EMBEDDED SURFACE DIFFUSER

A diffuser stack may include a first film with a first index of refraction and a second film proximate the first film. The second film may have a second index of refraction that is higher than the first index of refraction. An interface between the first film and the second film may include an array of microlenses of substantially randomized sizes. The microlenses may include sections of features that are substantially spherical, polygonal, conical, etc. The first and second films may be disposed between an array of pixels and a substantially transparent substrate. An anti-reflective layer may be disposed between the first film and the second film.

TECHNICAL FIELD

This disclosure relates to diffuser stacks, particularly diffuser stacks suitable for display devices.

DESCRIPTION OF THE RELATED TECHNOLOGY

Electromechanical systems (EMS) include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components (e.g., mirrors) and electronics. EMS can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical and electromechanical devices.

One type of EMS device is called an interferometric modulator (IMOD). As used herein, the term IMOD or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an IMOD may include a highly reflective metal plate and a partially absorptive and partially transparent and/or reflective plate, and capable of relative motion upon application of an appropriate electrical signal. In an implementation, one plate may include a stationary layer deposited on a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the IMOD and the reflection spectrum. IMOD devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with information display capabilities.

In reflective displays such as interferometric modulator (IMOD) displays, it can be advantageous to include a diffuser layer or stack. Such diffusers can improve the viewing angle of a display device. Also, reflective displays including IMOD displays may have specular reflections of light sources that can appear as glare and thereby degrade the image shown on the display, and diffusers can reduce such specular reflections.

SUMMARY

One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus which includes a first film having a first index of refraction and a second film proximate the first film, the second film having a second index of refraction that is higher than the first index of refraction. An interface between the first film and the second film may include an array of microlenses of substantially randomized sizes.

In some implementations, the microlenses may include portions of substantially spherical, polygonal or conical features. The microlenses may include concaves formed in the first film. The microlenses may include portions of the second film that fill the concaves.

The apparatus also may include an array of pixels disposed proximate the second film and a substantially transparent substrate disposed proximate the first film. In some implementations, the pixels may include interferometric modulator (IMOD) pixels. In some such implementations, the IMOD pixels may include multi-state IMOD pixels. In some such implementations, a single pixel of the array of pixels may corresponds with multiple microlenses. For example, a single pixel of the array of pixels may correspond with 10 or more microlenses.

The substantially transparent substrate may be capable of functioning as a light guide. In some implementations, the light guide may include a plurality of light-extracting features capable of extracting light from the light guide and capable of providing at least a portion of the light to the array of pixels. In some implementations, a cladding layer may be disposed between the substantially transparent substrate and the first film. For example, the cladding layer may have a third index of refraction that is lower than the first index of refraction. In some implementations, the first film has a lower index of refraction than that of the substantially transparent substrate.

The apparatus may include a control system that may be capable of processing image data and may be capable of controlling the array of pixels according to the processed image data. The control system may include a driver circuit capable of sending at least one signal to the array of pixels and a controller capable of sending at least a portion of the image data to the driver circuit. The apparatus may include an image source module capable of sending the image data to the control system. The image source module may include at least one of a receiver, transceiver, and transmitter. The apparatus may include an input device capable of receiving input data and capable of communicating the input data to the control system.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of fabricating a diffuser stack. The method may involve depositing a first film having a first index of refraction on a substantially transparent layer. In some implementations, the substantially transparent layer may include a cladding layer having a third index of refraction that is lower than the first index of refraction and a substantially transparent substrate. The method may involve etching features that may be referred to herein as “craters” or “concaves” into the first film. In some implementations, the concaves may have substantially random sizes.

In some implementations, the method may involve depositing, after the etching process, an anti-reflective layer on the first film. In some implementations, the anti-reflective layer may be conformal. The method may involve depositing a second film on the first film (or on the anti-reflective layer), to form an array of microlenses of substantially randomized sizes. In some implementations, the second film may have a second index of refraction that is higher than the first index of refraction.

The method may involve forming an array of pixels on the second film. In some implementations, the pixels may include interferometric modulator (IMOD) pixels, at least some of which may be multi-state IMOD pixels.

Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Although the examples provided in this summary are primarily described in terms of MEMS-based displays, the concepts provided herein may apply to other types of displays, such as liquid crystal displays (LCD), organic light-emitting diode (OLED) displays, electrophoretic displays, and field emission displays. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.

DETAILED DESCRIPTION

It can be challenging to provide sufficient haze while minimizing reflection and unwanted artifacts. Moreover, currently available diffusers are generally formed of plastic or similar material. Such material may have a melting point that is too low to be compatible with other fabrication processes. Some implementations described herein provide a diffuser that may be substantially transparent, with low amounts of back scatter and reflectivity, while providing a substantial haze value.

Some implementations described herein include an apparatus having a first film with a first index of refraction and a second film proximate the first film. The second film may have a second index of refraction that is higher than the first index of refraction. An interface between the first film and the second film may include an array of microlenses of substantially randomized sizes. The microlenses may include sections of features that are substantially spherical, polygonal, conical, etc. According to some implementations, the first and second films may be disposed between an array of display device pixels and a substantially transparent substrate, such as a glass substrate, a polymer substrate, etc.

The microlenses may include concaves or craters formed in the first film. For example, the concaves may be formed in the first film according to an etching process, which may include dry and/or wet etching. The microlenses may include portions of the second film that fill the concaves. These portions of the second film may be part of a passivation layer that substantially fills the concaves. In some implementations, an anti-reflective layer may be disposed between the first film and the second film. In some implementations, the anti-reflective layer conforms to the concaves or craters formed in the first film.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Some implementations may provide a diffuser stack that provides low amounts of back scatter and reflectivity, while providing a substantial haze value. Some diffuser stacks have a melting point that is sufficiently high to be compatible with other fabrication processes. For example, some such diffuser stacks have a melting point that is sufficiently high that an array of pixels, such as interferometric modulator (IMOD) pixels, may be formed on the diffuser stack without causing the diffuser stack to melt or deform. Forming the diffuser stack between a substantially transparent substrate (such as a display substrate) and an array of pixels, instead of on the opposite side of the substrate, can provide improved optical properties, such as improved resolution. When the diffuser stack is positioned farther from the pixels, this configuration can reduce the resolution by blurring images formed by the pixels. When the diffuser stack is positioned closer to the pixels, the resolution remains higher and the diffuser stack can increase the viewing angle and reduce specular reflections.

