Abstract:
A MEMS (micro electro mechanical system) actuator with discretely controlled multiple motions comprises bottom layer, stepper plate, support, and motion plate. The multiple motion of the motion plate is generated by the electrostatically actuated stepper plates and geometrically predetermined supports. By introducing the MEMS actuator with discretely controlled multiple motions, simple motion control can be achieved by digital controlling and only single voltage is needed for motion control of the motion plate.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to micro-electro mechanical systems in general and more specifically motion control and generation for micro-electro mechanical systems (MEMS). 
       BACKGROUND OF THE INVENTION 
       [0002]    Motion plates may be used in various optical applications instead of, or in addition to, conventional optoelectronic devices. It is desirable to have capability to move the motion plates by rotation and translation with very fine control. 
         [0003]    Since the micro-electro mechanical systems (MEMS) were developed, many applications in MEMS have been developed and used. Micro actuator is the main part of the research and applications in MEMS field. Devices and application using MEMS actuators are developed and used in various fields such as optical communication, display, motion sensor, and medical devices. As the applications of MEMS actuators grow rapidly, the demand on controlling motion plate device increases. It is desirable to have the motion control of the MEMS actuator with many degrees of freedom and simple driving method. Usually, electrostatic, magnetic, piezo, and thermal actuations are widely used in the MEMS industry. 
         [0004]    A translational motion only MEMS actuator has been used for phase-only piston-style motion and deformable mirrors. These applications are mainly used for phase adaptive optics applications. A rotational motion of MEMS actuator is also developed for light modulation and MEMS device movements. Most of these motion plates have been controlled to have continuous displacements, which are determined at the equilibrium between electrostatic force and elastic force. 
         [0005]    As an example, U.S. Pat. No. 7,036,312 is a good example of thermally controlled MEMS actuator device. Two cantilever actuator by thermally controlled make motion of actuation. Also U.S. Pat. No. 6,914,710 shows an example of electrostatic comb actuators. Comb actuator is one of the most widely used electrostatic actuators. Capacitive force of two different plates with different voltages makes strong attraction force. The electro capacitive force is a source of the force of the electrostatic MEMS actuator. Also, U.S. Pat. No. 6,858,911 shows an example of electromagnetic MEMS actuator. The electromagnetic MEMS actuator comprises a magnetic material, and an electrically conductive coil about the magnetic coil. The coil and the magnetic core can be arranged to generate a magnetic field to move the actuation element. But these actuators have a complicated driving mechanism and control method. 
         [0006]    Therefore, the demand on the simple control of the MEMS actuator with higher degrees of freedom and precision has been increased in MEMS industry. The present invention is intended to provide a MEMS actuator device with multiple motions, variable degrees of freedom, low driving voltage, and simple activation mechanism. The MEMS actuator of the present invention can have one degree of freedom rotational motion, one degree of freedom translational motion, one degree of freedom rotational and one degree of freedom translational motion, two degrees of freedom rotational motion, and two degrees of freedom rotational motion and one degree of freedom translational motion, depending on its system configuration. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention addresses the problems of the prior art and provides a MEMS actuator with discretely controlled multiple motions having the fine and simple control of rotation and translation. 
         [0008]    The MEMS (micro electro mechanical system) actuator with discretely controlled multiple motions of the present invention comprises a bottom layer having control circuitry, at least one stepper plate, at least one support, wherein each support is geometrically coupled to the corresponding stepper plate to define motion, and a motion plate having pre-determined multiple motions supported by the stepper plates and the supports. 
         [0009]    The motions of the motion plate are pre-programmed by the supports and the stepper plates and each of the pre-programmed motions of the motion plate is provided by actuating a predetermined set of stepper plates. 
         [0010]    Each support in the present invention is geometrically coupled to the corresponding stepper plate to define motion and the motion plate has pre-determined multiple motions supported by the stepper plates and the supports; 
         [0011]    The control circuitry of the present invention is coupled with the stepper plate electrodes and selectively activates the stepper plate electrodes. The control circuitry is wire structure directly connected with the stepper plate electrodes to supply voltages. By selectively applying voltages to the stepper plate electrodes through the wire structures, the motion of the motion plate can be discretely controlled. 
         [0012]    The control circuitry can be an electrical addressing circuitry. Also the electrical addressing circuitry comprises a plurality of memory type cell forming a memory addressing array. The memory addressing array comprises SRAM circuits to activate the stepper plate electrodes. The memory addressing array comprises DRAM circuits to activate the stepper plate electrodes. 
         [0013]    The control circuitry comprises a MOS-type or CMOS-type circuitry on the bottom layer. By controlling the MOS-type or CMOS-type circuitry on the bottom layer, the stepper plate electrodes can be selectively activated thus the motion of the motion plate can have multiple motions. 
         [0014]    By proper configuration of the control circuitry, the control circuitry can be operated by digital voltage. Thus the motion of the motion plate can be controlled by the digital voltage. 
         [0015]    The control circuitry supplies discrete control voltage to the stepper plate electrodes. The discretely controlled voltage to the stepper plate electrodes can control the motion of the motion plate. 
         [0016]    Each stepper plate is configured to have pre-programmed rotations about multiple axes by activating predetermined sets of the stepper plate electrodes and each support is configured to define a motion of the motion plate when the stepper plate is actuated. 
         [0017]    The support is a motion plate bottom support located under the motion plate and each of the motion plate bottom supports is geometrically coupled to the stepper plate and one end is disposed on the bottom side of the motion plate and the other end is configured to contact the stepper plate when the stepper plate is actuated. 
         [0018]    The motion of the motion plate is defined by the contact points of the motion plate bottom support and the stepper plate top side. The support is a stepper plate top support located on the stepper plate. Each of the stepper plate top supports is geometrically coupled to the motion plate and one end is disposed on the top side of the stepper plate and the other end is configured to contact the motion plate bottom side when the stepper plate is actuated. The motion of the motion plate is defined by the contact points of the stepper plate top support and the motion plate bottom side. 
