Abstract:
An array of movable MEMS mirror devices is provided being electromagnetically actuated in one axis and using an additional set of coils, or a single coil, positioned off of the main axis of rotation to achieve a second axis of rotation while allowing for a very high linear mirror fill factor (&gt;80%). This second set of coils, or second electrically wired coil, is capable of generating the necessary torque about an axis that is perpendicular to the major axis of rotation. A second embodiment is provided using electromagnetic actuation in one axis of rotation, which typically has larger rotation angles than the second axis, and electrostatic actuation in the second axis of rotation. Electrostatic pads can be used to sense rotation. When staggering adjacent pixels a center array of mirrors with no coils or electrodes provides increased radius of curvature and reducing undesirable cross-talk between adjacent mirror devices.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to microelectromechanical (MEMS) devices and, more particularly, to MEMS devices having movable mirrors used, e.g., in optical switches, scanners, projectors, etc. 
     BACKGROUND OF THE INVENTION 
     Optical switches may be used for routing optical signals in fiber optic networks. The switches may selectively transmit light signals from a set of input fibers to a set of output fibers. The switches may include at least one array of movable mirrors or reflectors that can be selectively actuated to deflect light signals to particular output fibers. The movable mirrors can be actuated or controlled in a variety of ways including electromagnetic actuation, electrostatic actuation, piezoelectric actuation, or thermal bimorph. Fabrication of the mirror arrays has been attempted using MEMS technology, in which silicon processing and related techniques common to the semiconductor industry are used to form microelectromechanical devices. 
     In many applications for optical micromirrors, it is desirable to build an array of mirrors with both a high fill factor and control of two axes of rotation. Advantages of increased linear mirror fill factor include improved channel shape in wavelength division multiplexing systems and reduced optical loss. Advantages of having two axes of rotation over only one axis include the ability to more ably move the mirror in different directions, for example to steer an optical beam to hit or avoid a particular optical fiber. 
     For purposes of the instant invention, linear fill-factor as a term of art is defined as the size of the mirror in one direction divided by the pitch of the mirror array in the same direction. 
     One technique known in the prior art for achieving two axes of rotation has a mirror with a gimbals structure. This solution however, generally limits the fill factor achievable due to the area taken up by the gimbals. 
     A need exists for building an array of mirrors achieving both a high fill factor and control of two axes of rotation. 
     A need exists for obtaining fill factors in excess of 80%. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is a mirror device for obtaining dual axis rotation including a first means for electromagnetic actuation about a first axis; and a second means for actuation about a second axis where the first and second means for actuation do not utilize a gimbal structure. The first means for electromagnetic actuation utilizes at least one first coil. In another aspect of the invention, the second means for actuation is electromagnetic actuation utilizing at least one second coil. In another aspect of the invention, the at least one first coil and the at least one second coil can be positioned anywhere relative to each other on any side of the first and second axes. And in another aspect of the invention, the at least one first means coil is positioned only on one side of the first axis. Additionally, the at least one second means coil is positioned on the same side of the first axis as the at least one first means coil. And in another aspect of the invention, only the at least one second coil is present. 
     In yet another aspect of the invention, at least one permanent magnet provides a magnetic field to actuate the coils. Yet still another aspect of the invention includes an array formed of mirror devices with the first and second means for electromagnetic actuation providing a linear fill factor greater than 80%. Further aspects include an array of magnets of alternating polarity arranged to provide a magnetic field for the array of mirror devices and an array of center mirrors of the mirror device array having no coils. 
