Patent Publication Number: US-2011069371-A1

Title: Semi-transparent/transflective lighted interferometric devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/207,270, filed Sep. 9, 2008, which claims the benefit of U.S. Provisional Application No. 60/994,073, filed Sep. 17, 2007, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The field of the disclosure relates generally to ornamental and image displaying devices utilizing interferometry. 
     2. Description of the Related Art 
     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. 
     SUMMARY 
     In certain embodiments, a device is provided which includes a substrate that is at least partially optically transparent. The device of certain embodiments also includes a first layer over the substrate, wherein the first layer is partially optically absorptive, partially optically reflective, and partially optically transmissive, and a second layer over the substrate and spaced from the first layer, the first layer located between the substrate and the second layer, wherein the second layer is partially optically absorptive, partially optically reflective, and partially optically transmissive. The device of certain embodiments also includes a light source responsive to a signal and positioned relative to the substrate such that the first layer and the second layer are located between the substrate and the light source. Light emitted from the device in a first direction comprises a first portion of light incident on the substrate, transmitted through the substrate, transmitted through the first layer, reflected by the second layer, transmitted through the first layer, transmitted through the substrate, and emitted from the substrate in the first direction. The light emitted in the first direction can also include a second portion of light incident on the substrate, transmitted through the substrate, reflected by the first layer, transmitted through the substrate, and emitted from the substrate in the first direction. In certain embodiments, the light emitted in the first direction also includes a third portion of light from the light source incident on the second layer, transmitted through the second layer, transmitted through the first layer, transmitted through the substrate, and emitted from the substrate in the first direction. 
     In certain embodiments a device is provided comprising a first means for partially absorbing light, partially reflecting light, and partially transmitting light and a second means for partially absorbing light, partially reflecting light, and partially transmitting light, the second means spaced from the first means. The device of some embodiments also includes a means for generating light, wherein light emitted from the device in a first direction comprises a first portion of light incident on the first means, transmitted through the first means, reflected by the second means, transmitted through the first means, and emitted from the device in the first direction. The light emitted from the device in the first direction can also include a second portion of light incident on the first means, reflected by the first means, and emitted from the device in the first direction, and a third portion of light generated by the light generation means, incident on the second means, transmitted through the second means, transmitted through the first means, and emitted from the device in the first direction. 
     In certain embodiments, a method of displaying an image is provided. The method of certain embodiments includes providing a device comprising a substrate that is at least partially optically transparent. The device can also include a first layer over the substrate, wherein the first layer is partially optically absorptive, partially optically transmissive, and partially optically reflective, and a second layer over the substrate and spaced from the first layer, the first layer located between the substrate and the second layer, wherein the second layer is partially optically absorptive, partially optically transmissive, and partially optically reflective. In certain embodiments, the method includes positioning a light source responsive to a signal relative to the substrate such that the first layer and the second layer are located between the substrate and the light source, and emitting light from the device in a first direction. In certain embodiments, the emitted light comprises a first portion of light incident on the substrate, transmitted through the substrate, transmitted through the first layer, reflected by the second layer, transmitted through the first layer, transmitted through the substrate, and emitted from the device in the first direction. The emitted light can also include a second portion of light incident on the substrate, transmitted through the substrate, reflected by the first layer, transmitted through the substrate, and emitted from the device in the first direction. In certain embodiments, the emitted light includes a third portion of light from the light source incident on the second layer, transmitted through the second layer, transmitted through the first layer, transmitted through the substrate, and emitted from the device in the first direction. 
    
    
     
       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. 2  is a system block diagram illustrating one embodiment of an electronic device incorporating a 3×3 interferometric modulator display. 
         FIG. 3  is a diagram of movable mirror position versus applied voltage for one exemplary embodiment of an interferometric modulator of  FIG. 1 . 
         FIG. 4  is an illustration of a set of row and column voltages that may be used to drive an interferometric modulator display. 
         FIG. 5A  illustrates one exemplary frame of display data in the 3×3 interferometric modulator display of  FIG. 2 . 
         FIG. 5B  illustrates one exemplary timing diagram for row and column signals that may be used to write the frame of  FIG. 5A . 
         FIGS. 6A and 6B  are system block diagrams illustrating an embodiment of a visual display device comprising a plurality of interferometric modulators. 
         FIG. 7A  is a cross section of the device of  FIG. 1 . 
         FIG. 7B  is a cross section of an alternative embodiment of an interferometric modulator. 
         FIG. 7C  is a cross section of another alternative embodiment of an interferometric modulator. 
         FIG. 7D  is a cross section of yet another alternative embodiment of an interferometric modulator. 
         FIG. 7E  is a cross section of an additional alternative embodiment of an interferometric modulator. 
         FIG. 8  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 9A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 9B  shows the reflectivity of an example device in accordance with certain embodiments described herein. 
         FIGS. 9C-9D  show CIE chromaticity diagrams of an example device in accordance with certain embodiments described herein. 
         FIG. 9E  shows a CIE chromaticity diagram of two example devices in accordance with certain embodiments described herein. 
         FIG. 9F  shows the reflectivity of two example devices in accordance with certain embodiments described herein. 
         FIG. 9G  shows a CIE chromaticity diagram of two example devices in accordance with certain embodiments described herein. 
         FIG. 9H  shows the reflectivity of two example devices in accordance with certain embodiments described herein. 
         FIG. 10  shows the reflectivity of an example device in accordance with certain embodiments described herein. 
         FIG. 11A  shows the reflectivity and transmittance of an example device in accordance with certain embodiments described herein. 
         FIG. 11B  shows a CIE chromaticity diagram of an example device in accordance with certain embodiments described herein. 
         FIG. 12A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 12B  shows a CIE chromaticity diagram of an example device for different viewing angles in accordance with certain embodiments described herein. 
         FIG. 13  shows a CIE chromaticity diagram of an example device for different viewing angles in accordance with certain embodiments described herein. 
         FIG. 14A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIGS. 14B-14C  show CIE chromaticity diagrams of two example devices in accordance with certain embodiments described herein. 
         FIG. 15  schematically illustrates an example device comprising a fluorescent material in accordance with certain embodiments described herein. 
         FIG. 16  schematically illustrates an example device comprising a third layer in accordance with certain embodiments described herein. 
         FIG. 17  schematically illustrates another example device comprising a third layer in accordance with certain embodiments described herein. 
         FIG. 18A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 18B  shows the reflectivity of an example device in accordance with certain embodiments described herein. 
         FIG. 18C  shows a CIE chromaticity diagram of an example device in accordance with certain embodiments described herein. 
         FIG. 19  schematically illustrates an example device comprising a passivation layer in accordance with certain embodiments described herein. 
         FIG. 20A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 20B  shows a CIE chromaticity diagram of example devices in accordance with certain embodiments described herein. 