         [0019]    The support is a stepper plate bottom support located under the stepper plate and each of the stepper plate bottom supports is geometrically coupled to the bottom layer and one end is disposed on the bottom side of the stepper plate and the other end is configured to contact the bottom layer when the stepper plate is actuated. 
         [0020]    The inclination angle of the stepper plate is defined the contact points of the stepper plate bottom support and the bottom layer. The motion of the motion plate is defined by the contact points of the stepper plate and the motion plate and the inclination angle of the stepper plate. The contact points of the stepper plate and the motion plate are determined by the stepper plate top support. The contact points of the stepper plate and the motion plate are determined by the motion plate bottom support. 
         [0021]    The support is a bottom layer support located on the bottom layer. Each of the bottom layer supports is geometrically coupled to the stepper plate and one end is disposed on the top side of the bottom layer and the other end is configured to contact the bottom side of the stepper plate when the stepper plate is actuated. The inclination angle of the stepper plate is defined the contact points of the bottom layer support and the stepper plate. 
         [0022]    The motion of the motion plate is defined by the contact points of the stepper plate and the motion plate and the inclination angle of the stepper plate. The contact points of the stepper plate and the motion plate are determined by the stepper plate top support. The contact points of the stepper plate and the motion plate are determined by the motion plate bottom support. 
         [0023]    The support is a stepper plate inner support and the stepper plate inner support is disposed on the bottom layer and is configured to contact the bottom side of the stepper plate when the stepper plate is actuated. The inclination angle of the stepper plate is defined the contact points of the stepper plate and the stepper plate inner support. 
         [0024]    The motion of the motion plate is defined by the contact points of the stepper plate and the motion plate and the inclination angle of the stepper plate. The rotation of the stepper plate is pre-programmed by position of the stepper plate inner support. The rotation of the stepper plate is pre-programmed by height of the stepper plate inner support, wherein the stepper plate inner support has variation in height. 
         [0025]    The stepper plate has at least one stepper plate tip, configured to contact the bottom layer including landing structures for reducing the contact area of the actuated stepper plate with the bottom layer. 
         [0026]    The motion of the motion plate is defined by the height of the support. 
         [0027]    The motion plate can further comprise at least one motion plate electrode, disposed on the bottom layer, configured to pull the motion plate down toward the bottom layer to make contact between the motion plate and the actuated stepper plate. The stepper plate is actuated by electrostatic force induced by the stepper plate electrodes. 
         [0028]    The driving voltage of the motion plate is reduced by using multiple stepper plate electrodes to actuate the stepper plate. 
         [0029]    Each stepper plate has at least one landing structure, disposed on the bottom layer, configured to stop the rotation of the stepper plate by contacting the actuated stepper plate. 
         [0030]    The motion plate can have various degrees of freedom motions. The motion plate has one rotational degree of freedom motion. The motion plate has two rotational degrees of freedom motion. The motion plate has two translational degrees of freedom motion. The motion plate has one rotational degree of freedom motion and one translational degree of freedom motion. The motion plate has two rotational degrees of freedom motion and one translational degree of freedom motion. 
         [0031]    While the MEMS actuator with discretely controlled multiple motions of the present invention combined as an array, the array of the MEMS actuator with discretely controlled multiple motions comprises the motion plates with various degrees of freedom rotation or translation which are controlled independently. In order to do this, each motion plate must have capability to control object on the motion plate to a desired direction by controls of respective degrees of freedom rotation or translation. 
         [0032]    This MEMS actuator with discretely controlled multiple motions can be applied to the motion control of the micromirror device. The general principle, structure and methods for making the discrete motion control of MEMS device including micromirrors are disclosed in U.S. patent application Ser. No. 10/872,241 filed Jun. 18, 2004, U.S. patent application Ser. No. 11/072,597 filed Mar. 4, 2005, U.S. patent application Ser. No. 11/347,590 filed Feb. 4, 2006, U.S. patent application Ser. No. 11/369,797 filed Mar. 6, 2006, U.S. patent application Ser. No. 11/426,565 filed Jun. 26, 2006, U.S. patent application Ser. No. 11/463,875 filed Aug. 10, 2006, U.S. patent application Ser. No. 11/534,613 filed Sep. 22, 2006, U.S. patent application Ser. No. 11/534,620 filed Sep. 22, 2006, U.S. patent application Ser. No. 11/549,954 filed Oct. 16, 2006, U.S. patent application Ser. No. 11/609,882 filed Dec. 12, 2006, U.S. patent application Ser. No. 11/685,119 filed Mar. 12, 2007, U.S. patent application Ser. No. 11/693,698 filed Mar. 29, 2007, and U.S. patent application Ser. No. 11/742,510 filed Apr. 30, 2007, all of which are incorporated herein by references. 
         [0033]    While used as an array with micromirrors, the motion of the micromirrors can be controlled independently and the micromirror array can be built as an optical device such as a spatial light modulator and a Micromirror Array Lens. The general principle and methods for making the Micromirror Array Lens are disclosed in U.S. Pat. No. 6,970,284 issued Nov. 29, 2005 to Kim, U.S. Pat. No. 7,031,046 issued Apr. 18, 2006 to Kim, U.S. Pat. No. 6,934,072 issued Aug. 23, 2005 to Kim, U.S. Pat. No. 6,934,073 issued Aug. 23, 2005 to Kim, U.S. Pat. No. 7,161,729 issued Jan. 9, 2007, U.S. Pat. No. 6,999,226 issued Feb. 14, 2006 to Kim, U.S. Pat. No. 7,095,548 issued Aug. 22, 2006 to Cho, U.S. patent application Ser. No. 10/893,039 filed Jul. 16, 2004, U.S. patent application Ser. No. 10/983,353 filed Nov. 8, 2004, U.S. patent application Ser. No. 11/076,616 filed Mar. 10, 2005, U.S. patent application Ser. No. 11/426,565 filed Jun.  26 ,  2006 , and U.S. patent application Ser. No. 11/743,664 filed May 2, 2007, all of which are incorporated herein by references. 
