HK1088076A - Display device having an array of spatial light modulators with integrated color filters - Google Patents

Abstract

By selectively placing color filters with different transmittance spectrums on an array of modulator elements each having the same reflectance spectrum, a resultant reflectance spectrum for each modulator element and it's respective color filter is created. In one embodiment, the modulator elements in an array are manufactured by the same process so that each modulator element has a reflectance spectrum that includes multiple reflectivity lines. Color filters corresponding to multiple colors, such as red, green, and blue, for example, may be selectively associated with these modulator elements in order to filter out a desired wavelength range for each modulator element and provide a multiple color array. Because the modulator elements are manufactured by the same process, each of the modulator elements is substantially the same and common voltage levels may be used to activate and deactivate selected modulation.

Description

Display device with spatial light modulator array with integrated color filters

Technical Field

The field of the invention relates to microelectromechanical systems (MEMS), and more particularly, to interferometric modulators.

Background

Microelectromechanical Systems (MEMS) include micromechanical elements, actuators, and electronics. Micromechanical elements may be created using deposition, etching, 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 known as an interferometric modulator. An interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. One of the plates may comprise a stationary layer deposited on a substrate and the other plate may comprise a metal diaphragm separated from the stationary layer by an air gap. 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 performance can be exploited in improving existing products and creating new products that have not yet been developed.

Disclosure of Invention

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

Certain embodiments of the present invention provide a display device comprising an array of spatial light modulators. Each spatial light modulator is individually addressable to transition between a first state in which the modulator is substantially reflective to at least one wavelength of light and a second state in which the modulator is substantially non-reflective to the at least one wavelength of light. The display device further includes a color filter array. Each color filter is positioned such that light reflected from a corresponding spatial light modulator propagates through the color filter. Each color filter is substantially transmissive to the at least one wavelength of a corresponding spatial light modulator.

In certain embodiments, the spatial light modulator comprises an interferometric modulator comprising a fixed surface and a movable surface substantially parallel to the fixed surface. In the first state, the movable surface is spaced from the fixed surface by a first distance in a direction substantially perpendicular to the fixed surface. In the second state, the movable surface is spaced from the fixed surface in a direction substantially perpendicular to the fixed surface by a second distance different from the first distance. In certain embodiments, the first distance or the second distance is approximately zero. In some embodiments, the first distance of each spatial light modulator is substantially the same. In some embodiments, the second distance of each spatial light modulator is substantially the same. In certain embodiments, the array of spatial light modulators includes two or more subsets of spatial light modulators, the modulators of each subset having the same first distance and the same second distance.

In certain embodiments, the at least one wavelength of a spatial light modulator comprises a broadband wavelength region (e.g., white light). In certain embodiments, the at least one wavelength of a spatial light modulator comprises a narrowband wavelength region comprising two or more colors. In certain embodiments, the at least one wavelength of a spatial light modulator comprises a single color of light (e.g., red, green, or blue light). In certain embodiments, the at least one wavelength comprises primary light, while in other embodiments, the at least one wavelength comprises secondary, tertiary, quaternary, or quinary light.

An embodiment includes a device, comprising: a plurality of display elements, wherein each display element comprises a fixed surface and a movable surface configured to define a cavity therebetween, the cavity being sufficiently large that light reflected from each display element has a wavelength spectrum comprising a plurality of lines; and a color filter associated with at least one display element, wherein the color filter is configured to allow a range of wavelengths to pass through the color filter, the display area being configured to allow a user to view light passing through the color filter.

Another embodiment includes an interferometric modulator configured to output a plurality of lines in a wavelength range visible to the human eye, the modulator comprising: a partially reflective surface; a reflective surface positioned relative to the partially reflective surface such that a gap therebetween is sufficiently large that light output from the interferometric modulator has a spectrum comprising a plurality of lines; and a color filter configured to transmit only light of wavelengths within a desired range of wavelengths, wherein the color filter is arranged to receive light reflected from at least one surface such that the received light is transmitted through the color filter towards an observer.

Another embodiment includes a method of manufacturing a device, the method comprising: fabricating an array of display elements, wherein each display element comprises a fixed surface and a movable surface to define a cavity therebetween, the cavity being sufficiently large that light reflected from each display element has a reflectivity spectrum comprising a plurality of lines; fabricating a color filter, wherein the color filter is configured to allow a range of wavelengths to pass through the color filter; and coupling the color filter to at least one display element to enable a user to view light passing through the color filter.

Another embodiment includes a device comprising: a partially reflective surface; a reflective surface; a dielectric layer disposed between the partially reflective surface and the reflective surface; and a gap defined between the partially reflective surface and the reflective surface, wherein a gap distance is the distance between the partially reflective surface and the reflective surface; wherein a thickness of the dielectric layer is sufficiently small to cause interference of a large range of wavelengths of visible light to be suppressed when the modulator is in an off state such that the modulator reflects visible light, and wherein the gap distance is sufficiently large to cause destructive interference when the modulator is in an on state such that the modulator substantially inhibits reflection of visible light.

Another embodiment includes a method of making an interferometric modulator, the method comprising: manufacturing a portion of the reflective surface; fabricating a reflective surface, wherein a gap distance is defined as the distance between the partially reflective surface and the reflective surface; a dielectric layer is disposed between the partially reflective surface and the reflective surface, wherein the dielectric layer has a thickness small enough to suppress interference of a large range of wavelengths of visible light when the modulator is in an off state such that the modulator reflects visible light, and wherein the gap distance is large enough to induce destructive interference when the modulator is in an on state such that the modulator substantially inhibits reflection of visible light.

Another embodiment comprises a device comprising: an array of interferometric modulators, wherein each interferometric modulator comprises a partially reflective surface comprising a transparent conductor layer and a partially reflective layer; a reflective surface; a dielectric layer disposed between the partially reflective surface and the reflective surface; and a gap defined between the partially reflective surface and the reflective surface, wherein the size of the gap is selected such that each interferometric modulator has a reflectance spectrum comprising lines of reflectance centered at the primary green color and extending to cover at least a portion of the primary blue and the primary red colors; and at least one color filter arranged to receive light reflected from the reflective surface such that the received light is transmitted through the color filter towards an observer.

Another embodiment includes a method of manufacturing a device, the method comprising: fabricating an array of interferometric modulators, wherein each interferometric modulator comprises a partially reflective surface, a dielectric layer disposed between the partially reflective surface and the reflective surface, and a gap defined between the partially reflective surface and the reflective surface, wherein the size of the gap is selected such that each interferometric modulator has a reflectance spectrum comprising a line of reflectance centered at a primary green color and extending to cover at least a portion of the primary blue and primary red colors; and fabricating at least one color filter such that the color filter transmits light in a wavelength range selected to include at least one of: red, green, and blue wavelengths; and positioning the color filter to receive light reflected from the reflective surface such that the received light is transmitted through the color filter toward an observer.

Another embodiment includes a device comprising: a reflective surface; a partially reflective surface; a dielectric layer disposed between the partially reflective surface and the reflective surface, wherein the dielectric layer has a thickness large enough to produce reflectivity lines at approximately the primary red and secondary blue visible wavelengths when the device is in an actuated state.

Another embodiment comprises an interferometric modulator comprising: a reflective surface; a partially reflective surface, the reflective surface and the partially reflective surface being movable relative to each other so as to provide an open state and a closed state for the interferometric modulator; and a dielectric layer disposed between the partially reflective surface and the reflective surface, wherein a thickness of the dielectric layer is sufficiently large to produce reflectivity lines at about 370 nanometers and about 730 nanometers when the modulator is in an off state.

