror, a thermal expansion coefficient of the carrier and a thermal expansion coefficient of the frame differ from one another. Due to the different thermal expansion coefficients, mechanical stresses can be induced in the structure of the microelectromechanical mirror by changing the temperature of the microelectromechanical mirror. The mechanical stresses change, for example, the restoring forces of the spring elements. Thus, the at least one resonant frequency of the mirror element can be adjusted by changing the temperature.

[0044] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises a heating element and / or a cooling element arranged on the frame or on the carrier. For example, the heating element comprises a temperature-dependent resistor, a heating wire, a heating coil, or a conductor track applied directly to the frame or the carrier, which has an electrical resistance. The cooling element comprises, for example, a Peltier element. The heating element is, for example, a galvanized heating structure in a meander shape. The temperature-dependent resistor is, for example, a PTC resistor (short for "positive thermal coefficient") in thin-film technology with lift-off electrodes. During operation of the heating element and / or the cooling element, the temperature of the microelectromechanical mirror can thus be adjusted.For example, the microelectromechanical mirror also has a temperature sensor.

[0045] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises a piezoelectric tuning element that is configured to change the stiffness of at least one of the spring elements. For example, the piezoelectric tuning element is configured to change the stiffness of at least one of the first spring elements, the second spring elements, and / or the third spring elements. For example, by applying an electrical voltage to the piezoelectric tuning element, a mechanical stress is generated that changes the stiffness of at least one of the spring elements and thus the resonance frequency of the corresponding oscillation mode.

[0046] In particular, the piezoelectric Ab tuning element comprises a piezoelectric layer, which comprises, for example, PZT, AIN, or BFO-BT, or consists of one of these materials, and which is arranged between two electrodes. The piezoelectric Ab tuning element is, in particular, not configured to excite an oscillation mode of the mirror element.

[0047] According to at least one further embodiment of the microelectromechanical mirror, the piezoelectric tuning element is arranged on the frame. For example, a piezoelectrically active surface of the piezoelectric tuning element is arranged perpendicular to the rotational axis of the second spring elements.

[0048] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises an electrode configuration of the drive element, wherein the electrode configuration is configured for mechanically exciting transverse length modes of a piezoelectric layer of the drive element, wherein the transverse length modes are excited for adapting the resonance frequency of the mirror element.

[0049] For example, in the drive element, longitudinal length modes, in particular d33 modes, of the piezoelectric layer are excited to induce torsional vibrations of the mirror element. In longitudinal length modes, a mechanical stress in the piezoelectric layer is in particular parallel to a direction in which the electrical voltage is applied to the piezoelectric layer. In contrast, in transverse length modes, in particular d31 modes, the mechanical stress is perpendicular to the direction in which the electrical voltage is applied to the piezoelectric layer. Transverse length modes can, for example, change the stiffness of the spring elements and thus the resonance frequency of the mirror element.

[0050] For example, the electrode configuration includes comb electrodes or finger-like toothed electrodes.

[0051] According to at least one further embodiment of the microelectromechanical mirror, the tuning element comprises a hermetically sealed housing in which at least the mirror element is arranged, wherein the hermetically sealed housing is configured to adjust the at least one resonant frequency by changing the air pressure within the housing. For example, at least the mirror element, the drive element, and the spring elements are arranged in the hermetically sealed housing. The air pressure can be used, for example, to adjust the air resistance that the mirror element experiences during the torsional vibrations about the rotational axes.

[0052] For example, several of the tuning elements described here can be combined with one another in a microelectromechanical mirror in order to achieve a larger or particularly large change in at least one resonance frequency.

[0053] According to at least one further embodiment of the microelectromechanical mirror, the tuning element is configured to adjust a frequency ratio between a first resonance frequency of a rotational oscillation of the mirror element about a first axis of rotation and a second resonance frequency of a rotational oscillation of the mirror element about a second axis of rotation during normal operation of the microelectromechanical mirror. According to at least one further embodiment of the microelectromechanical mirror, the microelectromechanical mirror is configured to adjust a resonance frequency of a first oscillation mode and / or a second oscillation mode by adjusting an electrical DC voltage component that is applied to first control regions and / or second control regions of the drive element.

[0054] According to at least one further embodiment of the microelectromechanical mirror, the microelectromechanical mirror is designed to set the mirror element into the first oscillation mode by means of a first electrical alternating current signal having a first frequency, which acts on first control regions of the drive element, and to set the mirror element into the second oscillation mode by means of a second electrical alternating current signal having a second frequency, which acts on second control regions of the drive element.

[0055] According to at least one further embodiment of the microelectromechanical mirror, the microelectromechanical mirror is configured to adjust the resonance frequency of the first oscillation mode and / or the second oscillation mode by adjusting a temperature of the microelectromechanical mirror. The mirror element is configured to adjust the temperature by at least partially absorbing laser radiation.

[0056] Furthermore, a method for producing a microelectromechanical mirror is specified. The method for producing a microelectromechanical mirror is particularly adapted for producing the microelectromechanical mirror described here. All features of the microelectromechanical mirror are also disclosed for the method for producing the microelectromechanical mirror, and vice versa.

