Patent Application
20140159587
This disclosure relates to display devices, including but not limited to display devices that incorporate electromechanical systems.
Electromechanical systems (EMS) include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components such as mirrors and optical films, and electronics. EMS devices or elements can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical and electromechanical devices.
One type of EMS device is called an interferometric modulator (IMOD). The term IMOD or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an IMOD display element may include a pair of conductive plates, one or both of which may be transparent and/or reflective, wholly or in part, and capable of relative motion upon application of an appropriate electrical signal. For example, one plate may include a stationary layer deposited over, on or supported by a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the IMOD display element. IMOD-based display devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with display capabilities. Although current IMOD displays and other reflective displays are generally satisfactory, improved methods and devices would be desirable.
The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.
One innovative aspect of the subject matter described in this disclosure can be implemented in a reflective display device that includes a front light system, a reflective display including a plurality of reflective pixels, a sensor system that includes an ambient light sensor and a control system. The front light system may be configured for producing light of a first color, light of a second color, light of a third color and substantially white light. The control system may be configured to receive ambient light data from the ambient light sensor and to determine, based at least in part on the ambient light data, a current operational mode from a plurality of operational modes.
The plurality of operational modes may include a field sequential color (FSC) mode in which the front light system illuminates the reflective display with white light while data are written to the plurality of reflective pixels. The control system may be configured to select, based at least in part on the ambient light data, a white light intensity level. The control system may be further configured to control the front light system and the reflective display according to the current operational mode and the white light intensity level.
In some implementations, the control system may be configured to determine a ratio of white light intensity to overall display illumination intensity. The overall display illumination intensity may include front light illumination intensity and ambient light illumination intensity.
The ambient light data may include ambient light intensity data. The control system may be configured to select the FSC operational mode if the ambient light data indicates a first ambient light intensity level that is below a first threshold. The control system may be configured to select a non-FSC operational mode if the ambient light data indicates a second ambient light intensity level that is at or above the first threshold. The control system may be configured to select an operational mode of substantially continuous front light operation if the second ambient light intensity level is below a second threshold. The control system may be configured to select an operational mode in which the front light is off if the second ambient light intensity level is at or above the second threshold.
In some implementations, the control system may be configured to determine an image content type and to select the current operational mode based, at least in part, on the image content type. The control system may be configured to select the white light intensity level based at least in part on a desired color gamut. The control system may be further configured to compute an objective measure of color breakup and to select the current operational mode based, at least in part, on the objective measure. In some implementations, the control system may be configured to vary the white light intensity level while maintaining a substantially constant brightness from the front light system.
According to some implementations, the sensor system may include a battery state sensor. The control system may be configured to receive battery state data from the battery state sensor and to select the current operational mode or the white light intensity level based, at least in part, on the battery state data.
The control system may be configured to process image data. In some implementations, the control system may include a driver circuit configured to send at least one signal to the reflective display. The control system may include a controller configured to send at least a portion of the image data to the driver circuit. The control system may include an image source module configured to send the image data to the processor. In some implementations, the image source module may include a receiver, a transceiver and/or a transmitter. The reflective display device may include an input device configured to receive input data and to communicate the input data to the control system.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of operating a display device. The method may involve receiving ambient light data from an ambient light sensor and determining, based at least in part on the ambient light data, a current operational mode for the display from a plurality of operational modes. The plurality of operational modes may include an FSC mode in which a lighting system illuminates the display with white light while data are written to the display.
The method may involve selecting, based at least in part on the ambient light data, a white light intensity level. The method may involve controlling the lighting system and the display according to the current operational mode and the white light intensity level.
In some implementations, the method may involve selecting the FSC operational mode if the ambient light data indicates a first ambient light intensity level that is below a first threshold. The method may further involve selecting a non-FSC operational mode if the ambient light data indicates a second ambient light intensity level that is at or above the first threshold. The method may involve determining an image content type and selecting the current operational mode based, at least in part, on the image content type. The method may involve selecting the white light intensity level based at least in part on a desired color gamut.
According to some implementations, the method may involve computing an objective measure of color breakup. The method may further involve selecting the current operational mode based, at least in part, on the objective measure of color breakup. In some implementations, the method may involve varying the white light intensity level while maintaining a substantially constant brightness from the lighting system.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory medium having software stored thereon. The software may include instructions for controlling an apparatus to receive ambient light data from an ambient light sensor and to determine, based at least in part on the ambient light data, a current operational mode for a display from a plurality of operational modes. The plurality of operational modes may include an FSC mode in which a lighting system illuminates the display with white light while data are written to the display. The software may include instructions for controlling the apparatus to select, based at least in part on the ambient light data, a white light intensity level and to control the lighting system and the display according to the current operational mode and the white light intensity level.
The software further may include instructions for controlling the apparatus to select the FSC operational mode if the ambient light data indicates a first ambient light intensity level that is below a first threshold. The software further may include instructions for controlling the apparatus to select a non-FSC operational mode if the ambient light data indicates a second ambient light intensity level that is at or above the first threshold. In some implementations, the software further may include instructions for controlling the apparatus to determine an image content type and to select the current operational mode based, at least in part, on the image content type.
According to some implementations, the software further may include instructions for controlling the apparatus to select the white light intensity level based at least in part on a desired color gamut. The software further may include instructions for controlling the apparatus to compute an objective measure of color breakup and to select the current operational mode based, at least in part, on the objective measure. The software further may include instructions for controlling the apparatus to vary the white light intensity level while maintaining a substantially constant brightness from the lighting system.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Although the examples provided in this summary are primarily described in terms of MEMS-based displays, the concepts provided herein may apply to other types of displays, such as cholesteric LCD displays, transflective LCD displays, electrofluidic displays, electrophoretic displays and displays based on electro-wetting technology. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
Like reference numbers and designations in the various drawings indicate like elements.
The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device, apparatus, or system that can be configured to display an image, whether in motion (such as video) or stationary (such as still images), and whether textual, graphical or pictorial. More particularly, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices such as, but not limited to: mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, Bluetooth® devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, facsimile devices, global positioning system (GPS) receivers/navigators, cameras, digital media players (such as MP3 players), camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), computer monitors, auto displays (including odometer and speedometer displays, etc.), cockpit controls and/or displays, camera view displays (such as the display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (such as in electromechanical systems (EMS) applications including microelectromechanical systems (MEMS) applications, as well as non-EMS applications), aesthetic structures (such as display of images on a piece of jewelry or clothing) and a variety of EMS devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes and electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art.
Field-sequential color (FSC) techniques can be applied to reflective displays, including but not limited to IMOD displays, using field-sequential front lights that may include light sources for various colors. FSC methods can provide enhanced brightness and/or color gamut for reflective displays in conditions of dim ambient light. However, FSC methods may cause noticeable color breakup (“CBU”) under certain conditions. CBU is a perceptual phenomenon that is caused by relative motion between a viewer's eye and a reflective display being operated in an FSC mode. Due to CBU, a viewer may see colored fringes around a displayed object. Therefore, various implementations described herein provide FSC modes in which the front light system illuminates a display with white light while data are written to the display. The intensity of white light may be controlled to optimize color gamut and CBU effects.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some implementations, illuminating a display with white light while data are written to the display during an FSC operational mode can mitigate the effects of CBU. In some implementations, the intensity of white light may be controlled to shape the color gamut produced by a display device. Illuminating the display with white light while data are written to the display during an FSC operational mode may increase overall display brightness.
Although most of the description herein pertains to IMOD displays, many such implementations could be used to advantage in other types of reflective displays, including but not limited to cholesteric LCD displays, transflective LCD displays, electrofluidic displays, electrophoretic displays and displays based on electro-wetting technology. Moreover, while the interferometric modulator displays described herein generally include red, blue and green subpixels, many implementations described herein could be used in reflective displays having other colors of subpixels, e.g., having violet, yellow-orange and yellow-green subpixels. In addition, many implementations described herein could be used in reflective displays having more colors of subpixels, e.g., having subpixels corresponding to 4, 5 or more colors. Some such implementations may include subpixels corresponding to red, blue, green and yellow. Alternative implementations may include subpixels corresponding to red, blue, green, yellow and cyan. Moreover, some implementations described below involve FSC methods for single-mirror IMODs (SM-IMODs).
An example of a suitable EMS or MEMS device or apparatus, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulator (IMOD) display elements that can be implemented to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMOD display elements can include a partial optical absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. In some implementations, the reflector can be moved to two or more different positions, which can change the size of the optical resonant cavity and thereby affect the reflectance of the IMOD. The reflectance spectra of IMOD display elements can create fairly broad spectral bands that can be shifted across the visible wavelengths to generate different colors. The position of the spectral band can be adjusted by changing the thickness of the optical resonant cavity. One way of changing the optical resonant cavity is by changing the position of the reflector with respect to the absorber.