         FIG. 21  schematically illustrates an example device comprising a first glass layer and a second glass layer in accordance with certain embodiments described herein. 
         FIG. 22  schematically illustrates an example device having a first layer, a second layer, a third layer, and a fourth layer in accordance with certain embodiments described herein. 
         FIG. 23  shows the transmittance of an example device in accordance with certain embodiments described herein. 
         FIG. 24A  schematically illustrates an example device in accordance with certain embodiments described herein. 
         FIG. 24B  shows the reflectivity of example devices in accordance with certain embodiments described herein. 
         FIG. 24C  shows a CIE chromaticity diagram of example devices in accordance with certain embodiments described herein. 
         FIG. 24D  shows the transmittance of example devices in accordance with certain embodiments described herein. 
         FIG. 24E  shows the reflectivity and transmittance of example devices in accordance with certain embodiments described herein. 
         FIG. 24F  shows a CIE chromaticity diagram of example devices in accordance with certain embodiments described herein. 
         FIGS. 25A-D  show CIE chromaticity diagrams of example devices for different viewing angles in accordance with certain embodiments described herein. 
         FIG. 26  shows a CIE chromaticity diagram of example devices in accordance with certain embodiments described herein. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following detailed description is directed to certain specific embodiments. However, the teachings herein 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. Embodiments described herein may be used in decorative and architectural applications such as, for example, for decorative glass. Moreover, and 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, decorative glass, 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. 
     In certain embodiments, a display device is provided that utilizes both interferometrically reflected light and transmitted light. Light incident on the display device is interferometrically reflected from a plurality of layers of the display device to emit light in a first direction, the interferometrically reflected light having a first color. Light from a light source is transmitted through the plurality of layers of the display device to emit from the display device in the first direction, the transmitted light having a second color. 
     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 (e.g., visible 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 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  16  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   a ,  14   b , and these strips may form column electrodes in a display device. In other embodiments, layers  14   a ,  14   b  can be semi-transparent such that the device is capable of partially reflecting and partially transmitting visible light or other non visible wavelengths while retaining the interferometric properties described herein. In one embodiment, layers  14   a ,  14   b  can comprise transparent material which can provide mechanical stability. In certain embodiments, the layers  14   a ,  14   b  comprise another layer of a partially reflective material, such as Aluminum. In one embodiment, the transparent mechanical layer comprises a dielectric material, such as Silicon Oxynitride, Silicon Dioxide or Silicon Nitride. In certain embodiments, the transparent mechanical layer is approximately 1000 to 5000 Angstroms thick and the partially reflective layer comprises a highly conductive material, such as Aluminum, of approximately 30 to 300 Angstroms thickness. In other embodiments, the layers  14   a ,  14   b  are patterned into areas of varying transmission and reflectivity. In one embodiment, the variable transmission and reflectivity is achieved by varying the thickness of the reflective material. For example, increasing the thickness can create areas of increased reflectivity and decreased transmission. 
     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. 
       FIGS. 2 through 5B  illustrate one exemplary process and system for using an array of interferometric modulators in a display application. 
       FIG. 2  is a system block diagram illustrating one embodiment of an electronic device that may incorporate certain aspects described herein. 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. 2 . For MEMS interferometric modulators, the row/column actuation protocol may take advantage of a hysteresis property of these devices illustrated in  FIG. 3 . 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. 3 , the movable layer does not relax completely until the voltage drops below 2 volts. Thus, there exists a window of applied voltage, about 3 to 7 V in the example illustrated in  FIG. 3 , 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. 3 , 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 certain embodiments described herein. 
       FIGS. 4 ,  5 A, and  5 B illustrate one possible actuation protocol for creating a display frame on the 3×3 array of  FIG. 2 .  FIG. 4  illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves of  FIG. 3 . In the  FIG. 4  embodiment, actuating a pixel involves setting the appropriate column to −V 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. 4 , 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. 5B  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. 5A , where actuated pixels are non-reflective. Prior to writing the frame illustrated in  FIG. 5A , the pixels can be in any state, and in this example, all the rows are at 0 volts, and all the columns are at +5 volts. With these applied voltages, all pixels are stable in their existing actuated or relaxed states. 
     In the  FIG. 5A  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. 5A . After writing the frame, the row potentials are zero, and the column potentials can remain at either +5 or −5 volts, and the display is then stable in the arrangement of  FIG. 5A . It will be appreciated that the same procedure can be 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. 6A and 6B  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  45 , 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. 6B . 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 or 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, or 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 embodiments, control programmability resides, as described above, in a driver controller which can be located in several places in the electronic display system. In some embodiments, control programmability resides in the array driver  22 . Those of skill in the art will recognize that the above-described optimizations 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. 7A-7E  illustrate five different embodiments of the movable reflective layer  14  and its supporting structures.  FIG. 7A  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. 7B , the moveable reflective layer  14  is attached to supports at the corners only, on tethers  32 . In  FIG. 7C , 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. 7D  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. 7A-7C , 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. 7E  is based on the embodiment shown in  FIG. 7D , but may also be adapted to work with any of the embodiments illustrated in  FIGS. 7A-7C , as well as additional embodiments not shown. In the embodiment shown in  FIG. 7E , 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. 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. 7E , 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. 7C-7E  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. 
     As discussed, embodiments described herein may be used in ornamental and architectural devices and applications, such as for decorative glass. For example, in an architectural setting, a coated glass panel may provide an attractive decorative effect such that the glass appears to be one color from one side and a different color from the other side. Moreover, when a light source positioned on one side of the panel is turned on, the panel may appear to be another color. Certain other embodiments are used for display devices. 
       FIG. 8  schematically illustrates an example device  100  in accordance with certain embodiments described herein. The device  100  comprises a substrate  110 , a first layer  120 , a second layer  130 , and a light source  140 . The substrate  110  is at least partially optically transparent. The first layer  120  is positioned over the substrate  110 , and the first layer  120  is partially optically absorptive, partially optically reflective, and partially optically transmissive. The second layer  130  is positioned over the substrate  110  and is spaced from the first layer  120  with the first layer  120  located between the substrate  110  and the second layer  130 . The second layer  130  is partially optically absorptive, partially optically reflective, and partially optically transmissive. In certain embodiments, the light source  140  is responsive to a signal and positioned relative to the substrate  110  such that the first layer  120  and the second layer  130  are located between the substrate  110  and the light source  140 . 