[0057] According to at least one embodiment of the method for producing a microelectromechanical mirror, a mirror element is formed. For example, the mirror element, a drive element surrounding the mirror element, a frame surrounding the drive element, first spring elements connecting the mirror element to the drive element, and second spring elements connecting the drive element to the frame are formed. For example, structures of the mirror element, the drive element, the frame, and the spring elements are formed by structuring, for example etching, a common substrate. Furthermore, for example, a reflective layer for the mirror element and a piezoelectric layer between two metallic electrode layers for the drive element are applied to the substrate in places.

[0058] According to at least one further embodiment of the method for producing a microelectromechanical mirror, at least one resonance frequency of the mirror element is adjusted by means of at least one tuning element.

[0059] According to a preferred embodiment, the method for producing a microelectromechanical mirror comprises the steps:

[0060] - forming the mirror element, and - adjusting at least one resonance frequency of the

[0061] Mirror element by means of at least one tuning element.

[0062] According to at least one further embodiment of the method for producing a microelectromechanical mirror, the tuning element comprises a structuring on a rear side of the mirror element, and the adjustment of the at least one resonance frequency is carried out by applying or at least partially removing the structuring.

[0063] For example, material from the substrate on the back of the mirror element is removed or ablated by laser cutting, laser ablation, plasma etching, or mechanical hard machining to independently adjust the mirror element's moments of inertia with respect to different axes of rotation. For example, additional material is applied to the back of the mirror element by printing, filling the pattern with conductive adhesive, or a synthetic resin, e.g., filled epoxy resin, to independently adjust the mirror element's moments of inertia with respect to different axes of rotation.

[0064] According to at least one further embodiment of the method for producing a microelectromechanical mirror, the tuning element comprises at least one substrate element which surrounds the mirror element at least in places and is directly connected to the mirror element via a predetermined breaking point, and the adjustment of the at least one resonance frequency is carried out by removing the substrate element. For example, the tuning element comprises a plurality of substrate elements which are arranged at different positions around the mirror element and are directly connected to the

[0065] mirror element are connected.

[0066] According to at least one further embodiment of the method for producing a microelectromechanical mirror, the tuning element comprises an electrode configuration of a drive element, and the adjustment of the resonance frequency of the mirror element is carried out by mechanical excitation of transverse length modes of a piezoelectric layer of the drive element by the electrode configuration.

[0067] According to at least one further embodiment of the method for producing a microelectromechanical mirror, a drive element comprises first control regions and second control regions, and the adaptation of the resonance frequency of a first oscillation mode and / or a second oscillation mode of the mirror element is carried out by setting an electrical DC voltage component which is applied to the first control regions and / or to the second control regions.

[0068] Furthermore, a method for operating a microelectromechanical mirror is specified. The method for operating a microelectromechanical mirror is particularly designed for operating the microelectromechanical mirror described here. All features of the microelectromechanical mirror are also disclosed for the method for operating the microelectromechanical mirror, and vice versa.

[0069] According to at least one embodiment of the method for operating a microelectromechanical mirror, the microelectromechanical mirror has a mirror element and at least one tuning element, wherein

[0070] - the mirror element is set into a first oscillation mode and a second oscillation mode, and

[0071] - the tuning element is configured to adjust a resonance frequency of the first vibration mode and / or a resonance frequency of the second vibration mode.

[0072] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the microelectromechanical mirror further comprises a drive element, wherein

[0073] - the mirror element is set into the first oscillation mode by means of a first electrical alternating current signal with a first frequency, which acts on first control regions of the drive element, and

[0074] - the mirror element is set into the second oscillation mode by means of a second electrical alternating current signal having a second frequency, which acts on second control regions of the drive element.

[0075] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the first oscillation mode comprises a rotation of the mirror element about a first axis of rotation.

[0076] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the second oscillation mode comprises a rotation of the mirror element about a second axis of rotation that is orthogonal or transverse to the first axis of rotation. According to at least one further embodiment of the method for operating a microelectromechanical mirror, the first oscillation mode and the second oscillation mode are resonantly excited. In other words, an oscillation frequency of the mirror about the respective axis of rotation corresponds to a resonance frequency of the associated oscillation mode.

[0077] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the tuning element comprises a heating element and / or a cooling element, and the adjustment of the resonance frequency of the first oscillation mode and / or the second oscillation mode is carried out by setting a temperature of the microelectromechanical mirror. In particular, the microelectromechanical mirror comprises a carrier and a frame with different thermal expansion coefficients. By changing the temperature, mechanical stresses are thus induced in the microelectromechanical mirror, which lead to a change in the resonance frequency of the first and / or second oscillation mode. For example, before the intended operation of the microelectromechanical mirror, a preheating phase takes place in which the resonance frequencies are brought to predetermined target frequencies.

[0078] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the microelectromechanical mirror is additionally dehumidified by adjusting the temperature. For example, the microelectromechanical mirror has a housing with a viewing window. In humid environments, condensate can form on the viewing window, for example. By heating the microelectromechanical mirror, the condensate can be at least partially or completely removed.