The IMOD display device can include an array of IMOD display elements which may be arranged in rows and columns. Each display element in the array can include at least a pair of reflective and semi-reflective layers, such as a movable reflective layer (i.e., a movable layer, also referred to as a mechanical layer) and a fixed partially reflective layer (i.e., a stationary layer), positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap, cavity or optical resonant cavity). The movable reflective layer may be moved between at least two positions. For example, in a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively and/or destructively depending on the position of the movable reflective layer and the wavelength(s) of the incident light, producing either an overall reflective or non-reflective state for each display element. In some implementations, the display element may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when actuated, absorbing and/or destructively interfering light within the visible range. In some other implementations, however, an IMOD display element may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the display elements to change states. In some other implementations, an applied charge can drive the display elements to change states.
The depicted portion of the array in
In
The optical stack 16 can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer, and a transparent dielectric layer. In some implementations, the optical stack 16 is electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate 20. The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals (e.g., chromium and/or molybdenum), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, certain portions of the optical stack 16 can include a single semi-transparent thickness of metal or semiconductor which serves as both a partial optical absorber and electrical conductor, while different, electrically more conductive layers or portions (e.g., of the optical stack 16 or of other structures of the display element) can serve to bus signals between IMOD display elements. The optical stack 16 also can include one or more insulating or dielectric layers covering one or more conductive layers or an electrically conductive/partially absorptive layer.
In some implementations, at least some of the layer(s) of the optical stack 16 can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having ordinary skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer 14, and these strips may form column electrodes in a display device. The movable reflective layer 14 may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack 16) to form columns deposited on top of supports, such as the illustrated posts 18, and an intervening sacrificial material located between the posts 18. When the sacrificial material is etched away, a defined gap 19, or optical cavity, can be formed between the movable reflective layer 14 and the optical stack 16. In some implementations, the spacing between posts 18 may be approximately 1-1000 μm, while the gap 19 may be approximately less than 10,000 Angstroms (Å).
In some implementations, each IMOD display element, whether in the actuated or relaxed state, can be considered as a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer 14 remains in a mechanically relaxed state, as illustrated by the display element 12 on the left in
The processor 21 can be configured to communicate with an array driver 22. The array driver 22 can include a row driver circuit 24 and a column driver circuit 26 that provide signals to, for example a display array or panel 30. The cross section of the IMOD display device illustrated in
In some implementations, a frame of an image may be created by applying data signals in the form of “segment” voltages along the set of column electrodes, in accordance with the desired change (if any) to the state of the display elements in a given row. Each row of the array can be addressed in turn, such that the frame is written one row at a time. To write the desired data to the display elements in a first row, segment voltages corresponding to the desired state of the display elements in the first row can be applied on the column electrodes, and a first row pulse in the form of a specific “common” voltage or signal can be applied to the first row electrode. The set of segment voltages can then be changed to correspond to the desired change (if any) to the state of the display elements in the second row, and a second common voltage can be applied to the second row electrode. In some implementations, the display elements in the first row are unaffected by the change in the segment voltages applied along the column electrodes, and remain in the state they were set to during the first common voltage row pulse. This process may be repeated for the entire series of rows, or alternatively, columns, in a sequential fashion to produce the image frame. The frames can be refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second.
The combination of segment and common signals applied across each display element (that is, the potential difference across each display element or pixel) determines the resulting state of each display element.
As illustrated in
When a hold voltage is applied on a common line, such as a high hold voltage VCHOLD
When an addressing, or actuation, voltage is applied on a common line, such as a high addressing voltage VCADD
In some implementations, hold voltages, address voltages, and segment voltages may be used which produce the same polarity potential difference across the modulators. In some other implementations, signals can be used which alternate the polarity of the potential difference of the modulators from time to time. Alternation of the polarity across the modulators (that is, alternation of the polarity of write procedures) may reduce or inhibit charge accumulation that could occur after repeated write operations of a single polarity.
During the first line time 60a: a release voltage 70 is applied on common line 1; the voltage applied on common line 2 begins at a high hold voltage 72 and moves to a release voltage 70; and a low hold voltage 76 is applied along common line 3. Thus, the modulators (common 1, segment 1), (1,2) and (1,3) along common line 1 remain in a relaxed, or unactuated, state for the duration of the first line time 60a, the modulators (2,1), (2,2) and (2,3) along common line 2 will move to a relaxed state, and the modulators (3,1), (3,2) and (3,3) along common line 3 will remain in their previous state. In some implementations, the segment voltages applied along segment lines 1, 2 and 3 will have no effect on the state of the IMOD display elements, as none of common lines 1, 2 or 3 are being exposed to voltage levels causing actuation during line time 60a (i.e., VCREL-relax and VCHOLD
During the second line time 60b, the voltage on common line 1 moves to a high hold voltage 72, and all modulators along common line 1 remain in a relaxed state regardless of the segment voltage applied because no addressing, or actuation, voltage was applied on the common line 1. The modulators along common line 2 remain in a relaxed state due to the application of the release voltage 70, and the modulators (3,1), (3,2) and (3,3) along common line 3 will relax when the voltage along common line 3 moves to a release voltage 70.
During the third line time 60c, common line 1 is addressed by applying a high address voltage 74 on common line 1. Because a low segment voltage 64 is applied along segment lines 1 and 2 during the application of this address voltage, the display element voltage across modulators (1,1) and (1,2) is greater than the high end of the positive stability window (i.e., the voltage differential exceeded a characteristic threshold) of the modulators, and the modulators (1,1) and (1,2) are actuated. Conversely, because a high segment voltage 62 is applied along segment line 3, the display element voltage across modulator (1,3) is less than that of modulators (1,1) and (1,2), and remains within the positive stability window of the modulator; modulator (1,3) thus remains relaxed. Also during line time 60c, the voltage along common line 2 decreases to a low hold voltage 76, and the voltage along common line 3 remains at a release voltage 70, leaving the modulators along common lines 2 and 3 in a relaxed position.
During the fourth line time 60d, the voltage on common line 1 returns to a high hold voltage 72, leaving the modulators along common line 1 in their respective addressed states. The voltage on common line 2 is decreased to a low address voltage 78. Because a high segment voltage 62 is applied along segment line 2, the display element voltage across modulator (2,2) is below the lower end of the negative stability window of the modulator, causing the modulator (2,2) to actuate. Conversely, because a low segment voltage 64 is applied along segment lines 1 and 3, the modulators (2,1) and (2,3) remain in a relaxed position. The voltage on common line 3 increases to a high hold voltage 72, leaving the modulators along common line 3 in a relaxed state. Then, the voltage on common line 2 transitions back to the low hold voltage 76.
Finally, during the fifth line time 60e, the voltage on common line 1 remains at high hold voltage 72, and the voltage on common line 2 remains at the low hold voltage 76, leaving the modulators along common lines 1 and 2 in their respective addressed states. The voltage on common line 3 increases to a high address voltage 74 to address the modulators along common line 3. As a low segment voltage 64 is applied on segment lines 2 and 3, the modulators (3,2) and (3,3) actuate, while the high segment voltage 62 applied along segment line 1 causes modulator (3,1) to remain in a relaxed position. Thus, at the end of the fifth line time 60e, the 3×3 display element array is in the state shown in
In the timing diagram of
The details of the structure of IMOD displays and display elements may vary widely.
As illustrated in
In implementations such as those shown in
In
The process 80 continues at block 84 with the formation of a sacrificial layer 25 over the optical stack 16. Because the sacrificial layer 25 is later removed (see block 90) to form the cavity 19, the sacrificial layer 25 is not shown in the resulting IMOD display elements.
The process 80 continues at block 86 with the formation of a support structure such as a support post 18. The formation of the support post 18 may include patterning the sacrificial layer 25 to form a support structure aperture, then depositing a material (such as a polymer or an inorganic material, like silicon oxide) into the aperture to form the support post 18, using a deposition method such as PVD, PECVD, thermal CVD, or spin-coating. In some implementations, the support structure aperture formed in the sacrificial layer can extend through both the sacrificial layer 25 and the optical stack 16 to the underlying substrate 20, so that the lower end of the support post 18 contacts the substrate 20. Alternatively, as depicted in
The process 80 continues at block 88 with the formation of a movable reflective layer or membrane such as the movable reflective layer 14 illustrated in Figure [#H4]. The movable reflective layer 14 may be formed by employing one or more deposition steps, including, for example, reflective layer (such as aluminum, aluminum alloy, or other reflective materials) deposition, along with one or more patterning, masking and/or etching steps. The movable reflective layer 14 can be patterned into individual and parallel strips that form, for example, the columns of the display. The movable reflective layer 14 can be electrically conductive, and referred to as an electrically conductive layer. In some implementations, the movable reflective layer 14 may include a plurality of sub-layers 14a, 14b and 14c as shown in
The process 80 continues at block 90 with the formation of a cavity 19. The cavity 19 may be formed by exposing the sacrificial material 25 (deposited at block 84) to an etchant. For example, an etchable sacrificial material such as Mo or amorphous Si may be removed by dry chemical etching by exposing the sacrificial layer 25 to a gaseous or vaporous etchant, such as vapors derived from solid XeF2 for a period of time that is effective to remove the desired amount of material. The sacrificial material is typically selectively removed relative to the structures surrounding the cavity 19. Other etching methods, such as wet etching and/or plasma etching, also may be used. Since the sacrificial layer 25 is removed during block 90, the movable reflective layer 14 is typically movable after this stage. After removal of the sacrificial material 25, the resulting fully or partially fabricated IMOD display element may be referred to herein as a “released” IMOD.
