Patent Abstract:
A method and system for fabricating a light guide is disclosed. The method and system comprise providing a light guide element which includes a plurality of scattering elements located therein and adjusting at least a portion of the scattering elements to maintain their optical scattering character. The present invention provides a system and method for fabricating a front light technology that is inexpensive and can compete on a cost basis with LCD backlight technologies while maintaining reasonable performance.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates generally to displays and more specifically to light guides for such displays. 
     BACKGROUND OF THE INVENTION 
     Microelectromechanical systems (MEMS) include micro mechanical 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 called an interferometric modulator. 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 certain embodiments, 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. In a particular embodiment, 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. As described herein in more detail, the position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Such 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. One area where constant improvement is needed is the light guides which are utilized in the flat panel displays. 
     Current light technologies for reflective flat panel displays are relatively expensive and difficult to fabricate. In a conventional approach, a light guide consists of two pieces of glass fastened together with a sealing agent, such as a bead of epoxy between the two pieces of glass. In the conventional approach, a piece of plastic is fabricated which has a “stairstep” pattern on it. A light guide is attached to the edge of this discrete piece of plastic, and the light is bounced through the plastic. At certain points where the light hits the stairstep structure the light will bounce down into the display. 
     The “stairstep” features on such a piece of glass require a manufacturing process which is very difficult to utilize using low cost molding methods. What is generally required is to make an expensive molding tool, which can then only be used for fabricating a limited number of parts. The light is very sensitive to the level of defects which may result from the “stairstep” feature. If defects such as a particle in the mold, or a burr in the mold occur, such defects will appear as optical defects to the viewer. Ghosting effects may also result, or double images, as a result of this conventional manufacturing process. 
     Accordingly, what is needed is a system and method for overcoming the above-mentioned problems. The present invention addresses such a need. 
     SUMMARY OF THE INVENTION 
     A method and system for fabricating a light guide is disclosed. The method and system comprise providing a light guide element which includes a plurality of scattering elements located therein and adjusting at least a portion of the scattering elements to maintain their optical scattering character. 
     The present invention provides a system and method for fabricating a lighting technology that is inexpensive and can compete on a cost basis with LCD backlight technologies while maintaining reasonable performance. 
    
    
     
       BRIEF DESCRIPTION OF THE 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 relaxed position and a movable reflective layer of a second interferometric modulator is in an actuated position. 
         FIG. 2A  is a simple flow chart of a method for fabricating a light guide element in accordance with the present invention. 
         FIG. 2B  is a flow chart of a method for fabricating a light guide in accordance with the present invention. 
         FIG. 3  shows a light guide film loaded with scattering elements where there is no preferential direction for light output elements. 
         FIG. 4A  shows one embodiment of a light guide element loaded with scattering elements in accordance with the present invention. 
         FIG. 4B  shows a second embodiment of a light guide element loaded with scattering elements in accordance with the present invention. 
         FIG. 4C  shows a third embodiment of a light guide element loaded with scattering elements in accordance with the present invention. 
         FIG. 5  illustrates a processed light guide element in accordance with the present invention. 
         FIG. 6  illustrates providing an ultraviolet exposure to a top side of the light guide element  100 ′″. 
         FIG. 7  illustrates the bottom portion of the scattering elements is then exposed to a second UV wavelength which deactivates the coating thereby preventing it from turning dark. 
         FIG. 7A  illustrates the light guide element placed on an interferometric modulator substrate via an adhesive layer. 
         FIG. 8  is a system block diagram illustrating one embodiment of an electronic device incorporating a 3×3 interferometric modulator display. 
         FIG. 9  is a diagram of movable mirror position versus applied voltage for one exemplary embodiment of an interferometric modulator of  FIG. 1 . 
         FIG. 10  is an illustration of a set of row and column voltages that may be used to drive an interferometric modulator display. 
         FIGS. 11A and 11B  illustrate one exemplary timing diagram for row and column signals that may be used to write a frame of display data to the 3×3 interferometric modulator display of  FIG. 8 . 
         FIGS. 12A and 12B  are system block diagrams illustrating an embodiment of a visual display device comprising a plurality of interferometric modulators. 