[0079] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the microelectromechanical mirror further comprises at least one spring element, the tuning element comprises a piezoelectric tuning element, and the adjustment of the resonance frequency of the first oscillation mode and / or the second oscillation mode is carried out by changing a stiffness of the at least one spring element by applying an electrical voltage to the piezoelectric tuning element. The at least one spring element is, for example, at least one of the first, second, and / or third spring elements described above.

[0080] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the resonant frequency of the first oscillation mode and / or the second oscillation mode is adjusted by setting an electrical DC voltage component that is applied to the first control regions and / or to the second control regions. The DC voltage component generates, for example, a mechanical prestress in the first, second, and / or third spring elements. The mechanical prestress changes, for example, the resonant frequency of the first and / or second oscillation mode.

[0081] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the tuning element comprises a hermetically sealed housing in which at least the mirror element is arranged, and the adjustment of the at least one resonant frequency is achieved by changing the air pressure within the housing. The hermetically sealed housing is, in particular, airtight.

[0082] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the tuning element comprises an electrode configuration of the drive element, wherein the electrode configuration is additionally configured for the mechanical excitation of transverse length modes of a piezoelectric layer of the drive element, and wherein the transverse length modes are excited to adapt at least one of the resonance frequencies of the mirror element. For example, the stiffness of the first, second, and / or third spring elements can be adjusted by means of the transverse length modes.

[0083] According to at least one further embodiment of the method for operating a microelectromechanical mirror, the resonance frequency of the first oscillation mode and / or the second oscillation mode is adjusted by adjusting a temperature of the microelectromechanical mirror, wherein the temperature is adjusted by at least partial absorption of laser radiation by the mirror element. For example, a reflectivity of the mirror element and / or a power of a laser beam directed onto the mirror element is adjusted such that a desired heating power is achieved by partial absorption of the laser radiation.

[0084] According to at least one further embodiment of the method for operating a microelectromechanical mirror, a frequency ratio between a first resonance frequency (ILA) of a rotational oscillation of the mirror element (1) about a first axis of rotation (LA) and a second resonance frequency (fsA) of a rotational oscillation of the mirror element (1) about a second axis of rotation (SA) is set by the tuning element.

[0085] Furthermore, a projection device is specified. The projection device has, in particular, a microelectromechanical mirror described here. All features of the microelectromechanical mirror are also disclosed for the projection device, and vice versa.

[0086] According to at least one embodiment, the projection device has a laser light source and a microelectromechanical mirror described here. For example, the laser light source comprises or consists of a semiconductor laser diode. Instead of the laser light source, the projection device can also have an incoherent light source, for example a light-emitting diode. During operation, the laser light source emits laser light that is generated by stimulated emission. In contrast to incoherent light that is generated by spontaneous emission, laser light has, in particular, a longer coherence length, a smaller spectral bandwidth, and / or a higher degree of polarization. The microelectromechanical mirror is designed, in particular, to deflect or redirect the laser light emitted by the laser light source.

[0087] Furthermore, a use of a microelectromechanical mirror, in particular the microelectromechanical mirror described here, is specified. All features of the microelectromechanical mirror are also disclosed for the use of the microelectromechanical mirror, and vice versa.

[0088] According to at least one embodiment, the microelectromechanical mirror is used for projecting information onto a surface, for head-up displays, for matrix illumination, for LIDAR applications, for hologram projectors, for VR glasses (virtual reality), or for AR glasses (short for augmented reality).

[0089] Further advantageous embodiments and developments of the microelectromechanical mirror, the method for producing a microelectromechanical mirror, the method for operating a microelectromechanical mirror, the projection device and the use of the microelectromechanical mirror emerge from the embodiments described below in conjunction with the figures.

[0090] Figure 1 shows a schematic perspective view of a microelectromechanical mirror according to an embodiment.

[0091] Figure 2 shows a schematic plan view of a microelectromechanical mirror according to a further embodiment.

[0092] Figures 3 to 6 show schematic perspective representations of microelectromechanical mirrors according to further embodiments. Figures 7 and 8 show a schematic cross-sectional view and a schematic perspective representation of a microelectromechanical mirror according to further embodiments.

[0093] Figure 9 shows a schematic representation of resonance frequencies of a microelectromechanical mirror according to an embodiment as a function of temperature.

[0094] Figure 10 shows a schematic plan view of a part of a microelectromechanical mirror according to a further embodiment.

[0095] Figure 11 shows a schematic representation of a projection device according to an embodiment.

[0096] Figures 12A and 12B show resonance frequencies of a mirror element of a microelectromechanical mirror according to an embodiment as a function of air pressure.

[0097] Identical, similar, or functionally identical elements are provided with the same reference symbols in the figures. The figures and the relative sizes of the elements depicted in the figures are not to scale. Rather, individual elements may be exaggeratedly large or small for clarity and / or clarity.

