Microelectromechanical mirror, method of operating a microelectromechanical mirror, projection device, and method of using a microelectromechanical mirror

Abstract

The present invention relates to a micro-electromechanical mirror, a method for operating a micro-electromechanical mirror, a projection device, and a method for using a micro-electromechanical mirror. A micro-electromechanical mirror (1) is described, Mirror element (2), The system comprises a torsion suspension (3) that surrounds the mirror element (2) and is connected to the mirror element (2) via two first torsion spring elements (41). Furthermore, the operating method of the micro-electromechanical mirror, the projection device, and the method of using the micro-electromechanical mirror are also described.

Description

Technical Field

[0001] A microelectromechanical mirror, a method for operating the microelectromechanical mirror, and a projection device are proposed.

Background Art

[0002] The microelectromechanical mirror is used, for example, in a laser projector that deflects a laser beam as desired to display a still image or a moving image. The laser projector is used, for example, in the automotive field to project information onto a road surface or in a HUD display system (head up display) for matrix illumination or LIDAR applications (light detection and ranging). For this purpose, a high depth of field provided by the laser projector is particularly required. Further, the laser projector is also used as a hologram projector, VR glasses (virtual reality), AR glasses (augmented reality), etc. Here, the deflected laser beam is coupled to, for example, a waveguide eyeglass lens. In this case, since the position of the image point for the observer is determined by the direction of the laser beam rather than its position, no further optical system is required.

[0003] In particular, laser projectors, which are resistant to vibration and have low manufacturing costs, are advantageous in the automotive sector and mobile applications such as VR or AR glasses. For example, a laser projector can rotate in two directions and is equipped with a micro-electromechanical mirror that deflects a time-modulated laser beam, generating an image in the far field. In particular, the projected image is always in focus for the observer, and the observer does not need to adjust their eyes. For example, document JP2008-20701A describes a two-dimensional optical scanner. Document JP6506212B2 describes an optical deflector. Document US10 371 940B2 describes a device for driving the mirror and related operating methods. Document DE10 2021 116 165B3 describes a Lissajous microscanner.

[0004] At least one problem in a particular embodiment is to provide a micro-electromechanical mirror having a particularly compact structure. At least one further problem in a particular embodiment is to provide a method for operating such a micro-electromechanical mirror. At least one further problem in a particular embodiment is to provide a projection device equipped with a micro-electromechanical mirror having a particularly compact structure. [Overview of the Initiative]

[0005] These problems are solved by the micro-electromechanical mirror, the method for operating the micro-electromechanical mirror, and the projection apparatus as defined in the independent claims. Advantageous embodiments and variations of the micro-electromechanical mirror, the method for operating the micro-electromechanical mirror, and the projection apparatus are described in the dependent claims and are also evident from the following description and drawings.

[0006] According to at least one embodiment, a microelectromechanical mirror comprises a mirror element, which in particular has a principal extending surface. For example, when the principal extending surface is viewed from above, the mirror element has a circular, elliptical, square, rectangular, or polygonal shape. The mirror element includes, for example, a substrate to which a reflective layer is applied. For example, the substrate contains or is composed of silicon. Alternatively or additionally, the substrate may contain or be composed of at least one of the following materials: diamond, cubic boron nitride (BN), silicon nitride (SiN), or boron. For example, the reflective layer may contain or be composed of a metal.

[0007] In particular, the reflective layer is configured to reflect and / or deflect electromagnetic beams in the spectral region between infrared and ultraviolet light. The reflective layer extends, in particular, to a plane corresponding to the principal extending plane of the mirror element. Here and below, the principal extending plane is defined in relation to the stationary position of the mirror element.

[0008] According to at least one other embodiment, the micro-electromechanical mirror comprises a torsion suspension, which surrounds the mirror element and is connected to the mirror element via two first torsion spring elements. For example, the mirror element is positioned at the center of the torsion suspension. In particular, the torsion suspension surrounds the mirror element within its principal extending plane when the mirror element is at rest. The torsion suspension includes, for example, a substrate formed annularly within the principal extending plane, with the mirror element positioned at its center. For example, the substrate contains or is composed of silicon. In particular, during the operation of the micro-electromechanical mirror in which the mirror element is in motion, the principal extending plane of the mirror element may rotate relative to the torsion suspension.

[0009] Each first torsion spring element is provided with, or composed of, a torsion beam. For example, a torsion spring element is provided with a base plate, which contains, or is composed of, silicon. Each torsion spring element has, for example, an elongated beam shape, each having a rotation axis corresponding to the longitudinal direction of each torsion spring element. During operation, a torsional moment acts on the torsion spring element, for example, with respect to the rotation axis, causing the torsion spring element to twist around its respective rotation axis. At this time, a restoring torsional moment is generated in particular on the torsion spring element.

[0010] The axes of rotation of the two first torsion spring elements are preferably aligned along a common first axis of rotation. In other words, the two first torsion spring elements have a common first axis of rotation and twist around that axis of rotation during operation. In particular, the Miller element is rotatable with respect to the torsion spring, at least within a first angular range around the first axis of rotation.

[0011] For example, the mirror element, the torsion suspension, and the first torsion spring element share the same base. In other words, the aforementioned elements are integrally molded and / or monolithically integrated.

[0012] According to at least one further embodiment, the micro-electromechanical mirror comprises a piezoelectric drive ring, the piezoelectric drive ring surrounding a torsion suspension and connected to the torsion suspension via two second torsion spring elements. For example, the torsion suspension is located at the center of the drive ring. The drive ring is configured, in particular, to displace the mirror element from a stationary position during the operation of the micro-electromechanical mirror. In this process, the torsion suspension and / or the mirror element is preferably rotated relative to the drive ring. For example, mechanical stress is generated in the drive ring, and this stress is transmitted to the torsion suspension via the second torsion spring elements as a bending moment and / or torque.

[0013] The drive ring comprises, for example, a substrate containing or composed of silicon, wherein a piezoelectric layer is applied (aufgebracht) at least partially to the substrate. The piezoelectric layer is arranged in particular parallel to the main extending surface of the mirror element.

[0014] The piezoelectric layer is positioned, for example, between the first electrode and the second electrode. The piezoelectric layer may contain one or more piezoelectric materials. For example, the piezoelectric layer may have, or be composed of, a piezoelectric material such as lead zirconate titanate (PZT), aluminum nitride (AlN), or bismuth fluoride barium titanate (BFO-BT). By applying a voltage to the electrodes, the piezoelectric layer generates mechanical stress, particularly in the drive ring.

[0015] The second torsion spring element is, in particular, equipped with or composed of a torsion beam. For example, the torsion spring element is equipped with a base plate, which is, for example, silicon or composed of silicon. The torsion spring elements have, for example, elongated beam-like shapes, each having a rotation axis corresponding to the longitudinal direction of each torsion spring element. During operation, a torsional moment acts on the torsion spring element, for example, with respect to the rotation axis, causing the torsion spring element to twist around its respective rotation axis. At this time, a restoring torsional moment is generated in particular on the torsion spring element.

