Patent Publication Number: US-6903486-B2

Title: Balanced microdevice

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. provisional patent application Ser. No. 60/323,628 filed Sep. 19, 2001 and is a continuation-in-part of U.S. patent application Ser. No. 09/727,794 filed Nov. 29, 2000, now U.S. Pat. No. 6,469,415, which claims priority to U.S. provisional patent application Ser. No. 60/167,951 filed Nov. 29, 1999; U.S. provisional patent application Ser. No. 60/174,562 filed Jan. 5, 2000; U.S. provisional patent application Ser. No. 60/227,933 filed Aug. 25, 2000 and U.S. provisional patent application Ser. No. 60/234,042 filed Sep. 20, 2000, the entire contents of each of which are incorporated herein by this reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is applicable to the field of microdevices and is more specifically applicable to electrostatic microdevices. 
     BACKGROUND 
     Microactuators, and particularly electrostatic microactuators, have heretofore been provided. See, for example, U.S. Pat. No. 5,998,906 and International Publication Number WO 00/36740. Such microactuators can be utilized in microdevices, for example in the telecommunications industry and in the data storage industry, for moving optical elements. See, for example, International Publication Number WO 00/36447 and U.S. Pat. No. 6,134,207. It has been found that applied external accelerations can undesirably effect the performance of microdevices employing microactuators. 
     What is needed, therefore, is a microdevice that is substantially mechanically balanced such that an element moved thereby does not appreciably move when subjected to external accelerations. 
     What is also needed is a rotary electrostatic microactuator that rotates about a pivot point disposed outside the confines of the microactuator. 
     SUMMARY OF THE INVENTION 
     In general, a balanced microdevice is provided that includes a substrate and at least one comb drive assembly having first and second comb drive members. The first comb drive member is mounted on the substrate and the second comb drive member overlies the substrate. At least one spring member is provided that has a first end portion coupled to the substrate and a second end portion coupled to the second comb drive member. The first comb drive member has a plurality of spaced-apart first comb drive fingers and the second comb drive member has a plurality of spaced-apart second comb drive fingers. The second comb drive member is movable between a first position in which the first and second comb drive fingers are not substantially fully interdigitated and a second position in which the first and second comb drive fingers are substantially fully interdigitated. A counterbalance is carried by the substrate and coupled to the second comb drive member for inhibiting undesirable movement of the second comb drive member in response to externally applied accelerations to the microdevice. 
     In one embodiment, a microdevice is provided that includes a substrate, a movable structure overlying the substrate, an element and a lever assembly having a pivot and a lever coupled to and pivotable about the pivot. The lever has a first extremity coupled to the movable structure and an opposite second extremity coupled to the element. The movable structure causes the lever to pivot about the pivot so as to move the element in a direction of travel. The element is substantially mechanically balanced to inhibit undesirable movement of the element in the direction of travel in response to externally applied forces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are somewhat schematic in many instances and are incorporated in and form a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a plan view of an electrostatic microactuator. 
         FIG. 2  is a plan view of a balanced microdevice of the present invention utilizing an electrostatic microactuator. 
         FIG. 3  is a fragmentary plan view of a portion of the first microactuator of the balanced microdevice of  FIG. 2  taken along the line  3 — 3  of FIG.  2  and rotated 90°. 
         FIG. 4  is a cross-sectional view of the first microactuator of  FIG. 2  taken along the line  4 — 4  of FIG.  2 . 
         FIG. 5  is a fragmentary plan view of the first microactuator of  FIG. 2  taken along the line  5 — 5  of FIG.  2  and rotated 90°. 
         FIG. 6  is a plan view of the balanced microdevice of  FIG. 2  in a second position. 
         FIG. 7  is a fragmentary plan view, similar to  FIG. 3 , of a portion of the first microactuator of  FIG. 6  taken along the line  7 — 7  of FIG.  6  and rotated 90°. 
         FIG. 8  is a fragmentary plan view, similar to  FIG. 5 , of the first microactuator of  FIG. 2  in a position between the position of FIG.  2  and the position of FIG.  6 . 
         FIG. 9  is a plan view of another embodiment of the balanced microdevice of the present invention. 
         FIG. 10  is a plan view of the balanced microdevice of  FIG. 9  in a second position. 
         FIG. 11  is a plan view of a further embodiment of the balanced microdevice of the present invention. 
         FIG. 12  is a plan view of the balanced microdevice of  FIG. 11  in a second position. 
         FIG. 13  is a plan view of a microdevice with lever assembly of the present invention. 
         FIG. 14  is a plan view of the microdevice with lever assembly of  FIG. 13  in a second position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, microactuator or motor  507  shown in  FIG. 1  is a MEMS-based microactuator capable of being used in a microdevice such as tunable laser of the type disclosed in copending U.S. patent application Ser. No. 09/728,212 filed Nov. 29, 2000, the entire content of which is incorporated herein by this reference. Microactuator  507  is a of a rotary or angular electrostatic microactuator formed from a substrate  526  that extends substantially in a plane. A plurality of first and second comb drive assemblies  527  and  528  are carried by substantially planar substrate  526  and are arranged on the substrate in first and second sets  531  and  532 . Each of the first and second comb drive assemblies includes a first comb drive member or comb drive  533  mounted on substrate  526  and a second comb drive member or comb drive  534  overlying the substrate  526 . At least first and second spaced-apart suspension members or spring members are included in microactuator  507  for supporting or suspending second comb drives  534  over the substrate  526  and for providing radial stiffness to the movable second comb drives  534 . As shown, first and second outer suspension members or springs  536  and  537  and a central suspension member or spring  538  are provided. Second comb drives  534  are part of a movable structure  539  overlying the substrate  526 . Any suitable movable element such as an optical element  506  can be mounted on movable structure  539  for movement relative to substrate  526 . The optical element  506 , as shown in  FIG. 1 , is a microreflector. 
     Substrate  526  is made from any suitable material such as silicon and is preferably formed from a silicon wafer having a thickness ranging from 400 to 600 microns and preferably approximately 400 microns. Springs  536 - 537 , first and second comb drive assemblies  527  and  528  and the remainder of movable structure  539  are formed atop the substrate  526  by a second or top layer  542  made from a wafer of any suitable material such as silicon. Top layer or wafer  542  has a thickness ranging from 10 to 200 microns and preferably approximately 85 microns and is preferably fusion bonded to the substrate  526  by means of a silicon dioxide layer (not shown). The components of microactuator  507  are preferably etched from wafer  542  by deep reactive ion etching (DRIE) techniques or the Lithographie Gavanometrie and Abformung (LIGA) process, which permit such structures to have a high aspect ratio and thus enhance the out-of-plane stiffness of such structures. Springs  536 - 538  and movable structure  539  are spaced above the substrate  526  by an air gap (not shown), that ranges from 3 to 30 microns and preferably approximately 15 microns so as to be electrically isolated from the substrate  526 . 
     First and second sets  531  and  532  of comb drive assemblies are symmetrically disposed about a radial centerline  543  of microactuator  507  and each include a first comb drive assembly  527  and a second comb drive assembly  528 . Second comb drive assembly  528  of the first set  531  is disposed adjacent centerline  543  and first second comb drive assembly  527  of the second set  532  is disposed adjacent the centerline  543 . A first comb drive assembly  527  is spaced farthest from centerline  543  in the first set  531  and a second comb drive assembly  528  is spaced farthest from the centerline in the second set  532 . Each of the comb drive assemblies  527  and  528  is centered along a radial line which intersects radial centerline  543  at the virtual pivot point (not shown) of microactuator  507 . Each of the first and second comb drive assemblies  527  and  528  has a length ranging from 300 to 3000 microns and preferably approximately 1300 microns, and commences a radial distance from the pivot point of microactuator  507  ranging from 500 to 5000 microns and preferably approximately 2000 microns. 
     First comb drive  533  of each of first and second comb drive assemblies  527  and  528  is immovably secured to substrate  526 . Each comb drive  533  has a radially-extending bar or truss  546  provided with a first or inner radial portion  546   a  and a second or outer radial portion  546   b . A plurality of comb drive fingers  547  extend from one side of bar  546  in radially spaced-apart positions along the length of the bar. Comb drive fingers or comb fingers  547  can be of any suitable shape and are preferably approximately arcuate in shape. Comb fingers  547  extend perpendicularly from bar  546  and thereafter substantially arc along a radius that preferably commences at the axis of rotation or virtual pivot point of microactuator  507 . In a preferred embodiment, piecewise linear segments are used to form the comb fingers  547  for approximating such an arcuate shape. 
     Second comb drives  534  are spaced above substrate  526  so as to be movable relative to the substrate and first comb drives  533 . The second comb drives  534  have a construction similar to first comb drives  533  and, more specifically, are formed with a radially-extending bar or truss  551  having a first or inner radial portion  551   a  and a second or outer radial portion  551   b . A plurality of comb drive fingers or comb fingers  552  extend from one side of bar  551  in radially spaced-apart positions along the length of the bar  551 . Comb fingers  552  are substantially similar in construction and size to comb fingers  547  of the related comb drive assembly  527  or  528 . Movable comb fingers  552  of each second comb drive  534  are offset relative to the respective stationary comb fingers  547  so that comb fingers  552  can interdigitate with comb fingers  547  when the second comb drive  534  is pivoted about the virtual pivot point or pivot point of microactuator  507  towards the respective first comb drive  533 . 
     The inner radial portions  551   a  of the two second comb drive bars  551   a  in each of the first and second sets  531  and  532  of comb drive assemblies are rigidly interconnected by a connector bar or beam  553  that extends radially inside the respective first comb drives  533  of such set  531  or  532 . The outer radial portions  551   b  of second comb drive assembly  528  in first set  531  and of first comb drive assembly  527  in second set  532  are rigidly interconnected so that the second comb drives  534  in microactuator  507  move in unison about the pivot point of such microactuator. Movable structure  539  includes second comb drives  534  and first and second connector beams  553  and has a thickness ranging from 15 to 200 microns and preferably approximately 85 microns. 
     Means including spaced-apart first and second outer springs  536  and  537  and optional central spring  538  are included within rotary electrostatic microactuator  507  for movably supporting second comb drives  534  and the remainder of movable structure  539  over substrate  526 . First and second outer springs  536  and  537  are symmetrically disposed about radial centerline  543  and central spring  538  extends between first and second sets  531  and  532  of comb drive assemblies. Each of the springs  536 - 538 , when in its rest position as shown in  FIG. 1 , is centered on a radial line extending through the virtual pivot point of microactuator  507 . Central spring  538  extends along radial centerline  543 . The springs are spaced approximately 20 to 30 degrees apart about the virtual pivot point of microactuator  507 . 