[0098] The microelectromechanical mirror 1 according to the embodiment in Figure 1 comprises a mirror element 2, which is connected to a drive element 3 via two first spring elements 4. The drive element 3 is connected to a frame 5 via two second spring elements 6. The frame 5, the drive element 3, the mirror element 2 and the spring elements 4, 6 are formed in one piece from a common substrate, for example from silicon, in particular by etching the common substrate. Furthermore, a

[0099] Arranged from tuning element 7 in the form of a heating element 14.

[0100] A reflective layer 21, made of metal, for example, is applied to the mirror element 2 and is designed to at least partially reflect light in the visible spectral range. The mirror element 2 has a mirror suspension 22 that is directly connected to the first spring elements 4. The mirror suspension 22 is designed, in particular, to reduce deformation of the surface of the mirror element 2 during operation of the microelectromechanical mirror 1.

[0101] The drive element 3 has an elongated, elliptical ring shape with a short axis SA and a long axis LA perpendicular thereto. The drive element 3 completely surrounds the mirror element 2 in its main extension plane in the rest position. The first spring elements 4 are arranged on opposite sides of the mirror element 2 along the long axis LA, while the second spring elements 6 are arranged on opposite sides of the drive element 3 along the short axis SA. The first spring elements 4 and the second spring elements 6 are designed as torsion spring elements.

[0102] A piezoelectric layer is applied to the substrate of the drive element 3. The piezoelectric layer is made, for example, of PZT, AIN, or BFO-BT and is arranged between two metallic electrode layers. At least one of the electrode layers is segmented and has first control regions 31a, 31b and second control regions 32a, 32b that are electrically insulated from one another.

[0103] By applying an alternating voltage to the first control regions 31a, 31b during operation of the microelectromechanical mirror 1, a temporally periodic mechanical stress is generated in the piezoelectric layer, which resonantly excites a first oscillation mode of the mirror element 2. The first oscillation mode comprises a rotational oscillation of the mirror element 2 about a first rotation axis, which corresponds to the long axis LA.

[0104] By applying an alternating voltage to the second control regions 32a, 32b during operation of the microelectromechanical mirror 1, a temporally periodic mechanical stress is generated in the piezoelectric layer, which resonantly excites a second oscillation mode of the mirror element 2. The second oscillation mode exhibits a rotational oscillation of the mirror element 2 about a second rotation axis, which corresponds to the short axis SA.

[0105] The oscillation frequencies of the rotational vibrations of mirror element 2 about the short axis SA and the long axis LA correspond to the resonance frequencies of the two vibration modes and are different from each other. A laser beam reflected by mirror element 2 during operation thus generates, for example, a Lissajous pattern on a projection surface. The frequency ratio between the two oscillation frequencies is preferably a rational ratio.

[0106] The tuning element 7 is configured to at least partially adapt at least one of the resonant frequencies of the mirror element 2 during operation of the microelectromechanical mirror 1. For this purpose, the frame 5 is arranged on a carrier 13 (not shown), wherein the frame 5 and the carrier 13 have different thermal expansion coefficients. For example, the carrier 13 comprises a metal or consists of a metal.

[0107] The tuning element 7 is a heating element 14 in the form of a conductor track applied to the frame 5. The microelectromechanical mirror 1 is heated by applying an electrical voltage to the heating element 14. Due to the mutually different thermal expansion coefficients of the frame 5 and the carrier 13, mechanical stresses arise in the common substrate when the temperature changes, which, for example, change the stiffness of the first spring elements 4 and / or the second spring elements 6. This also changes at least one resonance frequency of an oscillation mode of the mirror element 2, in which the mirror element 2 executes a torsional oscillation about the long axis LA and / or about the short axis SA (see, for example, Figure 9).By means of the tuning element 7, an image refresh rate and / or an image resolution can be set within a limited range during operation of the microelectromechanical mirror 1, without severely restricting a maximum deflection angle of the mirror element 2 relative to the frame 5. The microelectromechanical mirror 1 according to the embodiment shown in Figure 2, in contrast to the microelectromechanical mirror 1 described in connection with Figure 1, additionally has an elongated, elliptical torsion suspension 8 with a long axis LA and a short axis SA, which is arranged between the mirror suspension 22 and the annular drive element 3. The torsion suspension 8 is connected directly to the drive element 3 via the first spring elements 4 and directly to the mirror suspension 22 of the mirror element 2 via third spring elements 9.The first spring elements 4 and the second spring elements 6 are arranged along the short axis SA, while the third spring elements 9 are arranged along the long axis LA. The first spring elements 4, the second spring elements 6, and the third spring elements 9 are each designed as torsion spring elements. The torsion suspension 9 advantageously reduces anharmonicity of the torsional vibration of the mirror element 2 about the long axis LA during operation.

[0108] The tuning element 7 comprises substrate elements 11, which are connected to the mirror suspension 22 via predetermined breaking points 12. At the end of a manufacturing process for the microelectromechanical mirror 1, the resonance frequencies of the mirror element 2 can thus be adjusted by removing the substrate elements 11 at least in places. This changes, in particular, the moments of inertia of the mirror element 2 and thus the resonance frequency of the first and / or second oscillation mode.

