Abstract:
The underlying invention presents a device which connects a vibratably suspended optical element to at least two actuators mounted fixedly on one side via curved spring elements, wherein the actuators are implemented to cause the vibratably suspended optical element to vibrate via the curved spring elements. Both the actuators and the entire system may be implemented to be more robust and be operated more reliably due to the curved shaping of the spring elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from German Patent Application No. 10 2013 209 234.2, which was filed on May 17, 2013, and is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    When operating micromirrors, including piezoelectric micromirrors operated in resonance, a frequent objective is to implement both a high resonant frequency and a large deflection of the micromirror. However, it is difficult to achieve a high resonant frequency in combination with a large deflection of the micromirror at the same time. U.S. Pat. No. 7,190,502 B2 describes a device using which a deflection of 12.4 mm can be achieved at a resonant frequency of 10.6 kHz. U.S. Pat. No. 8,125,699 B2 shows devices using which an amplitude of 5.25 mm can be achieved at a resonance frequency of 15.6 kHz and 9 mm at a resonant frequency of 304 Hz. Devices of U.S. Pat. No. 6,657,764 B1 can be operated at amplitudes of  40  mm at a resonant frequency of 500 Hz and an amplitude of 3.9 mm at a resonant frequency of 17.2 kHz. 
         [0003]    In order to simultaneously achieve large deflections and high resonant frequencies, EP 2233 961 A1 discloses a setup in which a vibratable, oscillating system comprises laterally arranged actuators and a micromirror arranged in the center which, connected to one another via a torsion spring, form a vibratable overall system and exhibit a common resonant frequency. In order to allow a high operating frequency, the actuators are driven in the “one-node mode”, which is the frequency of the second eigenmode of a bending beam. This requires a small layer thickness of the actuators, which makes mechanical stability of the structure sensitive towards mechanical damage and constant load. At the same time, the overall system exhibits a parasitic and, in operation, undesired mode which is very close to the “one-node mode”, making operation of the device presented in EP 2233 961 A1 difficult. 
         [0004]      FIG. 12  shows a figure from EP 2233 961 A1. 
         [0005]    U.S. Pat. No. 6,198,565 B1 presents one way of implementing micromirrors operated in resonance, using which large deflections, high resonant frequencies and operating modes which are clearly separated from other modes can be achieved. However, it is of disadvantage with this solution that the springs connecting the micromirror to the actuators are provided with high mechanical loads, with the result that high levels of material stress are already reached with moderate mirror deflections, causing the material of the springs to fail, so that the springs will break. 
         [0006]      FIGS. 13   a  and  13   b  show pictures of such a micromirror the spring elements of which contain defects. 
         [0007]    U. Baran et al., in their publication “High Frequency Torsional MEMS Scanner for Displays”, have achieved an optical scanning angle of the micromirror of 38.5° at a resonant frequency of 39.5 kHz using a design presented in  FIG. 14 . 
         [0008]    In this design, a cascading oscillator system is constructed from several vibration frames. The vibration frames here are formed of piezoelectric actuators which, in turn, are connected to the micromirror arranged in the center and an outer frame each via broad torsion springs. This avoids material overload and at the same allows a large scanning angle and, thus, a high amplitude and a high resonant frequency. Of disadvantage with this solution are, on the one hand, increased space requirements for the setup, since the dimensions of the individual components, due to the existence of a double frame and the large width of the springs, are correspondingly large and a relatively low energy efficiency of the setup, since both ends of the piezoelectric actuators are each mounted to be movable so that the force generated by the actuators cannot be transferred completely to the micromirror or the torsion springs. 
         [0009]    Consequently, a concept for suspending a micromirror which allows both high amplitudes and scanning angles and high resonant frequencies would be desirable. 
         [0010]    Thus, the object of the present invention is providing a device comprising a vibratably suspended optical element such that high material stress can be avoided and a higher resonant frequency of the optical element is allowed, while at the same time allowing energy-efficient operation of the device by an optimum flux of force. 