     In another aspect of the invention, the second means for actuation is electrostatic actuation utilizing at least one electrode. In yet another aspect of the invention, the at least one first coil and the at least one electrode can be positioned anywhere relative to each other on either side of the first and second axes. In a different aspect, the at least one electrode is positioned only on one side of the first axis. Additionally, the at least one coil is positioned on the same side of the first axis as the at least one electrode. And in another aspect of the invention, the at least one electrode is positioned only on one side of the second axis. Further aspects include the second means for electrostatic actuation utilizing a common ground plane, an interposer or at least one patterned electrode. Still further aspects include at least one permanent magnet providing a magnetic field to actuate the coils. In other aspects, an array formed of the mirror devices with the first and second means for actuation provides a linear fill factor greater than 80% and an array of magnets of alternating polarity is arranged to provide a magnetic field for the array of the mirror devices and wherein an array of center mirrors of said mirror device array includes no coils or electrodes. 
     In yet another aspect of the invention, the mirror device has a double paddle structure. And in still further aspects, the at least one electrode is used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for second axis rotation, or a plurality of electrodes on an interposer are used to measure differential capacitance for second axis rotation. 
     In another aspect of the present invention, a mirror device for obtaining dual axis rotation includes a first means for electromagnetic actuation about a first axis and a second means, coupled to the first axis, for electrostatic actuation about a second axis. In further aspects, the first means for electromagnetic actuation utilizes at least one coil and at least one permanent magnet provides a magnetic field to actuate the at least one coil. Other aspects include, the second means for electrostatic actuation utilizes at least one electrode, a common ground plane, an interposer, and/or at least one patterned electrode. Still further aspects include an array of devices with the first means for electromagnetic actuation and the second means for electrostatic actuation allowing for a linear fill factor greater than 80% and wherein an array of magnets of alternating polarity are arranged to provide a magnetic field for the mirror device array. In another aspect, an array of center mirrors of the mirror device array has no coils or electrodes. In yet another aspect of the invention, this mirror device has a double paddle structure. In still further aspects of the invention, the at least one electrode is used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for second axis rotation, or a plurality of electrodes on the interposer are used to measure differential capacitance for second axis rotation. 
     In still yet another aspect of the invention, an array of MEMS devices, where each device includes a mirror with a reflective surface having no gimbal support, at least one first coil for causing selective movement of the mirror about a first axis in the presence of a magnetic field, and means for causing selective movement of the mirror about a second axis. Further aspects include the means for causing selective movement utilizing at least one second coil in the presence of a magnetic field, the at least one first coil positioned in any position on each side of the first axis, the at least one first coil positioned only on one side of the first axis, the at least one second coil positioned in any position on each side of the second axis, the at least one first and second coils are superposed on the mirror, and/or the at least one first and second coils are not superposed on the mirror. Still further aspects include the array of devices allowing a linear fill factor greater than 80%, an array of magnets of alternating polarity arranged to provide the magnetic field for the array, and/or a center mirror array having no coils. In still further aspects of the invention, the second means for causing selective movement utilizes at least one electrode and the at least one coil and the at least one electrode can be in any position relative to each other on either side of the first and second axes. Also the at least one electrode may be positioned only on one side of the first axis, on one side of the second axis, and/or the at least one coil is positioned on the same said of the first axis as the at least one electrode. Additionally, the means for causing selective movement may utilize a common ground plane, an interposer, and/or at least one patterned electrode. Still further aspects include the array of devices allowing a linear fill factor greater than 80%, an array of magnets of alternating polarity arranged to provide the magnetic field for the array, and/or a center mirror array having no coils or electrodes. Further aspects include the at least one electrode may be used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for the second axis movement. Another aspect of the invention is that the mirror device has a double paddle structure. 
     In a further aspect of the present invention, an array of electromagnetically actuated MEMS devices is provided wherein each device includes a mirror with a reflective surface having no gimbal structure support, and at least one minor axis coil for causing selective movement of the mirror about the minor axis in the presence of a magnetic field. In still further aspects of the invention the minor axis coil produces dual axis rotation of the mirror and the array of mirror devices allows a linear fill factor greater than 80%. 
     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as described in the written description and claims hereof, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed. 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s) of the invention, and together with the description serve to explain the principles and operation of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This invention is further illustrated with reference to the following drawings in which: 
     FIG. 1 is a top view of a MEMS mirror pixel with coils for rotation about a single axis. 