[0109] Figure 3 shows an embodiment of a microelectromechanical mirror 1 in which the

[0110] From tuning element 7 onwards, in comparison to the microelectromechanical mirror 1 described in connection with Figure 2, it has a structuring 10 on a rear side of the mirror element 2. The structuring 10 is produced, for example, by etching, laser ablation or mechanical hard machining of the common substrate, or by printing or applying additional material to the common substrate. The structuring 10 is also designed to mechanically stabilize the mirror element 2 and reduces deformations of the reflective front side of the mirror element 2 during operation of the microelectromechanical mirror 1.

[0111] The structuring 10 comprises a dam-like ring structure arranged at an edge of the mirror element 2, as well as a cross-shaped structuring 10 consisting of two bars arranged along the short axis SA and the long axis LA. The structuring 10 can also have other and / or further elements, for example straight or curved rib-shaped elements, which can be at least one selected from further rings, ellipses, circular or elliptical sections, or straight bars. For example, the straight bars form a lattice structure or other geometric shapes, for example rectangles.

[0112] By adjusting the thickness of the structuring 10 in a direction perpendicular to the main extension plane of the mirror element 2, in particular the mass distribution and the moments of inertia and thus the resonance frequencies of the mirror element 2 can be at least partially adjusted. For example, the resonance frequency of the torsional vibration mode about the long axis LA is 35.321 kHz without structuring 10 and 31.227 kHz with structuring 10. For example, the resonance frequency of the torsional vibration mode about the short axis SA is 18.518 kHz without

[0113] Structuring 10 and 17 , 995 kHz with structuring 10 .

[0114] In the microelectromechanical mirror 1 according to the embodiment in Figure 4, in contrast to the microelectromechanical mirror 1 in Figure 3, the cross-shaped structure 10 has been at least partially removed again along the short axis SA at the end of the manufacturing process, for example by laser ablation. This changes the moment of inertia of the mirror element 2 and thus its resonance frequency with respect to the torsional oscillation about the long axis LA, while the moment of inertia and thus the resonance frequency of the torsional oscillation of the mirror element 2 about the short axis SA remains approximately unchanged. As a result of the partial removal of the structure along the short axis SA, the resonance frequency of the torsional oscillation mode about the long axis LA changes, for example, to 31.407 kHz, and the resonance frequency of the torsional oscillation mode about the short axis SA remains approximately the same at 18.003 kHz.

[0115] In the microelectromechanical mirror 1 according to the embodiment in Figure 5, in contrast to the microelectromechanical mirror 1 in Figure 4, the cross-shaped structure 10 has been at least partially removed again along the long axis LA at the end of the manufacturing process, for example by laser ablation. This allows the resonance frequency of the mirror element 2 to be adjusted with respect to the short axis SA. By partially removing the structure along the long axis LA, the resonance frequency of the torsional vibration mode about the short axis SA changes, for example, to 18.037 kHz, and the resonance frequency of the torsional vibration mode about the long axis LA remains approximately the same at 31.265 kHz.

[0116] In the microelectromechanical mirror 1 according to the embodiment in Figure 6, in contrast to the microelectromechanical mirror 1 in Figure 5, the cross-shaped structure 10 has been at least partially removed again along the long axis LA and along the short axis SA at the end of the manufacturing process, for example by laser ablation. As a result, the resonance frequencies of the mirror element 2 with respect to the short axis SA and with respect to the long axis LA can be adjusted independently of one another. By partially removing the structure along the long axis LA and the short axis SA, the resonance frequencies of the torsional vibration modes about the short axis SA and about the long axis LA change, for example to 18.045 kHz and 31.446 kHz.

[0117] The microelectromechanical mirror 1 according to the embodiment in Figure 7 has, in addition to the microelectromechanical mirror 1 described in connection with Figure 1, a hermetically sealed housing 16 which is formed by the carrier 13, the frame 5 and a glass dome 161. Thus, at the end of the manufacturing process or during operation of the microelectromechanical mirror 1, in particular an air pressure within the housing 16 can be adjusted, whereby in particular an air resistance of the mirror element 2 changes during its torsional vibrations during operation. For example, the air pressure in the housing 16 can be between IO and 10 -7 atm and 2 atm inclusive. This allows the resonance frequencies of the mirror element 2 to be at least partially adjusted. For example, the resonance frequencies change by approximately 0.05% to 0.2%, in particular by approximately 0.1%, for a pressure change of 1 atm.

[0118] In the microelectromechanical mirror 1 according to the embodiment in Figure 8, the hermetically sealed housing 16 is formed by the carrier 13 and the glass dome 161, in contrast to the microelectromechanical mirror 1 described in connection with Figure 7, i.e. the frame 5 is arranged completely within the hermetically sealed housing 16.

[0119] Figure 9 shows a change in the resonance frequencies f LA , f SA the rotational vibrations of the mirror element 2 with respect to the long axis LA and the short axis SA of the microelectromechanical mirror 1 described in connection with Figure 2 as a function of a temperature change AT of the microelectromechanical mirror 1. In particular, the resonance frequency f LA the vibration mode around the long axis LA by approximately 0 , 2 % or 60 Hz with an increase in temperature of 50 K, while the resonance frequency f SAthe vibration mode around the short axis SA is approximately temperature independent.