       SUMMARY 
       [0011]    According to an embodiment, a device may have: an optical element suspended to be vibratable via curved spring elements; and at least two actuators, each mounted fixedly on one side, which are connected to the vibratably suspended optical element via the curved spring elements to cause the vibratably suspended optical element to vibrate. 
         [0012]    According to another embodiment, a device may have: an optical element which is suspended to be vibratable via curved spring elements, wherein the curved spring elements are implemented such that a local orientation of each spring element along a longitudinal center line of the respective curved spring element fulfils the following characteristics: a histogram of the local orientation has a span of 60°; the histogram is not located in a contiguous or non-contiguous interval of a length of 6° to more than 90%. 
         [0013]    The central idea of the present invention is realizing that the above object can be achieved by connecting actuators which are each mounted fixedly on one side to the vibratably suspended micromirror via curved spring elements. The curved spring elements allow forces to be absorbed such that material failure is prevented despite high operating frequencies and deflection amplitudes. 
         [0014]    In accordance with one embodiment, a vibratably suspended micromirror is suspended at two actuators via four torsion springs, the torsion springs being multiply curved and arranged at a distance to a torsion axis of the micromirror so as to allow large deflections of the micromirror by making use of the lever law. 
         [0015]    In accordance with alternative embodiments, four torsion springs which connect the vibratably suspended micromirror to actuators all include only one radius of curvature, so that a larger axial extension of the actuators is combined with an efficient utilization of space by the spring elements. 
         [0016]    Further embodiments exhibit an arrangement of more than two actuators for causing the vibratably suspended micromirror to vibrate in order to allow tilting of the micromirror around an additional axis to the torsion axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which: 
           [0018]      FIG. 1  is a schematic illustration of the setup of a curved torsion spring; 
           [0019]      FIG. 2  shows a histogram of the curved torsion spring of  FIG. 1 ; 
           [0020]      FIG. 3  shows a top view of a device comprising a micromirror arranged at actuators using curved torsion springs; 
           [0021]      FIG. 4   a  shows a side view of the device of  FIG. 3  in a non-deflected state; 
           [0022]      FIG. 4   b  shows a side view of the device of  FIG. 3  in a deflected state; 
           [0023]      FIG. 5  shows a detailed view of a portion of the device of  FIG. 3 ; 
           [0024]      FIG. 6  shows a top view of a device in analogy to  FIG. 3  in which additionally there are straight torsion springs; 
           [0025]      FIG. 7  shows a top view of a device in analogy to  FIG. 3  in which the torsion springs comprise common regions adjacent to the micromirror; 
           [0026]      FIG. 8  shows a top view of a device comprising a micromirror arranged at actuators using singly curved torsion springs; 
           [0027]      FIG. 9  shows a histogram of a singly curved torsion spring of  FIG. 8 ; 
           [0028]      FIG. 10  shows a top view of a device in analogy to  FIG. 8  in which curved torsion springs comprising a common region, in analogy to  FIG. 7 , are additionally arranged between actuators and an anchor point; 
           [0029]      FIGS. 11   a - e  show schematic views of different arrangements of actuators relative to the torsion axis and another axis of symmetry; 
           [0030]      FIG. 12  shows a schematic top view of a device comprising torsion springs in accordance with known technology; 
           [0031]      FIGS. 13   a - b  show pictures of a device comprising torsion springs in accordance with known technology, exhibiting defects; and 
           [0032]      FIG. 14  is an illustration of a device comprising curved torsion springs in which the actuators are arranged to be deflectable on both sides. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]      FIG. 1  shows a curved torsion spring  14  which includes a longitudinal center line  32  along the longitudinal extension of the spring. Starting at a first end of the longitudinal center line  32 , it includes a curvature section  29  comprising a curvature of a radius of curvature r K1  around a curvature center  34  at an aperture angle  31 . The aperture angle  31  exemplarily is roughly 90°. In the further course of the longitudinal center line, it includes a curvature section  27  comprising a curvature of a radius of curvature r K2  around a curvature center  35  at an aperture angle  37  of, exemplarily, 180°. Starting at the section  27 , there is a region  39 , in the direction of the second end of the longitudinal center line  32 , in which the torsion spring  14  is formed to be straight and which consequently does not include any curvature, i.e. has a zero value curvature or an infinite radius of curvature. 