         [0034]    The MEMS actuator with discretely controlled multiple motions of the present invention has advantages including: (1) the MEMS actuator provides multiple motions; (2) the MEMS actuator can be controlled in a low driving voltage; (3) simple motion control is achieved by applying digital control; (4) the MEMS actuator has a fine motion control of the motion plate using multiple supports and electrodes; (5) only single voltage is needed for driving the control circuitry; and (6) the motion plate is controlled discretely. 
         [0035]    Although the present invention is briefly summarized, the full understanding of the invention can be obtained by the following drawings, detailed description, and appended claims. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0036]    These and other features, aspects and advantages of the present invention will become better understood with reference to the accompanying drawings, wherein: 
           [0037]      FIG. 1   a - 1   c  shows schematic diagram of the MEMS actuator with discretely controlled multiple motions of the present invention; 
           [0038]      FIG. 2  is a two-dimensional cross-sectional schematic diagram showing the MEMS actuator of the present invention with discretely controlled multiple motions with motion plate; 
           [0039]      FIGS. 3   a - 3   c  show schematically how various types of supports can affect the motion of a motion plate; 
           [0040]      FIGS. 4   a - 4   b  are a three-dimensional schematic perspective diagram of the MEMS actuator of the present invention with discretely controlled multiple motions showing various types of supports and various shapes of stepper plates from different points of view; 
           [0041]      FIG. 5  is a schematic illustration of the MEMS actuator of the present invention showing how motion of the motion plate is controlled using a square shaped stepper plate and quadruple motion plate bottom supports; 
           [0042]      FIGS. 6   a - 6   c  are a schematic illustration of the MEMS actuator of the present invention showing how motion of the motion plate is controlled using an octagonal shaped stepper plate and eight motion plate bottom supports from different points of view; 
           [0043]      FIGS. 7   a - 7   b  are a schematic illustration of the MEMS actuator of the present invention having motion plate bottom supports with different heights from different points of view; 
           [0044]      FIGS. 8   a - 8   b  are a schematic illustration of the MEMS actuator of the present invention showing how motion of the motion plate is controlled using a hexagonal shaped stepper plate and six stepper plate top supports from different points of view; 
           [0045]      FIGS. 9   a - 9   b  show a variation of the configuration of the stepper plate top supports from different points of view. 
           [0046]      FIGS. 10   a - 10   b  show various configurations of the stepper plate inner support; 
           [0047]      FIGS. 11   a - 11   b  show a three-dimensional perspective view of the MEMS actuator of the present invention providing three degrees of freedom motion using motion plate bottom supports when the stepper plates are on and off; 
           [0048]      FIG. 12  shows a three-dimensional perspective view of the MEMS actuator of the present invention providing three degrees of freedom motion using motion plate bottom supports having variation in height; and 
           [0049]      FIG. 13  is a schematic illustration of an array of the MEMS actuator with motion plates of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]      FIG. 1   a - 1   c  shows schematic diagram of the MEMS actuator with discretely controlled multiple motions of the present invention.  FIG. 1   a  shows the simple illustration of the MEMS actuator with discretely controlled multiple motions of the present invention. A motion plate  12  is controlled to have discrete motions, which is controlled by stepper plates  13  and corresponding supports  14 . The motion plate  12  moves with an object  16  of regards. Since the object  16  is directly connected with the motion plate  12 , the control of the motion plate  12  is directly converted to the motion of the object  16 . 
         [0051]    The MEMS (micro electro mechanical system) actuator with discretely controlled multiple motions of the present invention comprises a bottom layer  11  having control circuitry, at least one stepper plate  13 , at least one support, wherein each support  14  is geometrically coupled to the corresponding stepper plate  13  to define motion, and a motion plate  12  having pre-determined multiple motions supported by the stepper plates  13  and the supports  14 . 
         [0052]    The motions of the motion plate  12  can be pre-programmed by the supports  14  and the stepper plates  13  and each of the pre-programmed motions of the motion plate  12  is provided by actuating a predetermined set of stepper plates  13 . Each support  14  in the present invention is geometrically coupled to the corresponding stepper plate  13  to define motion and the motion plate  12  has pre-determined multiple motions supported by the stepper plates  13  and the supports  14 . The stepper tip structure  15  is applied to reduce the stiction problem of the structures. 
         [0053]    The MEMS actuator of the present invention has simpler control system. Once the motion is defined and programmed in the motion plate structure, the control is just applying the on/off voltage for desired channel with respect to the desired motion. No feedback is required and the motion is reproducible regardless of the environment. Also multiple step-wise voltages can be applied to the desired channel for optimized motion and voltage. 
         [0054]    In  FIGS. 1   b - 1   c , the motion of the MEMS actuator is illustrated.  FIG. 1   b  shows the initial motion of the controlled object  16  and the motion plate  12 . The stepper plate  13  is initially aligned along with bottom layer  11 . In the  FIGS. 1   a - 1   c , the motion plate bottom supports  14  define the motion of the motion plate  12  and thus the object  16 . To see the clear motion difference, the motion grid lines  17  and the clock hand like indication arrows  18  are drawn with the structures. With the grid line  17 , the translation and the rotation of the motion plate  12  can easily be observed. In  FIG. 1   c , the stepper plates  13  are inclined with an angle and the supports  14  contact the stepper plate  13 . By the contact points of the supports  14  and the stepper plate  13 , the motion of the motion plate  12  is defined. And the object  16  has a motion, which can be defined and easily be seen with the grid lines  17  and clock hand like arrows  18 . 
         [0055]      FIG. 2  is a two-dimensional cross-sectional schematic diagram showing a MEMS actuator with discretely controlled multiple motions, according to the embodiments of the present invention. The MEMS actuator with discretely controlled multiple motions of this invention comprises a bottom layer  21  having control circuitry, a motion plate  22  having a top side and a bottom side, wherein the top side of the motion plate having a connection to a object of regards, at least one stepper plate  23  disposed between the motion plate  22  and the bottom layer  21 , wherein each stepper plate  23  has a plurality of stepper plate electrodes  24  configured to actuate the stepper plate  23 , and at least one support  25  ( 25 A˜ 25 E depending on its location), wherein each support  25  is geometrically coupled to the corresponding stepper plate  23 . Motions of the motion plate  22  are pre-programmed by the supports  25  and actuation of the stepper plates  23 . Each of the pre-programmed motions of the motion plate  22  is provided by actuating a predetermined set of stepper plates  23 . 
