Patent Application
20130135269
This disclosure relates to a drive scheme for driving electromechanical display devices that suffer from adhesion forces.
Electromechanical systems include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components (e.g., mirrors) and electronics. Electromechanical systems 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 electromechanical systems device is called an interferometric modulator (IMOD). As used herein, the term interferometric modulator 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 interferometric modulator 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. In an implementation, one plate may include a stationary layer deposited on 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 interferometric modulator. Interferometric modulator 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.
The systems, methods and devices of the 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 method for driving a display element in an array of display elements. The method includes applying a first series of voltages to a first electrode of the display element. The method further includes applying a second series of voltages from a set of voltage levels to a second electrode of the display element to selectively place a movable layer of the display element into an actuated state corresponding to a first position or an un-actuated state corresponding to a second position based on a voltage difference between the first electrode and the second electrode. The method further includes applying a third series of voltages levels using voltage levels from the set of voltage levels to a third electrode of the display element. The second electrode is between the first electrode and the third electrode. The third series of voltage levels are applied to the third electrode such that a non-zero voltage exists between the third electrode and the second electrode during a release time period in which a desired state of the display element is the un-actuated state.
Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for driving a display device. The apparatus includes a display element included in an array of display elements. The display element includes a first electrode. The display element further includes a second electrode. The display element further includes a third electrode. The second electrode is located between the first electrode and the third electrode. The display element further includes a movable layer configured to be in an actuated state in a first position or an un-actuated state in a second position based on a voltage difference between the first electrode and the second electrode. The apparatus further includes a driver circuit configured to apply a first series of voltage levels to the first electrode. The driver circuit is further configured to apply a second series of voltage levels from a set of voltage levels to the second electrode. The first series and second series of voltages levels are applied to selectively place the display element into the actuated or the un-actuated state. The driver circuit is further configured to apply a third series of voltages levels using voltage levels from the set of voltage levels to the third electrode of the display element. The third series of voltage levels are applied to the third electrode such that a non-zero voltage exists between the second electrode and the third electrode during a release time period in which a desired state of the display element is the un-actuated state.
Yet another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for driving a means for displaying in an array of means for displaying. The apparatus includes means for applying a first series of voltages to a first means for conducting of the means for displaying. The apparatus further includes means for applying a second series of voltages from a set of voltage levels to a second means for conducting of the means for displaying to selectively place a movable layer of the means for displaying into an actuated state corresponding to a first position or an un-actuated state corresponding to a second position based on a voltage difference between the first means for conducting and the second means for conducting. The apparatus further includes means for applying a third series of voltages levels using voltage levels from the set of voltage levels to a third means for conducting of the means for displaying. The second means for conducting is between the first means for conducting and the third means for conducting. The third series of voltage levels are applied to the third means for conducting such that a non-zero voltage exists between the third means for conducting and the second means for conducting during a release time period in which a desired state of the means for displaying is the un-actuated state.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a computer program product. The computer program product includes a computer-readable medium. The computer-readable medium includes code for applying a first series of voltages to a first electrode of a display element. The computer-readable medium further includes code for applying a second series of voltages from a set of voltage levels to a second electrode of the display element to selectively place a movable layer of the display element into an actuated state corresponding to a first position or an un-actuated state corresponding to a second position based on a voltage difference between the first electrode and the second electrode. The computer-readable medium further includes code for applying a third series of voltages levels using voltage levels from the set of voltage levels to a third electrode of the display element. The second electrode is between the first electrode and the third electrode. The third series of voltage levels are applied to the third electrode such that a non-zero voltage exists between the third electrode and the second electrode during a release time period in which a desired state of the display element is the un-actuated state.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for driving a display element in an array of display elements. The method includes simultaneously applying a first waveform to a first movable electrode extending along a line of display elements and to a pull up electrode extending along a different line of display elements. The method further includes applying a second waveform to a second movable electrode extending along the different line of display elements to selectively place portions of a movable layer of the different line into either a first position or a second position based on a voltage difference between a fixed electrode and the second movable electrode.
Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for driving a display device. The apparatus includes a driver circuit. The apparatus further includes a line of display elements in an array of display elements. The line of display elements includes a first movable electrode extending along the line of display elements. The line of display elements further includes a pull up electrode extending along the line of display elements. The pull up electrode and a second movable electrode of a different line of display elements in the array of display elements are coupled to a common output of the driver circuit. The pull up electrode may be directly electrically connected to the second movable electrode of the different line of display elements in the array of display elements such that the same waveform is simultaneously applied to the pull up electrode and to the second movable electrode of the different line of display elements.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. 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.
Like reference numbers and designations in the various drawings indicate like elements.
The following detailed description is directed to certain implementations for the purposes of describing the innovative aspects. However, the teachings herein can be applied in a multitude of different ways. The described implementations 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, graphical or pictorial. More particularly, it is contemplated that the implementations may be implemented 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, GPS receivers/navigators, cameras, 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 (e.g., odometer display, etc.), cockpit controls and/or displays, camera view displays (e.g., 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 (e.g., MEMS and non-MEMS), aesthetic structures (e.g., display of images on a piece of jewelry) and a variety of electromechanical systems 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 a person having ordinary skill in the art.
Some implementations of an electromechanical display element may include a movable element, such as a mirror or a deformable mechanical layer, which moves between a first position in which the movable element is in contact with a portion of the display element and a second position in which the movable element is not in contact with the portion of the display element. While in the first position, an adhesion force (e.g., stiction) may be generated between the movable element and the contact portion. Accordingly, it may be advantageous to provide display devices and methods of operation in which the adhesion force may be at least partially reduced or counteracted while the movable element is in the first position. In certain implementations, the display device includes one or more electrodes configured to at least partially reduce or counteract the adhesion force on the movable element. Voltages may be applied to the one or more electrodes to provide an electrostatic force that at least partially counteracts the adhesion force.
In one implementation, the one or more electrodes configured to counteract the adhesion force may be driven using the functionality provided to selectively move the display element between the first and second position. The electrodes may be configured to provide a pull up force that can both speed up the transition from first to second positions as well as ensure this movement for pixels where the adhesion force exceeds a restoring force. For example, voltage levels corresponding to the voltage levels used to drive the movable element may be applied to the one or more electrodes to cause a non-zero voltage to be applied for counteracting an adhesion force during a display refresh. During other periods for writing display data, voltage levels corresponding to the voltage levels used to drive the movable layer may be applied to the one or more electrodes to substantially eliminate any extra electrostatic force. In another implementation, the one or more electrodes configured to counteract the adhesion force may be electrically connected to an electrode used to drive the movable elements extending along another line of display elements to create a non-zero voltage applied for counteracting an adhesion force.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. By taking advantage of functionality used to write display data to display elements, additional driver circuitry needed to drive the pull up electrodes may be simplified or eliminated. The use of pull up electrodes can increase the speed of a release period and also increase the lifetime of the MEMS device. Implementations described herein may reduce the cost and complexity of providing pull up electrodes for enhancing release performance.
An example of a suitable MEMS device, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulators (IMODs) to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMODs can include an absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. 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 interferometric modulator. The reflectance spectrums of IMODs can create fairly broad spectral bands which 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, i.e., by changing the position of the reflector.
The IMOD display device can include a row/column array of IMODs. Each IMOD can include a pair of reflective layers, i.e., a movable reflective layer and a fixed partially reflective layer, positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap or cavity). The movable reflective layer may be moved between at least two positions. In a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a relatively large 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 or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel. In some implementations, the IMOD may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when actuated, reflecting light outside of the visible range (e.g., infrared light). In some other implementations, however, an IMOD 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 pixels to change states. In some other implementations, an applied charge can drive the pixels to change states.
The depicted portion of the pixel array in
In
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 (Cr), 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, the optical stack 16 can include a single semi-transparent thickness of metal or semiconductor which serves as both an optical absorber and conductor, while different, more conductive layers or portions (e.g., of the optical stack 16 or of other structures of the IMOD) can serve to bus signals between IMOD pixels. The optical stack 16 also can include one or more insulating or dielectric layers covering one or more conductive layers or a conductive/absorptive layer.
In some implementations, 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 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 posts 18 and an intervening sacrificial material deposited 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 on the order of 1-1000 um, while the gap 19 may be on the order of <10,000 Angstroms (Å).