     Each of the springs  536 - 538  is formed from a single beam-like spring member  556  having a first or inner radial end portion  556   a  and a second or outer radial end portion  556   b . The inner radial end portion  556   a  of the spring member  556  is secured or coupled to substrate  526  at an anchor  557 . The balance of the spring member  556  is spaced above the substrate by an air gap. The outer radial end portion  556   b  of outer springs  536  and  537  is secured or coupled to the outer radial extremity of the adjacent second comb drive bar  551  and the outer radial end portion  556   b  of central spring  538  is secured or coupled to the outer radial extremity of the adjacent second comb drive bars  551  forming the inner boundary of each of first and second sets  531  and  532  of comb drive assemblies. Each of the spring members  556  has a length ranging from 300 to 3000 microns and preferably approximately 1000 microns and has a width ranging from one to 20 microns and preferably approximately five microns. First and second elongate sacrificial bars  558  and  559  of the type described in U.S. Pat. No. 5,998,906 extend along opposite sides of each spring member  556  for ensuring even etching and thus the desired rectangular cross section of the spring member  556 . Springs  536 - 538  each have a thickness similar to movable structure  539  and preferably the same as movable structure  539 . Although three springs  536 - 538  are disclosed for microactuator  507 , it should be appreciated that two such springs or greater than three such springs can be provided. In addition, although first and second comb drive assemblies  527  and  528  are shown and described as being disposed between outer springs  536  and  537 , some or all of such comb drive assemblies  527  and  528  can be disposed outside of the springs  536  and  537 . 
     Each of the second comb drives  534  of first and second comb drive assemblies  527  and  528  is movable in a first direction of travel about the pivot point of microactuator  507  between a first or intermediate position in which comb fingers  547  and  552  of the comb drive assembly are not substantially fully interdigitated and a second position in which such comb fingers  547  and  552  are substantially fully interdigitated. Each of the comb drive assemblies  527  and  528  is shown in  FIG. 1  in the first position in which the comb fingers  547  and  552  of each comb drive assembly  527  and  528  are not substantially fully interdigitated. More specifically, comb fingers  547  and  552  of the second comb drive assembly  528  in first set  531  and of the first comb drive assembly  527  in second set  532  are partially interdigitated while in the first position and comb fingers  547  and  552  of the first comb drive assembly  527  in first set  531  and of the second comb drive assembly  528  in second set  532  are not interdigitated while in the first position. It can thus be seen that although comb fingers  547  and  552  can be partially interdigitated when a second comb drive  534  is in its first position, the comb fingers can alternatively be disengaged and thus not interdigitated when the second comb drive is in its first position. When in their second position, movable comb fingers  552  extend between respective stationary comb fingers  547 . The movable comb fingers  552  approach but preferably do not engage stationary bar  546  of the respective first comb drive  533  and, similarly, the stationary comb fingers  547  approach but preferably do not engage movable bar  551  of the respective second comb drive  534 . 
     Each of the second comb drives  534  of first and second comb drive assemblies  527  and  528  is also movable in a second direction of travel about the pivot point of microactuator  507  from the intermediate position shown in  FIG. 1  to a third position in which the comb fingers  547  and  552  are spaced apart and fully disengaged (not shown). When comb fingers  547  and  552  of one comb drive assembly  527  or  528  in a set  531  or  532  are in the first position, the comb fingers of the other comb drive assembly  527  or  528  are in the third position. Thus each second comb drive  534  is movable between the second position, in which comb fingers  547  and  552  are substantially fully interdigitated, to the first or intermediate position, in which the comb fingers are not substantially fully interdigitated, to the third position, in which the comb fingers are fully disengaged and spaced apart. 
     Electrical means is included for driving the second comb drives  534  between their first and second positions. Such electrical means includes a suitable controller and preferably a controller and voltage generator  561  that is electrically connected to the first and second comb drives  533  and  534  of microactuator  507 . In this regard, the outer radial end portion  546   b  of each first comb drive bar  546  is electrically connected by means of a lead  562  to a bond pad  563  provided on a side of microactuator  507 . Movable structure  539  is electrically connected by a lead  566  to a bond pad  567  also provided on a side of substrate  526 . The lead  566  extends from such bond pad  567  to inner radial portion  556   a  of second spring  536 . The bond pads  563  and  567  are electrically coupled by suitable wires or leads  568  to controller and power supply  561 . 
     Means in the form of a closed loop servo control can optionally be included in controller  561  or related control electronics for monitoring the position of movable structure  539  relative to substrate  526 . For example, controller  561  can include a conventional algorithm for measuring the capacitance between comb fingers  552  of movable comb drives  534  and comb fingers  547  of the stationary comb drives  533 . A signal separate from the drive signal to the comb drive members can be transmitted by the controller to the microactuator for measuring such capacitance. Such a method does not require physical contact between the comb drive fingers. The position of optical element  506  can be calibrated to the capacitance of the microactuator  507  and thus the position of the optical element can be monitored and controlled. This method of servo control can be implemented at low cost and does not require extra optical components. 
     The structural components of microactuator  507 , that is movable structure  539 , springs  536 - 538  and first comb drives  533 , have the shape of a truncated fan when viewed in plan (see FIG.  1 ). In this regard, such components resemble a truncated or foreshortened sector of a circle, that is such components do not extend to the virtual pivot point of microactuator  507  but instead are spaced radially outwardly from such virtual pivot point. As such, the virtual pivot point of microactuator  507  intersects the plane of substrate  526  at a point outside the confines of the components of such actuator and more specifically outside the confines of movable structure  536 . Springs  536  and  537  and movable structure  539  subtend an angle about the virtual pivot point of microactuator  507  of less than 180° and preferably less than 90°. In the specific embodiment of microactuator  507  shown in FIG.  1  and discussed above, springs  536  and  537  and movable structure  539  subtend an angle of approximately 45 degrees about such virtual pivot point. 
     In operation and use, movable structure  539  is movable about the virtual pivot point of microactuator  507  in opposite first and second angular directions from its at rest or intermediate position shown in FIG.  1 . When movable structure  539 , and thus reflector  506 , moves in a counterclockwise direction about such virtual pivot point, second comb drives  534  of the second comb drive assembly  528  in each of the first and second sets  531  and  532  move to their respective second positions so that comb fingers  547  and  552  of the second comb drive assemblies  528  are substantially fully interdigitated. When movable structure  531  is moved in a clockwise direction about the virtual pivot point of microactuator  507 , second comb drives  534  of the first comb drive assembly  527  in each of the first and second sets  531  and  532  move to their respective second positions so that comb fingers  547  and  552  of the first comb drive assemblies  527  are substantially fully interdigitated. Springs  536 - 538  provide radial rigidity to movable structure  539  for inhibiting snap over of the interdigitated comb fingers  547  and  552 . Springs  536 - 538  provide radial rigidity to movable structure  539  for inhibiting snap over of comb fingers  547  and  552 . 
     When it is desired to rotate movable structure  539  and thus reflector  506  in a clockwise direction about the virtual pivot point of microactuator  507 , in one preferred method a voltage potential is supplied by controller  561  to stationary comb drives  533  of first drive assemblies  527  so as to cause comb fingers  552  of the respective movable comb drives  534  to be electrostatically attracted to comb fingers  547  of the stationary comb drives  533 . Such attraction force causes comb fingers  552  to move towards and interdigitate with comb fingers  547 . The amount of such interdigitation, and thus the amount movable structure  539  and reflector  506  pivot about the virtual pivot of microactuator  507 , can be controlled by the amount of voltage supplied to the stationary comb drives  533  of the first comb drive assemblies  527 . When it is desired to pivot movable structure  539  and reflector  506  in a counterclockwise direction about the virtual pivot axis of microactuator  507 , a suitable voltage potential can be supplied to stationary comb drives  533  of second comb drive assemblies  528  so as to cause comb fingers  552  of the respective movable comb drives  534  to move towards and interdigitate with comb fingers  547  of the second comb drive assemblies  528 . As can be seen, the second comb drives  534  of one of first comb drive assemblies  527  or second comb drive assemblies  528  are in their second positions when the second comb drives  534  of the other of second comb drive assemblies  528  or first comb drive assemblies  527  are in their first positions. 
     Suitable voltage potentials to drive comb drive assemblies  527  and  528  can range from 20 to 200 volts and preferably range from 60 to 150 volts. Microactuator  507  is capable of a +/−1.5 degrees of pivotable rotation about the virtual pivot point of the microactuator  507 , that is rotational movement of 1.5 degrees in both the clockwise and the counterclockwise directions for an aggregate pivotal movement of three degrees when drive voltages of 120 or 140 volts are utilized. The amount of a angular deflection of movable structure  539  about such virtual pivot point is dependent on the number of comb fingers  547  and  552 , the electrostatic gap between the comb fingers and the length and width of springs  536 - 538 . 
     Radially-extending springs  536 - 538  provide radial rigidity and stiffness to movable second comb drives  534  and thus inhibit snap over of the comb fingers  547  and  552  during interdigitation. The nonfolded design of springs  536 - 538  enhances out-of-plane stiffness, that is stiffness in microactuator  507  that is out of the plane of movable structure  539 . Such out-of-plane stiffness facilitates support of the relatively large reflector  506  and inhibits misalignments between the reflector  506  and diffraction grating  504  during operation of microactuator  507 . 
     Microdevices incorporating microactuators, like microactuator  507 , can be provided that are balanced so that the movable portions of such actuators, and elements or objects moved thereby, are not undesirably moved when external accelerations or forces are applied to the device. An embodiment of such microdevice is shown in  FIGS. 2-8 . Balanced apparatus or microdevice  652  shown therein includes at least one microactuator coupled to a movable member or element, such as microreflector  506 , for moving such element and more specifically for pivoting the microreflector  506 . The microdevice is balanced to inhibit undesirable movement of the reflector  506  from externally applied accelerations to the device and can be used in any suitable application such as in a tunable laser. In one preferred embodiment, the balanced microdevice  652  includes a first microactuator or motor  653  which is preferably a MEMS-based microactuator of any suitable type and more preferably an electrostatic microactuator similar to microactuator  507  described above. Like reference numerals have been used to describe like components of microactuators  507  and  653 . 
     Microactuator  653  has at least one and preferably a plurality of first and second comb drive assemblies  656  and  657  carried by substantially planar substrate  526  and arranged on the substrate in first and second sets  658  and  659  (see FIGS.  2  and  6 ). Each of the first and second comb drive assemblies includes a first comb drive member or comb drive  662  mounted on substrate  526  and a second comb drive member or comb drive  663  overlying the substrate. At least first and second spaced-suspension beams or spring members  664  and  666  are included in microactuator  653  for supporting or suspending second comb drives  663  over the substrate  526  and for providing radial stiffness to the movable second comb drives  663 . The second comb drives  663  are part of a movable portion or structure  667  overlying the substrate  526 . 
     First and second comb drive assemblies  662  and  663 , first and second springs  664  and  666  and the remainder of movable structure  667  are formed atop substrate  526  by a second or top layer  668  made from a wafer of any suitable material such as silicon. Top layer or wafer  668  has a thickness ranging from 10 to 200 microns and preferably approximately 85 microns and is preferably fusion bonded to the substrate  526  by means of a silicon dioxide layer  669  (see FIG.  4 ). The components of microactuator  653  are preferably etched from top wafer  668  by any suitable technique and preferably by the techniques discussed above with respect to microactuator  507 . Springs  664  and  666  and movable structure  667  are spaced above the substrate  526  by an air gap  671  that ranges from 3 to 30 microns and preferably approximately 15 microns, so as to be electrically isolated from the substrate  526 . 
