Integrated front light solution

An integrated illumination apparatus includes a light injection portion having a first end for receiving light from a light source. The light injection portion includes material that supports propagation of said light along the length of the light injection portion. Turning microstructure is disposed on a first side of the light injection. The turning microstructure is configured to turn at least a substantial portion of light incident on the first side and to direct the portion of the light out a second opposite side of the light injection portion. A slit is disposed along the length of the light injection portion. The slit forms an optical interface on the second opposite side of the light injection portion that provides total internal reflection for light propagating along the length of the light injection portion to be guided therein. The optical interface further transmits light turned by said turning microstructure. A light distribution portion is disposed with respect to the slit to receive the light turned by said turning microstructure and transmitted out of the second side of the light injection portion and through said slit. At least one bridge is disposed between light injection portion and the light distribution portion. The bridge mechanically connects the light injection portion to the light distribution portion.

BACKGROUND

Microelectromechanical systems (MEMS) include micro mechanical elements, actuators, and electronics. Micromechanical elements may be created using deposition, etching, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers or that add layers to form electrical and electromechanical devices. One type of MEMS device is called an interferometric modulator. As used herein, the term interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In certain embodiments, an interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. In a particular embodiment, one plate may comprise a stationary layer deposited on a substrate and the other plate may comprise a metallic membrane separated from the stationary layer by an air gap. As described herein in more detail, the position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Such devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of these types of devices so that their features can be exploited in improving existing products and creating new products that have not yet been developed.

SUMMARY

One embodiment of the invention comprises an integrated illumination apparatus comprising: a light injection portion having a first end for receiving light from a light source, said light injection portion comprising material that supports propagation of said light along the length of the light injection portion towards a second opposite end; turning microstructure disposed on a first side of the light injection portion, the turning microstructure configured to turn at least a substantial portion of light incident on the first side and to direct the portion of the light towards a second opposite side of the light injection portion; a slit disposed along the length of the light injection portion, the slit forming an optical interface on the second opposite side of the light injection portion that provides total internal reflection for light propagating along the length of the light injection portion to be guided therein, said optical interface further transmitting light turned by said turning microstructure; a light distribution portion disposed with respect to the slit to receive the light turned by said turning microstructure and transmitted out of the second side of the light injection portion and through said slit; and at least one bridge disposed between light injection portion and the light distribution portion and mechanically connecting the light injection portion to the light distribution portion. Other embodiments are possible.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

Some embodiments include an integrated illumination apparatus comprising a light injection portion for receiving light from a light source along its length direction and propagating the light along its length direction, and a light distribution portion for receiving the light turned and transmitted from the light injection portion. The light injection portion and the light distribution portion are mechanically connected across one or more slits or openings via one or more bridges, thereby forming an integrated light injection/light distribution structure.

One interferometric modulator display embodiment comprising an interferometric MEMS display element is illustrated inFIG. 1. In these devices, the pixels are in either a bright or dark state. In the bright (“relaxed” or “open”) state, the display element reflects a large portion of incident visible light to a user. When in the dark (“actuated” 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.

The depicted portion of the pixel array inFIG. 1includes two adjacent interferometric modulators12aand12b. In the interferometric modulator12aon the left, a movable reflective layer14ais illustrated in a relaxed position at a predetermined distance from an optical stack16a, which includes a partially reflective layer. In the interferometric modulator12bon the right, the movable reflective layer14bis illustrated in an actuated position adjacent to the optical stack16b.

The optical stacks16aand16b(collectively referred to as optical stack16), as referenced herein, typically comprise several fused layers, which can include an electrode layer, such as indium tin oxide (ITO), a partially reflective layer, such as chromium, and a transparent dielectric. The optical stack16is thus electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate20. The partially reflective layer can be formed from a variety of materials that are partially reflective such as various metals, semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials.

In some embodiments, the layers of the optical stack16are patterned into parallel strips, and may form row electrodes in a display device as described further below. The movable reflective layers14a,14bmay be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of16a,16b) to form columns deposited on top of posts18and an intervening sacrificial material deposited between the posts18. When the sacrificial material is etched away, the movable reflective layers14a,14bare separated from the optical stacks16a,16bby a defined gap19. A highly conductive and reflective material such as aluminum may be used for the reflective layers14, and these strips may form column electrodes in a display device. Note thatFIG. 1may not be to scale. In some embodiments, the spacing between posts18may be on the order of 10-100 um, while the gap19may be on the order of <1000 Angstroms.

With no applied voltage, the gap19remains between the movable reflective layer14aand optical stack16a, with the movable reflective layer14ain a mechanically relaxed state, as illustrated by the pixel12ainFIG. 1. However, when a potential (voltage) difference is applied to a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the voltage is high enough, the movable reflective layer14is deformed and is forced against the optical stack16. A dielectric layer (not illustrated in this Figure) within the optical stack16may prevent shorting and control the separation distance between layers14and16, as illustrated by actuated pixel12bon the right inFIG. 1. The behavior is the same regardless of the polarity of the applied potential difference.

FIGS. 2 through 5illustrate one exemplary process and system for using an array of interferometric modulators in a display application.