         [0034]    In the sections  27  and  29 , starting from the initial orientation, all the local orientations are arranged in an evenly distributed manner in an interval with a span of 90° and 180°, since all the orientations occur evenly since the sections of curvature are shaped to be arcs of a circle, whereas the local orientation in the region  39  is constant, due to the lack of curvature. 
         [0035]    The even distributions of sections  27  and  29  result in an even height of a base region of a histogram of the torsion spring  14 , whereas the sections where the torsion spring has no curvature and thus includes a constant local orientation result in an additional amplitude of the histogram for the orientations of these sections. 
         [0036]    The radii of curvature r K1 a-d and r K2 a-d may be in any relation to one another, wherein the centers  34  and  35  of the radii of curvature are arranged alternatingly on one side each along the course of the curved torsion spring  14 . A center of curvature arranged on one alternating side relative to an adjacent center of curvature corresponds to an alternating change in sign of the radius of curvature along the course of the longitudinal center line. 
         [0037]    Although in  FIG. 1  two radii of curvature, each having a center, are arranged on alternating sides along the longitudinal center line, only a single radius of curvature or any larger number of radii of curvature may be arranged along the longitudinal center line, wherein embodiments describe torsion springs comprising less than ten changes in sign of the radii of curvature. 
         [0038]    In combination with the curvature centers  34  and  35  and the radii of curvature r K1  and r K2 , the aperture angles  31  and  37  describe aperture angles of sectors of a circle along which the curvatures proceed, the aperture angles each being smaller than or equaling 180°. 
         [0039]    Although, in  FIG. 1 , the radius of curvature changes discontinuously along the length of the torsion spring, a continuous change is of course also possible, which will be discussed in connection with  FIG. 9 . 
         [0040]    Due to the alternating positioning of the curvature center relative to the side of the longitudinal center line  32 , in the case of a single curvature center, the curved torsion spring  14  has the course of an arc of a circle and, in the case of several curvature centers, an S-shaped course. 
         [0041]      FIG. 2  shows a histogram of the local orientation of a curved torsion spring  14  of  FIG. 1 , starting from section  39  in an orientation of −90°, which in the histogram is represented by the area  39 ′. In the section  39 , the local orientation is constant over the longitudinal extension, so that the length of section  39  is arranged proportionately in the histogram in an orientation of −90°. The following curvature to the right of the torsion spring towards an orientation of +90° results in a hatched base region  29 ′ in the histogram, which corresponds to the equidistribution of the local orientations along section  27  of the torsion spring  14 . The curvature to the left along section  29  which follows in the further spring course in section  29 , from the orientation of +90° to 0°, results in an unhatched area  29 ′ between 0° and +90° in the histogram. 
         [0042]    In accordance with the minimum of −90° and the maximum of +90° of the local orientations of the torsion spring, the span of the histogram is an interval of 180°. The interval here is formed continuously since every local orientation between −90° and +90° is formed in the course of the curved torsion spring  14 , wherein, as is represented by the hatched base region  27 ′ of the histogram, a portion of at least 10 percent of the histogram is distributed evenly between the minimum local orientation of −90° and a maximum local orientation of +90°. 
         [0043]    Alternative embodiments comprise curved torsion springs of only one or several radii of curvature, so that the span of the histograms is greater than 60° and smaller than 360°. 
         [0044]      FIG. 3  shows a device  10  comprising a vibratably suspended micromirror  12  which is suspended on center at two actuators  16   a  and  16   b  via four curved torsion springs  14   a - d.  The actuators  16   a  and  16   b  are each cantilevered fixedly on one side and arranged such that a deflectable end of the actuator faces the micromirror  12 . The actuators  16   a  and  16   b  are implemented to be piezo-actuators and each include a substrate and a piezoelectric functional layer arranged thereon so that the actuators  16   a  and  16   b  are implemented as bending beams. Driving an actuator  16   a  or  16   b  results in a deflection of the deflectable end arranged opposite the fixedly cantilevered side in the direction out of the plane of the drawing, as will be illustrated below graphically. 