     First and second sets  658  and  659  of comb drive assemblies are symmetrically disposed about a radial centerline  672  of microactuator  653  and each include a first comb drive assembly  656  and a second comb drive assembly  657  (see FIG.  2 ). First comb drive assembly  656  of the first set  658  and second comb drive assembly  657  of the second set  659  are disposed adjacent centerline  672 . A second comb drive assembly  657  is spaced away from the centerline  672  in the first set  658  and a first comb drive assembly  656  is spaced away from the centerline in the second set  659  so as to be adjacent the respective sides of microactuator  653 . Each of the first and second comb drive assemblies  656  and  657  has a length ranging from 300 to 3000 microns and preferably approximately 1300 microns, and commences a radial distance ranging from 500 to 5000 microns and preferably approximately 2000 microns from the pivot point of microactuator  653 . 
     First comb drive  662  of each of first and second comb drive assemblies  656  and  657  is immovably secured to substrate  526 . Each first comb drive  662  has a radially-extending truss or bar  676  provided with a first or inner radial portion  676   a  and second or outer radial portion  676   b  (see FIGS.  5  and  8 ). A plurality of first comb drive fingers or comb fingers  677  extend from one side of bar  676  in radially spaced-apart positions along the length of the bar. Comb fingers  677  can be of any suitable shape and are preferably approximately arcuate in shape. In a preferred embodiment, piecewise linear segments are used to form comb fingers  677  for approximating such an arcuate shape. 
     Second comb drives  663  are spaced above substrate  526  so as to be movable relative to the substrate and first comb drives  662 . The second comb drives  663  have a construction similar to first comb drives  662  and, more specifically, are formed with a radially-extending truss or bar  681  having a first or inner radial portion  681   a  and a second or outer radial portion  681   b  (see FIGS.  5  and  8 ). A plurality of second comb drive fingers or comb fingers  682  extend from one side of bar  681  in radially spaced-apart positions along the length of the bar  681 . Comb fingers  682  are substantially similar in construction in size to comb fingers  677  of the related comb drive assembly  656  or  657 . In each of comb drive assembly sets  658  and  659 , the second comb drives  663  of the first and second comb drive assemblies  656  and  657  share a second bar  681  such that the two second comb drives  663  are back-to-back. Movable comb fingers  682  of each second comb drive  663  are offset relative to the respective stationary comb fingers  677  so that the movable comb fingers  682  can interdigitate with the stationary comb fingers  677  when the second comb drive  663  is pivoted about the virtual pivot point or pivot point of microactuator  653  towards the respective first comb drive  662 . 
     Each of first and second comb fingers  677  and  682  are optionally inclined relative to respective bars  676  and  681 , that is each comb finger is joined to the respective bar at an oblique angle as opposed to a right angle (see FIG.  3 ). The inclination angle  683  at which each comb finger  677  and  682  is joined to its respective bar  676  or  681 , measured from a line extending normal to the bar, can range from zero to five degrees and is preferably approximately three degrees. Stationary comb fingers  677  are inclined at such inclination angle  683  towards outer radial portion  376   b  of the stationary bar  676 . Conversely, movable comb finger  682  are inclined at inclination angle  683  towards inner radial portion  681  of the movable bar  681 . The inclination angle  683  of first comb fingers  677  is preferably equal to the inclination angle of second comb fingers  682 . In one preferred embodiment, the equation defining the shape of each first and second comb finger  677  and  682  is:
 
 R   2 (θ)= R   0   +mθ+b,  
 
where R 0  is the nominal radius of the comb finger measured from the virtual pivot point of microactuator  653 , m is the slope and b is the offset of the comb finger from the nominal radius.
 
     Each second comb drive finger  682  is optionally offset relative to the midpoint between the adjacent pair of first comb drive fingers  677  between which the second comb drive finger interdigitates when second comb drive  663  is electrostatically attracted to first comb drive  662 . Each adjacent pair of first comb drive fingers  677  has a space  686  therebetween, as shown most clearly in  FIGS. 3 and 7 . The midpoint between an adjacent pair of first comb drive fingers  677  is represented by an imaginary midpoint line  687  in the figures. The initial offset of each first comb drive finger  677  from the respective midpoint line  687 , measured when second comb drive  663  is in its rest position shown in  FIGS. 2 and 17 , can range from zero to two microns and is preferably approximately 0.75 microns in the illustrated embodiment. The offset of comb drive fingers  677  from midpoint line  687  has been exaggerated in  FIG. 3  to facilitate the visualization and understanding thereof. It should be appreciated that comb fingers  677  and  682  which extend from their respective comb drive bars in arcs having a constant radius measured from the pivot point of microactuator  653  can be provided. 
     Although first and second comb fingers  677  and  682  can be identical in shape and size, the comb drive fingers of first microactuator  653  vary in size and shape. More specifically, second comb fingers  682  in first comb assembly  656  of the first set  658  of comb drive assemblies decrease in length in a linear manner from the inner radial extremity of second or movable comb drive  663  to the outer radial extremity thereof. Similarly, second comb fingers  682  in second comb drive assembly  657  of the second set  659  of comb drive assemblies decrease linearly in length from the inner radial portion  681   a  of second or movable comb bar  681  to the outer radial portion  681   b  of the second bar. 
     First and second comb fingers  677  and  682  can be of constant width, as they extend outwardly from the respective bars  676  or  681 , as with the comb fingers  677  and  682  in first comb drive assembly  656  of first set  658  and the comb fingers in second comb drive assembly  657  of second set  659 , or can vary in width along the length thereof. For example, each of the comb fingers  677  and  682  in second comb drive assembly  657  of the first set  658  and in first comb drive assembly  656  of the second set  659  has an inner of proximal portion that is wider than the outer or distal portion of such comb finger. Specifically, each first comb finger  677  in such comb drive assemblies has an inner or proximal portion  691  and an outer or distal portion  692 , as shown in  FIGS. 5 and 8 . Similarly, each second comb finger  682  in such comb drive assemblies has an inner or proximal portion  693  and an outer or distal portion  694 . Each inner portion  691  or  693  has a width ranging from 4 to 20 microns and preferably approximately 10 microns, and each outer portion  692  and  694  has a smaller width ranging from 2 to 12 microns and preferably approximately five microns. Each of the stationary inner portions  691  has a length ranging from 40 to 150 microns and preferably approximately 80 microns and preferably, as shown in  FIG. 5 , and decreases linearly in relative length, that is after taking into consideration the increase in length with radius of each comb drive finger to reflect the truncated sector-shaped or pie-shaped configuration of the comb drive assemblies, from inner radial portion  676   a  of the first bar  676  to outer radial portions  676   b  of the first bar. Each of the movable inner portions  693  has a length of ranging from 40 to 150 microns and preferably approximately 80 microns and increases linearly in relative length from inner radial portion  681   a  to outer radial portions  681   b  of the second bar  681 . 
     The outer radial portions  681   b  of the second bars  681  are joined to a connector bar or shuttle  696  extending substantially perpendicularly to the bars  681  and arcuately relatively to the virtual pivot point of microactuator  653 . Shuttle  696  is a substantially rigid member and is included in movable structure  667  of the microactuator  653 . The shuttle  696  forms the outer radial periphery of microactuator  653  and extends sideways to each of the sides of the microactuator. 
     Means including at least first and second springs  664  and  666  are provided in rotary electrostatic microactuator  653  for movably supporting second comb drives  663  and the remainder of movable structure  667  over the substrate  526 . First and second springs  664  and  666  are symmetrically disposed about radial centerline  672  and, when in their respective rest positions shown in  FIG. 2 , are each centered on a radial line extending through the virtual pivot point of first microactuator  653 . The springs  664  and  666  are angularly spaced apart approximately 20 to 30 degrees about the virtual pivot point of microactuator  653 . First and second comb drive assemblies  656  and  657  are disposed between springs  664  and  666 , although at least some of the comb drives assemblies can optionally be disposed outside of the springs. 
     Each of springs  664  and  666  can be of any suitable type and is preferably formed from a single beam-like spring member  698  having a first or inner radial end portion  698   a  and a second or outer radial end portion  698   b  (see FIGS.  2  and  6 ). It should be appreciated however that first and second springs  664  and  666  can have other configurations when in their rest positions, such as being pre-bent as disclosed in U.S. Pat. No. 5,998,906, and be within the scope of the present invention. The inner radial end portion  698   a  is coupled or secured to substrate  526  at an anchor  699  so as to suspend the spring member  698  above the substrate a distance equal to air gap  671 . The outer radial end portion  698   b  of each spring member  698  is secured to shuttle  696  and thus coupled to the second comb drive  663  of first microactuator  653 . Each of the spring members  698  has a length ranging from 300 to 3000 microns and preferably approximately 1000 microns and has a width ranging from 1 to 20 microns and preferably approximately four microns. First and second elongate sacrificial bars  701  of the type described in U.S. Pat. No. 5,998,906 extend along each side of each spring member  698  for ensuring even etching of the desired rectangular cross section of the spring member  698 . Each of springs  664  and  666  has a thickness similar to the thickness of movable structure  667 , and preferably the same as movable structure  667 . In the embodiment illustrated in  FIGS. 2-8 , the springs  664  and  666  form the respective first and second radial sides of first microactuator  653 . 
     Each of second comb drives  663  is movable in opposite first and second angular directions about the virtual pivot point of microactuator  653  in the same manner as discussed above with respect to microactuator  507 . In general, each second comb drive  663  is movable in the first angular direction about the pivot point between a first or intermediate position in which comb fingers  677  and  682  of respective comb drive assembly are not substantially fully interdigitated and a second position in which such comb fingers are substantially fully interdigitated. Each of first and second comb drive assemblies  656  and  657  is shown in  FIG. 2  in their first positions and second comb drive assemblies  657  are shown in  FIG. 6  in their second positions. Each of the second comb drives  663  is also movable in the second angular direction about the pivot point of microactuator  653  between its intermediate position and a third position which comb fingers  677  and  682  are spaced apart and fully disengaged. First comb drive assemblies  656  are shown in  FIG. 6  in their spaced apart and fully disengaged third positions. 
     Means is included within first microactuator  653  for limiting the angular movement of movable structure  667  between its extreme angular positions about the virtual pivot point of the microactuator. In this regard, a bumper  706  is formed on shuttle  696  for alternatively engaging first and second stops  707  formed on substrate  526  from top wafer  668 . 
     Electrical means is included in controller  561  or related control electronics for driving second comb drives  663  between their first and second positions. Such electrical means include a suitable controller, such as controller and voltage generator  561  discussed above with respect to microactuator  507 , that is electrically connected to the first and second comb drives  662  and  663  of microactuator  653 . In this regard, the inner radial end portion  676   a  of each first comb drive  662  is electrically connected to controller  561  by means of a lead  708  extending to a bond pad  709  provided along one side of substrate  526 . Movable structure  667  is electrically connected to controller  561  by a lead  711  extending to a bond pad  712  also provided on a side of substrate  526 . Bond pads  709  and  712  are electrically coupled by suitable wires or other leads (not shown) to controller  561 . Means in the form of a closed loop servo control system can optionally be included in controller  561  or related control electronics for monitoring the position of movable structure  667  relative to substrate  526 . For example, controller  561  can include a conventual algorithm of the type discussed above the respect to microactuator  507  for measuring the capacitance between comb fingers  682  of movable comb drives  663  and comb fingers  677  of stationary comb drives of  662 . 