FIG. 2is a system block diagram illustrating one embodiment of an electronic device that may incorporate interferometric modulators. The electronic device includes a processor21which may be any general purpose single- or multi-chip microprocessor such as an ARM®, Pentium®, 8051, MIPS®, Power PC®, or ALPHA®, or any special purpose microprocessor such as a digital signal processor, microcontroller, or a programmable gate array. As is conventional in the art, the processor21may 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 processor21is also configured to communicate with an array driver22. In one embodiment, the array driver22includes a row driver circuit24and a column driver circuit26that provide signals to a display array or panel30. The cross section of the array illustrated inFIG. 1is shown by the lines1-1inFIG. 2. Note that althoughFIG. 2illustrates a 3×3 array of interferometric modulators for the sake of clarity, the display array30may contain a very large number of interferometric modulators, and may have a different number of interferometric modulators in rows than in columns (e.g., 300 pixels per row by 190 pixels per column).

As described further below, in typical applications, a frame of an image may be created by sending a set of data signals (each having a certain voltage level) across 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 a first row electrode, actuating the pixels corresponding to the set of data signals. The set of data signals is then changed to correspond to the desired set of actuated pixels in a second row. A pulse is then applied to the second row electrode, actuating the appropriate pixels in the second row in accordance with the data signals. The first row of pixels are unaffected by the second row pulse, and remain in the state they were set to during the first row pulse. This may be repeated for the entire series of rows in a sequential fashion to produce the frame. Generally, the frames are refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second. A wide variety of protocols for driving row and column electrodes of pixel arrays to produce image frames may be used.

FIGS. 4 and 5illustrate one possible actuation protocol for creating a display frame on the 3×3 array ofFIG. 2.FIG. 4illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves ofFIG. 3. In theFIG. 4embodiment, actuating a pixel involves setting the appropriate column to −Vbias, and the appropriate row to +ΔV, which may correspond to −5 volts and +5 volts respectively Relaxing the pixel is accomplished by setting the appropriate column to +Vbias, and the appropriate row to the same +ΔV, producing a zero volt potential difference across the pixel. In those rows where the row voltage is held at zero volts, the pixels are stable in whatever state they were originally in, regardless of whether the column is at +Vbias, or −Vbias. As is also illustrated inFIG. 4, voltages of opposite polarity than those described above can be used, e.g., actuating a pixel can involve setting the appropriate column to +Vbias, and the appropriate row to −ΔV. In this embodiment, releasing the pixel is accomplished by setting the appropriate column to −Vbias, and the appropriate row to the same −ΔV, producing a zero volt potential difference across the pixel.

In theFIG. 5Aframe, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) are actuated. To accomplish this, during a “line time” for row 1, columns 1 and 2 are set to −5 volts, and column 3 is set to +5 volts. This does not change the state of any pixels, because all the pixels remain in the 3-7 volt stability window. Row 1 is then strobed with a pulse that goes from 0, up to 5 volts, and back to zero. This actuates the (1,1) and (1,2) pixels and relaxes the (1,3) pixel. No other pixels in the array are affected. To set row 2 as desired, column 2 is set to −5 volts, and columns 1 and 3 are set to +5 volts. The same strobe applied to row 2 will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again, no other pixels of the array are affected. Row 3 is similarly set by setting columns 2 and 3 to −5 volts, and column 1 to +5 volts. The row 3 strobe sets the row 3 pixels as shown inFIG. 5A. After writing the frame, the row potentials are zero, and the column potentials can remain at either +5 or −5 volts, and the display is then stable in the arrangement ofFIG. 5A. The same procedure can be employed for arrays of dozens or hundreds of rows and columns. The timing, sequence, and levels of voltages used to perform row and column actuation can be varied widely within the general principles outlined above, and the above example is exemplary only, and any actuation voltage method can be used with the systems and methods described herein.

FIGS. 6A and 6Bare system block diagrams illustrating an embodiment of a display device40. The display device40can be, for example, a cellular or mobile telephone. However, the same components of display device40or slight variations thereof are also illustrative of various types of display devices such as televisions and portable media players.

The display device40includes a housing41, a display30, an antenna43, a speaker45, an input device48, and a microphone46. The housing41is generally formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing41may be made from any of a variety of materials, including but not limited to plastic, metal, glass, rubber, and ceramic, or a combination thereof. In one embodiment the housing41includes removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

The display30of exemplary display device40may be any of a variety of displays, including a bi-stable display, as described herein. In other embodiments, the display30includes a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described above, or a non-flat-panel display, such as a CRT or other tube device. However, for purposes of describing the present embodiment, the display30includes an interferometric modulator display, as described herein.

The components of one embodiment of exemplary display device40are schematically illustrated inFIG. 6B. The illustrated exemplary display device40includes a housing41and can include additional components at least partially enclosed therein. For example, in one embodiment, the exemplary display device40includes a network interface27that includes an antenna43which is coupled to a transceiver47. The transceiver47is connected to a processor21, which is connected to conditioning hardware52. The conditioning hardware52may be configured to condition a signal (e.g. filter a signal). The conditioning hardware52is connected to a speaker45and a microphone46. The processor21is also connected to an input device48and a driver controller29. The driver controller29is coupled to a frame buffer28, and to an array driver22, which in turn is coupled to a display array30. A power supply50provides power to all components as required by the particular exemplary display device40design.