     In certain embodiments, light emitted from the device  100  in a first direction  313  toward a viewer comprises a first portion  300  of light, a second portion  301  of light, and a third portion  302  of light. The first portion  300  of light is incident on the substrate  110 , transmitted through the substrate  110 , transmitted through the first layer  120 , reflected by the second layer  130 , transmitted through the first layer  120 , transmitted through the substrate  110 , and emitted from the substrate  110  in the first direction  313 . The second portion  301  of light is incident on the substrate  110 , transmitted through the substrate  110 , reflected by the first layer  120 , transmitted through the substrate  110 , and emitted from the substrate  110  in the first direction  313 . The third portion  302  of light is from the light source  140  and is incident on the second layer  130 , transmitted through the second layer  130 , transmitted through the first layer  120 , transmitted through the substrate  110 , and emitted from the substrate  110  in the first direction  313 . In certain embodiments, at least the first portion  300  and the second portion  301  combine interferometrically to form the light emitted from the device  100  in the first direction  313 . Similarly, in certain embodiments, the third portion  302  of light comprises interferometrically combined portions of light transmitted or reflected from the various layers of the device  100 . Not included in this description is any stray light reflected from the surface of the substrate  110 . Such stray light may be reduced by anti-reflection coatings which can be included on the substrate  110  in certain embodiments. 
     In certain embodiments, the substrate  110  comprises a glass or plastic material. In certain embodiments, the first layer  120  and the second layer  130  may comprise various materials with a positive extinction coefficient such as aluminum, chromium, molybdenum, titanium, carbon, silver, gold, and other such materials. In certain embodiments, for example, the first layer  120  comprises chromium. In certain embodiments, the second layer  130  comprises a metal layer (e.g., aluminum layer having a thickness of less than 300 Angstroms). In one embodiment, the second layer  130  comprises a metal having a thickness in the range of 30 to 300 Angstroms. In certain embodiments, the first layer has a thickness in the range of about 50 to 300 Angstroms. In one embodiment, for example, the first layer comprises chromium and the second layer comprises aluminum. The transmissivity of the second layer  130  in certain embodiments is dependent on the thickness of the second layer  130 . 
     In certain embodiments, the first layer  120  is substantially optically absorptive. In other embodiments, the first layer  120  is substantially optically reflective. In yet other embodiments, the first layer  120  is substantially optically transmissive. In certain embodiments, the second layer  130  is substantially optically absorptive. In other embodiments, the second layer  130  is substantially optically reflective. In yet other embodiments, the second layer  130  is substantially optically transmissive. In one embodiment, for example, substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52, the layer  120  comprises Chromium of 70 Angstroms thickness, and the layer  130  comprises Aluminum of 100 Angstroms thickness. In the example embodiment, the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3400 Angstroms thickness to create an interferometric cavity capable of modifying the properties of light reflecting from or transmitted through the device by the process of optical interference ( FIG. 9A ). When illuminated from direction  300  the device of the example embodiment, the device  100  primarily reflects green light in the visible spectrum in direction  313  with a peak reflectivity of approximately 72% at a wavelength of approximately 530 nm measured normal to the device ( FIG. 9B ). This corresponds to a color point of x=0.26, y=0.47 in the standard CIE xyY color space as shown by the CIE Chromaticity diagram of  FIG. 9C . When illuminated from direction  300  the example device transmits light in direction  314  having a transmission spectrum also peaking at a wavelength of approximately 530 nm, corresponding to a green color in the visible spectrum ( FIG. 9D ). In this embodiment, if the thickness of layer  130  is altered, the reflectivity and transmission may be altered. For example if the thickness of layer  130  is reduced to from 100 Angstroms to 70 Angstroms, peak reflectivity will be reduced to approximately 62%, while the peak reflectivity wavelength will be unchanged at approximately 530 nm, corresponding to a color point of x=0.28, y=0.47 in the standard CIE xyY color space when viewed normal to the device in direction  313  ( FIGS. 9E-9F ). In  FIGS. 9E-9F , the labels “100A” and “70A” refer to the plots characterizing the embodiments described above having a layer  130  with a thickness of 100 Angstroms and 70 Angstroms, respectively. In another embodiment, substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52, layer  120  comprises Chromium of 20 Angstroms thickness, and layer  130  comprises Aluminum of 100 Angstroms thickness. The peak reflectivity of the device of this embodiment is approximately 71%, and peak reflectivity wavelength is approximately 530 nm in the visible spectrum, normal to the device, corresponding to a color point of x=0.29, y=0.40 in the standard CIE xyY color space ( FIGS. 9G-9H ). In this embodiment, layer  120  is primarily responsible for the saturation of the color reflected in direction  313 , as shown by comparison to the embodiment described in which substrate  110  comprises glass of approximately 10 mm thickness, layer  120  comprises Chromium of 70 Angstroms thickness and layer  130  comprises Aluminum of 100 Angstroms thickness. In  FIGS. 9G-9H , the labels “70A” and “20A” refer to the plots characterizing the embodiments described above having a layer  120  with a thickness of 70 Angstroms and 20 Angstroms, respectively. The embodiments described above will also exhibit angular color shift. As used herein, the term “color shift” refers to the change of color emitted from a side of the device  100  as a function of angle from a direction perpendicular to the first layer  120  and the second layer  130 . For example, the color of light emitted from the device  100  and received by a viewer can be dependent on the angular position of the viewer relative to the device  100 . 
     In certain embodiments, the first portion  300  of light incident on the substrate  110  and the second portion  301  of light incident on the substrate  110  are infrared, visible, and/or ultraviolet light. In certain embodiments, the third portion  302  of light from the light source  140  is infrared, visible, and/or ultraviolet light. In one embodiment, substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52. In this embodiment, the layer  120  comprises Chromium of 70 Angstroms thickness, the layer  130  comprises Aluminum of 100 Angstroms thickness, and the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 5000 Angstroms thickness, to create an interferometric cavity. When illuminated from direction  300  the device of the example embodiment primarily reflects light in both the infra red spectrum and the visible spectrum in direction  313  with a peak reflectivity of approximately 68% at wavelengths of approximately 755 nm and 72% at a wavelength of 510 nm measured normal to the device ( FIG. 10 ). 
     In certain embodiments, the light source  140  comprises a backlight, as schematically illustrated by  FIG. 8 . The backlight of certain such embodiments comprises a light guide slab that receives light from a light generator (e.g., an LED, where light from the LED is injected along an edge of the light guide slab), guides the light along the light guide slab, and redirects and emits the light towards the device thereby providing illumination that may be substantially uniform or non-uniform to take advantage of device transmission and reflection properties to create patterns, graphics, or images with luminance or chromatic contrast when viewed from direction  313  or  314 . The light guide slab can include extractor features located on a rear or front surface (with respect to the second layer  130 ) of the light guide slab which disrupt the propagation of light within the light guide slab and cause the light to be uniformly emitted across a front surface of the light guide slab towards a front surface of the device  100 . In certain embodiments, the light source  140  comprises a fluorescent light generator. In other embodiments, the light source  140  comprises an incandescent light generator, an LED, or another type of light generator. In certain other embodiments, the light source  140  can comprise a substantially reflective surface which reflects or emits a substantial portion of the light which reaches the light source  140  after being transmitted through the substrate  110 , the first layer  120 , and the second layer  130 . In certain embodiments, there may be a separation between the light source  140  and the other portions of the device  100 . In certain such embodiments, for example, there may be a physical separation between the light source  140  and the layer  130 . Additionally, in some embodiments, the light incident upon and modulated by the device  100  includes ambient or natural light, such as light from the sun, for example. 