     FIG. 2 is a top view of a gimbals structure for two-axis rotation. 
     FIG. 3 is a top view of a MEMS mirror pixel with coils for rotation about two axes in accordance with a preferred embodiment of the present invention. 
     FIG. 4 is a top view of FIG. 3 showing major axis coils in accordance with a preferred embodiment of the present invention. 
     FIG. 5 is a top view of FIG. 3 showing minor axis coils in accordance with a preferred embodiment of the present invention. 
     FIG. 6 is a top view of FIG. 3 showing major axis coils on one side of the pixel in accordance with a preferred embodiment of the present invention. 
     FIG. 7 is a top view of FIG. 3 showing minor axis coils on one side of the pixel in accordance with a preferred embodiment of the present invention. 
     FIG. 8 is a top view of FIG. 3 showing minor axis coils on one side of the paddles in accordance with a preferred embodiment of the present invention. 
     FIG. 9 is a top view of a MEMS mirror pixel with one coil for rotation about the minor axis in accordance with a preferred embodiment of the present invention. 
     FIG. 10 is a top view of mirror pixels over a magnet array in accordance with a preferred embodiment of the present invention. 
     FIG. 11 is a top view of mirror pixels over a magnet array in accordance with a preferred embodiment of the present invention. 
     FIG. 12 is a side view of mirror pixels over a magnet array at three heights in accordance with a preferred embodiment of the present invention. 
     FIG. 13 is a top view of a mirror pixel device having electromagnetic major axis actuation and electrostatic minor axis actuation in accordance with a preferred embodiment of the present invention. 
     FIG. 14 is a top view showing a common ground plane in accordance with a preferred embodiment of the present invention. 
     FIG. 15 is a top view showing an alternate common ground plane in accordance with another preferred embodiment of the present invention. 
     FIG. 16 is a side view of FIG. 13 of mirror pixel device having electromagnetic major axis actuation and electrostatic minor axis actuation in accordance with a preferred embodiment of the present invention. 
     FIG. 17 is a side of FIG. 15 with only one side of electrostatic minor axis actuation in accordance with a preferred embodiment of the present invention. 
     FIG. 18 is a top view of mirror pixels with only one side of electrostatic minor axis actuation over a magnet array in accordance with a preferred embodiment of the present invention. 
     FIG. 19 is a perspective view of FIG. 18 showing an interposer in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The use of an array of micromirrors such as MEMS mirror devices with high fill-factor may be advantageous for certain optical systems. One example of such a system would be a photonic switch or a photonic switching mirror array or a multiple wavelength optical switch. In this type of application, the incoming light from an optical fiber is sent through a diffraction grating. This would result in beams of light at different wavelengths. Different wavelengths represent different channels to be used for information transfer. Hence, a MEMS mirror array could be used to switch the incoming light to one of several output states, which may be another optical fiber, or a blocking state. This blocking state may also be referred to as a “black” state. Each channel would have its own respective mirror to direct the light of that wavelength from an input to a given output state. 
     Referring now to FIG. 1, as an example, a single channel MEMS mirror pixel  100  which could be used for rotation about a single axis having coils  110  is shown. A permanent magnet or set of magnets (not shown in FIG. 1) provides a strong magnetic field, which exerts a torque on the pixel as current is passed through the coils. The mirror may be fabricated by depositing a reflective surface on the back side (not shown) of the MEMS mirror pixel  100 . 
     Methods of manufacturing such mirror pixels are described in pending U.S. patent application, filed on Aug. 24, 2001, Ser. No. 09/939,422, Publication Number US20020050744 A1, entitled MAGNETICALLY ACTUATED MICRO-ELECTRO-MECHANICAL APPARATUS AND METHOD OF MANUFACTURE, assigned to Corning IntelliSense Corporation, a wholly-owned subsidiary of Assignee hereof, Corning Incorporated and incorporated by reference herein. 