         [0045]    When the actuators  16   a  and  16   b  are operated in opposite phases so that one of the actuators  16   a  or  16   b  moves in a direction facing the viewer and the other one of the actuators moves in a direction facing away from the viewer, the micromirror  12  tilts around a torsion axis  18 . However, when the actuators are operated in phase, the micromirror  12  moves out of the plane of the torsion axis  18 . The actuators  16   a  and  16   b,  the micromirror  12 , and the curved torsion springs  14   a - d  form a spring-and-mass system of a common resonant frequency. The actuators  16   a  and  16   b  are arranged to be symmetrical around the torsion axis  18 , wherein an also symmetrical tilting of the micromirror  12  around the torsion axis  18  is achieved. The curved torsion springs  14   a - d  are connected to the actuators  16   a  and  16   b  at actuator mounting places  22   a -d. The ends of the curved torsion springs  14   a - d  facing away from the actuators  16   a  and  16   b  are connected to the micromirror  12  at mirror mounting places  24   a - d.  Thus, both the actuator mounting places  22   a - d  and the mirror mounting places  24   a - d  are implemented such that the transitions from the curved torsion springs  14   a - d  to the actuators  16   a - b  and from the curved torsion springs  14   a - d  to the micromirror  12  are implemented to be rounded, wherein outer edges of the respective curved spring element  14   a - d  are guided to the actuator  16   a  or  16   b  and the micromirror  12  tangentially, wherein an angular or discontinuous transition between the elements is avoided. 
         [0046]    The curved course of the torsion springs  14   a - d  allows an implementation of the springs which is provided with a larger longitudinal extension compared to spring elements of a straight course so that forces induced by a deformation of the material of the springs are distributed in a larger material region. In contrast to torsion springs redirected in an angular and, thus, discontinuous manner, a continuous transition of the different radii of curvature results in force peaks at places of discontinuity to be avoided. 
         [0047]    A rounded transition between the actuator/spring or spring/micromirror elements reduces force peaks occurring in the material with a deformation and avoids excessive material fatigue at these places. The result is an additionally increased operating time of the device. 
         [0048]    In order to reduce rotational or tilting movements around an axis other than the torsion axis  18 , the actuator mounting places  22   a - d  are arranged relative to one another such that the actuator mounting places  22   a  and  22   b  and the actuator mounting places  22   c  and  22   d  are each arranged in pairs on a line  26   a  and  26   b , respectively, the lines  26   a  and  26   b  being parallel to the torsion axis  18 . In combination with a symmetrical arrangement of the mirror mounting places  24   a - d,  the result is minimization of movements of the micromirror  12  which are not around the torsion axis  18 . 
         [0049]    The actuators  16   a  and  16   b  may be configured such that a longitudinal extension x 1  of the actuators  16   a  and  16   b  is greater than a radius of the round micromirror  12 . Increasing the extension x 1  allows a larger deflection of the deflectable end of the actuators and thus of the actuator mounting places  22   a - d.  Said larger deflection produces a larger material deformation which is made possible by the shape of the curved torsion springs  14   a - d.  Thus, the longitudinal dimension x 1  represents a distance from the fixed cantilevered part of an actuator  16   a  or  16   b  along an axis arranged perpendicular to the torsion axis  18  to an actuator mounting place  22   a - b,  i.e. a dimension along an extension in which the actuators bend as a bending beam in accordance with the implementation. 
         [0050]    The mirror mounting places  24   a - d  are arranged at a distance x 3  from the torsion axis  18 . The distance x 3  generates a leverage such that a deflection of the actuators  16   a  and  16   b , induced by the actuators  16   a  and  16   b  and transmitted by the curved torsion springs  14   a - d  is transferred onto the micromirror  12  to an extent depending on the distance x 3 . 