     The structural components of first microactuator  653 , that is movable structure  667 , first and second springs  664  and  666  and first comb drives  662 , have the shape of a truncated fan when viewed in plan (see FIGS.  2  and  6 ). In this regard, such components resemble a truncated or foreshortened sector of a circle. Such components do not extend to the virtual pivot point of microactuator  653 , but instead are spaced radially outwardly from such virtual pivot point. As such, the virtual point of the microactuator  653  intersects the plane of substrate  526  at a point outside the confines of the components of microactuator  653  and, more specifically, outside the confines of movable structure  667 . Springs  664  and  666  and movable structure  667  subtend an angle about the virtual pivot point of microactuator  653  of less than 180 degrees and preferably less than 90 degrees. More preferably, springs  664  and  666  and movable structure  667  subtend an angle of approximately 45 degrees about such virtual pivot point. 
     Movable structure  667  is rotatable about the virtual pivot point of microactuator  653  in opposite first and second angular directions from its at-rest or intermediate position shown in  FIG. 2  in the same manner as discussed above with respect to microactuator  507 . In general, when movable structure  667  moves in a clockwise direction about such virtual pivot point, second comb drives  663  in first comb drive assemblies  656  of each set  658  and  659  move to their respective second positions. When movable structure is moved in an opposite counterclockwise direction about such virtual pivot point, second comb drives  663  in second comb drive assemblies  657  of each set  658  and  659  move to their respective second positions, as shown in FIG.  6 . 
     Reflector  506  is coupled to microactuator  653 . Specifically, the reflector  506  is carried by movable structure  667  in the same manner as discussed above with respect to microactuator  507  and extends perpendicularly from the plane of microactuator  653 . First and second spaced-apart pads  713  and  714  are included on movable structure  667  for receiving the reflector  506 . First pad  713  extends from inner radial end portions  681   a  of the second comb drives  663  of first set  658 . Second pad  714  extends from the end of shuttle  696  secured to first spring  664 . Pads  713  and  714  are included in the coupling means or coupler of microdevice  652  for connecting the reflector  506  to the microactuator  653 . 
     A counterbalance  726  is carried by substrate  526  and coupled to second comb drives  663  of first microactuator  653 . The counterbalance or counterbalancing means  726  optionally includes a second microactuator and preferably a MEMS-based microactuator of any suitable type. The counterbalance more preferably includes a rotary electrostatic microactuator or any other suitable electrostatic microactuator. In one preferred embodiment, shown in  FIGS. 2 and 6 , a balancing microactuator  727  substantially similar to first microactuator  653  is included in counterbalance  726 . Like reference numerals have been used in the drawings to describe like components of microactuators  653  and  727 . Stationary comb drive fingers or comb fingers  731  and movable comb drive fingers or comb fingers  732  of microactuator  727 , identified in  FIG. 6 , are substantially similar to the comb fingers  676  and  682  in second comb drive assembly  657  of first set  658  and the comb fingers  676  and  682  in first comb drive assembly  656  of second set  659  of microactuator  653 . Each of the stationary comb fingers  731  has an inner portion  691  and an outer portion  692 , and each of the movable comb fingers  732  has an inner portion  693  and an outer portion  694 . 
     In the same manner as discussed above with respect to first microactuator  653 , movable structure  667  of balancing microactuator  727  moves or rotates in first and second opposite angular directions about a virtual pivot point, identified as pivot point  723  in FIG.  2 . Pivot point  723  is generally located at the intersection of straight lines drawn from first and second springs  664  and  666 , when in their respective rest positions, and radial centerline  672  of the microactuator  727 . 
     Electrical means is included for driving second comb drives  534  of balancing microactuator  727  between their first and second positions and can include controller and voltage generator  561  used for controlling first microactuator  653 . Controller  561  is electrically coupled to balancing microactuator  727  in the same manner as discussed above with respect to first microactuator  653  by means of bond pads  709  and  712  of the balancing microactuator  727 . A suitable closed loop servo control system, such as one using a conventional algorithm of the type discussed above, can optionally be included in controller  561  or related control electronics for measuring the capacitance between comb fingers  677  and  682  of balancing microactuator  727  to monitor the position of the movable structure  667  of the balancing microactuator  727 . 
     Counterbalance  726  further includes a link  736  for coupling balancing microactuator  727  to first microactuator  653  and, more specifically, for coupling second comb drives  663  of the balancing microactuator  727  to second comb drives  663  of the first microactuator  653 . Link or levers assembly  736  is anchored to substrate  526  by a mount  737  formed from top wafer  668  and secured to the substrate  526  by silicon dioxide layer  669 . Link  736  includes a lever arm  738  having first and second end portions  738   a  and  738   b  and a central portion  738   c  (see FIG.  2 ). Lever arm  738  is pivotably coupled to mount  737  by means of a pivot assembly  741 , which is X-shaped in conformation when viewed in plan and is formed from first and second pivot arms  742  joined at their center to form a pivot point  743  for the pivot assembly. The pivot assembly  741  is elongate in shape, with the first ends of the pivot arms  742  joined in spaced-apart positions to mount  737  and the second ends of the pivot arms joined in spaced-apart positions to lever arm  738  at central portion  738   c . Each of the pivot arms  742  has a width and thickness similar to the width and thickness of spring members  698 . First and second sacrificial bars  744 , similar to sacrificial bars  701  discussed above, extend along each side of the pivot arms  742  for ensuring even etching of the desired rectangular cross section of the pivot arms. 
     First and second ends  738   a  and  738   b  of the level arm  738  are joined to the respective shuttles  696  of first microactuator  653  and balancing microactuator  727  by respective first and second coupling members or coupling springs  746  and  747  (see FIGS.  2  and  6 ). Springs  746  and  747  are similar to first and second springs  664  and  666  and are each formed from a spring member  748  substantially similar to spring member  698 . Each of the spring members  748  has one end secured to the respective end of lever arm  738  and the other end secured to a bracket  751  joined to the respective shuttle  696 . First and second sacrificial bars  752 , substantially similar to sacrificial bars  701  discussed above, extend along each side of each spring member  748  for the reasons discussed above. Lever arm  738 , pivot assembly  741 , first and second coupling springs  746  and  747  and brackets  751  are each formed from top wafer  668  and overlie substrate  526  by the distance of air gap  671 . 
     Counterbalance  726  optionally further includes one or more weights  756  carried by movable structure  667  of balancing microactuator  727  to offset or counterbalance the weight of reflector  506  mounted on the movable structure  667  of first actuator  653 . In one preferred embodiment, a platform  757  is formed between the back-to-back movable bars  681  in each of the first set  658  of comb drive assemblies and the second set of  659  of comb drive assemblies of balancing microactuator  727 . Each of the platforms  757  is formed from top wafer  668 . Weights  756  are secured to platform  575  by any suitable means such as an adhesive (not shown). Movable structures  667  of first microactuator  653  and balancing microactuator  727 , reflector  506 , weights  756  and link  736  are included in the movable framework  758  of balanced microdevice  652 . 
     In operation and use of microdevice  652 , each of first microactuator  653  and balancing microactuator  727  are preferably driven by controller  561  in the same manner as discussed above with respect to microactuator  507 . Movement of movable structure  667  of microactuator  653  and reflector  506  is obtained by providing suitable voltage potentials from controller  561  to first and second comb drive assemblies  656  and  657  of the microactuators  653  and  727 . 
     The offset and inclined comb drive fingers of second comb drive assemblies  656  and  657  contribute to the stability of first microactuator  653 . In this regard, the bending of first and second springs  664  and  666  during interdigitation of comb fingers  677  and  682  causes the springs  664  and  666  to shorten slightly and thus results in movable comb fingers  682  following a noncircular trajectory. The actual trajectory of comb fingers  682  during movement from their first to second positions is approximated by the equation
 
 R   1 (θ)=( R   p   −Aθ   2 ) sec (θ), 
 
where A is given by
 
 A =(18 R   p   2 +2 L   2 −3 LR   p )/30 L,  
 
with L being the length of spring members  698  and R p  being the distance from the virtual pivot of first microactuator  653  to outer radial end portions  698   b  of the spring members  698 .
 
     The complimentary inclination of first and second comb drive fingers  677  and  682  relative to respective comb drive bars  676  and  681  results in the comb fingers having a shape that compensates for the trajectory of the second comb drives  663 . As discussed above, first comb drive fingers  677  are inclined radially outwardly of the respective comb drive bar  676  and second comb drive fingers  862  are inclined radially inwardly at a equal angle relative to the respective comb drive bar  681 . Such cooperative inclination of the comb fingers contributes to each second comb drive finger  682  being more centered relative to the respective par of adjacent first comb drive fingers  677  during interdigitation of the first and second comb drive fingers  677  and  682 . Since the comb drive fingers remain more centered, radial stability is enhanced during interdigitation. 
     The offset alignment of second comb drive fingers  682  relative to first comb drive fingers  677  ensures that the second comb drive fingers  682  will be substantially centered on midpoint line  687 , as shown in  FIG. 7 , when the first and second comb drive fingers are fully interdigitated. When this is so, the derivative of the net side force between the comb fingers  677  and  682  is substantially minimized and the side stability is increased. The combination of inclined comb fingers and initial offset allows the radial stability of the comb fingers to be maximized throughout the full deflection range. It should be appreciated the invention is broad enough to cover microactuators having comb drive assemblies with comb fingers that are offset but not inclined or inclined but not offset. 
     The electrostatic forces exerted between the comb fingers of microactuator  653  remain relatively constant during rotation of movable structure  667 . In this regard, the varying of the lengths of comb fingers  682  along comb drive bars  681  in the first and second comb drive assemblies  662  and  663  adjacent radial centerline  672  and the varying of the lengths of inner portions  691  and  693  along the respective comb drive bars  676  and  681  in the first and second comb drive assemblies farthest from centerline  672  minimizes undesirable spikes or peaks in the electrostatic forces exerted between the respective first and second comb drives  662  and  663  during interdigitation of the respective comb fingers  677  and  682 . 
     In an exemplary illustration,  FIG. 8  shows second comb drive  663  of second comb drive assembly  657  of first set  658  in a partially interdigitated position between its first position shown in FIG.  5  and its second position shown in FIG.  6 . As can be seen therein, outer portion  692  of the stationary comb fingers  677  at outer radial portion  676   b  of first bar  676  is approximately half interdigitated between the inner portions  693  of adjacent movable comb fingers  682  at outer radial portion  681   b  of the second bar  681 . The amount of interdigitation between the outer portion  692  of stationary comb fingers  677  with the inner portion  693  of movable comb fingers  682  decreases in a substantially linear manner from the outer radial portion to the inner radial portion of such first and second comb drive assemblies  6565  and  657 . The amount of interdigitation between outer portion  694  of the movable comb fingers  682  and the inner portion  691  of adjacent stationary comb fingers  677  at the inner radial portion of the second comb drive assembly  657  illustrated in  FIGS. 5 and 8  is less than the amount of interdigitation between outer portion  692  of the stationary comb fingers  677  and the inner portion  693  of adjacent movable comb fingers  682  at the inner radial portion of such second comb drive assembly  657 . The amount of interdigitation between outer portion  694  and adjacent inner portions  691  decreases from the inner radial portion to the outer radial portion of such second comb drive assemblies  657 . 