Another embodiment comprises an interferometric modulator comprising: means for partially reflecting light; means for reflecting light, wherein the means for partially reflecting light and the means for reflecting light are configured to provide a reflectivity spectrum comprising a plurality of lines; and means for filtering only a desired one of the plurality of lines for viewing by the human eye.

Another embodiment includes a device comprising: means for modulating light, configured such that light reflected from said modulating means has a wavelength spectrum comprising a plurality of lines; and means for filtering only a desired one of the plurality of lines for viewing by the human eye.

Another embodiment includes a device comprising: means for interferometrically modulating light, wherein in a first state interference of a wide range of wavelengths of visible light is suppressed such that the visible light is reflected, and wherein in a second state destructive interference substantially inhibits reflection of the visible light; and means for transitioning the modulating means between the first state and a second state.

Another embodiment includes a device comprising: means for modulating light, the modulating means having a reflectance spectrum comprising a line of reflectance centered at the primary green color and extending to cover at least a portion of the primary blue and primary red colors; and means for filtering color arranged to receive light from the modulating means.

Another embodiment includes a device comprising: means for modulating light, the modulating means having first and second states, wherein in the second state light having spectral lines approximately at the primary red and secondary blue visible wavelengths is reflected; and means for transitioning the modulating means between the first state and a second state.

Another embodiment includes a method of operating a display, the method comprising: providing an array of display elements, wherein each display element comprises a fixed surface and a movable surface configured to define a cavity therebetween, the cavity being sufficiently large that light reflected from each display element has a reflectivity spectrum comprising a plurality of lines; receiving light on the array of display elements; and filtering light reflected from each display element according to a color filter disposed in an optical path of the respective display element.

Another embodiment includes a method of operating a display, the method comprising: receiving light from a light source such that the light at least partially passes through a partially reflective surface and reflects from a reflective surface, wherein an optical cavity is formed between the partially reflective surface and the reflective surface; setting a distance between the partially reflective surface and the reflective surface such that interference of a wide range of wavelengths of visible light is suppressed and visible light is reflected by the display; and resetting a distance between the partially reflective surface and the reflective surface to cause destructive interference of light within the cavity and to substantially inhibit reflection of visible light from the display.

Another embodiment includes a method of operating a display, the method comprising: reflecting light from a display comprising a switchable optically resonant cavity such that the wavelength spectrum of the reflected light comprises a spectral line centered at a primary green color and extending to cover at least a portion of the primary red and primary blue colors; and filtering the reflected light to selectively change the wavelength of light emitted from portions of the display.

Another embodiment includes a method of operating a display device comprising a plurality of resonant optical cavities, the method comprising: setting at least one of the optical cavities to a state such that light reflected from the optical cavity has spectral lines approximately at primary red and secondary blue visible wavelengths; and transforming the at least one optical cavity such that the at least one optical cavity has a different optical cavity length and a different reflectivity spectrum.

Other embodiments are possible. For example, in other embodiments, other types of light modulating elements besides interferometric modulators may be used (e.g., other types of MEMS or non-MEMS, reflective or non-reflective structures).

Drawings

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

FIG. 2 is a system block diagram illustrating one embodiment of an electronic device including 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 a schematic diagram of a set of row and column voltages that may be used to drive an interferometric modulator display.

FIG. 5A shows one exemplary frame of display data in the 3 × 3 interferometric modulator display of FIG. 2.

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

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

FIG. 6B is a cross-sectional view of an alternative embodiment of an interferometric modulator.

FIG. 6C is a cross-sectional view of another alternative embodiment of an interferometric modulator.

FIG. 7 schematically shows an interferometric modulator array having three sets of modulator elements, each set having a corresponding gap distance.

FIG. 8 schematically illustrates an embodiment of an interferometric modulator array in which substantially all modulator elements have substantially equal gap distances.

FIG. 9 is a plot of an exemplary reflectance spectrum of an interferometric modulator element having a gap distance d0 substantially equal to one micron.

10A-10D are graphs of different reflectance spectra of interferometric modulator elements compatible with embodiments described herein.

FIGS. 11A and 11B schematically show an exemplary embodiment of a display device including an array of interferometric modulator elements and a color filter array.

FIG. 12 is a graph of transmittance spectra for a set including three exemplary color filter materials compatible with embodiments described herein.

FIGS. 13A-13D are graphs of the resulting reflectance spectra generated by combining a color filter with the interferometric modulator element of FIGS. 10A-10D.

FIG. 14 schematically illustrates an interferometric modulator element having a dielectric layer compatible with the embodiments described herein.

FIG. 15 schematically illustrates another embodiment of a display device having an array of interferometric modulator elements compatible with the embodiments described herein.

16A and 16B are system block diagrams illustrating one embodiment of a visual display device comprising a plurality of interferometric modulators.

Detailed Description

By selectively placing color filters having different transmittance spectra on an array of modulator elements, each having the same reflectance spectrum, a composite reflectance spectrum of each modulator element and its corresponding color filter is formed. In one embodiment, the modulator elements in an array are fabricated using the same process such that each modulator element has a reflectance spectrum comprising a plurality of reflectance lines. Color filters corresponding to a plurality of colors (e.g., red, green, and blue) may be selectively associated with the modulator elements, for example, to filter out a desired wavelength range for each modulator element and provide a multi-color array. Since the modulator elements are manufactured using the same process, each modulator element is substantially identical and a common voltage level may be used to activate and deactivate selected modulation.

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

One interferometric modulator display embodiment comprising an interferometric MEMS display element is shown 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 the 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 certain embodiments, an interferometric modulator display comprises a row/column array of these interferometric modulators. Each interferometric modulator includes a pair of reflective layers positioned at a variable and controllable distance from each other to form a resonant optical cavity with at least one variable dimension. In one embodiment, one of the reflective layers is movable between two positions. In the first position, referred to herein as the released state, the movable layer is positioned relatively far from a fixed partially reflective layer. In the second position, the movable layer is positioned closer to the partially reflective layer. Incident light that reflects from the two layers interferes constructively or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel.

The portion of the pixel array shown in FIG. 1 includes two adjacent interferometric modulators 12a and 12 b. In the interferometric modulator 12a on the left, a movable highly reflective layer 13A is illustrated in a released position at a predetermined distance from a fixed partially reflective layer 16 a. In the interferometric modulator 12b on the right, a movable highly reflective layer 14b is illustrated in an actuated position adjacent to a fixed partially reflective layer 16 b.

The fixed layers 16a, 16b are electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more layers each of chromium and indium tin oxide on a transparent substrate 20. The layers are patterned into parallel strips and may form row electrodes in a display device, as will be described further below. The movable layers 13A, 14b may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes 16a, 16 b) deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. After the sacrificial material has been etched away, the deformable metal layers are separated from the fixed metal layers by a defined air gap 19. The deformable layers may be formed from a highly conductive and reflective material, such as aluminum, and the strips may form column electrodes in a display device.

When no voltage is applied, the cavity 19 remains between the layers 13A, 16a and the deformable layer is in a mechanically relaxed state as shown by the pixel 12a in FIG. 1. However, after application of a potential difference to a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the voltage is high enough, the movable layer deforms and is forced against the fixed layer (a dielectric material (not shown in this figure) may be deposited over the fixed layer to prevent shorting and control the separation distance), as shown in the right pixel 12b in FIG. 1. The behavior is the same regardless of the polarity of the applied potential difference. It can thus be seen that 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.