         [0051]    The micromirror  12  in  FIG. 1  is formed to be of a round shape and of a constant radius r. In embodiments, an alternative micromirror includes a different shape, exemplarily that of an ellipse. In this case, the distance x 1  may be selected to be larger than half of the longest distance between any two points of a main side of the micromirror  12 . When, as is shown in  FIG. 1 , the micromirror  12  is formed to be a round element, half of the longest extension between any two points corresponds to the radius r. 
         [0052]    The distance x 3  defining the leverage allows a larger deflection of the micromirror  12  relative to an arrangement of torsion springs in the torsion axis with equal forces of the actuators  16   a  and  16   b , or an identical deflection of the micromirror  12  with a smaller actuator deflection. 
         [0053]    Further embodiments exhibit an arrangement of several actuators, wherein the actuators are arranged to be symmetrical around the torsion axis and/or an axis of symmetry perpendicular to the torsion axis and only a single curved torsion spring is arranged at each actuator. The distance x 2  is then determined as the distance between two actuator mounting places in a half-plane defined by the torsion axis or the axis of symmetry. 
         [0054]      FIG. 4   a  shows a side view of the device  10  in an undeflected state. The actuators  16   a  and  16   b , in analogy to  FIG. 3 , are each formed as piezo actuators including a substrate  28   a  and  28   b  and a piezoelectric functional layer. The actuators  16   a  and  16   b  include a thickness H 1  which is in a defined relation to a thickness H 2  of the micromirror  12 , the ratio between H 1  and H 2  roughly corresponding to 1:1. Alternative embodiments include a ratio between H 1  and H 2  between 0.1 and 2. 
         [0055]    The substrates  28   a  and  28   b  of the actuators  16   a  and  16   b , the curved torsion springs  14   a  and  14   b  and the micromirror  12  may, as is exemplarily illustrated in  FIGS. 4   a  and  4   b , be formed from the same material and integrally, wherein the integral characteristic may exemplarily be achieved from a common starting medium by means of a time-controlled etching process or an etch stop layer. In addition, the substrate  33  where the actuators  16   a  and  16   b  are suspended, is also formed integrally with the substrate  28   a  and  28   b  of the actuators  16   a  and  16   b  and, thus, the curved torsion springs  14   a  and  14   b , and the micromirror  12 , so that exemplarily the time-controlled etching process removes volume parts of a portion of a wafer at laterally and axially differing locations, wherein the structures of the substrate  28   a  and  28   b  of the actuators  16   a  and  16   b , that of the curved torsion springs  14   a  and  14   b  and of the micromirror  12  are formed, as is the substrate  33 , from the wafer portion. 
         [0056]      FIG. 4   b  shows the device  10  in a deflected state in which the actuator  16   a  is deflected in one direction and the actuator  16   b  in the opposite direction. The deflection of the actuators  16   a  and  16   b  results in a deformation of the curved torsion springs  14   a  and  14   b  and in tilting of the micromirror  12  around the torsion axis  18 . 
         [0057]      FIG. 5  shows part of  FIG. 1  with a top view of the mounting places  22   a  and  24   a  which connect the torsion spring  14   a  to the micromirror  12  and the actuator  16   a  tangentially, and the course of the curved torsion spring  14   a . Along its continuous course, a longitudinal center line  32   a  of the curved torsion spring  14   a  comprises the straight section  39   a  and the two curvature sections  27   a  and  29   a  each including a constant radius of curvature r K1 a and r K2 a and a curvature center  34   a  and  35   a , respectively. The local radii of curvature r K1 a and r K2 a may be implemented such that they are each larger than half of the mean width of the curved torsion spring and at the same time, in each curvature section  27   a  and  29   a , the mean value of the magnitude of the respective radius of curvature r K1 a or r K2 a is smaller than 10 times the overall length of the longitudinal center line  32   a.    
         [0058]    In accordance with alternative embodiments, a vibratably suspended optical element, exemplarily a micromirror, may also be arranged on a substrate via curved spring elements with no actuator, in particular when energy for causing the vibratably suspended optical element to vibrate is introduced into the vibratable system alternatively, exemplarily via a fluid stream flowing around the vibratably suspended optical element. 
