HK1102840A - Systems and methods of actuating mems display elements - Google Patents

Abstract

CN101010714A Methods of writing display data to MEMS display elements are configured to minimize charge buildup and differential aging. The methods may include writing data with opposite polarities, and periodically releasing and/or actuating MEMS elements during the display updating process. Actuating MEMS elements with potential differences higher than those used during normal display data writing may also be utilized.

Description

System and method for activating MEMS display elements

Technical Field

Is free of

Background

Microelectromechanical Systems (MEMS) include micromechanical elements, actuators, and electronics. Micromechanical elements may be created using deposition, etching, 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 MEMS device is referred to as an interferometric modulator. An interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. One plate may comprise a stationary layer deposited on a substrate and the other plate may comprise a metallic membrane separated from the stationary layer by an air gap. These devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of these types of devices so that their features can be exploited in improving existing products and creating new products that have not yet been developed.

Disclosure of Invention

The system, method, and apparatus of the present invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled "detailed description of certain embodiments" one will understand how the features of this invention provide advantages over other display devices.

In one embodiment, the invention provides an apparatus comprising a controller configured to control a driver circuit that actuates a MEMS display element with a potential difference of a first polarity during a first portion of a display write process. The controller is configured to cause the driver circuit to release the MEMS display element after the actuation and then actuate the MEMS element with a potential difference of a polarity opposite the first polarity during a second portion of the display write process. The apparatus further comprises at least one output port configured to communicate, at least in part, a potential difference to the MEMS display element during a first portion of a display write process.

In another embodiment, the invention provides an apparatus configured to drive a set of MEMS display elements. The apparatus comprises means for controlling actuation of the MEMS display element with a potential difference of a first polarity during a first portion of a display write process. The apparatus further includes means for causing release of the MEMS display element, and means for controlling actuation of the MEMS display element with a potential difference having a polarity opposite the first polarity during a second portion of the display writing process. The apparatus further comprises means for communicating, at least in part, the potential difference to the MEMS display element during a first portion of a display write process.

In yet another embodiment, the invention provides a method of actuating a set of MEMS display elements comprising a portion of an array of MEMS display elements. The method comprises the following steps: actuating the MEMS display elements with a potential difference of a first polarity during a first portion of a display write process; releasing the MEMS display element; and then actuating the MEMS display elements with a potential difference having a polarity opposite the first polarity during a second portion of the display write process.

In yet another embodiment, the present invention provides an apparatus configured to operate MEMS display elements in an array of MEMS display elements. The apparatus includes a controller configured to control a driver circuit that periodically applies first and second potential differences to the MEMS element. These first and second potential differences are of opposite polarity and of approximately equal magnitude sufficient to actuate the MEMS element. The controller is configured to periodically apply these first and second potential differences to the MEMS element in an alternating manner. The first and second potential differences are applied to the MEMS elements at defined times and for defined durations that depend on the rate at which image data is written to the MEMS array. The first and second potential differences are each applied to the MEMS elements for approximately equal amounts of time in a given period of display use. The controller is further configured to write the same frame of data using two potential differences. The apparatus also includes at least one output port configured to communicate, at least in part, a potential difference to the MEMS display element during a first portion of a display write process.

In yet another embodiment, the present disclosure provides an apparatus configured to update a display. The apparatus comprises means for modulating light and means for applying a potential difference to the light modulating means. The means for applying a potential difference to the light modulating means is configured to periodically apply a first potential difference and a second potential difference to the modulating means. The first and second potential differences are of opposite polarity and of approximately equal magnitude sufficient to actuate the light modulating means. The first potential difference and the second potential difference are applied to the light modulating means at defined times and for defined durations, respectively, which depend on the rate at which image data is written to the modulating means. The first and second potential differences are each applied to the light modulating means for approximately equal amounts of time in a given period of display use. The applying means is further configured to write the same frame of data using both the first and second potential differences.

In yet another embodiment, the invention provides a method of operating a MEMS element in an array of MEMS elements forming a display. The method includes periodically applying a first potential difference to the MEMS element, wherein the first potential difference has a polarity and a magnitude sufficient to actuate the MEMS element. The method further includes periodically applying a second potential difference to the MEMS element, the second potential difference having an opposite polarity and approximately equal magnitude to the first potential difference. These first and second potential differences are applied to the MEMS elements at defined times and for defined durations, respectively, that depend on the rate at which image data is written to the array of MEMS elements. The first and second potential differences are each applied to the MEMS elements for approximately equal amounts of time in a given period of display use. The method further comprises writing the same frame of data using both the potential difference of the first polarity and the potential difference of a polarity opposite to the first polarity.

In yet another embodiment, the disclosure provides an apparatus configured to display an image. The apparatus comprises: a plurality of MEMS elements in the display; and a controller configured to activate all of the MEMS elements in a portion of the display and write display data to the portion.

In yet another embodiment, the present invention provides an apparatus for displaying an image. The apparatus includes a plurality of means for modulating light, and means for controlling activation and writing of all of the plurality of means for modulating light in a portion of the display.

In yet another embodiment, the invention provides a method of writing display data to an array of MEMS display elements. The method includes activating all MEMS elements in a portion of an array and writing display data to the portion of the array.

In yet another embodiment, the invention provides a system configured to write data to an array of MEMS display elements. The system includes a column driver and a row driver. The row driver and column driver are configured to actuate at least some elements of the array with first and second potential differences, wherein an absolute value of the second potential difference is greater than an absolute value of the first potential difference.