Fig. 2-5B 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 embody aspects of the invention. In the exemplary embodiment, the electronic device includes a processor 21, which may be any general purpose single-or multi-chip microprocessor such as an ARM, Pentium *, Pentium II *, Pentium III *, Pentium IV *, Pentium * Pro, 8051, MIPS *, Power PC *, ALPHA *, or any special purpose microprocessor such as a digital signal processor, microcontroller, or programmable gate array. As is conventional in the art, the processor 21 may be configured to execute one or more software modules. In addition to executing an operating system, the processor may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application.

In one embodiment, the processor 21 is further configured to communicate with an array controller 22. In one embodiment, the array controller 22 includes a row driver circuit 24 and a column driver circuit 26 that provide signals to a pixel array 30. The cross-sectional view of the array shown in FIG. 1 is shown by line 1-1 in FIG. 2. For MEMS interferometric modulators, the row/column actuation protocol may take advantage of the hysteresis properties of these devices shown in FIG. 3. It may require, for example, a 10 volt potential difference to cause a movable layer to deform from the released state to the actuated state. However, when the voltage is reduced from this value, the movable layer will retain its state as the voltage drops back below 10 volts. In the exemplary embodiment of FIG. 3, the movable layer does not release completely until the voltage drops below 2 volts. Thus, in the example shown in FIG. 3, there is a range of voltage, approximately 3-7 volts, within which there exists a window of applied voltage within which the device is stable in either the released 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 to apply a voltage difference of about 10 volts to the pixels to be actuated in the selected pass and a voltage difference of approximately 0 volts to the pixels to be released during row strobing. 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 shown in fig. 1 stable under the same applied voltage conditions in either an actuated or released pre-existing state. Since each pixel of the interferometric modulator, whether in the actuated or released state, is essentially a capacitor formed by the fixed and moving reflective layers, this stable state can be 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 constant.

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 thus remain in the state they were set to during the row 1 pulse. The above steps may be repeated for the entire series of rows in a sequential manner to form the frame. Typically, the frames are refreshed and/or updated with new display data by repeating the process at some desired number of frames per second. A wide variety of protocols for driving row and column electrodes of pixel arrays to produce display frames are also well known and may be used in conjunction with the present invention.

FIGS. 4, 5A and 5B illustrate one possible actuation protocol for forming a display frame on the 3 × 3 array of FIG. 2. Figure 4 shows a possible set of row and column voltage levels that may be used for pixels having the hysteresis curves of figure 3. In the embodiment of FIG. 4, actuating a pixel involves setting the appropriate column to-Vbias, and the appropriate row to + Δ V, which may correspond to-5 volts and +5 volts, respectively. Releasing a pixel is accomplished by setting the corresponding column to + Vbias, and the corresponding row to the same + deltav, thereby creating a 0 volt potential difference across the pixel. In those rows where the row voltage is held at 0 volts, the pixels are stable in the state they were originally in, regardless of whether the column is at + Vbias, or-Vbias.

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

In the frame shown in FIG. 5A, pixels (1, 1), (1, 2), (2, 2), (3, 2) and (3, 3) are activated. To accomplish this, during a "line time" for row 1, columns 1 and 2 are set to-5 volts, and column 3 is set to +5 volts. This does not change the state of any pixels, since all pixels remain within the 3-7 volt stability window. Thereafter, row 1 is strobed with a pulse that rises from 0 volts to 5 volts and then falls back to 0 volts. Thereby actuating the pixels (1, 1) and (1, 2) and releasing the pixels (1, 3). 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. Thereafter, applying the same strobe to row 2 will actuate pixel (2, 2) and release pixels (2, 1) and (2, 3). Again, no other pixels in the array are affected. Similarly, row 3 is 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 to the state shown in FIG. 5A. After writing the frame, the row potentials are 0, while the column potentials can remain at either +5 or-5 volts, and the display will be stable thereafter in the arrangement shown in FIG. 5A. It will be appreciated that the same procedure can be used for arrays consisting of tens or hundreds of rows and columns. It will also be appreciated that the timing, sequence, and levels of voltages used to perform row and column actuation can be varied widely within the general principles outlined above, and the above example is exemplary only, and any actuation voltage method can be used with the present invention.

The detailed structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example, FIGS. 6A-6C show three different embodiments of the moving mirror structure. FIG. 6A is a cross-sectional view of the embodiment of FIG. 1, wherein a strip of metal material 14 is deposited on orthogonally extending supports 18. In FIG. 6B, the moveable reflective material 14 is attached to supports at the corners only, on tethers 32. In FIG. 6C, the moveable reflective material 14 is suspended from a deformable layer 34. This embodiment has several advantages because the structural design and materials used for the reflective material 14 can be optimized with respect to the optical properties, and the structural design and materials used for the deformable layer 34 can be optimized with respect to the desired mechanical properties. The manufacture of various types of interferometric devices is described in a number of published documents, including, for example, U.S. published application 2004/0051929. The above-described structures may be fabricated using a variety of well-known techniques, including a series of material deposition, patterning, and etching steps.

The exemplary spatial light modulator array provides the ability to individually address selected modulator elements and to transition them between at least two states having different reflection and transmission characteristics. In some embodiments, each spatial light modulator of the array may be optimized to change at least one corresponding wavelength from a reflective "on" state to a non-reflective "off" state. This array of modulators can be used in pixels of an electronic display device, which can be either black and white or color.

In one embodiment, an interferometric modulator includes a fixed surface and a movable surface that is substantially parallel to the fixed surface. In the reflective "on" state, the movable surface is spaced from the fixed surface by a first distance in a direction substantially perpendicular to the fixed surface. In the non-reflective "off" state, the movable surface is spaced from the fixed surface in a direction substantially perpendicular to the fixed surface by a second distance different from the first distance.

In one embodiment, the reflective "on" state of a black and white display reflects a plurality of wavelengths that together produce visible white light, and the "off" state is substantially non-reflective for the plurality of wavelengths. For a color display, the reflective "on" state of each modulator is reflective to one or more wavelengths corresponding to a particular corresponding color (e.g., red, green, and blue).

In one embodiment, the color reflected by a modulator element in the actuated state is primarily dependent on the length of the optical path of the dielectric layer, which is approximately the thickness of the dielectric layer times the refractive index of the dielectric material. In general, the thickness of both the dielectric layer and the air gap required to obtain the desired color depends on the materials used in the fixed and movable layers. Accordingly, the thicknesses of the dielectric layers and air gaps described herein with reference to certain embodiments are merely exemplary. These thicknesses may vary depending on the material selected for the dielectric and other characteristics of the particular modulator element. Accordingly, when different dielectric materials are used in the modulator element, the optical path distance may change, and the color reflected by the modulator element may also change. In one embodiment, a fixed layer of a modulator element comprises an indium tin oxide transparent conductor layer, a chromium partially reflective layer, an aluminum reflective layer, and a dielectric stack consisting essentially of silicon dioxide.

