Micromirrors and projection device

Abstract

A micromirror is proposed comprising a mirror element (1) with a reflective surface, a first arm (2), a second arm (3), and a frame (4), wherein a first end (2a) of the first arm (2) is connected to the frame (4), wherein a second end (2b) of the first arm (2) is connected to the mirror element (1), wherein a first end (3a) of the second arm (3) is connected to the frame (4), wherein a second end (3b) of the second arm (3) is connected to the mirror element (1), wherein drive elements (8a-8c, 11a) are arranged on the first arm (2) and on the second arm (3) which are configured to bend the first arm (2) and the second arm (3), and wherein the mirror element (1) is arranged and connected to the second ends (2b, 3b) of the first and the second arm (2, 3) such that the bending of the first and second arms (2, 3) causes a tilting movement of the mirror element (1) about an axis of rotation.

Description

[0001] For projection applications, such as the projection of images and / or videos, as well as for lidar devices, there is a need for quasi-static mirrors for raster scanning. The mirrors should cover a frequency range up to an image refresh rate of 120 Hz non-resonantly and therefore have a resonant frequency greater than 120 Hz.

[0002] US 2015 / 0362724A1 describes an optical deflector device.

[0003] The object of the present invention is now to provide an improved micromirror.

[0004] A micromirror is proposed comprising a mirror element with a reflective surface, a first arm, a second arm, and a frame. A first end of the first arm is connected to the frame. A second end of the first arm is connected to the mirror element. A first end of the second arm is connected to the frame. A second end of the second arm is connected to the mirror element. Drive elements are arranged on the first and second arms, configured to bend the first and second arms. The mirror element is arranged and connected to the second end of the first and second arms such that bending the first and second arms causes the mirror element to tilt about an axis of rotation.

[0005] The first arm and the second arm can have drive sections, each with a drive element designed to bend the respective drive section. The first arm and the second arm can have a meandering structure in which the drive sections are arranged parallel to each other and connected by connecting sections.

[0006] The drive sections can be arranged such that their deflections add up to a total deflection. The total deflection of the first arm can be the sum of the individual deflections of each drive section. By using several individual drive sections, the micromirror can be designed more compactly, and it can be ensured that each drive section is deflected in such a way that the mirror element remains free of deformation and stress. This would not be possible with a comparable total deflection of a single section.

[0007] The drive sections can run perpendicular to an axis of rotation of the mirror element, wherein the first arm and the second arm each have connecting sections, wherein two drive sections are connected to each other by a connecting section, wherein the connecting sections run perpendicular to the drive sections and wherein no drive elements are arranged on the connecting sections.

[0008] The drive sections can have a width that indicates their extent in the direction of the axis of rotation, with the width of the drive sections decreasing from the first end of the first arm to the second end of the first arm. This decreasing width of the drive sections allows the resonant frequency of the mirror element to be increased compared to a mirror where all drive sections have the same width. Increasing the resonant frequency is advantageous for achieving the goal of quasi-static operation at a frequency of 120 Hz.

[0009] The drive sections can each have a constant width along their respective lengths. The length can define the extent of the drive sections perpendicular to their width and perpendicular to a substrate thickness. In an alternative embodiment, the drive sections can have a width that decreases along their respective lengths, with the width at the end of each drive section facing the first end being greater than the width at the end facing the second end. Accordingly, the width of the first arm can decrease continuously from its first end to its second end.

[0010] The drive sections can be of such a length that the mirror element tilts with minimal stress when the first and second arms are bent. In particular, the lengths of the drive sections should not be too long to ensure that the bending of the arms does not cause stress on the mirror element. The drive sections and drive elements can be designed such that each drive section is bent by a maximum angle α, for which the following holds: α22 from 1 - cosa by no more than 0.2%, preferably by no more than 0.1%.

[0011] The mirror element, the first arm, the second arm, and the frame can be formed from a structured silicon substrate. Accordingly, the elements can be manufactured in one piece from a single substrate.