[0016] The axes of rotation of the two second torsion spring elements are preferably aligned along a common second axis of rotation. In other words, the two second torsion spring elements have a common second axis of rotation and twist around that axis of rotation during operation. The torsion suspension, and by extension the mirror element, is rotatable relative to the drive ring within at least a second angular range around the second axis of rotation. The second axis of rotation is, for example, lateral or perpendicular to the first axis of rotation.

[0017] According to a microelectromechanical mirror in at least one further embodiment, the torsion suspension has an elongated shape having a major axis and a minor axis perpendicular thereto. The major and minor axes are, for example, the axes of symmetry of the torsion suspension. In particular, the torsion suspension has a greater spatial extent in the direction of the major axis than in the direction of the minor axis. In other words, the diameter of the torsion suspension in the direction of the major axis is greater than the diameter in the direction of the minor axis. For example, the diameter of the torsion suspension in the direction of the major axis is at least 5%, preferably at least 20%, and particularly preferably at least 40%, greater than the diameter in the direction of the minor axis. The major and minor axes are, for example, on the main extending plane of the mirror element.

[0018] For example, the first axis of rotation coincides with the major axis, and the second axis of rotation coincides with the minor axis. Therefore, during the operation of the micro-electromechanical mirror, the mirror element is at least partially rotatable with respect to the drive ring, particularly with respect to the minor and major axes.

[0019] Due to the elongated shape of the torsion suspension, at least one vibration mode of the mirror element and / or torsion suspension exhibits particularly lower anharmonicity than the corresponding vibration mode of a torsion suspension without an elongated shape. Hereafter, anharmonicity refers specifically to the fact that the resonant frequency of a vibration mode depends on the amplitude of the vibration mode. In other words, the greater the shift in the resonant frequency as the amplitude of the vibration mode increases, the greater the anharmonicity.

[0020] According to a preferred embodiment, the microelectromechanical mirror includes: - Mirror element, - A torsion suspension surrounding the mirror element and connected to the mirror element via two first torsion spring elements.

[0021] According to a further preferred embodiment, the microelectromechanical mirror includes: - Mirror element, - A torsion suspension surrounding the mirror element and connected to the mirror element via two first torsion spring elements. - A piezoelectric drive ring surrounding the torsion suspension and connected to the torsion suspension via two second torsion spring elements. - A torsion suspension with an elongated shape having a long axis and a short axis perpendicular to it.

[0022] The micro-electromechanical mirror described here is based on the idea that two different vibration modes, in which the mirror element rotates around one of two rotation axes, are excited via only a single drive ring. In this way, the micro-electromechanical mirror is particularly compact. Furthermore, the vibration modes in which the mirror element rotates around its long axis have the advantage of being particularly less disharmonious due to the elongated shape of the torsion suspension.

[0023] According to at least one further embodiment of the micro-electromechanical mirror, the first torsion spring element is arranged along its long axis. In particular, the first rotation axis or the torsion axis of the first torsion spring element is aligned along the long axis of the torsion suspension.

[0024] According to at least one further embodiment of the micro-electromechanical mirror, the second torsion spring element is arranged along a minor axis. In particular, the second rotational or torsional axis of the second torsion spring element is aligned along the minor axis of the torsion suspension.

[0025] According to at least one further embodiment of the micro-electromechanical mirror, two first torsion spring elements are arranged on opposing faces, sides, or lateral surfaces of the mirror element. In this way, for example, the mechanical stability of the suspension or support of the mirror element is improved.

[0026] According to at least one further embodiment of the microelectromechanical mirror, the two first torsion spring elements are arranged on opposite faces of the mirror element. Thereby, for example, the mechanical stability of the suspension of the torsion suspension is improved.

[0027] In at least one further embodiment of the microelectromechanical mirror, the torsion suspension has an elliptical ring shape or a flattened elliptical ring shape. For example, the outer periphery of the torsion suspension has an elliptical or flattened elliptical shape. For example, the semi-major axis of the ellipse corresponds to the major axis of the torsion suspension, and the semi-minor axis of the ellipse corresponds to the minor axis of the torsion suspension. For example, the major axis and the minor axis of the torsion suspension correspond to the two symmetry axes of the flattened ellipse.

[0028] In the case of a flattened ellipse, for example, the distance between the periphery of the torsion suspension and the major axis exhibits a local minimum at the minor axis. In this case, the distance from the major axis corresponds particularly to the distance in a direction perpendicular to the major axis. In other words, the periphery of the torsion suspension has a constriction at the minor axis. For example, the periphery of the torsion suspension has the shape of a Cassini curve.

[0029] According to at least one further embodiment of the microelectromechanical mirror, the torsion suspension does not have a piezoelectric drive element and / or the torsion suspension is composed of a substrate. For example, the torsion suspension is a passive element. In particular, the torsion suspension is not designed, by definition (bestimmungsgemaess), to convert electrical energy into kinetic energy. In contrast, the drive ring is an active element and is designed, by definition, to convert electrical energy into kinetic energy.

[0030] For example, a torsion suspension is composed of a substrate. In one embodiment, one or more sensor elements can be applied to the substrate of the torsion suspension, and one or more sensor elements may be piezoelectric elements, and the drive element is not located on the torsion suspension. The sensor elements are designed, for example, to capture the motion state of a mirror element. The sensor elements are not designed, by definition, to displace the mirror element from its stationary position.

[0031] According to at least one further embodiment of the micro-electromechanical mirror, a mirror element and a first torsion spring element are connected to each other via a connecting element. The connecting element is configured, in particular, to mechanically connect the mirror element to the first torsion spring element. In particular, the connecting element is designed so that the principal extending surface of the mirror element does not bend or deform as much as possible when the mirror element vibrates around two rotation axes. In this way, for example, imaging errors (Abbildungsfehler) can be reduced during the operation of the micro-electromechanical mirror. For example, the connecting element reduces the transmission of torsion of the first torsion spring element to the mirror element. The connecting element includes, in particular, a substrate containing or composed of silicon.

[0032] According to at least one further embodiment of the microelectromechanical mirror, the connecting element is formed in an annular shape and connected to the mirror element by two suspension points. In particular, the mirror element is positioned at the center of the connecting element. The connecting element extends, for example, along the principal extending surface of the mirror element.

[0033] According to at least one further embodiment of the micro-electromechanical mirror, two suspension points are arranged on opposing surfaces of the mirror element along the minor axis. In particular, the suspension points are rotated 90° with respect to the first axis of rotation of the first torsion spring element.

[0034] According to at least one further embodiment of the micro-electromechanical mirror, the connecting element comprises two arc-shaped segments that are separated from each other, each segment being connected to one of two first torsion spring elements.

[0035] According to at least one further embodiment of the micro-electromechanical mirror, each arc-shaped segment is connected to the mirror element by two suspension points. The suspension points are located, for example, at each end of the arc-shaped segment. A first torsion spring element is connected to each arc-shaped segment, for example, between the two suspension points.