FIG. 1is a block diagram that includes example elements of a diffuser stack. In this example, the diffuser stack100includes a first film, the low-index film105, having a first index of refraction. The diffuser stack100also includes a second film, the high-index film110in this example, having a second index of refraction that is higher than the first index of refraction. However, in alternative implementations the second film may have an index of refraction that is lower than the first index of refraction. The higher the difference between the first and second indices of refraction, the higher the haze of the diffuser stack. Hence, for high haze implementations, the second index of refraction will be larger than both the first index of refraction and the index of refraction of the substrate. In this example, an interface between the low-index film105and the high-index film110includes an array of microlenses of substantially randomized sizes.

FIGS. 2A-2Cshow cross-sections through examples of diffuser stacks. In these examples, the diffuser stack100is disposed on a substrate205, which is a glass substrate in these examples. In some implementations, the glass substrate may include a borosilicate glass, a soda lime glass, quartz, Pyrex™, or other suitable glass material. In alternative implementations, the substrate205may include suitable substantially transparent non-glass materials, such as polycarbonate, acrylic, polyethylene terephthalate (PET) or polyether ether ketone (PEEK).

Here, the diffuser stack100includes a low-index film105and a high-index film110. In some implementations, the low-index film105may include one or more materials having a relatively low index of refraction, such as SiO2, SiOC (carbon-doped silicon oxide), spin-on glass (SOG), magnesium fluoride (MgF2), polytetrafluoroethylene (PTFE), etc. In some implementations, the low-index film105may have a thickness in the range of 1 to 10 microns, or 1 to 5 microns, or 1 to 3 microns.

The high-index film110may include one or more materials that have a higher index of refraction than that of the low-index film105. For example, in some implementations the high-index film110may include SiNxOx. As known by those of ordinary skill in the art, the index of refraction of SiNxOxmay be controlled by varying the ratio of nitrogen to oxygen and/or by varying the pressure during a sputtering process. Accordingly, the index of refraction of a film formed of SiNxOxmay vary substantially, e.g., from 1.7 or less to 2 or more. In alternative examples, the high-index film110may include SiNx, ZrO2, TiO2and/or Nb2O5. In some implementations, the high-index film110may have a thickness in the range of 1 to 10 microns.

In the implementations shown inFIGS. 2A-2C, an interface between the low-index film105and the high-index film110includes an array of microlenses212having substantially randomized sizes. In these examples, the microlenses212include portions of substantially spherical features. However, in alternative examples, the microlenses212may include other shapes, such as portions of substantially polygonal or conical features.

As described in more detail below, in some implementations the array of microlenses212may be formed by etching features of substantially randomized sizes into the low-index film105and filling in the features with the high-index film110. In some implementations, the etching process may include a dry etch process and/or a wet etch process. In some implementations, high-index film110may be formed via deposition of a high refractive index passivation coating that substantially fills the concaves in the first film. However, in alternative implementations, the array of microlenses212may be formed by etching features of substantially randomized sizes into a higher-index film and filling in the features with a lower-index film. Some implementations may include an anti-reflective layer between the higher-index film and the lower-index film, e.g., as described elsewhere herein.

In the examples shown inFIGS. 2A-2C, an array of pixels210is disposed on the diffuser stack100. As described in more detail below, in some implementations the array of pixels210may be fabricated on the diffuser stack100. For example, the diffuser stack100may be fabricated on a substantially transparent stack that includes the substrate205and subsequently the array of pixels210may be fabricated on the diffuser stack100. As noted above, it can be advantageous to have the diffuser stack100disposed between a “display glass” such as the substrate205and the array of pixels210. However, it would not be feasible to simply fabricate the array of pixels210on a typical diffusing film. Such films are generally made of a polymer with a relatively low melting point. The process of fabricating an array of pixels210, such as an IMOD array, generally involves stages at which the temperature is substantially higher than this melting point. Therefore, if one were to attempt to fabricate an IMOD array on a typical diffusing film, the diffusing film would melt during the fabrication process.

In the examples shown inFIGS. 2B and 2C, the substrate205is capable of functioning as a light guide. In these implementations, a cladding layer220is disposed between the substrate205and the low-index film105. The cladding layer220may have a lower index of refraction than the low-index film105and may allow the substrate205to function as a light guide. For example, if the low-index film105is formed of SiO2, the cladding layer220may be formed of spin-on glass, MgF2or SiOC. In some implementations, the cladding layer220can be about 1 micron thick or more and have an index of 1.38 or less. However, in some implementations, the refractive index of the low-index film105may be sufficiently low that no additional cladding layer is necessary for the substrate205to function as a light guide.

FIG. 2Cshows an example of a light source227, which includes a light-emitting diode in this example, providing light to the substrate205. In the examples shown inFIGS. 2B and 2C, the substrate205includes a plurality of light-extracting features215capable of extracting light from the light guide and providing at least a portion of the light to the array of pixels210. It is understood thatFIGS. 2B and 2Care schematic, and that the shape and density of light-extracting features215may vary according to the application and are only schematically shown relative to the size and density of the array of microlenses212.

In the example shown inFIG. 2C, the light-extracting features215are capable of functioning as the electrodes of a touch panel. Here, a passivation layer229is formed on the light-extracting features215.

Like the implementation shown inFIG. 2A, the examples ofFIGS. 2B and 2Calso include an array of microlenses212. In the example shown inFIG. 2C, a single pixel226of the array of pixels210corresponds with multiple microlenses212. In some implementations, a single pixel226of the array of pixels210may correspond with 10 or more microlenses212. In some examples, a single pixel226of the array of pixels210may correspond with 25 or more microlenses212.

