Patent Publication Number: US-2015070747-A1

Title: Display element reset using polarity reversal

Description:
TECHNICAL FIELD 
     This disclosure relates to electromechanical systems and devices. More specifically, the disclosure relates to resetting a movable element in an electromechanical system device, such as a mirror in an interferometric modulator (IMOD), to a consistent starting point or reset position. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     Electromechanical systems (EMS) include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components such as mirrors and optical films, and electronics. EMS devices or elements can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical and electromechanical devices. 
     One type of EMS device is called an interferometric modulator (IMOD). The term IMOD or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an IMOD display element may include a pair of conductive plates, one or both of which may be transparent and/or reflective, wholly or in part, and capable of relative motion upon application of an appropriate electrical signal. For example, one plate may include a stationary layer deposited over, on or supported by a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the IMOD display element. IMOD-based display devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with display capabilities. 
     In some implementations, the position of one plate in relation to another may reflect a specific wavelength of light. The plate may be moved to another position in order to reflect another wavelength of light. 
     SUMMARY 
     The systems, methods and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. 
     One innovative aspect of the subject matter described in this disclosure can be implemented in a circuit including a first electrode associated with a first voltage source, a second electrode associated with a second voltage source, a movable element, and a third electrode coupled with the movable element. In such implementations, a first capacitance is defined between the first electrode and the third electrode, and a second capacitance is defined between the second electrode and the third electrode. A capacitor is coupled between the second electrode and the third electrode. 
     In some implementations, the circuit can include a dielectric that can be positioned between the first electrode and the third electrode. 
     In some implementations, the first voltage source and the second voltage source are configured to switch in polarity with reference to each other. In some implementations, the movable element can be configured to move towards the first electrode in response to the switch in polarity of the first voltage source. 
     In some implementations, an electric field associated with the first electrode and the third electrode changes direction responsive to the switch in polarity between the first voltage source and the second voltage source. 
     In some implementations, the second capacitance can be larger than the first capacitance. 
     In some implementations, the second capacitance can be defined by a capacitance of the capacitor in parallel with an equivalent series capacitance of one or both of a first air gap and a dielectric. The first capacitance can be defined by an equivalent series capacitance of one or both of a second air gap and the movable element. 
     In some implementations, the second capacitance can be defined by a capacitance of the capacitor in parallel with an equivalent series capacitance of one or both of a first air gap and the movable element. The first capacitance can be defined by an equivalent series capacitance of one or both of a second air gap and a dielectric. 
     In some implementations, the movable element can include the third electrode and a mirror. The third electrode on the movable element can be positioned closer to the first electrode than the positioning of the mirror to the first electrode. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for moving a movable element to a reset position. In some implementations, the voltage source associated with an electrode can be switched in polarity. The planar surface of the movable element can move towards the electrode in response to the switch in polarity. 
     In some implementations, the movable element is moved to a reset position associated with a dielectric. In some implementations, the movable element can rest against the dielectric when in the reset position. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a circuit for moving a movable element of an electromechanical systems (EMS) device. The circuit can include: means for switching the polarity of a voltage associated with an electrode, and means for consistently resetting the movable element of the EMS device to the same reset position. In some implementations, the reset position is associated with a dielectric. In some implementations, the movable element rests against the dielectric when in the reset position. 
     Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Although the examples provided in this disclosure are primarily described in terms of EMS and MEMS-based displays the concepts provided herein may apply to other types of displays such as liquid crystal displays, organic light-emitting diode (“OLED”) displays, and field emission displays. Other features, aspects, and advantages will become apparent from the description, the drawings and the claims. Note that the relative dimensions of the following figures may not be drawn to scale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view illustration depicting two adjacent interferometric modulator (IMOD) display elements in a series or array of display elements of an IMOD display device. 
         FIG. 2  is a system block diagram illustrating an electronic device incorporating an IMOD-based display including a three element by three element array of IMOD display elements. 
         FIGS. 3A and 3B  are schematic exploded partial perspective views of a portion of an electromechanical systems (EMS) package including an array of EMS elements and a backplate. 
         FIG. 4  is an example of a system block diagram illustrating an electronic device incorporating an IMOD-based display. 
         FIG. 5  is a circuit schematic of an example of a three terminal IMOD. 
         FIG. 6A  is a circuit schematic illustrating capacitances of elements of display unit  540  of the circuit schematic of  FIG. 5 . 
         FIG. 6B  is a circuit schematic illustrating capacitances of the circuit schematic of  FIG. 6A . 
         FIG. 7  is a timing diagram for the circuit schematic of  FIG. 5 . 
         FIG. 8A  is an illustration of an example of a movable element in a first position. 
         FIG. 8B  is an illustration of an example of a movable element in a reset position. 
         FIG. 8C  is an illustration of an example of a movable element in a second position. 
         FIG. 9A  is an illustration of electric fields in the circuit schematic of  FIG. 5 . 
         FIG. 9B  is another illustration of electric fields in the circuit schematic of  FIG. 5 . 
         FIG. 10  is an example of another circuit schematic of a three terminal IMOD. 
         FIG. 11  is an example of another circuit schematic of a three terminal IMOD. 
         FIG. 12  is a flow diagram illustrating a method for moving a movable element to a reset position. 
         FIGS. 13A and 13B  are system block diagrams illustrating a display device that includes a plurality of IMOD display elements. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device, apparatus, or system that can be configured to display an image, whether in motion (such as video) or stationary (such as still images), and whether textual, graphical or pictorial. More particularly, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices such as, but not limited to: mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, Bluetooth® devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, facsimile devices, global positioning system (GPS) receivers/navigators, cameras, digital media players (such as MP3 players), camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), computer monitors, auto displays (including odometer and speedometer displays, etc.), cockpit controls and/or displays, camera view displays (such as the display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (such as in electromechanical systems (EMS) applications including microelectromechanical systems (MEMS) applications, as well as non-EMS applications), aesthetic structures (such as display of images on a piece of jewelry or clothing) and a variety of EMS devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes and electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art. 