     In such an optical system, it would be desirable to have a high linear fill-factor mirror array of mirror pixels  100 . High linear fill-factor can be defined as the length of the mirror along an axis divided by the pitch between adjacent mirror pixels. The geometry of the layout with high fill factor would capture more of the light from the diffraction grating at each channel. 
     High fill factor solutions are described in pending U.S. patent application, filed on Feb. 28, 2002, Ser. No. 10/085,963, entitled MICROELECTROMECHANICAL MIRROR DEVICES HAVING A HIGH LINEAR FILL FACTOR, assigned to Corning IntelliSense Corporation, a wholly-owned subsidiary of Assignee hereof, Corning Incorporated and incorporated by reference herein. 
     The light is incident on such a mirror array (not shown) from a diffraction grating, and may also pass through several optical components such as, but not limited to, a lens or lens array. Each wavelength or beam is deflected along the direction of a minor axis  120  to each individual mirror. The major axis  130  is the major axis of rotation, or the x-axis in this case. Deflection about a minor axis  120 , substantially orthogonal to the major axis, can be used to move beams around an input or output between switching states to prevent unwanted signal transmission or to compensate for minor non-planarities of the MEMS mirror array. An additional advantage of the minor axis rotation is that cross-talk during switching can virtually be eliminated. By actuating the minor axis during switching, the input beams can be decoupled from the non-selected output channels. Each mirror is capable of being actuated to and remaining at a given angle via a control system. 
     Versions of mirrors that rotate in two axes have used a gimbals structure  200 , as discussed supra, as described in conjunction with pending U.S. patent application, filed on Aug. 24, 2001, Ser. No. 09/939,422 (cited supra), and as shown for instance in FIG.  2 . The use of the gimbals  210  greatly reduces the possible linear fill factor as mirror “real estate” is minimized since the gimbal  210  itself takes area away from mirror to be used. The preferred embodiments of the present invention are advantageous as a result of the gimbals structure being eliminated from the mirror pixel as will be described in more detail infra. 
     Referring now to FIGS. 3-5 a dual-axis mirror pixel designed to operate without the use of a gimbals structure is provided in accordance with preferred embodiments of the present invention. In effect, FIGS. 4 and 5 are provided for clarity, as combined they produce the preferred embodiment shown in FIG.  3 . Hence, several of the elements of FIG. 3 are found in FIGS. 4 and 5. By and large, in these embodiments, there are four flexures  360 - 363  in FIG. 3 that are used to create the electrical connections to the four ends of the coils on the mirror. Multiple coils may be wired in series or parallel on the mirror to achieve the desired rotation in either the major or minor rotational axis. 
     Referring now to FIG. 3 a mirror pixel  300  having two coils  310  and  311  on each side of the major rotational axis  330  is shown for providing torque about the major axis  330  of rotation. The mirror pixel  300  is shown to include two paddles  315  and  316 , each paddle containing one major axis coil. Viewed from the top, the paddle  315  on the right side of the major rotational axis  330  contains coil  310 . The paddle  316  on the left side of the major rotational axis  330  contains coil  311 . The mirror may be fabricated by depositing a reflective surface on the backside of one or both paddles  315  and  316 . 
     In mirror pixel  300 , the torque for the minor axis  340  is provided by four additional coils  320 - 323 , also shown in FIG. 5, two on each side of the major and minor rotational axes  330  and  340  respectively, which when energized act to push and pull away from a set of permanent magnets (not shown) which would be located under the pixel  300  in accordance with one aspect of the preferred embodiment of the present invention. 
     Referring to FIG. 4, the mirror pixel  300  is provided containing coils  310  and  311 , associated with the major axis  330  of rotation in accordance with a preferred embodiment of the present invention. Also shown in FIG. 4 are cross-unders  324  and  325  utilized to connect coils  320 - 321  and  322 - 323  as shown in FIG.  5 . Referring to FIG. 5, the coils  320 - 323  for the minor axis  340  rotation are provided in accordance with a preferred embodiment of the present invention. Also shown in FIG. 5 a cross-over  312  that is utilized to connect coils  310  and  311  as shown in FIG.  4 . 