The network interface27includes the antenna43and the transceiver47so that the exemplary display device40can communicate with one ore more devices over a network. In one embodiment the network interface27may also have some processing capabilities to relieve requirements of the processor21. The antenna43is any antenna for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.11 standard, including IEEE 802.11(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS, W-CDMA, or other known signals that are used to communicate within a wireless cell phone network. The transceiver47pre-processes the signals received from the antenna43so that they may be received by and further manipulated by the processor21. The transceiver47also processes signals received from the processor21so that they may be transmitted from the exemplary display device40via the antenna43.

In an alternative embodiment, the transceiver47can be replaced by a receiver. In yet another alternative embodiment, network interface27can be replaced by an image source, which can store or generate image data to be sent to the processor21. 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.

Processor21generally controls the overall operation of the exemplary display device40. The processor21receives data, such as compressed image data from the network interface27or an image source, and processes the data into raw image data or into a format that is readily processed into raw image data. The processor21then sends the processed data to the driver controller29or to frame buffer28for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation, and gray-scale level.

In one embodiment, the processor21includes a microcontroller, CPU, or logic unit to control operation of the exemplary display device40. Conditioning hardware52generally includes amplifiers and filters for transmitting signals to the speaker45, and for receiving signals from the microphone46. Conditioning hardware52may be discrete components within the exemplary display device40, or may be incorporated within the processor21or other components.

The driver controller29takes the raw image data generated by the processor21either directly from the processor21or from the frame buffer28and reformats the raw image data appropriately for high speed transmission to the array driver22. Specifically, the driver controller29reformats the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array30. Then the driver controller29sends the formatted information to the array driver22. Although a driver controller29, such as a LCD controller, is often associated with the system processor21as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. They may be embedded in the processor21as hardware, embedded in the processor21as software, or fully integrated in hardware with the array driver22.

Typically, the array driver22receives the formatted information from the driver controller29and 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 matrix of pixels.

In one embodiment, the driver controller29, array driver22, and display array30are appropriate for any of the types of displays described herein. For example, in one embodiment, driver controller29is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, array driver22is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, a driver controller29is integrated with the array driver22. Such an embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment, display array30is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).

The input device48allows a user to control the operation of the exemplary display device40. In one embodiment, input device48includes a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a touch-sensitive screen, a pressure- or heat-sensitive membrane. In one embodiment, the microphone46is an input device for the exemplary display device40. When the microphone46is used to input data to the device, voice commands may be provided by a user for controlling operations of the exemplary display device40.

Power supply50can include a variety of energy storage devices as are well known in the art. For example, in one embodiment, power supply50is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment, power supply50is a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell, and solar-cell paint. In another embodiment, power supply50is configured to receive power from a wall outlet.

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

The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,FIGS. 7A-7Eillustrate five different embodiments of the movable reflective layer14and its supporting structures.FIG. 7Ais a cross section of the embodiment ofFIG. 1, where a strip of metal material14is deposited on orthogonally extending supports18. InFIG. 7B, the moveable reflective layer14of each interferometric modulator is square or rectangular in shape and attached to supports at the corners only, on tethers32. InFIG. 7C, the moveable reflective layer14is square or rectangular in shape and suspended from a deformable layer34, which may comprise a flexible metal. The deformable layer34connects, directly or indirectly, to the substrate20around the perimeter of the deformable layer34. These connections are herein referred to as support posts. The embodiment illustrated inFIG. 7Dhas support post plugs42upon which the deformable layer34rests. The movable reflective layer14remains suspended over the gap, as inFIGS. 7A-7C, but the deformable layer34does not form the support posts by filling holes between the deformable layer34and the optical stack16. Rather, the support posts are formed of a planarization material, which is used to form support post plugs42. The embodiment illustrated inFIG. 7Eis based on the embodiment shown inFIG. 7D, but may also be adapted to work with any of the embodiments illustrated inFIGS. 7A-7Cas well as additional embodiments not shown. In the embodiment shown inFIG. 7E, an extra layer of metal or other conductive material has been used to form a bus structure44. This allows signal routing along the back of the interferometric modulators, eliminating a number of electrodes that may otherwise have had to be formed on the substrate20.

In embodiments such as those shown inFIG. 7, the interferometric modulators function as direct-view devices, in which images are viewed from the front side of the transparent substrate20, the side opposite to that upon which the modulator is arranged. In these embodiments, the reflective layer14optically shields the portions of the interferometric modulator on the side of the reflective layer opposite the substrate20, including the deformable layer34. This allows the shielded areas to be configured and operated upon without negatively affecting the image quality. For example, such shielding allows the bus structure44inFIG. 7E, which provides the ability to separate the optical properties of the modulator from the electromechanical properties of the modulator, such as addressing and the movements that result from that addressing. This separable modulator architecture allows the structural design and materials used for the electromechanical aspects and the optical aspects of the modulator to be selected and to function independently of each other. Moreover, the embodiments shown inFIGS. 7C-7Ehave additional benefits deriving from the decoupling of the optical properties of the reflective layer14from its mechanical properties, which are carried out by the deformable layer34. This allows the structural design and materials used for the reflective layer14to be optimized with respect to the optical properties, and the structural design and materials used for the deformable layer34to be optimized with respect to desired mechanical properties.