[0120] Figure 10 shows an embodiment of a microelectromechanical mirror 1 in which the Ab tuning element 7, in comparison to the microelectromechanical mirror 1 described in connection with Figure 1, has a piezoelectric Ab tuning element 15 which is applied to the frame 5. The piezoelectric Ab tuning element 15 comprises a piezoelectric layer made of PZT, AIN or BFO-BT, which is arranged between two metallic electrode layers. The piezoelectric Ab tuning element 15 is arranged perpendicular to the short axis SA adjacent to the second spring elements 6. By applying an electrical voltage to the piezoelectric Ab tuning element 15, mechanical stresses are generated which in particular change the stiffness of the second spring elements 6. As a result, the resonance frequency of the torsional vibration mode of the mirror element 2 about the short axis SA can be adjusted during operation of the microelectromechanical mirror 1.

[0121] Figure 11 shows a schematic representation of a projection device 1000 according to an exemplary embodiment, which has a microelectromechanical mirror 1 according to the previous description. Furthermore, the projection device 1000 has a laser light source 200, which emits laser light 201 during operation.

[0122] For example, the laser light source 200 can be a so-called RGB light source that can emit red, green, and blue laser light. For this purpose, the laser light source 200 can, for example, have three correspondingly modulatable laser diodes or laser diode groups. The laser light beams can, for example, be superimposed in a beam combiner 202, so that a beam of combined laser light 201' can be irradiated onto the microelectromechanical mirror 1 and reflected by it into the desired image area. The laser light source 200 can, for example, be controlled via laser control electronics 206, for example in order to modulate the amplitude of the laser light 201, 201' over time.

[0123] The microelectromechanical mirror 1 can be controlled via mirror control electronics 203, for example to generate the desired Lissajous figure with which the desired image area can be scanned. Furthermore, sensor electronics 204 can be provided to detect the position and / or the frequencies of the mirror element 2 of the microelectromechanical mirror 1, preferably in real time. In addition, image processing electronics 205 can be present, which, for example, controls the entire image display. This can correspond in particular to the conversion of image or film information into control signals for the laser light source 200 and the microelectromechanical mirror 1, including the temporal synchronization between the position of the mirror element 2 and the amplitudes of the laser light 201, 201'.

[0124] Figure 12A shows a resonance frequency f SAan oscillation mode of a mirror element 2 of a microelectromechanical mirror 1 according to the embodiment of Figure 1, in which the mirror element 2 performs a rotational oscillation about the short axis SA. The resonance frequency f SA as a function of an air pressure p . The air pressure p indicates the air pressure of the ambient air in which the mirror element 2 moves . In particular, the resonance frequency f SA by approximately 0.1% when the air pressure p increases by 1 bar.

[0125] Figure 12B shows a resonance frequency f LA an oscillation mode of a mirror element 2 of a microelectromechanical mirror 1 according to the embodiment of Figure 1, in which the mirror element 2 performs a rotational oscillation about the long axis LA. The resonance frequency f LAas a function of an air pressure p . The air pressure p indicates the air pressure of the ambient air in which the mirror element 2 moves . In particular, the resonance frequency f LA by approximately 0.1% when the air pressure p increases by 1 bar.

[0126] The invention is not limited to the embodiments by the description. Rather, the invention encompasses any novel feature and any combination of features, including, in particular, any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments.

[0127] Reference sign

[0128] 1 microelectromechanical mirror

[0129] 2 mirror elements

[0130] 21 reflective layer

[0131] 22 Mirror suspension

[0132] 3 Drive element

[0133] 31a, b first control areas

[0134] 32a, b second control areas

[0135] 4 first spring element

[0136] 5 frames

[0137] 6 second spring element

[0138] 7 From tuning element

[0139] 8 Torsion suspension

[0140] 9 third spring element

[0141] 10 Structuring

[0142] 11 Substrate element

[0143] 12 Predetermined breaking point

[0144] 13 carriers

[0145] 14 Heating element

[0146] 15 piezoelectric tuning element

[0147] 16 hermetically sealed housing

[0148] 161 Glass dome

[0149] 200 laser light source

[0150] 201 , 201 ' Laser light

[0151] 202 beam combiner

[0152] 203 Mirror control electronics

[0153] 204 Sensor electronics

[0154] 205 image processing electronics

[0155] 206 Laser control electronics

[0156] 1000 projection device

[0157] LA long axis

[0158] SA short axis f LA Resonant frequency, long axis f SA Resonant frequency, short axis

[0159] AT temperature change p air pressure

Claims

Patent claims:

1. Microelectromechanical mirror (1) comprising: - a mirror element (2), and - at least one tuning element (7) which is arranged to adapt at least one resonance frequency of the mirror element (2).

2. Microelectromechanical mirror (1) according to the preceding claim, further comprising a drive element (3) which surrounds the mirror element (2) and is connected to the mirror element (2) via first spring elements (4).

3. Microelectromechanical mirror (1) according to the preceding claim, further comprising a frame (5) which surrounds the drive element (3) and is connected to the drive element (3) via second spring elements (6).