         FIG. 13A  is a cross section of the device of  FIG. 1 . 
         FIG. 13B  is a cross section of an alternative embodiment of an interferometric modulator. 
         FIG. 13C  is a cross section of another alternative embodiment of an interferometric modulator. 
         FIG. 13D  is a cross section of yet another alternative embodiment of an interferometric modulator. 
         FIG. 13E  is a cross section of an additional alternative embodiment of an interferometric modulator. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. As will be apparent from the following description, the embodiments 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 embodiments 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, display of camera views (e.g., display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., display of images on 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 gap 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 relaxed position, the movable reflective layer is positioned at a relatively large distance from a fixed partially reflective layer. In the second position, referred to herein as the actuated position, the movable reflective 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 an overall reflective or non-reflective state for each pixel. 
     The depicted portion of the pixel array in  FIG. 1  includes two adjacent interferometric modulators  12   a  and  12   b . In the interferometric modulator  12   a  on the left, a movable reflective layer  14   a  is illustrated in a relaxed position at a predetermined distance from an optical stack  16   a , which includes a partially reflective layer. In the interferometric modulator  12   b  on the right, the movable reflective layer  14   b  is illustrated in an actuated position adjacent to the optical stack  16   b.    
     The optical stacks  16   a  and  16   b  (collectively referred to as optical stack  16 ), as referenced herein, typically comprise of several fused layers, which can include an electrode layer, such as indium tin oxide (ITO), a partially reflective layer, such as chromium, and a transparent dielectric. The optical stack  16  is thus 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 partially reflective layer can be formed from a variety of materials that are partially reflective such as various metals, 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 embodiments, the layers of the optical stack are patterned into parallel strips, and may form row electrodes in a display device as described further below. The movable reflective layers  14   a ,  14   b  may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of  16   a ,  16   b ) deposited on top of posts  18  and an intervening sacrificial material deposited between the posts  18 . When the sacrificial material is etched away, the movable reflective layers  14   a ,  14   b  are separated from the optical stacks  16   a ,  16   b  by a defined gap  19 . A highly conductive and reflective material such as aluminum may be used for the reflective layers  14 , and these strips may form column electrodes in a display device. 
     With no applied voltage, the gap  19  remains between the movable reflective layer  14   a  and optical stack  16   a , with the movable reflective layer  14   a  in a mechanically relaxed state, as illustrated by the pixel  12   a  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 reflective layer  14  is deformed and is forced against the optical stack  16 . A dielectric layer (not illustrated in this Figure) within the optical stack  16  may prevent shorting and control the separation distance between layers  14  and  16 , as illustrated by pixel  12   b  on the right in  FIG. 1 . The behavior is the same regardless of the polarity of the applied potential difference. In this way, 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. 
     This type of system utilizes a light guide element thereon as part of the optical stack of the reflective display. A system and method in accordance with the present invention provides an improved light guide element that is easy to fabricate and cost effective. To describe the features of the light guide element in more detail refer now to the following description in conjunction with the accompanying Figures. 
     The present invention provides for fabricating a light guide which is cheaper, more robust and more efficient for reflective display than existing technologies. The method of fabrication described in the present invention simplifies the manufacturing process, which is expensive with conventional technology because of the difficulty in fabricating very fine features on the light guide. As before mentioned, such conventional processes require expensive molding tools which can only be used a limited number of times. As a result of the method described in the present invention, less expensive fabricating processes may be utilized. Thinner light guides are also possible, creating more flexibility for product design and less weight and bulk. 
     The present invention provides a method for fabricating a light guide element including optical scattering elements. In one embodiment of the present invention, the scattering elements are embedded in the bulk of the light guide material or the bulk of the film that will be applied to the display substrate.  FIG. 2A  is a simple flow chart of a method for fabricating a light guide element in accordance with the present invention. First, a plurality of scattering elements are provided, via step  72 . Next, the plurality of scattering elements is loaded into a light guide film to provide a light guide element, via step  74 . Finally, at least a portion of the scattering elements are adjusted to maintain their optical scattering character, via step  76 . 