In some embodiments of interferometric modulator arrays, a color display is made using three sets of modulator elements, each set having a different gap distance to transform a corresponding color. For example, as schematically shown in FIG. 7, an interferometric modulator array 110 for use in a color display comprises a plurality of modulator elements, each of which comprises a fixed surface 112 and a movable surface 114. A gap is defined between the fixed surface 112 and the movable surface 114, where a gap distance is the distance between the fixed surface 112 and the movable surface 114. The interferometric modulator array 110 further comprises a planarization layer 116 that provides a plane for subsequent processing of the interferometric modulator array 110.

In the embodiment shown in fig. 7, the modulator array comprises three modulator elements 120, 122, 124. Each of these modulator elements 120, 122, 124 may be configured to reflect a different color such that the combination of the three modulator elements 120, 122, 124 provides three colors. For example, modulator element 120 may be configured to reflect only a first color, modulator element 122 may be configured to reflect only a second color, and modulator element 124 may be configured to reflect only a third color. In certain embodiments, the first, second, and third colors are red, green, and blue, while in other embodiments, the first, second, and third colors are deep blue, deep red, and yellow.

In the embodiment shown in FIG. 7, the first gap distance d1 is set such that the first modulator element 120 is substantially reflective for a first color (e.g., red) and non-reflective for a second and third color. For the second modulator element 122, the distance between the movable surface 114 and the fixed surface 112 is selectively varied between a second gap distance d2 and approximately zero. In the embodiment shown in fig. 7, the second gap distance d2 is set such that the second modulator element 122 is substantially reflective for a second color (e.g., green) and non-reflective for a first and third color. For the third modulator element 124, the distance between the movable surface 114 and the fixed surface 112 is selectively switched between a third gap distance d3 and approximately zero. In the embodiment shown in FIG. 7, third gap distance d3 is set such that third modulator element 124 is substantially reflective for a third color (e.g., blue) and non-reflective for a first and second color.

As will be appreciated by those skilled in the art, the fabrication of a multi-color modulator array, such as array 110, for example, typically includes patterning a sacrificial layer using three masks to create three different gap distances (corresponding to three colors, e.g., red, green, and blue) between the fixed and movable surfaces 112, 114 of the three modulator elements 120, 122, 144. In addition, the mechanical structure of the modulator element configured with an irregular back structure increases the likelihood of misalignment and tilting of the modulator element. In addition to the complexity of manufacturing modulator elements with three different gap distances, it may be difficult to form a deeply saturated color gamut (i.e., the set of possible colors within a color system). For example, a modulator element having a gap distance set to reflect red wavelengths of light may be fabricated using additional masking steps that increase the depth of the color reflected by the modulator element. Thus, in some embodiments, the manufacturing process includes making an array of multi-color modulator elements with different gap distances, and additional steps are required to enhance the color gamut of the array.

FIG. 8 schematically illustrates an embodiment of an interferometric modulator array 1100 in which substantially all modulator elements 1110 have the same gap distance d 0. The gap distance d0 is selected to provide most of the reflection of the modulator element 1110 to a selected wavelength range in the visible portion of the spectrum. For example, in some embodiments, the gap distance d0 is approximately equal to one micron. The gap distance d0 is selected to produce a reflectance spectrum comprising a plurality of peaks.

Fig. 9 is a graph of an exemplary reflectance spectrum of a modulator element 1110, the modulator element 1110 having a gap distance d0 substantially equal to one micron. In this embodiment, the amount of light reflected by the modulator element 1110 is approximately 20-25% of the input light. In the graph shown in FIG. 9, the horizontal axis indicates the wavelength of light reflected from the example modulator element 1110, and the vertical axis indicates the percent reflectance of the example modulator element 1110. As shown in the graph of FIG. 9, the reflectance spectrum of modulator element 1110 includes three reflectance peaks at approximately 430 nanometers, 525 nanometers, and 685 nanometers. Thus, modulator element 1110 is said to have a reflectance spectrum that includes three lines of reflectance (or simply "lines"), one of which is a peak in reflectance. Specifically, the reflectance spectrum shown in fig. 9 includes a first line 910, a second line 920, and a third line 930. In other embodiments, the gap between the fixed and movable surfaces of the modulator element 1110 may be adjusted to produce more or fewer lines of reflectivity. For example, in some embodiments, the selected wavelength range includes a color range, thereby producing a plurality of reflectance lines associated with the color range. In certain embodiments, the selected wavelength range includes two or more colors, and thus the reflectance spectrum of the modulator element includes at least one line of reflectance associated with each of the two or more colors. In some embodiments, the selected wavelength range includes a selected color of light (e.g., red, green, or blue). In certain embodiments, the at least one wavelength comprises primary light, while in other embodiments, the at least one wavelength comprises light of a higher order (e.g., secondary, tertiary, quaternary, or quinary). In an embodiment, at higher order colors, such as at six levels, 3-6 reflectance peaks may be simultaneously manifested in the visible spectrum. 10A-10D are graphs of example reflectance spectra of modulator elements having varying gaps between their respective reflective and semi-reflective surfaces. Each of fig. 10A-10D shows reflectance (R) (shown on the vertical axis) as a function of wavelength (X) (shown on the horizontal axis). 10A-10D, by adjusting the gap of the modulator elements, the reflectance spectrum of the modulator elements can be adjusted to include more than one line, and the peak reflectance wavelength of the line or lines can also be adjusted.

The dashed lines in fig. 10A-10D represent a selected range of wavelengths that may be filtered, for example, by a color filter. In certain embodiments, as schematically shown in FIG. 10A, the selected wavelength range includes a generally broadband wavelength region (e.g., white light). In some embodiments, as schematically shown in FIG. 10B, the selected wavelength range includes a broadband wavelength region having a single line with a peak at a selected wavelength (e.g., primary red or primary green). In some embodiments, as schematically shown in FIG. 10C, the selected wavelength range includes a broadband wavelength region including a plurality of lines corresponding to different colors. In some embodiments, as schematically shown in FIG. 10D, the selected wavelength range includes a wavelength region having a plurality of lines corresponding to different levels of color. Other selected wavelength ranges may also be compatible with the embodiments described herein.

FIGS. 11A and 11B schematically show an exemplary embodiment of a display device 1200 that includes an array of interferometric modulator elements 1210 and an array of color filters 1220. FIG. 11A shows three modulator elements 1210A, 1210B, and 1210C and three color filters 1220A, 1220B, and 1220C. In the embodiment shown in fig. 11A and 11B, each modulator element 1210 is individually addressable to transition between a first state in which the modulator element 1210 is substantially reflective at least one wavelength and a second state in which the modulator element 1210 is substantially non-reflective at the at least one wavelength. In the embodiment schematically illustrated in FIGS. 11A and 11B, each modulator element 1210 has the same gap distance d0 such that each modulator element 1210 converts at the same at least one wavelength as the other modulator elements 1210.

Each color filter 1220 is positioned such that light reflected from a corresponding modulator element 1210 propagates through the corresponding color filter 1220. In the embodiment schematically illustrated in FIG. 11A, the color filters 1220 are positioned outside the outer surface 1230 of the array of interferometric modulator elements 1210. In the embodiment schematically shown in FIG. 11B, the color filters 1220 are positioned within the outer surface 1230 and are integral with the array of interferometric modulator elements 1210.