4. Microelectromechanical mirror (1) according to one of claims 2 or 3, wherein at least one of the spring elements (4, 6) is designed as a torsion spring element.

5. Microelectromechanical mirror (1) according to one of claims 2 to 4, wherein a torsion suspension (8) is arranged between the drive element (3) and the mirror element (2), which torsion suspension surrounds the mirror element (2), wherein the torsion suspension (8) is connected directly to the drive element (3) via the first spring elements (4) and is connected directly to the mirror element (2) via third spring elements (9).

6. Microelectromechanical mirror (1) according to one of the Claims 2 to 5, wherein the drive element (3) or the Torsion suspension (8) has an elongated shape with a long axis (LA) and a short axis (SA) perpendicular thereto.

7. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the tuning element (7) comprises a structuring (10) on a rear side of the mirror element (2).

8. Microelectromechanical mirror (1) according to the preceding claim, wherein the structuring (1) is further configured to mechanically stiffen the mirror element (2).

9. Microelectromechanical mirror (1) according to one of claims 7 or 8, wherein the structuring (10) is arranged along at least one axis of rotation (LA, SA) of the mirror element (2).

10. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the tuning element (7) comprises at least one substrate element (11) which surrounds the mirror element (2) at least in places and is connected directly to the mirror element (2) via a predetermined breaking point (12).

11. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the tuning element (7) is configured to adapt the at least one resonant frequency during intended operation of the microelectromechanical mirror (1).

12. Microelectromechanical mirror (1) according to claim 3, additionally comprising a carrier (13), wherein - the frame (5) is arranged on the support (13), - a thermal expansion coefficient of the support (13) and a thermal expansion coefficient of the frame (5) are different from each other, and - the tuning element (7) comprises a heating element (14) and / or a cooling element arranged on the frame (5) or on the support (13).

13. Microelectromechanical mirror (1) according to one of claims 2 to 12, wherein the tuning element (7) comprises a piezoelectric tuning element (15) which leads to a change in the stiffness of at least one of the spring elements (4, 6, 9) is set up.

14. Microelectromechanical mirror (1) according to the preceding claim, wherein the piezoelectric tuning element (15) is arranged on a frame (5).

15. Microelectromechanical mirror (1) according to one of claims 2 to 6, wherein - the tuning element (7) comprises an electrode configuration of the drive element (3), and - the electrode configuration is designed for the mechanical excitation of transverse length modes of a piezoelectric layer of the drive element (3), wherein the transverse length modes are excited to adapt the resonance frequency of the mirror element (2).

16. Microelectromechanical mirror (1) according to one of the preceding claims, wherein - the Abst Imme lament (7) comprises a hermetically sealed housing (16) in which at least the mirror element (2) is arranged, and - the hermetically sealed housing (16) is configured to adjust the at least one resonance frequency by changing an air pressure (p) within the housing (16).

17. Microelectromechanical mirror (1) according to one of the preceding claims, wherein - the tuning element (7) is designed to determine a frequency ratio between a first resonance frequency (f LA ) a rotational oscillation of the mirror element (1) about a first axis of rotation (LA) and a second resonance frequency (fsA) of a rotational oscillation of the mirror element (1) about a second axis of rotation (SA).

18. Microelectromechanical mirror (1) according to one of the preceding claims, wherein - the microelectromechanical mirror (1) is designed to set a resonance frequency of a first oscillation mode and / or a second oscillation mode by setting an electrical DC voltage component which is applied to first control regions (31a / 31b) and / or second control regions (32a / 32b) of the drive element (3).

19. Microelectromechanical mirror (1) according to one of claims 2 to 6, wherein - the microelectromechanical mirror (1) is designed to move the mirror element (2) by means of a first electrical alternating current signal with a first frequency, which is based on first Control areas (31a, 31b) of the drive element (3) acts to put into the first oscillation mode, and - to set the mirror element (2) into the second oscillation mode by means of a second electrical alternating current signal with a second frequency, which acts on second control regions (32a, 32b) of the drive element (3).

20. Microelectromechanical mirror (1) according to one of the preceding claims, wherein - the microelectromechanical mirror (1) is designed to adapt the resonance frequency of the first oscillation mode and / or the second oscillation mode by adjusting a temperature of the microelectromechanical mirror (1), wherein - the mirror element (2) is designed to adjust the temperature by at least partially absorbing laser radiation.

21. Method for producing a microelectromechanical mirror (1) comprising the steps: - forming a mirror element (2), and - Adjusting at least one resonance frequency of the mirror element (2) by means of at least one tuning element (7).

22. A method for producing a microelectromechanical mirror (1) according to the preceding claim, wherein - the tuning element (7) comprises a structuring (10) on a back side of the mirror element (2), and - the adjustment of the at least one resonance frequency is carried out by applying or at least partially removing the structuring (10).

23. A method for producing a microelectromechanical mirror (1) according to one of claims 21 or 22, wherein - the tuning element (7) comprises at least one substrate element (11) which surrounds the mirror element (2) at least in places and is directly connected to the mirror element (2) via a predetermined breaking point (12), and - the adjustment of the at least one resonance frequency is carried out by removing the substrate element (11).