         [0056]    The stepper plate  23  is configured to have pre-programmed rotations about multiple axes by activating predetermined sets of the stepper plate electrodes  24  using the control circuitry. Motion of the motion plate  22  can be pre-programmed by the positions and geometries of these stepper plates  23 . The positions and geometries of the stepper plates  23  are selected during the design process of the MEMS actuator in order to provide the required motions of the motion plate  22  and fabricated accordingly. The stepper plates  23  are actuated by electrostatic force induced by the stepper plate electrodes  24 . 
         [0057]    The motion plate  22  can be configured to be pulled down to the actuated stepper plates to provide the required motion. In order to do this, the MEMS actuator of the present invention can further comprise at least one motion plate electrode  26 , disposed on the bottom layer  21 . The motion plate electrodes  26  are configured to pull the motion plate  22  down toward the bottom layer  21  to make the motion plate  22  contact the actuated stepper plates  23 . 
         [0058]    The MEMS actuator of the present invention can further comprise at least one landing structure  27  in order to reduce a possible stiction problem. The landing structure  27  is disposed on the bottom layer  21 , isolated electronically, and configured to stop the rotation of the stepper plate  23  by contacting the actuated stepper plate  23 . In addition, the stepper plate  23  can have at least one stepper plate tip  23 A, configured to contact the bottom layer  21  or landing structure  27  for reducing the contact area of the actuated stepper plate  23  with the bottom layer  21  or landing structure  27  to reduce the stiction problem. 
         [0059]    The motion range of the motion plate  22  can be increased by using various supports  25  that are geometrically coupled to the motion plate  22  directly or indirectly through the stepper plates  23 . The required motions of the motion plate  22  can be precisely pre-programmed by properly choosing the positions and geometries of these supports  25 . The positions and geometries of the supports are selected in the design process of the MEMS actuator in order to provide the required motions of the motion plate  22  and fabricated accordingly. 
         [0060]    The supports can be motion plate bottom supports  25 A located under the motion plate  22 . Each of the motion plate bottom supports  25 A is geometrically coupled to the stepper plate  23 , and configured to define motion of the motion plate  22 , wherein one end is disposed on the bottom side of the motion plate  22  and the other end is configured to contact the stepper plate  23  when the stepper plate  23  is actuated. 
         [0061]    The supports can be stepper plate inner supports  25 B. The stepper plate inner support  25 B is disposed on the bottom layer  21  and is configured to contact the stepper plate  23  to form a pivotal point for rotation of the stepper plate  23  when the stepper plate  23  is actuated. Also, the stepper plate inner support  25 B can be configured to support the stepper plate  23 . 
         [0062]    The supports can be stepper plate top supports  25 C. Each of the stepper plate top supports  25 C is configured to define motion of the motion plate  22 , wherein one end is disposed on the top side of the stepper plate  23  and the other end is configured to contact the bottom side of the motion plate  22  when the stepper plate  23  is actuated. 
         [0063]    The supports can be stepper plate bottom supports  25 D. Each of the stepper plate bottom supports  25 D is configured to define the rotation of the stepper plate  23 , wherein one end is disposed on the bottom side of the stepper plate  23  and the other end is configured to contact the bottom layer  21 , landing structures  27 , or the stepper plate inner support  25 B when the stepper plate  23  is actuated. 
         [0064]    The supports can be bottom layer supports  25 E. Each of the bottom layer supports  25 E is configured to define rotation of the stepper plate  23 , wherein one end is disposed on the bottom layer  21  and the other end is configured to contact the stepper plate  23  when the stepper plate  23  is actuated. 
         [0065]    Supports defining rotation of the stepper plate  23  such as stepper plate bottom support  25 D, stepper plate inner support  25 B, and bottom layer supports  25 E define the motion of the motion plate  22  indirectly while supports such as the motion plate bottom support  25 A and the stepper plate top supports  25 C define the motion of the motion plate directly. 
         [0066]    The MEMS actuator of the present invention can use one only type of supports  25  to pre-program the required motions of the motion plate  22 . Also, The MEMS actuator of the present invention can use various types of supports  25  together to pre-program the required motions of motion plate  22  with proper combinations. 
         [0067]    The MEMS actuator with discretely controlled multiple motions further comprises at least one stepper plate spring  28 , wherein each of the stepper plate spring  28  is configured to provide elastic restoring force to the stepper plate  23  and connect the stepper plate  23  with the bottom layer  21  or the stepper plate inner support  25 B. One end of the stepper plate spring  28  is attached to the stepper plate  23  or a stepper plate spring post (not shown) disposed on the stepper plate  23 . The other end of the stepper plate spring  28  can be attached to the bottom layer  21  or a stepper plate spring post  28 A disposed on the bottom layer  21 . Also, the other end of the stepper plate spring  28  can be attached to the stepper plate inner support  25 B or a stepper plate spring post (not shown) disposed on the stepper plate inner support  25 B. 
         [0068]    The MEMS actuator with discretely controlled multiple motions further comprises at least one motion plate spring  29 , wherein each of the motion plate springs  29  is configured to provide elastic restoring force to the motion plate  22  and connect the motion plate  22  with the bottom layer  21 . One end of the motion plate spring  29  is be attached to the bottom side of the motion plate  22  or a first motion plate spring post (not shown) disposed on the bottom side of the motion plate  22 . The other end of the motion plate spring  29  can be attached to the bottom layer  21  or a second motion plate spring post  29 A disposed on the bottom layer  21 . 