     The scattering elements could be a variety of elements including but not limited to highly reflective polymers or metals, such as silver, aluminum, nickel, chrome or the like which inherently have optical scattering characteristics. In another example the scattering elements could be comprised of TiO 2  that is coated with a photochromic coating that is activated in some manner to adjust the scattering elements optical scattering direction. 
     In one embodiment, the scattering elements are coated with a photochromic coating that forms a black mask when exposed to UV. By exposing the display side of the light control film or front light guide, the side of the scattering elements facing the display array maintain their optical scattering character while the display side forms a black mask. To describe the features of the embodiment in more detail, refer now to the following description in conjunction with the accompanying figures. 
       FIG. 2B  is a flow chart of a method for fabricating a light guide in accordance with the present invention. First, a plurality of optical scattering elements are provided, via step  82 . The scattering elements for example could be comprised of TiO 2 . A portion of the plurality of scattering elements is coated with a photochromic coating, via step  84 . The photochromic coating could be for example, in the classes of triarylmethanes, stilbenes, azastilbenes, nitrones, fulgides, spiropyrans, naphthopyrans, spiro-oxazines, and the like. The plurality of scattering elements are loaded into a light guide film to provide a light guide element, via step  86 . Thereafter, the coating of the at least a portion of scattering elements is activated by a first UV exposure on one side to darken and form a mask on the one side, via step  88 . The first UV exposure may be within a first range of wavelengths such as 300-400 nanometers. A second UV exposure is provided to the side opposite of the one side to deactivate the coating on the side opposite and ensure that it will not darken, via step  90 . The second UV exposure may be within a second range of wavelengths such as 300-400 nanometers such that the second UV exposure is different from the first exposure. 
     A method and system in accordance with the present invention allows for the fragile “stairstep” utilized in the conventional approach to be eliminated.  FIG. 3  shows a light guide film  100  loaded with scattering elements where there is no preferential direction for light output. As is seen, a thin relatively flat sheet is fabricated, and then filled with reflective particles, the scattering elements  104 . The elimination of the “stairstep” pattern as before mentioned allows for much thinner plastic to be utilized, from 0.5 to 1.0 millimeters, for example. Utilization of the thinner plastic eliminates the need to build a very fine mold, and instead allows for building a flat mold or injection mold, compression mold, spincasting, extrusion molding, blow molding or other molding processes, thereby allowing a more cost-efficient manufacturing process. 
     In an embodiment in accordance with the present invention, the scattering elements are embedded in the bulk of the light guide material or the bulk of the film that will be applied to the display substrate.  FIG. 4A  shows a first embodiment of a light guide element  100 ′ loaded with scattering elements  104   a - n  in accordance with the present invention. In this embodiment, the top portion  105   a - n  of the scattering elements is masked, so that the top portion  105   a - n  of the scattering elements absorb the light. Varying percentages of masking could be utilized. The scattering elements  104   a - n  should be distributed in a random fashion for maximum effect. In another embodiment of the present invention, for example, a portion of scattering elements  104   a - n  might be masked at 10% coverage, another portion of scattering elements at 40% coverage, and another portion of scattering elements  104   a - n  might be masked at 70% coverage. Other percentages of masking might also be utilized in conjunction with one another, the masked scattering elements of varying coverage randomly dispersed among each other. 
       FIG. 4B  shows a second embodiment of a light guide element  100 ′ with scattering elements  204   a - n . As is seen, some of scattering elements  204   a - n  are within the light guide and some protrude from a top portion. One of skill in the art will recognize that scattering elements  204  may all protrude from the surface of the light guide element  100 ′ (rather than some buried and some protruding, as illustrated in  FIG. 4B ), with more or less of each scattering element  204  protruding from the surface than is illustrated in  FIG. 4B . For example,  FIG. 4B  illustrates each scattering element  204  having more surface area inside of light guide  100 ′ than outside, however in other embodiments there may be an equal amount of surface area of a scattering element  204  inside and outside the light guide  100 ′, or there may be more surface area of a scattering element  204  outside of the light guide  100 ′ rather than inside. 