[0012] The drive elements can incorporate piezoelectric layers. These piezoelectric layers can, for example, be made of PZT. The piezoelectric layers can be applied to the arms using a thin-film process.

[0013] The micromirror can include a control unit designed to apply a voltage to the piezoelectric layers. This control unit can be configured to apply a voltage with a bias voltage and an alternating voltage, where the alternating voltage varies between a minimum and a maximum value, while the bias voltage remains constant. The bias voltage can be selected to prevent the voltage, which is the sum of the bias voltage and the alternating voltage, from crossing zero. Applying the bias voltage ensures that the voltage applied to the drive elements never drops into the negative range during operation, thus preventing polarity reversal of the piezoelectric layers.

[0014] The mirror element can have a compensation layer on its back side, which faces the reflective surface. This compensation layer can be designed to counteract mechanical deformation of the mirror element caused by the application of preload and other manufacturing steps. In its resting state, where only the preload is applied to the drive elements, the mirror element is not bent, as the effects of the preload and the compensation layer cancel each other out.

[0015] According to an unclaimed comparative example, the first arm and the second arm can be connected to the mirror element at a first suspension point and a second suspension point, respectively. The first suspension point and the second suspension point can lie on the axis of rotation.

[0016] Alternatively, the second end of the first arm can be forked. The second end of the first arm is connected to the mirror element at several primary suspension points. The second end of the second arm can also be forked. The second end of the second arm is connected to the mirror element at several secondary suspension points. The primary and secondary suspension points can be connected by straight lines perpendicular to the axis of rotation.

[0017] The axis of rotation preferably passes through the center point of the mirror element. The micromirror can be designed to be operated quasi-statically or resonantly.

[0018] Another aspect concerns a projection device comprising the micromirror described above and a light source configured to emit a beam of light onto the reflecting surface, wherein the micromirror is configured to reflect the beam of light, and wherein the micromirror is configured to be moved such that the reflected beam of light performs a raster scan. The projection device may be a device for projecting images and / or videos or a lidar device.