         [0069]      FIGS. 3   a - 3   c  show schematically how various types of supports can affect the motion of a motion plate  31 .  FIG. 3   a  shows a motion plate 
         [0070]    having motion plate bottom supports  32 A,  32 B. The stepper plates  33 A,  33 B are inclined by a pre-programmed angle when a driving voltage is applied to the stepper plate electrodes  34 A,  34 B. The motion plate bottom supports  32 A,  32 B are upheld by the actuated stepper plates  33 A,  33 B and the motion plate  31  has a motion defined by the contacting positions of the motion plate bottom support  32 A,  32 B with the stepper plate  33 A,  33 B. Motion plate electrodes  35 A can be used to pull down the motion plate  31  toward a bottom layer  35  in order to make the motion plate bottom supports  32 A,  32 B to be rested on the stepper plates  33 A,  33 B. The motion of the motion plate  31  is defined by the geometry of the MEMS actuator of the present invention including positions and heights of the motion plate bottom supports  32 A,  32 B. 
         [0071]      FIG. 3   b  shows stepper plates  33 A,  33 B having stepper plate top supports  36 A,  36 B. The stepper plates  33 A,  33 B are inclined by a pre-programmed angle when a driving voltage is applied to the stepper plate electrodes  34 A,  34 B. The stepper plate top supports  36 A,  36 B uphold the motion plate  31  and the motion plate  31  has a motion defined by the contacting positions of the motion plate  31  with the stepper plate top supports  36 A,  36 B. Motion plate electrodes  35 A can be used to pull down the motion plate  31  toward a bottom layer  35  in order to make the motion plate  31  to be rested on the stepper plate top supports  36 A,  36 B. The motion of the motion plate  31  is defined by the geometry of the MEMS actuator of the present invention including positions and heights of the stepper plate top supports  36 A,  36 B that uphold the motion plate  31 . 
         [0072]      FIG. 3   c  shows how the motion of a motion plate  31  is defined by stepper plate bottom supports  37 , bottom layer supports  38 , and stepper plate inner support  39 A,  39 B. A mechanical stop is applied to the MEMS actuator of the present invention to determine the amounts of the rotational angle of the stepper plate  33 A,  33 B. In this example, one stepper plate  33 A has the stepper plate bottom supports  37  while the other stepper plate  33 B has the bottom layer supports  38 . The amounts of the rotation angles of the stepper plates  33 A,  33 B are determined by positions and heights of the stepper plate bottom supports  37 , the bottom layer supports  38 , and the stepper plate inner supports  39 A,  39 B or even the existence thereof. The actuated stepper plates  33 A,  33 B uphold the motion plate  31  and determine the motion of the motion plate  31 . These supports limit or extend the rotation of the stepper plates  33 A,  33 B to provide the required motions of the motion plate  31 . 
         [0073]    The motion of the motion plate  31  can be defined by various combinations of these supports including motion plate bottom supports  32 , stepper plate top supports  36 , stepper plate bottom supports  37 , bottom layer supports  38 , and stepper plate inner supports  39 . Any combination of these supports can be used to pre-program the required motions of the motion plate  31  even though  FIGS. 3   a ,  3   b , and  3   c  don&#39;t show all cases. Also, the positions and heights of these supports are chosen in the design process to provide the required motions of the motion plate  31 , which allows the precise motion generation and control of the motion plate  31 . 
         [0074]      FIGS. 4   a - 4   b  are three-dimensional schematic perspective diagrams of the MEMS actuator of the present invention showing various types of supports and various shapes of stepper plates. The MEMS actuator of the present invention shown in  FIGS. 4  is used for only illustrative purpose in order to help the understanding of this invention. In practical use, each stepper plate can have the same configuration for simpler fabrication and easier operation as well as various configurations for precise motion pre-programming. 
         [0075]    The MEMS actuator of the present invention in  FIG. 4   a  comprises a bottom layer  41 , a motion plate  42 , and at least one stepper plate  43 A,  43 B,  43 C,  43 D. Stepper plates  43 A,  43 B,  43 C,  43 D has corresponding stepper plate electrodes  44 A,  44 B,  44 C,  44 D and corresponding supports, respectively. The stepper plate  43 A,  43 B has motion plate bottom supports  45 A,  45 B as the support structures, respectively. The stepper plate  43 C,  43 D has stepper plate top supports  45 C,  45 D as the corresponding supports, respectively. Motion plate springs  46  connect the bottom layer  41  with the motion plate  42 , wherein one end is attached to a motion plate spring post  46 A disposed on the bottom layer  41 , and the other end is attached to a motion plate spring post  46 B disposed on the bottom side of the motion plate  42 . Stepper plate springs connect the corresponding stepper plates  43  with the bottom layer  41  or corresponding stepper plate inner supports, respectively. The stepper plates  43 A,  43 D have the stepper plate springs (not shown) under the bottom side of the stepper plates  43 A,  43 D. The stepper plates  43 B has the stepper plate spring  47 B in the same level as the stepper plate  43 C and the stepper plates  43 C has the stepper plate spring  47 C above the top side of the stepper plate  43 B. Also, stepper plates  43 A,  43 B,  43 C,  43 D have stepper plate tips  48 A,  48 B,  48 C,  48 D to reduce the contact area with the bottom layer  41 . Each actuated stepper plate has a contact point that determines the motion of the motion plate. The contact points determining the motion of the motion plate are indicated as asterisk (*).  FIG. 4   b  shows the MEMS actuator structures of  FIG. 4   a  viewed from the different point of view, wherein the configurations of some elements are viewed better. In this view, the configurations of the motion plate bottom supports  45 A,  45 B and the stepper plate top supports  45 C,  45 D can be observed clearly. The motion plate bottom supports  45 A,  45 B are attached to the bottom side of the motion plate  42  while the stepper plate top supports  45 C,  45 D are attached to the top side of the corresponding stepper plate  43 C,  43 D. Also, the configuration of the motion plate spring post  46 A on the bottom layer  41  and the motion plate spring post  46 B on the bottom side of the motion plate  42  can be observed clearly. The first motion plate spring post  46 A is attached on the bottom layer  41  while the second motion plate spring post  46 B is attached on the bottom side of the motion plate  42 . Also,  FIG. 4   b  shows that some stepper plates can be configured to have multiple contact points with the bottom layer  41  when the stepper plates are actuated, which provides the stability of the stepper plate rotation. For example, the stepper plate  43 A is configured to have two contact points with the bottom layer  41  by making two stepper plate tips contact the bottom layer  41  for each rotation of the stepper plate  43 A. In this case, two stepper plate tips  49 A,  49 B contact the bottom layer  41 . The detail description of each stepper plate and motion generation shown in  FIG. 4   a  is further described in  FIGS. 5 ,  6 ,  7 , and  8 . 