       FIG. 4C  shows a third embodiment of a light guide element  100 ′ with scattering elements  304   a - n . As is seen, all of the scattering elements  304   a - n  in this third embodiment are located within the top portion of the light guide  100 ′. All of the above-described embodiments can be utilized to provide the appropriate light output. One of ordinary skill in the art readily recognizes that a variety of types of scattering elements could be utilized in a variety of configurations and their use would be within the spirit and scope of the present invention. 
       FIG. 5  illustrates a processed light guide element  100 ″ in accordance with the present invention. As is seen, the scattering elements  104 ″ are coated with a photochromic coating  106 . Existing coating technologies provide for the possibility of applying a very thin coat of photochromic coating. In one approach in accordance with the present invention, particles coated with TiO2, for example, might be immersed for coating, and when removed, the particles would have a very thin coating of UV sensitive material. 
       FIG. 6  illustrates providing an ultraviolet exposure to a top side of the light guide element  100 ′″. The element with the coated UV sensitive particles embedded within it is then exposed to UV wavelengths of a certain frequency, which activates the coating on the scattering elements  104 ′″. When the top side is exposed to the specified wavelength of UV, a portion  105 ′ of the top of the coating on the scattering particles will darken. Referring now to  FIG. 7 , the bottom portion  112 ′ of the scattering elements  104 ′″ is then exposed to a second UV wavelength which deactivates the coating thereby preventing it from turning dark. The result is a light guide element  100 ″″ with embedded scattering particles which are masked on one side. As a result in this embodiment there is a preferential direction for light away from the display side. 
       FIG. 7A  illustrates the light guide element  100 ″″ placed on an interferometric modulator substrate  190  via an adhesive layer  192 . In a preferred embodiment the light guide film is indexed matched to the interferometric modulator sensor. As before mentioned, the optical scattering elements embedded in the bulk of the light guide material may be made of material such as TiO 2 , although a number of other materials may also be utilized. 
     Accordingly, a light guide element in accordance with the present invention can be utilized advantageously in an interferometric modulator display application such as will be described in detail hereinbelow. 
       FIGS. 8 through 11B  illustrate one exemplary process and system for using an array of interferometric modulators in a display application. 
       FIG. 8  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 includes a processor  21  which may be any general purpose single- or multi-chip microprocessor such as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®, Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any special purpose microprocessor such as a digital signal processor, microcontroller, or a 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 driver  22 . In one embodiment, the array driver  22  includes a row driver circuit  24  and a column driver circuit  26  that provide signals to a display array or panel  30 . The cross section of the array illustrated in  FIG. 1  is shown by the lines  1 - 1  in  FIG. 8 . For MEMS interferometric modulators, the row/column actuation protocol may take advantage of a hysteresis property of these devices illustrated in  FIG. 9 . It may require, for example, a 10 volt potential difference to cause a movable layer to deform from the relaxed 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. 9 , the movable layer does not relax completely until the voltage drops below 2 volts. There is thus a range of voltage, about 3 to 7 V in the example illustrated in  FIG. 9 , where there exists a window of applied voltage within which the device is stable in either the relaxed or actuated state. This is referred to herein as the “hysteresis window” or “stability window.” For a display array having the hysteresis characteristics of  FIG. 9 , the row/column actuation protocol can 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 relaxed 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. After being written, each pixel sees a potential difference within the “stability window” of 3-7 volts in this example. This feature makes the pixel design illustrated in  FIG. 1  stable under the same applied voltage conditions in either an actuated or relaxed pre-existing state. Since each pixel of the interferometric modulator, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and moving reflective layers, this stable state can be held at a voltage within the hysteresis window with almost no power dissipation. Essentially no current flows into the pixel if the applied potential is fixed. 
     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 asserted set of 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 may be repeated for the entire series of rows in a sequential fashion to produce the frame. Generally, 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. 