In some implementations, each pixel of the IMOD, whether in the actuated or relaxed state, is essentially 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 pixel 12 on the left in
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, e.g., a display array or panel 30. The cross section of the IMOD display device illustrated in
In some implementations, a frame of an image may be created by applying data signals in the form of “segment” voltages along the set of column electrodes, in accordance with the desired change (if any) to the state of the pixels in a given row. Each row of the array can be addressed in turn, such that the frame is written one row at a time. To write the desired data to the pixels in a first row, segment voltages corresponding to the desired state of the pixels in the first row can be applied on the column electrodes, and a first row pulse in the form of a specific “common” voltage or signal can be applied to the first row electrode. The set of segment voltages can then be changed to correspond to the desired change (if any) to the state of the pixels in the second row, and a second common voltage can be applied to the second row electrode. In some implementations, the pixels in the first row are unaffected by the change in the segment voltages applied along the column electrodes, and remain in the state they were set to during the first common voltage row pulse. This process may be repeated for the entire series of rows, or alternatively, columns, in a sequential fashion to produce the image frame. The frames can be refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second.
The combination of segment and common signals applied across each pixel (that is, the potential difference across each pixel) determines the resulting state of each pixel.
As illustrated in
When a hold voltage is applied on a common line, such as a high hold voltage VCHOLD
When an addressing, or actuation, voltage is applied on a common line, such as a high addressing voltage VCADD
In some implementations, hold voltages, address voltages, and segment voltages may be used which always produce the same polarity potential difference across the modulators. In some other implementations, signals can be used which alternate the polarity of the potential difference of the modulators. Alternation of the polarity across the modulators (that is, alternation of the polarity of write procedures) may reduce or inhibit charge accumulation which could occur after repeated write operations of a single polarity.
During the first line time 60a: a release voltage 70 is applied on common line 1; the voltage applied on common line 2 begins at a high hold voltage 72 and moves to a release voltage 70; and a low hold voltage 76 is applied along common line 3. Thus, the modulators (common 1, segment 1), (1,2) and (1,3) along common line 1 remain in a relaxed, or unactuated, state for the duration of the first line time 60a, the modulators (2,1), (2,2) and (2,3) along common line 2 will move to a relaxed state, and the modulators (3,1), (3,2) and (3,3) along common line 3 will remain in their previous state. With reference to
During the second line time 60b, the voltage on common line 1 moves to a high hold voltage 72, and all modulators along common line 1 remain in a relaxed state regardless of the segment voltage applied because no addressing, or actuation, voltage was applied on the common line 1. The modulators along common line 2 remain in a relaxed state due to the application of the release voltage 70, and the modulators (3,1), (3,2) and (3,3) along common line 3 will relax when the voltage along common line 3 moves to a release voltage 70.
During the third line time 60c, common line 1 is addressed by applying a high address voltage on common line 1. Because a low segment voltage 64 is applied along segment lines 1 and 2 during the application of this address voltage, the pixel voltage across modulators (1,1) and (1,2) is greater than the high end of the positive stability window (i.e., the voltage differential exceeded a predefined threshold) of the modulators, and the modulators (1,1) and (1,2) are actuated. Conversely, because a high segment voltage 62 is applied along segment line 3, the pixel voltage across modulator (1,3) is less than that of modulators (1,1) and (1,2), and remains within the positive stability window of the modulator; modulator (1,3) thus remains relaxed. Also during line time 60c, the voltage along common line 2 decreases to a low hold voltage 76, and the voltage along common line 3 remains at a release voltage 70, leaving the modulators along common lines 2 and 3 in a relaxed position.
During the fourth line time 60d, the voltage on common line 1 returns to a high hold voltage 72, leaving the modulators along common line 1 in their respective addressed states. The voltage on common line 2 is decreased to a low address voltage 78. Because a high segment voltage 62 is applied along segment line 2, the pixel voltage across modulator (2,2) is below the lower end of the negative stability window of the modulator, causing the modulator (2,2) to actuate. Conversely, because a low segment voltage 64 is applied along segment lines 1 and 3, the modulators (2,1) and (2,3) remain in a relaxed position. The voltage on common line 3 increases to a high hold voltage 72, leaving the modulators along common line 3 in a relaxed state.