         [0059]      FIG. 6  shows a top view of a device  20  in which the device  10  has been extended in that two additional torsion springs  36   a  and  36   b  of a straight shape are arranged at the micromirror  12 , of which the end facing away from the micromirror  12  is arranged at an immobile anchor point and the longitudinal course of which is identical to the torsion axis  18 . The straight torsion springs  36   a  and  36   b  here have no direct connection to the curved torsion springs  14   a - d.  The straight torsion springs  36   a  and  36   b  are configured to stabilize tilting of the micromirror  12 . 
         [0060]    Although the arrangement of two straight torsion springs  36   a  and  36   b  has been described for  FIG. 6 , alternative embodiments include a different number of straight torsion springs which are arranged symmetrically around and parallel to the torsion axis  18 . 
         [0061]      FIG. 7  shows a top view of a device  30  in which the micromirror  12  is arranged at the actuators  16   a  and  16   b  via four curved torsion springs  14   a - d.  Thus, the curved torsion springs  14   a - d  are shaped such that two curved torsion springs  14   a  and  14   c  and  14   b  and  14   d  each arranged on a side of an axis of symmetry  41  which is arranged to be perpendicular to the torsion axis  18  include a common section  38   a  and  38   b  of the torsion spring. Starting at the respective actuator mounting places, the curved torsion springs  14   a - d  follow a curved course to the torsion axis  18 , wherein the curved torsion spring  14   a  is merged with the curved torsion spring  14   c  and the curved torsion spring  14   b  is merged with the curved torsion spring  14   d  at the torsion axis  18 , forming the further straight part  38   a  of the curved torsion springs  14   a  and  14   c  and the further straight part  38   b  of the curved torsion springs  14   b  and  14   d , respectively. The distance x 3  of the device  10  in  FIG. 1  is implemented with a zero extension. 
         [0062]    Merging the curved spring elements as shown in the above embodiment allows compensating manufacturing tolerances when manufacturing the device such that, instead of four mirror mounting places, only two mirror mounting places are formed, for which consequently only one orientation relative to the torsion axis of the micromirror is necessitated, thus increasing the precision of the tilting motion of the micromirror  12 . 
         [0063]      FIG. 8  shows a second embodiment of a torsion spring. It shows a device  40  which includes singly curved torsion springs  42   a - d  which connect the micromirror  12  to the actuators  16   a  and  16   b  such that an excitation induced by the actuators  16   a  and  16   b  tilts the micromirror  12  around the torsion axis  18  or moves same along a plane which includes the torsion axis  18 . The singly curved torsion springs  42   a - d  are connected to the micromirror  12  at mirror mounting places  44   a -d. Thus, the mirror mounting places  44   a - d  are, in analogy to the mirror mounting places of preceding embodiments, configured to be rounded, so that peaks of material stress occurring at structural transitions between the singly curved torsion springs  42   a - d  and the micromirror  12  are minimized. 
         [0064]    A lateral distance x 2  between the actuator mounting places  46   a  and  46   b  and between  46   c  and  46   d  exemplarily is more than 150% of the largest distance between any two points of a main side of the micromirror  12 . A larger extension x 2  results in a greater deflecting force and, thus, a faster deflection of the micromirror  12 . 
         [0065]    In analogy to the actuator mounting places  22  of the curved torsion springs  14 , the actuator mounting places  46   a - d  of the singly curved torsion springs  42   a - d  are also implemented to be rounded or guided to the actuators  16   a  and  16   b  tangentially. Along a continuous longitudinal center line of the singly curved torsion springs  42   a - d,  all the radii of curvature of the singly curved torsion springs  42   a - d  are on the same side of the longitudinal center line, wherein a mean value of each radius of curvature is smaller than 10 times the length of the longitudinal center line. Thus, the singly curved torsion springs  42   a - d  are implemented such that their course basically corresponds to a quarter of an ellipse. 