Each color filter 1220 has a characteristic transmittance spectrum in which a selected range of wavelengths is substantially transmitted through the color filter 1220 and other wavelengths are substantially not transmitted (e.g., reflected or absorbed) by the color filter 1220. In certain embodiments, the array of color filters 1220 comprises three subsets of color filters 1220. Each color filter 1220 in the first subset has a first transmittance spectrum, each color filter 1220 in the second subset has a second transmittance spectrum, and each color filter 1220 in the third subset has a third transmittance spectrum. In some embodiments, the first, second, and third subsets of color filters 1220 have transmittance spectra corresponding to substantial transmittance of red, green, and blue light, respectively. In certain other embodiments, the first, second, and third subsets of color filters 1220 have transmittance spectra corresponding to substantial transmittance of deep blue, deep red, and yellow light, respectively. Accordingly, by placing color filters 1220 having different transmittance spectra on modulator elements 1210, modulator elements 1210 having the same gap distance may have different reflectance spectra. Thus, by combining color filters 1220 corresponding to three colors (e.g., red/green/blue or dark blue/dark red/yellow) with modulator elements having substantially equal gap distances (e.g., the modulator elements schematically shown in FIGS. 8, 11A, and 11B), some such embodiments advantageously provide a reflectance spectrum comprising three highly saturated color lines without patterning the structure of the interferometric modulator elements. In some such embodiments, because the gap for each modulator element is substantially the same, a common voltage level may be used to activate or deactivate selected modulator elements. Thus, voltage matching between modulator elements is simplified.

In certain embodiments, color filter 1220 is combined with two or more sets of modulator elements (e.g., the modulator elements schematically shown in FIG. 7) having different gap distances, where each set of modulator elements reflects a different range of wavelengths. In some such embodiments, color filter 1220 is used to modify the reflectance spectrum of the modulator element/color filter combination (e.g., by removing undesirable tails or lines in the resulting reflectance spectrum). For example, in an embodiment in which each modulator element in a set of modulator elements has a reflective "on" state, substantially reflecting a range of wavelengths corresponding to red light but substantially non-reflective for other wavelengths, a color filter having a narrower range of transmitted red wavelengths in its transmittance spectrum may produce a more saturated red color due to the reflective "on" state of the modulator element. In some embodiments, the transmittance of the color filter is less than 100% of the wavelength substantially transmitted by the color filter. In some such embodiments, the reduction in overall display brightness caused by less than 100% transmittance of the color filter is acceptable for producing deeply saturated colors.

FIG. 12 is a graph of transmittance spectra for a set including three exemplary color filter materials compatible with embodiments described herein. An exemplary color filter material in FIG. 12 is a colored photosensitive color filter resin available from Brewer Science Specialty Materials, Inc. in Rolla, Missouri. The solid line in fig. 12 corresponds to the transmission spectrum of a PSCBlue * film having a thickness of 1.2 microns, the dashed line in fig. 12 corresponds to the transmission spectrum of a PSCGreen * film having a thickness of 1.5 microns, and the dotted line in fig. 12 corresponds to the transmission spectrum of a pscrid * film having a thickness of 1.5 microns. Any type of color filter known in the art, such as a pigment-based or interference-based multi-layer dielectric color filter, is compatible with the embodiments described herein.

The thickness of the color filter material is selected to provide the desired transmission. When used with transmissive displays, such as liquid crystal displays, in which a backlight is used to generate light that is transmitted through the display elements, the light travels through the color filter material only once. When used with a reflective display (e.g., a reflective interferometric display), light propagates through the color filter material twice: once upon incidence on the modulator element and once upon propagation away from the modulator element. Thus, the thickness of the color filter material for reflective displays is typically approximately half the thickness of the color filter material for transmissive displays. Any type of color filter known in the art, such as a pigment-based or interference-based multi-layer dielectric filter, is compatible with the embodiments described herein.

The dashed lines in fig. 10A-10D schematically show the wavelength ranges substantially transmitted by a selected color filter. Fig. 13A-13D are graphs of reflectance spectra produced by the combination of the selected color filter and modulator element 1210 corresponding to fig. 10A-10D. The reflectance spectrum produced by the combination of modulator element 1210 and the selected color filter corresponding to the reflectance spectrum shown in fig. 10A-10D corresponds to the convolution of the reflectance spectrum of modulator element 1210 and the transmittance spectrum of the color filter. The bandpass characteristics of the selected color filters allow the modulator elements 1210 to be used as individual color components of the pixels of the display device.

Referring to fig. 11A and 11B, each modulator element 1210 may have a common gap sized such that the reflectance spectrum of the modulator element 1210 includes three distinct reflectance lines, such as shown in fig. 9 and 10D. In one embodiment, each of the three lines corresponds to a red, green, or blue wavelength, respectively. Accordingly, in the absence of the color filter 1220, the modulator elements 1210 would each have a reflectance spectrum containing the three reflectance lines, and the modulator elements 1210 would each reflect white light when in the "on" state. However, after the addition of the color filter 1220, the modulator element 1210 may be modified to change its reflectance spectrum. For example, each color filter 1220 may be selected to transmit only a particular range of wavelengths, such as red, green, or blue wavelengths. Specifically, filter 1220A may be selected to transmit only a red wavelength range, filter 1220B may be selected to transmit only a green wavelength range, and filter 1220C may be selected to transmit only a blue wavelength range. Thus, after the addition of color filters 1220A-1220C, modulator elements 1210 provide different reflectance spectra, respectively. Specifically, modulator element 1210A has a single reflectance line at the blue range selected by color filter 1220A, modulator element 1210B has one reflectance line at the green range selected by color filter 1220B, and modulator element 1210C has one reflectance line at the red range selected by color filter 1220C.

In one embodiment, each modulator element includes a single color filter having a selected spectrum of transmittance. In another embodiment, a single color filter is shared by multiple modulator elements such that the outputs of the multiple modulator elements are all filtered in the same manner. In another embodiment, a single modulator element includes multiple color filters.

FIG. 14 schematically illustrates an interferometric modulator element 1300 compatible with embodiments described herein. In the embodiment shown in FIG. 14, the modulator element 1300 comprises a fixed layer 112 and a movable layer 114. In this embodiment, the fixed layer 112 includes a reflective surface on a layer that forms a partial reflector 1340. A dielectric layer 1310 is formed over the partial reflector 1340. In one embodiment, the partial reflector 1340 comprises a thin layer of chromium and the dielectric layer 1310 comprises silicon dioxide. In other embodiments, the partial reflector 1340 and the dielectric layer 1310 may comprise any other suitable materials.

In some embodiments, the material and dimensions selected for the dielectric layer 1310 will change the optical path length of the light within the modulator element 1300 and will adjust the reflectance spectrum of the modulator element 1300 accordingly. The different materials and thicknesses of the dielectric layer 1310 are compatible with the embodiments described herein. As described in more detail below, the length of the optical path of the modulator element 1300 can be adjusted by varying the thickness of the air gap. Alternatively, the length of the optical path may be changed by changing the thickness or material of the dielectric layer 1310.

In one embodiment, the dimensions of the dielectric layer of the modulator elements are selected such that when the modulator is in the closed position, light incident on the modulator elements destructively interferes and the modulator elements are seen to appear black by an observer. In such embodiments, the dielectric layer may be about 300 to 700 angstroms thick to provide the correct destructive interference when the modulator element is in the closed position.

In general, the power with which a modulator element is caused to transition between two states depends, in part, on the capacitance between the conductive portions associated with the fixed layer 112 and the movable layer 114. Thus, by reducing the gap distance, the capacitance between these surfaces is reduced, the conversion power is reduced, and the overall power consumption of a display including one or more modulator elements is reduced. In the embodiment shown in FIG. 14, the size of the dielectric layer 1310 is selected to be greater than 700 angstroms so that the gap can be reduced while maintaining the desired optical path length of the modulator element, thereby inducing destructive interference of visible light in the off state. Thus, by reducing the air gap, the power consumed by the modulator element can be reduced.