In some implementations, the packaging of an EMS component or device, such as an IMOD-based display, can include a backplate (alternatively referred to as a backplane, back glass or recessed glass) which can be configured to protect the EMS components from damage (such as from mechanical interference or potentially damaging substances). The backplate also can provide structural support for a wide range of components, including but not limited to driver circuitry, processors, memory, interconnect arrays, vapor barriers, product housing, and the like. In some implementations, the use of a backplate can facilitate integration of components and thereby reduce the volume, weight, and/or manufacturing costs of a portable electronic device.
The backplate 92 can be essentially planar or can have at least one contoured surface (e.g., the backplate 92 can be formed with recesses and/or protrusions). The backplate 92 may be made of any suitable material, whether transparent or opaque, conductive or insulating. Suitable materials for the backplate 92 include, but are not limited to, glass, plastic, ceramics, polymers, laminates, metals, metal foils, Kovar and plated Kovar.
As shown in
The backplate components 94a and/or 94b can include one or more active or passive electrical components, such as transistors, capacitors, inductors, resistors, diodes, switches, and/or integrated circuits (ICs) such as a packaged, standard or discrete IC. Other examples of backplate components that can be used in various implementations include antennas, batteries, and sensors such as electrical, touch, optical, or chemical sensors, or thin-film deposited devices.
In some implementations, the backplate components 94a and/or 94b can be in electrical communication with portions of the EMS array 36. Conductive structures such as traces, bumps, posts, or vias may be formed on one or both of the backplate 92 or the substrate 20 and may contact one another or other conductive components to form electrical connections between the EMS array 36 and the backplate components 94a and/or 94b. For example,
The backplate components 94a and 94b can include one or more desiccants which act to absorb any moisture that may enter the EMS package 91. In some implementations, a desiccant (or other moisture absorbing materials, such as a getter) may be provided separately from any other backplate components, for example as a sheet that is mounted to the backplate 92 (or in a recess formed therein) with adhesive. Alternatively, the desiccant may be integrated into the backplate 92. In some other implementations, the desiccant may be applied directly or indirectly over other backplate components, for example by spray-coating, screen printing, or any other suitable method.
In some implementations, the EMS array 36 and/or the backplate 92 can include mechanical standoffs 97 to maintain a distance between the backplate components and the display elements and thereby prevent mechanical interference between those components. In the implementation illustrated in
Although not illustrated in
In alternate implementations, a seal ring may include an extension of either one or both of the backplate 92 or the substrate 20. For example, the seal ring may include a mechanical extension (not shown) of the backplate 92. In some implementations, the seal ring may include a separate member, such as an O-ring or other annular member.
In some implementations, the EMS array 36 and the backplate 92 are separately formed before being attached or coupled together. For example, the edge of the substrate 20 can be attached and sealed to the edge of the backplate 92 as discussed above. Alternatively, the EMS array 36 and the backplate 92 can be formed and joined together as the EMS package 91. In some other implementations, the EMS package 91 can be fabricated in any other suitable manner, such as by forming components of the backplate 92 over the EMS array 36 by deposition.
In some implementations, rows of an IMOD display can be scanned and written with different colors (e.g., red, green, and blue) sequentially, and then the corresponding colored light from a front light of the display may be flashed onto the display for a certain time after the rows are scanned. While writing data of a primary color of interest in subpixels of rows in the display, corresponding subpixels of the remaining primary colors may be written to black, or driven according to data for the color of interest, simultaneously.
Referring first to
However, in the implementation depicted in
After all subpixels in the array have been addressed, the array of subpixels is illuminated with red light, from time t2 until time t3. (See block 910 of
The time interval between t1 and t4 may be referred to herein as a “field,” which corresponds to a sub-unit of a frame during which data for a particular color are written and within which the display is illuminated with light of that color. In this example, the time interval between t1 and t4 may be referred to as a “red field,” because this first field corresponds to a time during which red data of a frame of image data are written to subpixels of the display and during which the subpixels are illuminated with red light. The entire frame of data extends from t1 to t10, after which time the next frame of data is written.
From time t4 to time t5, data of a second color are written to subpixels for the second color in rows of the array of subpixels, while subpixels for other colors are scrolled to black. (See block 915 of
Next, data of a third color are written to subpixels for the third color in rows of the array of subpixels, while subpixels for other colors are scrolled to black. (See block 925 of
At this point, an entire frame of image data has been written to the subpixel array. The next frame of image data may be written to the subpixel array by returning to block 905 and repeating the above-described process for the next frame. Although in the above example (and other examples described herein) the sequence of colors is red/green/blue, the order in which the color data are written and the corresponding colored light is flashed does not matter and may differ in other implementations.
Referring now to
Beginning at time t2, red data of a frame of image data are written to rows of red subpixels. The “drive” time for writing data to the subpixel rows, from time t2 until time t3, may be on the order of a few milliseconds (ms), e.g., between 1 and 10 ms. In some implementations, this time may be on the order of 3 to 6 ms. In this example, all of the rows of green and blue subpixels kept in a black state from time t2 until after the subpixel array is illuminated with red light. In alternative implementations, all of the rows of green and blue subpixels may be flashed to black during the time that red data are being written.
After all subpixels in the array have been addressed, the array of subpixels is illuminated with red light, in this example from time t3 until time t4. The time interval between t1 and t4 is another example of a red field. The illumination time may, for example, be on the order of 1 or more ms. In some implementations, there may be a short time (e.g., a few microseconds) between the time at which the last row of subpixels is addressed and the time at which the array of subpixels is illuminated. However, in alternative implementations, the array of subpixels may be illuminated before last row of subpixels is addressed. For example, the array of subpixels may be illuminated after most, but not all, of the subpixels have been addressed (e.g., after approximately 70%, 75%, 80%, 85%, 90% or 95% of the subpixels have been addressed).
Beginning at time t4, all of the rows of red subpixels are flashed to black at substantially the same time. In alternative implementations, all of the rows of red subpixels may be flashed to black during the time that green data are being written. In this example, all of the rows of blue subpixels are also flashed to black. However, in alternative implementations, all of the rows of blue subpixels may be maintained in a black state from the time that they were previously flashed to black until after the subpixel array is illuminated with green light.
From time t5 to time t6, data of a second color are written to subpixels for the second color in rows of the array of subpixels, while subpixels for other colors are kept in a black state. In the example shown in
Next, all of the rows of green subpixels are flashed to black at substantially the same time, starting at time t7 in this example. The time interval between t4 and t7 is another example of a green field. In alternative implementations, all of the rows of green subpixels may be flashed to black during the time that blue data are being written. In this example, all of the rows of red subpixels are also flashed to black. However, in alternative implementations, all of the rows of red subpixels may be maintained in a black state from the time that they were previously flashed to black until after the subpixel array has been illuminated with blue light.
Data of a third color are written to subpixels for the third color in rows of the array of subpixels, while subpixels for other colors are kept in a black state. In the example shown in
At this point, an entire frame of image data has been written to the subpixel array. The next frame of image data may be written to the subpixel array by repeating the above-described process for the next frame. Although in the above example (and other examples described herein) the sequence of colors is red/green/blue, the order in which the color data are written and the corresponding colored light is flashed does not matter and may differ in other implementations.
Scrolling black and flash to black implementations have the advantage of increased color saturation, as compared to IMODs driven according to some conventional schemes, when the front light of a display is being used. When used in a relatively dark environment, the appearance is dominated by the light provided to the display by the front light. If the ambient light becomes bright enough, however, the reflective color will be dimmer than during typical IMOD display operation in reflective mode (about ⅓ as bright), because only 1 type of subpixel is “on” (not driven to black) at a time. Accordingly, in some instances it will be determined in block 935 that the scrolling black method will end. For example, it may be determined in block 935 that the operational mode of the display will be altered because of a change in ambient light conditions, because of an indication received from a user input device, etc. In some implementations, the display may be configured to provide vivid colors even under bright ambient light.
One example is shown in
In this example, the array of subpixels is illuminated with red light after all subpixels in the array have been addressed and written with red data of the frame of image data, from time t2 (or from a time just after time t2) until time t3. (See block 1110 of
From time t4 to time t5, data of a second color are written to subpixels for the first, second and third colors in rows of the array of subpixels. (See block 1115 of
Next, data of a third color are written to all subpixels in the array of subpixels. (See block 1125 of
At this time, a frame of image data has been written to the subpixel array. It may then be determined whether to change the operational mode of the display or whether to continue controlling the display in accordance with method 1100. The next frame of image data may be written to the subpixel array in accordance with method 1100 by returning to block 1105 and repeating the above-described processes for the next frame. The determination in block 1135 of whether to change the operational mode of the display may be made, for example, in response to a change in ambient light conditions and/or in response to user input. If the ambient light is sufficiently bright while controlling a display in accordance with method 1100, the ambient light may make the display appear to be a black and white display instead of a color display. Therefore, it can be advantageous to change the operational mode of the display according to the brightness of ambient light. Some relevant methods of are described below with reference to
However, when used in conditions of low ambient light, method 1100 may result in greater brightness and color saturation than some conventional interferometric modulation subpixel illumination methods. Method 1100 may even result in greater brightness and color saturation than the “flash to black” and “scrolling black” implementations described above with reference to FIGS. 9 and 10A-B. However, this may depend on the spectral responses of the subpixels in the array.