[0019] The following are advantageous aspects. To facilitate referencing, the aspects are numbered. The characteristics of these aspects are relevant not only in combination with the specific aspect to which they refer, but also when considered separately. 1. Micromirrors, comprising: - a mirror element with a reflective surface, - a first arm, - a second arm, and - a frame, wherein a first end of the first arm is connected to the frame, wherein a second end of the first arm is connected to the mirror element, wherein a first end of the second arm is connected to the frame, wherein a second end of the second arm is connected to the mirror element, wherein drive elements are arranged on the first arm and on the second arm which are designed to bend the first arm and the second arm, wherein the mirror element is arranged and connected to the second ends of the first and the second arm in such a way that the bending of the first and the second arm causes a tilting movement of the mirror element about an axis of rotation. 2. Micromirrors according to aspect 1, wherein the first arm and the second arm have drive sections, wherein a drive element is arranged on each drive section which is designed to bend the respective drive section, wherein the drive sections are arranged parallel to each other. 3. Micromirror according to aspect 2, wherein the drive sections extend perpendicular to the axis of rotation of the mirror element, wherein the first arm and the second arm each have connecting sections, wherein each drive section is connected to each other by one of the connecting sections, wherein the connecting sections extend perpendicular to the drive sections, and wherein no drive elements are arranged on the connecting sections. 4. Micromirrors according to one of aspects 2 or 3, wherein the drive sections have a width that indicates their extension in the direction of the axis of rotation, wherein the width of the drive sections of the first arm decreases from the first end of the first arm to the second end of the first arm. 5. Micromirrors according to aspect 4, wherein the drive sections have a constant width over their respective length, the length being perpendicular to the width of the drive section. 6. Micromirrors according to aspect 4, wherein the drive sections have a width decreasing over their respective lengths, the length being perpendicular to the width of the drive section, and the width of the drive sections at the end of the respective drive section connected to the first end being greater than the width of the drive sections at the end of the drive section connected to the second end. 7. Micromirror according to one of aspects 2 to 6, wherein the drive sections have such a length that the mirror element is tilted with minimal stress and deformation when the first and second arms are bent. 8. Micromirrors according to one of aspects 2 to 7, wherein the drive sections and the drive elements are designed such that each of the meandering sections is bent by a maximum angle α such that α2 / 2 deviates from 1-cos(α) by no more than 0.2%. 9. Micromirrors according to one of the previous aspects, wherein the mirror element, the first arm, the second arm and the frame are formed by a structured silicon substrate. 10. Micromirrors according to one of the previous aspects, wherein the driving elements have piezoelectric layers. 11. Micromirror according to aspect 10, comprising a control unit designed to apply a voltage to the piezoelectric layers, wherein the voltage is composed of a bias voltage and an alternating voltage, and wherein the bias voltage is chosen such that a zero crossing of the voltage is avoided. 12. Micromirror according to one of the previous aspects, wherein the mirror element has a compensation layer on a back side opposite the reflecting surface. 13. Micromirrors according to aspect 11 and aspect 12, wherein the compensation layer is designed to compensate for a mechanical deformation of the mirror element caused by the prestress. 14. Micromirror according to one of the previous aspects, wherein the first arm and the second arm are connected to the mirror element at a first suspension point and a second suspension point, and wherein the first suspension point and the second suspension point lie on the axis of rotation. 15. Micromirror according to one of aspects 1 to 13, wherein the second end of the first arm is connected to the mirror element at several suspension points, wherein the second end of the second arm is connected to the mirror element at several suspension points. 16. Micromirror according to aspect 15, wherein the suspension points at which the second end of the first arm is connected to the mirror element and the suspension points at which the second end of the second arm is connected to the mirror element can be connected to each other by straight lines perpendicular to the axis of rotation. 17. Micromirror according to one of the previous aspects, wherein the axis of rotation passes through a center point of the mirror element. 18. Micromirror according to one of the previous aspects, wherein the micromirror is designed to be operated quasistatically, or wherein the micromirror is designed to be operated resonantly. 19. Projection device comprising a micromirror according to one of the preceding aspects and a light source configured to emit a beam of light onto the reflecting surface, wherein the micromirror is configured to reflect the beam of light, wherein the micromirror is configured to be moved such that the reflected beam of light performs a raster-like scan. 20. Projection device according to the previous aspect, wherein it is a device for projecting images and / or videos or a lidar device.

[0020] Preferred embodiments of the present invention are described below with reference to the figures. The Fig. 1 and Fig. Figure 2 shows a micromirror in perspective view. Fig. Figure 3 schematically shows how a deflection of a mirror element by 3 α can be caused by deflecting three drive sections by the angle α each. The Fig. Figures 4 to 6 show a simulation of the deformation of the micromirror. Fig. Figure 7 shows a diagram illustrating the maximum mechanical deflection of the mirror element and the phase between the control signal and the mechanical deflection for different frequencies of the control signal. Fig. Figure 8 shows the micromirror according to a second embodiment. Fig. Figure 9 shows the distortion of a mirror element 1 according to the first embodiment. Fig. Figure 10 shows the distortion of the mirror element 1 according to the second embodiment.

[0021] The Fig. 1 and Fig. Figure 2 shows a micromirror in perspective view. Fig. Figure 1 shows a perspective view of the top. Fig. Figure 2 shows a perspective view of the underside of the micromirror.

[0022] The micromirror comprises a mirror element 1, a first arm 2, a second arm 3, and a frame 4. The mirror element 1, the first arm 2, the second arm 3, and the frame 4 are formed in one piece from a single silicon substrate, with a reflective layer being applied to the mirror element 1 in addition to the structuring of the silicon substrate, and drive elements being applied to both the first arm 2 and the second arm 3.

[0023] The mirror element 1 is a flat structure, for example a disk, preferably a circular disk, or a flat, rectangular structure. The mirror element 1 has a reflective layer, for example a reflective coating, on its upper surface. The mirror element 1 is configured to reflect a light beam incident on its upper surface.