Integrated illumination systems for providing artificial illumination for underlying modulators are disclosed herein. The integrated illumination system comprises a light source, a light injection portion, and a light distribution portion. The light injection portion transforms light from a point source (e.g., a light emitting diode (LED)) into a line source. A light injection portion having turning features may be used for this purpose. Light injected into the light injection portion propagates along the length of the bar portion and is ejected out of the bar over the length of the bar. This light is subsequently spread across a wide area and directed onto an array of display elements. A light distribution portion also having turning features thereon may be used for this purpose. The light ejected from the light injection portion is coupled into an edge of the light distribution portion and propagated within the light distribution portion. Turning features eject the light from the panel portion over an area corresponding to the plurality of display elements.

FIG. 8Ais a top view of a nonintegrated illumination system comprising separate light injection and light distribution components. The illumination system includes a light injection component101, a light distribution component80, a light source92, and a plurality of reflectors96,97. The light injection component101includes turning microstructure comprising a plurality of turning features91. The illumination system may further include one or more reflectors96,97that receive and reflect light transmitted through the sides of the light injection component101. In the illumination system, the light injection component101and the light distribution component80are separate structures. For maximum efficiency, the light injection component101and the light distribution component80are accurately aligned with respect to each other.

FIG. 8Bis a top view of an example of an integrated illumination system100comprising light injection and light distribution portions connected by bridges according to certain embodiments. The integrated illumination system100comprises a light injection portion101, a light distribution portion103, a slit105, and bridges107. The light injection portion101includes turning microstructure comprising a plurality of turning features91. In certain embodiments, the light injection portion101includes a light bar having a rectangular cross section such as the one shown inFIG. 8B. In the example embodiment, the turning features91include V or triangular-shaped grooves in the side of the light injection portion. In the example integrated illumination system, the bridges107provide a mechanical connection between the light injection portion101and the light distribution portion103. The slit105is a narrow open area surrounded on opposite sides by the light injection portion101, the light distribution portion103, and the bridges.

In certain embodiments of the integrated illumination system, the light injection portion, the light distribution portion, and the bridges comprise a monolithic structure such as a unitary film. In such embodiment, the light injection portion and the light distribution portion are contained in a single film. The illumination system may also further include one or more reflectors96,97that receive and reflect light transmitted through the sides of the light injection portion.

Various advantages are realized by use of an unitary integrated structure such as a monolithic film. The monolithic design eliminates the manufacture and inventory of separate light-bar and light-guide components. More importantly, the unitary design eliminates the precise alignment between the light-bar and light-guide components. In a non-monolithic illumination structure involving separate light injection component90and light distribution component80, such as the one shown inFIG. 8A, the light injection and the light distribution component are free to move relative to each other. For maximum efficiency, the light injection and the light distribution components are precisely positioned relative to each other. For example, the light injection component90and the light distribution component80are positioned precisely in the x-direction in order to create a slit having an optimal width. The light injection component90and the light distribution component80are also aligned precisely in the y and z directions to increase or maximize light coupling from the light injection component to the light distribution component through the slit99. In addition, for increased or maximum coupling, the thicknesses of the light injection component and the light distribution component are also precisely matched. The precise alignment/positioning and the thickness control can incur extra manufacturing costs and become extra source of product defects. In a monolithic film design such as the one shown inFIG. 8B, these problems are sufficiently avoided. The positioning/alignment and the thicknesses of the light injection and light distribution portions are precisely matched without the need of any complicated assembly process. In some monolithic film embodiments, the turning microstructures91on the light injection portion can be formed directly into an edge of the monolithic film in the same fabricating process as for the light distribution portion and the light injection portion simplifying fabrication. Formation of the turning microstructures on the edge of the monolithic film is easier compared to formation of the microstructures on an edge of a smaller, and therefore, harder to handle, separate light injection component. This is especially true if the microstructures are formed in the monolithic film before the slit105is made. Turning features on the light distribution portion103may also be formed at the same time as the slit in some embodiments and may thus simplify fabrication.

FIG. 9Ais a perspective view of a display device including an integrated illumination system100comprising a light distribution portion103disposed with respect to a display substrate comprising a plurality of display elements81. The integrated illumination system100includes a light injection portion101, a light distribution portion103, a slit105, and bridges107. The light injection portion101has a first end101afor receiving light from a light emitter92, a second opposite edge101d, a first side101b, and a second opposite side101c. The light emitter92may comprise a light emitting diode (LED), although other light sources are also possible. The light injection portion101comprises substantially optically transmissive material that supports propagation of light from the emitter along the length of the light injection portion101. The light distribution portion103includes a first side103aand a second opposite side103b.

As discussed above, in certain embodiments of the integrated illumination system, the light injection portion, the light distribution portion, and the bridges comprise a monolithic structure such as a unitary film. Such unitary film can be laminated to a display substrate including a plurality of display elements81. The display elements81may be on the other side of the display substrate as the integrated illumination system. In the area directly beneath the light injection portion101of the film, a refractive index mismatch may be generated between the film and the display substrate in order to aid total internal reflection (TIR) with the film having the larger of the two indices. Alternatively, this portion of the film may not contain any adhesive and light guiding, e.g., TIR, relies on the presence of a small air gap. Such small gap typically exits when one material is resting on top of another.