In order to achieve a high haze value for the diffuser stack100, it is desirable to minimize the light reflected in a specular direction (due to Fresnel reflections at flat dielectric-dielectric interfaces). Therefore, the microlenses212may be closely packed so that there is only a small amount of area not occupied by the microlenses212, from which light may reflect in a specular fashion from the diffuser stack100.

If the microlenses212are formed in a regular or periodic pattern, artifacts such as Moiré effects and diffraction patterns may result. Accordingly, in various implementations the microlenses212may have sizes and/or distributions that are substantially random, in order to avoid such artifacts. In the examples shown inFIGS. 2A-2C, the microlenses have different sizes, each of which has a radius of curvature (ROC) and a depth. The ROC and/or the depth may be randomized.

FIGS. 2D and 2Eshow examples of microlenses having different depths and radii of curvature. Referring first toFIG. 2D, the microlens2121has a radius of curvature ROC1and a depth d1.FIG. 2Dalso provides examples of inter-microlens areas230, from which light may reflect in a specular direction.

As compared to the microlens2121, the microlens2122ofFIG. 2Ehas a larger radius of curvature ROC2. However, the microlens2122has a relatively smaller depth d2. Accordingly, a larger ROC does not necessarily correspond with a larger depth.

In some implementations, the radii of curvature and/or the depths of the microlenses212may be selected from a random or quasi-random distribution. For example, the radii of curvature of the microlenses212may be selected from a Gaussian random distribution, with a specified mean and a specified standard deviation for the distribution. In various implementations, the mean of the radii of curvature in the random distribution can range from 2 to 10 microns, or 2 to 6 microns. In various implementations, the depth of the concaves into the surface of the first layer can range from 200 nm (0.2 microns) to 5 microns, or 500 nm (0.5 microns) to 2.5 microns. In some implementations, the depths are relatively similar with random or quasi-random distribution of the radii of curvature, while in other implementations, both the depth and the radii of curvature have a random or quasi-random distribution. Wet etching processes tend to produce concaves having somewhat uniform depth, while dry etching processes tend to produce more random depths.

The haze of the diffuser stack100may be controlled by varying the mean and standard deviation of the ROC and/or the difference between the refractive indices of the low-index film105and the high-index film110. A higher difference between these refractive indices produces a higher haze value, which indicates increased diffusion. However, a higher difference between the refractive indices also causes more Fresnel reflection and back scatter at the interface between low-index film105and the high-index film110, which may reduce the reflective contrast ratio of reflective pixels of the array of pixels210. For example, a higher difference between the refractive indices may reduce the reflective contrast ratio of MS-IMOD pixels. For some reflective displays, diffusers have haze values of about 70-80%. For example, for reflective displays that include diffusers having haze values of about 70-80%, in some implementations the difference between the index of refraction of the first layer and the second layer is about 0.3 or more. However, for very low haze implementations, the difference between the index of refraction of the first layer and the second layer can be relatively small.

In the example shown inFIG. 2B, an anti-reflective layer225is disposed between the low-index film105and the high-index film110. The anti-reflective layer225may reduce the amount of Fresnel reflection and back scatter of the microlenses212. In this example, the anti-reflective layer225substantially conforms to the shape of concaves formed in the low-index film105. The anti-reflective layer225may, for example, be deposited after forming the microlenses212in the low-index film105and before depositing the high-index film110.

In some implementations, the anti-reflective layer may include SiNxOx. As noted above, the index of refraction of SiNxOxmay be controlled according to the ratio of nitrogen to oxygen and/or by varying the pressure during a sputtering process. Accordingly, the index of refraction of an anti-reflective layer225formed of SiNxOxmay be selected, as appropriate, according to the other materials used to form the diffuser stack100. Some examples are provided below. However, in alternative implementations the anti-reflective layer225may include other materials, such as MgF2.

In some examples, the anti-reflective layer225may be a quarter-wave index-matching layer. In some implementations, the thickness (dAR) and refractive index (nAR) of the anti-reflective layer225are chosen according to Equations (1) and (2), below:

In Equation (1), nFilm 1represents the index of refraction of a first film (e.g., the low-index film105) and nFilm 2represents the index of refraction of a second film (e.g., the high-index film110). If the anti-reflective layer225is thin, it may adopt the shape of the concaves in the low-index film105. The shape of the high-index film110may conform to the shape of the concaves in the first film. Therefore, including an anti-reflective layer225may not substantially change the haze of the diffusion layer, but may nonetheless reduce the amount of Fresnel reflection and back scatter of the microlenses212.

Table 1 shows some examples of simulation results of optical properties for diffuser stacks with and without anti-reflective layers225:

One diffuser stack100represented in Table 1 includes a low-index film105of SiO2, with a refractive index of 1.46, and a second film of SiNxOxwith a refractive index of 1.71. The other diffuser stack represented in Table 1 includes a low-index film105of SOG, having a refractive index of 1.4, and a second film of SiNxOxwith a refractive index of 2. In the latter case, the low-index film105also may function as a cladding layer for allowing the substrate205to function as a light guide. Alternatively, or additionally, the diffuser stack100also may include a separate cladding layer220between the low-index film105and the substrate205(e.g., as shown inFIG. 2B), to ensure sufficient internal reflection for the substrate205to function as a light guide.

In the examples shown in Table 1, adding the anti-reflective layer225can reduce back scatter by approximately 10% and can improve forward transmission. However, adding the anti-reflective layer225may not substantially affect the haze value.

FIG. 3is a flow diagram that outlines an example of a process of fabricating a diffuser stack. The operations of method300are not necessarily performed in the order shown inFIG. 3. Moreover, method300may involve more or fewer blocks than are shown inFIG. 3. In this example, the method300begins with block305, which involves depositing a first film having a first index of refraction on a substantially transparent layer. For example, block305may involve a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, or another such process for depositing thin films. In some implementations, the first index of refraction is lower than an index of refraction of the substrate. In some implementations, the substantially transparent layer may include a cladding layer and a substantially transparent substrate. The cladding layer may have an index of refraction that is lower than the first index of refraction.