[0024] Mirror element 1 is designed to perform a tilting movement about a rotational axis. In doing so, mirror element 1 is deflected from its rest position. Depending on the respective deflection angle, a light beam incident on mirror element 1 is reflected at different angles of incidence. In this way, mirror element 1 can be designed to perform a scan, for example a raster scan, of the light beam.

[0025] The first arm 2 and the second arm 3 are identical in their structural design and functional properties. Therefore, only the first arm 2 will be described in detail below.

[0026] The first arm 2 connects the mirror element 1 to the frame 4. A first end 2a of the first arm 2 is attached to the frame 4. The first end 2a of the first arm 2 is directly connected to the frame 4. A second end 2b of the first arm 2, opposite the first end 2a, is attached to the mirror element 1. The second end 2b of the first arm 2 is directly connected to the mirror element 1. The first arm 2 is designed to bend, whereby the second end 2b of the first arm 2 moves relative to the first end 2a. The bending of the first arm 2 triggers the tilting movement of the mirror element 1.

[0027] The frame 4, to which the first end 2a of the first arm 2 is connected, is not moved by bending the first arm 2. The frame 4 is therefore static.

[0028] The first arm 2 has drive sections 5a, 5b, 5c, connecting sections 6a, 6b, and an end section 7. The drive sections 5a, 5b, 5c and the connecting sections 6a, 6b form a meandering structure of the first arm 2. A drive element 8a, 8b, 8c is arranged on each of the drive sections 5a, 5b, 5c. The drive sections 5a, 5b, 5c are arranged parallel to each other. The connecting sections 6a, 6b each connect two adjacent drive sections. No drive elements are arranged on the connecting sections 6a, 6b.

[0029] The one in the Fig. 1 and Fig. The first arm 2 of the micromirror shown in Figure 2, according to a first embodiment, has three drive sections 5a, 5b, 5c and two connecting sections 6a, 6b. In alternative embodiments, the first arm can have n drive sections and n-1 connecting sections, where n can be any integer greater than or equal to 2.

[0030] The drive elements 8a, 8b, and 8c each have a piezoelectric layer. This layer can be a piezoelectric thin film. The piezoelectric thin film can be applied using a coating process, such as vapor deposition, sputtering, or sputtering variations. The piezoelectric material can be lead zirconium tanate (PZT). Additionally, the drive elements 8a, 8b, and 8c have electrodes that allow a voltage to be applied to the piezoelectric layers.

[0031] The first arm 2 has a first group of drive elements 8a, 8c and a second group of drive elements 8b. A drive element 8a of the first group is arranged on the drive section 5a, which is directly connected to the frame 4. On each of the drive sections 5b, which are directly connected by a connecting section 6a to a drive section 5a on which a drive element 8a of the first group is arranged, a drive element 8b of the second group is arranged. On each of the drive sections 5c, which are directly connected by a connecting section 6b to a drive section 5b on which a drive element 8b of the second group is arranged, a drive element 5c of the first group is again arranged. This results in a structure in which drive elements 8a, 8c of the first group and drive elements 8b of the second group alternate along the first arm 2.

[0032] An AC voltage signal and a bias voltage are applied to the drive elements 8a, 8b, 8c. The AC voltage signal applied to the drive elements 8a, 8c of the first group is phase-shifted by 180° relative to the AC voltage signal applied to the drive elements 8b of the second group. The drive elements 8a, 8b, 8c of two adjacent drive sections 5a, 5b, 5c are thus controlled with opposite polarities.

[0033] The phase shift of the applied alternating voltage signal causes two adjacent drive sections to bend in opposite directions. Due to the meandering structure of the first arm 2, the first arm 2 is bent entirely in one direction.

[0034] The end section 7 connects the last drive section 5c in the direction of the mirror element 1 to the mirror element 1. The end section 7 has the second end 2b of the first arm 2. The end section 7 is fork-shaped and connected to the mirror element 1 at several suspension points 9a, 9b. In the Fig. 1 and Fig. In the embodiment shown in Figure 2, the end section 7 of the first arm 2 is connected to the mirror element 1 at two suspension points 9a, 9b.

