Abstract:
An arrangement for a micro-mechanical beam includes a support structure to provide an increase in bending stiffness of the micro-mechanical beam without significantly influencing torsional stiffness, where the support structure is configured to directly attach to the micro-mechanical beam.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an improved micro-mechanical beam or spring configuration for using micro-mechanical applications, micro-mechanical mirrors. 
       BACKGROUND OF THE INVENTION 
       [0002]    German Published Patent Application No. 198 51 667 refers to a basic configuration of a micro-mechanical mirror arrangement, in which a micro-mechanical mirror plate is suspended by one or more torsional beams or beam springs. To allow large deflection angles of the mirror plate, the torsional beams may be required to be thin and long which may be prone to break. 
         [0003]    German Published Patent Application No. 199 63 382 and German Published Patent Application No. 199 41 045 refer to a modification which may provide a more robust configuration of the micro-mechanical mirror arrangement. The modification may relieve stress upon the micro-mechanical torsional beams if the micro-mechanical mirror plate is moved in a direction that is vertical to the plane of the micro-mechanical mirror plate, but not if the micro-mechanical mirror plate is moved in a direction that is parallel or “in-plane” with the micro-mechanical mirror plate. To increase the robustness further, the thickness of the micro-mechanical beams may be increased and/or their length may be reduced. However, such changes to the length and thickness may decrease the “freedom of movement” of the micro-mechanical beam. 
         [0004]    German Published Patent Application No. 199 63 382 and German Published Patent Application No. 199 41 045 refer to a two parallel beam configuration, as well as the transformation of bending in a vertical direction perpendicular to the surface of the substrate (i.e. the Z-direction) in tension by using a transversal beam. The resulting stiffness of the whole structure may therefore be significantly higher than that for a single spring of the basic configuration. 
       SUMMARY OF THE INVENTION 
       [0005]    It is believed that an exemplary embodiment of the present invention may provide enhanced protection for micro-mechanical torsional beam springs via the addition of one or more support structures that may attach directly to the micro-mechanical beam. The attachable structures may assist in limiting the “freedom of movement” of the micro-mechanical beam in a more precise manner by preventing undesirable bending actions of the micro-mechanical beam at specific points along the beam. Such targeting or “pin-pointing” may increase the bending stiffness of the beam at the specific points with only a marginal influence to its torsional stiffness. Thus, the protective support structures may increase the robustness of the micro-mechanical beam and may permit their use under harsh and/or tough environmental conditions. The structures may also facilitate the production of moveable structures (such as, for example, mirrors with much higher robustness) as well as making mass application and/or higher yields feasible. 
         [0006]    The attachable structures may be applied in devices such as bar-code readers, leveling devices, scanners, display technology devices, and in particular, micro-mechanical mirrors. For example, the attachable support structures may provide an effective way to reduce the freedom of the in-plane movement of a micro-mechanical mirror that is suspended by one or more micro-mechanical beams. The attachable support structures may also provide enhanced protection for devices in a mobile configuration, such as, for example, an automotive application, where movement-induced vibration may be a major concern. 
         [0007]    An exemplary embodiment of the present invention is directed to providing an arrangement for use with a micro-mechanical beam, having a support structure configured to directly attach to the micro-mechanical beam to increase bending stiffness of the micro-mechanical beam without significantly influencing torsional stiffness. 
         [0008]    Another exemplary embodiment is directed to an arrangement in which the support structure is positioned at a point of a maximum bending of the micro-mechanical beam. 
         [0009]    Yet another exemplary embodiment is directed to an arrangement in which the support structure is constructed to reduce stiction. 
         [0010]    Still another exemplary embodiment is directed to an arrangement in which the support structure includes a rounded contact area. 
         [0011]    Yet another exemplary embodiment is directed to an arrangement in which the support structure includes a tapered end near a point of attachment with the micro-mechanical beam. 
         [0012]    Still another exemplary embodiment is directed to an arrangement in which the support structure is arranged at a point of maximum bending of the micro-mechanical beam and includes a rounded contact area and a tapered end near a point of attachment. 
         [0013]    Yet another exemplary embodiment is directed to an arrangement in which a shape of the support structure includes at least one of round, cubic, cylindrical, tubular, coil-shaped, quonset-shaped, prism-shaped, pyramid, obelisk, wedge, spherical, prolate spheroid, cone-shaped; catenoid, ellipsoid, paraboloid, conoid, disc-shaped, toroid, serpentine, helix, concave, and convex. 