[0036] According to at least one further embodiment of the microelectromechanical mirror, the drive ring is formed in an annular shape. According to at least one further embodiment of the microelectromechanical mirror, the drive ring is positioned in a stationary position within the principal extending plane of the mirror element. In particular, the torsion suspension and the mirror element are positioned at the center of the drive ring.

[0037] According to at least one further embodiment of the microelectromechanical mirror, the drive ring is connected to a frame via two third torsion spring elements. For example, the frame completely surrounds the drive ring on the main extending surface of the mirror element. The frame, in particular, has a substrate containing or composed of silicon. The third torsion spring elements have a structure similar to or identical to that of the second torsion spring elements, or are designed to be the same as or similar to that of the second torsion spring elements.

[0038] For example, electrical contacts for the external electrical contacts of the micro-electromechanical mirror are arranged on the frame. The electrical contacts are electrically connected to the piezoelectric drive ring, for example, via a conductor pattern. The conductor pattern is arranged particularly on the third torsion spring element. Alternatively or additionally, the piezoelectric drive ring can be electrically connected to the electrical contacts via bonding wires. Because the motion of the drive ring is small, the mechanical load on the bonding wires is particularly small.

[0039] According to at least one further embodiment of the micro-electromechanical mirror, two third torsion spring elements are arranged along the minor axis on opposing surfaces of the drive ring. For example, the second and third torsion spring elements are aligned along the minor axis.

[0040] According to at least one further embodiment of the microelectromechanical mirror, the mirror element, torsion suspension, drive ring, frame, and torsion spring element are formed as a single integrated component (einstueckiges Bauteil). In other words, the mirror element, torsion suspension, drive ring, frame, and torsion spring element are monolithically integrated and / or formed from a common substrate. For example, the substrate is a single crystal. Furthermore, the connecting element between the first torsion spring element and the mirror element can also be formed integrally with the above elements. For example, in the manufacture of the microelectromechanical mirror, the common substrate is structured such that the above elements are formed within the common substrate.

[0041] According to at least one further embodiment of the micro-electromechanical mirror, all elements of an integral component have a common substrate having a certain thickness. Hereinafter, thickness refers to the spatial extent in the direction perpendicular to the main extending surface of the substrate. In this way, the manufacturing process of the micro-electromechanical mirror is simplified in particular. For example, the thickness of the substrate is from 20 μm to 500 μm. Alternatively, the substrate may have regions with different thicknesses. For example, to improve the mechanical stability of the micro-electromechanical mirror, the substrate may have a thicker thickness in the frame region and a thinner thickness in the drive ring region, for example, thus having high flexibility and low inertia. The substrate in the mirror element region has a thicker thickness compared to the drive ring, which can reduce deformation of the mirror element during operation, for example.

[0042] According to at least one further embodiment of the micro-electromechanical mirror, a piezoelectric layer is applied to a drive ring. In particular, the piezoelectric layer is applied at least partially to the main surface of the drive ring, which is positioned parallel to the main extending surface of the mirror element. The piezoelectric layer has, for example, PZT, AlN, or BFO-BT, or is composed of any of these materials. For example, the thickness of the piezoelectric layer is 0.5 μm to 5 μm.

[0043] According to at least one further embodiment of the microelectromechanical mirror, a piezoelectric layer is positioned between a first electrode and a second electrode. The first and second electrodes are provided, in particular, for applying a voltage to the piezoelectric layer. By applying a voltage during operation, mechanical stresses are generated in the drive ring. These mechanical stresses induce, for example, torsional moments and / or bending moments, which are transmitted to the torsion suspension and / or mirror element via a second torsion spring element.

[0044] According to at least one further embodiment of the microelectromechanical mirror, the second electrode comprises a plurality of drive control regions that are separated from each other. For example, the second electrode is segmented. In particular, the drive control regions are electrically drive controllable independently of each other. By applying voltages to different drive control regions, different torsional and / or bending moments can be generated in the drive ring, for example, and in particular, different vibration modes of the torsion suspension and / or mirror element can be excited.

[0045] According to at least one further embodiment of the microelectromechanical mirror, at least one sensor element is positioned on the drive ring and / or frame for determining the frequency of displacement and / or vibration of the mirror element.

[0046] According to at least one further embodiment of the microelectromechanical mirror, the torsion suspension is provided with at least one sensor element for determining the frequency of displacement and / or vibration of the mirror element.

[0047] In particular, during operation, at least one sensor element can determine the orientation of the mirror element relative to the torsion suspension, drive ring, and / or frame. The sensor element generates, for example, a time-dependent electrical signal proportional to the instantaneous displacement angle of the mirror element.

[0048] For example, the electrical signal from the sensor element can be used to control or close-loop control (Regelung) and / or fine-tuning (Feinjustage) the vibration frequency of the mirror element around two rotation axes. In other words, the drive control signal for the drive ring can be adapted depending on the obtained measurement from the sensor element.

[0049] According to at least one further embodiment of the microelectromechanical mirror, at least one sensor element comprises a piezoelectric layer. According to at least one further embodiment of the microelectromechanical mirror, the piezoelectric layer is positioned between two electrodes. The piezoelectric layer is applied, for example, to the surface of a torsion suspension positioned parallel to the main extending plane of the mirror element. Displacement of the mirror element generates, for example, mechanical stress in the torsion suspension. In this way, the piezoelectric layer deforms in particular, generating a voltage. This voltage can be read, for example, as an electrical signal of the sensor element.

[0050] According to at least one further embodiment of the microelectromechanical mirror, the torsion suspension is configured to linearize the vibration modes around the long axis. In other words, the vibration modes around the long axis exhibit lower anharmonicity due to the shape of the torsion suspension. For example, the elongated shape of the torsion suspension linearizes the vibration modes around the long axis. In particular, the vibration modes around the long axis are a combination of the torsional motion of the mirror element, in which the first torsion spring element twists, and the bending motion of the torsion suspension.

[0051] The micro-electromechanical mirror described here is based on the following idea in particular: For example, rotational vibrations around the first and second rotation axes of the mirror element are resonantly excited. In this way, for example, so-called Lissajous scanning is realized, and during the operation of the micro-electromechanical mirror, a laser beam deflected by the mirror element is projected onto the projection surface, creating a Lissajous figure. By temporally modulating the laser beam, for example, still images or moving images can be created on the projection surface. For a given image refresh rate and image resolution, the micro-electromechanical mirror has the following particular requirements:

[0052] - The diameter of the mirror element determines the aperture, which in turn determines the diffraction-limited resolution of each individual pixel; - The maximum deflection angles of the mirror element around the first and second rotation axes, along with the diameter of the mirror element, determine the image resolution, i.e., the number of pixels per direction. For example, a micro-electromechanical mirror should achieve an image resolution of at least 1024 × 768 pixels, preferably at least 720p; - The resonant frequencies of the vibration modes in which the mirror element vibrates around the first and second rotation axes particularly affect the image refresh rate and also influence the image resolution; - The vibration mode should be designed to avoid bending the mirror elements as much as possible during operation, thus keeping the reflective layer as flat as possible and avoiding imaging errors (Abbildungsfehler), pixel blemishes, and / or speckle patterns; - The Miller element should oscillate harmoniously around the first and second rotation axes to ensure a stable frequency ratio between the frequencies of vibration around the two rotation axes; - The resonance of the vibration modes should not have too small a bandwidth so that the vibration frequencies of the first and second rotation axes can be finely tuned during operation; - Micro-electromechanical mirrors should be as compact as possible; - Micro-electromechanical mirrors should be as resistant as possible to shocks during operation; and / or - The micro-electromechanical mirror should consume as little power as possible, for example, a maximum of 200mW, preferably a maximum of 100mW, and particularly preferably a maximum of 50mW.