In operation, the light emitted from the light emitter92propagates into the light injection portion101. The light is guided therein, for example, via total internal reflection at sides101band101cthereof, which form optical interfaces with air or some other surrounding medium. In various embodiments, this surrounding medium may comprise air or gas. This surrounding medium may alternatively comprise solid or liquid. Accordingly, this medium may be fluid. Light travels from the first end101ato a second end101dof the light injection portion101. A substantial portion of the light traveling along the light injection portion gets turned by the turning microstructure towards the second opposite side101cof the light injection portion101at an angle less than a critical angle. The slit105is disposed along the length of the light injection portion and forms an optical interface on the second opposite side101cof the light injection portion101that provides total internal reflection for light propagating along the length of the light injection portion to be guided therein. The optical interface further transmits at least some of the light turned by the turning microstructure and incident on the interface at an angle greater than the critical angle. The light distribution portion103is disposed with respect to the light injection portion101so as to receive through the first side103athe light injected from the light injection portion101, e.g., the light that has been turned by the turning microstructure and directed out of the light injection portion101and through the slit105. The light distribution portion103is configured to receive the light injected from the light injection portion101and distribute the received light onto a plurality of display elements81. In certain embodiments, the light distribution portion103includes turning microstructures109(FIG. 9B) that reflect light from the light injection portion101into the plurality of display elements81(e.g., a plurality of spatial light modulators, interferometric modulators, liquid crystal elements, etc.) as described above.

The turning microstructure of the light injection portion101comprises a plurality of turning features91having facets91a(which may be referred to as faceted turning features or faceted features), as can be seen inFIG. 9A. The features91shown inFIG. 9Aare schematic and exaggerated in size and spacing therebetween. As illustrated, the turning microstructure is integrated with the light injection portion101. For example, the light injection portion101may be molded with the turning features91formed therein by molding. Alternatively, the turning microstructures may be formed by cutting the light injection portion or by other methods. In certain embodiments, some or all of the faceted features91of the turning microstructure could be formed in a film that is formed on, or laminated to, the light injection portion101.

The facets91aor sloping surfaces are configured to direct or scatter light out of the light injection portion101towards the light distribution portion103. Light may, for example, reflect by total internal reflection from a portion91bof the sidewall of the light injection portion101parallel to the length of the light injection portion101to one of the sloping surfaces91a. This light may reflect from the sloping surface91ain a direction toward the light distribution portion103. (See alsoFIG. 10B) In the embodiment illustrated inFIG. 9B, the turning microstructure comprises a plurality of grooves. Specifically, the turning microstructure comprises a plurality of triangular grooves having substantially triangular cross-sections. The triangular grooves illustrated inFIG. 9Bhave cross-sections with the shape of an isosceles triangle, although other shapes are also possible. The orientation of the sides91acan affect the distribution of light exiting the light injection portion101and entering the light distribution portion103. Other shapes may be used.

In some embodiments, the turning microstructure has a parameter that changes with distance, d, from the first end101aof the light injection portion101and/or the light source92. In some embodiments, the parameter of the microstructure that changes with distance, d, from the first end101aof the light injection portion101and/or the light source92is size, shape, density, spacing, position, etc. In certain such embodiments, the turning microstructure has a size that, on average, increases with distance, d, from the light source92. For example, the turning microstructure in some embodiments has a width (e.g., parallel to y-axis) that, on average, increases with distance, d, from the light source92. In another example, the turning microstructure in some embodiments has a depth (e.g., parallel to the x axis) that, on average, increases with distance, d, from the light source92. The turning features91illustrated inFIG. 9Aincrease in both depth and width, while the angles of the facets91aor sloping sidewalls remain substantially constant. In some embodiments, one or more other parameters of the turning microstructure may change, such as shape and angle.

In certain embodiments, the turning microstructure has a density, ρ, of turning features91that remains substantially the same with distance, d, from the light source. For example, inFIG. 9Bthe plurality of triangular grooves91are approximately equally spaced from each other. In certain other embodiments, the turning microstructure has a density, ρ, that increases with distance, d, from the first end101aof the light injection portion101and/or the light source92. For example, the turning microstructure in some embodiments has a spacing (e.g., along the y-axis) that, on average, increases with distance, d, from the first end101aof the light injection portion101and/or the light source92.

In some embodiments, the light injection portion101has a turning efficiency that determines the amount of light turned out of the light injection portion101compared to the amount of light that continues to be guided within the light injection portion101. For example, the turning efficiency can increase with an increasing density of turning microstructures. In certain such embodiments, the microstructure density and, therefore, the turning efficiency increase with distance, d, from the first end101aof the light injection portion101and/or the light source92.

In certain embodiments, the slit105runs nearly across the entire length of the integrated illumination system (e.g., along y direction), thereby forming relatively narrow bridges107as shown inFIG. 9B. In some embodiments, the length of the slit is between 90 percent and 100 percent of the length of the light injection portion101(e.g., in y direction). In some embodiments, the width of the slit (e.g., in x direction) is less than 5% of the length of the slit (e.g., in y direction). The width of the slit can be between 1 μm and 10 mm, and preferably between 50 μm and 200 μm. The width of the slit is related to coupling efficiency. In general, smaller the slit width is, the higher the coupling efficiency is. In some embodiments, the width of the slit is determined by the ease of cutting the slit and the need to reduce overall width (e.g., x dimension) of the integrated illumination system. The slit can be manufactured by a variety of methods, including die-cutting, molding, embossing, and the like.