         [0014]    Still another exemplary embodiment is directed to an arrangement having at one additional support structure. 
         [0015]    Yet another exemplary embodiment is directed to an arrangement in which the support structure and the at least one additional support structure are equal in at least one of length, size, and shape. 
         [0016]    Still another exemplary embodiment is directed to an arrangement in which the support structure and the at least one additional support structure are unequal in at least one of length, size, and shape. 
         [0017]    Yet another exemplary embodiment is directed to a device for use with a micro-mechanical beam having a protective structure to restrict a bending action of the micro-mechanical beam, and configured to directly attach to the micro-mechanical beam at specific points along the beam. 
         [0018]    Still another exemplary embodiment is directed to a device in which the protective structure includes at least two adjacent support structures arranged to touch each upon reaching a predetermined bending action of the micro-mechanical beam and prevent a further bending action of the micro-mechanical beam. 
         [0019]    Yet another exemplary embodiment is directed to a device in which the at least two adjacent support structures are positioned at points of most severe deflection of the micro-mechanical beam. 
         [0020]    Still another exemplary embodiment is directed to a device in which the protective structures are distributed uniformly with an even length along an axis of the micro-mechanical beam. 
         [0021]    Yet another exemplary embodiment is directed to an device in which the protective structures are distributed non-uniformly along an axis of the micro-mechanical beam. 
         [0022]    Still another exemplary embodiment is directed to a device in which the protective structures are distributed with a decreasing length along the axis of the micro-mechanical beam. 
         [0023]    Yet another exemplary embodiment is directed to a device in which the protective structures are distributed with an increasing length along the axis of the micro-mechanical beam. 
         [0024]    Still another exemplary embodiment is directed to a device in which the protective structure restricts the bending action in at least one of a variety of directions and all directions. 
         [0025]    Yet another exemplary embodiment is directed to an arrangement for use with a micro-mechanical mirror having a micro-mechanical beam attached to the micro-mechanical mirror and a support structure attached to the micro-mechanical beam to restrict a bending action of the micro-mechanical beam. 
         [0026]    Still another exemplary embodiment is directed to an arrangement having a micro-mechanical mirror plate, a micro-mechanical beam attached to the micro-mechanical mirror plate, and a support structure to restrict a bending action of the micro-mechanical mirror beam. 
         [0027]    Yet another exemplary embodiment is directed to an arrangement to protect a micro-mechanical mirror plate having a support structure configured to restrict an in-plane movement of the micro-mechanical mirror plate, and being directly attachable to a micro-mechanical beam that suspends the micro-mechanical mirror plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1   a  shows a micro-mechanical mirror arrangement. 
           [0029]      FIG. 1   b  shows a partial view of the micro-mechanical mirror arrangement of  FIG. 1   a  with the addition of a micro-mechanical mirror stop to limit the in-plane movement of the micro-mechanical mirror plate. 
           [0030]      FIG. 1   c  shows a partial view of micro-mechanical mirror arrangement and the additional micro-mechanical mirror stop of  FIG. 1   b  immediately after an applied shock. 
           [0031]      FIG. 2   a  shows a micro-mechanical beam arrangement to restrict an in-plane movement of a micro-mechanical mirror plate suspended by at least one micro-mechanical beam. 
           [0032]      FIG. 2   b  shows the micro-mechanical beam arrangement of  FIG. 2   a  in a deflective state under stress of an applied shock force, demonstrating how the micro-mechanical support structures may touch each other in case of a significant bending action and thereby limit the maximal bending action of the micro-mechanical beam. 
           [0033]      FIG. 2   c  shows the micro-mechanical beam arrangement of  FIG. 2   a  under the stress of an applied shock force demonstrating how the micro-mechanical support structures may touch in case of a twisting action, and thereby still limit the maximal bending action of the micro-mechanical beam. 
           [0034]      FIG. 3   a  shows an exemplary variation of the micro-mechanical support structures. 
           [0035]      FIG. 3   b  shows an additional exemplary variation of the micro-mechanical support structures. 
           [0036]      FIG. 3   c  shows a further additional exemplary variation of the micro-mechanical support structures. 