[0053] The microelectromechanical mirrors described herein satisfy at least one, preferably more, and most preferably all of the above requirements, and for example, have at least one, preferably more, and most preferably all of the following features: - Vibrations around the short axis are particularly pure torsional vibration modes, while vibrations around the long axis are modified "rocking" modes, which, due to the elongated shape of the torsion suspension, combine, for example, the torsional motion of the mirror element with the bending motion of the torsion suspension. In this way, the dissonance of the rocking mode in particular is reduced; - All elements of a microelectromechanical mirror have a common substrate, for example, one of which is of a uniform thickness. In other words, all elements of a microelectromechanical mirror have a substrate of the same thickness. This simplifies the manufacturing process of the microelectromechanical mirror. Alternatively, the substrate may have multiple regions of different thicknesses; - The resonant frequencies of the two vibration modes are clearly different, and are particularly outside the audible frequency range. In this way, the mirror suspension can be optimized in one direction, and for example, the thickness of the substrate can be reduced; - The desired mirror diameter, torsion suspension shape, desired resonant frequency, and required flatness of the mirror element, combined with the substrate material, determine the substrate thickness (bestimmen); - The shape and size of the torsion suspension, and the dimensions of the first torsion spring element, are derived from the desired angular range of rotation around the first rotation axis, the allowable mechanical stress, the desired resonant frequency, and the desired linearity or harmonicity of the vibration modes around the first rotation axis; - The second torsion spring element is positioned within the drive ring for rotation around the second rotation axis and rotated 90° relative to the long axis of the torsion suspension. In this way, the micro-electromechanical mirror has a particularly compact structure. The dimensions of the second torsion spring element are obtained based on the desired angular range of rotation around the second rotation axis, the allowable mechanical stress, and the desired resonant frequency of the vibration mode around the second rotation axis; - The conductive pattern for the electrical contact of the piezoelectric layer of the drive ring can be placed on a third torsion spring element that moves little or no during operation.

[0054] According to at least one embodiment, a microelectromechanical mirror is used for surface projection, head-up displays, matrix lighting, LiDAR applications, hologram projectors, VR glasses, or AR glasses.

[0055] Furthermore, a method for operating the micro-electromechanical mirror is also described. This method is particularly applicable to the operation of the micro-electromechanical mirror described here. All the characteristics of the micro-electromechanical mirror are disclosed in the method for operating the micro-electromechanical mirror, and vice versa.

[0056] According to at least one embodiment of a method for operating a micro-electromechanical mirror, the mirror element is placed into a first vibration mode by a first AC electrical signal of a first frequency acting on a first drive control region of a drive ring.

[0057] According to at least one embodiment of the method, a torsion suspension is placed into a second vibration mode by a second AC electrical signal of a second frequency acting on a second drive control region of the drive ring. In particular, in the second vibration mode, the torsion suspension vibrates together with the mirror element.

[0058] The first and second drive control regions correspond, in particular, to the drive regions of the second electrode provided for electrical contact of the piezoelectric layer of the drive ring.

[0059] According to at least one further embodiment of the method, the first vibration mode includes rotation of the mirror element about its major axis.

[0060] According to at least one further embodiment of the method, the second vibration mode includes rotation around the minor axis of the mirror element. In particular, the torsion suspension in the second vibration mode rotates together with the mirror element around the minor axis.

[0061] According to at least one further embodiment of the method, a first vibration mode and / or a second vibration mode are excited resonantly. In particular, the first and second vibration modes are excited simultaneously and overlap during the operation of the micro-electromechanical mirror. The first frequency corresponds, for example, to the resonant frequency of the first vibration mode, or deviates from the resonant frequency of the first vibration mode by at most the bandwidth of the resonance of the first vibration mode. The second frequency corresponds, for example, to the resonant frequency of the second vibration mode, or deviates from the resonant frequency of the second vibration mode by at most the bandwidth of the resonance of the second vibration mode.

[0062] According to at least one further embodiment of the method, the motion of the drive ring in the first and / or second vibration modes has an amplitude of up to one-fifth, preferably up to one-tenth, of the amplitude of the motion of the mirror element. In other words, the drive ring hardly moves in the first and second vibration modes. For example, the motion of the drive ring is negligible compared to that of the mirror element. This reduces, for example, the damping of vibration modes due to air resistance and / or improves excitation efficiency. For example, through mechanical amplification, a small deflection of the drive ring is converted into a large displacement of the mirror element. Furthermore, the third torsion spring element exhibits little to no twisting in the first and second vibration modes.

[0063] For example, a conductive path wired through a third torsion spring element for the electrical contact of the drive ring electrodes experiences little to no mechanical load due to the small motion of the drive ring. This extends the lifespan of, for example, a micro-electromechanical mirror. The electrodes of the drive ring can also be electrically contacted via bonding wires, either alternatively or additionally.

[0064] According to at least one further embodiment of the method, the resonant frequency of the first vibration mode is at least 1.3 times greater than the resonant frequency of the second vibration mode. The clear difference between the two resonant frequencies allows for the independent optimization of the suspension of the mirror elements for motion around two rotation axes, for example.

[0065] According to at least one further embodiment of the method, the resonant frequency of the second vibration mode is at least 16 kHz, preferably at least 20 kHz. In particular, since the resonant frequencies of the first and second vibration modes are outside the audible range, the micro-electromechanical mirror does not generate, for example, interfering background noise during operation. Furthermore, a higher resonant frequency allows for improved image resolution, for example, in projection applications.

[0066] According to at least one further embodiment of the method, the first and / or second vibration modes operate within a harmonic range. In other words, the first and second vibration modes have little disharmonicity. Therefore, during operation, the frequency ratio between the first and second vibration modes changes little to no. In other words, there is the advantage that the frequency ratio is stable during operation. For example, the change in the frequency ratio between the first and second vibration modes during operation is at most 5%, preferably at most 1%, and particularly preferably at most 0.1%.

[0067] According to at least one further embodiment of the method, the second vibration mode is a torsional vibration in which the Miller element rotates around its minor axis, and the first vibration mode is a combination of a torsional vibration in which the Miller element rotates around its major axis and a bending motion of the torsion suspension. In particular, the first vibration mode is a so-called "rocking" mode in which, for example, one of the two second torsion spring elements moves periodically in a direction perpendicular to the principal extending plane of the Miller element, and the other of the two second torsion spring elements moves, for example, in opposite phase to it. In this way, the Miller element vibrates, in particular, around its major axis.