In yet another embodiment, the invention provides a system configured to write data to an array of MEMS display elements. The system includes means for driving columns of the MEMS display elements and means for driving rows of the MEMS display elements. The row and column drive means are configured to actuate at least some elements of the array with first and second potential differences, wherein the absolute value of the second potential difference is greater than the absolute value of the first potential difference.

In yet another embodiment, the invention provides a method of writing display data to an array of MEMS display elements comprising actuating at least some elements of the array with first and second potential differences, wherein the absolute value of the second potential difference is greater than the absolute value of the first potential difference.

Drawings

FIG. 1 is an isometric view depicting a portion of one embodiment of an interferometric modulator display in which a movable reflective layer of a first interferometric modulator is in a released position and a movable reflective layer of a second interferometric modulator is in an actuated position.

FIG. 2 is a system block diagram illustrating one embodiment of an electronic device incorporating a 33 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltage for one exemplary embodiment of an interferometric modulator of FIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that may be used to drive an interferometric modulator display.

FIG. 5A illustrates one exemplary frame of display data in the 33 interferometric modulator display of FIG. 2.

FIG. 5B illustrates one exemplary timing diagram for row and column signals that may be used to write the frame of FIG. 5A.

Fig. 6A is a cross-section of the device of fig. 1.

FIG. 6B is a cross section of an alternative embodiment of an interferometric modulator.

FIG. 6C is a cross section of another alternative embodiment of an interferometric modulator.

FIG. 7 is an exemplary timing diagram for row and column signals that may be used in one embodiment of the invention.

FIGS. 8A and 8B illustrate a set of row and column voltages that may be used to drive an interferometric modulator display in one embodiment of the invention.

FIGS. 9A and 9B are system block diagrams illustrating an embodiment of a visual display device comprising a plurality of interferometric modulators.

Detailed Description

The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in many different forms. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. As will be appreciated from the following description, the invention may be implemented in any device that is configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual or pictorial. More particularly, it is contemplated that the invention may be implemented in or associated with a variety of electronic devices such as, but not limited to, mobile telephones, wireless devices, Personal Data Assistants (PDAs), hand-held or portable computers, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, computer monitors, auto displays (e.g., odometer display, etc.), cockpit controls and/or displays, displays of camera views (e.g., of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., a display of images for a piece of jewelry). MEMS devices of similar structure to those described herein can also be used in non-display applications such as in electronic switching devices.

One interferometric modulator display embodiment comprising an interferometric MEMS display element is illustrated in FIG. 1. In these devices, the pixels are in either a bright or dark state. In the bright ("on" or "open") state, the display element reflects a large portion of incident visible light to a user. When in the dark ("off" or "closed") state, the display element reflects little incident visible light to the user. Depending on the embodiment, the light reflectance properties of the "on" and "off" states may be reversed. MEMS pixels can be configured to reflect predominantly at selected colors, allowing for a color display in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series of pixels of a visual display, wherein each pixel comprises a MEMS interferometric modulator. In some embodiments, an interferometric modulator display comprises a row/column array of these interferometric modulators. Each interferometric modulator includes a pair of reflective layers positioned at a variable and controllable distance from each other to form a resonant optical cavity with at least one variable dimension. In one embodiment, one of the reflective layers may be moved between two positions. In the first position, referred to herein as the released position, the movable layer is positioned a relatively large distance from the fixed partially reflective layer. In the second position, the movable layer is positioned more closely adjacent to the partially reflective layer. Incident light that reflects from the two layers interferes constructively or destructively depending on the position of the movable reflective layer, producing either a fully reflective or non-reflective state for each pixel.

The depicted portion of the pixel array in FIG. 1 includes two adjacent interferometric modulators 12a and 12 b. In the interferometric modulator 12a on the left, a movable and highly reflective layer 14a is illustrated in a released position at a predetermined distance from a fixed partially reflective layer 16 a. In the interferometric modulator 12b on the right, the movable highly reflective layer 14b is illustrated in an actuated position adjacent to a fixed partially reflective layer 16 b.

The fixed layers 16a, 16b are electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more layers, each of chromium and indium tin oxide, onto a transparent substrate 20. The layers are patterned into parallel strips, and may form row electrodes in a display device, as described further below. The movable layers 14a, 14b may be formed as a series of parallel strips (perpendicular to the row electrodes 16a, 16 b) of a deposited metal layer(s) deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. When the sacrificial material is etched away, the deformable metal layer is separated from the fixed metal layer by a defined air gap 19. A highly conductive and reflective material such as aluminum may be used for the deformable layers, and these strips may form column electrodes in a display device.

With no applied voltage, the cavity 19 remains between the layers 14a, 16a, and the deformable layer is in a mechanically relaxed state, as illustrated by the pixel 12a in FIG. 1. However, when a potential difference is applied to a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the voltage is high enough, the movable layer deforms and is forced against the fixed layer (a dielectric material not shown in this figure may be deposited on the fixed layer to prevent shorting and control the separation distance), as illustrated by the pixel 12b on the right in FIG. 1. Behaves the same regardless of the polarity of the applied potential difference. In this manner, row/column actuation that can control the reflective vs. non-reflective pixel states is analogous in many ways to that used in conventional LCD and other display technologies.

FIGS. 2-5 illustrate one exemplary process and system for using an array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of an electronic device that may incorporate aspects of the invention. In the exemplary embodiment, the electronic device packageIncludes a processor 21 which may be any general purpose single-or multi-chip microprocessor (e.g., ARM, Pentium)^®、Pentium II^®、Pentium III^®、Pentium IV^®、Pentium^®Pro、8051、MIPS^®、Power PC^®、ALPHA^®) Or any special purpose microprocessor (e.g., digital signal processor, microcontroller), or programmable gate array. As is conventional in the art, the processor 21 may be configured to execute one or more software modules. In addition to executing an operating system, the processor 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.