       FIGS. 10 ,  11 A and  11 B illustrate one possible actuation protocol for creating a display frame on the 3×3 array of  FIG. 8 .  FIG. 10  illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves of  FIG. 9 . In the  FIG. 10  embodiment, actuating a pixel involves setting the appropriate column to −V bias , and the appropriate row to +ΔV, which may correspond to −5 volts and +5 volts respectively Relaxing the pixel is accomplished by setting the appropriate column to +V bias , and the appropriate row to the same +ΔV, producing a zero volt potential difference across the pixel. In those rows where the row voltage is held at zero volts, the pixels are stable in whatever state they were originally in, regardless of whether the column is at +V bias , or −V bias . As is also illustrated in  FIG. 10 , it will be appreciated that voltages of opposite polarity than those described above can be used, e.g., actuating a pixel can involve setting the appropriate column to +V bias , and the appropriate row to −ΔV. In this embodiment, releasing the pixel is accomplished by setting the appropriate column to −V bias , and the appropriate row to the same −ΔV, producing a zero volt potential difference across the pixel. 
       FIG. 11  is a timing diagram showing a series of row and column signals applied to the 3×3 array of  FIG. 2  which will result in the display arrangement illustrated in  FIG. 11A , where actuated pixels are non-reflective. Prior to writing the frame illustrated in  FIG. 11A , 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 relaxed states. 
     In the  FIG. 11A  frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) are actuated. 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, because all the 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 actuates the (1,1) and (1,2) pixels and relaxes 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 actuate pixel (2,2) and relax 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. 11A . 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. 11A . It will be appreciated that the same procedure can be employed for arrays of dozens 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 systems and methods described herein. 
       FIGS. 12A and 12B  are system block diagrams illustrating an embodiment of a display device  40 . The display device  40  can be, for example, a cellular or mobile telephone. However, the same components of display device  40  or slight variations thereof are also illustrative of various types of display devices such as televisions and portable media players. 
     The display device  40  includes a housing  41 , a display  30 , an antenna  43 , a speaker  44 , an input device  48 , and a microphone  46 . The housing  41  is generally formed from any of a variety of manufacturing processes as are well known to those of skill in the art, 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. In one embodiment the housing  41  includes 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  of exemplary display device  40  may be any of a variety of displays, including a bi-stable display, as described herein. In other embodiments, the display  30  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  30  includes an interferometric modulator display, as described herein. 
     The components of one embodiment of exemplary display device  40  are schematically illustrated in  FIG. 12B . The illustrated exemplary display device  40  includes a housing  41  and can include additional components at least partially enclosed therein. For example, in one embodiment, the exemplary display device  40  includes a network interface  27  that includes an antenna  43  which is coupled to a transceiver  47 . The transceiver  47  is connected to a processor  21 , which is connected to conditioning hardware  52 . The conditioning hardware  52  may be configured to condition a signal (e.g. filter a signal). The conditioning hardware  52  is connected to a speaker  45  and a microphone  46 . The processor  21  is also connected to an input device  48  and a driver controller  29 . The driver controller  29  is coupled to a frame buffer  28 , and to an array driver  22 , which in turn is coupled to a display array  30 . A power supply  50  provides power to all components as required by the particular exemplary display device  40  design. 
     The network interface  27  includes the antenna  43  and the transceiver  47  so that the exemplary display device  40  can communicate with one ore more devices over a network. In one embodiment the network interface  27  may also have some processing capabilities to relieve requirements of the processor  21 . The antenna  43  is any antenna known to those of skill in the art for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.11 standard, including IEEE 802.11 (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  47  pre-processes 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 processes signals received from the processor  21  so that they may be transmitted from the exemplary display device  40  via the antenna  43 . 
     In an alternative embodiment, the transceiver  47  can be replaced by a receiver. In yet another alternative embodiment, network interface  27  can be replaced by an image source, which can store or generate image data to be sent to the processor  21 . 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. 
     Processor  21  generally controls the overall operation of the exemplary 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  then sends the processed data to the driver controller  29  or to 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. 
     In one embodiment, the processor  21  includes a microcontroller, CPU, or logic unit to control operation of the exemplary display device  40 . Conditioning hardware  52  generally includes amplifiers and filters for transmitting signals to the speaker  45 , and for receiving signals from the microphone  46 . Conditioning hardware  52  may be discrete components within the exemplary display device  40 , or may be incorporated within the processor  21  or other components. 