In certain embodiments, the slit is not placed too close to the first side101b. As the distance between the slit and the faceted first side101bof the light injection portion decreases, light into the x-y plane more frequently strikes the facets. This fact is taken into account in the facet and slit designs. Also, the width (x-direction) of the light injection portion101needs to be large enough to capture light from the light source92. In certain embodiments, the second opposite side101cof the light injection portion101forming a first side wall of the slit105is positioned substantially aligned with one side of the light source92as shown inFIG. 9A. In certain other embodiments, the first side103aof the light distribution portion103forming a second side wall of the slit is positioned substantially aligned with one edge of the module forming the display elements81as shown inFIG. 9A. In certain embodiments, the slit is symmetrically positioned in the length (e.g., y) direction such that the widths of the bridges are substantially the same as shown inFIG. 9A. In other embodiments, it may be advantageous to asymmetrically position the slit so as to provide a wider bridge at the edge opposite to the light source. This design allows more light to enter the typically dim region of the light distribution portion close to the opposite edge.

In certain embodiments, the slit may comprise an opening filled with air, gases, or liquid, e.g. adhesive flowed into at least part of the slit. In various such embodiments, however, the light injection portion101and the slit105form a high-index to low-index interface. In some embodiments, the high-index to low-index interface comprises a plastic/air interface. The shape of the slit is shown as rectangular but may differ. The slit may include flat parallel sides such as shown. In certain other embodiments, the slit may include one or more performance-enhancing features formed on the sides to control the direction of transmitted light, for example. Such performance-enhancing features formed on side walls of a slit are described in detail below with reference toFIG. 12AtoFIG. 12D.

In certain embodiments, the bridges107are narrow portions remaining after the slit is formed nearly across the entire length of the integrated illumination system as shown inFIG. 9A. In some of such embodiments, the width (y-direction) of the bridge is less than 5% of the length of the light injection portion101. The width of the bridge is preferably between 1% and 50% of the length of the light injection portion101. The width of the bridge is preferably between 1 mm and 20 mm. The number of bridges is preferably 2 but can range from 1 to 10. In some embodiments, the length of the slit extends (e.g., in y-direction) slightly (e.g., less than 5 mm) beyond the size of the active area of the display and the first side103aof the light distribution portion103is disposed (e.g., in x-direction) slightly (e.g., less than 5 mm) outside the active area of the display, such that the bridges thereby formed are placed outside the active area of the display. As used herein, the “active area” refers to the part of the display substrate containing the display elements81. Various methods of manufacturing the slit, therefore also of bridges, are described above. In some embodiments, the bridges107are disposed proximal to the first end101aand the second opposite end101dof the light injection portion101. In some embodiments, one or more bridges are disposed proximal to the center between the first end101aand the second opposite end101dof the light injection portion101. In certain embodiments, one or more bridges may have a thickness that is different from the thickness of the light injection portion101and/or the light distribution portion103. For example, the thickness of the bridge may be only 50% of the thickness of the light injection and the light distribution portions. In certain embodiments, the bridge may comprise the same material as the light injection portion and the light distribution portion. In some embodiments, the bridges comprise substantially optically transmissive material.

FIG. 9Bis a side cross-sectional view of a display device including an integrated illumination system100comprising a light distribution portion103disposed with respect to a plurality of display elements81. The integrated illumination system100includes a light injection portion101, a light distribution portion103, a slit105, and bridges107. The light distribution portion103includes turning microstructures109. In some embodiments, the turning microstructures include prismatic microstructures as illustrated byFIG. 9B. In certain embodiments, the turning microstructures109can be formed directly on the light distribution portion109itself. In other embodiments, the turning microstructures109are part of a separate turning film. The turning films108can comprise, for example, a prismatic film having prismatic turning microstructures. The turning microstructures109directs light propagating through the light distribution portion103onto the display elements81. Light reflected from the display elements81is then transmitted through and out of the light distribution portion103.

FIGS. 10A and 10Bare a side cross sectional view and a top view of an integrated illumination system additionally comprising one or more reflectors on one or more sides of the light injection portion of the integrated illumination system. As illustrated inFIGS. 10A and 10B, the display device comprising the integrated illumination system may additionally comprises one or more reflectors or reflecting portions94,95,96,97disposed with respect to the sides (top101d, bottom101e, left101b, and/or back101f) of the light injection portion101of the integrated illumination system. In various embodiments, the reflective surfaces94,95,96, and97may comprise planar reflectors, although other shapes are possible. Additionally, the reflectors may comprise diffuse or specular reflectors, although diffuse reflectors may offer the advantage of altering the angle that reflected light returning to the light injection portion101propagates therein. In certain embodiments, the reflecting surfaces comprise metal, reflecting paint, or other reflective material. In some embodiments, a dielectric multilayer film (e.g., an interference coating) may be used. An interference coating constructed from dielectric films may advantageously reflect a greater portion of incident light than a metal reflective surface, as metal surfaces may absorb a portion of incident light.