In one embodiment, the processor 21 is also configured to communicate with an array controller 22. In one embodiment, the array controller 22 includes a row driver circuit 24 and a column driver circuit 26 that provide signals to a pixel array 30. The cross-section of the array illustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. For MEMS interferometric modulators, the row/column actuation protocol may take advantage of the hysteresis properties of these devices illustrated in FIG. 3. A potential difference of, for example, 10 volts may be required to cause a movable layer to deform from the released state to the actuated state. However, when the voltage is reduced from that value, the movable layer maintains its state as the voltage drops back below 10 volts. In the exemplary embodiment of FIG. 3, the movable layer does not release completely until the voltage drops below 2 volts. There is thus a range of voltage, about 3 to 7V in the example illustrated in figure 3, where there exists a window of applied voltage within which the device is stable in either the released or actuated state. This window is referred to herein as the "hysteresis window" or "stability window". For a display array having the hysteresis characteristics of FIG. 3, the row/column actuation protocol may be designed such that during row strobing, pixels in the strobed row that are to be actuated are exposed to a voltage difference of about 10 volts, and pixels that are to be released are exposed to a voltage difference of close to zero volts. After the strobe, the pixels are exposed to a steady state voltage difference of about 5 volts such that they remain in whatever state the row strobe put them in. In this example, each pixel sees a potential difference within the "stability window" of 3-7 volts after being written. This feature makes the pixel design illustrated in fig. 1 stable under the same applied voltage conditions in either an actuated or released pre-existing state. Because each pixel of the interferometric modulator, whether in the actuated or released state, is essentially a capacitor formed by the fixed and moving reflective layers, this stable state can be maintained at a voltage within the hysteresis window with almost no power dissipation. Essentially, if the applied voltage is fixed, no current flows into the pixel.

In typical applications, a display frame may be created by asserting the set of column electrodes in accordance with the desired set of actuated pixels in the first row. A row pulse is then applied to the row 1 electrode, actuating the pixels corresponding to the asserted column lines. The set of asserted column electrodes is then changed to correspond to the desired set of actuated pixels in the second row. A pulse is then applied to the row 2 electrode, actuating the appropriate pixels in row 2 in accordance with the asserted column electrodes. The row 1 pixels are unaffected by the row 2 pulse, and remain in the state they were set to during the row 1 pulse. This process may be repeated for the entire series of rows in a sequential manner to produce a frame. Typically, the frames are refreshed and/or updated with new display data by continually repeating this process at some desired number of frames per second. A wide variety of protocols for driving row and column electrodes of pixel arrays to produce display frames are also well known and may be used in conjunction with the present invention.

Fig. 4 and 5 illustrate one possible activation protocol for forming display frames on the 3 x 3 array of fig. 2. FIG. 4 illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves of FIG. 3. In the FIG. 4 embodiment, actuating a pixel involves setting the appropriate column to-V_biasAnd the appropriate row is set to + deltav, which may correspond to-5 volts and +5 volts, respectively. Releasing the pixel is by setting the appropriate column to + V_biasAnd the appropriate row is set to the same + av, producing a zero volt potential difference across the pixel. Those rows where the row voltage is maintained at zero voltsIn, no matter the column is at + V_biasOr is-V_biasThe pixel is stable in whatever state it was originally in.

FIG. 5B is a timing diagram showing a series of row and column signals applied to the 3 x 3 array of FIG. 2 which will result in the display arrangement illustrated in FIG. 5A, wherein actuated pixels are non-reflective. Prior to writing the frame illustrated in FIG. 5A, the pixels can be in any state, and in this example all the rows are at 0 volts, and all the columns are at +5 volts. With these applied voltages, all pixels are stable in their existing actuated or released states.

In the frame of fig. 5A, pixels (1, 1), (1, 2), (2, 2), (3, 2), and (3, 3) are activated. To accomplish this, during a "line time" for row 1, columns 1 and 2 are set to-5 volts, and column 3 is set to +5 volts. This does not change the state of any pixels, since all pixels remain in the 3-7 volt stability window. Row 1 is then strobed with a pulse that goes from 0, up to 5 volts, and back to zero. This activates the (1, 1) and (1, 2) pixels and releases the (1, 3) pixel. No other pixels in the array are affected. To set row 2 as desired, column 2 is set to-5 volts, and columns 1 and 3 are set to +5 volts. The same strobe applied to row 2 will then activate pixel (2, 2) and release pixels (2, 1) and (2, 3). Again, no other pixels of the array are affected. Row 3 is similarly set by setting columns 2 and 3 to-5 volts, and column 1 to +5 volts. The row 3 strobe sets the row 3 pixels as shown in FIG. 5A. After writing the frame, the row potentials are zero, and the column potentials can remain at either +5 or-5 volts, and the display is then stable in the arrangement of FIG. 5A. It will be appreciated that the same procedure can be used for arrays of tens or hundreds of rows and columns. It will also be appreciated that the timing, sequence, and levels of voltages used to perform row and column actuation can be varied widely within the general principles outlined above, and the above example is exemplary only, and any actuation voltage method can be used with the present invention. For example, it will be appreciated that the voltage drive may be offset from a circuit common voltage of the array drive circuitMoving the array elements so that the rows may change from 6.2V to 6.2V + V_biasAnd similarly the column will switch from a low voltage (e.g. 1V) to 1V + 2V_bias. In this embodiment, the release voltage may be slightly different than zero volts. It can be as large as two volts, but is typically less than one volt.