Here, block310involves etching concaves into the first film. In this example, the concaves have substantially random sizes. For example, the concaves may have substantially random radii of curvature and/or depths. In this implementation, optional block315involves depositing, after the etching process, an anti-reflective layer on the first film. Block315may, for example, involve a PVD process, a CVD process, etc. In some implementations, depositing the anti-reflective layer includes conformally depositing the anti-reflective layer so that it conforms to the shape of the etched first film. Block320may involve a PVD process, a CVD process, etc. Here, block320involves depositing a second film on the first film, or the anti-reflective layer, to form an array of microlenses of substantially randomized sizes. In this example, the second film has a second index of refraction that is higher than the first index of refraction. In some implementations, the deposited second film planarizes the topography of the first film or the stack of the first film and the anti-reflective layer.

FIGS. 4A-4Fare cross-sectional views that illustrate stages in an example of a process of fabricating a diffuser stack.FIG. 4Aillustrates an example of a low-index film105deposited on a substrate205. The configuration shown inFIG. 4Amay result, for example, after block305ofFIG. 3.

At the stage shown inFIG. 4B, photoresist material405has been deposited on the low-index film105and patterned. The particular pattern of photoresist material405shown inFIG. 4Bis merely an example. In alternative implementations, the photoresist material405may processed according to a grayscale lithography process. Grayscale lithography, often used with dry etch techniques, allows greater control of the curvature of the walls of the concaves formed into the substrate. Grayscale techniques allow forming concaves onto the photoresist surface, and the surface formed on the photoresist can then be transferred to the substrate using the etchant.

At the stage shown inFIG. 4C, concaves have been etched into the first film. Accordingly,FIG. 4Ccorresponds with the completion of a process such as that of block310ofFIG. 3. In this example, the concaves have substantially random sizes and have been formed by a wet etch process. However, in other implementations, the process could include a dry etch process. Some such examples are described below with reference toFIGS. 5A and 5B.

In this implementation, the photoresist material405has been patterned such that the radii of curvature and/or the depths of the concaves410have a random or quasi-random distribution. For example, the radii of curvature of the concaves410may be selected from a Gaussian random distribution, with a specified mean and a specified standard deviation for the distribution. In some examples, the arrangement of the concaves410may be selected according to a computer simulation based, at least in part, on the principles of molecular dynamics. For example, the layout of a mask used to pattern the photoresist material405may be selected according to a computer simulation based, at least in part, on molecular dynamics.

At the stage shown inFIG. 4D, the photoresist material405has been removed and an anti-reflective layer225has been deposited on the low-index film105. In this implementation, the anti-reflective layer225is substantially conformal with the shapes of the concaves410.

In the example shown inFIG. 4E, a layer of high-index film110has been deposited on the anti-reflective layer225. Portions of the high-index film110have been deposited in the concaves410, on the anti-reflective layer225, to form microlenses212. Accordingly, the resulting diffuser stack100includes an array of microlenses212having substantially random sizes. In these examples, the microlenses212include portions of substantially spherical features. However, in alternative examples, the microlenses212may include other shapes, such as portions of substantially polygonal or conical features.

FIG. 4Fshows an example of an array of pixels210proximate the diffuser stack100. In this example, the array of pixels210has been fabricated on the diffuser stack100. Some examples of fabricating an array of pixels210are provided below, especially inFIG. 10. InFIG. 10, the “substrate” referenced in block82may include substrate205, low-index film105, and high-index film110since the array pixels210are formed over both the substrate205and the diffuser stack100.

FIGS. 5A-5Cillustrate stages in one example of a process of fabricating microlenses that include portions of substantially conical features. In this example, at the stage depicted inFIG. 5Athe photoresist material405has been deposited on the low-index film105and patterned. However, in this example, the concaves410are formed by a dry etch process. At the stage depicted inFIG. 5A, the sidewalls505are substantially vertical in this example and the concaves410have substantially the same depths.

FIG. 5Bshows an example of the stack ofFIG. 5Aafter a thermal reflow process. At the stage depicted inFIG. 5B, the reflow process has changed the shape of the sidewalls505. In alternative implementations, the reflow process may produce other shapes for the sidewalls505, such as curved shapes.

FIG. 5Cshows an example of concaves formed after etching through the photoresist material405and into portions of the low-index film105shown inFIG. 5B.FIG. 5Cmay, for example, depict concaves410resulting from a dry etching process which has transferred the topography of the photoresist material405ofFIG. 5Binto the low-index film105ofFIG. 5C. In this example, the resulting concaves410are substantially conical. Accordingly, if the concaves410were filled with a high-index film110, the resulting microlenses212would also be substantially conical.

FIGS. 6A and 6Bshow examples of microlenses having different shapes. In the example shown inFIG. 6A, the microlenses212have been formed in octagonal concaves410after a dry etch process. Accordingly, the microlenses212are octagonal in cross-section. In the example shown inFIG. 6B, the concaves410are substantially circular in cross-section and have been formed by a wet etch process. Accordingly, the resulting microlenses212are substantially circular in cross-section.

FIG. 7shows an example of an isometric view depicting two adjacent pixels in a series of pixels of an IMOD display device. The IMOD display device includes one or more interferometric MEMS display elements. In these devices, the pixels of the MEMS display elements can be positioned in either a bright or dark state. In the bright (“relaxed,” “open” or “on”) state, the display element reflects a large portion of incident visible light, e.g., to a user. Conversely, in the dark (“actuated,” “closed” or “off”) state, the display element reflects little incident visible light. In some implementations, the light reflectance properties of the on and off states may be reversed. MEMS pixels can be capable of reflecting predominantly at particular wavelengths allowing for a color display in addition to black and white. In some implementations, by using multiple display elements, different intensities of color primaries and shades of gray can be achieved.