     Interoferometric modulator (IMOD) displays may include a movable element, such as a mirror, that can be positioned at various points in order to reflect light at a specific wavelength. Some implementations of the subject matter described in this disclosure include driving a single-mirror IMOD to a consistent starting point. For example, moving the movable element to a specific position to reflect light at a particular wavelength may be easier and/or more reliable if the starting point is about the same every time the movable element needs to be moved. 
     In some implementations, the movable element may be moved to a consistent starting point, or reset position, by changing the voltage difference between electrodes, and therefore, changing the electric fields associated with the IMOD. For example, creating a voltage difference between a first electrode and second electrode that is larger than the voltage difference between the second and a third electrode can create a stronger electric field associated with the first and second electrodes. Additionally, a voltage applied to the first electrode may be reversed in polarity to change the direction of the electric field. Accordingly, the electric field can pull the movable element to the reset position. 
     Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Driving the movable element from a consistent starting point may improve precision of the movement of the mirror. Moreover, starting from a consistent starting point may eliminate the impact of hysteresis in the electromechanical response. For example, applying 5 Volts (V) to the movable element may move the movable element to a new position from an initial position. However, when the movable element starts from a different initial position, applying 5 V may move the movable element to a slightly different position. Additionally, returning the movable element to a consistent starting point can prevent the movable element from remaining in the same position for an extended period of time, and therefore, increase reliability. 
     An example of a suitable EMS or MEMS device or apparatus, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulator (IMOD) display elements that can be implemented to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMOD display elements can include a partial optical absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. In some implementations, the reflector can be moved to two or more different positions, which can change the size of the optical resonant cavity and thereby affect the reflectance of the IMOD. The reflectance spectra of IMOD display elements can create fairly broad spectral bands that can be shifted across the visible wavelengths to generate different colors. The position of the spectral band can be adjusted by changing the thickness of the optical resonant cavity. One way of changing the optical resonant cavity is by changing the position of the reflector with respect to the absorber. 
       FIG. 1  is an isometric view illustration depicting two adjacent interferometric modulator (IMOD) display elements in a series or array of display elements of an IMOD display device. The IMOD display device includes one or more interferometric EMS, such as MEMS, display elements. In these devices, the interferometric MEMS display elements can be configured in either a bright or dark state. In the bright (“relaxed,” “open” or “on,” etc.) state, the display element reflects a large portion of incident visible light. Conversely, in the dark (“actuated,” “closed” or “off,” etc.) state, the display element reflects little incident visible light. MEMS display elements can be configured to reflect predominantly at particular wavelengths of light allowing for a color display in addition to black and white. In some implementations, by using multiple display elements, different intensities of color primaries and shades of gray can be achieved. 
     The IMOD display device can include an array of IMOD display elements which may be arranged in rows and columns. Each display element in the array can include at least a pair of reflective and semi-reflective layers, such as a movable reflective layer (i.e., a movable layer, also referred to as a mechanical layer) and a fixed partially reflective layer (i.e., a stationary layer), positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap, cavity or optical resonant cavity). The movable reflective layer may be moved between at least two positions. For example, in a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively and/or destructively depending on the position of the movable reflective layer and the wavelength(s) of the incident light, producing either an overall reflective or non-reflective state for each display element. In some implementations, the display element may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when actuated, absorbing and/or destructively interfering light within the visible range. In some other implementations, however, an IMOD display element may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the display elements to change states. In some other implementations, an applied charge can drive the display elements to change states. 
     The depicted portion of the array in  FIG. 1  includes two adjacent interferometric MEMS display elements in the form of IMOD display elements  12 . In the display element  12  on the right (as illustrated), the movable reflective layer  14  is illustrated in an actuated position near, adjacent or touching the optical stack  16 . The voltage V bias  applied across the display element  12  on the right is sufficient to move and also maintain the movable reflective layer  14  in the actuated position. In the display element  12  on the left (as illustrated), a movable reflective layer  14  is illustrated in a relaxed position at a distance (which may be predetermined based on design parameters) from an optical stack  16 , which includes a partially reflective layer. The voltage V 0  applied across the display element  12  on the left is insufficient to cause actuation of the movable reflective layer  14  to an actuated position such as that of the display element  12  on the right. 
     In  FIG. 1 , the reflective properties of IMOD display elements  12  are generally illustrated with arrows indicating light  13  incident upon the IMOD display elements  12 , and light  15  reflecting from the display element  12  on the left. Most of the light  13  incident upon the display elements  12  may be transmitted through the transparent substrate  20 , toward the optical stack  16 . A portion of the light incident upon the optical stack  16  may be transmitted through the partially reflective layer of the optical stack  16 , and a portion will be reflected back through the transparent substrate  20 . The portion of light  13  that is transmitted through the optical stack  16  may be reflected from the movable reflective layer  14 , back toward (and through) the transparent substrate  20 . Interference (constructive and/or destructive) between the light reflected from the partially reflective layer of the optical stack  16  and the light reflected from the movable reflective layer  14  will determine in part the intensity of wavelength(s) of light  15  reflected from the display element  12  on the viewing or substrate side of the device. In some implementations, the transparent substrate  20  can be a glass substrate (sometimes referred to as a glass plate or panel). The glass substrate may be or include, for example, a borosilicate glass, a soda lime glass, quartz, Pyrex, or other suitable glass material. In some implementations, the glass substrate may have a thickness of 0.3, 0.5 or 0.7 millimeters, although in some implementations the glass substrate can be thicker (such as tens of millimeters) or thinner (such as less than 0.3 millimeters). In some implementations, a non-glass substrate can be used, such as a polycarbonate, acrylic, polyethylene terephthalate (PET) or polyether ether ketone (PEEK) substrate. In such an implementation, the non-glass substrate will likely have a thickness of less than 0.7 millimeters, although the substrate may be thicker depending on the design considerations. In some implementations, a non-transparent substrate, such as a metal foil or stainless steel-based substrate can be used. For example, a reverse-IMOD-based display, which includes a fixed reflective layer and a movable layer which is partially transmissive and partially reflective, may be configured to be viewed from the opposite side of a substrate as the display elements  12  of  FIG. 1  and may be supported by a non-transparent substrate. 