[0068] Furthermore, a projection device is also described. This projection device includes, in particular, a micro-electromechanical mirror as described here. All the features of the micro-electromechanical mirror are disclosed in the projection device, and vice versa.

[0069] According to at least one embodiment, the projection device includes a laser light source and a micro-electromechanical mirror described herein. The micro-electromechanical mirror, in operation, deflects, for example, the laser light emitted from the laser light source. Due to the vibration modes of the mirror element as described above, the deflected laser light can scan, in particular, an image region perceptible to the observer. In particular, the micro-electromechanical mirror is configured to perform Lissajous scanning of the image region.

[0070] Further advantageous embodiments and improvements of microelectromechanical mirrors, methods of operating microelectromechanical mirrors, and projection devices are evident from the embodiments described below in relation to the drawings. [Brief explanation of the drawing]

[0071] [Figure 1] Figure 1 is a schematic top view showing a micro-electromechanical mirror according to the first embodiment. [Figure 2] Figure 2 is a schematic top view showing a micro-electromechanical mirror according to the second embodiment. [Figure 3A] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3B] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3C] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3D] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3E]Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3F] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3G] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3H] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3I] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 3J] Figures 3A to 3J schematically show the vibration modes of a micro-electromechanical mirror according to the first embodiment. [Figure 4A] Figures 4A and 4B schematically show the second vibration mode of the micro-electromechanical mirror according to the first embodiment. [Figure 4B] Figures 4A and 4B schematically show the second vibration mode of the micro-electromechanical mirror according to the first embodiment. [Figure 5A] Figures 5A and 5B show schematic diagrams of the first vibration mode of the micro-electromechanical mirror according to the first embodiment. [Figure 5B] Figures 5A and 5B show schematic diagrams of the first vibration mode of the micro-electromechanical mirror according to the first embodiment. [Figure 6] Figure 6 schematically shows the displacement and mechanical stress of the mirror element of the micro-electromechanical mirror according to the first embodiment. [Figure 7] Figure 7 schematically shows the displacement (Auslenkung) of the mirror element of the micro-electromechanical mirror according to the first embodiment. [Figure 8A] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8B]Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8C] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8D] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8E] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8F] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8G] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8H] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8I] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 8J] Figures 8A to 8J schematically show the vibration modes of a micro-electromechanical mirror according to the second embodiment. [Figure 9A] Figures 9A and 9B schematically show the second vibration mode of a micro-electromechanical mirror according to the second embodiment. [Figure 9B] Figures 9A and 9B schematically show the second vibration mode of a micro-electromechanical mirror according to the second embodiment. [Figure 10A] Figures 10A and 10B schematically show the first vibration mode of a micro-electromechanical mirror according to the second embodiment. [Figure 10B] Figures 10A and 10B schematically show the first vibration mode of a micro-electromechanical mirror according to the second embodiment. [Figure 11]Figure 11 schematically shows the displacement and mechanical stress of the mirror element of the micro-electromechanical mirror according to the second embodiment. [Figure 12] Figure 12 schematically shows the displacement of the mirror element of the micro-electromechanical mirror according to the second embodiment. [Figure 13] Figure 13 shows a cross-section of a micro-electromechanical mirror according to the second embodiment. [Figure 14] Figure 14 is a schematic diagram showing a projection device according to an embodiment. [Modes for carrying out the invention]

[0072] Elements that are identical, of the same type, or of the same function are given the same reference numeral in the drawings. The size ratios between elements shown in the drawings are not considered to be to actual size. Rather, individual elements may be exaggerated in size, either larger or smaller, for clarity and / or ease of understanding.

[0073] The micro-electromechanical mirror 1 according to the first embodiment shown in Figure 1 comprises a mirror element 2, a connecting element 6, a torsion suspension 3, a drive ring 5, a frame 7, and two first, second, and third torsion spring elements 41, 42, and 43, respectively, which are integrally molded from a common silicon substrate 8. In particular, Figure 1 shows a top view of the main extension surface 21 of the mirror element 2.

[0074] The mirror element 2 is circular or elliptical, having a diameter of, for example, 1 mm to 2 mm. A reflective layer 22 (not shown) is applied to the main surface 21 of the mirror element 2, and the reflective layer 22 comprises a metal, dielectric mirror, or nanostructured surface and is designed to reflect electromagnetic beams in the spectral range between infrared and ultraviolet.

[0075] The connecting element 6 mechanically connects the mirror member 2 to two first torsion spring elements 41, which are positioned on opposing surfaces of the mirror element 2. The connecting element 6 comprises two arc-shaped segments 62, which are mechanically connected to the mirror element 2 via two suspension points 61 at their ends. Each of the two first torsion spring elements 41 is mechanically connected to a segment 61 located midway between the two suspension points 61.

[0076] The two first torsion spring elements 41 are mechanically connected to the torsion suspension 3 via a connecting element 6. The torsion suspension 3 completely encloses the mirror element 2 and the connecting element 6 in its main extending surface 21, so the mirror element 2 is positioned at the center of the torsion suspension 3. The torsion suspension 3 has an elongated shape with a major axis 31 and a minor axis 32, which are the axes of symmetry of the torsion suspension 3, respectively. The diameter of the torsion suspension 3 along the major axis 31 is approximately 50% larger than the diameter of the torsion suspension 3 along the minor axis 32. The outer circumference of the torsion suspension 3 is a compressed or constricted ellipse. The two first torsion spring elements 41 are positioned along the major axis 31.

[0077] The two first torsion spring elements 42 are mechanically connected to the drive ring 5 via the connecting element 3. The two second torsion spring elements 42 are positioned on opposing surfaces of the torsion suspension 3 along the short axis 32.

[0078] The drive ring 5 is circular or elliptical and is mechanically connected to the frame 7 via two third torsion spring elements 43. The torsion suspension 3 is located at the center of the drive ring 5. The frame 7 completely surrounds the drive ring 5 in its main extending surface 21. On the main surface of the drive ring 5, which is arranged parallel to the main extending surface 21, a piezoelectric layer 50 made of PZT (not shown) is located between a first electrode 51 (not shown) and a second electrode 52. The second electrode 52 has first drive control regions 521a, 521b and second drive control regions 522a, 522b, which are separated from each other.

[0079] The first vibration mode 11 of the micro-electromechanical mirror 1 can be excited by applying a time-oscillating voltage between the first electrode 51 and the first drive control regions 521a and 521b of the second electrode 52. The second vibration mode 12 of the micro-electromechanical mirror 1 can be excited by applying a time-oscillating voltage between the first electrode 51 and the second drive control regions 522a and 522b of the second electrode 52. Here, the first vibration mode 11 includes, in particular, rotational vibration of the mirror element 2 around the long axis 31, and the second vibration mode 12 includes, in particular, rotational vibration of the mirror element 2 around the short axis 32. The voltage is applied to the first drive control regions 521a and 521b, in particular in opposite phase. Similarly, the voltage is applied to the second drive control regions 522a and 522b, in particular in opposite phase.