The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example, FIGS. 6A-6C illustrate three different embodiments of moving mirror structures. Fig. 6A is a cross-section of the embodiment of fig. 1, wherein a strip of metal material 14 is deposited on vertically extending supports 18. In FIG. 6B, the moveable reflective material 14 is attached to supports at the corners only, on tethers (teters) 32. In FIG. 6C, the moveable reflective material 14 is suspended from the deformable layer 34. This embodiment has benefits because the structural design and materials used for the reflective material 14 can be optimized with respect to the optical properties, and the structural design and materials used for the deformable layer 34 can be optimized with respect to desired mechanical properties. The production of various types of interferometric devices is described in various publications, including, for example, U.S. published application No. 2004/0051929. A variety of well-known techniques may be used to create the above-described structures, involving a series of material deposition, patterning, and etching steps.

One aspect of the above-described devices is that charge can accumulate on the dielectric between the layers of the device, especially when the device is activated and held in an activated state by an electric field that is always in the same direction. For example, if the moving layer is always at a higher potential relative to the fixed layer when the device is actuated by a potential having a magnitude greater than the external stability threshold, slowly increasing charge accumulation on the dielectric between the layers may begin to shift the hysteresis curve of the device. This is undesirable because it causes the display performance to vary over time and in different ways for different pixels to be activated in different ways over time. As can be seen in the example of FIG. 5B, a given pixel experiences a 10 volt difference during actuation, and at each time in this example, the row electrodes are at a 10V higher potential than the column electrodes. During activation, the electric field between the plates thus always points in one direction, i.e. from the row electrode towards the column electrode.

This problem can be alleviated by actuating the MEMS display elements with a potential difference of a first polarity during a first portion of the display write process and actuating the MEMS display elements with a potential difference having an opposite polarity to the first polarity during a second portion of the display write process. This basic principle is illustrated in fig. 7, 8A and 8B.

In fig. 7, two frames of display data, frame N and frame N +1, are written in order. In this figure, the data for the columns is valid for row 1 during a row 1 line time (i.e., +5 or-5 depending on the desired state of the pixels in row 1), for row 2 during a row 2 line time, and for row 3 during a row 3 line time. Frame N (referred to herein as positive polarity) is written as shown in FIG. 5B, where the row electrode is 10V higher than the column electrode during MEMS device actuation. In this example, during actuation, the column electrodes can be-5V, and the scan voltage on the rows is + 5V. The activation and deactivation of frame N is therefore performed according to the same table in fig. 8A as in fig. 4.

Frame N +1 is written according to the table in fig. 8B. For frame N +1, the scan voltage is-5V, and the column voltage is set to +5V for actuation and to-5V for release. Thus, in frame N +1, the column voltage is 10V higher (referred to herein as negative polarity) than the row voltage. Because the display is continuously refreshed and/or updated, the polarity may alternate between frames, with frame N +2 being written in the same manner as frame N, frame N +3 being written in the same manner as frame N +1, and so on. In this way, the activation of the pixels occurs in both polarities. In an embodiment following this principle, potentials of opposite polarity are applied to a given MEMS element at defined times and for defined durations, respectively, that depend on the rate at which image data is written to the MEMS elements of the array, and the opposite potential differences are each applied for approximately the same amount of time in a given period of display use. This helps reduce charge buildup on the dielectric over time.

Various modifications to this scheme may be implemented. For example, frame N and frame N +1 may include different display data. Alternatively, it may be the same display data that is written twice to the array with opposite polarity. It may also be advantageous to dedicate certain frames to setting the state of all or substantially all pixels to a released state and/or setting the state of all or substantially all pixels to an activated state prior to writing desired display data. Setting all pixels to a common state may be performed in a single row line time by, for example, setting all columns to +5V (or-5V) and scanning all rows with a-5V scan (or +5V scan) simultaneously.

In one such embodiment, the desired display data is written to the array with one polarity, all pixels are released, and the same display data is written a second time with the opposite polarity. This is similar to the scheme illustrated in FIG. 7, where frame N is the same as frame N +1, and where the array release line time is inserted between the frames. In another embodiment, each display update of new display data is preceded by a release row line time.

In another embodiment, the row line time is used to activate all pixels of the array, the second line time is used to release all pixels of the array, and then the display data (e.g., frame N) is written to the display. In this embodiment, frame N +1 may be preceded by an array active line time and an array release line time of opposite polarity for the frame preceding frame N, and frame N +1 may then be written. In some embodiments, an activation line time of one polarity, a release line time of the same polarity, an activation line time of opposite polarity, and a release line time of opposite polarity may precede each frame. These embodiments ensure that all or substantially all pixels are activated at least once for each frame of display data, thereby reducing differential aging (differential aging) effects and reducing charge accumulation.

In some cases, it may be advantageous to use an ultra-high activation voltage during the array activation line time. For example, during the array active line time described above, the row scan voltage may be 7V or 10V instead of 5V. In this embodiment, the highest voltage applied to the pixels occurs during these "over active" array activation times, and not during display data updates. This may also help reduce differential aging effects for different pixels, some of which may change frequently during display updates while others may change infrequently during display updates, depending on the image being displayed.

It is also possible to perform these polarity inversions and activation/deactivation protocols in a row-by-row manner. In these embodiments, each row of a frame may be written more than once during the frame writing process. For example, when writing row 1 of frame N, the pixels of row 1 may all be released, and the display data for row 1 may be written with positive polarity. The row 1 pixels may be released a second time and the row 1 display data written again with negative polarity. Actuating all of the pixels of row 1 as described above may also be performed for the entire array. It will be further appreciated that the release, activation, and over-activation may be performed with a lower frequency than every row write or every frame write during the display update/refresh process.