         [0076]      FIG. 5  is a schematic illustration of the MEMS actuator showing how motion of a motion plate is controlled using a square shaped stepper plate  51  and quadruple motion plate bottom supports for providing multiple motions. The square shaped stepper plate  51  has quadruple motion plate bottom supports  52 A,  52 B,  52 C,  52 D disposed on the bottom side of the motion plate  56  and quadruple stepper plate electrodes  53  corresponding to the motion plate motions. The stepper plate  51  is configured to have at least four pre-programmed rotations by activating predetermined sets of stepper plate electrodes  53 . When a predetermined set of stepper plate electrodes  53  are activated, the stepper plate  51  is actuated to have a pre-programmed rotation. Then, the actuated stepper plate  51  is rotated and snapped down to the direction of the activated stepper plate electrodes  53 . At least one stepper plate tip  54  of the rotated stepper plate  51  contacts the bottom layer  55  or a landing structure and the top side of the stepper plate  51  contacts one of the motion plate bottom supports  52 A,  52 B,  52 C,  52 D. The contact point between the stepper plate  51  and the contacted motion plate bottom support  52 A is indicated as asterisk. The motion of the motion plate  56  depends on the position and height of the contacted motion plate bottom support  52 A. In this example, the stepper plate spring (not shown) connecting the stepper plate  51  with the bottom layer  55  or a stepper plate inner support is disposed under the stepper plate  51 . The positions and the heights of the motion plate bottom supports  52 A,  52 B,  52 C,  52 D are determined to provide the required motions of the motion plate  56  during design process and fabrication process of the motion plate device. To have larger electrostatic force or lower driving voltage, electric bias can be applied to two or more stepper plate electrodes  53  at the same time. Although this example shows the case using the motion plate bottom supports  52 A,  52 B,  52 C,  52 D, the motion of the motion plate  56  can be pre-programmed by using various combinations of motion plate bottom supports, stepper plate top supports, stepper plate bottom supports, stepper plate inner supports, and bottom layer supports. 
         [0077]      FIGS. 6   a - 6   c  are a schematic illustration of the MEMS actuator of the present invention from the different points of view showing how the motion of a motion plate  66  is controlled using an octagonal shaped stepper plate and eight motion plate bottom supports  62  for providing multiple motions of the motion plate.  FIGS. 6   a ,  6   b ,  6   c  show the portion of the DCM viewed from the different points of view (top, side, and bottom). The octagonal shaped stepper plate  61  has eight motion plate bottom supports  62  disposed on the bottom side of the motion plate and eight stepper plate electrodes  63 . The stepper plate  61  is configured to have at least eight pre-programmed rotations by activating predetermined sets of stepper plate electrodes  63 . When a predetermined set of stepper plate electrodes  63  are activated, the stepper plate  61  is actuated to have a pre-programmed rotation. Then, the actuated stepper plate  61  is rotated and snapped down to the direction of the activated stepper plate electrodes  63 . The stepper plate tip  64  of the actuated stepper plate  61  contacts the bottom layer  65  or a landing structure and the top side of the stepper plate  61  contacts one of the motion plate bottom supports  62 . The contact point between the stepper plate  61  and the contacted motion plate bottom support  62  is indicated as asterisk. Motion of the motion plate  66  depends on the position and height of the contacted motion plate bottom support  62 . The positions and the heights of the motion plate bottom supports  62  are determined to provide the required motions of the motion plate in the design process and fabricated during making process of the motion plate device. Unlike the case in the  FIG. 5 , wherein the stepper plate spring is disposed under the bottom side of the stepper plate, the stepper plate spring  67  of this example is disposed on the same level as that of the stepper plate  61  as shown in  FIGS. 6 , which can yield a simpler fabrication process. In this example, the MEMS actuator works in the same manner as the case in quadruple motion plate bottom supports in  FIG. 5 , but provides more number of motions and finer motion control of the motion plate  66 . In  FIG. 6   b , the configuration of the motion plate bottom supports  62  can be viewed better. The motion plate bottom supports  62  are attached to the bottom side of the motion plate  66  and the actuated stepper plate  61  is configured to contact one of the motion plate bottom supports  62 . In this case, the actuated stepper plate  61  contacts the motion plate bottom support  62 . 
         [0078]    While the motion plate bottom supports shown in  FIGS. 6  have the same height, wherein  FIG. 6   c  provides a clear view for observing the height of the motion plate bottom supports, the motion plate bottom supports can have variation in height as shown in  FIGS. 7   a - 7   b .  FIGS. 7   a  and  7   b  are schematic illustrations of the MEMS actuator of the present invention having motion plate bottom supports with different heights, viewed in two different directions. The MEMS actuator of the present invention is controlled using an octagonal shaped stepper plate  71  and eight motion plate bottom supports  72  having different heights for providing multiple motions of the motion plate  73 . The stepper plate  71  has eight motion plate bottom supports  72  disposed on the bottom side of the motion plate  73  and eight stepper plate electrodes  74 . The stepper plate  71  is configured to have at least eight pre-programmed rotations by activating predetermined sets of stepper plate electrodes  74 . When a predetermined set of stepper plate electrodes  74  are activated, the stepper plate  71  is actuated to have a pre-programmed rotation. Then, the actuated stepper plate  71  is rotated and snapped down to the direction of the activated stepper plate electrodes  74 . The stepper plate tip  75  of the actuated stepper plate  71  contacts the bottom layer  76  or a landing structure and the top side of the stepper plate  71  contacts one of the motion plate bottom supports  72 . The contact point between the stepper plate  71  and the contacted motion plate bottom support  72  is indicated as asterisk. The motion of the motion plate  73  depends on the position and height of the contacted motion plate bottom support  72 . The positions and the heights of the motion plate bottom supports  72  are determined to provide the required motions of the motion plate  73  in the design process and fabricated during making process of the motion plate device. By using the motion plate bottom supports  72  having variation in height, the motion of the motion plate  73  can be precisely pre-programmed to provide the required motions of the motion plate  73 . As a result, the motion control accuracy of the DCM can increase. Also, the motion range of the motion plate can be increased. 