[0035] The second arm 3 is designed analogously to the first arm 2. A first end 3a of the second arm 3 is connected to the frame 4, and a second end 3b of the second arm 3 is connected to the mirror element 1.

[0036] The second arm 3 is arranged rotationally symmetrically to the first arm 2, with rotational symmetry about a 180° rotation about an axis through the center of the mirror element 1, which is perpendicular to the surface of the mirror element 1. The drive section 10a of the second arm 3, which is directly connected to the frame 4, has a drive element 11a of the second group. The drive sections 10a, 10b, 10c of the second arm 3 are thus controlled in the opposite direction to the corresponding drive sections 5a, 5b, 5c of the first arm 2. If the second end 2b of the first arm 2 is moved in the first direction, the second end 3b of the second arm 3 is moved in the opposite, negative first direction.

[0037] If, for example, the second end 2b of the first arm is now placed in the representation plane of the Fig. 1 moved inwards and simultaneously the second end 3b of the second arm 3 out of the representation plane of the Fig. When 1 is moved outwards, a tilting movement of the mirror element 1 around the axis of rotation is caused, whereby the upper half of the mirror element 1 is tilted forwards out of the plane of representation and the lower half of the mirror element 1 is tilted backwards into the plane of representation.

[0038] In the first embodiment of the micromirror, which is located in the Fig. 1 and Fig. As shown in Figure 2, the first arm 2 and the second arm 3 are each connected to the mirror element 1 at several suspension points 9a, 9b, 12a, 12b. Each suspension point 9a, 9b, where the second end 2b of the first arm 2 is connected to the mirror element 1, is located opposite a suspension point 12a, 12b, where the second end 3b of the second arm 3 is connected to the mirror element 1. The two suspension points 9a, 12a and 9b, 12b can be connected by a straight line perpendicular to the axis of rotation.

[0039] The drive sections 5a-5c and 10a-10c have a length, a width, and a thickness, all of which are perpendicular to each other. The thickness indicates the extent of the drive sections 5a-5c and 10a-10c in the direction where their extent is smallest. The thickness of the drive sections 5a-5c and 10a-10c corresponds to the thickness of the silicon substrate from which they are structured. The length of the drive sections 5a-5c and 10a-10c indicates their extent in the direction in which they are bent by applying a voltage to the drive elements. The width indicates the extent of the drive sections 5a-5c, 10a-10c in a direction perpendicular to the thickness and length. The width indicates an extent of the drive sections 5a-5c, 10a-10c in a direction along the axis of rotation of the mirror element 1.

[0040] The drive sections 5a-5c of the first arm 2 differ from each other in their width. The drive section 5a, which is connected to the frame 4, has the greatest width. Towards the second end 2b of the first arm 2, the width of the drive sections 5a-5c decreases. A drive section located closer to the second end 2b of the first arm 2 than a drive section located closer to the first end 2a has a smaller width. The drive sections 10a-10c of the second arm 3 also differ from each other in their respective widths.

[0041] The resonant frequency of the first and second arms 2, 3 is altered, and in particular increased, by reducing the width of the drive sections 5a-5c, 10a-10c towards the second end, compared to an arm where all drive sections have the same width. This variation in the width of the drive sections 5a-5c, 10a-10c thus results in a higher resonant frequency of the first and second arms 2, 3 during bending. The increased resonant frequency contributes to exciting the mirror element 1 into a tilting movement with minimal stress and deformation.

[0042] For example, the width of the drive section 5a, which is directly connected to the frame 4, can be between 2 and 4 mm, preferably between 2.5 and 3 mm. The width of the drive section 5c, which is connected to the end section, can be between 0.5 mm and 2.5 mm, preferably between 0.5 mm and 1.5 mm.