In the embodiment shown in FIG. 14, the dielectric layer 1310 has a thickness of about 2200 to 2500 angstroms that can adjust the reflectance spectrum of the modulator element 1300 in the off state to be within a wavelength range between the primary red light and the secondary blue light. This wavelength range is not truly black because it includes tails of primary red and secondary blue light, thereby producing a "deep violet" color. This deep purple color may be sufficient to mimic the black color that would be used as the black state of the pixel. However, in some embodiments, as schematically shown in FIG. 14, the modulator element 1300 includes a color filter 1320 having a tail whose transmittance spectrum does not transmit the primary red light and the secondary blue light. Such embodiments provide a non-reflective off-state for the modulator element 1300 that more closely approximates a true black color. The color filter 1320 may be further selected to transmit only a selected range of wavelengths when the modulator element 1300 is in the open state. The modulator element 1300 may also provide reduced capacitance, and thus consume less power, than a similar modulator element 1300 having a thinner dielectric.

FIG. 15 schematically illustrates a portion of another embodiment of a display device 1400, the display device 1400 including an array of interferometric modulator elements 1410 compatible with the embodiments described herein. In this embodiment, the gap distance when the modulator element is in the reflective "on" state is smaller than the gap distance when the modulator element is in the non-reflective "off" state. The modulator element 1400 includes a dielectric layer that is sufficiently thin to inhibit interference between the partially reflective layer and the fully reflective layer when the modulator element is in the "on" state, and thus reflects substantially all wavelengths of light with equal intensity. In one embodiment, the dielectric is about 100 angstroms thick. In another embodiment, the dielectric has a thickness in a range of about 50 to 200 angstroms.

In one embodiment, a gap distance d0 is set small enough that the modulator element 1400 provides near 100% visible reflectance in the reflective "on" state, which can be significantly higher than in embodiments with larger gap distances. Accordingly, some embodiments of the display device 1400 may provide a black and white display with improved reflectance. The color filter 1420 may be used to tune the color spectrum of the modulator element 1410 in the same manner as described above.

In the embodiment shown in fig. 15, the gap distance in the non-reflective "off" state is greater than d0 and is selected to not reflect a wide range of wavelengths. In particular, the gap distance is such that light destructively interferes between the fixed and movable surfaces of the modulator element 1410, resulting in substantially no light being reflected from the modulator element 1410 in the "off state. In one embodiment, the gap distance in the "off" state is in a range of about 500 to 1200 angstroms.

Certain embodiments described herein advantageously utilize a single gap distance to provide highly saturated colors among substantially all of the modulator elements of an interferometric modulator array. Certain embodiments described herein advantageously do not require special patterning or masking of the reflective layer in modulator elements configured to have red wavelength reflectivity lines. Certain embodiments advantageously provide a gap distance that is large enough to be tuned to eliminate undesirable portions of the visible spectrum. Certain embodiments advantageously provide a dielectric thickness that is sufficiently small to reflect nearly 100% of a wide range of visible wavelengths. Certain embodiments advantageously provide a low capacitance interferometric modulator structure.

16A and 16B are system block diagrams illustrating one embodiment of a display device 2040. The display device 2040 can be, for example, a cellular or mobile telephone. However, the same components of display device 2040 and slight variations thereof are also illustrative of various types of display devices such as televisions and portable media players.

The display device 2040 includes a housing 2041, a display 2030, an antenna 2043, a speaker 2045, an input device 2048, and a microphone 2046. The housing 2041 is typically made by any of a number of manufacturing processes well known to those skilled in the art, including injection molding and vacuum forming. Further, the housing 2041 may be made from any of a wide variety of materials, including but not limited to plastic, metal, glass, rubber, and ceramic, or a combination thereof. In one embodiment, the housing 2041 includes removable portions (not shown) that can be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

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

FIG. 16B schematically shows components in an embodiment of an exemplary display device 2040. The exemplary display device 2040 shown includes a housing 2041 and can include other components at least partially enclosed therein. For example, in one embodiment, the exemplary display device 2040 includes a network interface 2027, the network interface 2027 including an antenna 2043 coupled to a transceiver 2047. The transceiver 2047 is connected to the processor 2021, which processor 2021 is in turn connected to conditioning hardware 2052. Conditioning hardware 2052 may be configured to condition (e.g., filter) a signal. Conditioning hardware 2052 is coupled to a speaker 2045 and a microphone 2046. The processor 2021 is also connected to an input device 2048 and a driver controller 2029. The driver controller 2029 is coupled to a frame buffer 2028 and to the array driver 2022, which in turn is coupled to a display array 2030. A power supply 2050 provides power to all components as required by the design of the particular exemplary display device 2040.

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

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

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

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

The driver controller 2029 receives raw image data generated by the processor 2021 either directly from the processor 2021 or from the frame buffer 2028 and reformats the raw image data appropriately for high speed transmission to the array driver 2022. In particular, the driver controller 2029 reformats the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning the display array 2030. The driver controller 2029 then sends the formatted information to the array driver 2022. Although a driver controller 2029, such as an LCD controller, is typically associated with the system processor 2021 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in a number of ways. They may be embedded in the processor 2021 as hardware, embedded in the processor 2021 as software, or fully integrated in hardware with the array driver 2022.

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

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

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

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

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

Different embodiments of the invention have been described above, however, other embodiments are possible. For example, in other embodiments, other types of light modulating elements besides interferometric modulators may be used (e.g., other types of MEMS or non-MEMS, reflective or non-reflective structures).

Accordingly, while the present invention has been described with reference to specific embodiments, the description is intended to be illustrative of the invention and is not intended to be limiting of the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention.

Claims (72)

1. An apparatus, comprising:

a plurality of display elements, wherein each of the display elements comprises a fixed surface and a movable surface configured to define a cavity therebetween, the cavity being sufficiently large that light reflected from each of the display elements has a wavelength spectrum comprising a plurality of lines; and

a color filter associated with at least one of the display elements, wherein the color filter is configured to allow a range of wavelengths to pass through the color filter, the display area being configured to allow a user to view light passing through the color filter.

2. The device of claim 1, wherein the fixed surface is partially reflective and the movable surface is reflective.

3. The device of claim 1, wherein a distance between the fixed surface and the movable surface is substantially equal in each of the plurality of display elements when the display elements are in an open state.

4. The device of claim 1, wherein the distance between the fixed and movable surfaces of the display elements is large enough for light incident on each of the display elements to have a reflectivity line at red, green, and blue visible wavelengths.

5. The device of claim 4, further comprising a plurality of color filters, wherein a first set of the color filters are configured to transmit only visible light at wavelengths in the red visible light wavelengths, a second set of the color filters are configured to transmit only visible light at wavelengths in the green visible light wavelengths, and a third set of the color filters are configured to transmit only visible light at wavelengths in the blue visible light wavelengths.

6. The device of claim 1, wherein the distance between the fixed surface and the movable surface of the display elements is large enough for visible light incident on each of the display elements to have a reflectivity line in a range of about 625-740 nanometers, about 500-565 nanometers, and about 440-485 nanometers.