     Thus, as can be seen from  FIG. 8 , outer portions  692  sequentially commence interdigitation between adjacent inner portions  693 , commencing at the outer radial portion of such second comb drive assembly  657  and continuing towards the inner radial portion of such second comb assembly  657 , during movement of the respective second comb drive  663  towards the respective first comb drive  662  and thereafter outer portions  694  sequentially commence interdigitation between adjacent inner portions  691 , commencing at the inner radial portion and continuing to the outer radial portion of such second comb drive assembly  657 , during further rotational movement of such second comb drive  663  about the virtual pivot point of first microactuator  653  towards the first comb drive  662  of such second comb drive assembly  657 . In this manner, any spike or peak in the engagement force resulting from an outer portion  692  or  694  interdigitating between the relatively wider inner portions  691  or  693  is spread throughout the interdigitation of a complimentary pair of first and second comb drives  662  and  663 . 
     Counterbalance  726  serves to inhibit undesirable movements of the second comb drives  663  in first microactuator  653 , and thus microreflector  506  carried thereby, in the direction of travel of those components from externally applied accelerations to microdevice  652 . As discussed above, first and second suspension members or springs  664  and  666  provide radial stiffness to first microactuator  653 . As such, springs  664  and  666  inhibit undesirable movements of the second comb drives  663  in the radial direction when forces or accelerations are externally applied to microdevice  652 . The counterbalance  726  particularly minimizes undesirable movements in an angular direction about the pivot point of first microactuator  653 . 
     Angular movements of movable structure  667  of first microactuator  653  about the virtual pivot point of the microactuator  653  are counterbalanced by opposite angular movements of the movable structure  667  of balancing microactuator  727  about the virtual pivot point  733 , shown in  FIG. 2 , of the microactuator  727 . Specifically, when second comb drive assemblies  657  of first microactuator  653  are driven by controller  561  from their first position to their second position, as shown in  FIG. 6 , second comb drive assemblies  657  of balancing microactuator  727  are moved from their first position to their third position. Similarly, a clockwise movement of movable structure  667  of first microactuator  653  is offset by a counterclockwise movement of movable structure  667  of balancing microactuator  727 . 
     The mass of reflector  506  mounted on movable structure  667  may be balanced by optional weights  756  mounted on movable structure  667  of balancing microactuator  727 . The mass of optional weights  756  is adjusted so that the line between the virtual pivot of the first microactuator  653  and the combined center of mass of movable structure  667  of first microactuator  653  and reflector  506  is parallel to the line between the virtual pivot  733  of balancing microactuator  727  and the combined center of mass of movable structure  667  of balancing microactuator  727  and optional weights  756 . The mass of optional weights  756  is also adjusted so that the product of the combined mass of movable structure  667  of first microactuator  653  and reflector  506  with the distance between the virtual pivot of first microactuator  653  and the combined center of mass of movable structure  667  of first microactuator  653  and reflector  506  is equal to the product of the combined mass of movable structure  667  of balancing microactuator  727  and optional balancing weights  756  with the distance between the virtual pivot  733  of balancing microactuator  727  and the combined center of mass of movable structure  667  of balancing microactuator  727  and optional weights  756 . Linear accelerations to device  652  then produce equal torques on both first microactuator  653  and balancing microactuator  727  and equal forces on the two ends  738   a  and  738   b  of link  738  on pivot assembly  741 . 
     If the perpendicular distances between the pivot point  743  and the coupling springs  748  are not equal, but instead have a ratio R, then the mass of optional weights  756  can be adjusted so that linear accelerations to device  652  produce torques on first microactuator  653  and balancing microactuator  727  that are not equal, but have the same ratio R. The force produced by linear accelerations acting on the mass of lever arm  738  may also be included when balancing the forces on the two ends  738   a  and  738   b  of pivot assembly  741 . 
     Other embodiments of the balanced microdevice of the present invention can be provided. Another balanced apparatus or microdevice  771  is shown in  FIGS. 9 and 10  for moving any suitable object or element. In one preferred embodiment, such an object is an optical element such as a collimating lens  503  carried by a lens substrate or block  515  having first and second end portions  515   a  and  515   b . In general, microdevice  771  serves to move collimating lens  503  and is balanced to inhibit undesirable movement of the collimating lens  503  and lens block  515  from externally applied accelerations to the device. In one preferred embodiment, balanced microdevice  771  includes a microactuator or motor  772  which is preferably a MEMS-based microactuator of any suitable type and more preferably an electrostatic microactuator similar to microactuator  508  described above. 
     Linear microactuator  772  can be constructed in the manner discussed above with respect to first microactuator  653  atop a planar substrate  773  that is substantially similar to substrate  526  discussed above. At least one and preferably a plurality of first and second comb drive assemblies  776  and  777 , which are preferably linear comb drive assemblies, are carried by substrate  773  and arranged on substrate  773  in first and second sets  778  and  779 . Each of the first and second comb drive assemblies  776  and  777  includes a first comb drive member or comb drive  781  mounted on substrate  773  and a second comb drive member or comb drive  782  overlying the substrate  773 . At least first and second spaced-apart suspension members or spring members  783  and  784  are included in microactuator  772  for supporting or suspending the second comb drives  782  over the substrate  773  and for providing stiffness to the second comb drives  794  in a direction along a longitudinal centerline  786  of the microactuator  782 . 
     The components of microactuator  772  are formed atop substrate  773  by a top layer or wafer substantially similar to top wafer  668  of first microactuator  653 . The top wafer is secured to substrate  773  in any suitable manner and is preferably fusion bonded to the substrate by means of a silicon dioxide layer (not shown). The components of microactuator  772  can be formed by any suitable means and are preferably etched from the top layer by any of techniques discussed above with respect to microactuator  508 . Second comb drives  782  are part of a movable portion or structure  787  that, together with springs  783  and  784 , is spaced above substrate  773  by an air gap, similar to air gap  671  discussed above with respect to first microactuator  653 , so as to be electrically isolated from substrate  773 . 
     First and second comb drive assemblies sets  778  and  779  optionally extend parallel to each other in symmetrical disposition relative to longitudinal centerline  786  of microactuator  772 . A single first comb drive assembly  776  and a single second comb drive assembly  777  are provided in each set  778  and  779  of comb drive assemblies. First comb drive  871  of each of first and second comb drive assemblies  776  and  777  is immovably secured to substrate  773  and has a longitudinally-extending truss or bar  791  having first and second portions  791   a  and  791   b . A plurality of comb drive fingers or comb fingers  792  extend from one side of bar  791  in longitudinally spaced-apart positions along the length of the bar. 
     Second comb drives  782  are spaced above substrate  773  so as to be movable relative to the substrate and first comb drives  781 . The second comb drives  782  have a construction similar to first comb drives  781  and, more specifically, are each formed with a longitudinally—extending truss or bar  796  having first and second end portions  796   a  and  796   b . The second comb drives  782  of each set  778  and  779  are disposed back-to-back and, as such, share a bar  796 . A plurality of comb drive fingers or comb fingers  797  extend from each side of each bar  796  to form the back-to-back second comb drives  782  of each set  778  and  779 . The comb fingers  797  on each side of bar  796  are longitudinally spaced apart along the length the bar  796 . 
     Comb fingers  792  and  797  are substantially similar in construction. Each of the comb fingers are preferably of the type disclosed in International Publication No. WO 00/62410 having an International Filing Date of Apr. 12, 2000 and as such are inclined and offset. As more fully disclosed International Publication No. WO 00/62410, each of the comb fingers is slightly inclined from a line extending normal to the respective bar  791  or  796 . In addition, when each of the comb drive assemblies  776  and  777  is in its rest position, movable comb fingers  797  are offset relative to a midpoint line extending between the adjacent pair of stationary comb fingers  792  into which such comb fingers  797  interdigitate. In addition to the foregoing, the comb fingers  792  and  797  in first set  778  of comb drive assemblies are similar in construction to certain of the comb fingers discussed above with respect to first microactuator  653 . More specifically, the comb fingers in first set  778  are each formed with a first or inner portion  801  and a second or outer portion  802 . The inner portion  801  of each such comb finger has a width greater than the width of the respective outer portion  802 . The comb fingers  792  and  797  in second set  779  of comb drive assemblies each have a constant width along the length thereof. 
     First and second springs  783  and  784  are substantially similar in construction to springs  664  and  666  discussed above and each include a single spring member  806  and first and second sacrificial bars  807  extending parallel to the spring member along each of the opposite sides of the spring member. Each spring member  806  has a first end portion  806   a  and an opposite second end portion  806   b . First end portion  806   a  of each spring members is coupled or secured to substrate  783  at an anchor  808  and second end portion  806   b  of each spring member is coupled or secured to second comb drives  782 . In this regard, an elongate bar or shuttle  809  is secured to the free second end portion  806   b  of each spring member  806 . Shuttle  809  extends substantially perpendicular to springs  783  and  784  when the springs are in their rest positions shown in FIG.  9 . The second end portion  796   b  of each movable bar  796  of the second comb drives  782  is perpendicularly joined to the portion of shuttle  809  extending between springs  783  and  784 . The shuttle  809  is part of the movable structure  787  of microactuator  772 . It should be appreciated that some of the first and second comb drive assemblies  776  and  777  of microactuator can be disposed outside of springs  783  and  784 . 
     Second comb drives  782  of each of first and second comb drive assemblies  776  and  777  are movable in a first direction from their first or intermediate positions shown in  FIG. 9 , in which comb fingers  792  and  797  are not substantially fully interdigitated, to a second position, in which the comb fingers  792  and  797  are substantially fully interdigitated. The second comb drives  782  are also movable from their first position in an opposite second direction to a third position, in which the comb fingers  792  and  797  are spaced apart and fully disengaged. The comb fingers of first comb drive assemblies  796  are shown in  FIG. 10  in the second position, in which the comb fingers are substantially fully interdigitated, while the comb fingers of second comb drives assemblies  777  are shown in  FIG. 10  in the third position, in which the comb fingers are spaced apart and fully disengaged. First and second springs  783  and  784  permit the movement of second comb drives  782  and provide longitudinal rigidity to shuttle  809  and a second comb drives so as to inhibit snap over between interdigitated comb fingers  792  and  797 . 
     The interdigitation of the comb drive fingers of first comb drive assembly  776  serves to move shuttle  809  and the remainder of movable structure  787  in a sideways direction substantially perpendicular to longitudinal centerline  786  to a first position relative to substrate  773 , as shown in FIG.  10 . The interdigitation of the comb drive fingers of second comb drive assemblies  777  serves to move shuttle  809  and the remainder of movable structure  787  in an opposition second direction to a second position relative the substrate  773  (not shown). Bumpers  811  are provided on the first end portions  796   a  of movable comb drive bars  796  and on shuttle  809  for engaging respective stops  812  formed on substrate  773  to limit the sideways movement of the second comb drives  782  and shuttle  809  and thus define the first and second positions of the shuttle  809  and the remainder of movable structure  787 . 