24. A method for producing a microelectromechanical mirror (1) according to one of claims 21 to 23, wherein - the tuning element (7) comprises an electrode configuration of a drive element (3), and - the adjustment of the resonance frequency of the mirror element (2) is carried out by a mechanical excitation of transverse length modes of a piezoelectric layer of the drive element (3) by the electrode configuration.

25. A method for producing a microelectromechanical mirror (1) according to one of claims 21 to 24, wherein - a drive element (3) comprises first control areas (31a, 31b) and second control areas (32a, 32b), and - the adaptation of the resonance frequency of a first oscillation mode and / or a second oscillation mode of the mirror element (2) is carried out by setting an electrical DC voltage component which is applied to the first control regions (31a, 31b) and / or to the second control regions (32a, 32b).

26. Method for operating a microelectromechanical Mirror (1) comprising a mirror element (2) and at least one From tuning element (7), wherein - the mirror element (2) is set into a first oscillation mode and a second oscillation mode, and - the tuning element (7) is arranged to adapt a resonance frequency of the first vibration mode and / or a resonance frequency of the second vibration mode.

27. A method for operating a microelectromechanical mirror (1) according to the preceding claim, wherein - the microelectromechanical mirror (1) further comprises a drive element (3), - the mirror element (2) is set into the first oscillation mode by means of a first electrical alternating current signal having a first frequency, which acts on first control regions (31a, 31b) of the drive element (3), and - the mirror element (2) is set into the second oscillation mode by means of a second electrical alternating current signal having a second frequency, which acts on second control regions (32a, 32b) of the drive element (3).

28. A method for operating a microelectromechanical mirror (1) according to one of claims 26 or 27, wherein - the first oscillation mode is a rotation of the mirror element (2) about a first axis of rotation, - the second oscillation mode is a rotation of the mirror element (2) about a second axis of rotation which is orthogonal to the first axis of rotation, and - the first vibration mode and the second vibration mode are resonantly excited.

29. A method for operating a microelectromechanical mirror (1) according to one of claims 26 to 28, wherein - the tuning element (7) comprises a heating element (14) and / or a cooling element, and - the adjustment of the resonance frequency of the first oscillation mode and / or the second oscillation mode is carried out by adjusting a temperature of the microelectromechanical mirror (1).

30. A method for operating a microelectromechanical mirror (1) according to the preceding claim, wherein the microelectromechanical mirror (1) is additionally dehumidified by adjusting the temperature.

31. A method for operating a microelectromechanical mirror (1) according to one of claims 26 to 30, wherein - the microelectromechanical mirror (1) further comprises at least one spring element (4, 6, 9), - the Ab tuning element (7) comprises a piezoelectric Ab tuning element (15), and - adjusting the resonance frequency of the first vibration mode and / or the second vibration mode by changing a stiffness of the at least one spring element (4, 6, 9) by applying an electrical voltage to the piezoelectric tuning element (15).

32. A method for operating a microelectromechanical mirror (1) according to claim 27, wherein the adjustment of the resonance frequency of the first oscillation mode and / or the second oscillation mode is carried out by adjusting an electrical DC voltage component which is applied to the first control regions (31a, 31b) and / or to the second control regions (32a, 32b).

33. Method for operating a microelectromechanical Mirror (1) according to one of claims 26 to 32, wherein - the Abst Imme lament (7) comprises a hermetically sealed housing (16) in which at least the mirror element (2) is arranged, and - the adjustment of the at least one resonance frequency is carried out by changing an air pressure (p) within the housing (16).

34. A method for operating a microelectromechanical mirror (1) according to claim 27, wherein - the tuning element (7) comprises an electrode configuration of the drive element (3), and - the electrode configuration is additionally configured for the mechanical excitation of transverse length modes of a piezoelectric layer of the drive element (3), wherein the transverse length modes are excited for adapting at least one of the resonance frequencies of the mirror element (2).

35. A method for operating a microelectromechanical mirror (1) according to one of claims 26 to 34, wherein the adjustment of the resonance frequency of the first oscillation mode and / or the second oscillation mode is carried out by adjusting a temperature of the microelectromechanical mirror (1) and wherein the temperature is adjusted by at least partial absorption of laser radiation by the mirror element (2).

36. A method for operating a microelectromechanical mirror (1) according to one of claims 26 to 35, wherein- (7) a frequency ratio between a first resonance frequency (f LA ) a rotational oscillation of the mirror element (1) about a first axis of rotation (LA) and a second resonance frequency (f SA ) a rotational oscillation of the mirror element (1) about a second axis of rotation (SA) is adjusted by the tuning element.

37. Projection device (1000) comprising a laser light source (200) and a microelectromechanical mirror (1) according to one of claims 1 to 16.

38. Use of a microelectromechanical mirror (1) according to one of claims 1 to 16 for the projection of information onto a surface, for head-up displays, for matrix illumination, for LIDAR applications, for hologram projectors, for VR glasses, or for AR glasses.

Images