Finally, during the fifth line time 60e, the voltage on common line 1 remains at high hold voltage 72, and the voltage on common line 2 remains at a low hold voltage 76, leaving the modulators along common lines 1 and 2 in their respective addressed states. The voltage on common line 3 increases to a high address voltage 74 to address the modulators along common line 3. As a low segment voltage 64 is applied on segment lines 2 and 3, the modulators (3,2) and (3,3) actuate, while the high segment voltage 62 applied along segment line 1 causes modulator (3,1) to remain in a relaxed position. Thus, at the end of the fifth line time 60e, the 3×3 pixel array is in the state shown in
In the timing diagram of
The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,
As illustrated in
In implementations such as those shown in
The process 80 continues at block 84 with the formation of a sacrificial layer 25 over the optical stack 16. The sacrificial layer 25 is later removed (e.g., at block 90) to form the cavity 19 and thus the sacrificial layer 25 is not shown in the resulting interferometric modulators 12 illustrated in
The process 80 continues at block 86 with the formation of a support structure e.g., a post 18 as illustrated in
The process 80 continues at block 88 with the formation of a movable reflective layer or membrane such as the movable reflective layer 14 illustrated in
The process 80 continues at block 90 with the formation of a cavity, e.g., cavity 19 as illustrated in
When a movable reflective layer 14 is in the actuated position, it may come in contact with a portion of the optical stack 16 of the IMOD 12. An adhesion force may be generated between the movable reflective layer 107 and the portion of the optical stack 16. The adhesion force tends to adhere the deformed portion of the movable reflective layer 14 to a portion of the optical stack 16 of the IMOD 12.
The adhesion force may be caused by forces such as, for example, capillary, electrostatic, or van der Waals forces, or other intermolecular forces. The adhesion force may depend on a range of factors including, for example, the materials used, the shape, orientation, and configuration of structures in the IMOD 12, the roughness of the contact surfaces, and ambient humidity and pressure. The adhesion force may depend on the manner in which the structures within the IMOD 12 are operated, for example, through impulsive motions involving large accelerations or through more gentle quasi-static motions. This adhesion force can increase the time it takes for the reflective layer 14 to release from an actuated position and in extreme cases (where the adhesion force exceeds the restoring force), the reflective layer 14 may not release when the electrostatic attractive force is removed leading to a condition that may be referred to as “stiction.”. “Stiction” is a commonly used term that may include some of the adhesion effects discussed herein.
The process of actuating and de-actuating the IMOD 12 is described herein with reference to
The adhesion force may alter the nature of this actuation and release cycle. In some implementations of the IMOD pixel 12, the adhesion force at the contact area 913 of the IMOD 12 may be sufficiently large that adhesion inhibits, or in some cases prevents, the release of the movable reflective layer 14 as the voltage difference drops below the second threshold. Also, when the movable reflective layer 14 is released by reducing or eliminating the voltage difference between the movable layer and the optical stack 16, the only force pulling the movable layer 14 up is a mechanical restoring force. Because no electrical force works to release the movable layer in these implementations, the time taken to release the membrane may be significantly longer than the time used to actuate it. Accordingly, it is advantageous to provide architectures that at least partially reduce or counteract the adhesion force and that speed the release process.