Accordingly, when the green subpixels are illuminated with some wavelengths of light in the blue range or the red range, the response of the green subpixels may provide additional blue or red color. For example, when the subpixel array is illuminated with light in wavelength range 1320, the green subpixels contribute an amount of brightness in the blue wavelength range that is indicated by area 1325. The combined contribution of the blue and green subpixels is indicated by the additional area 1330, the area of which is the same as that of the area 1325.
In some implementations, some but not all of the rows may be scanned and written with data of a certain color of a frame, followed by flashing a corresponding colored light, and the remaining rows can be scanned and written with data of the particular color of the frame later. Some examples will now be described with reference to
In the example of
In block 1415, data for a second color (which is green in this example) are written to all subpixels in alternating rows 0, 2, 4 through N−1, while all subpixels in alternating rows 1, 3, 5 through N are driven to black. The entire subpixel array is then illuminated with green light. (See block 1420.) Then, data for a third color, which is blue in this example, are written to all subpixels in alternating rows 0, 2, 4 through N−1, while all subpixels in alternating rows 1, 3, 5 through N are driven to black. (See block 1425.) The entire subpixel array is then illuminated with blue light. (See block 1430.)
After the operation of block 1430, only half a frame of image data has been written to the subpixel array. Therefore, in block 1435, red data are written to all subpixels in odd-numbered rows (alternating rows 1, 3, 5 through N in this example), while all subpixels in even-numbered rows (alternating rows 0, 2, 4 through N−1 in this example) are driven to black. The entire subpixel array is then illuminated with red light. (See block 1440.)
In block 1445, data for a second color, which is green in this example, are written to all subpixels in alternating rows 1, 3, 5 through N, while all subpixels in alternating rows 0, 2, 4 through N−1 are driven to black. The entire subpixel array is then illuminated with green light. (See block 1450.) Then, data for a third color, which is blue in this example, are written to all subpixels in alternating rows 1, 3, 5 through N, while all subpixels in alternating rows 0, 2, 4 through N−1 are driven to black. (See block 1455.) The entire subpixel array is then illuminated with blue light. (See block 1460.) In block 1465, it is determined whether to continue controlling the display according to method 1400.
Here, data for a first color (e.g., red data) from row 0 of the image data may first be written to all subpixels in rows 0 and 1 of the display. At the same time, red data from row 2 of the image data may be written to all subpixels in rows 2 and 3 of the display, while red data from row 4 of the image data may be written to all subpixels in rows 4 and 5 of the display, etc., until all subpixel rows have been addressed. None of the subpixel rows are driven to black in this example. The display may then be illuminated by red light.
Data for a second color (e.g., green data) from even-numbered rows of the image data may then be written to all subpixels of the display. Green data from row 0 of the image may be written to all subpixels in rows 0 and 1 of the display, while green data from row 2 of the image data may be written to all subpixels in rows 2 and 3 of the display, and so on. None of the subpixel rows are driven to black in this example. The display may then be illuminated by green light.
In the same manner, data for a third color (e.g., blue data) from even-numbered rows of the image data may then be written to all subpixels of the display. The display may then be illuminated by blue light.
At this stage, half a frame of image data has been written to the display. To write the next half of the frame, red data from row 1 of the image may first be written to all subpixels in rows 1 and 2 of the display, while red data from row 3 of the image may be written to all subpixels in rows 3 and 4 of the display, etc., until all subpixel rows have been addressed. None of the subpixel rows are driven to black in this example. The display may then be illuminated by red light. In the same manner, green data from odd-numbered rows of the image may then be written to all subpixels of the display. The display may then be illuminated by green light. Blue data from odd-numbered rows of the image may then be written to adjacent subpixel rows of the display. The display may then be illuminated by blue light. At this time, an entire data frame will have been written.
Some such odd/even implementations have the advantage of being able to increase the overall time frame for writing a frame without causing noticeable flicker. In general, the shorter the overall frame time, the less chance of noticeable flicker. The time for writing an image data frame and illuminating the display should be kept below the flicker threshold Tflicker, beyond which a typical observer will detect flicker. Tflicker is a function of various factors, such as display resolution, subpixel size, the distance between an observer and the display, etc. There is also a subjective aspect to flicker perception.
For example, suppose that a “scrolling black” implementation (e.g., an implementation described above with reference to FIGS. 9 and 10A-B) had a frame time of 25 ms. An odd/even implementation might have a frame time of 40 ms (20 ms for the even rows and 20 ms for the odd rows), yet may have even less noticeable flicker than the scrolling black implementation. For a 40 ms frame time with the odd/even implementation, an observer's flicker perception may be similar to that for a frame having a 20 ms frame time. This is made possible by high display resolution: the spatial resolution of a high-resolution display can suppress flicker. The odd and even lines can dither each other in, so that odd/even methods implemented in a high-resolution display may have the same flicker perception as much shorter frames.
The subpixel size and spacing of the display affects Tflicker. For a given display size, having smaller subpixels means there are more rows of subpixels. Having more rows of subpixels will generally mean a relatively longer time for addressing all of the rows. A longer addressing time tends to make the frame time longer and having longer frame times tends to cause flicker. However, having relatively smaller subpixels can help to avoid artifacts due to spatial dithering. Accordingly, having higher resolution results in relatively fewer spatial artifacts, but more temporal artifacts (flicker). If a display is viewed at a distance of approximately 1.5 feet to 2 feet, a display line spacing on the order of 40 to 60 microns should provide sufficiently high resolution for the 40 ms frame time with the odd/even implementation in the foregoing example. A display line spacing in the low tens of microns, e.g., less than 50 microns, would further reduce the chance of perceptible flicker for this example.
Having a longer frame time allows for the possibility of increasing the overall time of flashing the colored light, which increases the brightness of the display. The available time to address a display is Taddress=Nlines*line time, where line time is the time to write data to a single row and Nlines is the number of lines to which data will be written in the display. In some implementations, the front light flashing time can be computed by: Tflashing
For example, suppose that a “scrolling black” implementation had a frame time of 21 ms, with 18 ms for writing color data (6 ms per color) and 3 ms for flashing colored light from the front light (1 ms per color). An odd/even implementation might have a frame time of 42 ms (21 ms for the even rows and 21 ms for the odd rows). If the odd/even implementation took 18 ms for writing color data, the remaining 24 ms could be used for flashing colored light from the front light (4 ms for each color during both the odd phase and the even phase). However, a display being operated according to an odd/even implementation would generally still be dimmer in bright ambient light conditions than the display when being operated in a full reflective mode, such as the one described above with reference to
Alternatively, one can take advantage of the longer frame time to lower power consumption. Power usage is proportional to the flash time: if the flash time is not increased when the frame time is increased, less power will be consumed. The settings for specific implementations may seek to optimize power consumption and color saturation/gamut.
Other variations to the odd/even implementations may involve writing data to every third row, every fourth row, etc., and then flashing a corresponding colored light. Still other variations may involve adjusting the flashing time of colored lights after different sets of rows are scanned. For example, in some implementations, even rows may be illuminated for a first time whereas odd rows may be illuminated for a second time. The first time may be longer or shorter than the second time.
In alternative implementations, data of two colors (e.g., red and blue because their spectral responses are sufficiently separated) can be written first and then the corresponding colored lights (e.g., red light and blue light) may be flashed together. Referring again to
Green data may then be written to green subpixels of the display, while red and blue subpixels are driven to black. (See block 1615.) The display may then be illuminated with green light. (See block 1620.) At this time, a frame of data has been written. In block 1635, it is determined whether to write another frame or to change the operational mode.
Such methods may be used in various ways. If so desired, these methods could be used to reduce the field time and therefore the frame time. By writing data and illuminating the display twice within a frame, instead of writing data and illuminating the display three times as in some of the above-described methods, the frame length could be reduced by approximately ⅓ if the writing time and flashing time are held substantially constant. For example, if a “scroll to black” implementation had a frame length of 18 ms, method 1600 could reduce the frame length to 12 ms. Alternatively, or additionally, these methods may be used to increase the overall amount of time available for illuminating the display. If the same frame length is used (e.g., 18 ms), an additional ⅓ of the frame (6 ms) becomes available for illumination. For example, if the overall “flash time” available in a “scroll to black” implementation is 3 ms per frame, which may be divided equally between the three colors (i.e., 1 ms per color), the illumination time of method 1600 could be increased to 9 ms if so desired. The red and blue lights could be flashed for 4.5 ms and the green light could be flashed for 4.5 ms in one example. Note that the available “flash time” may not be divided equally between the colors. Different lengths of time could be used for the different colors, e.g., 5 ms for red and blue and 4 ms for green.
At this time, a frame of image data has been written to the display. It may then be determined (block 1735) whether to revert to block 1705 and write another frame or to change the operational mode of the display.