           [0037]      FIG. 4  shows an exemplary variation of the micro-mechanical support structures to reduce stiction. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]      FIG. 1   a  shows a configuration of a micro-mechanical mirror arrangement  100 . The micro-mechanical arrangement  100  includes a micro-mechanical mirror plate  101  suspended by two torsional micro-mechanical beams  102  and  103 . The micro-mechanical beams  102 ,  103  permit a certain “freedom of movement” of the micro-mechanical mirror plate  101 . In particular, the tension of the micro-mechanical beams  102 ,  103  restricts a movement of the micro-mechanical mirror plate  101  in a direction X along the axis of the micro-mechanical beams  102 ,  103 , and at the same time permits movement in a direction Y that is in-plane with the micro-mechanical mirror plate  101  (that is, perpendicular to the axis of the micro-mechanical beams  102 ,  103  and a direction Z that is vertical to the plane of the micro-mechanical mirror plate  101 ). 
         [0039]    To increase the freedom of movement of the micro-mechanical mirror plate  101 , the micro-mechanical beams  102 ,  103  may be extended lengthwise in the direction X along the axis of the micro-mechanical beams  102 ,  103  and/or their thickness may be reduced. However, the extended length or reduced thickness of the micro-mechanical beams  102 ,  103  may make them prone to breakage or may not adequately restrict a particular undesired movement of the micro-mechanical mirror plate  101 . 
         [0040]    To make the micro-mechanical beams  102 ,  103  more robust and/or to restrict a particular undesired movement of the micro-mechanical mirror plate  101 , the micro-mechanical beams  102 ,  103  may be shortened lengthwise and/or their thickness may be increased. However, such shortening and/or thickening of the micro-mechanical beams  102 ,  103  may restrict the overall freedom of movement of the micro-mechanical mirror plate  101 . Furthermore, such shortening and/or thickening may also pose significant challenges to their production. 
         [0041]      FIG. 1   b  shows a partial view of the micro-mechanical mirror arrangement  100  of  FIG. 1   a  with the addition of a micro-mechanical mirror stop  104  to limit the in-plane movement of the micro-mechanical mirror plate  101 . The micro-mechanical mirror stop  104  may be made out of, for example, the same material or film as the micro-mechanical mirror plate  101 . However, in case of an applied shock to the micro-mechanical mirror arrangement  100 , the micro-mechanical mirror stop  104  may not prevent the micro-mechanical mirror plate  101  from tilting downwards and “diving” beneath the micro-mechanical mirror stop  104 . 
         [0042]      FIG. 1   c  shows a partial view of micro-mechanical mirror arrangement  100  and the additional micro-mechanical mirror stop  104  of  FIG. 1   b  immediately after an applied shock. As a result of the shock, an end  101   a  of the micro-mechanical mirror plate  101  may be positioned beneath the micro-mechanical mirror stop  104 . Such a position of the end  101   a  may be undesirable or may result in potential damage the micro-mechanical mirror plate  101  and/or the micro-mechanical beam  103 . 
         [0043]      FIG. 2   a  shows a micro-mechanical beam arrangement  200  to restrict an in-plane movement of a micro-mechanical mirror plate  201  suspended by at least one micro-mechanical beam  202 . The micro-mechanical beam arrangement  200  includes one or more micro-mechanical support structures  205  attached directly to the micro-mechanical beam  202  that limit the bending action of the micro-mechanical beam  202 . Such support structures  205  may greatly increase the stiffness of the micro-mechanical beam  202  in a direction Y perpendicular to the axis of the micro-mechanical beam  202 , with only marginal influence to the torsional stiffness. 
         [0044]    Thus, for example, in case of a shock, the micro-mechanical mirror plate  201 , whose mass may be relatively high in comparison with the micro-mechanical beam  202 , may apply a force to the micro-mechanical beam  202  stressing it and causing it to bend resulting in an undesirable deflection of the micro-mechanical beam  202 . With the attachment of the micro-mechanical support structures  205 , the deflection of the micro-mechanical beam  202  may be limited as adjacent micro-mechanical support structures  205  touch each other and prevent further bending at points of the most severe deflection. Thus, the deflection caused by the applied shock may be spread more evenly. As a result, the micro-mechanical beam  202  may be able to absorb more energy and therefore withstand greater stresses. Thus, the addition of the micro-mechanical support structures  205  may enhance the maximal load and shock survival of the micro-mechanical beam  202 , as well as that of the micro-mechanical mirror plate  201 . 