FIG. 11Ais a top view of a corner region of the integrated illumination system having one long slit and a pair of bridges illustrating light leakage through one of the bridges. The corner region includes a section of the light injection portion101, a long slit105a, a light distribution portion103, and a bridge107. In order to form the bridges, the long slit105aruns nearly across the entire length of the integrated illumination system except at the bridges. The light injection portion receives light93emanating from the light source92. The light93comprises reflected light93athat is incident on and reflected by the optical interface created by the long slit105aas shown inFIG. 11A. The light93further comprises leaked light93bthat passes through the bridge107into the light distribution portion without undergoing total internal reflection by the optical interface created by the long slit105a. The leaked light93bcreates a “hot spot” in the corner region near the light source92. The hot spot is a location where the intensity of the light directed onto the light modulators is higher. The result is that a viewer sees a region of the display, for example, in the corner, that is brighter than the remainder of the display. This lack of uniformity may be distracting or otherwise degrades from the appearance of the display and the images produced by the display.

FIG. 11Bis a top view of a corner region of the integrated illumination system having a long slit and an additional short slit for reducing or eliminating light leakage through a bridge according to certain embodiments. As the example inFIG. 11Billustrates, the corner region of the example embodiment includes an additional short slit105balong with the long slit105asimilar to the one shown inFIG. 11A. In this arrangement with the additional slit105b, the portion of the light93bwhich would have otherwise leaked into the light distribution portion through the bridge107undergoes total internal reflection by another optical interface created by the additional short slit while maintaining the structural integrity of the integrated illumination system structure.

In certain embodiments, the additional short slit105bis disposed proximal to the bridge107and has the same length as the width of the bridge107as shown inFIG. 11B. In some embodiments, the width (e.g., in x-direction) of the additional slit105bhas substantially the same width as the wide slit105a. In some embodiments, the additional slit105bextends out to an extreme end, e.g., the first end101a, and another additional short slit may extend to the second opposite end101d(FIG. 9A) of the light injection portion101as shown inFIG. 11B. In some other embodiments, the additional slits105bdo not extend out to the extreme end of the light injection portion, thereby forming additional yet shorter bridges (not shown). The distance (e.g., in x-direction) between the long slit105aand the additional short slit105bis preferably between 1 mm and 5 mm. Methods for manufacturing the additional slit105bare substantially the same as those for manufacturing the long slit105adescribed above. For example, the short slits105can be formed on film by die-cutting, molding, and embossing.

In certain embodiments, the additional slit105bmay comprise an opening filled with air, gases, or liquid, e.g. adhesive flowed into at least part of the short slit. In various such embodiments, the light injection portion101and the additional slit105bform a high-index to low-index interface. In some embodiments, the high-index to low-index interface comprises a plastic/air interface. The shape of the additional slit is shown as rectangular but may differ. The additional slit may include flat parallel sides such as shown.

FIG. 12Ashows a cross sectional view of an integrated illumination system light transmission region showing a slit that is not accompanied by additional light control features. As discussed above with reference toFIG. 9B, the slit105is bounded by side walls, namely, the second opposite side101cof the light injection portion101and the first side103aof the light distribution portion103. The example slit shown inFIG. 12Ahas featureless flat side walls. AsFIG. 12Aillustrates, a portion of the light output or transmitted from light injection portion101can escape the integrated illumination system without being coupled to the light distribution portion103, thus reducing the light efficiency of the integrated illumination system.

In contrast,FIGS. 12B-Dshow cross sectional views (12C,12E) or top views (12B,12D) of a region near a slit having additional light control feature(s) on or between the side walls according to certain embodiments. In some of the embodiments, the light control feature(s) control the angular direction of the light coupled from the light injection potion into the light distribution portion by changing the direction of the coupled light, e.g., by collimating, diverging, deflecting the light. Such light control features can change the angular behavior of the coupled light in in-plane (y) direction, out-of-the-plane (z), direction, or both. For example,FIG. 12Bis a cross sectional view of a region of the integrated illumination system showing a slit and additional light control features comprising divergence enhancing features formed on one of the side walls according to certain embodiments. In certain embodiments, the divergence enhancing features comprise a plurality of concave-shaped features formed on at least one of the side walls. In some embodiments, the divergence enhancing features can include a substantially uniform cross section along the thickness (z) direction of the slit as shown inFIG. 12B. The divergence-enhancing features may comprise various sloping surfaces including planar or curved surfaces. In some embodiments, the redirecting features comprise grooves. The redirecting features may be symmetric or asymmetric. The divergence-enhancing features may have triangular cross-section, e.g., equilateral, isosceles, etc. The divergence-enhancing features may have other shapes as well.

The divergence enhancing features106acan receive light substantially collimated rays which are transmitted out of the light injection portion at substantially normal propagation angles with respect to the second opposite side101cof the light injection portion101and cause the light to diverge, e.g., in the plane of the light distribution portion, e.g., in the ±y propagation directions of the light rays as they get injected or coupled into the light distribution portion103. The divergence enhancing features106atend to diverge or broaden the in-plane (+/−y) angular distributions of the coupled light rays. Such divergence or broadening can help to achieve a uniformity of light across the light distribution portion.