[0080] Sensor elements 9 are positioned on both the drive ring 5 and the frame 7 to determine the frequency of displacement and / or vibration of the mirror element 2 during the operation of the micro-electromechanical mirror 1. The sensor elements 9 include a piezoelectric layer 90 (not shown) positioned between a first electrode 91 (not shown) and a second electrode 92. In particular, the sensor elements 9 capture the mechanical stresses (mechanische Verspannungen) of the micro-electromechanical mirror 2 that occur during the vibration of the mirror element 2 during the operation of the micro-electromechanical mirror 1.

[0081] The micro-electromechanical mirror 1 of the first embodiment has the following features in particular: - Thickness of piezoelectric layer 50 and 90: 1.7 μm; - Thickness of Si substrate 8: 150 μm, short axis 32 is the crystal direction <100> Aligned along the crystal direction, the long axis 31 is the crystal direction <010> Aligned along; - Dimensions of the micro-electromechanical mirror 1 on the main extending surface 21: 7.65 mm × 9.35 mm; - Resonant frequency of the first vibration mode 11: 30.8 kHz; - Resonant frequency of the second vibration mode 12: 20.9 kHz; - Maximum displacement angle of mirror element 2 in the first vibration mode 11: 16.5°; - Maximum displacement angle of mirror element 2 in the second vibration mode 12: 11°; - Q coefficient of the vibration mode: 10³; - Anharmonicity of the first vibration mode 11: frequency shift of 6 Hz at displacement angles from 1° to 16.5°; - Anharmonicity of the second vibration mode 12: Frequency shift of -1.4 Hz at displacement angles from 1° to 11°; - Sensitivity of sensor element 9 to the first vibration mode 11: 0.5 μA / ° to 15.0 μA / °; - Sensitivity of sensor element 9 to second vibration mode 12: 0.2 μA / ° to 1.5 μA / °.

[0082] The micro-electromechanical mirror 1 according to the second embodiment shown in Figure 2, in contrast to the first embodiment, features an elliptical ring-shaped torsion suspension 3. Furthermore, additional sensor elements 9 are positioned on the main surface of the torsion suspension 3, which is parallel to the main extending surface 21. The sensor elements 9 include a piezoelectric layer 90 (not shown) positioned between a first electrode 91 (not shown) and a second electrode 92. The second electrode 92 is segmented so that the sensor elements 9 on the torsion suspension 3 have multiple reading areas. The additional sensor elements 9 on the torsion suspension 3 can, for example, improve the measurement accuracy of the sensor elements.

[0083] Furthermore, in the second embodiment, the connecting element 6 is formed in an annular shape and has two suspension points 61 for the mirror element 2 along the short axis 32.

[0084] The micro-electromechanical mirror 1 of the second embodiment has the following features in particular: - Thickness of piezoelectric layer 50 and 90: 1.7 μm; - Thickness of Si substrate 8: 50 μm, short axis 32 is the crystal direction <100> Aligned along the crystal direction, the long axis 31 is the crystal direction <010> Aligned along; - Dimensions of the micro-electromechanical mirror 1 on the main extending surface 21: 7.65 mm × 9.35 mm; - Resonant frequency of the first vibration mode 11: 20.3 kHz; - Resonant frequency of the second vibration mode 12: 9.2 kHz; - Maximum displacement angle of mirror element 2 in the first vibration mode 11: 16.5°; - Maximum displacement angle of mirror element 2 in the second vibration mode 12: 11°; - Q coefficient of the vibration mode: 10³; - Anharmonicity of the first vibration mode 11: frequency shift of 184.6 Hz at displacement angles from 1° to 16.5°; - Anharmonicity of the second vibration mode 12: Frequency shift of -21.2 Hz at displacement angles from 1° to 11°; - Sensitivity of sensor element 9 to the first vibration mode 11: 0.5 μA / ° to 45.2 μA / °; - Sensitivity of sensor element 9 to the second vibration mode 12: 0.04 μA / ° or 19.2 μA / °.

[0085] Figures 3A to 3J show numerical simulations of various vibration modes of the micro-electromechanical mirror 1 according to the first embodiment. In particular, the displacements of various elements of the micro-electromechanical mirror 1 are exaggerated and enlarged at specific points in time for better visualization. The resonant frequencies fR of the vibration modes shown in the figures are summarized in the table below.

[0086] [Table 1]

[0087] [Table 2]

[0088] The vibration mode in Figure 3D corresponds to the second vibration mode 12 in the first embodiment, in which the mirror element 2 rotates and vibrates around the minor axis 32 together with the torsion suspension 3.

[0089] The vibration mode shown in Figure 3F corresponds to the first vibration mode 11 in the first embodiment, in which the mirror element 2 undergoes rotational vibration around the long axis 31, and the torsion suspension 3 undergoes bending motion in particular.

[0090] Since the resonant frequencies of the various vibration modes have particularly wide frequency intervals, the first and second vibration modes 11 and 12 can be excited as intended without exciting any further parasitic vibration modes.

[0091] Figure 4A shows a schematic diagram of the tensile stress (Zugspannung) in the material of the micro-electromechanical mirror 1 according to the first embodiment. In particular, the tensile stress in the micro-electromechanical mirror 12 at the maximum displacement angle of 11° of the mirror element 2 around the minor axis 32 in the second vibration mode 12 is shown. The maximum tensile stress is approximately 1.7 GPa.

[0092] Figure 4B shows a schematic diagram of the deformation of the main extending surface 21 of the mirror element 2 of the micro-electromechanical mirror 1 according to the first embodiment. In particular, the deformation in the direction perpendicular to the main extending surface 21 at the maximum displacement angle of 11° of the mirror element 2 around the minor axis 32 in the second vibration mode 12 is shown. In this case, the maximum deformation at the edge of the mirror element 2 is approximately ±250 nm.

[0093] Figure 5A shows a schematic diagram of the tensile stress in the material of the micro-electromechanical mirror 1 according to the first embodiment. In particular, the tensile stress in the micro-electromechanical mirror 11 is shown when the maximum displacement angle of the mirror element 2 around the minor axis 31 is 16.5° in the first vibration mode 11. The maximum tensile stress in this case is approximately 2.4 GPa.

[0094] Figure 5B shows a schematic diagram of a modified example of the main extending surface 21 of the mirror element 2 of the micro-electromechanical mirror 1 according to the first embodiment. In particular, it shows the deformation in the direction perpendicular to the main extending surface 21 when the maximum displacement angle of the mirror element 2 around the major axis 31 is 16.5° in the first vibration mode 11. In this case, the maximum deformation at the edge of the mirror element 2 is approximately ±250 nm.

[0095] Figure 6 shows the displacement angles φ1 and φ2 of the mirror element 2 around the major axis 31 and minor axis 32, as well as the maximum tensile stress Z, as a function of time t, for the material of the micro-electromechanical mirror 1 according to the first embodiment, during the vibration of the mirror element 2 corresponding to the first and second vibration modes 11 and 12.