Fig. 9A and 9B are system block diagrams illustrating an embodiment of a display device 2040. The display device 2040 can be, for example, a cellular or mobile telephone. However, the same components of display device 2040 or slight variations thereof are also illustrative of various types of display devices such as televisions and portable media players.

The display device 2040 includes a housing 2041, a display 2030, an antenna 2043, a speaker 2045, an input device 2048, and a microphone 2046. The housing 2041 is generally formed by any of a variety of manufacturing processes well known to those skilled in the art, including injection molding and vacuum forming. Additionally, the housing 2041 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. In one embodiment, the housing 2041 includes removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

As described herein, the display 2030 of exemplary display device 2040 may be any of a variety of displays including a bi-stable display. In other embodiments, the display 2030 includes a flat panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described above, or a non-flat panel display, such as a CRT or other tube device, as is well known to those of skill in the art. However, for purposes of describing the present embodiment, the display 2030 includes an interferometric modulator display, as described herein.

The components of one embodiment of exemplary display device 2040 are schematically illustrated in FIG. 9B. The illustrated exemplary display device 2040 includes a housing 2041 and can include additional components at least partially enclosed in the housing 2041. For example, in one embodiment, the exemplary display device 2040 includes a network interface 2027, which network interface 2027 includes an antenna 2043 coupled to the transceiver 2047. The transceiver 2047 is connected to the processor 2021, and the processor 2021 is connected to conditioning hardware 2052. Conditioning hardware 2052 may be configured to condition (e.g., filter) a signal. Conditioning hardware 2052 is connected to a speaker 2045 and a microphone 2046. The processor 2021 is also connected to an input device 2048 and a driver controller 2029. The driver controller 2029 is coupled to a frame buffer 2028 and to an array driver 2022, which array driver 2022 is in turn coupled to a display array 2030. A power supply 2050 provides power to all components as required by the particular exemplary display device 2040 design.

The network interface 2027 includes the antenna 2043 and the transceiver 2047 so that the exemplary display device 2040 can communicate with one or more devices over a network. In one embodiment, the network interface 2027 may also have some processing capabilities to relieve requirements of the processor 2021. The antenna 2043 is any antenna known to those skilled in the art for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE802.11 standard, including IEEE802.11(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS or other known signals that are used to communicate within a wireless cell phone network. The transceiver 2047 pre-processes the signals received from the antenna 2043 so that they may be received by and further processed by the processor 2021. The transceiver 2047 also processes signals received from the processor 2021 so that they may be transmitted from the exemplary display device 2040 via the antenna 2043.

In an alternative embodiment, the transceiver 2047 may be replaced by a receiver. In yet another alternative embodiment, the network interface 2027 may be replaced by an image source, which may store or generate image data to be sent to the processor 2021. For example, the image source can be a Digital Video Disc (DVD) or a hard-disc drive that contains image data, or a software module that generates image data.

The processor 2021 generally controls the overall operation of the exemplary display device 2040. The processor 2021 receives data, such as compressed image data from the network interface 2027 or an image source, and processes the data into raw image data or into a format that is readily processed into raw image data. The processor 2021 then sends the processed data to the driver controller 2029 or to frame buffer 2028 for storage. Raw data generally refers to information that identifies the image characteristics at each location within an image. These image characteristics may include color, saturation, and gray-scale level, for example.

In one embodiment, the processor 2021 includes a microcontroller, CPU, or logic unit to control the operation of the exemplary display device 2040. Conditioning hardware 2052 typically includes amplifiers and filters for transmitting signals to the speaker 2045, and for receiving signals from the microphone 2046. Conditioning hardware 2052 may be discrete components within the exemplary display device 2040, or may be incorporated within the processor 2021 or other components.

The driver controller 2029 takes the raw image data generated by the processor 2021 either directly from the processor 2021 or from the frame buffer 2028 and reformats the raw image data appropriately for high speed transmission to the array driver 2022. In particular, the driver controller 2029 reformats 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 2030. The driver controller 2029 then sends the formatted information to the array driver 2022. Although a driver controller 2029, such as an LCD controller, is typically associated with the system processor 2021 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. They may be embedded in the processor 2021 as hardware, embedded in the processor 2021 as software, or fully integrated in hardware with the array driver 2022.

Typically, the array driver 2022 receives the formatted information from the driver controller 2029 and reformats the video data into a parallel set of waveforms that are applied many times per second to the hundreds and sometimes thousands of leads coming from the display's x-y matrix of pixels.

In one embodiment, the driver controller 2029, array driver 2022, and display array 2030 are appropriate for any of the types of displays described herein. For example, in one embodiment, the driver controller 2029 is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, the array driver 2022 is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, the driver controller 2029 is integrated with the array driver 2022. This embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment, display array 2030 is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).

The input device 2048 allows a user to control the operation of the exemplary display device 2040. In one embodiment, input device 2048 includes a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a touch-sensitive screen, a pressure-or heat-sensitive membrane. In one embodiment, the microphone 2046 is an input device for the exemplary display device 2040. When the microphone 2046 is used to input data to the device, voice commands may be provided by a user for controlling the operation of the exemplary display device 2040.

The power supply 2050 may include a variety of energy storage devices as are well known in the art. For example, in one embodiment, power supply 2050 is a rechargeable battery such as a nickel cadmium battery or a lithium ion battery. In another embodiment, power supply 2050 is a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell, and solar-cell paint. In another embodiment, power supply 2050 is configured to receive power from a wall outlet.