The IMOD display device can include an array of IMOD display elements which may be arranged in rows and columns. Each display element in the array can include at least a pair of reflective and semi-reflective layers, such as a movable reflective layer (i.e., a movable layer, also referred to as a mechanical layer) and a fixed partially reflective layer (i.e., a stationary layer), positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap, cavity or optical resonant cavity). The movable reflective layer may be moved between at least two positions. For example, in a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively and/or destructively depending on the position of the movable reflective layer and the wavelength(s) of the incident light, producing either an overall reflective or non-reflective state for each display element. In some implementations, the display element may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when actuated, absorbing and/or destructively interfering light within the visible range. In some other implementations, however, an IMOD display element may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the display elements to change states. In some other implementations, an applied charge can drive the display elements to change states.

The depicted portion of the array inFIG. 7includes two adjacent interferometric MEMS display elements in the form of IMOD display elements12. In the display element12on the right (as illustrated), the movable reflective layer14is illustrated in an actuated position near, adjacent or touching the optical stack16. The voltage Vbiasapplied across the display element12on the right is sufficient to move and also maintain the movable reflective layer14in the actuated position. In the display element12on the left (as illustrated), a movable reflective layer14is illustrated in a relaxed position at a distance (which may be predetermined based on design parameters) from an optical stack16, which includes a partially reflective layer. The voltage V0applied across the display element12on the left is insufficient to cause actuation of the movable reflective layer14to an actuated position such as that of the display element12on the right.

InFIG. 7, the reflective properties of IMOD display elements12are generally illustrated with arrows indicating light13incident upon the IMOD display elements12, and light15reflecting from the display element12on the left. Most of the light13incident upon the display elements12may be transmitted through the transparent substrate20, toward the optical stack16. A portion of the light incident upon the optical stack16may be transmitted through the partially reflective layer of the optical stack16, and a portion will be reflected back through the transparent substrate20. The portion of light13that is transmitted through the optical stack16may be reflected from the movable reflective layer14, back toward (and through) the transparent substrate20. Interference (constructive and/or destructive) between the light reflected from the partially reflective layer of the optical stack16and the light reflected from the movable reflective layer14will determine in part the intensity of wavelength(s) of light15reflected from the display element12on the viewing or substrate side of the device. In some implementations, the transparent substrate20can be a glass substrate (sometimes referred to as a glass plate or panel). The glass substrate may be or include, for example, a borosilicate glass, a soda lime glass, quartz, Pyrex, or other suitable glass material. In some implementations, the glass substrate may have a thickness of 0.3, 0.5 or 0.7 millimeters, although in some implementations the glass substrate can be thicker (such as tens of millimeters) or thinner (such as less than 0.3 millimeters). In some implementations, a non-glass substrate can be used, such as a polycarbonate, acrylic, polyethylene terephthalate (PET) or polyether ether ketone (PEEK) substrate. In such an implementation, the non-glass substrate will likely have a thickness of less than 0.7 millimeters, although the substrate may be thicker depending on the design considerations. In some implementations, a non-transparent substrate, such as a metal foil or stainless steel-based substrate can be used. For example, a reverse-IMOD-based display, which includes a fixed reflective layer and a movable layer which is partially transmissive and partially reflective, may be adapted to be viewed from the opposite side of a substrate as the display elements12ofFIG. 7and may be supported by a non-transparent substrate.

The optical stack16can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer, and a transparent dielectric layer. In some implementations, the optical stack16is 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 substrate20. The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals (e.g., chromium and/or molybdenum), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, certain portions of the optical stack16can include a single semi-transparent thickness of metal or semiconductor which serves as both a partial optical absorber and electrical conductor, while different, electrically more conductive layers or portions (e.g., of the optical stack16or of other structures of the display element) can serve to bus signals between IMOD display elements. The optical stack16also can include one or more insulating or dielectric layers covering one or more conductive layers or an electrically conductive/partially absorptive layer.

In some implementations, at least some of the layer(s) of the optical stack16can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having ordinary skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer14, and these strips may form column electrodes in a display device. The movable reflective layer14may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack16) to form columns deposited on top of supports, such as the illustrated posts18, and an intervening sacrificial material located between the posts18. When the sacrificial material is etched away, a defined gap19, or optical cavity, can be formed between the movable reflective layer14and the optical stack16. In some implementations, the spacing between posts18may be approximately 1-1000 μm, while the gap19may be approximately less than 10,000 Angstroms (Å).

In some implementations, each IMOD display element, whether in the actuated or relaxed state, can be considered as a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer14remains in a mechanically relaxed state, as illustrated by the display element12on the left inFIG. 7, with the gap19between the movable reflective layer14and optical stack16. However, when a potential difference, i.e., a voltage, is applied to at least one of a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding display element becomes charged, and electrostatic forces pull the electrodes together. If the applied voltage exceeds a threshold, the movable reflective layer14can deform and move near or against the optical stack16. A dielectric layer (not shown) within the optical stack16may prevent shorting and control the separation distance between the layers14and16, as illustrated by the actuated display element12on the right inFIG. 7. The behavior can be the same regardless of the polarity of the applied potential difference. Though a series of display elements in an array may be referred to in some instances as “rows” or “columns,” a person having ordinary skill in the art will readily understand that referring to one direction as a “row” and another as a “column” is arbitrary. Restated, in some orientations, the rows can be considered columns, and the columns considered to be rows. In some implementations, the rows may be referred to as “common” lines and the columns may be referred to as “segment” lines, or vice versa. Furthermore, the display elements may be evenly arranged in orthogonal rows and columns (an “array”), or arranged in non-linear configurations, for example, having certain positional offsets with respect to one another (a “mosaic”). The terms “array” and “mosaic” may refer to either configuration. Thus, although the display is referred to as including an “array” or “mosaic,” the elements themselves need not be arranged orthogonally to one another, or disposed in an even distribution, in any instance, but may include arrangements having asymmetric shapes and unevenly distributed elements.

FIG. 8is a system block diagram illustrating an electronic device incorporating an IMOD-based display including a three element by three element array of IMOD display elements. The electronic device includes a processor21that may be capable of executing one or more software modules. In addition to executing an operating system, the processor21may be capable of executing one or more software applications, including a web browser, a telephone application, an email program, or any other software application.