In the implementation shown in
The IMOD display element 12 shown in
In some implementations of the IMOD display element 12, at least portions of the electrodes 912a and 912b are disposed higher than the movable reflective layer 14 when the movable reflective layer 14 is in the first position and therefore higher than the second electrode 902. In certain implementations, at least a portion of each of the electrodes 912a and 912b protrudes away from the support posts 18a and 18b, respectively, such that these portions are disposed above (e.g., higher than) at least a portion of the movable reflective layer 14 when the movable reflective layer 14 is in the first position (
In some implementations of the IMOD display element 12, voltages are applied to the electrodes 901, 902, and 903 so that a net electrostatic force on the movable reflective layer 14 at least partially reduces or counteracts the adhesion force on the movable reflective layer 14 in the first position. The voltages may have various ranges of magnitudes and frequencies and may be applied to induce displacements, oscillations, and/or vibrations of the movable reflective layer 14 to assist in moving the movable reflective layer 14 from the first position to the second position. In certain implementations, a voltage difference is applied between the third electrode 903 (e.g., the electrodes 912a, 912b) and the second electrode 902 (e.g., an electrically conductive portion of the movable reflective layer 14). The voltage difference can have various ranges of magnitudes and frequencies and can include one or more relatively short duration impulses. In various implementations, the third electrode 903 is electrically connected to one or more voltage sources by traces or wires that lead off of the display array 30 to the array driver 22 (see
The voltage difference applied between the second and third electrodes 902 and 903 causes net electrostatic forces indicated by arrows 908a and 908b to act on the movable reflective layer 14. In certain implementations, portions of the electrodes 912a and 912b protrude directly above at least portions of the bending regions 906a and 906b so that the net electrostatic forces 908a and 908b have reasonably large perpendicular components in the bending regions 906a and 906b that tend to pull the movable reflective layer 14 away from the portion 913. In certain such implementations, the electrostatic forces 908a and 908b may at least partially reduce or counteract the adhesion force and may assist in moving the movable reflective layer 14 from the first position to the second position. Without subscribing to any particular theory, the net electrostatic force 908a applied in the bending region 906a may induce crack opening at an edge of a contact interface between the movable reflective layer 14 and the portion 913. The crack may propagate across the contact interface, assisting the movable reflective layer 14 to peel away from the portion 913 and to move from the first position to the second position. The net electrostatic force 908b applied in the bending region 906b may act in a similar manner, and in certain implementations cracks may open at opposing edges of the contact interface and propagate across the interface. In other implementations different configurations, orientations, and numbers of electrodes (e.g., one) can be used, for example, to initiate crack opening and facilitate release of the movable reflective layer 14.
The magnitudes of the electrostatic forces 764a, 764b at the bending regions 760a, 760b to facilitate release from the driven to the un-driven state typically are much smaller than if the forces were applied to a central region of the reflective element 107. Accordingly, smaller voltage differences (e.g., between the second and third electrodes 902 and 903) can be applied to the IMOD display element 12. Moreover, in some implementations, the electrodes 912a and 912b reduce electrostatic instability and collapse of the movable reflective layer 14 onto the dielectric layer 904, which can be a problem in some closing-gap devices. Further, in certain implementations, voltage impulses having a duration that is shorter than a typical release time of the IMOD display element 12 can be used to facilitate movement of the movable reflective layer 14 from the driven state to the un-driven state.
In some cases, the third electrode 903 may use dedicated driver circuitry and/or power supply circuitry for selectively driving additional voltage levels to the third electrode 903. This additional driver circuitry (e.g., in addition to the driver circuitry such as the row driver circuit 24 and column driver circuit 26 provided to actuate and release an IMOD display element 12) may increase the expense and complexity of the display device. To reduce the need for this additional circuitry, certain aspects of various implementations are directed to driving the third electrode 903 using at least portions of the functionality used to drive the common line and segment lines as described above. The array driver 22 or substantial portions of the array driver 22 may be adapted and used to additionally drive the third electrode 903. In one aspect, the third electrode 903 may be driven without requiring any additional analog voltage levels as compared to the voltage levels used to drive the first and second electrodes 901 and 902 (e.g., the voltage levels described above with reference to
The array driver 22 may apply a series of voltages (i.e., a waveform) to the third electrode 903 to counteract the adhesion force during actuation and release periods when writing lines of display data. As described above, a generated voltage across electrodes 901 and 902 may be referred to herein as the “pixel voltage.” The voltage that is generated between the second electrode 902 and the third electrode 903 to counteract the adhesion force may be referred to herein as the “pull voltage.” Aspects of certain implementations are directed to applying voltage waveforms to the electrodes 901, 902, and 903 to produce a non-zero pull voltage during release periods while also ensuring that the pixel voltage remains substantially unaffected by any pull voltage (i.e., the pull voltage does not work significantly against the ability to actuate an IMOD display element 12) when writing display data to the array 30.
In one aspect, the third electrode 903 may be positioned in a layer that extends along the same pixel line along which the second electrode 902 extends. For example, the third electrode 903 may extend along the pixel line of the movable reflective layer 14 including the second electrode 902. In this way, the row driver circuit 24 may be adapted to drive both the second and third electrodes 902 and 903.