     The optical stack  16  can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer, and a transparent dielectric layer. In some implementations, the optical stack  16  is electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate  20 . The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals (e.g., chromium and/or molybdenum), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, certain portions of the optical stack  16  can include a single semi-transparent thickness of metal or semiconductor which serves as both a partial optical absorber and electrical conductor, while different, electrically more conductive layers or portions (e.g., of the optical stack  16  or of other structures of the display element) can serve to bus signals between IMOD display elements. The optical stack  16  also can include one or more insulating or dielectric layers covering one or more conductive layers or an electrically conductive/partially absorptive layer. 
     In some implementations, at least some of the layer(s) of the optical stack  16  can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having ordinary skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer  14 , and these strips may form column electrodes in a display device. The movable reflective layer  14  may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack  16 ) to form columns deposited on top of supports, such as the illustrated posts  18 , and an intervening sacrificial material located between the posts  18 . When the sacrificial material is etched away, a defined gap  19 , or optical cavity, can be formed between the movable reflective layer  14  and the optical stack  16 . In some implementations, the spacing between posts  18  may be approximately 1-1000 μm, while the gap  19  may be approximately less than 10,000 Angstroms (A). 
     In some implementations, each IMOD display element, whether in the actuated or relaxed state, can be considered as a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer  14  remains in a mechanically relaxed state, as illustrated by the display element  12  on the left in  FIG. 1 , with the gap  19  between the movable reflective layer  14  and optical stack  16 . However, when a potential difference, i.e., a voltage, is applied to at least one of a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding display element becomes charged, and electrostatic forces pull the electrodes together. If the applied voltage exceeds a threshold, the movable reflective layer  14  can deform and move near or against the optical stack  16 . A dielectric layer (not shown) within the optical stack  16  may prevent shorting and control the separation distance between the layers  14  and  16 , as illustrated by the actuated display element  12  on the right in  FIG. 1 . The behavior can be the same regardless of the polarity of the applied potential difference. Though a series of display elements in an array may be referred to in some instances as “rows” or “columns,” a person having ordinary skill in the art will readily understand that referring to one direction as a “row” and another as a “column” is arbitrary. Restated, in some orientations, the rows can be considered columns, and the columns considered to be rows. In some implementations, the rows may be referred to as “common” lines and the columns may be referred to as “segment” lines, or vice versa. Furthermore, the display elements may be evenly arranged in orthogonal rows and columns (an “array”), or arranged in non-linear configurations, for example, having certain positional offsets with respect to one another (a “mosaic”). The terms “array” and “mosaic” may refer to either configuration. Thus, although the display is referred to as including an “array” or “mosaic,” the elements themselves need not be arranged orthogonally to one another, or disposed in an even distribution, in any instance, but may include arrangements having asymmetric shapes and unevenly distributed elements. 
       FIG. 2  is a system block diagram illustrating an electronic device incorporating an IMOD-based display including a three element by three element array of IMOD display elements. The electronic device includes a processor  21  that may be configured to execute one or more software modules. In addition to executing an operating system, the processor  21  may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application. 
     The processor  21  can be configured to communicate with an array driver  22 . The array driver  22  can include a row driver circuit  24  and a column driver circuit  26  that provide signals to, for example a display array or panel  30 . The cross section of the IMOD display device illustrated in  FIG. 1  is shown by the lines  1 - 1  in  FIG. 2 . Although  FIG. 2  illustrates a 3×3 array of IMOD display elements for the sake of clarity, the display array  30  may contain a very large number of IMOD display elements, and may have a different number of IMOD display elements in rows than in columns, and vice versa. 
       FIGS. 3A and 3B  are schematic exploded partial perspective views of a portion of an EMS package  91  including an array  36  of EMS elements and a backplate  92 .  FIG. 6A  is shown with two corners of the backplate  92  cut away to better illustrate certain portions of the backplate  92 , while  FIG. 6B  is shown without the corners cut away. The EMS array  36  can include a substrate  20 , support posts  18 , and a movable layer  14 . In some implementations, the EMS array  36  can include an array of IMOD display elements with one or more optical stack portions  16  on a transparent substrate, and the movable layer  14  can be implemented as a movable reflective layer. 
     The backplate  92  can be essentially planar or can have at least one contoured surface (e.g., the backplate  92  can be formed with recesses and/or protrusions). The backplate  92  may be made of any suitable material, whether transparent or opaque, conductive or insulating. Suitable materials for the backplate  92  include, but are not limited to, glass, plastic, ceramics, polymers, laminates, metals, metal foils, Kovar and plated Kovar. 
     As shown in  FIGS. 6A and 6B , the backplate  92  can include one or more backplate components  94   a  and  94   b , which can be partially or wholly embedded in the backplate  92 . As can be seen in  FIG. 6A , backplate component  94   a  is embedded in the backplate  92 . As can be seen in  FIGS. 6A and 6B , backplate component  94   b  is disposed within a recess  93  formed in a surface of the backplate  92 . In some implementations, the backplate components  94   a  and/or  94   b  can protrude from a surface of the backplate  92 . Although backplate component  94   b  is disposed on the side of the backplate  92  facing the substrate  20 , in other implementations, the backplate components can be disposed on the opposite side of the backplate  92 . 
     The backplate components  94   a  and/or  94   b  can include one or more active or passive electrical components, such as transistors, capacitors, inductors, resistors, diodes, switches, and/or integrated circuits (ICs) such as a packaged, standard or discrete IC. Other examples of backplate components that can be used in various implementations include antennas, batteries, and sensors such as electrical, touch, optical, or chemical sensors, or thin-film deposited devices. 