     Electrical means is included for driving second comb drives  782  and the remainder of movable structure  787  between their first and second positions. Such electrical means includes a controller, such as controller  561 . An electrical lead or trace  813  extends from first end portion  791   a  of each first comb drive  781  to a bond pad  814  for permitting electrical control signals to be supplied to the first comb drives  781 . An additional electrical lead or trace  816  extends from the first end portion  806   a  of the spring member  806  of first spring  783  to a bond pad  817  for permitting electrical control signals to be supplied to the movable second comb drives  782 . Bond pads  814  and  817  are electrically coupled by suitable wires or leads (not shown) to the controller  561 . Means in the form of a closed loop servo control system, such as the conventional algorithm discussed above, can optionally be included in controller  561  or related control electronics for measuring the capacitance between comb fingers  792  and  797  to monitor the position of the second comb drives  782  of microactuator  772 . 
     A counterbalance  821  is carried by substrate  773  and coupled to second comb drive  782  of microactuator  772 . In this regard, elongate shuttle  809  extends forwardly of microactuator  772  and is formed with a platform  822 . Counterbalance or counterbalancing means  821  includes a lever assembly or coupler  826  that is carried by substrate  773  and serves to couple collimating lens  503  and lens block  515 , or any other suitable movable member or optical element, to shuttle  809 . 
     Lever assembly  826  is formed from the top wafer disposed atop substrate  773  and includes an anchor or mount  827  rigidly secured to the substrate  773 . A lever arm  828  is provided and has opposite first and second ends portions  828   a  and  828   b  and a central portion  828   c . Central portion  828   c  of the lever arm is secured to mount  827  by a pivot assembly  829  that is substantially similar to pivot assembly  741  described above. In this regard, pivot assembly  829  has first and second pivot arms  831  joined at their center to form a pivot point  832 . First and second sacrificial bars  833  extends along each side of the pivot arms. One end of each of the pivot arms is joined to mount  827  and the other end of each of the pivot arms is joined to central portion  828   c  of lever arm  828 . 
     First end portion  828   a  of the lever arm is coupled to shuttle platform  822  by means of an additional pivot assembly  836  substantially identical to pivot assembly  829 . The pivot arms  831  of pivot assembly  836  form a pivot point  837  where they intersect at the center of the X-shaped pivot assembly  836 . A mounting platform  838  is formed at second end portion  828   b  of lever arm. First end portion  515   a  of lens block  515  is secured to platform  838  by any suitable means such as an adhesive. The lens block  515  is preferably aligned relative to lever assembly  826  such that the substrate  515  extends along the centerline of lever arm  828 . Lever arm  828  and pivot assemblies  829  and  836  of lever assembly  826  are spaced above substrate  773  by an air gap so as to be movable relative to the substrate. An optional weight  839  can be secured to shuttle platform  828  by any suitable means such as a adhesive (not shown). Movable structure  787 , collimating lens  503 , lens block  515 , lever assembly  826  and weight  839  are included in the movable framework  841  of balanced microdevice  771 . 
     In operation and use, first and second comb drive assemblies  776  and  777  of microactuator  772  are preferably driven by the controller  561  in the same manner as discussed above with respect to microactuator  508  to move collimating lens  503  or any other suitable object. As shown in  FIGS. 9 and 10 , movement of first comb drive assemblies  776  of the microactuator  772  to their second positions causes lever arm  828  to pivot in a counterclockwise direction and thus move collimating lens  503  upwardly relative to substrate  773 . Conversely, movement of second comb drive assemblies  777  from their first position to their second position results in lever arm  828  moving in a clockwise direction and thus collimating lens moving downwardly relative to substrate  773 . Pivot assembly  826  permits the lever arm  828  to pivot about pivot point  832  and pivot relative to mount  827 . Pivot assembly  836  pivotably couples lever arm  828  to shuttle  809  for accommodating such pivotal movement of the lever arm  828  about pivot point  832 . Since the amount of angular rotation of collimating lens  503  is substantially small, its upward and downward movement is substantially. It can thus be seen that movement of the second comb drives  782  of microactuator  772  in a first direction causes collimating lens  503  to move in a second direction substantially opposite to the first direction. 
     In a manner similar to counterbalance  726 , counterbalance  821  of second balance microdevice serves to inhibit undesirable movements of the second comb drives  782  of microactuator  772 , and thus collimating lens  503 , in the direction of travel of those components from externally applied accelerations to microdevice  771 . As discussed above, first and second springs  783  and  784  of microactuator  772  provide stiffness to second comb drives  782  along the longitudinal centerline  786  of microdevice  771 . Counterbalance  821  particularly inhibits undesirable movements of the second comb drives  782 , in a direction substantially perpendicular to centerline  786 , between the first, second and third positions of the comb drives. In this regard, the object or element being moved by microactuator  772 , in this instance collimating lens  503  and lens block  515 , serves as part of the counterbalance of microdevice  771 . Factors contributing to the counterbalancing of the microdevice of  771  include the aggregate mass of movable structure  787  and weight  839  relative to the aggregate mass of lens block  515  and collimating lens  503 , the location of the center of mass of movable structure  787  and weight  839  relative to the center mass of lens block  515  and collimating lens  503  and the length of first end portion  828   a  of lever arm  828  relative to the length of second end portion  828   b  of the lever arm  828 . The mass of framework  841  and the distance from pivot  832  to the framework center of mass may also be considered. 
     Another embodiment of the balanced microdevice of the present invention is shown in  FIGS. 11 and 12 . Microdevice  889  therein can be used for moving or rotating any suitable object or element such as collimating lens  503 . Balanced microdevice  889  has a rotary electrostatic microactuator and preferably a fan-shaped rotary electrostatic microactuator. A balanced microdevice  889  having a particularly preferred rotary electrostatic microactuator  891  is shown in  FIGS. 11 and 12 . Balanced rotary microactuator  891  is formed from a substrate  892  substantially similar to substrate  526 . A movable or rotatable member, in the exemplary embodiment shown as a platform  893 , overlies substrate  892 . A plurality of first and second comb drive assemblies  896  and  897  are carried by substrate  892  for rotating platform  893  in opposite first and second angular directions about an axis of rotation extending perpendicular to substrate  892  and shown as a pivot point  898  in  FIGS. 11 and 12 . Each of the first and second comb drive assembles  896  and  897  includes a first comb drive member or comb drive  901  mounted on substrate  892  and a second comb drive member or comb drive  902  overlying the substrate  892 . First and second spaced-apart springs  903  and  904  are included in microactuator  891  for supporting or suspending second comb drives  902  and platform  893  over the substrate  892  and for providing radial stiffness to such comb drives and platform. Second comb drives  902  and platform  893  are part of a movable portion or structure  906  of microactuator  892 . 
     Substrate  892  is substantially similar to substrate  526 . Platform  893 , first and second comb drive assemblies  896  and  897 , first and second springs  903  and  904  and the other components of microactuator  891  are formed atop substrate  892  by a second or top layer or wafer  907  substantially similar to top wafer  668  discussed above. The top layer or wafer  907  is preferably fusion bonded to substrate  892  by means of a silicon dioxide layer (not shown). The components of microactuator  891  are formed from top wafer  907  by any suitable means and preferably by any of the techniques discussed above. 
     At least one and preferably a plurality of first comb drive assemblies  896  are included in balanced rotary microactuator  891  and angularly disposed about pivot point  898  for driving movable structure  906  in a clockwise direction about the pivot point  898 . 
     At least one and preferably a plurality of second comb drive assemblies  897  are included in microactuator  891  for driving movable structure  906  in a counterclockwise direction about pivot point  898 . The comb drive assemblies of microactuator  891  are arranged in a first or inner radial set  911  symmetrically disposed about radial centerline  912  of microactuator  891  and in a second or outer radial set  913  symmetrically disposed about radial centerline  912 . Each of the comb drive assemblies  896  and  897  extends substantially radially from pivot point  898  and, in the aggregate, subtends an angle of approximately 180 degrees or less, preferably approximately 120 degrees or less and more preferably approximately 90 degrees. As such, microactuator  891  has a fan like shape when viewed in plan, as shown in  FIGS. 11 and 12 . The microactuator  891  has a base  916  extending substantially perpendicularly of radial centerline  912 , and pivot point  898  is disposed adjacent based  916 . The microactuator  891  has an arcuate outer radial extremity  917  resembling the arc of a circle centered on pivot point  898  and a radial dimension from pivot point  898  to outer radial extremity  917  ranging from 1000 to 2500 microns and preferably approximately 1600 microns. 
     Two first comb drive assemblies  869  and two second comb drive assembles  897  are included in inner set  911  of comb drive assemblies. The first comb drive  901  in each comb drive assembly of inner set  911  has a radially-extending bar  918  having a first of inner end portion  918   a  and a second or outer end portion  918   b . A plurality of comb drive fingers or comb fingers  918  extend from one side of the bar  918  in radially spaced-apart positions along the length of the bar. The second comb drive  902  in each comb drive assembly of inner set  911  is formed from a radially-extending bar  921  having a first or inner end portion  921   a  and a second or outer end portion  921   b . A plurality of comb drive fingers or comb fingers  922  extend from one side of the bar towards the respective first comb drive  901  in radially spaced-apart positions along the length of the bar. Comb fingers  919  and  922  can be of any suitable size and shape and are preferably arcuate in shape. In a preferred embodiment, piecewise linear segments are used to form the comb fingers  919  and  922  for approximating such an arcuate shape. 
     Although the comb fingers  919  and  922  can have a constant width along the length thereof, each of the comb fingers preferably has a first or inner portion  923  and a second or outer portion  924 . The inner portion  923  has a width greater than the width of outer portion  924  for reasons discussed above. As shown in  FIG. 11 , comb fingers  919  and  922  are partially interdigitated when in their first rest position. Specifically, outer portions  924  of stationary comb fingers  919  are interdigitated with outer portions  924  of movable comb fingers  922 . 
     The inner end portion  921   a  of the movable bar  921  spaced farthest from radial centerline  912  on each side of inner set  911  of first and second comb drive assemblies is joined to platform  893 . The outer end portion  921   b  of each of the movable bars  921  in inner set  911  is joined to a rigid shuttle  926  which is substantially arcuate in shape. The arcuate shuttle  926  is part of the movable structure  906  of balanced rotary microactuator  891 . 
     Although springs  903  and  904  can be of any suitable type, each of the springs preferably consists of a single beam-like member  927  having a first or inner end portion  927   a  and a second or outer end portion  927   b . The inner end portion  927   a  of each of the spring members is coupled to substrate  892  and, more specifically, is secured to a mount  928  that is formed from top wafer  907  and is rigidly joined to substrate  892 . The inner end portions  927   a  are each joined to the mount  928  at pivot point  898 . Each of the spring members  927  extends between two adjacent movable bars  921  and the outer end portion  927   b  of each spring member is joined to an end of arcuate shuttle  926 . First and second springs  903  and  904  are angularly spaced apart a distance of approximately 70 degrees and, when viewed together in plan, are substantially V-shaped. 