The processor21can be capable of communicating with an array driver22. The array driver22can include a row driver circuit24and a column driver circuit26that provide signals to, for example a display array or panel30. The cross section of the IMOD display device illustrated inFIG. 7is shown by the lines1-1inFIG. 9. AlthoughFIG. 8illustrates a 3×3 array of IMOD display elements for the sake of clarity, the display array30may contain a very large number of IMOD display elements, and may have a different number of IMOD display elements in rows than in columns, and vice versa.

The details of the structure of IMOD displays and display elements may vary widely.FIGS. 9A-9Eare cross-sectional illustrations of varying implementations of IMOD display elements.FIG. 9Ais a cross-sectional illustration of an IMOD display element, where a strip of metal material is deposited on supports18extending generally orthogonally from the substrate20forming the movable reflective layer14. InFIG. 9B, the movable reflective layer14of each IMOD display element is generally square or rectangular in shape and attached to supports at or near the corners, on tethers32. InFIG. 9C, the movable reflective layer14is generally square or rectangular in shape and suspended from a deformable layer34, which may include a flexible metal. The deformable layer34can connect, directly or indirectly, to the substrate20around the perimeter of the movable reflective layer14. These connections are herein referred to as implementations of “integrated” supports or support posts18. The implementation shown inFIG. 9Chas additional benefits deriving from the decoupling of the optical functions of the movable reflective layer14from its mechanical functions, the latter of which are carried out by the deformable layer34. This decoupling allows the structural design and materials used for the movable reflective layer14and those used for the deformable layer34to be optimized independently of one another.

FIG. 9Dis another cross-sectional illustration of an IMOD display element, where the movable reflective layer14includes a reflective sub-layer14a. The movable reflective layer14rests on a support structure, such as support posts18. The support posts18provide separation of the movable reflective layer14from the lower stationary electrode, which can be part of the optical stack16in the illustrated IMOD display element. For example, a gap19is formed between the movable reflective layer14and the optical stack16, when the movable reflective layer14is in a relaxed position. The movable reflective layer14also can include a conductive layer14c, which may be configured to serve as an electrode, and a support layer14b. In this example, the conductive layer14cis disposed on one side of the support layer14b, distal from the substrate20, and the reflective sub-layer14ais disposed on the other side of the support layer14b, proximal to the substrate20. In some implementations, the reflective sub-layer14acan be conductive and can be disposed between the support layer14band the optical stack16. The support layer14bcan include one or more layers of a dielectric material, for example, silicon oxynitride (SiON) or silicon dioxide (SiO2). In some implementations, the support layer14bcan be a stack of layers, such as, for example, a SiO2/SiON/SiO2tri-layer stack. Either or both of the reflective sub-layer14aand the conductive layer14ccan include, for example, an aluminum (Al) alloy with about 0.5% copper (Cu), or another reflective metallic material. Employing conductive layers14aand14cabove and below the dielectric support layer14bcan balance stresses and provide enhanced conduction. In some implementations, the reflective sub-layer14aand the conductive layer14ccan be formed of different materials for a variety of design purposes, such as achieving specific stress profiles within the movable reflective layer14.

As illustrated inFIG. 9D, some implementations also can include a black mask structure23, or dark film layers. The black mask structure23can be formed in optically inactive regions (such as between display elements or under the support posts18) to absorb ambient or stray light. The black mask structure23also can improve the optical properties of a display device by inhibiting light from being reflected from or transmitted through inactive portions of the display, thereby increasing the contrast ratio. Additionally, at least some portions of the black mask structure23can be conductive and be configured to function as an electrical bussing layer. In some implementations, the row electrodes can be connected to the black mask structure23to reduce the resistance of the connected row electrode. The black mask structure23can be formed using a variety of methods, including deposition and patterning techniques. The black mask structure23can include one or more layers. In some implementations, the black mask structure23can be an etalon or interferometric stack structure. For example, in some implementations, the interferometric stack black mask structure23includes a molybdenum-chromium (MoCr) layer that serves as an optical absorber, an SiO2layer, and an aluminum alloy that serves as a reflector and a bussing layer, with a thickness in the range of about 30-80 Å, 500-1000 Å, and 500-6000 Å, respectively. The one or more layers can be patterned using a variety of techniques, including photolithography and dry etching, including, for example, tetrafluoromethane (or carbon tetrafluoride, CFO and/or oxygen (O2) for the MoCr and SiO2layers and chlorine (Cl2) and/or boron trichloride (BCl3) for the aluminum alloy layer. In such interferometric stack black mask structures23, the conductive absorbers can be used to transmit or bus signals between lower, stationary electrodes in the optical stack16of each row or column. In some implementations, a spacer layer35can serve to generally electrically isolate electrodes (or conductors) in the optical stack16(such as the absorber layer16a) from the conductive layers in the black mask structure23.

FIG. 9Eis another cross-sectional illustration of an IMOD display element, where the movable reflective layer14is self-supporting. WhileFIG. 9Dillustrates support posts18that are structurally and/or materially distinct from the movable reflective layer14, the implementation ofFIG. 9Eincludes support posts that are integrated with the movable reflective layer14. In such an implementation, the movable reflective layer14contacts the underlying optical stack16at multiple locations, and the curvature of the movable reflective layer14provides sufficient support that the movable reflective layer14returns to the unactuated position ofFIG. 9Ewhen the voltage across the IMOD display element is insufficient to cause actuation. In this way, the portion of the movable reflective layer14that curves or bends down to contact the substrate or optical stack16may be considered an “integrated” support post. One implementation of the optical stack16, which may contain a plurality of several different layers, is shown here for clarity including an optical absorber16a, and a dielectric16b. In some implementations, the optical absorber16amay serve both as a stationary electrode and as a partially reflective layer. In some implementations, the optical absorber16acan be an order of magnitude thinner than the movable reflective layer14. In some implementations, the optical absorber16ais thinner than the reflective sub-layer14a.