In some implementations, control programmability resides, as described above, in a driver controller, which can be located in several places in the electronic display system. In some cases control programmability resides in the array driver 2022. Those skilled in the art will appreciate that the above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.

While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the spirit of the invention. For example, it will be appreciated that the test voltage driver circuitry may be separate from the array driver circuitry used to manufacture the display. With respect to the current sensors, separate voltage sensors may be dedicated to separate row electrodes. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (98)

1. An apparatus configured to drive a MEMS display element, the apparatus comprising:

a controller configured to control a driver circuit, said driver circuit actuating a MEMS display element with a potential difference of a first polarity during a first portion of a display write process, said controller configured to cause said driver circuit to release said MEMS display element after said actuation and then actuate said MEMS display element with a potential difference of a polarity opposite said first polarity during a second portion of said display write process; and

at least one output port configured to communicate, at least in part, the potential difference to the MEMS display elements during the first portion of the display write process.

2. The apparatus of claim 1, wherein the at least one output port comprises at least one chip pin.

3. The apparatus of claim 1, wherein the at least one output port comprises at least one conductive line.

4. The apparatus of claim 1, wherein the at least one output port comprises at least one interface to the driver circuit.

5. The apparatus of claim 1, wherein the at least one output port comprises at least one row output port and at least one column output port.

6. The apparatus of claim 1, wherein the first portion of the display write process comprises writing a first frame of display data to the MEMS display elements, and wherein the second portion of the display write process comprises writing a second frame of display data to the MEMS display elements.

7. The apparatus of claim 6, wherein one or more other frames of display data are written to the MEMS display elements between the first frame and the second frame.

8. The apparatus of claim 1, wherein the controller is further configured to actuate the MEMS display element with a potential difference of the first polarity during a third portion of the display write process.

9. The apparatus of claim 1, wherein the controller is further configured to alternately apply potential differences of opposite polarity to the MEMS display elements during alternating portions of the display write process.

10. The apparatus of claim 9, wherein alternating portions of the display writing process comprise writing alternating frames of display data to the MEMS display elements.

11. The apparatus of claim 10, wherein the alternating portions of the display writing process comprise writing alternating rows of display data to an array of MEMS display elements.

12. The apparatus of claim 1, wherein the controller is configured to:

writing a first frame of display data to an array of MEMS display elements with a potential difference of the first polarity so as to actuate the MEMS display elements;

disposing substantially all MEMS elements in the array in a released state; and

a second frame of display data is written to the array with a potential difference of opposite polarity to the first polarity in order to actuate the MEMS display elements.

13. The apparatus of claim 12, wherein the first frame of display data and the second frame of display data are the same.

14. The apparatus of claim 1, further comprising:

a processor in electrical communication with the MEMS display element, the processor configured to process image data; and

a memory device in electrical communication with the processor.

15. The apparatus of claim 14, wherein the processor is configured to send at least a portion of the image data to the controller.

16. The apparatus of claim 14, further comprising an image source module configured to send the image data to the processor.

17. The apparatus of claim 16, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

18. The apparatus of claim 14, further comprising an input device configured to receive input data and to communicate the input data to the processor.

19. The apparatus of claim 1, wherein the controller is configured to:

disposing substantially all MEMS elements in a row of an array of MEMS display elements in a released state;

writing a first set of display data to a row with a potential difference of the first polarity in order to actuate the MEMS display elements;

disposing substantially all MEMS elements in the row in a released state; and

a second set of display data is written to the row with a potential difference of opposite polarity to the first polarity in order to actuate the MEMS display elements.

20. The apparatus of claim 19, wherein the first set of display data and the second set of display data comprise the same data.

21. An apparatus configured to drive a set of MEMS display elements, the apparatus comprising:

means for controlling actuation of said MEMS display elements with a potential difference of a first polarity during a first portion of a display write process and for causing release of said MEMS display elements and then controlling actuation of said MEMS elements with a potential difference having a polarity opposite said first polarity during a second portion of said display write process; and

means for communicating, at least in part, the potential difference to the MEMS display elements during the first portion of the display write process.

22. The apparatus of claim 21, wherein the means for controlling activation of the MEMS display element comprises a controller.

23. The apparatus of claim 22, wherein the means for causing release of the MEMS display element comprises a controller.

24. The apparatus of claim 21, wherein the means for controlling activation of the MEMS display element comprises a processor.

25. The apparatus of claim 21, wherein the means for controlling actuation of the MEMS display elements with a potential difference of a first polarity comprises writing a first frame of display data to the set of MEMS display elements, and wherein the second portion of the display writing process comprises writing a second frame of display data to the set of MEMS display elements.

26. The apparatus of claim 25, wherein one or more other frames of display data are written to the set between the first frame and the second frame.

27. The apparatus of claim 21, wherein the apparatus is further configured to control actuation of the MEMS display element with a potential difference of the first polarity during a third portion of the display write process.

28. The apparatus of claim 21, wherein the apparatus is further configured to alternately apply potential differences of opposite polarity to the set of display elements during alternating portions of the display write process.

29. The apparatus of claim 28, wherein alternating portions of the display write process comprise writing alternating frames of display data to the set of MEMS display elements.

30. The apparatus of claim 29, wherein the alternating portion of the display writing process comprises writing alternating rows of display data to the set of MEMS display elements.

31. The apparatus of claim 21, wherein the apparatus is further configured to:

writing a first frame of display data to the set of MEMS display elements with a potential difference of the first polarity by controlling actuation of the MEMS display elements;

disposing substantially all MEMS elements in the set in a released state; and

a second frame of display data is written to the set with a potential difference of a polarity opposite the first polarity by controlling actuation of the MEMS display elements.