     A plurality of first and second comb drive assemblies  896  and  897  are included in outer set  913  of comb drive assemblies. More specifically, two first comb drive assemblies  896  and two second comb drive assemblies  897  are included in the outer set  913 . The first comb drive  901  in each comb drive assembly  896  and  897  of outer set  913  is formed from a radially-extending bar  931  having a first or inner end portion  931   a  and a second or outer end portion  931   b . A plurality of comb drive fingers or comb fingers  932  extend from one side of the stationary bar  931  in radially spaced-apart positions along the length of the bar. Each of the second comb drives  902  in outer set  913  is formed from a substantially radially-extending bar  933  having a first or inner end portion  933   a  and a second or outer end portion  933   b . A plurality of comb drive fingers of comb fingers  934  extend from one side of the movable bar  933  towards the respective first comb drive  901  in radially spaced-apart positions along the length of the bar  933 . 
     Although comb fingers  932  and  934  can be of any suitable size and shape, the comb fingers are preferably arcuate in shape and, like comb fingers  919  and  922 , are preferably formed from piecewise linear segments for approximating such an arcuate shape. Comb fingers  932  and  934  are not substantially interdigitated when in their first or rest position, shown in FIG.  11 . More specifically, the comb fingers  932  and  934  are disengaged in the rest or intermediate position of FIG.  11 . Comb fingers  919 ,  922 ,  932  and  934  can optionally be inclined and offset in the manner discussed above with respect to the comb fingers of first microactuator  653 . 
     The inner end portion  933   a  of each movable bar  933  is joined to arcuate shuttle  926  and is thus movable in unison with the movable bars  921  of inner set  911  of comb drive assembles. The second comb drives  902  of the first comb drive assembly  896  and the second comb drive assembly  897  symmetrically disposed relative to the radial centerline at the center of outer set  913  face away from each other. The movable bar  933  of such second comb drives  902  are interconnected by means of a platform  937  that is preferably joined to the outer end portions  933   b  of such movable bars. 
     Movable structure  906  is rotatable in first and second opposite angular directions above pivot point  898 . Movement of the second comb drives  902  of first comb drive assemblies  896  from their first positions, shown in  FIG. 11 , to their second positions, in which the respective comb fingers thereof are substantially fully interdigitated, results in movable structure  906  rotating in a clockwise direction about pivot point  898 . Similarly, movement of the second comb drives  902  of second comb drive assemblies  897  from their first positions, shown in  FIG. 11 , to their second positions, in which the comb fingers of such second comb drive assemblies are substantially fully interdigitated as shown in  FIG. 12 , results in movable structure  906  rotating in a counterclockwise position about pivot point  898 . When the second comb drives  902  of one of first and second comb drive assemblies  896  and  897  move to their second positions, the second comb drives  902  of the other of the comb drive assemblies  896  and  897  move to their third positions, in which the comb fingers thereof are spaced apart and fully disengaged. First comb drive assemblies  896  are shown in their third positions in FIG.  12 . Movable structure  906  is capable of rotating plus and minus two to ten degrees and preferably approximately six degrees in each direction, for an aggregate rotation between its extreme angular positions ranging from four to 20 degrees and preferably approximately 12 degrees. 
     Means is included within balanced rotary microactuator  891  for limiting the angular movement of movable structure  906  about pivot point  898 . In this regard, a bumper  938  extends radially outwardly from outer platform  937  and engages one of first and second stops  939  when movable structure  906  is in either of its first and second extreme angular positions about pivot point  898 . 
     The electrical means such as controller  561  can be utilized for driving second comb drives  902  between their first and second positions. First comb drives  901  of the first and second comb drive assemblies  896  and  897  of inner set  911  spaced farthest from radial centerline  912  and all of the first comb drives  901  of outer set  913  are electrically connected by means of leads  942  to at least one end and as shown first and second bond pads  943 . The first comb drives  901  of the first and second comb drive assemblies  896  and  897  of inner set  911  spaced closest to radial centerline  912  are connected at respective inner end portions  918   a  to respective first and second bond pads  944  disposed between first and second springs  903  and  904 . Mount  928  additionally serves as a bond pad for electrically connecting second comb drives  902  and movable structure  906  to controller  561 . Means in the form of a closed loop servo control system, for example a conventional algorithm of the type discussed above, can optionally be included in controller  561  or related control electronics for measuring the capacitance between comb fingers  919  and  922  and comb fingers  932  and  934  to monitor the position of movable structure  906  relative to substrate  892 . 
     Collimating lens  503  is coupled to movable structure  906  by means of platform  893 . Specifically, first end portion  515   a  of lens block  515  is secured to platform  893  by any suitable means such as an adhesive (not shown). The lens block  515  is centered on radial centerline  912  of balanced rotary microactuator  891  when movable structure  906  is in its rest position shown in FIG.  11 . 
     A counterbalance  946  is carried by substrate  892  and movable structure  906  and thus, second comb drives  902 . Counterbalance  946  includes a weight  947  secured to outer platform or coupler  937  by any suitable means such as an adhesive (not shown) and thus coupled to movable structure  906  and second comb drives  902 . The mass of weight  947  and its position on movable structure  906  are selected so that the center of mass of movable structure  906 , lens block  515 , collimating lens  503  and weight  947 , in the angular direction about pivot point  848 , is located substantially at the pivot point  848 . Movable structure  906 , lens block  515 , collimating lens  503  and weight  947  are collectively referred to as the movable framework  948  of balanced microdevice  889 . 
     In operation and use, the rotary microactuator  891  of balanced microdevice  889  can be used in substantially the same manner as microactuator  772  to move collimating lens  503  or any other suitable object. Rotation of movable structure  906  in its first and second opposite angular directions about pivot point  848  results in collimating lens  503  similarly rotating about pivot point  848 . Since the amount of angular rotation of collimating lens  503  is substantially small, the upward and downward movement of the collimating lens  503  is substantially linear. 
     Counterbalance  946  serves to limit undesirable movements of the collimating lens  503  about the axis of rotation of microactuator  891  when external accelerations are applied to microdevice  889 . 
     Another embodiment of the microdevice of the present invention is shown in  FIGS. 13 and 14 . Microdevice  950  shown herein, for moving any suitable object or element  952 , is preferably provided with a lever assembly and is preferably balanced. In one referred embodiment, such an element  952  is an optical element such as a shutter plate or light blocking member. For example, microdevice  950  can be used as a variable optical attenuator or an on-off shutter in an optical communication system. In this regard, microdevice  950  can be part of tunable laser of the type disclosed in U.S. patent application Ser. No. 09/728,212 filed Nov. 29, 2000, the entire content of which is incorporated herein by this reference. 
     In general, microdevice  950  includes a microactuator  954  that serves to move the optical element  952  in a large displacement. A lever assembly  956  including a pivot  958  and lever  960  is provided to couple together microactuator  954  and optical element  952 . The microdevice includes a movable portion  981  which causes lever  960  to pivot so as to move optical element  952  in a direction of travel. Element  952  is substantially mechanically balanced to inhibit undesirable movement of the element in response to externally applied accelerations or vibrations. 
     In one preferred embodiment, microactuator or motor  954  is preferably a MEMS-based microactuator of any suitable type and more preferably a linear electrostatic microactuator similar to microactuator  772  described above. Linear microactuator  954  can be constructed in the manner discussed above with respect to microactuator  772 , atop a planar substrate  962 , that is substantially similar to substrate  773  discussed above. In general, linear microactuator  954  includes at least one and preferably a plurality of first and second comb drive assemblies  972  and  974 , preferably linear comb drive assemblies, which are carried by substrate  962  and arranged on substrate  962  in first, second, third and fourth sets  964  through  968 . Each of the first and second comb drive assemblies  972  and  974  includes a first comb drive member or comb drive  976  mounted on substrate  962  and a second comb drive member or comb drive  978  overlying substrate  962 . At least first and second spaced-apart suspension members or spring members  977  and  979  are included in microactuator  954  for supporting or suspending the second comb drives  978  over substrate  962  and for providing stiffness to second comb drives  978  in a direction along a longitudinal centerline  965  of microactuator  954 . 
     The components of microactuator  954  are formed atop substrate  962  by a top layer or wafer substantially similar to top wafer  773  of microactuator  772 . The top wafer is secured to substrate  962  in any suitable manner and is preferably fusion bonded to the substrate by means of a silicon dioxide layer (not shown). The components of microactuator  954  can be formed by any suitable means and are preferably etched from the top layer by any of techniques discussed above with respect to microactuator  772 . Second comb drives  978  are part of a movable portion or structure  981  that, together with springs  977  and  979 , is spaced above substrate  962  by an air gap, similar to air gap  671  discussed above with respect to first microactuator  653 , so as to be electrically isolated from substrate  962 . 
     First and second comb drive assemblies sets  964  and  966  extend parallel to each other in substantially symmetrical disposition relative to longitudinal centerline  965  of microactuator  954 . Similarly, third and fourth comb drive assemblies sets  968  and  970  extend parallel to each other in substantially symmetrical disposition relative to longitudinal centerline  965  of microactuator  954 . A single first comb drive assembly  972  and a single second comb drive assembly  974  are provided in each comb drive assemblies set  964  through  968 . First comb drive  976  of each of first and second comb drive assemblies  972  and  974  is immovably secured to substrate  962  and has a longitudinally-extending truss or bar  981  having first and second portions  982   a  and  982   b . A plurality of comb drive fingers or comb fingers  984  extend from one side of bar  982  in longitudinally spaced-apart positions along the length of the bar. 
     Second comb drives  978  are spaced above substrate  962  so as to be movable relative to the substrate and first comb drives  976 . The second comb drives  978  have a construction similar to first comb drives  976  and, more specifically, are each formed with a longitudinally-extending truss or bar  980  having first and second end portions  980   a  and  980   b . The second comb drives  978  of each set  964  through  970  are disposed back-to-back and, as such, share a bar  980 . A plurality of comb drive fingers or comb fingers  986  extend from each side of each bar  980  to form the back-to-back second comb drives  978  of each set. The comb fingers  986  on each side of bar  980  are longitudinally spaced apart along the length the bar  980 . 
     Comb fingers  984  and  986  are substantially similar in construction. Each of the comb fingers  984  and  986  are preferably of the type disclosed in U.S. Pat. No. 6,384,510 and as such are inclined and offset. As more fully disclosed in U.S. Pat. No. 6,384,510, each of the comb fingers  984  and  986  is slightly inclined from a line extending normal to the respective bar  980  and  982 . In addition, when each of the comb drive assemblies  972  and  974  is in its rest position, movable comb fingers  986  are offset relative to a midpoint line extending between the adjacent pair of stationary comb fingers  984  into which such comb fingers  986  interdigitate. 