It may be observed from
Some display devices may be configured to use two or more different field-sequential color methods for controlling the display. In the example shown in
Method 2015 may be used when the ambient light is sufficiently bright that illumination via a front light is not beneficial. In some implementations, a “taper off” method may be used to transition between method 2010 and powering off the front light. For example, the front light may be powered off over a few hundred ms, half a second or some other period of time.
Referring again to
As the display device is being operated, the ambient light intensity may be monitored. In block 1915, for example, it is determined whether the ambient light intensity has changed beyond a predetermined threshold. Small changes in ambient light may indicate that the same field-sequential color method will be used to control the display, but with a higher or low level of power applied (see
If it is determined in block 1920 that the front light should still be used, it may be determined whether or not the same field-sequential color method will be used to control the display (block 1925). In block 1930, the display will be controlled according to the field-sequential color method determined in block 1925. In block 1940, it is determined whether to continue in the current operational mode, e.g., as described elsewhere herein. If so, the power level may be adjusted according to ambient light intensity (see
Some implementations described herein can produce a black and white display suitable for displaying text. For example, a black and white display may be produced using a magenta light (e.g., made by adding a magenta filter to white light generated by a light source) to illuminate green interferometric subpixels, or vice versa.
In some implementations, the same display device can provide a color display in a dark environment (e.g., indoors) and a black and white (monochrome) display in a bright environment (e.g., outdoors). Alternatively, in some such implementations, all of the interferometric subpixels in the display could be configured to produce substantially the same spectral response. For example, all of the interferometric subpixels in the display could be configured as green subpixels. Such a display would not provide a multi-color display.
Applying the foregoing field-sequential color methods to reflective displays can provide a number of advantages. For example, when a reflective display is used in low ambient light conditions, the foregoing field-sequential color methods can increase the color gamut of the display. Some implementations provide increased brightness and/or color saturation.
However, providing grayscale for such displays has proven to be challenging. One might imagine that known temporal grayscale methods could be combined with the above-mentioned field-sequential color methods in a reflective display. However, it is not apparent how such methods could be combined. With temporal grayscale methods, the gray level depends on the length of time the image is displayed. For example, to have two bits of grayscale via a temporal grayscale method, a display is addressed twice during a single frame. The MSB is used to drive the display twice as long as the LSB. Such methods do not seem to be compatible with the above-described field-sequential color methods, which involve pulsing a colored light source briefly after image data for a corresponding color field are written.
Accordingly, novel grayscale methods are disclosed herein. Some such methods exploit the overlapping spectral responses of reflective subpixels. In the example described above with reference to
However, in some other implementations, there may be a more substantial overlap between the spectral responses for red and blue subpixels. One such implementation will now be described with reference to
If all three subpixels were configured to reflect light when the blue LED is illuminated, the combined intensity would be the sum of intensities 2220, 2225 and 2230. However, if the red subpixel were in a black state while the green and blue subpixels were configured to reflect light, the combined intensity would be the sum of intensities 2220 and 2225. Similarly, if the green subpixel were in a black state while the red and blue subpixels were configured to reflect light, the combined intensity would be the sum of intensities 2220 and 2230. Accordingly, the amount of brightness for each color may be modulated according to the state of each subpixel.
Some implementations described herein use colors other than the field color to produce grayscale. In this three-bit example, the field color may correspond to the most significant bit (MSB) and the other colors may correspond to the other two bits. For the blue field, the blue subpixel may be driven according to the MSB (B[0]), the green subpixel may be driven according to the next bit (B[1]) and the red subpixel may be driven according to the least significant bit (LSB) B[2].
Although the state of each reflective subpixel corresponds with a bit in this example, the contributions of each subpixel will not generally correspond with powers of two. Instead, the contributions of each subpixel will depend on the spectral response of each subpixel and the extent of overlap with the spectral response of the other subpixels of the display. For example, by comparing the intensity corresponding to the LSB for green (G[2]) to the intensities of the LSB for blue (B[2]) and red (R[2]), one can see that the intensity of G[2] is substantially greater than that of B[2] or R[2]. This means that in this example, when the blue subpixel is configured to reflect light it will contribute more intensity to the green field than a reflective red subpixel will contribute to the blue field.
Here, the three-bit group (1,1,1) corresponds with a subpixel state 2310 in which the red, green and blue subpixels are all configured to reflect light in the red field. Therefore, the subpixel state 2310 corresponds with maximum brightness for red color. The three-bit group (1,1,0) corresponds with a subpixel state 2311 in which only the red and green subpixels are configured to reflect light in the red field. The blue subpixel is configured to be in the black state and therefore does not make a significant intensity contribution in the red field. However, because the blue subpixel corresponds with the LSB R[2], if the intensity contribution is similar to that shown in
The three-bit group (1,0,1) corresponds with a subpixel state 2312 in which only the red and blue subpixels are configured to reflect light in the red field. The green subpixel is configured to be in the black state and therefore does not make a significant intensity contribution in the red field. Because the green subpixel corresponds with R[1], this subpixel state 2312 may be substantially less bright than the subpixel state 2310 corresponding to the three-bit groups (1,1,1). For example, if the intensity contributions of the blue and green subpixels in the red field are similar to those shown in
However, intensities corresponding to the three-bit groups (1,1,0) and (1,0,1) may vary substantially from field to field. For example, if the intensity contributions of the blue and red subpixels in the green field also are similar to those shown in
Referring again to
The process 2400 of
The reflective display may include an illumination system, reflective subpixels and a control system. The illumination system may include a front light that is configured to illuminate the reflective display with a first color, a second color and a third color. The reflective display may include a plurality of first reflective sub-pixels corresponding to the first color, a plurality of second reflective sub-pixels corresponding to the second color and a plurality of third reflective sub-pixels corresponding to the third color. The control system may, for example, include at least one of a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or combinations thereof.
Accordingly, in some implementations the blocks of the process 2400 may be implemented, at least in part, by such a control system. In some implementations, the process 2400 may be implemented, at least in part, by software encoded in a non-transitory medium. The software may include instructions for controlling a reflective display to perform the process 2400 or other processes described herein.
In block 2405, an MSB of first data corresponding to the first color may be written to at least some of the first reflective subpixels. A next bit of the first data may be written to the second reflective sub-pixels (block 2410) and an LSB of the first data may be written to at least some of the third reflective sub-pixels (block 2415). In some implementations, the control system may be configured to assign bit values according to grayscale levels that correspond with values of the MSB, the next bit and the LSB. The control system may be configured to receive grayscale level data and to determine the bit values according to the grayscale level data. For example, the control system may be configured to determine the bit values by referencing a data structure that has grayscale levels and corresponding values of the MSB, the next bit and the LSB stored therein.
The front light may be controlled to flash the first color on the reflective display after the first data have been written to the first, second and third reflective sub-pixels (block 2420). The blocks 2405 through 2420 correspond to a first color field of a frame of image data in this example.
Referring to
Returning to
Referring again to
Returning to
In
Returning again to
The foregoing example involves three-bit groups and eight grayscale levels. However, other implementations may involve more or fewer bits and brightness levels. Some such implementations are described below.
Referring first to
Because only two bits are used to control three subpixel colors, subpixels having a color other than the field color are controlled according to the same bit in this example. Here, both the green subpixel and the blue subpixel are controlled according to the same bit (the LSB) when the field color is red. When the field color is green, both the red and the blue subpixels are controlled according to the LSB. When the field color is blue, the red and the green subpixels are controlled with the LSB.
Accordingly, the two-bit group (1,1) and the three-bit group (1,1,1) both correspond to the same subpixel state 2310. Similarly, the same subpixel state 2310 corresponds to the two-bit group (1,0) and the three-bit group (1,0,0). (See
In alternative implementations, however, the subpixels may be grouped differently. In some such implementations, the subpixel corresponding to the field color (the red subpixel in this example) and one of the other subpixels may be controlled according to the MSB. For example, in the red field the red subpixel and the blue subpixel may both be controlled according to the MSB for red. In such implementations, the same subpixel state 2310 may correspond to the two-bit group (1,0) and the three-bit group (1,0,1). (See
The process 2700 of
In block 2705, an MSB of first data for a first color may be written to at least some first reflective sub-pixels corresponding to the first color. An LSB of the first data also may be written to at least some second reflective sub-pixels corresponding to a second color (block 2710) and to at least some third reflective sub-pixels corresponding to a third color (block 2715). An illumination system, which may include a front light, may be controlled to flash the first color on the reflective display after the first data have been written to the first, second and third reflective sub-pixels (block 2720). The blocks 2705 through 2720 correspond to a first color field for a frame of image data in this example.
An MSB of second data for the second color may then be written to at least some of the second reflective sub-pixels (block 2725). An LSB of the second data also may be written to at least some of the first reflective sub-pixels (block 2730) and to at least some of the third reflective sub-pixels (block 2735). The illumination system may be controlled to flash the second color on the reflective display after the second data have been written to the first, second and third reflective sub-pixels (block 2740). The blocks 2725 through 2740 correspond to a second color field for a frame of image data.