7. The device of claim 6, further comprising a plurality of color filters, wherein a first set of the color filters are configured to transmit only visible light at wavelengths in the range of about 625-740 nanometers, a second set of the color filters are configured to transmit only visible light at wavelengths in the range of about 500-565 nanometers, and a third set of the color filters are configured to transmit only visible light at wavelengths in the range of about 440-485 nanometers.

8. The device of claim 1, further comprising a plurality of color filters, wherein a first set of the color filters are configured to transmit only light at wavelengths in the range of about 610-630 nanometers, a second set of the color filters are configured to transmit only light at wavelengths in the range of about 530-550 nanometers, and a third set of the color filters are configured to transmit only light at wavelengths in the range of about 440-460 nanometers.

9. The device of claim 1, wherein the distance between the fixed surface and the movable surface of the display element is in a range of about 10,000 to 15,000 angstroms.

10. The device of claim 1, wherein the reflective surface of each of the plurality of display elements comprises the same material.

11. The device of claim 1, further comprising:

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

a storage device in electrical communication with the processor.

12. The device of claim 11, further comprising a drive circuit configured to send at least one signal to the plurality of display elements.

13. The device of claim 12, further comprising a controller configured to send at least a portion of the image data to the drive circuit.

14. The device of claim 11, further comprising an image source module configured to send the image data to the processor.

15. The device of claim 14, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

16. The device of claim 11, further comprising an input device configured to receive input data and to communicate the input data to the processor.

17. An interferometric modulator configured to output a plurality of lines located within a wavelength range visible to a human eye, the modulator comprising:

a partially reflective surface;

a reflective surface positioned relative to the partially reflective surface such that a gap therebetween is large enough for light output from the interferometric modulator to have a spectrum comprising a plurality of lines; and

a color filter configured to transmit only light of wavelengths within a desired range of wavelengths, wherein the color filter is arranged to receive light reflected from at least one of the surfaces such that the received light is transmitted through the color filter towards an observer.

18. The interferometric modulator of claim 17, wherein the gap between the partially reflective surface and the reflective surface is greater than about 5,000 angstroms.

19. The interferometric modulator of claim 17 in which the color filter comprises one of a red color filter, a green color filter, and a blue color filter.

20. A method of manufacturing a device, comprising:

fabricating an array of display elements, wherein each of the display elements comprises a fixed surface and a movable surface to define a cavity therebetween, the cavity being sufficiently large that light reflected from each of the display elements has a reflectivity spectrum comprising a plurality of lines;

fabricating a color filter configured to allow a range of wavelengths to pass through the color filter; and

coupling the color filter to at least one of the display elements such that a user views light passing through the color filter.

21. The method of claim 20, wherein the distance between the fixed surface and the movable surface of the display elements is large enough for light incident on each of the display elements to have a line of reflectivity at each of blue, green, and red wavelengths.

22. A device manufactured by the method of claim 20 or 21.

23. An apparatus, comprising:

a partially reflective surface;

a reflective surface;

a dielectric layer disposed between the partially reflective surface and the reflective surface; and

a gap defined between the partially reflective surface and the reflective surface, wherein gap distance is the distance between the partially reflective surface and the reflective surface;

wherein the thickness of the dielectric layer is sufficiently small such that when the modulator is in an off state, interference of visible light over a large range of wavelengths is suppressed such that the modulator reflects visible light, and wherein when the modulator is in an on state, the gap distance is sufficiently large to cause destructive interference such that the modulator substantially inhibits reflection of visible light.

24. The device of claim 23, wherein the dielectric thickness is less than about 100 angstroms.

25. The device of claim 23, further comprising a color filter.

26. The device of claim 25, wherein the color filter is configured to preferentially transmit light within a range of wavelengths, wherein the range of wavelengths is selected to include at least one of the following wavelengths: red, green, and blue wavelengths.

27. The device of claim 23, further comprising a bandpass filter that transmits white light.

28. The device of claim 23, wherein destructive interference occurs when the gap distance is in the range of about 500 to 1200 angstroms.

29. A method of making an interferometric modulator, the method comprising:

manufacturing a portion of the reflective surface;

fabricating a reflective surface, wherein a gap distance is defined as a distance between the partially reflective surface and the reflective surface;

disposing a dielectric layer between the partially reflective surface and the reflective surface, wherein the dielectric layer has a thickness small enough such that interference of visible light over a large range of wavelengths is suppressed when the modulator is in an off state such that the modulator reflects visible light, and wherein the gap distance is large enough to induce destructive interference when the modulator is in an on state such that the modulator substantially inhibits reflection of visible light.

30. An interferometric modulator manufactured by the method of claim 29.

31. An apparatus, comprising:

an array of interferometric modulators, each interferometric modulator comprising:

a partially reflective surface comprising a transparent conductor layer and a partially reflective layer;

a reflective surface;

a dielectric layer disposed between the partially reflective surface and the reflective surface; and

a gap defined between the partially reflective surface and the reflective surface, wherein the size of the gap is selected such that each interferometric modulator has a reflectance spectrum comprising lines of reflectance centered at the primary green color and extending to cover at least a portion of the primary blue and primary red colors; and

at least one color filter arranged to receive light reflected from the reflective surface such that the received light is transmitted through the color filter towards an observer.

32. The device of claim 31, wherein the dielectric layer has a thickness in a range of about 300 to 1,000 angstroms and the gap size is in a range of about 1400 to 2000 angstroms.

33. The apparatus of claim 31, wherein the at least one color filter comprises a red color filter, a blue color filter, or a green color filter.

34. The device of claim 31, wherein the at least one color filter comprises a plurality of color filters, each of the color filters being associated with at least one of the interferometric modulators.

35. The apparatus of claim 31, wherein the at least one color filter comprises a green color filter and a red color filter, wherein the green color filter is less absorptive to light than the red color filter.

36. The apparatus of claim 31, wherein said at least one color filter comprises a green color filter and a blue color filter, wherein said green color filter is less light-absorbing than said blue color filter.

37. The device of claim 31, wherein the reflectivity line is centered at about 520 nanometers.

38. The device of claim 31, wherein each interferometric modulator has a reflectance spectrum that reflects at least about 40% of light having wavelengths of about 450 nm, 520 nm, and 620 nm.

39. The device of claim 31, wherein the gap size of each interferometric modulator is about 2000 angstroms.

40. A method of manufacturing a device, the method comprising:

fabricating an array of interferometric modulators, each interferometric modulator comprising a partially reflective surface, a dielectric layer disposed between the partially reflective surface and the reflective surface, and a gap defined between the partially reflective surface and the reflective surface, wherein the size of the gap is selected such that each interferometric modulator has a reflectance spectrum comprising a line of reflectance centered at a primary green color and extending to cover at least a portion of the primary blue and the primary red colors; and

fabricating at least one color filter such that the color filter transmits light in a wavelength range selected to include at least one of the following wavelengths: red, green, and blue wavelengths; and

the color filter is positioned to receive light reflected from the reflective surface such that the received light is transmitted through the color filter toward an observer.

41. A device made by the method of claim 40.

42. An apparatus, comprising:

a reflective surface;

a partially reflective surface;

a dielectric layer disposed between the partially reflective surface and the reflective surface, wherein the dielectric layer has a thickness large enough to produce reflectivity lines at approximately the primary red and secondary blue visible wavelengths when the device is in an actuated state.

43. The device of claim 42, further comprising a color filter structure configured to transmit visible light at wavelengths in the range of about 420-650 nanometers and block the primary blue and secondary red reflectance lines so that the partially reflective surface of the interferometric modulator appears substantially black to a human eye when the interferometric modulator is in an actuated state.