     First and second springs  977  and  979  are substantially similar in construction to springs  783  and  784  discussed above and each include a single spring member  985  and first and second sacrificial bars  987  extending parallel to the spring member along each of the opposite sides of the spring member. Each of springs  977  and  979  has a first end portion  985   a  and an opposite second end portion  985   b . First end portion  985   a  of each spring members is coupled or secured to substrate  962  and second end portion  985   b  of each spring member is coupled to second comb drives  978 . In this regard, an elongate bar or shuttle  990  is secured to the free second end portion  985   b  of each spring member. Shuttle  990  extends substantially perpendicular to springs  977  and  979  when the springs are in their rest positions shown in FIG.  13 . The second end portion  980   b  of each movable bar  980  of the second comb drives  978  is perpendicularly joined to shuttle  990 . 
     Shuttle  990  is part of the movable structure  981  of microactuator  954 . In particular, first and second comb drive assembly sets  964  and  966  are disposed on one same side of shuttle  990  in substantially symmetrical disposition with respect to the centerline  965  of microactuator  954 . Third and fourth comb drive assembly sets  968  and  970  are disposed on the opposite side of shuttle  990  in substantially symmetrical disposition with respect to centerline  965  of microactuator  954 . 
     Second comb drives  978  of each of first and second comb drive assemblies  972  and  974  are movable in a first direction from their first or intermediate positions shown in  FIG. 13 , in which comb fingers  984  and  986  are not substantially fully interdigitated, to a second position, in which the comb fingers are substantially fully interdigitated. The second comb drives  978  are also movable from their first position in an opposite second direction to a third position (not shown), in which the comb fingers  984  and  986  are spaced apart and fully disengaged. 
     First and second flexible springs  977  and  979  permits each of the movable comb drives  978  to move from a first or rest position shown in  FIG. 13 , in which comb fingers are not substantially fully interdigitated, to a second or actuated position shown in  FIG. 14 , in which comb fingers are substantially fully interdigitated. As used herein, the term “not substantially fully interdigitated” is broad enough to cover comb fingers which are fully disengaged as well as comb fingers which are partially interdigitated. Movement of second comb drives  978  to their respective second positions causes shuttle  990  to move substantially in a linear direction of travel relative to substrate  962 . 
     Electrical means is included for driving second comb drives  978  and the remainder of movable structure  981  between their first and second positions. Such electrical means includes a controller, such as controller  561 . An electrical lead or trace  996  extends from each first comb drive  972  to a bond pad  994  for permitting electrical control signals to be selectively supplied to appropriate first comb drives  972 . An additional electrical lead or trace  997  extends from the first end portion  985   a  of spring member  977  to a bond pad  995  for permitting electrical control signals to be supplied to the movable second comb drives  978 . Means in the form of a closed loop servo control system, such as the conventional algorithm discussed above, can optionally be included in controller or related control electronics for measuring the capacitance between comb fingers  984  and  986  to monitor the position of the second comb drives  978  of microactuator  954 . 
     Lever assembly  956  is coupled to microactuator  954  and includes a pivot assembly or pivot  958  and a lever arm or lever  960 . Pivot or pivot assembly  958  is X-shaped in conformation when viewed in plan and is formed from first and second pivot arms  1000  and  1002  which are joined at their center to form a pivot point  1004  of the pivot assembly  958 . Each of pivot arms  1000  and  1002  has a first end portion  1000   a  and  1002   a  joined to substrate  962  in spaced-apart positions and a second end portion  1000   b  and  1002   b  joined to lever arm  960  in spaced-apart positions. Each of the pivot arms  1000  and  1002  is capable of bending or flexing and preferably has a cross-sectional configuration, both in shape and dimensions, similar to springs  977  and  979 . Sacrificial bars  1003 , similar to sacrificial bars  987  discussed above, optionally extend along the side of pivot arms for ensuring even etching of the desired rectangular cross section of the pivot arms. Pivot assembly  958  permits lever  960  to pivot about pivot point  1004  in both clockwise and counterclockwise directions from a first or rest position shown in  FIG. 13  to a second or actuated position shown in FIG.  14 . 
     The elongate and substantially rigid lever  960  has a first extremity  960   a  coupled to microactuator  954  through flexural member  1006 , an opposite second extremity  960   b  coupled to an optical element  952 , and a third or central portion  960   c  coupled to pivot assembly  958 . Third portion  960   c  of lever  960  includes two extensions or couplers  1010  for coupling to second end portions  1000   b  and  1002   b  of each of first and second pivot arms  1000  and  1002  respectively. Lever  960  has a first length from the first extremity  960   a  to pivot point  1004  and a second length from the second extremity  960   b  to the pivot point  1004 . The ratio of the second length to the first length can be adjusted to permit suitable displacement of optical element  952  in both clockwise and counterclockwise directions. In one preferred embodiment, the first length is approximately 1100 microns and the second length is approximately 2500 microns. Such dimensions provide a lever ratio of about 2.3, that is optical element  952  will translate 2.3 times of the travel distance of shuttle  990 . Microactuator  954  permit shuttle  990  to travel at least a distance of approximately 90 microns in both forward and rearward directions, and thus moving element  952  in a direction of travel through a distance at least 200 microns in both clockwise and counterclockwise directions. 
     Flexible or bendable member  1006  is provided to couple first extremity  960   a  of lever  960  to microactuator  954 . Specifically, the elongate and substantially linear coupler  1006  has first end portion  1006   a  joined to first extremity  960   a  of lever  960  and an opposite second end portion  1006   b  joined to movable structure  982  of microactuator  954 . Coupler  1006  preferably has a cross sectional configuration, including width and thickness, similar to the configuration of springs  977  and  979  so as to permit bending thereof during movement of lever  960 . A rigid member  1008  is provided to couple flexible member  1006  to microactuator  954 . Specifically, rigid member  1008  is Z-shaped in conformation when viewed in plan and has first end portion  1008   a  coupled to second end portion  1006   b  of flexural member  1006  and second end portion  1008   b  coupled to bar  980  of second comb drive  978  of third comb drive assemblies set  968 . 
     Movable components of microdevice  954  are substantially mechanically balanced to inhibit undesirable movement of element  952  in the direction of travel of element  952  in response to externally applied forces to microdevice  950 . In this regard, mass of movable structure  981  of microactuator  954 , lever  960 , and element  952  of microdevice  950  are adjusted so that the torque in the clockwise direction about pivot point  1004  of pivot assembly  958  is substantially equal to the torque in the counterclockwise direction about such pivot point. Any means can be utilized to adjust the dimensions and mass of the movable components of microdevice  950  to achieve such mechanical balancing. For example, a counterbalance such as a weight or mass (not shown) can be attached to such movable components. Such a counterbalance is preferably carried by lever arm  960 . 
     Element  952  can be any optical element such as a light blocking element, shutter, lens, and filter. In one preferred embodiment, element  952  is a shutter plate fabricated on substrate  962  during fabrication of other components of microdevice  950 . As shown in  FIGS. 13 and 14 , shutter plate  952  has a generally planar rectangular attenuation surface, however, the shape and the topography of the attenuation surface can be modified to provide the desired level of attenuation and minimize power consumption. Shutter plate  952  as fabricated can be mounted to second extremity  960   b  of lever  960  by any suitable means. In one preferred embodiment, shutter plate  952  (shown as  952   b  in  FIGS. 13 and 14 ) is coupled to lever  960  in a plane substantially perpendicular to the plane of substrate  962 . As such, shutter plate  952   b  can attenuate an optical beam  953  that lies in a plane parallel to the plane of substrate  962  and travels in a path substantially perpendicular to the plane of the shutter disposition when in rest position, as shown in FIG.  14 . Shutter plate  952  (shown as  952   a  in phantom lines in  FIG. 13 ) can also be coupled to lever  960  in a plane parallel to the plane of substrate  962  shown in  FIG. 13  so as to at least partially overlie an opening (not shown) defined by substrate  962 . This disposition of shutter plate  952   a  attenuates an optical beam that passes through the opening in the substrate  962 . 
     In operation and use, microactuator  954  is electrically controlled by controller  561  to drive shuttle  990  in a forward direction (a downward direction in  FIG. 13 ) from its rest position shown in  FIG. 13  to its actuated position shown in FIG.  14 . Such movement of shuttle pushes flexural member  1006  forward which in turn rotates lever  960  in a counterclockwise direction about pivot point  1004  so as to pull element  952  in a rearward direction (an upward direction in  FIG. 14 ) to a second position shown in FIG.  14 . Similarly, microactuator  954  can be electrically controlled by controller  561  to pull shuttle  990  in a rearward direction (an upward direction in  FIG. 13 ) from its rest position shown in  FIG. 13  to a second position (not shown). Such movement of shuttle  990  pulls flexural member  1006  rearwardly which in turn rotates lever  960  in a clockwise direction about pivot point  1004  so as to push optical element  952  in a forward direction to a second position. In both instances, bendable flexural member  1006  and pivot arms  1000  and  1002  accommodate the pivoting of lever  960  about pivot point  1004 . The pivoting of lever  960  about pivot point  1004  in both clockwise and counterclockwise directions allows optical element  952  coupled to the second extremity  960   b  of lever  960  to move in both clockwise and counterclockwise directions. Stop  1006  is provided on substrate  962  to limit the maximum travel of lever  960 . The precise and variable control of motor  954  allows shutter plate  952  to dynamically attenuate the optical beam over the entire circular region of the beam or any predetermined portion of the beam. 
     The microdevice  950  of the present invention is suitable for use either as a variable optical attenuator or as an on-off shutter in an optical communication system. As such the microdevice of the present invention is advantageous over the prior art microdevices which have limitations in ability to divert all or portion of the optical beam and is susceptible to external accelerations or vibrations. The microdevice of the present invention is substantially mechanically balanced and thus provides the variable optical attenuator or shutter with substantial immunity to undesirable externally applied forces. Further, by adjusting the lever ratio of the device, the deflection of the device can be controlled. In one embodiment of the invention, the lever of the device is pivotable about the pivot point through an angle of at least five degrees in both clockwise and counterclockwise directions and the light blocking element or shutter plate is movable in the direction of travel through a distance of at least 200 microns in both clockwise and counterclockwise directions. The ability of large deflections allows the microdevice to be used in relatively large collimated, converging, or diverging optical beams, which results in reduced insertion loss compared to prior art devices. This is particularly useful in a tunable laser system employing an external cavity laser design where the output beam from such a system usually has a diameter of about 150 microns. Allowing for alignment tolerances, the output beam can be located in a circular region about 200 microns or more in diameter. To provide an attenuator for such a laser system, a shutter with a travel of at least 200 microns is desirable. The microdevice of the present invention can provide large structure deflections at least about 200 microns in both clockwise and counterclockwise directions and is thus suitable for use in such tunable laser systems. The microdevice of the present invention can be scaled larger or smaller to any suitable size so as to provide a low cost solution for commercial applications. 
     The microdevice of the present invention are not limited for use in tunable lasers, the telecommunications industry or optical apparatus, it being appreciated that the microdevice and microactuators disclosed herein can be used in a wide range of applications, in addition to those discussed herein, to move any suitable element or member. It should also be appreciated by those skilled in the art that it would be possible to modify the size, shape, appearance and methods of manufacture of various elements of the invention, or to include or exclude various elements, and stay within the scope and spirit of the present invention.