In implementations such as those shown inFIGS. 9A-9E, the IMOD display elements form a part of a direct-view device, in which images can be viewed from the front side of the transparent substrate20, which in this example is the side opposite to that upon which the IMOD display elements are formed. In these implementations, the back portions of the device (that is, any portion of the display device behind the movable reflective layer14, including, for example, the deformable layer34illustrated inFIG. 9C) can be configured and operated upon without impacting or negatively affecting the image quality of the display device, because the reflective layer14optically shields those portions of the device. For example, in some implementations a bus structure (not illustrated) can be included behind the movable reflective layer14that provides the ability to separate the optical properties of the modulator from the electromechanical properties of the modulator, such as voltage addressing and the movements that result from such addressing.

FIG. 10is a flow diagram illustrating a manufacturing process80for an IMOD display or display element.FIGS. 11A-11Eare cross-sectional illustrations of various stages in the manufacturing process80for making an IMOD display or display element. In some implementations, the manufacturing process80can be implemented to manufacture one or more EMS devices, such as IMOD displays or display elements. The manufacture of such an EMS device also can include other blocks not shown inFIG. 10. The process80begins at block82with the formation of the optical stack16over the substrate20.FIG. 11Aillustrates such an optical stack16formed over the substrate20. The substrate20may be a transparent substrate such as glass or plastic such as the materials discussed above with respect toFIG. 7. The substrate20may be flexible or relatively stiff and unbending, and may have been subjected to prior preparation processes, such as cleaning, to facilitate efficient formation of the optical stack16. As discussed above, the optical stack16can be electrically conductive, partially transparent, partially reflective, and partially absorptive, and may be fabricated, for example, by depositing one or more layers having the desired properties onto the transparent substrate20.

InFIG. 11A, the optical stack16includes a multilayer structure having sub-layers16aand16b, although more or fewer sub-layers may be included in some other implementations. In some implementations, one of the sub-layers16aand16bcan be configured with both optically absorptive and electrically conductive properties, such as the combined conductor/absorber sub-layer16a. In some implementations, one of the sub-layers16aand16bcan include molybdenum-chromium (molychrome or MoCr), or other materials with a suitable complex refractive index. Additionally, one or more of the sub-layers16aand16bcan be patterned into parallel strips, and may form row electrodes in a display device. Such patterning can be performed by a masking and etching process or another suitable process known in the art. In some implementations, one of the sub-layers16aand16bcan be an insulating or dielectric layer, such as an upper sub-layer16bthat is deposited over one or more underlying metal and/or oxide layers (such as one or more reflective and/or conductive layers). In addition, the optical stack16can be patterned into individual and parallel strips that form the rows of the display. In some implementations, at least one of the sub-layers of the optical stack, such as the optically absorptive layer, may be quite thin (e.g., relative to other layers depicted in this disclosure), even though the sub-layers16aand16bare shown somewhat thick inFIGS. 11A-11E.

The process80continues at block84with the formation of a sacrificial layer25over the optical stack16. Because the sacrificial layer25is later removed (see block90) to form the cavity19, the sacrificial layer25is not shown in the resulting IMOD display elements.FIG. 11Billustrates a partially fabricated device including a sacrificial layer25formed over the optical stack16. The formation of the sacrificial layer25over the optical stack16may include deposition of a xenon difluoride (XeF2)-etchable material such as molybdenum (Mo) or amorphous silicon (Si), in a thickness selected to provide, after subsequent removal, a gap or cavity19(see alsoFIG. 11E) having a desired design size. Deposition of the sacrificial material may be carried out using deposition techniques such as physical vapor deposition (PVD, which includes many different techniques, such as sputtering), plasma-enhanced chemical vapor deposition (PECVD), thermal chemical vapor deposition (thermal CVD), or spin-coating.

The process80continues at block86with the formation of a support structure such as a support post18. The formation of the support post18may include patterning the sacrificial layer25to form a support structure aperture, then depositing a material (such as a polymer or an inorganic material, like silicon oxide) into the aperture to form the support post18, using a deposition method such as PVD, PECVD, thermal CVD, or spin-coating. In some implementations, the support structure aperture formed in the sacrificial layer can extend through both the sacrificial layer25and the optical stack16to the underlying substrate20, so that the lower end of the support post18contacts the substrate20. Alternatively, as depicted inFIG. 11C, the aperture formed in the sacrificial layer25can extend through the sacrificial layer25, but not through the optical stack16. For example,FIG. 11Eillustrates the lower ends of the support posts18in contact with an upper surface of the optical stack16. The support post18, or other support structures, may be formed by depositing a layer of support structure material over the sacrificial layer25and patterning portions of the support structure material located away from apertures in the sacrificial layer25. The support structures may be located within the apertures, as illustrated inFIG. 11C, but also can extend at least partially over a portion of the sacrificial layer25. As noted above, the patterning of the sacrificial layer25and/or the support posts18can be performed by a masking and etching process, but also may be performed by alternative patterning methods.

The process80continues at block88with the formation of a movable reflective layer or membrane such as the movable reflective layer14illustrated inFIG. 11D. The movable reflective layer14may be formed by employing one or more deposition steps, including, for example, reflective layer (such as aluminum, aluminum alloy, or other reflective materials) deposition, along with one or more patterning, masking and/or etching steps. The movable reflective layer14can be patterned into individual and parallel strips that form, for example, the columns of the display. The movable reflective layer14can be electrically conductive, and referred to as an electrically conductive layer. In some implementations, the movable reflective layer14may include a plurality of sub-layers14a,14band14cas shown inFIG. 11D. In some implementations, one or more of the sub-layers, such as sub-layers14aand14c, may include highly reflective sub-layers selected for their optical properties, and another sub-layer14bmay include a mechanical sub-layer selected for its mechanical properties. In some implementations, the mechanical sub-layer may include a dielectric material. Since the sacrificial layer25is still present in the partially fabricated IMOD display element formed at block88, the movable reflective layer14is typically not movable at this stage. A partially fabricated IMOD display element that contains a sacrificial layer25also may be referred to herein as an “unreleased” IMOD.