     In certain embodiments, the light source  140  is responsive to the signal (e.g., from a controller) by changing between multiple states. For example, in certain embodiments, in response to the signal, the light source  140  can turn “on” and “off”. In other embodiments, the light source  140  may be responsive to the signal by changing to emit light having different properties, such as, for example, light having different brightness levels or different colors. In one embodiment, the light source  140  is responsive to the signal by changing from emitting light having a first selected brightness to emitting light having a second selected brightness different from the first selected brightness. In certain embodiments, the light source  140  is responsive to the signal by changing from emitting light having a first selected color to emitting light having a second selected color different from the first selected color. In certain embodiments, the light source  140  is responsive to the signal by changing from emitting light of a first selected color, thereby modulating angular color shift and intensity over a predetermined range of angles (e.g., 0 to 30 degrees) from a direction perpendicular to the first layer  120  and the second layer  130  to emitting light exhibiting a second selected color, thereby modulating angular color shift and intensity over a predetermined range of angles (e.g., 0 to 30 degrees) from a direction perpendicular to the first layer  120  and the second layer  130  where the second selected color shift is different from the first selected angular color shift and intensity. By modulating the signal in certain embodiments, one or more properties of the light emitted in the first direction  313  can be modulated. 
     Light resulting from the interference of light reflected from a plurality of layers can be referred to as “interferometrically reflected” light. In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere with one another to produce interferometrically reflected light which comprises a substantial portion of the light reflected from the device  100 . In certain other embodiments, the reflected light emitted from the device  100  can comprise light from other reflections from other interfaces (e.g., the air-substrate interface), light reflected from other layers, and light from multiple reflections between these interfaces (e.g., light reflected multiple times between the first layer  120  and the second layer  130 ). 
     In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere to produce light having a first color, and the third portion  302  of light has a second color different from the first color. In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere to produce light having a first color, and the light emitted from the device  100  in the first direction  313  (e.g., the combination of the interferometrically reflected light and the third portion  302  of light) has a second color different from the first color. 
     In certain embodiments, the light emitted from the device  100  in the first direction  313  has a first color when the light source  140  emits light. The first color of such embodiments results from the combination of the interferometrically reflected light and the third portion  302  of light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a second color, which can be different from the first color, when the light source  140  does not emit light. The second color of such embodiments results from the interferometrically reflected light without the third portion  302  of light. 
     In certain embodiments, the light emitted by the device  100  in the first direction  313  has a first color when the light source  140  emits light and ambient light is incident on the device  100  (e.g., incident on the substrate  110 ). The first color of such embodiments results from the combination of the interferometrically reflected light and the third portion  302  of light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a second color, which can be different from the first color, when the light source  140  emits light and ambient light is not incident on the device  100 . The second color of such embodiments results from the third portion  302  of light without the interferometrically reflected light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a third color, which can be different from either the first color or the second color, when the light source  140  does not emit light and ambient light is incident on the device  100 . The third color of such embodiments results from the interferometrically reflected light without the third portion  302  of light. In one embodiment, substrate  110  comprises glass of approximately 10 mm thickness, layer  120  comprises Aluminum of 40 Angstroms thickness, layer  130  comprises Aluminum also of 40 Angstroms thickness, and layer  120  and  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3200 Angstroms thickness to create an interferometric cavity. When illuminated from direction  300  the device will reflect blue light in direction  313 , normal to the device, with a peak wavelength of 470 nm and peak reflectivity of approximately 56% (not including losses through substrate materials or due to reflection at material/air interfaces). The example interferometric device described is semi-transparent and will transmit light in direction  302  when illuminated by light source  140 . This embodiment will transmit green light with a peak wavelength of 540 nm and a transmission of approximately 45% (not including losses through substrate materials, or due to reflection at material/air interfaces), as shown by the plot of  FIG. 11A  and the CIE chromaticity diagram of  FIG. 11B . The light emitted in direction  313  will comprise a combination of the interferometrically reflected light and light  302 , which will vary in perceived color according to the intensity of the light source  140  and the intensity of the light incident on the device. 
     In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere to produce light having a first color and which exhibits a first angular color shift, and the third portion  302  of light has a second color and exhibits a second angular color shift different from the first angular color shift. In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere to produce light having a first color which exhibits a first angular color shift, and the light emitted from the device  100  in the first direction  313  (e.g., the combination of the interferometrically reflected light and the third portion  302  of light) has a second color and exhibits a second angular color shift different from the first angular color shift. In one embodiment, substrate  110  comprises glass of approximately 10 mm thickness, layer  120  comprises Aluminum of 40 Angstroms thickness, layer  130  comprises Aluminum also of 40 Angstroms thickness, and layer  120  and layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3200 Angstroms thickness to create an interferometric cavity. When illuminated from direction  300  the device will reflect blue light in direction  313 , normal to the device, with a peak wavelength of 470 nm and peak reflectivity of approximately 56% (not including losses through substrate materials, or due to reflection at material/air interfaces). The interferometric device of the example embodiment is semi-transparent and will transmit light in direction  302  when illuminated by light source  140 . This embodiment will transmit green light with a peak wavelength of 540 nm and a transmission of approximately 45% (not including losses through substrate materials, or due to reflection at material/air interfaces), as shown by  FIG. 11A .  FIG. 11B  shows the same as a CIE chromaticity diagram.  FIGS. 12A and 12B  show how the reflected and transmitted color varies with view angle.  FIG. 12B  assumes that the viewer is within the substrate  110  and does not account for the substrate to air interface. A refractive index change at that interface will alter the perceived color shift. As a result, if the viewer is in air (N=1) and the substrate is glass (N=1.52), then the viewer will see a reduced amount of color shift for a given view angle with respect to the substrate. 
     In certain embodiments, the light emitted from the device  100  in the first direction  313  has a first color and exhibits a first angular color shift when the light source  140  emits light. The first angular color shift of such embodiments results from the combination of the interferometrically reflected light and the third portion  302  of light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a second color and exhibits a second angular color shift, which can be different from the first angular color shift, when the light source  140  does not emit light. The second angular color shift of such embodiments results from the interferometrically reflected light without the third portion  302  of light. 