[0043] In the first embodiment, the width of the drive sections 5a-5c increases from the second end 2b to the first end 2a from 1.0 mm, to 1.67 mm, to 2.78 mm. The width of the connecting sections 6a, 6b increases from 0.7 mm, to 0.8 mm, to 1.0 mm.

[0044] In the first embodiment, the outer dimensions of the frame are 15.1 mm and 6.2 mm. The thickness of the silicon substrate on which the frame 4, the arms 2, 3 and the mirror element 1 are structured can be between 250 µm and 500 µm, for example 380 µm.

[0045] The thickness of the drive elements 5a-5c, 10a-10c is the sum of the thicknesses of two electrode layers and the thickness of a piezoelectric layer. The thickness of the piezoelectric layer is between 1 µm and 3 µm, and is preferably 1.7 µm.

[0046] The diameter of the mirror element 1 is between 1 mm and 10 mm, preferably between 2 mm and 5 mm, and is, for example, 3 mm. The length of the drive sections 5a-5c, 10a-10c corresponds to the diameter of the mirror element 1.

[0047] The meandering structure of the first and second arms 2, 3 can also be described as an arm folding. This meandering structure avoids excessively long sections. Excessively long arm sections, from which the mirror element 1 is suspended, would reduce the resonant frequency.

[0048] The length of the drive sections, in which they are bent, is chosen such that the following approximation applies: (α)22≈1−cos(α□). Here, α represents the maximum deflection of the drive sections 5a-5c and 10a-10c that they experience during operation of the micromirror. The approximation is considered satisfactory if the two values ​​differ from each other by no more than 0.2%, preferably by no more than 0.1%.

[0049] If arms 2, 3 are formed with n meandering drive sections, each of which can be deflected by a maximum angle α_max, then a total deflection of the mirror element 1 by n×α_max is achieved. If the above approximation is satisfied, then the mirror element 1 is deflected almost without stress and almost without deformation.

[0050] Fig. Figure 3 schematically shows how a deflection of the mirror element by 3 α can be caused by deflecting three drive sections 5a, 5b, 5c by the angle α each.

[0051] The drive elements 8a-8c and 10a-10c feature piezoelectric thin films. These are operated beyond their coercive field strength. Therefore, negative voltages should not be applied to the piezoelectric elements, as this would reverse the polarity of the piezoelectric layer. A bias voltage is therefore applied to the piezoelectric layers. The bias voltage is selected such that a positive potential is always present at the drive elements. The bias voltage can range between 5 V and 25 V, and can be, for example, 10 V.

[0052] Applying the preload can cause mechanical distortion of the mirror element 1. One or more compensation layers 13 can be applied to the back side of the mirror element 1, opposite the reflective top side, to compensate for this mechanical distortion. The piezoelectric layer is under tensile stress, which is increased by applying the preload. In the factory state, without the preload, the mirror element is distorted by the compensation layers 13. In a rest state, with only the preload applied to the drive elements, the distortion caused by the preload and the compensation layers 13 cancel each other out, so the mirror element is not distorted.

[0053] Fig. Figure 4 shows the result of a simulation in which the preload is not taken into account and the AC voltage applied to the drive elements is between 4 V and -4 V. This results in a deflection of the mirror element of 9.1°, resulting in a full optical angle of 36.4°. The coefficient e31f was set to 16.25 C / m. 2 assumed.

[0054] Fig. 5 also shows this simulation, where in Fig. Figure 5 shows the deflection of the elements of the micromirror. The greatest deflection is experienced by the end sections 7 of the first and second arms 2, 3.

[0055] In Fig. Figure 6 shows a simulation of the static deformation of the mirror element 1 in nm at a deflection of 15°.

[0056] The micromirror can be operated either quasi-statically or in resonance. In quasi-static operation, the frequency of the applied alternating voltage is below the resonant frequency of the micromirror.

[0057] In Fig. Figure 7 shows the frequency of the signals applied to the drive elements 8a-8c and 10a-10c on the horizontal axis. The mechanical displacement is plotted on the vertical axis for curve K1, and the phase between the control signal and the mechanical displacement is plotted on curve K2. Resonance behavior occurs at a frequency of approximately 320 Hz.