[0096] Figure 7 shows the displacement angles φ1 and φ2 of the mirror element 2 around the major axis 31 and minor axis 32 of the micro-electromechanical mirror 1 according to the first embodiment, in which the first vibration mode 11 and the second vibration mode 12 are driven simultaneously. In particular, the displacement of the mirror traces a Lissajous figure as a function of time.

[0097] Figures 8A to 8J show numerical simulations of various vibration modes of the micro-electromechanical mirror 1 according to the second embodiment. In particular, the displacements of various elements of the micro-electromechanical mirror 1 are exaggerated and enlarged at specific points in time for better visualization. The resonant frequencies fR of the vibration modes shown in the figures are summarized in the table below.

[0098] [Table 3]

[0099] [Table 4]

[0100] The vibration mode in Figure 8D corresponds to the second vibration mode 12 in the second embodiment, in which the mirror element 2 rotates and vibrates around the short axis 32 together with the torsion suspension 3.

[0101] The vibration mode in Figure 8H corresponds to the first vibration mode 11 in the second embodiment, in which the mirror element 2 undergoes rotational vibration around the long axis 31, and the torsion suspension 3 undergoes bending motion in particular. Figure 9A shows a schematic diagram of the tensile stress in the material of the micro-electromechanical mirror 1 according to the second embodiment. In particular, it shows the tensile stress at the maximum displacement angle of 11° of the mirror element 2 around the minor axis 32 in the second vibration mode 12. The maximum tensile stress in this case is approximately 1.0 GPa.

[0102] Figure 9B shows a schematic diagram of a modified example of the main extending surface 21 of the mirror element 2 of the micro-electromechanical mirror 1 according to the second embodiment. In particular, it shows the deformation in the direction perpendicular to the main extending surface 21 when the mirror element 2 has a maximum displacement angle of 11° around the minor axis 32 in the second vibration mode 12. In this case, the maximum deformation at the edge of the mirror element 2 is approximately ±250 nm.

[0103] Figure 10A shows a schematic diagram of the tensile stress in the material of the micro-electromechanical mirror 1 according to the second embodiment. In particular, it shows the tensile stress in the micro-electromechanical mirror 11 when the maximum displacement angle of the mirror element 2 around the minor axis 31 is 16.5° in the first vibration mode 11. The maximum tensile stress in this case is approximately 1.5 GPa.

[0104] Figure 5B shows a schematic diagram of a modified example of the main extending surface 21 of the mirror element 2 of the micro-electromechanical mirror 1 according to the second embodiment. In particular, it shows the deformation in the direction perpendicular to the main extending surface 21 when the maximum displacement angle of the mirror element 2 around the major axis 31 is 16.5° in the first vibration mode 11. The maximum tensile stress in this case is approximately 1.5 GPa.

[0105] Figure 11 shows the displacement angles φ1 and φ2 around the major axis 31 and minor axis 32 of the mirror element 2, and the maximum tensile stress Z, as a function of time t, for the material of the micro-electromechanical mirror 1 according to the second embodiment, during the vibration of the mirror element 2 corresponding to the first and second vibration modes 11 and 12.

[0106] Figure 12 shows the displacement angles φ1 and φ2 of the mirror element 2 around the major axis 31 and minor axis 32 of the micro-electromechanical mirror 1 according to the second embodiment, in which the first vibration mode 11 and the second vibration mode 12 are driven simultaneously. In particular, the displacement of the mirror traces a Lissajous figure as a function of time.

[0107] Figure 13 shows a schematic cross-sectional view of the micro-electromechanical mirror 1 according to the second embodiment. In particular, a cross-section parallel and offset with respect to the minor axis 32 is shown. The mirror element 2, connecting element 6, torsion suspension 3, drive ring 5, and frame 7 are integrally formed with a common substrate 8. The substrate 8 has a constant thickness. A metal reflective layer 22 is disposed on the main surface 21 of the mirror element 2.

[0108] On the drive ring 5, a piezoelectric layer 50 is positioned between the first electrode 51 and the second electrode 52. A sensor element 9 is positioned on the torsion suspension 3, and the sensor element 9 includes a piezoelectric layer 9 between the first electrode 91 and the second electrode 92.

[0109] Figure 14 shows a schematic diagram of a projection device 1000 according to an embodiment, which is equipped with the micro-electromechanical mirror 1 described above. Furthermore, this projection device is equipped with a laser light source 200 that emits laser light 201 when in operation.

[0110] For example, the laser light source 200 can be a so-called RGB light source capable of emitting red, green, and blue laser light. For this purpose, the laser light source 200 may comprise, for example, three appropriately modulated laser diodes or groups of laser diodes. The laser beams can be superimposed, for example, in a beam combiner 202, so that the combined beam of laser light 201' is irradiated onto a piezoelectric mirror element 100 and reflected from there to a desired image region. The laser light source 200 can be controlled, for example, by laser control electronic equipment 206, which can, for example, temporally modulate the amplitudes of the laser beams 201, 201'.

[0111] The micro-electromechanical mirror 1 is controlled by a mirror control electronic device 203 and can scan a desired image area, for example, to generate a desired Lissajous figure. Furthermore, a sensor electronic device 204 may be provided to detect the position and / or frequency of the mirror element 2 of the micro-electromechanical mirror 1, preferably in real time. In addition, an image processing electronic device 205 may be provided, for example, to control the entire image display. This corresponds in particular to converting image information or film information into control signals for the laser light source 200 and the micro-electromechanical mirror 1, including temporal synchronization between the position of the mirror element 2 and the amplitude of the laser beams 201, 201'.

[0112] The present invention is not limited by the description based on the examples. Rather, the present invention includes all new features and all combinations of features, in particular all combinations of features described in the claims, even if the feature or combination itself is not explicitly described in the claims or examples. [Explanation of Symbols]

[0113] 1. Micro-electromechanical mirror (mikroelektromechanischer Spiegel) 11. First mode of oscillation (erste Schwingungsmode) 12. Second mode of oscillation (zweite Schwingungsmode) 2. Mirror element (Spiegelement) 21 Main extension plane (Haupterstreckungsebene) 22 Reflection layer 3. Torsion suspension (Torsionsaufhaengung) 31 Long axis 32 Short axis (kurze Achse) 41 First torsion spring element (erste Torsionsfederelemente) 42 Second torsion spring element (zweite Torsionsfederelemente) 43. Third Torsion Spring Element (dritte Torsionsfederelemente) 5. Drive ring (Antriebsring) 50 Piezoelectric layer 51 First electrode (erste Elektrode) 52 Second electrode (zweite Elektrode) 521a, 521b First drive control area (erster Ansteuerbereich) 522a, 522b Second drive control area (zweiter Ansteuerbereich) 6. Verbindungselement (connection element) 61 Suspension points (Aufhaengungspunkte) 62 Segments 7 Frames (Rahmen) 8. Substrat 9. Sensor element 90 Piezoelectric layer 91 First electrode (erste Elektrode) 92 Second electrode (zweite Elektrode) 200 Laser light sources (Laserlichtquelle) 201, 201' Laser light (Laserlicht) 202 Beam Combiner (Strahlkombinierer) 203 Mirror-controlled electronic equipment (Spiegel-Steuerelektronik) 204 Sensor Electronics (Sensorelektronik) 205 Image Processing Electronic Equipment (Bildprozessierungselektronik) 206 Laser-controlled electronic equipment (Lasersteuerelektronik) 1000 Projection devices t Time (Zeit) Z tensile stress (Zugspannung) φ1 Displacement angle around the long axis (Auslenkungswinkel um die lange Achse) φ2 Displacement angle around the minor axis (Auslenkungswinkel um die kurze Achse)

Claims

1. A micro-electromechanical mirror (1), Mirror element (2), A micro-electromechanical mirror comprising a torsion suspension (3) surrounding a mirror element (2) and connected to the mirror element (2) via two first torsion spring elements (41).