     In certain embodiments, the light emitted by the device  100  in the first direction  313  has a first color and exhibits a first angular color shift when the light source  140  emits light and ambient light is incident on the device  100  (e.g., incident on the substrate  110 ). The first angular color shift of such embodiments results from the combination of the interferometrically reflected light and the third portion  302  of light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a second color and exhibits a second angular color shift, which can be different from the first angular color shift, when the light source  140  emits light and ambient light is not incident on the device  100 . The second angular color shift of such embodiments results from the third portion  302  of light without the interferometrically reflected light. In certain embodiments, the light emitted by the device  100  in the first direction  313  has a first color and exhibits a third angular color shift, which can be different from either the first angular color shift or the second angular color shift, when the light source  140  does not emit light and ambient light is incident on the device  100 . The third angular color shift of such embodiments results from the interferometrically reflected light without the third portion  302  of light. Referring again to the example embodiment described above with respect to  FIGS. 12A-12B  in which the substrate  110  comprises glass of approximately 10 mm thickness, layer  120  comprises Aluminum of 40 Angstroms thickness, layer  130  comprises Aluminum also of 40 Angstroms thickness, and layer  120  and layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3200 Angstroms thickness, a viewer will see 313 as the combination of the reflected light ( 300 ,  301 ) and transmitted light  302 .  FIG. 13  shows how the reflected and transmitted color variation with view angle (for a viewer within substrate  110 , so ignoring additional reflections from substrate  110 .) For a viewer normal to the IMOD, depending on the brightness of the light source  140  and the reflected portion of light, the perceived color will lie on a line from A to B as shown in  FIG. 13 . Similarly at an angle of 30 degrees, the color will lie on a line from C to D. This example also shows how an illuminated semi-transparent IMOD can be used to produce color that not only varies with view angle, but which is not a color that can be directly created by a purely reflective IMOD. 
     In certain embodiments, the device  100  is viewable from both the first direction  313  and in a second direction  314  generally opposite to the first direction  313 . For example, the device  100  of certain such embodiments can be viewed from a first position on a first side of the device  100  and from a second position on a second side of the device  100 . In certain embodiments, the light emitted from the device  100  in the second direction  314  comprises a fourth portion  306  of light, a fifth portion  307  of light, and a sixth portion  312  of light. The fourth portion  306  of light in certain embodiments is incident on the substrate  110 , transmitted through the substrate  110 , transmitted through the first layer  120 , transmitted through the second layer  130 , and emitted from the device  100  in the second direction  314 . The fifth portion  307  of light in certain embodiments is incident on the second layer  130 , transmitted through the second layer  130 , reflected from the first layer  120 , transmitted through the second layer  130 , and emitted from the device  100  in the second direction  314 . The sixth portion  312  of light in certain embodiments is incident on the second layer  130 , reflected from the second layer  130 , and emitted from the device  100  in the second direction  314 . In certain embodiments, the fifth portion  307  of light comprises light emitted by the light source  140  and the sixth portion  312  of light comprises light emitted by the light source  140 . 
     In certain embodiments, the light emitted from the device  100  in the first direction  313  has a first color, and the light emitted from the device  100  in the second direction  314  has a second color. In certain such embodiments, the first color and the second color are substantially the same, while in certain other such embodiments, the first color and the second color are different. In certain embodiments, the light emitted from the device  100  in the first direction  313  has a first color and exhibits a first angular color shift, and the light emitted from the device  100  in the second direction  314  has a second color and exhibits a second angular color shift. In certain such embodiments, the first angular color shift and the second angular color shift are substantially the same, while in certain other such embodiments, the first angular color shift and the second angular color shift are different. In one embodiment, substrate  110  comprises glass of approximately 10 mm thickness, layer  120  comprises Aluminum of 40 Angstroms thickness, layer  130  comprises Aluminum also of 40 Angstroms thickness, and layer  120  and layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3200 Angstroms thickness to create an interferometric cavity. This symmetrically designed IMOD will tend to exhibit similar reflected colors in direction  313  and  314  ( FIGS. 14A-14B ). In this example embodiment, layer  120  is positioned against glass and layer  130  is positioned in air (for simplicity, and not by way of limitation, there is no backlight  140  included in this example embodiment). The CIE Chromaticity diagram of  FIG. 14B  shows that the reflected colors in direction  313  and  314  are similar. In practice, the difference in refractive index between substrate  110  and the air surrounding layer  130  accounts for the slight difference in symmetry. If layer  130  were also positioned against glass, the device reflection would be symmetric. For simplicity, the viewer is assumed to be normal to the device and on side  313  the viewer is assumed to be within substrate  110 , so that the substrate  110  to air interface is not included. The transmitted color is substantially the same for ray  306  and  302  in the example embodiment. In another embodiment, the substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52. Layer  120  comprises Chromium of 70 Angstroms thickness, layer  130  comprises Aluminum of 100 Angstroms thickness, and layer  120  and layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 3400 Angstroms thickness. In this example, the layer  120  is positioned against glass and the layer  130  is positioned in air (for simplicity, and not by way of limitation, no backlight  140  is included in this example embodiment). The CIE Chromaticity diagram of  FIG. 14C  shows that the reflected colors in direction  313  and direction  314  are different. For simplicity, the viewer is assumed to be normal to the device and on side  313  the viewer is assumed to be within substrate  110 , so the substrate  110  to air interface is not included. The transmitted color is substantially the same for ray  306  and  302  in the example embodiment. 
     In certain embodiments, the device  100  comprises a region  150  located between the first layer  120  and the second layer  130 . The region  150  of certain embodiments comprises a dielectric layer and is at least partially optically transparent. In certain embodiments, at least a portion of the region  150  is filled with air. In certain such embodiments, at least one of the first layer  120  and the second layer  130  is selectively movable so as to change a spacing between the first layer  120  and the second layer  130 . Thus, in certain embodiments, the first layer  120  and the second layer  130  form an actuable interferometric modulator as described herein. In certain embodiments, the device  100  is an actuatable element (e.g., a pixel or sub-pixel) of a display system. By selectively moving at least one of the first layer  120  and the second layer  130  so as to change a spacing between the first layer  120  and the second layer  130 , in certain embodiments, one or more properties of the light emitted in the first direction  313  can be modulated. 
     In certain embodiments, the at least one of the first layer  120  and the second layer  130  which is selectively movable comprises a support structure which mechanically strengthens the layer. In some embodiments, the support structure comprises a transparent material. In other embodiments, the support structure comprises a non-transparent material (e.g., a metal ring) which is positioned so as to not affect the optical properties of the device. 