[0058] Fig. Figure 8 shows the micromirror according to a second embodiment. The second embodiment differs from the first embodiment in the design of the end sections 7.

[0059] In the second embodiment, the first arm 2 and the second arm 3 are each connected to the mirror element at a suspension point 14, 15, with the two suspension points lying on the axis of rotation. The end section 7 of the first arm 2 and the end section of the second arm 3 are connected to each other.

[0060] The second embodiment is characterized by high robustness against insufficient flatness of the mirror element 1 in its initial state. It ensures that mechanical distortions occur essentially outside the mirror element.

[0061] Fig. Figure 9 shows the distortion of a mirror element 1 according to the first embodiment. Fig. Figure 10 shows the distortion of the mirror element 1 according to the second embodiment. A deflection of 15° and an applied voltage of 4 V are assumed in each case. A comparison of the Fig. 9 and Fig.Figure 10 shows that the mirror element 1 in the second embodiment experiences less mechanical distortion. However, the resonant frequency of the second embodiment is somewhat lower than that of the first embodiment. The resonant frequency can be 288 Hz. The second embodiment has slightly larger external dimensions than the first embodiment if the mirror element, the drive sections, and the connecting sections are identical. For example, the external dimensions can be 15.74 mm and 6.2 mm.

[0062] The mirror element 1 and the drive sections 5a-5c, 10a-10c are arranged such that the centerline of the mirror element 1, which is perpendicular to the length of the drive sections 5a-5c, 10a-10c, and the centerlines of the drive sections 5a-5c, 10a-10c, which are perpendicular to the length of the respective drive sections, are not offset from each other in the length direction. The mirror element 1 is thus located in the middle of the direction in which the drive sections 5a-5c, 10a-10c can be bent. This prevents the micromirror from jamming. Reference symbol list 1 mirror element 2 first arm 2a first end of the first arm 2b second end of the first arm 3 second arm 3a first end of the second arm 3b second end of the second arm 4 frames 5a, 5b, 5c Drive section of the first arm 6a, 6b Connecting section of the first arm 7 End section of the first arm 8a, 8b, 8c Drive element of the first arm 9a, 9b Suspension point of the first arm 10a, 10b, 10c Drive section of the second arm 11a Drive element of the second arm 12a, 12b Suspension point of the second arm 13 Compensation layer 14, 15 Suspension point (second embodiment)