         [0066]    Alternative embodiments exhibit singly curved torsion springs, the course of which roughly corresponds to an arc of a circle. Thus, along the courses, the singly curved torsion springs includes one or several radii of curvature around one or several curvature centers, wherein all the curvature centers are arranged on the same side of the longitudinal center line of the respective singly curved torsion spring and each local radius of curvature has, over a length of the center line, a larger magnitude than half of a mean width of the respective singly curved torsion spring. 
         [0067]    In order to reduce the space necessitated for the entire structure, this arrangement of singly curved torsion springs may be of advantage compared to an arrangement of curved torsion springs of the preceding embodiments. In  FIG. 8 , the curvature of the singly curved torsion springs  42   a - d  is implemented such that, starting from the actuator mounting places  46   a - d,  the singly curved torsion springs  42   a - d  include only sections which, except for the actuator mounting places  46   a - d,  are only directed towards the micromirror  12  or exhibit a curvature towards the micromirror  12 . In preceding embodiments, the curved torsion springs  14  have been implemented such that, starting from actuator mounting places  22   a - d,  sections of the curved torsion springs  14   a - d  face away from the micromirror  12  and a maximum lateral extension, in the direction of the torsion axis  18 , is defined by the lateral extension of the curved torsion springs  14   a - d.  The maximum lateral setup space in the direction of the torsion axis  18  of the device  40 , in contrast, is defined by the lateral extension of the actuators  16   a  and  16   b.    
         [0068]      FIG. 9  shows a histogram of the course of curvature of the singly curved torsion spring  42   c  of the device  40  of  FIG. 8  starting from the actuator  16   b  in the direction of the micromirror  12 . Starting with the tangential arrangement of the singly curved torsion spring  42   c  at the actuator  16   b  with the local orientation of 0°, the curvature of the singly curved torsion spring  42   c  develops continuously to an orientation of +90°. From a minimal orientation of 0° to a maximum orientation of +90°, the histogram has a span of 90°. At least 10% of the integral area of the histogram, which in  FIG. 9  is illustrated in a hatched manner, are arranged to be evenly distributed, which means: an equidistribution over the span of an area of 10% of the histogram remains below the histogram over the entire span. At the same time, the histogram of  FIG. 9  does not contain a contiguous or non-contiguous interval with a length of 6%, which includes the area of the histogram to more than 90% so that the orientations of a singly curved torsion spring include a measure of equidistribution within the span. The continuous course of the non-hatched region indicates that radii of curvature change continuously along the course of the torsion spring. 
         [0069]    Alternative embodiments include singly curved torsion springs the histograms of which comprise spans of larger than or equal to 60° and smaller than or equal to 270°. 
         [0070]      FIG. 10  shows a schematic top view of a device  60  including a micromirror  12  which is arranged at the actuators  16   a  and  16   b  via four singly curved torsion springs  42   a - d.  Additionally, curved torsion springs  14   a - d  which support deflection of the actuators  16   a  and  16   b  relative to the substrate  33  are arranged at the actuators  16   a  and  16   b . The curved torsion springs  14   a  and  14   c  and  14   b  and  14   d  each comprise, in pairs and in analogy to  FIG. 5 , the common sections  38   a  and  38   b , respectively, of the curved torsion springs. 
         [0071]    By additionally arranging curved torsion springs between the actuators and the substrate, stabilization of the deflection motion can be achieved, wherein, in principle, any combination of curved and singly curved torsion springs is possible. 
         [0072]    In principle, the ends of the curved torsion springs  14   a - d  facing away from the actuators  16   a  and  16   b  may also be arranged at further actuators in order for the micromirror  12  to be arranged to be rotatable along a second axis different from the torsion axis  18  and movable along an axis perpendicular to the torsion axis  18 . 
         [0073]      FIG. 11  schematically shows ways of arranging actuators  16   a - d  relative to the micromirror. 