     The driver controller  29  takes the raw image data generated by the processor  21  either directly from the processor  21  or from the frame buffer  28  and reformats the raw image data appropriately for high speed transmission to the array driver  22 . Specifically, the driver controller  29  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  30 . Then the driver controller  29  sends the formatted information to the array driver  22 . Although a driver controller  29 , such as a 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. They 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 . 
     Typically, the array driver  22  receives the formatted information from the driver controller  29  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&#39;s x-y matrix of pixels. 
     In one embodiment, the driver controller  29 , array driver  22 , and display array  30  are appropriate for any of the types of displays described herein. For example, in one embodiment, driver controller  29  is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, array driver  22  is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, a driver controller  29  is integrated with the array driver  22 . Such an embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment, display array  30  is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators). 
     The input device  48  allows a user to control the operation of the exemplary display device  40 . In one embodiment, input device  48  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  46  is an input device for the exemplary display device  40 . When the microphone  46  is used to input data to the device, voice commands may be provided by a user for controlling operations of the exemplary display device  40 . 
     Power supply  50  can include a variety of energy storage devices as are well known in the art. For example, in one embodiment, power supply  50  is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment, power supply  50  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  50  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  22 . Those of skill in the art will recognize that the above-described optimization may be implemented in any number of hardware and/or software components and in various configurations. 
     The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,  FIGS. 13A-13E  illustrate five different embodiments of the movable reflective layer  14  and it&#39;s supporting structures.  FIG. 13A  is a cross section of the embodiment of  FIG. 1 , where a strip of metal material  14  is deposited on orthogonally extending supports  18 . In  FIG. 13B , the moveable reflective layer  14  is attached to supports at the corners only, on tethers  32 . In  FIG. 13C , the moveable reflective layer  14  is suspended from a deformable layer  34 , which may comprise a flexible metal. The deformable layer  34  connects, directly or indirectly, to the substrate  20  around the perimeter of the deformable layer  34 . These connections are herein referred to as support posts. The embodiment illustrated in  FIG. 13D  has support post plugs  42  upon which the deformable layer  34  rests. The movable reflective layer  14  remains suspended over the gap, as in  FIGS. 13A-13C , but the deformable layer  34  does not form the support posts by filling holes between the deformable layer  34  and the optical stack  16 . Rather, the support posts are formed of a planarization material, which is used to form support post plugs  42 . The embodiment illustrated in  FIG. 13E  is based on the embodiment shown in  FIG. 13D , but may also be adapted to work with any of the embodiments illustrated in  FIGS. 13A-13C  as well as additional embodiments not shown. In the embodiment shown in  FIG. 13E , an extra layer of metal or other conductive material has been used to form a bus structure  44 . This allows signal routing along the back of the interferometric modulators, eliminating a number of electrodes that may otherwise have had to be formed on the substrate  20 . 
     In embodiments such as those shown in FIG.  13 A- 13 E 7 , the interferometric modulators function as direct-view devices, in which images are viewed from the front side of the transparent substrate  20 , the side opposite to that upon which the modulator is arranged. In these embodiments, the reflective layer  14  optically shields the portions of the interferometric modulator on the side of the reflective layer opposite the substrate  20 , including the deformable layer  34 . This allows the shielded areas to be configured and operated upon without negatively affecting the image quality. Such shielding allows the bus structure  44  in  FIG. 13E , which provides the ability to separate the optical properties of the modulator from the electromechanical properties of the modulator, such as addressing and the movements that result from that addressing. This separable modulator architecture allows the structural design and materials used for the electromechanical aspects and the optical aspects of the modulator to be selected and to function independently of each other. Moreover, the embodiments shown in  FIGS. 13C-13E  have additional benefits deriving from the decoupling of the optical properties of the reflective layer  14  from its mechanical properties, which are carried out by the deformable layer  34 . This allows the structural design and materials used for the reflective layer  14  to be optimized with respect to the optical properties, and the structural design and materials used for the deformable layer  34  to be optimized with respect to desired mechanical properties. 
     Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.

Technology Classification (CPC): 6