As another example of a slit having light control features,FIG. 12Cis a cross sectional view of a region and the integrated illumination system having additional light control features comprising collimation features106bformed on side walls according to certain embodiments. In the example shown, the collimation features106binclude a pair of convex-shaped features formed on both of the side walls101c,103. The collimation features106bcan help reduce light escaping out of the integrated illumination system (seeFIG. 12A) by collimating and reducing divergence in the out-of-the-plane (z) direction a substantial portion of light output or transmitted from the light injection portion101, and similarly collimating the light injected or coupled into the light distribution portion103. In some embodiments, the collimation features can include a substantially uniform cross section along the length (y) direction of the slit as shown inFIG. 12C. In some embodiments, the convex-shaped collimation features comprise a cylindrical or other-shaped lens or lenslets. If the lenslets are collimating, the brightness of the display can be increased by the virtue of the fact that a greater portion of the collimated light is turned up (z-direction) towards the viewer. In certain embodiments, in-plane collimation is increased by the collimation features. In other embodiments, out-of-plane collimation is increased by the collimation features.

FIG. 12Dis a top view of another integrated illumination system that includes a slit having additional light control features comprising redirecting features106cformed on one of the side walls, e.g., the first side103aof the light distribution portion. In certain embodiments, the redirecting features comprise a plurality of sawtooth-shaped features formed on at least one of the side walls as shown inFIG. 12D. In some embodiments, the redirecting features can include a substantially uniform cross section along the thickness (z) direction of the slit. In some embodiments, the redirecting features can include microprisms. The redirecting features may comprise various sloping surfaces including planar or curved surfaces. In some embodiments, the redirecting features comprise grooves. The redirecting features may be symmetric or asymmetric. The redirecting features may have triangular cross-section, e.g., equilateral, isosceles, etc. The redirecting features may have other shapes as well.

In the example shown inFIG. 12D, the redirecting features106cchange the direction of the light rays, e.g., from (+x, +y) direction to (+x, −y) direction as shown inFIG. 12D. The light may be deflected to alter the intensity distribution of illumination of the spatial light modulators. Deflection of the coupled light can be beneficial as the upper edge and corner opposite the light source is often dim. Proper-shaped redirecting features can redirect light into these dim areas.

In addition or alternative to including features on the walls of the light injection portion and/or light distribution portion, optical elements and/or surfaces can be included within the slit. As yet another example of a slit having additional light control features,FIG. 12Eis a cross-sectional view of a region of the integrated illumination system showing a slit having a light control insert102placed between the side walls of the slit. In certain embodiments, in order to accommodate the extra light control insert, the width of the slit (e.g., in x-direction) may have to be made larger than what it would have been without the light control insert. In certain embodiments, the light control insert102has a rectangular bar shape having flat surfaces such as shown inFIG. 12E. In other embodiments, the light control insert102can include differently-shaped surfaces or features. The surfaces may be curved or planar, sloped, symmetric or asymmetric, etc. In some embodiments, the insert102may comprise one or more optical elements such as cylindrical lens or a plurality of lenslets or other structure. The light control insert102can utilize diffractive or other types of microstructure. By employing one or more of such microstructures, the light control insert can perform one or more of light control functions such as the ones described above. Therefore, by having a combination of light control features, for example, the light control insert can control both in-plane (e.g., x-y plane) and out-of-plane (e.g., z-direction) behaviors of the coupled light.

In addition, while the light control functions described above include the light angle control functions such as collimation, divergence, and deflection, the light control function performed by light control features formed on one or more side walls or on the light control insert can also include other control functions. For example, the light control insert can include a light filtering element to change the color of the coupled light. The light filtering element may transmit a narrow band of wavelengths when white light is incident thereon, thereby producing a color. Such color filter may be an absorptive color filter, wherein wavelengths of light are absorbed thereby filtering the white light and producing a color. Such absorptive filters may comprise for example absorptive material such as dyes. For example, the slit can be coated with dye molecules or quantum dots that convert UV light into R,G,B colors more appropriate for the display. Alternatively, the filters may comprise fluorescent material wherein incident light causes the element to fluoresce at one or more wavelengths, thereby producing a color. The incident light may, for example, be white light, ultraviolet (UV) light, etc.

As discussed above with reference toFIG. 11A, the presence of the bridges can cause some light to leak into the light distribution portion, and such leaked light can create a “hot spot” in the corner region near the light source92. The light leakage can also produce inefficiency and/or performance degradation as the leaked light does not get subjected to various efficiency/performance-enhancing features of the integrated illumination system. For example, the leaked light portion does not get controllably directed to the light distribution portion by the turning microstructure and may create an uneven distribution of light across the light distribution portion, illuminating certain parts of the light distribution portion more than others. As discussed above with reference toFIGS. 12B-12D, the slit may include certain light control features formed on the side walls to collimate, diverge, or change direction of the light transmitted through the slit, for example. In some embodiments, the light control features may change wavelength distribution of the light. The leaked light portion does not pass through the light control features, at least partially defeating particular benefits that the light control features are designed to engender.

A wide variety of variations are possible. Films, layers, components, features, structures, and/or elements may be added, removed, or rearranged. Additionally, processing steps may be added, removed, or reordered.