       FIG. 15  schematically illustrates an example device  100  comprising a fluorescent material  160  in accordance with certain embodiments described herein. The device  100  comprises a substrate  110 , a first layer  120 , and a second layer  130 . The substrate is at least partially optically transparent. The first layer  120  is positioned over the substrate  110 , and the first layer  120  is partially optically absorptive, partially optically reflective, and partially optically transmissive. The second layer  130  is positioned over the substrate  110  and is spaced from the first layer  120  with the first layer  120  located between the substrate  110  and the second layer  130 . The second layer  130  is partially optically absorptive, partially optically reflective, and partially optically transmissive. The fluorescent material  160  is positioned relative to the substrate  110  such that the first layer  120  and at least a portion of the second layer  130  are located between the substrate  110  and the fluorescent material  160 . In certain embodiments, the fluorescent material  160  is responsive to ultraviolet light incident on the substrate  110 , transmitted through the substrate  110 , transmitted through the first layer  130 , and transmitted through the at least a portion of the second layer  130  by generating visible light. At least a portion of the visible light from the fluorescent material  160  in certain embodiments is transmitted through the second layer  130 , the first layer  120 , and the substrate  110  to contribute to the light emitted in the first direction  313 . In certain such embodiments, the fluorescent material  160  serves as the light source  140 . 
       FIG. 16  schematically illustrates an example device  100  comprising a third layer  170  in accordance with certain embodiments described herein. In certain embodiments, the third layer  170  may comprise various materials such as aluminum, chromium, molybdenum, titanium, carbon, silver, gold, and other materials. The third layer  170  is over the substrate  110  and spaced from the first layer  120  and from the second layer  130 . The third layer  170  is partially optically absorptive, partially optically reflective, and partially optically transmissive. In certain embodiments, the third layer  170  has a thickness in a range from between 20 and 300 Angstroms thick. In certain embodiments, the third layer  170  comprises chromium. In certain embodiments, the third layer  170  is substantially optically absorptive. In other embodiments, the third layer  170  is substantially optically reflective. In yet other embodiments, the third layer  170  is substantially optically transmissive. 
     As shown schematically by  FIG. 16 , in certain embodiments, the third layer  170  is located between the first layer  120  and the second layer  130 . The device  100  of certain embodiments further comprises a region  150  (e.g., an at least partially optically transparent dielectric layer or a region filled with air) located between the third layer  170  and the first layer  120 , and a region  190  (e.g., an at least partially optically transparent dielectric layer or a region filled with air) located between the third layer  170  and the second layer  130 . 
       FIG. 17  schematically illustrates another example device  100  comprising a third layer  170  in accordance with certain embodiments described herein. The third layer  170  is positioned such that the second layer  130  is located between the first layer  120  and the third layer  170 . The device  100  of certain embodiments further comprises a region  150  (e.g., an at least partially optically transparent dielectric layer or a region filled with air) located between the first layer  120  and the second layer  130 , and a region  190  (e.g., an at least partially optically transparent dielectric layer or a region filled with air) located between the second layer  130  and the third layer  170 . 
     The combination of the layers  120 ,  150 ,  130 ,  170 ,  190  can comprise a dual cavity interferometric modulator in certain embodiments. The additional layers  170 ,  190  of material as compared to  FIG. 8  can provide flexibility in design such that the modulator can be designed to reflect or transmit additional colors. In certain embodiments, the layers  150 ,  190  can be described as spacer layers and layers  120 ,  170  can be described absorber layers. In other embodiments, the layer  170  may be an absorber layer and layers  120 ,  130  may act as partial reflector layers. In some embodiments, the layers  150 ,  190  have equal thicknesses. In other embodiments, the layers  150 ,  190  have different thicknesses. In one embodiment, substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52, the layers  120 ,  170  comprise Chromium of 70 Angstroms thickness, layer  130  comprises Aluminum of 100 Angstroms thickness, and spacing dielectric layers  150 ,  190  comprise Silicon Dioxide of 3400 Angstroms thickness ( FIG. 18A ).  FIGS. 18B-18C  show the reflected color normal to the substrate in direction  313  (assuming no backlight). Comparing this example to  FIGS. 9B and 9C  for a viewer standing in air, and including a front surface reflection from substrate  110 , the peak wavelength is almost unchanged at 520 nm, but shows a sharper peak and correspondingly more saturated color as shown by the CIE chromaticity diagram of  FIG. 9C , for example. 
       FIG. 19  schematically illustrates an example device  100  comprising a passivation layer  200  in accordance with certain embodiments described herein. The passivation layer  200  is positioned such that the second layer  130  is located between the passivation layer  200  and the substrate  110 . In certain embodiments, the passivation layer  200  comprises an at least partially optically transparent dielectric material (e.g., silicon dioxide) and has a thickness in a range between about 300 Angstroms and about 4000 Angstroms. In certain embodiments, the light emitted from the device  100  in the first direction  313  has a color which is dependent on the thickness of the passivation layer  200  (e.g., due to the effect of the passivation layer  200  on the interferometrically reflected light and/or on the light transmitted through the device  100  in the first direction  313 ). In certain such embodiments, the thickness of the passivation layer  200  is selected to tailor the color of the light emitted from the device  100  in the first direction  313  to be a selected color. For example, the passivation layer  200  can be configured to have a selected thickness within the range described to provide both the desired passivation and the desired tailoring of the color emitted from the device  100  in the first direction  313 . 
     In certain embodiments, the light emitted from the device  100  in the first direction  313  is dependent on an index of refraction of the passivation layer  200 . In some embodiments, the index of refraction of the passivation layer  200  is substantially different from the index of refraction of the surrounding medium. In certain embodiments, the passivation layer  200  comprises silicon dioxide. In other embodiments, the passivation layer  200  comprises another type of oxide or a polymer. 
     In certain embodiments, an additional layer is in contact with the passivation layer  200  such that the passivation layer  200  is positioned between the region  150  and the additional layer. In some embodiments, the color of the light emitted from the device in the first direction  313  and  314  can be tailored by the index of refraction of the additional layer. In certain embodiments, the additional layer comprises an adhesive material such as glue or tape. In some embodiments, the additional layer comprises ink. In one embodiment, for example, as shown by  FIG. 20A , the substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52. An IMOD is constructed on the substrate so that layer  120  comprises Chromium of 70 Angstroms thickness, the layer  130  comprises Aluminum of 60 Angstroms thickness, and the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 2700 Angstroms thickness. In the example embodiment, layer  200  comprises Silicon Dioxide. The layer  200  side of the IMOD is bonded to pieces of PET with an adhesive index matched to the PET, with a refractive index of 1.61, so that some areas of the IMOD are bonded and some are not. When viewed from direction  314  and direction  313 , the reflected and transmitted color will vary, both between areas bonded with PSA, and those in air, and if the thickness of layer  200  is varied.  FIG. 20B  shows this effect for embodiments where the air is adjacent to the layer  200  and where the layer  200  is varied from 1200 Angstroms to 2700 Angstroms (labels A and D).  FIG. 20B  also shows this effect for an embodiment where the layer  200  is bonded to material having a refractive index of 1.61 and where the layer  200  is varied from 1200 Angstroms to 2700 Angstroms (labels B and C).  FIG. 20B  assumes that the viewer is normal to the device  100 . In the example embodiment, and as shown by  FIG. 20B , the “color tuning” effect seen from direction  314  is relatively large. A “color tuning” effect is also seen from direction  313  and in the transmitted color. As shown, there is a narrower range of variation of color with variation of the layer  200  from 1200 Angstroms to 2700 Angstroms with the layer  200  adjacent to the PSA. The portion of  FIG. 20B  identified by the label “Reflection  313 ” represents the total range of variation of color from direction  313  with variation of the layer  200  from 1200 Angstroms to 2700 Angstroms and for a change from air to a PSA interface. 