     In some implementations, the backplate components  94   a  and/or  94   b  can be in electrical communication with portions of the EMS array  36 . Conductive structures such as traces, bumps, posts, or vias may be formed on one or both of the backplate  92  or the substrate  20  and may contact one another or other conductive components to form electrical connections between the EMS array  36  and the backplate components  94   a  and/or  94   b . For example,  FIG. 3B  includes one or more conductive vias  96  on the backplate  92  which can be aligned with electrical contacts  98  extending upward from the movable layers  14  within the EMS array  36 . In some implementations, the backplate  92  also can include one or more insulating layers that electrically insulate the backplate components  94   a  and/or  94   b  from other components of the EMS array  36 . In some implementations in which the backplate  92  is formed from vapor-permeable materials, an interior surface of backplate  92  can be coated with a vapor barrier (not shown). 
     The backplate components  94   a  and  94   b  can include one or more desiccants which act to absorb any moisture that may enter the EMS package  91 . In some implementations, a desiccant (or other moisture absorbing materials, such as a getter) may be provided separately from any other backplate components, for example as a sheet that is mounted to the backplate  92  (or in a recess formed therein) with adhesive. Alternatively, the desiccant may be integrated into the backplate  92 . In some other implementations, the desiccant may be applied directly or indirectly over other backplate components, for example by spray-coating, screen printing, or any other suitable method. 
     In some implementations, the EMS array  36  and/or the backplate  92  can include mechanical standoffs  97  to maintain a distance between the backplate components and the display elements and thereby prevent mechanical interference between those components. In the implementation illustrated in  FIGS. 3A and 3B , the mechanical standoffs  97  are formed as posts protruding from the backplate  92  in alignment with the support posts  18  of the EMS array  36 . Alternatively or in addition, mechanical standoffs, such as rails or posts, can be provided along the edges of the EMS package  91 . 
     Although not illustrated in  FIGS. 3A and 3B , a seal can be provided which partially or completely encircles the EMS array  36 . Together with the backplate  92  and the substrate  20 , the seal can form a protective cavity enclosing the EMS array  36 . The seal may be a semi-hermetic seal, such as a conventional epoxy-based adhesive. In some other implementations, the seal may be a hermetic seal, such as a thin film metal weld or a glass frit. In some other implementations, the seal may include polyisobutylene (PIB), polyurethane, liquid spin-on glass, solder, polymers, plastics, or other materials. In some implementations, a reinforced sealant can be used to form mechanical standoffs. 
     In alternate implementations, a seal ring may include an extension of either one or both of the backplate  92  or the substrate  20 . For example, the seal ring may include a mechanical extension (not shown) of the backplate  92 . In some implementations, the seal ring may include a separate member, such as an O-ring or other annular member. 
     In some implementations, the EMS array  36  and the backplate  92  are separately formed before being attached or coupled together. For example, the edge of the substrate  20  can be attached and sealed to the edge of the backplate  92  as discussed above. Alternatively, the EMS array  36  and the backplate  92  can be formed and joined together as the EMS package  91 . In some other implementations, the EMS package  91  can be fabricated in any other suitable manner, such as by forming components of the backplate  92  over the EMS array  36  by deposition. 
       FIG. 4  is an example of a system block diagram illustrating an electronic device incorporating an IMOD display element. Moreover,  FIG. 4  depicts an implementation of the row driver circuit  24  and the column driver circuit  26  of array driver  22  that provide signals to, for example the display array or panel  30 , as previously discussed. 
     As an example, display module  450  in the fourth row may be provided a row signal and a common signal from row driver circuit  24 . Display module  450  may also be provided a column signal from column driver circuit  26 . The implementation of display module  450  may include a variety of different designs. In some implementations, display module  450  may include a transistor with its gate coupled to the row signal and the column signal provided to the drain. In an implementation, each display module  450  may include an IMOD display element. The common signal may provide a bias to other components within display module  450 . In some implementations, display module  450  may have multiple common signals. 
       FIG. 5  is a circuit schematic of an example of a three terminal IMOD. In some implementations, the circuit of  FIG. 5  may be display module  450  of  FIG. 4 . The circuit of  FIG. 5  includes a switch implemented as an n-type metal oxide semiconductor (NMOS) transistor M 1   510 . The gate of transistor M 1   510  is coupled to V row    530 , which may be provided by row driver circuit  24  of  FIG. 4 . Transistor M 1   510  is also coupled to V column    520 , which may be provided by column driver circuit  26  of  FIG. 4 . The circuit of  FIG. 5  also includes display unit  540 . 
     In an implementation, display unit  540  may include three terminals or electrodes: V bias    555 , V d    560 , and V com    565 . Display unit  540  may also include movable element  570 , dielectric  575 , and capacitor  580 . Movable element  570  may include a mirror. In the implementation of  FIG. 5 , capacitor  580  is coupled between V d  electrode  560  and V com  electrode  565 . In another implementation, capacitor  580  may be coupled between V bias  electrode  555  and V d  electrode  560 . Movable element  570  may be coupled with the V d  electrode  560 . Additionally, in some implementations, air gap  585  may be between V bias  electrode  555  and V d  electrode  560 . Air gap  590  may be between V d  electrode  560  and V com  electrode  565 . 
     In some implementations, display unit  540  may include multiple capacitors. For example, instead of a single capacitor  580 , multiple capacitors may be used. 
       FIG. 6A  is a circuit schematic illustrating capacitances of elements of display unit  540  of the circuit schematic of  FIG. 5 . In  FIG. 6A , capacitance C 1   650  is associated with capacitor  580  of  FIG. 5 . Capacitance C 5   610  is associated with dielectric  575 . Capacitance C 4   620  is associated with air gap  585 . Capacitance C 3   630  is associated with movable element  570 . Capacitance C 2   640  is associated with air gap  590 . 