     In accordance with the preferred embodiments of the present invention, the required minor axis  340  rotation may be small when compared to the major axis  330  rotation. 
     An alternate preferred embodiment of the present invention would only have coils on one or the other of the two paddles  315  and  316  of FIG.  3 . Such an embodiment would include the combination of one coil  310  in paddle  315  for the major axis  330  of rotation, as shown in FIG. 6, and two coils  320  and  321  in paddle  315  for the minor axis  340  of rotation, as shown in FIG.  7 . 
     The advantage of such a “one-sided” design would be the reduction of the stress on one of the paddles, in this case paddle  316 , which would increase the radius of curvature of a mirror placed on that paddle. 
     Another preferred embodiment of the present invention would have just one or two of the four coils  320 - 323  of FIG. 5 for the minor axis. This embodiment is shown in FIG. 8 (showing two coils) and FIG. 9 (showing one coil). 
     It should be noted that several of the embodiments shown in the thus far described drawings might be combined into alternate preferred embodiments of the present invention. For instance, the elements shown in the embodiments of FIGS. 5 and 6 or FIGS. 6 and 8 may be combined to form an alternate preferred embodiment; the elements shown in the embodiments of FIGS. 6 and 9 may be combined to form another alternate preferred embodiment; the elements shown in the embodiments of FIGS. 6,  7 , and  8  could also be combined to form yet another alternate preferred embodiment. FIG.  4  and FIG. 7 can also be combined to form another embodiment with two major coils and two minor coils. These various embodiments do not represent all possible contemplated alternate preferred embodiments in accordance with the present invention but rather by starting such a list of permutations it is meant to show the broad scope possible allowed within the present invention. 
     In accordance with the present invention, the one coil  321  shown in FIG. 9 could be positioned in any one of the positions of the minor-axis coils shown in FIG.  5  and it would be possible to achieve some level of minor-axis rotation along minor axis  340  and/or major axis  330 . Likewise, the exact shape and number of turns or layers of the coils could be altered according to design needs without departing from the scope of the present invention. For instance, two layers of metal could be used to define the major axis of rotation  330 , and two additional metal layers, bringing the total to four metal layers could be used to form the minor axis of rotation coils. All such embodiments and variations or possible permutations are contemplated in the instant invention. 
     The coils on the pixels interact with a magnetic field provided by a set of permanent magnets to cause actuation. 
     Referring now to FIG. 10, two mirror pixels  1010  and  1020  are shown from a top view  1000  over three magnets  1030 ,  1040 , and  1050 , where the magnets  1030 ,  1040 , and  1050  may be extended (forming a magnet array  1070 ) in the direction of increasing number of mirrors. The magnets  1030 ,  1040 , and  1050  alternate in magnetization (out of and in to the page), i.e. north, south, north; or south, north, south. 
     For the case where coils are placed on only one of the two paddles of the major axis of rotation, preferably the paddle closest to the North-South magnet boundary or edge  1060  in FIG. 10, FIG. 11 shows a top view of two mirror pixels  1100  where the removed coils  1120  and  1130  are indicated with a dotted boundary. The paddles with removed coils  1120  and  1130  may have a reflective mirror surface deposited therein. Such an embodiment produces an array of mirrors with high linear fill factor and high radius of curvature. For clarity, only the coils for the major axis of rotation are shown in FIG.  11 . 
     A side view of the two mirror pixels shown in FIGS. 10 and 11 is provided in FIG. 12 in accordance with a preferred embodiment of the present invention. The mirror pixels in FIG. 12 are shown at three heights  1210 ,  1220  and  1230  over the magnets (removed coils  1120  and  1130  in the mirror region, not shown). As such, this type of configuration would depict coils on one-side of the pixel. There is an increase in torque per mA at smaller gaps or as the distance between the coil and the magnet is decreased. 