32. The apparatus of claim 31, wherein the first frame of display data and the second frame of display data are the same.

33. The apparatus of claim 21, wherein the apparatus is configured to:

disposing substantially all MEMS elements in a row of the set in a released state;

writing a first set of display data to the rows of the set with a potential difference of the first polarity by controlling actuation of the MEMS display elements;

disposing substantially all MEMS elements in the row of the set in a released state; and

writing a second set of display data to the rows of the set with a potential difference of a polarity opposite the first polarity by controlling actuation of the MEMS display elements.

34. The apparatus of claim 33, wherein the apparatus comprises a controller.

35. The apparatus of claim 33, wherein the first set of display data and the second set of display data comprise the same data.

36. The apparatus of claim 21, wherein the means for at least partially communicating the potential difference to the MEMS display element comprises at least one output port in communication with a controller.

37. The apparatus of claim 21, wherein the means for at least partially communicating the potential difference to the MEMS display element comprises at least one chip pin.

38. The apparatus of claim 21, wherein the means for at least partially communicating the potential difference to the MEMS display element comprises at least one conductive line.

39. The apparatus of claim 21, wherein the means for at least partially communicating the potential difference to the MEMS display element comprises at least one interface to a driver circuit that actuates a MEMS display element.

40. A method of actuating a set of MEMS display elements, the MEMS display elements comprising a portion of an array of MEMS display elements, the method comprising:

actuating the MEMS display elements with a potential difference of a first polarity during a first portion of a display write process;

releasing the MEMS display element; and

actuating the MEMS display elements with a potential difference having a polarity opposite the first polarity during a second portion of the display write process.

41. The method of claim 40, wherein the first portion of the display write process comprises writing a first frame of display data to the array of MEMS display elements, and wherein the second portion of the display write process comprises writing a second frame of display data to the array of MEMS display elements.

42. The method of claim 41, wherein one or more other frames of display data are written to the array between the first frame and the second frame.

43. The method of claim 40, further comprising actuating the MEMS display elements with a potential difference of the first polarity during a third portion of the display write process.

44. The method of claim 40, further comprising alternately applying potential differences of opposite polarity to display elements of the array during alternating portions of the display write process.

45. The method of claim 44, wherein the alternating portions of the display writing process comprise writing alternating frames of display data to the array of MEMS display elements.

46. The method of claim 45, wherein the alternating portions of the display writing process comprise writing alternating rows of display data to the array of MEMS display elements.

47. The method of claim 40, further comprising:

disposing substantially all MEMS elements in a row of the array in a released state;

writing a first set of display data to the rows of the array with a potential difference of the first polarity in order to actuate the MEMS display elements;

disposing substantially all MEMS elements in the row of the array in a released state; and

a second set of display data is written to the rows of the array with a potential difference of opposite polarity to the first polarity in order to actuate the MEMS display elements.

48. The method of claim 47, wherein the first set of display data and the second set of display data comprise the same data.

49. The method of claim 40, further comprising:

writing a first frame of display data to the array with a potential difference of the first polarity so as to actuate the MEMS display elements;

disposing substantially all MEMS elements in the array in a released state; and

a second frame of display data is written to the array with a potential difference of opposite polarity to the first polarity in order to actuate the MEMS display elements.

50. The method of claim 49, wherein the first frame of display data and the second frame of display data are the same.

51. An apparatus configured to operate a MEMS element in an array of MEMS elements forming a display, the apparatus comprising:

a controller configured to control a driver circuit that periodically applies a first potential difference to the MEMS elements, the first potential difference having a magnitude sufficient to actuate the MEMS elements and having a polarity, the controller configured to periodically apply a second potential difference to the MEMS elements, the second potential difference having a magnitude and opposite polarity that is about equal to the first potential difference, wherein the first potential difference and the second potential difference are respectively applied to the MEMS elements at defined times and for defined durations that are dependent on a rate at which image data is written to the MEMS elements of the array, and wherein the first and second potential differences are each applied to the MEMS elements for about equal amounts of time in a given period of display use, the controller further configured to use the potential difference of the first polarity and the potential difference of the opposite polarity to the first polarity To write the same data frame; and

at least one output port configured to communicate, at least in part, the potential difference to the MEMS display elements during the first portion of the display write process.

52. The apparatus of claim 51, further comprising:

a processor in electrical communication with the MEMS element, the processor configured to process image data; and

a memory device in electrical communication with the processor.

53. The apparatus of claim 52, further comprising a processor configured to send at least a portion of the image data to a controller in communication with the MEMS display element.

54. The apparatus of claim 52, further comprising an image source module configured to send the image data to the processor.

55. The apparatus as recited in claim 54, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

56. The apparatus of claim 52, further comprising an input device configured to receive input data and to communicate the input data to the processor.

57. The apparatus of claim 51, wherein the at least one output port configured to communicate the potential difference at least partially to the MEMS display element comprises at least one chip pin.

58. The apparatus of claim 51, wherein the at least one output port configured to at least partially communicate the potential difference to the MEMS display element comprises at least one conductive line.

59. The apparatus of claim 51, wherein the at least one output port configured to communicate the potential difference at least partially to the MEMS display element comprises at least one interface to the driver circuit.

60. The apparatus of claim 51, wherein the at least one output port configured to at least partially communicate the potential difference to the MEMS display element comprises at least one row output port and at least one column output port.