         [0079]      FIGS. 7  also show an exemplary configuration of a stepper plate spring. The stepper plate  71  has the stepper plate spring  77  in the same level as the stepper plate  71 . The stepper plate spring  77  is configured to provide elastic restoring force to the stepper plate  71  and connect the stepper plate  71  with the bottom layer  76  or the stepper plate inner support (not shown). One end of the stepper plate spring  77  is attached to the stepper plate  71  or a stepper plate spring post (not shown) disposed on the stepper plate  71 . The other end of the stepper plate spring  77  can be attached to the bottom layer  76  or a stepper plate spring post  78  disposed on the bottom layer  76 . Also, the other end of the stepper plate spring  77  can be attached to the stepper plate inner support or a stepper plate spring post disposed on the stepper plate inner support. 
         [0080]      FIGS. 8   a - 8   b  are a schematic illustration of the MEMS actuator of the present invention showing how the motion of a motion plate is controlled using a hexagonal shaped stepper plate and six stepper plate top supports for providing multiple motions of the motion plate. The hexagonal shaped stepper plate  81  has six stepper plate top supports  82  disposed on the top side of the stepper plate  81  and six stepper plate electrodes  83 . The stepper plate  81  is configured to have at least six pre-programmed rotations by activating predetermined sets of stepper plate electrodes  83 . When a predetermined set of stepper plate electrodes  83  are activated, the stepper plate  81  is actuated to have a pre-programmed rotation. Then, the actuated stepper plate  81  is rotated and snapped down to the direction of the activated stepper plate electrodes  83 . The stepper plate tip  84  of the actuated stepper plate  81  contacts the bottom layer  89  or a landing structure and one of the stepper plate top supports  82  disposed on the top side of the stepper plate  81  contacts the bottom side of the motion plate  85 . The contact point between the motion plate  85  and the contacted stepper plate top support  82  is indicated as asterisk. The motion of the motion plate  85  depends on the position and height of the contacted stepper plate top support  82 . The positions and the heights of the stepper plate top supports  82  are determined to provide the required motions of the motion plate  85  during the design process and fabrication process of the motion plate device.  FIG. 8   a  shows another example of the arrangement of the stepper plate spring. In this example, the stepper plate spring  86  is disposed above the top side of the stepper plate  81 , wherein one end is attached to a first stepper plate spring post  87  disposed on the top side of the stepper plate  81  and the other end is attached to the motion plate spring post  46 A as shown in  FIGS. 4 . 
         [0081]      FIG. 8   b  also shows another exemplary configuration of a stepper plate inner support. The stepper plate  81  can be supported by a flexible structure such as stepper plate springs  86  and suspended over the stepper plate inner support  88  before the stepper plate  81  is actuated. When the stepper plate  81  is actuated, the stepper plate inner support  88  contacts the actuated stepper plate  81  to form a pivotal point for rotation of the actuated stepper plate  81 . The rotation of the actuated stepper plate  81  is pre-programmed by position and height of the stepper plate inner support  88 . The positions and geometries of the stepper plate inner supports  88  are selected in the design process of the MEMS actuator in order to provide the required motions of the motion plate  85  and fabricated accordingly. 
         [0082]      FIGS. 9   a - 9   b  show a variation of the configuration of the stepper plate top supports from the different points of view. In stead of using individually separated stepper plate top supports, the same function can be accomplished by using one bodied stepper plate top support structure. For example, the six stepper plate top supports  82  in  FIGS. 8  can be replaced with one bodied stepper plate top support structure  91  in  FIGS. 9 . The bodied stepper plate top support structure  91  is configured to be able to contact the motion plate  92  at six different positions. Each position contacted by the motion plate  92  can be configured to have variation in height. The contact point between the motion plate  92  and the one bodied stepper top support structure  91  is indicated as asterisk. The concept of the one bodied structure can be applied to other types of supports including motion plate bottom supports, stepper plate bottom supports, and bottom layer supports. The motion plate device can be ruggedized by using these one bodied structures instead of individually separated supports. 
         [0083]      FIGS. 9   a - 9   b  also show another exemplary configuration of stepper plate spring. The stepper plate  93  has the stepper plate spring  94  disposed under the stepper plate  93 . The stepper plate spring  94  is configured to provide elastic restoring force to the stepper plate  93  and connect the stepper plate  93  with the bottom layer  95  or the stepper plate inner support (not shown). In this example, one end of the stepper plate spring  94  is attached to a stepper plate spring post  96  disposed on the bottom side of the stepper plate  93 . The other end of the stepper plate spring  94  is attached to a stepper plate spring post  97  disposed on the bottom layer  95 . 
         [0084]      FIGS. 10   a - 10   b  show various configurations of stepper plate inner supports. The stepper plate  101 A can be supported by a flexible structure such as stepper plate springs  102  and suspended over the stepper plate inner support  103  before the stepper plate  101 A is actuated as shown in  FIG. 10   a . When the stepper plate  101 A is actuated, the stepper plate inner support  103  contacts the actuated stepper plate  10 B to form a pivotal point  104  for rotation of the actuated stepper plate  101 B. The rotation of the actuated stepper plate  101 B is pre-programmed by position and height of the stepper plate inner support  103 . The positions and geometries of the stepper plate inner supports are selected during the design process of the MEMS actuator in order to provide the required motions of the motion plate  105  and fabricated accordingly. On the other hand, the stepper plate  101 A can be supported by the stepper plate inner support  103  regardless of existence of the flexible structures as shown in  FIG. 10   b . In this case, the stepper plate  101 A is supported by the stepper plate inner support  103  before the stepper plate  101 A is actuated. When the stepper plate  101 A is actuated, the actuated stepper plate  10 B rotates about a pivotal point  104  of the stepper plate inner support  103 . The rotation of the actuated stepper plate  101 B is pre-programmed by position and geometry of the stepper plate inner support  103 , which is selected during the design process of the MEMS actuator in order to provide the required motion of the motion plate  105  and fabricated accordingly. 