     Still another preferred embodiment of the present invention uses electrostatic actuation for one of the two axes of rotation and electromagnetic for the other axis of rotation. Such a device could use a at least one patterned electrode structure on a magnet array and ground the moving paddles to achieve the desired electrostatic actuation. The ground may be formed on the moving paddle by connecting one of the coil leads to the double paddle structure. Such an embodiment may only require two electrical connections to the movable pixel, in general fewer connections than the aforementioned electromagnetic dual-axis rotation embodiments. 
     Referring now to FIG. 13 a top view schematic representation of a mirror pixel device  1300  with coils  1310  and  1320  is provided for electromagnetic primary axis actuation and electrostatic secondary actuation in accordance with a preferred embodiment of the present invention. Electrodes  1330 - 1360  are shown as four pads. Flexures, though not shown, are also present in the preferred embodiment of the present invention. Alternatively, instead of four pads, these electrodes  1330 - 1360  may be represented as one common ground plane as discussed supra on the pixel  1300  as shown in a preferred embodiment of the present invention in FIG. 14 infra. 
     Referring now to FIG. 14 a top view schematic representation of a mirror pixel device  1400  is shown having coils  1410  and  1420  and a common ground plane or electrode  1430  (where for instance, electrodes  1330 - 1360  of FIG. 13 are connected) providing electromagnetic primary axis actuation and electrostatic secondary actuation in accordance with a preferred embodiment of the present invention. 
     If a common ground electrode  1430  is designed on the pixel  1400 , patterned electrodes may also be made on the magnet (FIG. 16) or an interposer (e.g.  1920  shown in FIG. 19) may be placed between the magnet and pixel  1400  in accordance with a further aspect of the preferred embodiment of the present invention. These patterned electrodes would be similar to electrodes  1330 - 1360  except that they would be on the magnet or interposer. One method to pattern the magnets in accordance within one aspect of a preferred embodiment of the present invention, is to coat the magnets with dielectric material, including but not limited to a polyimide material, and then patterning electrical lines directly on the polyimide material. A potential disadvantage of this method may be that the polymer material curing process may require the magnets to be re-magnetized after this process is complete. 
     FIG. 15 shows a top view schematic representation of a mirror pixel  1500  an alternate preferred embodiment of the present invention with a common ground plane or electrode  1530  in one half of the paddle with coils  1510  and  1520  providing electromagnetic primary axis actuation and electrostatic secondary actuation in accordance with a preferred embodiment of the present invention. Such an embodiment may allow the paddle under coil  1510  to achieve higher radius of curvature. It should also be noted that coil  1510  may entirely be removed in accordance with the present invention thereby further increasing the radius of curvature. 
     Referring now to FIG. 16 a side view schematic of a mirror pixel  1600  of a preferred embodiment of the present invention having an interlayer dielectric  1610  on the movable pixel is shown. The dielectric layer  1610  may be made from materials including but not limited to, for example, polyimide, silicon dioxide, silicon nitride, or other dielectric layer materials. 
     The pads  1640  and  1650  shown in FIG. 16 for electrostatic actuation may be patterned on the magnetic material  1030 ,  1040 ,  1050 . If the magnetic material is electrically conductive, an interlayer dielectric may be utilized (not shown in FIG. 16) between the electrostatic pads or patterned electrodes  1640  and  1650  and the magnetic material  1030 ,  1040 , and  1050 . Electrodes  1630  and  1660  are not shown, as they would be behind  1640  and  1650 , respectively. 
     As previously described the four electrodes  1330 - 1360  on the pixel in FIG.  13  and hence electrodes shown in FIGS. 16 may be changed to a common ground plane where a separate set of electrodes is patterned on the magnets, or some form of interposer is utilized in accordance with another aspect of a preferred embodiment of the present invention as will be discussed in conjunction with FIG.  19 . 