Claims

[1] Micromirrors, comprising: - a mirror element (1) with a reflective surface, - a first arm (2), - a second arm (3), and - a frame (4), wherein a first end (2a) of the first arm (2) is connected to the frame (4), wherein a second end (2b) of the first arm (2) is connected to the mirror element (1), wherein a first end (3a) of the second arm (3) is connected to the frame (4), wherein a second end (3b) of the second arm (3) is connected to the mirror element (1), wherein drive elements (8a-8c, 11a) are arranged on the first arm (2) and on the second arm (3) which are designed to bend the first arm (2) and the second arm (3), wherein the mirror element (1) is arranged and connected to the second ends (2b, 3b) of the first and second arms (2, 3) in such a way that bending the first and second arms (2, 3) causes a tilting movement of the mirror element (1) about an axis of rotation, wherein the second end (2b) of the first arm (2) is connected to the mirror element (1) at several suspension points (9a, 9b), wherein the second end (3b) of the second arm (3) is connected to the mirror element (1) at several suspension points (12a, 12b). [2] Micromirrors according to claim 1, wherein the first arm (2) and the second arm (3) have drive sections (5a-5c, 10a-10c), wherein a drive element (8a-8c, 11a) is arranged on each drive section (5a-5c, 10a-10c) which is configured to bend the respective drive section (5a-5c, 10a-10c), wherein the drive sections (5a-5c, 10a-10c) are arranged parallel to each other. [3] Micromirrors according to claim 2, wherein the drive sections (5a-5c, 10a-10c) run perpendicular to the axis of rotation of the mirror element (1), wherein the first arm (2) and the second arm (3) each have connecting sections (6a, 6b), wherein each drive section (5a-5c, 10a-10c) is connected to each other by one of the connecting sections (6a, 6b), wherein the connecting sections (6a, 6b) run perpendicular to the drive sections (5a-5c, 10a-10c), and wherein no drive elements are arranged on the connecting sections (6a, 6b). [4] Micromirrors according to one of claims 2 or 3, wherein the drive sections (5a-5c, 10a-10c) have a width that indicates their extent in the direction of the axis of rotation, wherein from the first end (2a) of the first arm (2) to the second end (2b) of the first arm (2) the width of the drive sections (5a-5c) of the first arm (2) decreases. [5] Micromirrors according to claim 4, wherein the drive sections (5a-5c, 10a-10c) have a constant width over their respective lengths, where the length is perpendicular to the width of the drive section (5a-5c, 10a-10c). [6] Micromirrors according to claim 4, wherein the drive sections (5a-5c, 10a-10c) have a width that decreases over their respective lengths, the length being perpendicular to the width of the drive section (5a-5c, 10a-10c), wherein the width of the drive sections (5a-5c, 10a-10c) at the end of the respective drive section (5a-5c, 10a-10c) that is connected to the first end (2a, 3a) is greater than the width of the drive sections (5a-5c, 10a-10c) at the end of the drive section (5a-5c, 10a-10c) that is connected to the second end (2b, 3b). [7] Micromirror according to any one of claims 2 to 6, wherein the drive sections (5a-5c, 10a-10c) have a length such that the mirror element (1) is tilted with minimal stress and deformation when the first and second arms (3) are bent. [8] Micromirrors according to any one of claims 2 to 7, wherein the drive sections (5a-5c, 10a-10c) and the drive elements (8a-8c, 11a) are designed such that each of the meandering sections is bent by a maximum angle α such that α 2 / 2 of 1-cos(α) deviates by no more than 0.2 %. [9] Micromirror according to one of the preceding claims, wherein the mirror element (1), the first arm (2), the second arm (3) and the frame (4) are formed by a structured silicon substrate. [10] Micromirrors according to one of the preceding claims, wherein the drive elements (8a-8c, 11a) have piezoelectric layers. [11] Micromirrors according to claim 10, comprising a control unit designed to apply a voltage to the piezoelectric layers, where the voltage is composed of a bias voltage and an alternating voltage, and where the pre-voltage is chosen such that a zero crossing of the voltage is avoided. [12] Micromirror according to one of the preceding claims, wherein the mirror element (1) has a compensation layer (13) on a back side opposite the reflecting surface. [13] Micromirrors according to claim 11 and claim 12, wherein the compensation layer (13) is configured to compensate for a mechanical deformation of the mirror element (1) caused by the preload. [14] Micromirrors according to any one of the preceding claims, wherein the second end (2b) of the first arm (2) is fork-shaped, wherein the second end (3b) of the second arm (3) is fork-shaped. [15] Micromirrors according to one of the preceding claims, wherein the suspension points (9a, 9b) at which the second end (2b) of the first arm (2) is connected to the mirror element (1) and the suspension points (12a, 12b) at which the second end (3b) of the second arm (3) is connected to the mirror element (1) can be connected to each other by straight lines that are perpendicular to the axis of rotation. [16] Micromirror according to one of the preceding claims, wherein the axis of rotation passes through a center point of the mirror element (1). [17] Micromirrors according to any one of the preceding claims, where the micromirror is designed to be operated quasi-statically, or the micromirror is designed to be operated resonantly. [18] Projection device comprising a micromirror according to one of the preceding claims and a light source configured to emit a beam of light onto the reflecting surface, the micromirror is designed to reflect the light beam, the micromirror is designed to be moved in such a way that the reflected light beam performs a raster-like scan. [19] Projection device according to the previous claim, wherein the device is a device for projecting images and / or videos or a lidar device.

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