         [0085]      FIGS. 11   a - 11   b  show a three-dimensional perspective view of a MEMS actuator of the present invention providing three degrees of freedom motion using motion plate bottom supports. The motion of the motion plate  111  is provided with two degrees of freedom rotation  112 ,  113  and one degree of freedom translation  114  as shown in  FIG. 11   a . To provide these three degrees of freedom motion, the MEMS actuator of the present invention preferably actuates at least three stepper plates  115  for each motion as shown in  FIG. 11   b . In this case, the motion plate  111  can have a stable motion because the motion plate  111  is supported by at least three points. Each stepper plate  115  has pre-programmed rotations determined by the positions and heights of the corresponding motion plate bottom supports  116 . The contact points between the stepper plates  115  and the contacted motion plate bottom supports  116  are indicated as asterisk. These contact points of the three stepper plates  115  with the three motion plate bottom supports  116  make a plane for the motion plate  111  representing a motion of the motion plate  111 . 
         [0086]      FIG. 12  shows a three-dimensional perspective view of the MEMS actuator of the present invention providing three degrees of freedom motion using motion plate bottom supports having variation in height. Each stepper plate  121  has pre-programmed rotations determined by the positions and heights of the corresponding motion plate bottom supports  122 , wherein the motion plate bottom supports  122  can have variation in height. The contact points between the stepper plates  121  and the contacted motion plate bottom supports  122  are indicated as asterisk. These contact points of the three stepper plates  121  with the three motion plate bottom supports  122  make a plane for the motion plate  123  representing a motion of the motion plate  123 . By introducing the motion plate bottom supports  122  and allowing the motion plate bottom supports  122  to have variation in height, the motion of the motion plate  123  can be precisely pre-programmed and the motion range of the motion plate  123  can be increased. 
         [0087]      FIG. 13  is a schematic illustration of an array of the MEMS actuator with motions plates of the present invention. As an illustrative purpose, a simple two by two motion plate  131  array is shown, wherein motion of the motion plate  132  is defined by the motion plate bottom supports  133 . In practice, the size of the two-dimensional array of the motion plates and the type of the supports defining the motion of the motion plate  132  can be varied according to a considered application. Each motion plate  132  in the array of the motion plates is independently controlled to form desired motion of the MEMS array. The control circuitry can be constructed by using known semiconductor microelectronics technologies such as MOS or CMOS to control the independent motion of the MEMS array. 
         [0088]    If the motion plate is built as a mirror for reflecting light, the array of the MEMS actuator with motion plates can be used as an arrayed spatial light modulator. The motion plates  132  in array of the MEMS actuator have independently controlled motions to make an optical phase modulator. The one translational degree of freedom motion of the MEMS actuator  131  with motion plate is controlled to retract or elevate the motion plate  132  to remove the phase aberration of an optical system. 
         [0089]    The motion plates  132  in array of the MEMS actuator with motion plates have independently controlled motions to form a spatial light modulator. The one translational degree of freedom motion of the motion plate  132  with motion plate is controlled to retract or elevate the motion plate  132  to remove the phase aberration of an optical system. The one or two rotational degrees of freedom motion of the motion plate  132  with motion plate is controlled to control light intensity and/or to scan a field of regard. By using both rotational degree of freedom motion and translational degree of freedom motion of the motion plate  132 , a fine spatial light modulator can be provided. 
         [0090]    As a special example of the arrayed motion plates, Micromirror Array Lens is a good example. The general properties of the Micromirror Array Lens are disclosed in U.S. Pat. No. 7,057,826 issued Jun. 6, 2006 to Cho, U.S. Pat. No. 7,173,653 issued Feb. 06, 2007, U.S. Pat. No. 7,215,882 issued May 8, 2007 to Cho, U.S. patent application Ser. No. 10/979,568 filed Nov. 2, 2004, U.S. patent application Ser. No. 11/218,814 filed Sep. 2, 2005, U.S. patent application Ser. No. 11/359,121 filed Feb. 21, 2006, U.S. patent application Ser. No. 11/382,273 filed May 9, 2006, and U.S. patent application Ser. No. 11/429,034 filed May 5, 2006, and its application are disclosed in U.S. Pat. No. 7,077,523 issued Jul. 18, 2006 to Seo, U.S. Pat. No. 7,068,416 issued Jun. 27, 2006 to Gim, U.S. patent application Ser. No. 10/914,474 filed Aug. 9, 2004, U.S. patent application Ser. No. 10/934,133 filed Sep. 3, 2004, U.S. patent application Ser. No. 10/979,619 filed Nov. 2, 2004, U.S. patent application Ser. No. 10/979,624 filed Nov. 2, 2004, U.S. patent application Ser. No. 11/076,688 filed Mar. 10, 2005, U.S. patent application Ser. No. 11/208,114 filed Aug. 19, 2005, U.S. patent application Ser. No. 11/208,115 filed Aug. 19, 2005, U.S. patent application Ser. No. 11/382,707 filed May 11, 2006, U.S. patent application Ser. No. 11/419,480 filed May 19, 2006, and U.S. patent application Ser. No. 11/423,333 filed Jun. 9, 2006, all of which are incorporated herein by references. 
         [0091]    While the invention has been shown and described with reference to different embodiments thereof, it will be appreciated by those skills in the art that variations in form, detail, compositions and operation may be made without departing from the spirit and scope of the present invention as defined by the accompanying claims.