     Referring then to FIG. 17, a side view schematic of a mirror pixel  1700  of an alternate preferred embodiment of the present invention is provided where the electrostatic actuation is shown as being only on one side of the pixel via electrodes  1640 ,  1650  (removed) and common ground plane or electrode  1725  on the mirror. It should be noted that it might be desirable to remove coil  1310  and dielectric  1610  in the area of coil  1310  to achieve high radius of curvature. Still further, while two coils  1310  and  1320  are shown in FIG. 17, in accordance with yet another aspect of a preferred embodiment of the present invention, any one coil on any one paddle may be utilized without the need for a second coil. 
     Referring now to FIG. 18 a top view  1800  of mirror pixel array  1820  positioned over magnet array  1070  in accordance with yet another aspect of the preferred embodiment of the present invention is provided showing how the electrodes  1630  and  1640  of FIG. 17 ( 1630  not visible in FIG. 17 as it is behind  1640 ), for instance, associated with the electrostatic actuation could be positioned in an array. This type of embodiment is desirable for reducing the cross-talk of adjacent devices as the alternating nature of adjacent mirrors increases the physical distance between any two electrostatic pads  1640  and  1630  on adjacent pixels. The alternating or staggered nature of the electrostatic pads increases the distance between pads on neighboring pixels thereby reducing cross-talk. The one-sided, staggered configuration may be applied to the minor-axis electromagnetic actuation described supra. These embodiments have the advantage of reducing cross-talk and achieving high radius of curvature. 
     Referring now to FIG. 19 a perspective view schematic  1900  of a mirror pixel array  1910  of an alternate preferred embodiment of the present invention is shown providing a ground plane having an interposer  1920  situated above a magnet array  1070 . Note that, while present, the electrodes on the movable pixel array  1910  are not shown in FIG. 19 for clarity. The interposer  1920  is preferably made of pyrex. Conductive pads or patterned electrodes  1930  and  1940 , made from gold for example, are also shown deposited on interposer  1920 . As can be seen clearly in both arrays of FIGS. 18 and 19, a center array of mirrors  1810  is shown having neither coils nor electrodes. With such an embodiment, as discussed above in conjunction with FIG. 17, undesirable cross-talk is reduced. 
     Additionally, the electrodes described in conjunction with the embodiments of the present invention may be utilized for the purpose of sensing rotation about one or both axes by measuring the capacitance between the electrodes and the mirror pixel. In one aspect of the present invention for measuring minor axis rotation, the electrostatic pads on the interposer  1920  in FIG. 19 could be utilized to measure the differential capacitance for minor axis rotation. 
     In the case of an optical system for wavelength switching, as described supra, the minor axis rotation is used to compensate for small variations in wafer curvature, or any pointing accuracy issues that arise as a result of the fabrication of the device. An additional advantage of the minor axis rotation of the present invention as mentioned supra is that optical cross-talk during switching can be virtually eliminated. By actuating the minor axis during switching, the input beams can be decoupled from the output channels. 
     It would be obvious to one skilled in the art that the positions of the coils and electrodes could be changed, and that the number and size of the coils and/or electrodes could be altered subject to particular design considerations and desires. There are other variations of flexure and coil design not shown that would result in the same actuation principles as described by the present invention. However, it is intended, that all such potential variations or permutations fall within the scope of and would be motivated by the novel notions described in conjunction with the preferred embodiments of the present invention. 
     Several commercial applications are contemplated for the preferred embodiments of the present invention. Electromagnetic actuators may be useful in fluid control applications; for instance, actuators for valves. Also, as mentioned supra, a MEMS based wavelength optical switch or a MEMS based channel gain equalizer would also benefit from electromagnetic actuation based on dual-axis rotation and high fill factor mirrors. 
     Therefore, having described various preferred embodiments of the present invention, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.