       FIG. 6B  is a circuit schematic illustrating capacitances of the circuit schematic of  FIG. 6A .  FIG. 6B  shows the equivalent capacitances between the electrodes. In  FIG. 6B , capacitance C 6   650  is the equivalent series capacitance of capacitance C 5   610  (i.e., the capacitance associated with dielectric  575 ) and capacitance C 4   620  (i.e., the capacitance associated with air gap  585 ). That is, capacitance C 6   650  is the capacitance between V bias  electrode  555  and V d  electrode  560 . Capacitance C 7   660  is the equivalent capacitance of capacitance C 1   650  (i.e., the capacitance associated with capacitor  580 ) in parallel with the equivalent series capacitance of capacitance C 3   630  (i.e., the capacitance associated with the movable element) and capacitance C 2   640  (i.e., the capacitance associated with air gap  590 ). That is, capacitance C 7   660  is the capacitance between V d  electrode  560  and V com  electrode  565 . Accordingly, when transistor M 1   510  is turned off (i.e., V row  is biased to turn transistor M 1   510  off), the model of capacitances of display unit  540  in  FIG. 6B  acts as a capacitor divider, and therefore, the voltage on V d  electrode  560  is determined by the change in V bias  electrode  555  and V com  electrode  565 , and the capacitances of C 6   650  and C 7   660 . In some implementations, if capacitance C 1   650  (i.e., the capacitance associated with capacitor  580 ) is larger compared to the other capacitances, then capacitance C 7   660  may be larger than capacitance C 6   660 . If capacitance C 7   660  is sufficiently larger than capacitance C 6   650  then the voltage associated with V d  electrode  560  may remain relatively constant, or slightly change, despite a voltage associated with another electrode changing, for example, V bias  electrode  555 . As an example, the capacitance C 1   650  may be approximately 50 to 200 femtofarads (fF) and the remaining capacitances may range from approximately 10 to 200 fF. 
     In some implementations, air gap  585  or air gap  590  may not be present. For example, as discussed later herein, movable element  570  may be configured to move towards an electrode and rest against a dielectric. Accordingly, air gaps  585  and  590  are variable, and may disappear, or reduce in size, in some implementations. Therefore, capacitance C 6   650  or capacitance C 7   660  may not include capacitances for air gap  585  or air gap  590 , respectively. 
     In an implementation, the voltages applied to V bias  electrode  555  and V com  electrode  565  may be biased such that movable element  570  may be moved. For example, in one implementation, movable element  570  may be pulled by an electric field towards V bias  electrode  555  or V com  electrode  565  to a consistent starting point or reset position. In another implementation, movable element  570  may be pulled to rest against dielectric  575  to provide a consistent starting point or reset position. 
     In particular, the direction of the electric fields induced by external biases associated with V bias  electrode  555  and/or V com  electrode  565  may be switched by reversing the polarity of V bias  electrode  555  and/or V com  electrode  565 . A change in voltage on V bias  electrode  555  and/or V com  electrode  565  may change the voltage difference between V bias  electrode  555  and V com  electrode  565  with V d  electrode  560 . A larger voltage difference can provide a larger electric field which can move movable element  570 . Therefore, adjusting the biases may move movable element  570  to a consistent starting or reset position before moving movable element  570  to a new position to provide color at a different wavelength. 
     For example, V bias  electrode  555  may be biased at 3 V and V com  electrode  565  may be biased at 0 V. Transistor M 1   510  may be turned off, and therefore, V d  electrode  560  may be floating, for example, at a positive voltage previously applied while transistor M 1   510  was turned on, such as 2 V. To reverse the polarity of V bias  electrode  555  in relation to V com  electrode  565 , the voltage bias of V bias  electrode  555  may be switched to −3 V and the voltage bias of V com  electrode  565  may remain at 0 V. If capacitance C 7   660  (i.e., the capacitance between V d  electrode  560  and V com  electrode  565 ) is sufficiently larger than capacitance C 6   650  (i.e., the capacitance between V bias  electrode  555  and V d  electrode  560 ), then the voltage at V d  electrode  560  may be held relatively constant (e.g., remain at approximately 2 V), and therefore, the voltage difference between V d  electrode  560  and V com  electrode  565  is relatively unchanged (i.e., approximately 2 V difference between 2 V for V d  electrode  560  and 0 V for V com  electrode  565 ). However, the voltage difference between V bias  electrode  555  and V d  electrode  560  is larger because though V d  electrode  560  stays relatively constant, or only slightly changes, the bias of the power supply associated with V bias  electrode  555  has switched to −3 V. Accordingly, the electric field between V d  electrode  560  and V bias  electrode  555  is larger than the electric field between V d  electrode  560  and V com  electrode  565 . Additionally, the direction of the electric field between V d  electrode  560  and V bias  electrode  555  has switched because V bias  electrode  555  switched from 3 V to −3 V. Therefore, movable element  570  may be pulled up because the electric field between V d  electrode  560  and V bias  electrode  555  is larger and in the opposite direction of the electric field between V d  electrode  560  and V com  electrode  565 . In some implementations, movable element  570  may be pulled up, and rest against, dielectric  575 . That is, dielectric  575  may act as a “stop” for movable element  570 , and therefore, provide a reset position or consistent starting point for movable element  570 . 
       FIG. 7  is a timing diagram for the circuit schematic of  FIG. 5 . In  FIG. 7 , V com    705  is associated with a power supply coupled with V com  electrode  565 , and is biased at 0 V. V bias    710  is associated with a power supply coupled with V bias  electrode  555 . V bias    710  toggles between 3 V and −3 V. V row    715  is associated with V row    540 , and therefore, controls whether transistor M 1   530  is turned on or off. V column    720  is associated with V column    520 . V d    725  is associated with V d  electrode  560 . In an implementation, when M 1   530  is turned on, V column    720  is applied to V d  electrode  560 . 