         [0045]      FIG. 2   b  shows the micro-mechanical beam arrangement  200  of  FIG. 2   a  in a deflective state under stress of an applied shock force, demonstrating how the micro-mechanical support structures  205  may touch each other in case of a significant bending action and thereby limit the maximal bending action of the micro-mechanical beam  202 . In particular, if a deflection of the micro-mechanical beam  202  should occur, for example, in a direction Y that is in-plane with the micro-mechanical mirror plate  201  and perpendicular to the axis of the micro-mechanical beam  202 , the micro-mechanical support structures  205  prevent further bending beyond a certain limit at points P 1  and P 2  along the axis of the micro-mechanical beam  202 . Thus, the in-plane movement of the micro-mechanical mirror plate  201  may be limited and the required stress to break the micro-mechanical beam  202  may not be reached. 
         [0046]      FIG. 2   c  shows the micro-mechanical beam arrangement  200  of  FIG. 2   a  under the stress of an applied shock force demonstrating how the micro-mechanical support structures  205  may touch in case of a twisting action, and thereby still limit the maximal bending action of the micro-mechanical beam  202 . In particular, should a deflection of the micro-mechanical beam  202  induce, for example, a movement of the micro-mechanical mirror plate  201  in a rotational direction R about the axis of the micro-mechanical beam  202 , the micro-mechanical support structures  205  may still prevent bending beyond a certain limit at points P 1  and P 2  along the axis of the micro-mechanical beam  202 . Thus, the in-plane movement of the micro-mechanical mirror plate  201  may still be limited and the required stress to break the micro-mechanical beam  202  may not be reached. 
         [0047]    To achieve more precise control, the maximum bending action of the micro-mechanical beam  202  may be adjusted by adjusting the length of the micro-mechanical structures  205  and/or the gap between them. For instance, the stress and bending action of the micro-mechanical beam  202  may vary along its length. In particular, the highest stress may be found at the points of the highest bending, which may be found, for example, near points where the micro-mechanical beam  202  is attached to the micro-mechanical mirror plate  101 . Since the bending action may vary depending on the position along the micro-mechanical beam, not every position along the micro-mechanical beam may require equal protection (for example, the bending action in the middle of a double clamped beam may be lower). Thus, by reducing and/or abandoning micro-mechanical support structures  205  at points of low bending, the damping action may be targeted ad localized along the length of the micro-mechanical beam  202 . Additionally, the length and thickness of the micro-mechanical support structures may be varied along the length to localize the damping action. Such localization of the damping action may permit a “tailoring” of the movement of the attached micro-mechanical mirror plate  201 . 
         [0048]      FIGS. 3   a ,  3   b , and  3   c  show exemplary variations of the micro-mechanical support structures  205 . In  FIG. 3   a , the micro-mechanical support structures  305  are distributed uniformly with an even length along the axis of the micro-mechanical beam  302  thereby providing uniform protection along the axis of the micro-mechanical beam with to a horizontal in-plane bending action in direction Y. In  FIG. 3   b , the micro-mechanical support structures  305  are distributed with a decreasing length along the axis of the micro-mechanical beam  302 , starting from the micro-mechanical mirror plate  301  and extending lengthwise. In  FIG. 3   c , the micro-mechanical support structures  305  are distributed with an increasing length along the axis of the micro-mechanical beam  302  starting from the micro-mechanical mirror plate  301  and extending lengthwise. 
         [0049]      FIG. 4  shows an exemplary variation of the micro-mechanical support structures  405  to reduce “stiction” (the tendency of surfaces of the support structures to “stick together” due to, for example, electrostatic effects). The addition of the micro-mechanical support structures  405  may influence the natural spring constant of the beam spring  402 . To reduce such influences upon the natural spring constant, the micro-mechanical support structures  405  may be varied in shape and size. In particular, round contact areas  406  at points of contact between two micro-mechanical structures  405  and/or tapered ends  407  near their point of attachment with the beam spring may reduce effects such as stiction. 
         [0050]    Although depicted in rectangular/parallelepiped form, the support structures  405  may be any suitably appropriate shape, including, for example, round, cubic, cylindrical, tubular, coil-shaped, quonset-shaped, prism-shaped, pyramid, obelisk, wedge, spherical, prolate spheroid, cone-shaped, catenoid, ellipsoid, paraboloid, conoid, disc-shaped, toroid, serpentine, helix, concave, and convex. Hence, with such a multitude of structure types, the support structures may provide protections in a variety of directions (e.g., X and Z directions) and/or all directions (i.e., “wrap around” protection—up to 360 degrees protection or part thereof).