Subsequently, an MSB of third data for the third color may be written to at least some of the third reflective sub-pixels (block 2745). An LSB of the third data also may be written to at least some of the second reflective sub-pixels (block 2750) and to at least some of the first reflective sub-pixels (block 2755). The illumination system may be controlled to flash the third color on the reflective display after the third data have been written to the first, second and third reflective sub-pixels (block 2760). The blocks 2745 through 2760 correspond to a third color field for a frame of image data.
In block 2765 it is determined (e.g., by a control system of the display) whether to continue the process 2700. For example, the process 2700 may end (block 2770) if user input is received indicating that the reflective display will be switched off, if the reflective display enters a sleep mode, etc. However, if it is determined in the block 2765 that the process 2700 will continue, the process 2700 reverts to the block 2705 in this example. The first field of another frame of image data may be processed.
When observed under conditions of dim ambient light, black and white FSC methods, such as those described above with reference to
This effect may be seen in
In the graph 2800, color gamut is plotted on the vertical axis and ambient light intensity is plotted on the horizontal axis. In this example, the units of ambient light intensity are lux. The range of ambient light intensity shown in the graph 2800 is approximately half of the range for which a front light would normally be used for a reflective display: typically, a front light would be used when the ambient light intensity is below a threshold of approximately 1,000 lux.
As shown in
In general, lup2down FSC methods do not provide as high a color gamut as that provided by the black and white FSC methods. However, the color gamut provided by lup2down FSC methods does not decrease as rapidly as the ambient light illumination increases. This effect may be seen in
As compared to black and white FSC implementations having the same levels of light source intensity, the lup2down FSC implementations do not have as large a decrease in color gamut as the ambient light illumination increases. For example, as the ambient light illumination increases from zero to 100 lux, the lup2down FSC implementation having a front light with a brightness of 10 nits (see the curve 2905) has a color gamut that decreases from 60% to about 25%. The color gamut of the corresponding black and white FSC implementation decreases from 80% to approximately 6% as the ambient light intensity increases from zero to 100 lux (see the curve 2805 of
Accordingly, as compared to the black and white FSC implementations, even the lup2down FSC implementations having the lowest levels of light source intensity do not show as precipitous a drop in color gamut as the ambient light illumination increases. The lup2down FSC implementations with higher levels of light source intensity still provide a substantial color gamut percent as the ambient light illumination approaches 500 lux: the color gamuts of these implementations range from about 15% to about 44% at this level of ambient light illumination (see curves 2910-2930).
Therefore, some reflective display device implementations described herein may include a control system that is configured to change an operational mode of the front light and/or the display according to ambient light data. A conceptual basis for some such implementations is shown in
In this example, the region 3015 corresponds to a black and white FSC operational mode for use in the lowest levels of ambient light illumination. In some implementations, for example, the region 3015 may extend from substantially zero lux to an ambient light illumination in the range of approximately 50 lux to 500 lux at the boundary 3017. In some implementations, operational modes involving grayscale FSC methods may be used for levels of ambient light illumination corresponding to the region 3015.
The region 3020 corresponds to a lup2down FSC operational mode for use in relatively higher levels of ambient light illumination. In some implementations, for example, the region 3020 may extend from an ambient light illumination in the range of 50-500 lux (at the boundary 3017) to an ambient light illumination in the range of approximately 400-600 lux (at the boundary 3022). Accordingly, FSC operational modes may be implemented if the ambient light intensity is below a first threshold. In this example, the first threshold corresponds to the boundary 3022.
The regions 3025 and 3030 correspond to non-FSC operational modes for use under relatively higher levels of ambient light illumination. The region 3035 corresponds to a relatively higher level of ambient light illumination, wherein the front light is switched off. Accordingly, when the ambient light intensity is above the first threshold (in this example, the boundary 3022) but below a second threshold (in this example, the boundary 3032), non-FSC operational modes that involve operating a front light may be implemented. In some implementations, for example, the region 3025 may extend from approximately 400-600 lux (at the boundary 3022) to approximately 800-900 lux (at the boundary 3027), whereas the region 3030 may extend from the boundary 3027 to approximately 1000 lux at the boundary 3032. In this example, the region 3025 corresponds to an operational mode wherein red, green and blue light sources of a front light are used to illuminate a reflective display, whereas the region 3030 corresponds to an operational mode wherein the front light illuminates the reflective display with one or more white light sources. In both operational modes, the light sources of the front light may be switched on in a substantially continuous manner instead of being flashed on and off. In some other implementations, only three modes (e.g., FSC-monochrome, RGB (non-FSC) and FL OFF) with two typical approximate thresholds (e.g., 600 lux and 1000 lux) may be used. In such implementations, the five modes shown in
It will be appreciated by a person of ordinary skill in the art that other implementations described herein may involve other FSC and/or non-FSC operational modes. The ambient light intensity levels corresponding to such operational modes may differ from those shown in
In this example, the method 3100 begins with block 3105, in which ambient light data are received. Referring to
Block 3110 of
For example, block 3110 may involve selecting a current operational mode for the reflective display 3220 and the front light system 3215 of
Block 3110 may involve selecting the current operational mode based, at least in part, upon whether the ambient light data indicates an ambient light intensity level that is at or below a first threshold. If so, block 3110 may involve selecting an FSC operational mode. If not, block 3110 may involve selecting a non-FSC operational mode.
For example, referring to
If the ambient light data indicate an ambient light intensity level that is in the region 3030, block 3110 may involve selecting a non-FSC operational mode in which one or more substantially white light sources of the front light are continuously on in block 3115. If the ambient light data indicate an ambient light intensity level that is above the region 3030, block 3110 may involve selecting a non-FSC operational mode in which the front light is switched off in block 3115.
However, other FSC and non-FSC operational modes may be among the operational modes available for selection. For example, block 3110 may involve selecting a 2up1down FSC operational mode, in which only one out of three subpixel colors are driven to black at any one time. In one 2up1down FSC implementation, data may be written corresponding to a combined primary for the colors that are written. For example, if red and green were written and blue was kept off (black), then data would be written at that point calculated for a yellow primary. This would happen for other two combinations as well, e.g., for cyan and magenta. Such 2up1down FSC implementations can produce a brighter display than lup2down FSC implementations, but with relatively more limited gamut.
The operational modes may include an “interlace” operational mode, in which image data are rendered in an interlaced format. Relevant examples are disclosed in United States Patent Publication No. 2006/0066504, which is hereby incorporated by reference. Alternatively, or additionally, the operational modes may include an operational mode for producing line multiplied images, wherein the line multiplying is shifted for one of the colors of the display with respect to at least one other color of the display. Some such operational modes involve green offset line doubling. Relevant examples are disclosed in United States Patent Publication No. 2012/0098847, which is hereby incorporated by reference.
As noted above, the ambient light data may include data other than intensity data. In some implementations, the ambient light data may include ambient light temporal frequency data. For example, desk lamps with light emitting diodes (LEDs) are typically driven according to pulse width modulation methods. Accordingly, the LEDs flash on and off rapidly. The LEDs are generally flashing on and off too quickly for a person to perceive this effect. However, when a reflective display is being controlled according to some FSC operational modes at a time that the reflective display is being exposed to such flashing room lighting LEDs, a stroboscopic effect may be produced that is readily apparent to a human observer. Accordingly, if the ambient light data received in block 3105 include ambient light temporal frequency data that indicate flashing ambient light, block 3110 may involve selecting a non-FSC operational mode.
Some types of ambient light may produce a “white” light that includes a disproportionate amount of green, yellow, blue or some other color. Accordingly, in some implementations, the ambient light data received in block 3105 may include ambient light spectrum data. If the operational mode selected in block 3110 involves operating a front light, the spectrum of the front light may be adjusted to compensate for the ambient light spectrum. For example, if the ambient light spectrum data indicate that the ambient light includes a disproportionate amount of green light, the green light source(s) of the front light may be operated in block 3115 at a lower intensity level, in order to compensate for the ambient light spectrum.
In block 3120, it is determined whether the method 3100 will continue. This determination may, for example, be made according to input from an activity timer, such as the activity timer 4322 of
Referring again to
In this implementation, the front light system 3215 includes light sources configured for producing at least the range of spectral emissions and the second range of spectral emissions. The front light system 3215 also may include light sources configured for producing other ranges of spectral emissions. For example, the front light system 3215 also may include light sources configured for producing a third range of spectral emissions, a fourth range of spectral emissions and/or additional ranges of spectral emissions. The front light system 3215 also may include one or more light sources configured for producing substantially white light.
The control system 3205 may, for example, include at least one of a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or combinations thereof. The control system 3205 may include one or more memory devices, such as random access memory (RAM), read-only memory (ROM), etc. Alternatively, or additionally, such memory devices (or other types of memory devices) may be included in other portions of the reflective display device 3200, in another device, etc., and may be accessible by the control system 3205 via a direct connection, a network interface, etc.
As noted above, the sensor system 3210 includes an ambient light sensor in this implementation. However, the sensor system 3210 also may include one or more other types of sensors. In some implementations, the sensor system 3210 includes a battery state sensor. The use of such other sensors will be described in more detail below.