2. The micro-electromechanical mirror according to claim 1, further comprising a piezoelectric drive ring (5) surrounding the torsion suspension (3) and connected to the torsion suspension (3) via two second torsion spring elements (42).

3. The micro-electromechanical mirror according to claim 1 or 2, wherein the torsion suspension (3) has an elongated shape having a long axis (31) and a short axis (32) perpendicular thereto.

4. The micro-electromechanical mirror according to claim 3, wherein the first torsion spring element (41) is arranged along the long axis (31).

5. The micro-electromechanical mirror according to claim 3 or 4, wherein the second torsion spring element (42) is arranged along the minor axis (32).

6. The micro-electromechanical mirror according to any one of claims 1 to 5, wherein the two first torsion spring elements (41) are arranged on opposing surfaces of the mirror element (2).

7. The micro-electromechanical mirror according to any one of claims 2 to 6, wherein the two second torsion spring elements (42) are arranged on opposing surfaces of the torsion suspension (3).

8. The torsion suspension (3) has an elliptical ring shape or a flattened elliptical ring shape, according to any one of claims 1 to 7.

9. The micro-electromechanical mirror according to any one of claims 1 to 8, wherein the torsion suspension (3) does not have a piezoelectric drive element and / or is composed of a substrate.

10. The micro-electromechanical mirror according to any one of claims 1 to 9, wherein the mirror element (2) and the first torsion spring element (41) are connected to each other via a connecting element (6).

11. The micro-electromechanical mirror according to claim 10, wherein the connecting element (6) is formed in an annular shape and is connected to the mirror element (2) via two suspension points (61).

12. The micro-electromechanical mirror according to claim 11, wherein the two suspension points (61) are arranged along the minor axis (32) on opposing surfaces of the mirror element (2).

13. The micro-electromechanical mirror according to claim 10, wherein the connecting element (6) has two arc-shaped segments (62) that are separated from each other, each of which is connected to one of the two first torsion spring elements (41).

14. The micro-electromechanical mirror according to claim 13, wherein each of the arc-shaped segments (62) is connected to the mirror element (2) via the two suspension points (61).

15. The drive ring (5) is formed in an annular shape, as described in any one of claims 2 to 14.

16. The drive ring (5) is positioned in a stationary position on the main extending surface (21) of the mirror element (2), as described in any one of claims 2 to 15.

17. The drive ring (5) is connected to the frame (7) via two third torsion spring elements (43), as described in any one of claims 2 to 16.

18. The micro-electromechanical mirror according to claim 17, wherein the two third torsion spring elements (43) are arranged on opposing surfaces of the drive ring (2) along the minor axis (32).

19. The micro-electromechanical mirror according to claim 17 or 18, wherein the mirror element (2), the torsion suspension (3), the drive ring (5), the frame (7), and the torsion spring elements (41, 42, 43) are formed as an integral part.

20. The micro-electromechanical mirror according to claim 19, wherein all elements (2, 3, 41, 42, 43, 5, 7) of the integrated component are provided with a common substrate (8) having a certain thickness.

21. A micro-electromechanical mirror according to any one of claims 2 to 20, wherein a piezoelectric layer (50) is formed on the drive ring (5).

22. The piezoelectric layer (50) is disposed between the first electrode (51) and the second electrode (52) in the micro-electromechanical mirror according to claim 21.

23. The micro-electromechanical mirror according to claim 22, wherein the second electrode (52) has a plurality of drive control regions (521a, 521b, 522a, 522b) that are separated from each other.

24. The micro-electromechanical mirror according to any one of claims 17 to 23, wherein at least one sensor element (9) for determining the displacement and / or frequency of vibration of the mirror element (2) is disposed on the drive ring (5) and / or the frame (7).

25. The micro-electromechanical mirror according to any one of claims 1 to 24, wherein at least one sensor element (9) for determining the frequency of displacement and / or vibration of the mirror element (2) is disposed on the torsion suspension (3).

26. The micro-electromechanical mirror according to claim 24 or 25, wherein the at least one sensor element (9) includes a piezoelectric layer (90).

27. The micro-electromechanical mirror according to claim 26, wherein the piezoelectric layer (90) is disposed between two electrodes (91, 92).

28. The micro-electromechanical mirror according to any one of claims 1 to 27, wherein the torsion suspension (3) is provided to linearize the vibration modes around the long axis (31).

29. A method for operating a micro-electromechanical mirror according to any one of claims 2 to 28, wherein the mirror element (2) is set to a first vibration mode (11) by a first AC electrical signal of a first frequency acting on a first drive control region (521a, 521b) of the drive ring (5).

30. The method according to claim 29, wherein the torsion suspension (3) is set to a second vibration mode (12) by a second AC electrical signal of a second frequency acting on the second drive region (522a, 522b) of the drive ring (5).

31. The first vibration mode (11) includes rotation of the mirror element (2) around the major axis (31), The method according to claim 30, wherein the second vibration mode (12) includes rotation of the mirror element (2) about the minor axis (32).

32. The method according to claim 31, wherein the first vibration mode (11) and / or the second vibration mode (12) are resonantly excited.

33. The method according to any one of claims 29 to 32, wherein the motion of the drive ring (5) in the first vibration mode (11) and / or the second vibration mode (12) has an amplitude of one-fifth or less of the amplitude of the motion of the mirror element (2).

34. The method according to any one of claims 29 to 33, wherein the resonant frequency of the first vibration mode (11) is at least 1.3 times greater than the resonant frequency of the second vibration mode (12).

35. The method according to any one of claims 29 to 34, wherein the first vibration mode (11) and / or the second vibration mode (12) operate in the harmonic region.

36. The second vibration mode (12) is a torsional vibration of the torsion suspension (3) having the mirror element (2) around the minor axis. The method according to any one of claims 29 to 35, wherein the first vibration mode (11) is a combination of torsional vibration of the mirror element (2) about its long axis and bending motion of the torsion suspension (3).

37. A projection device (1000) comprising a laser light source (200) and a micro-electromechanical mirror (1) according to any one of claims 1 to 28.

38. A method for using the micro-electromechanical mirror according to any one of claims 1 to 28 for projection of information onto a surface, a head-up display, matrix illumination, a LiDAR application, a hologram projector, VR glasses, or AR glasses.

Images