61. An apparatus for updating a display, the apparatus comprising:

means for modulating light; and

means for applying a potential difference to the modulating means, the applying means configured to periodically apply a first potential difference and a second potential difference to the modulating means, the first and second potential differences are of opposite polarity and of approximately equal magnitude sufficient to actuate the modulating means, wherein the first potential difference and the second potential difference are applied to the modulating means at defined times and for defined durations, respectively, that depend on a rate at which image data is written to the modulating means, and wherein said first and second potential differences are each applied to said modulating means for an approximately equal amount of time over a given period of display use, and wherein the applying means is further configured to write the same frame of data using both a potential difference of the first polarity and a potential difference of a polarity opposite to the first polarity.

62. The apparatus according to claim 61, wherein said applying means comprises a driver circuit.

63. The apparatus according to claim 61, wherein the application member comprises at least one output port.

64. The apparatus of claim 63, wherein the output port comprises at least one chip pin.

65. The apparatus of claim 63, wherein the output port comprises at least one conductive line.

66. The apparatus of claim 63, wherein the output port comprises at least one interface to a driver circuit.

67. The apparatus according to claim 61, wherein said means for modulating light comprises an interferometric modulating MEMS device.

68. A method of operating a MEMS element in an array of MEMS elements forming a display, the method comprising:

periodically applying a first potential difference to the MEMS element, the first potential difference having a magnitude sufficient to actuate the MEMS element and having a polarity; and

periodically applying a second potential difference to the MEMS element, the second potential difference having a magnitude approximately equal to the first potential difference and a polarity opposite the polarity of the first potential difference;

wherein the first potential difference and the second potential difference are applied to the MEMS elements at defined times and for defined durations that depend on a rate at which image data is written to MEMS elements of the array, respectively, and wherein the first and second potential differences are each applied to the MEMS elements for an approximately equal amount of time in a given period of display use;

wherein the method comprises writing the same frame of data using both the potential difference of the first polarity and the potential difference of a polarity opposite to the first polarity.

69. An apparatus for displaying an image, the apparatus comprising:

a plurality of MEMS elements in a display; and

a controller configured to activate all of the MEMS elements in a portion of the display and write display data to the portion.

70. The apparatus of claim 69, wherein at least one of the MEMS elements comprises an interferometric modulator.

71. The apparatus of claim 69, further comprising:

a processor in electrical communication with at least one of the plurality of MEMS elements, the processor configured to process image data; and

a memory device in electrical communication with the processor.

72. The apparatus of claim 71, further comprising an image source module configured to send the image data to the processor.

73. The apparatus as recited in claim 72, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

74. The apparatus of claim 71, further comprising an input device configured to receive input data and to communicate the input data to the processor.

75. An apparatus for displaying an image, the apparatus comprising:

a plurality of means for modulating light; and

means for controlling activation of all of the means for modulating light and means for writing display data in a portion of a display.

76. The apparatus according to claim 75, wherein at least one of said plurality of means for modulating light comprises an interferometric modulating MEMS device.

77. The apparatus according to claim 75, wherein said control means comprises a controller.

78. The apparatus of claim 75, wherein the control means further comprises at least one output port in communication with the controller configured to activate the MEMS display element.

79. The apparatus of claim 78, wherein the at least one output port comprises at least one chip pin.

80. The apparatus of claim 78, wherein the at least one output port comprises at least one conductive line.

81. The apparatus of claim 78, wherein the at least one output port comprises at least one interface to a driver circuit configured to activate the MEMS display element.

82. The apparatus of claim 75, wherein the portion comprises a row of MEMS display elements.

83. The apparatus of claim 75, wherein the portion comprises an entire array of MEMS display elements.

84. The apparatus of claim 75, wherein the controlling means is further configured to release all modulating means in the portion of the array prior to writing display data to the portion.

85. A method of writing display data to an array of MEMS display elements, comprising:

activating all MEMS elements in a portion of the array; and

writing display data to the portion of the array.

86. The method of claim 85, wherein the portion of the array comprises a row of MEMS elements of the array.

87. The method of claim 85, wherein the portion comprises an entire array.

88. The method of claim 85, further comprising releasing all MEMS elements in the portion of the array prior to writing display data to the portion of the array.

89. A system configured to write data to an array of MEMS display elements, the system comprising:

a row of drivers;

a row driver; and is

Wherein the row driver and column driver are configured to actuate at least some elements of the array with first and second potential differences, wherein an absolute value of the second potential difference is greater than an absolute value of the first potential difference.

90. The system of claim 89, further comprising:

a processor in electrical communication with the array of MEMS display elements, the processor configured to process image data; and

a memory device in electrical communication with the processor.

91. The system of claim 90, further comprising a controller configured to send at least a portion of the image data to at least one of the row and column drivers.

92. The system of claim 90, further comprising an image source module configured to send the image data to the processor.

93. The system as recited in claim 92, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

94. The system of claim 92, further comprising an input device configured to receive input data and to communicate the input data to the processor.

95. A system configured to write data to an array of MEMS display elements, the system comprising:

means for driving a column of the MEMS display elements; and

means for driving a row of the MEMS display elements;

wherein the row and column drive means are configured to actuate at least some elements of the array with first and second potential differences, wherein the absolute value of the second potential difference is greater than the absolute value of the first potential difference.

96. The system of claim 95, wherein the column driving means comprises a column driver circuit.

97. The system of claim 95, wherein the row driving means comprises a driver circuit.

98. A method of writing display data to an array of MEMS display elements comprising actuating at least some elements of the array with first and second potential differences, wherein the absolute value of the second potential difference is greater than the absolute value of the first potential difference.