The foregoing description has focused primarily on implementations involving bi-stable IMODs, which can be configured in only two positions, open or closed. A single image pixel will typically include three or more bi-stable IMODs, each of which corresponds to a subpixel. In a display device that includes multi-state interferometric modulators (MS-IMODs) or analog IMODs (A-IMODs), a pixel's reflective color may be determined by the gap spacing or “gap height” between an absorber stack and a mirror stack of a single IMOD. Some A-IMODs may be positioned in a substantially continuous manner between a large number of gap heights, whereas MS-IMODs generally may be positioned in a smaller number of gap heights. Because each mirror may correspond to a pixel in both types of devices, A-IMODs and MS-IMODs are treated herein as examples of the broader category of single-mirror IMODs (SM-IMODs). SM-IMODs can produce vivid, saturated colors under bright ambient light conditions.
In an SM-IMOD, a pixel's reflective color may be varied by changing the gap height between an absorber stack and a mirror stack. In
In some implementations, the absorber layer may be formed of a partially absorptive and partially reflective layer. The absorber layer may be part of an absorber stack that includes other layers, such as one or more dielectric layers, an electrode layer, etc. According to some such implementations, the absorber stack may include a dielectric layer, a metal layer and a passivation layer. In some implementations, the dielectric layer may be formed of silicon dioxide (SiO2), silicon oxynitride (SiON), magnesium fluoride (MgF2), aluminum oxide (Al2O3) and/or other dielectric materials. In some implementations, the metal layer may be formed of chromium (Cr), tungsten (W), nickel (Ni), vanadium (V), titanium (Ti), rhodium (Rh), platinum (Pt), germanium (Ge), cobalt (Co) and/or molychrome (MoCr, a molybdenum-chromium alloy). In some implementations, the passivation layer may include Al2O3 or another dielectric material.
The mirrored surface may, for example, be formed of a reflective metal such as aluminum (Al), silver (Ag), etc. The mirrored surface may be part of a reflector stack that includes other layers, such as one or more dielectric layers. Such dielectric layers may be formed of titanium oxide (TiO2), silicon nitride (Si3N4), zirconium oxide (ZrO2), tantalum pentoxide (Ta2O5), antimony trioxide (Sb2O3), hafnium(IV) oxide (HfO2), scandium(III) oxide (Sc2O3), indium(III) oxide (In2O3), tin-doped indium(III) oxide (Sn:In2O3), SiO2, SiON, MgF2, Al2O3, hafnium fluoride (HfF4), ytterbium(III) fluoride (YbF3), cryolite (Na3AlF6) and/or other dielectric materials.
In
An incident wave having a wavelength λ will interfere with its own reflection from the mirror stack 3305 to create a standing wave with local peaks and nulls. The first null is λ/2 from the mirror and subsequent nulls are located at λ/2 intervals. For that wavelength, a thin absorber layer placed at one of the null positions will absorb very little energy.
Referring first to
In
In
Some examples of applying FSC techniques to SM-IMODs will now be described with reference to
The logic system 3405 may, for example, include at least one of a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or combinations thereof. According to some implementations, the logic system 3405 may include the processor 21, the driver controller 29, the array driver and/or other elements that are shown in
For example, in some implementations the logic system 3405 may be configured to control the front light 3410 and the IMOD array 3415 to make such transitions according to input from an ambient light sensor, a user input system, etc., such as shown in
In some implementations, the front light 3410 may at least partially overlie the IMOD array 3415. The front light 3410 may include a substantially transparent wave guide and light-extracting elements such as prisms, dots, etc., that are configured to illuminate the IMOD array 3415 with light sources of various colors. For example, the front light 3410 may include light sources corresponding to at least a first color and a second color. The front light 3410 also may include light sources corresponding to a third color, a fourth color and/or other colors. In some implementations, the front light 3410 may include light sources for blue, green and red colors. Alternatively, or additionally, the front light 3410 may include light sources for other colors, such as yellow, yellow-orange, yellow-green, violet, cyan, white and/or magenta.
The IMOD array 3415 may include a plurality of SM-IMODs. As used herein, analog IMODs are considered to be one type of SM-IMODs. Accordingly, the IMOD array 3415 may include a plurality of analog IMODs. Each of the IMODs may have an absorber layer and a mirrored surface. The IMODs may be configured to define a gap height in between the absorber layer and a mirrored surface. As described above with reference to
In this example, the method 3500 begins by controlling an SM-IMOD to have a first configuration corresponding to a first gap height between an absorber layer and a mirrored surface (block 3505). As noted elsewhere herein, in some implementations the SM-IMOD may be an analog IMOD. The gap height may correspond to a reflectivity of the IMOD for a particular wavelength of incident light.
In this implementation, block 3510 involves controlling a front light to flash a first light source corresponding to a first color when the SM-IMOD is in the first configuration. In this example, the front light has light sources for a plurality of colors, like the front light 3410.
In this example, block 3515 involves controlling the SM-IMOD to have a second configuration corresponding to a second gap height between the absorber layer and the mirrored surface. While the SM-IMOD is in the second configuration, the front light may be controlled to flash a second light source corresponding to a second color (block 3520).
In the example shown in
In some implementations, the block 3525 may involve determining whether to continue operating the display device, e.g., according to input from a user. Alternatively, or additionally, the block 3525 may involve determining whether to change the operational mode of the display device, e.g., according to input from an ambient light sensor as describe above.
Alternatively, or additionally, the block 3525 may involve determining whether an image data frame is complete. In this example, the image data frame is complete after two light source colors have been flashed during times when the SM-IMOD was in two configurations.
However, in alternative implementations, a data frame will not be complete until three or more light source colors have been flashed during times when the SM-IMOD was in three or more configurations. For example, alternative methods may involve controlling the SM-IMOD to have a third configuration corresponding to a third gap height between the absorber layer and the mirrored surface and controlling the front light to flash a third light source corresponding to a third color when the SM-IMOD is in the third configuration. The block 3525 may involve determining whether an image data frame is complete. For example, the image data frame may be complete after three light source colors have been flashed during times when the SM-IMOD was in three configurations.
However, alternative implementations may involve controlling the SM-IMOD to have a fourth configuration corresponding to a fourth gap height between the absorber layer and the mirrored surface and controlling the front light to flash a fourth light source corresponding to a fourth color when the SM-IMOD is in the fourth configuration. It may be determined in block 3525 that the image data frame may be complete after four light source colors have been flashed during times when the SM-IMOD was in four configurations.
The gap heights may also vary according to the implementation. For example, in some implementations, the gap heights may be less than or equal to a gap height that corresponds with a black state of the SM-IMOD. Some such implementations, including some grayscale FSC implementations, are described below with reference to
Some implementations for controlling SM-IMODs according to FSC techniques will now be described with reference to
Here, the yellow color has substantially equal amounts of red and green. The brightest yellow will be produced by configuring the SM-IMOD with a gap height G1 when the SM-IMOD is being illuminated with a green light and by configuring the SM-IMOD with a gap height R1 when the SM-IMOD is being illuminated with a red light. In this example, no blue component is desired, so the SM-IMOD is configured with a gap height B1 when the SM-IMOD is being illuminated with a blue light. B1 corresponds to a gap height at which the SM-IMOD will reflect little or no blue light.
In some implementations, a color may not be flashed if that color will not contribute significantly to the combined color. For example, in the situation depicted in
Using similar principles, some FSC operational modes also may produce a more pure (less green) white state. According to some such implementations, the SM-IMOD may be configured with a gap height of less than 5 nm (e.g., 2 or 3 nm) when the blue light is flashed, yielding a blue reflectivity of approximately 70%. In order to substantially match this reflectivity, the gap height may be slightly less than 20 nm when the red light is flashed and slightly greater than 20 nm when the green light is flashed.
Some grayscale FSC examples will now be discussed with reference to
In some grayscale FSC implementations, grayscale levels may be obtained by varying the gap height between the black state and second-order color peaks.
Here, as above, a yellow color that has substantially equal amounts of red and green is being produced by the SM-IMOD. The brightest yellow will be produced by configuring the SM-IMOD with a gap height G1 when the SM-IMOD is being illuminated with a green light, by configuring the SM-IMOD with a gap height R1 when the SM-IMOD is being illuminated with a red light and by configuring the SM-IMOD with a gap height B1 when the SM-IMOD is being illuminated with a blue light.
A yellow that is substantially the same shade but about ⅔ as bright can be produced by configuring the SM-IMOD with a gap height G2 when the SM-IMOD is being illuminated with a green light and with a gap height R2 when the SM-IMOD is being illuminated with a red light. In this example, the SM-IMOD is configured with a gap height B2 when the SM-IMOD is being illuminated with a blue light. B2 is substantially the same as B1.
In order to produce substantially the same shade of yellow, but about ⅓ as bright, the SM-IMOD may be configured with a gap height G3 when the SM-IMOD is being illuminated with a green light and with a gap height R3 when the SM-IMOD is being illuminated with a red light. In this example, the SM-IMOD is configured with a gap height B3, which is substantially the same as B1, when the SM-IMOD is being illuminated with a blue light.