More specifically,
During periods other than the release period, the third electrode may be simultaneously driven with the same voltage levels being applied to second electrode 902 such that the third electrode waveform 1106 may be the same as the second electrode waveform 1104. As the second electrode waveform 1104 and the third electrode waveform 1106 are the same during these periods, substantially zero voltage difference exists between the third electrode 903 and the second electrode 902. In other words, the pull voltage may be maintained at substantially zero outside the release period. The third electrode waveform 1106, outside the release period, may therefore use the same voltage levels used for the second electrode waveform 1104. While some additional driver circuitry may be needed to provide the third electrode waveform 1104, the cost and complexity may be reduced as the same voltage levels used to provide the second electrode waveform 1104 may be used. It should be appreciated that the second electrode 902 may be held at VCHOLD
During times other than the release period, the pull voltage 1202 is substantially zero as the waveforms 1104 and 1106 applied to both the second electrode 902 and the third electrode 903 are substantially equivalent. As a result, a non-zero pull voltage is applied substantially only during release periods to help to counteract stiction and ensure that any actuated IMOD display element 12 is released. According to this implementation, no other voltage levels are used beyond what is already provided to drive the second electrode 902 for writing display data to each IMOD display element 12.
In other implementations, it may be additionally desirable to further reduce the number of voltage levels used to drive the third electrode 903.
The actual voltage levels applied to the electrodes 901, 902, and 903 may vary substantially according to the design of the display device. In some implementations, the difference between VCADD
In block 1504, an array driver 22 may simultaneously apply a substantially identical waveform to both the second electrode 902 and the third electrode 903 of the line of display elements during other periods. The other periods may correspond to a time in which display data is written to display elements for driving them to an actuated state. As a result of the waveforms being substantially the same for each of the second and third electrodes 902 and 903, a substantially zero pull-voltage may be applied during the addressing periods so as not to work against actuation of individual IMOD elements. Substantially identical waveforms may correspond to two waveforms applied to the second and third electrodes 902 and 903 that do not substantially affect actuation or hold states. For example, the waveforms 1304 and 1306 applied during the release period as shown in
In some cases, the implementations described above with reference to
During a release period for the first line, the waveform 1706 applied on the second electrode 902a of the first line will be applied on the third electrode 903b of the second line just before the beginning of the release period of the second line. More specifically, as shown in
Per the implementation described with reference to
The implementations described with reference to
In block 2006, the array driver 22 may apply a third series of voltages levels (i.e., a third waveform) using voltage levels from the set of voltage levels to a third electrode 903 of the display element. The third series of voltage levels may include only those voltage levels from the set of voltage levels. The second electrode 902 may be between the first electrode 901 and the third electrode 903. The third series of voltage levels may be applied to the third electrode 903 such that a non-zero voltage (i.e., a non-zero pull voltage) exists between the third electrode 903 and the second electrode 902 during a release time period in which a desired state of the display element is the un-actuated state. This non-zero voltage may be applied to at least partially reduce or counteract an adhesion force generated between the movable layer and a first layer including the first electrode.
In some implementations, the third series of voltages levels may be substantially equal to the second series of voltages during an addressing time period that is different than the release time period. This may minimize any voltage between the third electrode 902 and second electrode 902 during the addressing time period so as not to interfere with actuation of a display element. The third series of voltage levels may include a smaller subset of voltage levels of the set of voltage levels (e.g., only VCHOLD
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 interferometric modulator display, as described herein.
The components of the display device 40 are schematically illustrated in
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, e.g., 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 or n. 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 is 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), NEV-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 or 4G 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, 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 is 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's x-y matrix of pixels.
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 (e.g., an IMOD controller). Additionally, the array driver 22 can be a conventional driver or a bi-stable display driver (e.g., an IMOD display driver). Moreover, the display array 30 can be a conventional display array or a bi-stable display array (e.g., a display including an array of IMODs). In some implementations, the driver controller 29 can be integrated with the array driver 22. Such an implementation is common in highly integrated systems such as cellular phones, watches and other small-area displays.
In some implementations, the input device 48 can be configured to allow, e.g., 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, 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 as are well known in the art. For example, the power supply 50 can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. 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.
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 may also be implemented as a combination of computing devices, e.g., 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.
If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The steps of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine readable medium and computer-readable medium, which may be incorporated into a computer program product.
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. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. 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 the IMOD 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, this should not be understood as requiring that such operations 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.