       FIG. 21  schematically illustrates an example device  100  comprising a first glass layer  210  and a second glass layer  220  in accordance with certain embodiments described herein. The structure  270  comprises the substrate  110 , the first layer  120 , and the second layer  130  and spacer layer  150 . The structure  270  comprising the substrate  110 , the first layer  120 , and the second layer  130  and spacer layer  150  is laminated and located between the first glass layer  210  and the second glass layer  220 . In certain embodiments, one or more adhesive layers  230  are used to laminate the structure comprising the substrate  110 , the first layer  120 , and the second layer  130  with the first glass layer  210  and the second glass layer  220 . In certain embodiments, at least one of the first glass layer  210  and the second glass layer  220  comprises textured glass. The substrate  110 , the first layer  120 , the second layer  130 , and the spacer layer  150  comprise an IMOD, which may be designed to exhibit specific colors in directions  313 ,  314  and  302 ,  306 . As an interferometric device it can exhibit on axis colors that color shift as the viewer changes angle relative to the structure. A textured laminate can be designed with either specific or random angular features on the surface so that light emerging toward a viewer through planar areas of the substrate will emerge at a different angle relative to the IMOD compared to light emerging through a textured feature. Therefore the viewer will see different colors across the textured surface. Examples of textured laminates can be found in U.S. patent application Ser. No. 12/220,947, titled “DEVICES AND METHODS FOR ENHANCING COLOR SHIFT OF INTERFEROMETRIC MODULATORS”, filed Jul. 29, 2008, which is incorporated in its entirety by reference herein. 
       FIG. 22  schematically illustrates an example device  100  having a first layer  120 , a second layer  130 , a third layer  240 , and a fourth layer  250  in accordance with certain embodiments described herein. The first layer  120  and the second layer  130  are over a first surface of the substrate  110 . The third layer  240  and the fourth layer  250  are over a second surface of the substrate  110 . The third layer  240  is partially optically absorptive, partially optically transmissive, and partially optically reflective. The fourth layer  250  is spaced from the third layer  240 , with the third layer  240  located between the substrate  110  and the fourth layer  250 . The fourth layer  250  is partially optically absorptive, partially optically transmissive, and partially optically reflective. In certain embodiments, the device  100  further comprises a light source  140  positioned relative to the substrate  110  such that the first layer  120  and the second layer  130  are located between the substrate  110  and the light source  140 . 
     As schematically illustrated by  FIG. 22 , in certain embodiments, the device  100  further comprises a spacer  260  (e.g., an at least partially optically transparent dielectric layer or a region filled with air) located between the third layer  240  and the fourth layer  250 . In certain embodiments, one or both of the spacer  150  located between the first layer  120  and the second layer  130  and the spacer  260  located between the third layer  240  and the fourth layer  250  comprises a region filled with air. The structure comprising layers  120 ,  150 ,  130  and the structure comprising layers  260 ,  250 ,  240  may each be described as individual IMODs in certain embodiments. The structure comprising layers  120 ,  150 ,  130  will be described herein as IMOD I and the structure comprising layers  260 ,  250 ,  240  will be described herein as IMOD II. These descriptions are for the purposes of illustration and are not limiting. In one embodiment, for example, substrate  110  comprises of glass of approximately 10 mm thickness with a refractive index of approximately 1.52, the layer  120  comprises Chromium of 70 Angstroms thickness, the layer  130  comprises Aluminum of 40 to 100 Angstroms thickness, and the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 1000 to 5000 Angstroms thickness. As has been described herein, the spacer  150  can be selected to provide a specific transmitted and reflected color, with the layer  120  (e.g., absorber layer) and the layer  130  (e.g., reflector layer) selected to provide the desired brightness and color saturation. Layers  250 ,  240  and spacer  260  may be selected in a similar way. Each of IMODs I and II are independent but, depending on the level of transmission, the IMODs can interact so the viewer will see colors that are a combination of the two. In one embodiment, for example, layer  120  comprises Chromium of 70 Angstroms thickness, the layer  130  comprises Aluminum of 60 Angstroms thickness, and the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 2000 Angstroms thickness. In the example embodiment, the layer  240  comprises Chromium of 70 Angstroms thickness, the layer  250  comprises Aluminum of 60 Angstroms thickness, and the layer  240  and the layer  250  are spaced by spacing dielectric layer  260  comprising Silicon Dioxide of 4250 Angstroms thickness. The resulting on axis transmission plots for IMODs I and II are shown in  FIG. 23  (front reflections are excluded in  FIG. 23 ). IMOD I has a first order red transmission response, IMOD II is magenta, but the effect of overlaying them as described will be for IMOD II to act as a filter for the red IMOD I, increasing its color saturation. 
     In certain embodiments, a plurality of devices, including one or more devices  100 , can be arranged in a manner generally similar to the embodiments described above with respect to, for example,  FIGS. 1-5 . In certain embodiments, the plurality of devices can have different interferometric and/or transmissive performance. For example, a plurality of devices can be arranged in a row/column array. Contrast among these different devices can be used to generate a viewable image. For example, in certain embodiments, multiple devices can be formed from a patterned layered structure over the substrate  110 . A first device  100 , for example, can comprise a first layer  120  and a second layer  130  as described herein, and can be the source of both interferometrically reflected light and light transmitted through the first device  100 . A second device can comprise a first layer that is partially optically absorptive, partially optically transmissive, and partially optically reflective (e.g., a chromium layer) and a second layer spaced from the first layer such that the second layer is located between the substrate  110  and the first layer. The second layer can be at least partially optically reflective and substantially optically non-transmissive. In certain such embodiments, the first layer and the second layer are portions of an interferometric modulator as described herein. 
     In certain embodiments, the first device  100  exhibits a first color which is the result of a first portion  300  of light, a second portion  301  of light, and a third portion  302  of light being emitted in a first direction  313  from the device  100  as described herein. In certain embodiments, the first portion  300  of light and the second portion  301  of light interfere to produce light having a first color, and the third portion  302  of light has a second color different from the first color. 