     The timing diagram of  FIG. 7  illustrates reversing the polarity of V bias  relative to V com  to move movable element  570  to a consistent starting position or reset position. For example, at time  740 , V bias  is 3 V, V d  is 2 V, and V com  is 0 V. Accordingly, the electric field between V bias  electrode  555  and V d  electrode  560  is pointed downward (i.e., from high potential to low potential). Likewise, the electric field between V d  electrode  560  and V com  electrode  565  is also pointed downward. The voltage difference between V bias  and V d  is 1 V. The voltage difference between V d  and V com  is 2 V. 
     However, at time  735 , the polarity of V bias  is reversed by changing the voltage from a positive voltage (i.e., 3 V in  FIG. 7 ) to a negative voltage (i.e., −3 V) and maintaining V com  at 0 V. Since V row  is low, transistor M 1   510  is turned off, and therefore, V d  electrode  560  is floating, for example, at a previously applied 2 V rather than being driven by V column    720 . However, if capacitance C 7   660  is sufficiently larger than capacitance C 6   650 , at time  735 , V d    725  may only slightly drop in voltage when V bias  switches polarity. For example, V d    725  may change to 1.5 V from 2 V, due to the capacitor divider model, as previously discussed. Accordingly, the electric field between V d  electrode  560  and V com  electrode  565  remains relatively the same because V com  is constant at 0 V and V d  has only slightly dropped to 1.5 V (i.e., a 1.5 V difference between V d  and V com ) from 2 V. Additionally, the electric field remains pointing downward (i.e., from high to low potential). However, since V bias  has switched to −3 V from 3V, and V d  is at 1.5 V, the electric field between V bias  electrode  555  and V d  electrode  560  switches direction and points upward. Additionally, the voltage difference between V bias  electrode  555  and V d  electrode is 4.5 V (i.e., 4.5 V difference between V bias  at −3 V and V d  at 1.5 V). Accordingly, the electric field between V bias  and V d  (i.e., the electric field pointing upward) may be stronger than the electric field between V d  and V com  (i.e., the electric field pointing downward) because the voltage difference between V bias  electrode  555  and V d  electrode  560  (i.e., a 4.5 V difference) is much larger than the voltage difference between V d  electrode  560  and V com  electrode  565  (i.e., a 1.5 V difference). Therefore, movable element  570  may be pulled upwards by the stronger electric field. For example, in  FIG. 7 , movable element position  730  represents the position of movable element  570 . At time  735 , movable element  570  may be moved to the reset position (e.g., up to dielectric  575 ) at 450 nm. 
     As an example,  FIG. 8A  is an illustration of an example of movable element  570  in a first position, for example, at time  740 .  FIG. 9A  is an illustration of electric fields in the circuit schematic of  FIG. 8 , for example, at time  740 . As previously discussed, electric field  905  (i.e., the electric field between V bias  electrode  555  and V d  electrode  560 ) and electric field  910  (i.e., the electric field between V d  electrode  560  and V com  electrode  565 ) both point downward, or towards V com  electrode  565 .  FIG. 8B  is an illustration of an example of movable element  570  in a reset position, for example, at time  735 . In  FIG. 8B , movable element  570  has been pulled towards V bias  electrode  555  and rests against dielectric  575 . As previously discussed, movable element  570  may be pulled towards V bias  electrode  555  because the electric field between V bias  electrode  555  and V d  electrode  560  (i.e., electric field  905 ) switches direction and points upward. For example, in  FIG. 9B , at time  735 , electric field  905  is stronger than the downward pointing electric field between V d  electrode  560  and V com  electrode  565  (i.e., electric field  910 ). In  FIG. 9B , electric field  905  points upward rather than downward as in  FIG. 9A . As previously discussed, the stronger and reversed electric field  905  may pull movable element  570  to the reset position in  FIG. 8B . 
     After movable element  570  has been moved to the reset position, for example at time  740 , movable element  570  may subsequently be moved to a new position.  FIG. 8C  is an illustration of an example of movable element  570  being moved to a new position at time  845 . In  FIG. 7 , at time  745 , V row    715  goes high (i.e., to 1 V) and turns on transistor M 1   510 . Accordingly, V d  electrode  560  is no longer floating. Rather, V column    720  is applied to V d    725 . As such, movable element  570  may move a distance from the reset position associated with an application of the voltage associated with V column    720 . For example, in  FIG. 7 , movable element position  730  at time  745  is associated with 175 nm. After movable element  570  has been set to the new position, V row    715  goes low, and therefore, V d  electrode  560  is undriven and floating. Before moving movable element  570  to another position, movable element  570  may be moved back to the reset position (e.g., towards V bias  electrode  555 ). 
     In some implementations, both V bias  electrode  555  and V com  electrode  565  may change in voltage. For example, in one implementation, V bias  electrode  555  may switch from a positive to a negative voltage and V com  electrode  565  may switch from a negative to a positive voltage. In another implementation, the voltages applied to V com  electrode  565  and V bias  electrode  555  may both be positive voltages or both be negative voltages. For example, polarity may be reversed when one voltage increases while another voltage decreases. In another implementation, only V com  electrode  565  may change in voltage. 
       FIG. 10  is an example of another circuit schematic of a three terminal IMOD. In  FIG. 10 , capacitor C 1   580  is coupled between V bias  electrode  555  and V d  electrode  560  rather than V d  electrode  560  and V com  electrode  565  as in  FIG. 5 . In the configuration of  FIG. 10 , movable element  570  may be moved to a reset position towards V com  electrode  565  rather than V bias  electrode  555  as in  FIG. 5 . That is, in  FIG. 10 , the electric field between V bias  electrode  555  and V d  electrode  560  may remain relatively unchanged and in the same direction, but the electric field between V d  electrode  560  and V com  electrode  565  may increase and switch direction, and therefore, pull movable element  570  towards V com  electrode  565 . In some implementations, movable element  570  may rest against a dielectric. 