The process80continues at block90with the formation of a cavity19. The cavity19may be formed by exposing the sacrificial material25(deposited at block84) to an etchant. For example, an etchable sacrificial material such as Mo or amorphous Si may be removed by dry chemical etching by exposing the sacrificial layer25to a gaseous or vaporous etchant, such as vapors derived from solid XeF2for a period of time that is effective to remove the desired amount of material. The sacrificial material is typically selectively removed relative to the structures surrounding the cavity19. Other etching methods, such as wet etching and/or plasma etching, also may be used. Since the sacrificial layer25is removed during block90, the movable reflective layer14is typically movable after this stage. After removal of the sacrificial material25, the resulting fully or partially fabricated IMOD display element may be referred to herein as a “released” IMOD.

FIGS. 12A and 12Bshow examples of system block diagrams illustrating a display device that includes a diffuser stack as described herein. The display device40can be, for example, a cellular or mobile telephone. However, the same components of the display device40or slight variations thereof are also illustrative of various types of display devices such as televisions, computers, tablets, e-readers, hand-held devices and portable media devices.

The display device40includes a housing41, a display30, a diffuser stack100, an antenna43, a speaker45, an input device48and a microphone46. The housing41can be formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing41may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber and ceramic, or a combination thereof. The housing41can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

The display30may be any of a variety of displays, including a bi-stable or analog display, as described herein. The display30also can include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display30can include an IMOD-based display, as described herein.

The components of the display device40are schematically illustrated inFIG. 12B. The display device40includes a housing41and can include additional components at least partially enclosed therein. For example, the display device40includes a network interface27that includes an antenna43which can be coupled to a transceiver47. The network interface27may be a source for image data that could be displayed on the display device40. Accordingly, the network interface27is one example of an image source module, but the processor21and the input device48also may serve as an image source module. The transceiver47is connected to a processor21, which is connected to conditioning hardware52. The conditioning hardware52may be capable of conditioning a signal (such as filter or otherwise manipulate a signal). The conditioning hardware52can be connected to a speaker45and a microphone46. The processor21also can be connected to an input device48and a driver controller29. The driver controller29can be coupled to a frame buffer28, and to an array driver22, which in turn can be coupled to a display array30. One or more elements in the display device40, including elements not specifically depicted inFIG. 12B, can be capable of functioning as a memory device and be capable of communicating with the processor21. In some implementations, a power supply50can provide power to substantially all components in the particular display device40design.

In this example, the display device40also includes a diffuser stack100. In this example, the diffuser stack100includes a low-index film and a high-index film. In this implementation, an interface between the low-index film and the high-index film includes an array of microlenses of substantially randomized sizes.

The network interface27includes the antenna43and the transceiver47so that the display device40can communicate with one or more devices over a network. The network interface27also may have some processing capabilities to relieve, for example, data processing requirements of the processor21. The antenna43can transmit and receive signals. In some implementations, the antenna43transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, and further implementations thereof. In some other implementations, the antenna43transmits and receives RF signals according to the Bluetooth® standard. In the case of a cellular telephone, the antenna43can be designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G, 4G or 5G technology. The transceiver47can pre-process the signals received from the antenna43so that they may be received by and further manipulated by the processor21. The transceiver47also can process signals received from the processor21so that they may be transmitted from the display device40via the antenna43.

In some implementations, the transceiver47can be replaced by a receiver. In addition, in some implementations, the network interface27can be replaced by an image source, which can store or generate image data to be sent to the processor21. The processor21can control the overall operation of the display device40. The processor21receives data, such as compressed image data from the network interface27or an image source, and processes the data into raw image data or into a format that can be readily processed into raw image data. The processor21can send the processed data to the driver controller29or to the frame buffer28for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation and gray-scale level.

The processor21can include a microcontroller, CPU, or logic unit to control operation of the display device40. The conditioning hardware52may include amplifiers and filters for transmitting signals to the speaker45, and for receiving signals from the microphone46. The conditioning hardware52may be discrete components within the display device40, or may be incorporated within the processor21or other components.

The driver controller29can take the raw image data generated by the processor21either directly from the processor21or from the frame buffer28and can re-format the raw image data appropriately for high speed transmission to the array driver22. In some implementations, the driver controller29can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array30. Then the driver controller29sends the formatted information to the array driver22. Although a driver controller29, such as an LCD controller, is often associated with the system processor21as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor21as hardware, embedded in the processor21as software, or fully integrated in hardware with the array driver22.

The array driver22can receive the formatted information from the driver controller29and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display's x-y matrix of display elements.

In some implementations, the driver controller29, the array driver22, and the display array30are appropriate for any of the types of displays described herein. For example, the driver controller29can be a conventional display controller or a bi-stable display controller (such as an IMOD display element controller). Additionally, the array driver22can be a conventional driver or a bi-stable display driver (such as an IMOD display element driver). Moreover, the display array30can be a conventional display array or a bi-stable display array (such as a display including an array of IMOD display elements). In some implementations, the driver controller29can be integrated with the array driver22. Such an implementation can be useful in highly integrated systems, for example, mobile phones, portable-electronic devices, watches or small-area displays.

In some implementations, the input device48can be capable of allowing, for example, a user to control the operation of the display device40. The input device48can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, a touch-sensitive screen integrated with the display array30, or a pressure- or heat-sensitive membrane. The microphone46can be capable of functioning as an input device for the display device40. In some implementations, voice commands through the microphone46can be used for controlling operations of the display device40.

The power supply50can include a variety of energy storage devices. For example, the power supply50can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. In implementations using a rechargeable battery, the rechargeable battery may be chargeable using power coming from, for example, a wall socket or a photovoltaic device or array. Alternatively, the rechargeable battery can be wirelessly chargeable. The power supply50also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply50also can be capable of receiving power from a wall outlet.

In some implementations, control programmability resides in the driver controller29which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver22. The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.

Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the IMOD (or any other device) as implemented.