44. An interferometric modulator, comprising:

a reflective surface;

a partially reflective surface, the reflective surface and the partially reflective surface being movable relative to each other so as to provide an open state and a closed state for the interferometric modulator; and

a dielectric layer disposed between the partially reflective surface and the reflective surface, the dielectric layer having a thickness large enough to produce a reflectivity line at about 370 nanometers and about 730 nanometers when the modulator is in the off state.

45. The interferometric modulator of claim 44, further comprising a color filter structure configured to transmit visible light at wavelengths in the range of about 420-650 nanometers and block the reflectivity lines at about 370 nanometers and about 730 nanometers so that the partially reflective surface of the interferometric modulator appears substantially black to a human eye when the interferometric modulator is in an actuated state.

46. The interferometric modulator of claim 45, wherein the color filter structure is further configured to generate at least one of red, green, and blue light by preferentially transmitting red, green, and blue wavelengths, respectively.

47. The interferometric modulator of claim 45, wherein the color filter structure is further configured to transmit light within a range of wavelengths, wherein the range of wavelengths is selected to include at least one of the following wavelengths: red wavelength, green wavelength, blue wavelength, and white wavelength.

48. The interferometric modulator of claim 44 in which the dielectric layer comprises an oxide film.

49. The interferometric modulator of claim 44 in which the dielectric layer has a thickness in the range of about 2200 to 2500 angstroms.

50. The interferometric modulator of claim 44 in which the distance between the reflective surface and the partially reflective surface is selected to cause the interferometric modulator to have a reflectance spectrum comprising at least three peaks at wavelengths visible to the human eye.

51. An interferometric modulator, comprising:

means for partially reflecting light;

means for reflecting light, wherein the partially reflecting means and the reflecting means are configured to provide a reflectivity spectrum comprising a plurality of lines; and

means for filtering only a desired one of the plurality of lines for viewing by a human eye.

52. An apparatus, comprising:

means for modulating light configured such that light reflected from the modulating means has a wavelength spectrum comprising a plurality of lines; and

means for filtering only a desired one of the plurality of lines for viewing by a human eye.

53. A device according to claim 52, wherein the modulating means comprises a plurality of display elements, each of the display elements comprising a fixed surface and a movable surface arranged to define a cavity therebetween, the cavity being sufficiently large that light reflected from each of the display elements has the wavelength spectrum comprising a plurality of lines.

54. The device of claim 53, wherein the filtering means comprises a color filter associated with at least one of the display elements, wherein the color filter is configured to allow a range of wavelengths to pass through the color filter, the device being configured to allow a user to view light passing through the color filter.

55. An apparatus, comprising:

means for interferometrically modulating light, wherein in a first state interference of visible light of a large wavelength range is suppressed such that the visible light is reflected, and wherein in a second state destructive interference substantially inhibits reflection of the visible light; and

means for transitioning the modulating means between the first state and the second state.

56. The apparatus of claim 55, wherein the modulating means comprises:

a partially reflective surface;

a reflective surface, said partially reflective surface and said reflective surface being movable relative to each other to provide open and closed states;

a dielectric layer disposed between the partially reflective surface and the reflective surface; and

a gap defined between the partially reflective surface and the reflective surface, wherein gap distance is the distance between the partially reflective surface and the reflective surface,

wherein the thickness of the dielectric layer is sufficiently small such that interference of visible light of a large range of wavelengths is suppressed and visible light is reflected when in the off state, and wherein the gap distance is sufficiently large to induce destructive interference to substantially inhibit reflection of visible light when in the on state.

57. The device of claim 56, wherein the transforming member comprises at least one electrode.

58. An apparatus, comprising:

means for modulating light, the modulating means having a reflectance spectrum comprising a line of reflectance centered at the primary green color and extending to cover at least a portion of the primary blue and primary red colors; and

means for filtering color arranged to receive light from the modulating means.

59. The apparatus of claim 58, wherein the modulating means comprises:

a plurality of interferometric modulators, wherein each interferometric modulator comprises:

a partially reflective surface comprising a transparent conductor layer and a partially reflective layer;

a reflective surface;

a dielectric layer disposed between the partially reflective surface and the reflective surface; and

a gap defined between the partially reflective surface and the reflective surface, wherein the size of the gap is selected such that each interferometric modulator has a reflectance spectrum that includes a line of reflectance centered at a primary green color and extending to cover at least a portion of the primary blue and primary red colors.

60. A device as claimed in claim 59, wherein the colour filtering means comprises at least one colour filter arranged to receive light reflected from the reflective surface such that the received light is transmitted through the colour filter towards an observer.

61. An apparatus, comprising:

means for modulating light, the modulating means having first and second states, wherein in the second state light having spectral lines approximately at primary red and secondary blue visible wavelengths is reflected; and

means for transitioning the modulating means between the first state and the second state.

62. The apparatus of claim 61, wherein the modulating means comprises:

a reflective surface;

a partially reflective surface; and

a dielectric layer disposed between the partially reflective surface and the reflective surface, wherein the dielectric layer has a thickness large enough to produce reflectivity lines at approximately the primary red and secondary blue visible wavelengths when the interferometric modulator is in an actuated state.

63. The device of claim 62, wherein the transforming means comprises at least one electrode.

64. The device of any one of claims 52, 55, 58, and 61, further comprising:

a processor in electrical communication with the modulating means, the processor configured to process image data;

a storage device in electrical communication with the processor.

65. The device of claim 64, further comprising:

a first controller configured to send at least one signal to the at least one display; and

a second controller configured to send at least a portion of the image data to the first controller.

66. The device of claim 65, further comprising:

an image source module configured to send the image data to the processor.

67. The device of claim 66, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

68. The device of claim 64, further comprising:

an input device configured to receive input data and to communicate the input data to the processor.

69. A method of operating a display, comprising:

providing an array of display elements, each of the display elements comprising a fixed surface and a movable surface configured to define a cavity therebetween, the cavity being sufficiently large that light reflected from each of the display elements has a reflectivity spectrum comprising a plurality of lines;

receiving a light on the array of display elements; and

light reflected from each of the display elements is filtered according to a color filter disposed in an optical path of the respective display element.

70. A method of operating a display, comprising:

receiving light from a light source such that the light at least partially passes through a partially reflective surface and reflects from a reflective surface, wherein an optical cavity is formed between the partially reflective surface and the reflective surface;

setting a distance between the partially reflective surface and the reflective surface such that interference of a large range of wavelengths of visible light is suppressed and visible light is reflected from the display; and

the distance between the partially reflective surface and the reflective surface is reset such that light within the cavity interferes destructively and visible light is substantially inhibited from reflecting from the display.

71. A method of operating a display, comprising:

reflecting light from a display comprising a switchable optically resonant cavity such that the wavelength spectrum of the reflected light comprises a spectral line centered at a primary green color and expanded to cover at least a portion of the primary blue and primary red colors; and

the reflected light is filtered to selectively change the wavelength of light emitted from portions of the display.

72. A method of operating a display device comprising a plurality of resonant optical cavities, the method comprising:

setting at least one of the optical cavities to a state such that light reflected from the optical cavity has spectral lines approximately at primary red and secondary blue visible wavelengths; and

transforming the at least one optical cavity such that the at least one optical cavity has a different optical cavity length and a different reflectivity spectrum.