     Accordingly, in the circuit schematic of  FIG. 10 , the capacitance between V bias  electrode  555  and V d  electrode  560  is the equivalent capacitance of capacitor C 1   580  in parallel with a series equivalent capacitance of air gap  585  and dielectric  875 . The capacitance between V d  electrode  560  and V com  electrode  565  is the equivalent series capacitance of movable element  570  and air gap  590 . If the capacitance between V bias  electrode  555  and V d  electrode  560  is sufficiently larger than the capacitance between V d  electrode  560  and V com  electrode  565 , then the circuit of  FIG. 10  operates similar to the circuit of  FIG. 9 . However, movable element  570  may be pulled downward rather than upward because capacitor C 1   580  is coupled between V bias  electrode  555  and V d  electrode  560  rather than V d  electrode  560  and V com  electrode  565 . 
     As previously discussed with  FIG. 1 , movable element  570  may include many layers, one layer being or including an electrode. In the circuit schematic of  FIG. 5 , V d  electrode  560  corresponds with a layer associated with a top portion of movable element  570 . 
       FIG. 11  is an example of another circuit schematic of a three terminal IMOD. In  FIG. 11 , V d  electrode  560  corresponds with a layer associated with a bottom portion of movable element  570  rather than a top portion as in  FIG. 5 . The top portion of movable element  570  may include a mirror. As such, the distance between V d  electrode  560  and V com  electrode  565  may be shorter than the distance between a mirror on another portion of movable element  570  and V com  electrode  565 . Additionally, the capacitance between V bias  electrode  555  and V d  electrode  560  is the equivalent capacitance of capacitor C 1   580  in parallel with a series equivalent capacitance of air gap  585 , dielectric  575 , and movable element  570 . The capacitance between V d  electrode  560  and V com  electrode  565  is the capacitance of air gap  590 . 
     In some implementations, as movable element  570  moves to a new position, certain instabilities may occur. For example, after movable element  570  has moved a certain distance, tip-in instability may occur due to rotational and translational properties of movable element  570 , its hinge design and its movement mechanism. Movable element  570  may tilt, and therefore, movable element  570  may reflect light at different wavelengths rather than the desired wavelength that would be provided if movable element  570  was flat. When movable element  570  undergoes tip-in, a high voltage bias may need to be applied to “flatten” all of movable element  570 . In some implementations, when tip-in instability occurs, approximately 50 V may need to be applied to movable element  570  such that it is re-oriented to be flat. 
     For example, movable element  570  may move towards V com  electrode  565 . However, as movable element  570  travels towards V com  electrode  565 , a tilt may occur, and therefore, a corner of movable element  570  may touch a dielectric layered above V com  electrode  565 . However, a second corner of movable element  570  may not be touching the dielectric because movable element  570  is tilted. That is, an air gap may exist between the second corner and the dielectric. Accordingly, the second corner may be pulled towards the dielectric and close the air gap by biasing V d  electrode  560  with a high voltage. As such, both corners of movable element  570  may make contact with the surface of the dielectric. 
     Another example of instability is pull-in instability. In some implementations, as movable element  570  moves a certain distance, pull-in instability may occur. Once movable element  570  moves a certain distance, the mechanical restoring force of the mechanism to move movable element  570  (e.g., a hinge mechanism) may be weaker than the electrostatic force provided by the biasing of the various electrodes. Accordingly, movable element  570  “snaps” in to a slightly different position. However, unlike tip-in instability, movable element  570  may stay relatively flat when pull-in occurs. 
     In some implementations, the occurrence of pull-in instability and tip-in instability may be mutually exclusive. That is, if tip-in instability occurs, then pull-in instability may not occur, and vice versa. In some implementations, pull-in instability may occur before tip-in instability may occur, or vice versa. Accordingly, in some implementations, a design allowing pull-in instability rather than tip-in instability may be useful in applications where movable element  570  may need to be flat as it is moved to a new position. 
     In the circuit of  FIG. 11 , pull-in instability rather than tip-in instability may occur because V d  electrode  560  corresponds to a layer associated with a bottom portion, or the portion closer to V com  electrode  560 , of movable element  570 . Accordingly, as previously discussed, the capacitance between V d  electrode  560  and V com  electrode  565  is lower because it only includes air gap  590  rather than both air gap  590  and movable element  570 . As such, less voltage may be needed to pull movable element  570  towards V com  electrode  565  and pull-in instability may occur before tip-in instability occurs. 
     Additionally, in some implementations, the size of air gap  585  may be reduced by driving movable element  870  from a bottom portion rather than a top portion. Additionally, dielectric layers associated with V bias  electrode  855  may also be thinner, allowing for easier and cheaper fabrication. 
       FIG. 12  is a flow diagram illustrating a method for moving a movable element to a reset position. In method  1200 , at block  1210 , the polarity of an electrode may be switched. For example, as previously discussed, the voltage on the electrode may change. In some implementations, the voltage on the electrode may be of an opposite polarity than that of another electrode. At block  1220 , a movable element may be moved to a reset position. As previously discussed, the movable element may move towards the electrode. In some implementations, the movable element may rest against a dielectric when in the reset position. The method ends at block  1230 . 
       FIGS. 13A and 13B  are system block diagrams illustrating a display device  40  that includes a plurality of IMOD display elements. The display device  40  can be, for example, a smart phone, a cellular or mobile telephone. However, the same components of the display device  40  or slight variations thereof are also illustrative of various types of display devices such as televisions, computers, tablets, e-readers, hand-held devices and portable media devices. 
     The display device  40  includes a housing  41 , a display  30 , an antenna  43 , a speaker  45 , an input device  48  and a microphone  46 . The housing  41  can be formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing  41  may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber and ceramic, or a combination thereof. The housing  41  can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols. 