     In certain embodiments, the second device exhibits a second color which is the result of a fourth portion of light incident on the substrate  110 , transmitted through the substrate  110 , transmitted through the first layer of the second device, reflected by the second layer of the second device, transmitted through the first layer of the second device, transmitted through the substrate  110 , and emitted from the device in the first direction  313 , and a fifth portion of light incident on the substrate  110 , transmitted through the substrate  110 , reflected by the first layer of the second device, transmitted through the substrate  110 , and emitted from the second device in the first direction  313 . The fourth portion of light and the fifth portion of light interfere to produce light having the second color. In certain embodiments, the second color is different from the first color. 
     In certain embodiments, the plurality of devices further comprises an anti-reflection coating on a surface of the substrate  110  such that the substrate  110  is located between the anti-reflective coating and the first layer  120  of the first device  100  and the first layer of the second device. In certain embodiments, the first layer  120  of the first device  100  is contiguous with the first layer of the second device (e.g., the first layer  120  of the first device  100  and the first layer of the second device can be portions of a common layer). For example, an Chromium layer can have one or more portions that have a thickness less than 1000 Angstroms serving as the first layer  120  of the first device  100 , and also serving as the first layer of the second device. 
     In certain embodiments, the plurality of devices further comprises a third device which is substantially transmissive to light incident on the third device. In certain such embodiments, the first device  100  exhibits a first color, the second device exhibits a second color different from the first color, and the third device exhibits a third color different from both the first color and the second color. Contrast among the first, second, and third devices can be used to generate a viewable image. 
     The effect of varying reflector and absorber thickness will now be illustrated with reference to certain embodiments of the device  100  of  FIG. 24A  wherein substrate  110  comprises glass of approximately 10 mm thickness with a refractive index of approximately 1.52, the layer  120  comprises Chromium of 20 to 80 Angstroms thickness, the layer  130  comprises Aluminum of 30 to 150 Angstroms, and the layer  120  and the layer  130  are spaced by spacing dielectric layer  150  comprising Silicon Dioxide of 90 to 450 Angstroms thickness. For simplicity, the view is on axis from within substrate  110  (e.g., ignoring the substrate to air interface).  FIGS. 24B-24D  illustrate the reflectivity, a CIE chromaticity diagram, and the transmittance, respectively, of example embodiments of the device  100  of  FIG. 24A  wherein the layer  120  comprises Chromium of 70 Angstroms thickness, the spacer layer  150  comprises Silicon Dioxide of 3400 Angstroms thickness, and the reflector layer  130  comprises Aluminum and is varied from between 30 and 150 Angstroms thickness. As illustrated by  FIGS. 24B-24D , the effect is relatively larger on the reflectivity and transmittance and there is relatively less effect on the color saturation.  FIGS. 24E-24F  show the reflectivity/transmittance and a CIE chromaticity diagram, respectively, of embodiments of the device  100  of  FIG. 24A  where the reflector layer  130  comprises Aluminum 60 Angstroms thick, the spacer layer  150  comprises Silicon Dioxide 3400 Angstroms thick, and the absorber layer  120  comprises Chromium and is varied from 20 Angstroms to 70 Angstroms thickness. The effect on the color is different than the embodiment illustrated with respect to  FIGS. 24B-24D  and there is a relatively greater impact on color saturation. 
     One aspect of an IMOD device is angular color shift.  FIG. 25A  shows a CIE chromaticity diagram of another embodiment of a device  100  (on glass) where the absorber layer  120  comprises Chromium 70 Angstroms thick, the spacer layer  150  comprises Silicon Dioxide 3400 Angstroms thick, and the reflector layer  130  comprises Aluminum 60 Angstroms thick. The example embodiment exhibits a second order color with peak reflectivity of 535 nm on axis in direction  313 . View angle (from within substrate  110 , for simplicity and not by way of limitation) is varied from 0 to 30 degrees in the example embodiment. 
       FIG. 25B  shows a CIE chromaticity diagram of another example embodiment wherein the absorber layer  120  and the reflector layer  130  comprise the same materials having the same thicknesses as the embodiment described with respect to  FIG. 25A  but where the spacer layer  150  is 1580 Angstroms thick. The embodiment illustrated with respect to  FIG. 25B  has a green reflection peaking at 535 nm, similar to the embodiment illustrated with respect to  FIG. 25A , but as a first order color response, it exhibits less angular color shift.  FIGS. 25C-25D  illustrate example embodiments of the device  100  wherein the absorber layer  120  and the reflector layer  130  comprise the same materials having the same thicknesses as the embodiments described with respect to  FIGS. 25A-B , but where the spacer layer  150  comprises Zinc Oxide (which has higher refractive index than Silicon Dioxide) and air (lower index), respectively. The spacer thickness for the embodiments of  FIGS. 25C-25D  is adjusted in each case to provide the same peak reflected wavelength (535 nm) on axis. Each figure shows the effect (viewed from within substrate  110  for simplicity, and not by way of limitation) of varying the view angle from 0 to 30 degrees. As illustrated, the embodiments having lower index spacers exhibit more color shift. For example, the higher index spacer layer  150  (e.g., Zinc Oxide) of  FIG. 25C  has the same peak reflectivity of 535 nm at 0 degrees viewing angle, but exhibits less color shift than the lower index spacer layer  150  (e.g., Silicon Dioxide) of the embodiment of  FIG. 25B . This provides another design parameter for a semi transparent IMOD. In certain embodiments, the IMOD may also be combined with texture to accentuate the color shift effect, or diffusive materials which can be used to de-emphasize the color shift effect, depending on the aesthetic desired. 
       FIG. 26  illustrates another embodiment of the device  100  wherein the absorber layer  120  and the reflector layer  130  comprise the same materials having the same thicknesses as the embodiments described with respect to  FIGS. 24A-24D , viewed on axis, but wherein the spacer layer  150  is varied from 1000 Angstroms to 4250 Angstroms, through first and second order colors.  FIG. 26  shows that as the spacer thickness varies the color will vary over a relatively wide range, and identifies colors that are first order (less saturated) or second order (more saturated). Colors at the extreme end of the range depicted (for example the magentas with spacer layers  150  approximately 4000 Angstroms or more) may also include third order colors, in addition to second order colors. 
     Although certain embodiments and examples are discussed above, it is understood that the inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the embodiments and obvious modifications and equivalents thereof. Thus, for example, in any method or process disclosed herein, the acts or operations making up the method/process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various aspects and advantages of the embodiments have been described where appropriate. It is to be understood that not necessarily all such aspects or advantages may be achieved in accordance with any particular embodiment. Thus, for example, it should be recognized that the various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may be taught or suggested herein.