         [0074]      FIG. 11   a , in analogy to the preceding embodiment, shows a symmetrical arrangement of the actuators  16   a  and  16   b  around the torsion axis  18 . The actuators  16   a  and  16   b  here are cantilevered fixedly at a side facing away from the micromirror  12 , in a parallel manner and spaced apart from the torsion axis  18 , and are arranged to be symmetrical to the axis of symmetry  41 . 
         [0075]      FIG. 11   b  shows an arrangement of four actuators  16   a - d  which are arranged to be both symmetrical to the torsion axis  18  and symmetrical to the axis of symmetry  41 , so that one actuator  16   a - d  each is arranged in a quadrant of a coordinate system spanned by the torsion axis  18  and the axis of symmetry  41 . 
         [0076]      FIG. 11   c  shows an arrangement of actuators in analogy to  FIG. 11   b , wherein an arrangement of further actuators is indicated by points between the actuators  16   a  and  16   b  and between the actuators  16   c  and  16   d . Further actuators are arranged to be symmetrical to the axis of symmetry  41 . When, for example, an additional fifth and sixth actuator are arranged,  FIG. 11   b  is extended in that the additional fifth and sixth actuator are arranged in the course of the axis of symmetry  41 . 
         [0077]      FIG. 11   d  shows an arrangement of actuators  16   a - d  in analogy to  FIG. 11   b , wherein the actuators are cantilevered fixedly in a course in parallel to the axis of symmetry  41  and the freely deflectable ends of the actuators  16   a - d  are facing the axis of symmetry  41  and are in parallel to the axis of symmetry  41 . 
         [0078]      FIG. 11   e  shows an arrangement of actuators  16   a - d  in analogy to  FIG. 11   d , wherein the fixed cantilevered part of the actuators  16   a - d  is arranged to be facing the axis of symmetry  41  and the freely deflectable end of the actuators  16   a - d  to be facing away from the axis of symmetry  41 . 
         [0079]    In principle, any number of actuators may be arranged, wherein the actuators are arranged to be both symmetrical to the torsion axis  18  and symmetrical to the axis of symmetry  41 , which is perpendicular to the torsion axis  18 , and the axes of symmetry cross in the center of the micromirror  12 . 
         [0080]    The embodiments described provide an oscillating system which includes a micromirror and external piezoelectric actuators. In contrast to known solutions, the actuators may be implemented such that they exhibit higher resonant frequencies than the micromirror, so that a greater layer thickness of the actuators may be used and the entire structure is implemented to be more robust due to the large layer thickness. 
         [0081]    Furthermore, the actuators may be operated in the zero-node mode, the first eigenmode of a bending beam. In contrast to the one-node mode, in the zero-node mode, neighboring parasitic modes in the frequency range are at relatively large distances to one another, so that the eigenmode is predominant and the influence of parasitic modes, which limits operation of the micromirror, is reduced. 
         [0082]    Furthermore, discontinuous material courses of torsion springs, like, for example, in the torsion springs shown in  FIG. 13 , formed at a 90° angle are avoided by the curved and singly curved torsion springs comprising a continuous course, and thus force peaks and mechanically overstressed locations along the course of the curved and singly curved torsion springs are prevented. Rounded or tangentially implemented mounting places of the springs at the micromirror and/or actuators additionally prevent mechanically overstressed locations from occurring at the ends of the torsion springs. 
         [0083]    All in all, the micromirror system described comprises a high resonant frequency and is of a stable and robust design. When the torsion springs are arranged on the micromirror at a distance from the torsion axis, the lever arm may be made use of in that the distance from the torsion axis to the mirror mounting places acts as a lever arm and the force of the actuators is transferred efficiently, thereby achieving a large deflection of the micromirror. Using the torsion springs as a lever at the same time prevents locations with too high a mechanical stress due to the design of the torsion springs and the mounting places at the actuators and the micromirror. 
         [0084]    Although the preceding embodiments have shown torsion springs connecting a micromirror to actuators, in principle different elements may also be arranged at the ends of the torsion springs facing away from the actuators, such as, for example, lenses or parts of electronic switches. 
         [0085]    While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which will be apparent to others skilled in the art and which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.