     The display  30  may be any of a variety of displays, including a bi-stable or analog display, as described herein. The display  30  also can be configured to include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display  30  can include an IMOD-based display, as described herein. 
     The components of the display device  40  are schematically illustrated in  FIG. 13A . The display device  40  includes a housing  41  and can include additional components at least partially enclosed therein. For example, the display device  40  includes a network interface  27  that includes an antenna  43  which can be coupled to a transceiver  47 . The network interface  27  may be a source for image data that could be displayed on the display device  40 . Accordingly, the network interface  27  is one example of an image source module, but the processor  21  and the input device  48  also may serve as an image source module. The transceiver  47  is connected to a processor  21 , which is connected to conditioning hardware  52 . The conditioning hardware  52  may be configured to condition a signal (such as filter or otherwise manipulate a signal). The conditioning hardware  52  can be connected to a speaker  45  and a microphone  46 . The processor  21  also can be connected to an input device  48  and a driver controller  29 . The driver controller  29  can be coupled to a frame buffer  28 , and to an array driver  22 , which in turn can be coupled to a display array  30 . One or more elements in the display device  40 , including elements not specifically depicted in  FIG. 13A , can be configured to function as a memory device and be configured to communicate with the processor  21 . In some implementations, a power supply  50  can provide power to substantially all components in the particular display device  40  design. 
     The network interface  27  includes the antenna  43  and the transceiver  47  so that the display device  40  can communicate with one or more devices over a network. The network interface  27  also may have some processing capabilities to relieve, for example, data processing requirements of the processor  21 . The antenna  43  can transmit and receive signals. In some implementations, the antenna  43  transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, and further implementations thereof. In some other implementations, the antenna  43  transmits and receives RF signals according to the Bluetooth® standard. In the case of a cellular telephone, the antenna  43  can be designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G, 4G or 5G technology. The transceiver  47  can pre-process the signals received from the antenna  43  so that they may be received by and further manipulated by the processor  21 . The transceiver  47  also can process signals received from the processor  21  so that they may be transmitted from the display device  40  via the antenna  43 . 
     In some implementations, the transceiver  47  can be replaced by a receiver. In addition, in some implementations, the network interface  27  can be replaced by an image source, which can store or generate image data to be sent to the processor  21 . The processor  21  can control the overall operation of the display device  40 . The processor  21  receives data, such as compressed image data from the network interface  27  or an image source, and processes the data into raw image data or into a format that can be readily processed into raw image data. The processor  21  can send the processed data to the driver controller  29  or to the frame buffer  28  for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation and gray-scale level. 
     The processor  21  can include a microcontroller, CPU, or logic unit to control operation of the display device  40 . The conditioning hardware  52  may include amplifiers and filters for transmitting signals to the speaker  45 , and for receiving signals from the microphone  46 . The conditioning hardware  52  may be discrete components within the display device  40 , or may be incorporated within the processor  21  or other components. 
     The driver controller  29  can take the raw image data generated by the processor  21  either directly from the processor  21  or from the frame buffer  28  and can re-format the raw image data appropriately for high speed transmission to the array driver  22 . In some implementations, the driver controller  29  can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array  30 . Then the driver controller  29  sends the formatted information to the array driver  22 . Although a driver controller  29 , such as an LCD controller, is often associated with the system processor  21  as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor  21  as hardware, embedded in the processor  21  as software, or fully integrated in hardware with the array driver  22 . 
     The array driver  22  can receive the formatted information from the driver controller  29  and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display&#39;s x-y matrix of display elements. 
     In some implementations, the driver controller  29 , the array driver  22 , and the display array  30  are appropriate for any of the types of displays described herein. For example, the driver controller  29  can be a conventional display controller or a bi-stable display controller (such as an IMOD display element controller). Additionally, the array driver  22  can be a conventional driver or a bi-stable display driver (such as an IMOD display element driver). Moreover, the display array  30  can be a conventional display array or a bi-stable display array (such as a display including an array of IMOD display elements). In some implementations, the driver controller  29  can be integrated with the array driver  22 . Such an implementation can be useful in highly integrated systems, for example, mobile phones, portable-electronic devices, watches or small-area displays. 
     In some implementations, the input device  48  can be configured to allow, for example, a user to control the operation of the display device  40 . The input device  48  can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, a touch-sensitive screen integrated with the display array  30 , or a pressure- or heat-sensitive membrane. The microphone  46  can be configured as an input device for the display device  40 . In some implementations, voice commands through the microphone  46  can be used for controlling operations of the display device  40 . 
     The power supply  50  can include a variety of energy storage devices. For example, the power supply  50  can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. In implementations using a rechargeable battery, the rechargeable battery may be chargeable using power coming from, for example, a wall socket or a photovoltaic device or array. Alternatively, the rechargeable battery can be wirelessly chargeable. The power supply  50  also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply  50  also can be configured to receive power from a wall outlet. 
     In some implementations, control programmability resides in the driver controller  29  which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver  22 . The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations. 
     As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c. 
     The various illustrative logics, logical blocks, modules, circuits and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and steps described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular steps and methods may be performed by circuitry that is specific to a given function. 
     In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus. 
     Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of, e.g., an IMOD display element as implemented. 
     Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, a person having ordinary skill in the art will readily recognize that such operations need not be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. 
     Though the circuits and techniques disclosed herein utilize an NMOS transistor, any other type of element with the functionality of a switch may be used. For example, PMOS transistors, bipolar junction transistors, memristors, and other components may be used. Depletion-type and enhancement-type PMOS and NMOS transistors may also be used. 
     Additionally, the circuits and techniques disclosed herein may be used in applications beyond positioning a movable element. The circuits and techniques may be employed in any scenario where positioning an object to a reset position may be beneficial. 
     The circuits and techniques disclosed herein utilize examples of values (e.g., voltages, capacitances, dimensions, etc.) that are provided for illustration purposes only. Other implementations may involve different values.