In the foregoing examples, three different grayscale levels were produced. However, in alternative examples, more or fewer grayscale levels may be produced.
As noted above, in some alternative implementations a color may not be flashed if that color will not contribute significantly to the combined color. For example, in the situations depicted in
Color breakup (which may be referred to herein as “CBU”) is a perceptual phenomenon that is associated with FSC methods. CBU may be caused by relative motion between a viewer's eye and a display that is being operated according to an FSC method. CBU may occur when the different color components of image data frames do not coincide in space. This may happen, for example, the display is in a first location relative to the eye when a red light source flashes, a second location relative to the eye when a green light source flashes, etc. Due to CBU, a viewer may see colored fringes around a displayed object.
Including white light (e.g., from a white LED) with the colors flashed during an FSC operational mode can alleviate CBU. Including white light has the effect of bringing colors closer together in color space, even though the colors may be spatially dispersed on the retina.
In block 3805, ambient light data are received from an ambient light sensor. The ambient light sensor may, for example, be part of the sensor system 3210 of the reflective display device 3200. The ambient light data may include ambient light intensity data.
Block 3810 involves determining, based at least in part on the ambient light data, a current operational mode for a display. The display may, for example, be a reflective display such as the reflective display 3220 illustrated in
Block 3815 involves selecting, based at least in part on the ambient light data, a white light intensity level. For example, block 3815 may involve selecting a white light intensity level for a lighting system of a display device. The lighting system may be configured for producing light of three or more colors and may include a source of substantially white light. The lighting system may, for example, be a front light system such as the front light system 3215 of the reflective display device 3200. For example, block 3815 may involve selecting, by the control system 3205, a white light intensity level for the front light system 3215 that will be used to illuminate the reflective display 3220.
In some implementations, the control system 3205 may be configured to determine a ratio of white light intensity to an overall display illumination intensity. The overall display illumination intensity may include front light illumination intensity and ambient light illumination intensity. For example, based on the ambient light intensity data received in block 3805, block 3815 may involve selecting the white light intensity level to maintain the ratio of white light intensity to an overall display illumination intensity.
In some implementations, block 3815 may involve selecting a white light intensity in order to maintain a substantially constant brightness from the front light system. For example, based on the ambient light intensity data received in block 3805, a ratio of white light intensity to front light illumination intensity may be determined. Block 3815 may involve varying the white light intensity level in order to maintain the ratio of white light intensity to front light illumination intensity. Block 3820 involves controlling the lighting system and the display according to the current operational mode and the white light intensity level. Some examples are provided below.
The method 3900 begins with block 3905, in which data of a first color is written to all subpixels in an IMOD display while illuminating the display with white light. Here, the front light system 3215 may be configured for producing light of three or more colors. In this example, the front light system 3215 includes red, green and blue LEDs, and a source of substantially white light. In some implementations, the source of substantially white light may be white LEDs, whereas in other implementations the source of substantially white light may be red, green and blue LEDs operated simultaneously. Other colors and/or types of light sources may be used in other implementations. In some implementations, block 3905 may involve writing data of the first color to substantially all, but not all, subpixels in an IMOD display. For example, in some implementations, data may not be written to “dummy” subpixels in a border area of a display in block 3905, block 3915 or block 3925.
Accordingly, in the example shown in
In block 3910 of
In block 3915 of
In block 3925 of
At this time, a frame of image data has been written to the subpixel array. In block 3935, it may then be determined (e.g., by the control system 3205 of
By using an FSC operational mode such as that described above, one can mitigate the effects of color breakup. However, illuminating a display with white light has potential drawbacks. For example, illuminating a display with white light tends to de-saturate the colors produced by a display.
The curve 4110 represents the color gamut provided by a display that is being controlled according to an FSC operational mode such as that described above with reference to
The “CBU comfort zone” was derived by performing human perception tests, comparing observers' subjective perceptions of CBU with a computed CBU score and mapping the results to color gamut space. Some examples of computing a CBU score are provided below. The threshold 4120 bounding the CBU comfort zone represents a transition between an annoying level of CBU (above the threshold 4120) and a perceptible, but not annoying level of CBU (below the threshold 4120). The position of the threshold 4120 may vary from person to person, according to subjective perceptions of CBU. In a lower portion of the CBU comfort zone (e.g., the bottom ⅓), CBU may be imperceptible to most observers. However, the extent to which CBU is perceptible to a particular person will vary according to that person's subjective perception.
As shown in
Some implementations take into account the effects of white light on color gamut. Some such implementations take into account not only CBU effects, but also color gamut effects.
The ambient light thresholds 4205, 4210 and 4215 and/or the light control values may, for example, be stored in a memory that is accessible by a control system of a display device. In some such implementations, the control system may be configured to select an FSC operational mode if the ambient light data received from an ambient light sensor indicates an ambient light intensity level that is below the threshold 4205. The control system may be configured to select a non-FSC operational mode if the ambient light data indicates an ambient light intensity level that is at or above the threshold 4205. In this example, an ambient light intensity that is at or above the threshold 4205 corresponds to typical outdoor lighting conditions. Here, the threshold 4205 is approximately 1000 lux, but in other examples the threshold 4205 may be at a higher or lower ambient light intensity level.
In this implementation, if the ambient light intensity level is at or above the threshold 4205 but below the threshold 4210, the control system may select a non-FSC operational mode involving substantially continuous front light operation. However, if the ambient light intensity level is at or above the threshold 4210, the control system may select a non-FSC operational mode in which the front light is turned off. In this example, the threshold 4210 is approximately 2000 lux, but in other examples the threshold 4210 may be at a higher or lower ambient light intensity level.
The range of ambient light intensities below the threshold 4205 may correspond with a range of FSC operational modes. As described above, such FSC operational modes may include black and white or “monochrome” FSC operational modes as well as lup2down FSC operational modes.
At least some of the FSC operational modes corresponding to ambient light intensities that are below the threshold 4215 may involve illuminating the display with white light. In this example, the white light is provided by a white LED. Here, the front light also includes red, green and blue light sources, which are red, green and blue LEDs in this example.
In this implementation, the control system may be configured to vary the white light intensity level while maintaining a substantially constant brightness from the front light system when the ambient light intensity levels are below the threshold 4215. In the example shown in
The control system may decrease the white LED intensity and/or duration for higher ambient light intensity levels. In some implementations, the control system may decrease the white LED intensity in a substantially continuous manner as the ambient light intensity increases, whereas in other implementations the control system may decrease the white LED intensity in a stepwise manner as the ambient light intensity increases. In the example shown in
In some implementations the selection of a current operational mode for a display device may be based, at least in part, on criteria other than ambient light data. Examples of some such implementations will now be described with reference to
In some implementations, the mode switching controller 4305 may be configured to select an operational mode according to one or more of the methods described above. For example, the mode switching controller 4305 may be configured to select an operational mode according to ambient light data from the ambient light sensor 4310. In some implementations, the mode switching controller 4305 may be configured to select an operational mode from among the operational modes provided by way of example in block 4315 of
Some implementations may involve determining a desired color gamut and selecting the current operational mode based, at least in part, on the desired color gamut. For example, the color gamut of a display device being operated according to an FSC mode may extend outside of the sRGB color gamut. In such implementations, it may be desirable to shape the color gamut of the display device by increasing the white light illumination during FSC mode. In alternative implementations, it may be desirable to enlarge the color gamut of the display device by decreasing the white light illumination during FSC mode. In some implementations, the mode switching controller 4305 may be configured to select an operational mode according to display luminance and/or color gamut data corresponding to various display devices and/or operational modes. Such data (and/or other data) may be stored in memory 4340 and provided to the mode switching controller 4305 as needed.
In some implementations, the image data input module 4332 and/or the image processing module 4345 may be configured to analyze the color gamut of input images and to provide image color gamut input to the mode switching controller 4305. The mode switching controller 4305 may be configured to select an operational mode based, at least in part, on the image color gamut input. For example, if the image color gamut input indicates that the color gamut of an image is small, the mode switching controller 4305 may be configured to increase the intensity of white light used to illuminate the display during an FSC mode.
However, some implementations, may involve selecting an operational mode based on other criteria. For example, some implementations may include a battery state sensor. The control system may be configured to receive battery state data from the battery state sensor and to select the current operational mode (and/or the white light intensity level) based, at least in part, on the battery state data. In the implementation shown in
The mode switching controller 4305 may be configured to select an operational mode based, at least in part, on input from other modules. For example, if the application type indicator 4330 provides input to the mode switching controller 4305 indicating that a text-based application will be executed on the reflective display device 3200, the mode switching controller 4305 may determine that the extra power and computational overhead of FSC operational modes are not warranted. Alternatively, if the application type indicator 4330 provides input to the mode switching controller 4305 indicating that a graphics-intensive application will be executed on the reflective display device 3200 (such as a photo album application, a video-based application, etc.), the mode switching controller 4305 may determine that an FSC operational mode would be appropriate for certain ambient light conditions and/or battery states.
The mode switching controller may change modes according to other energy-saving criteria. For example, the activity timer 4322 may provide input indicating when the current operational mode should be evaluated or when the reflective display device 3200 should enter a sleep mode, as described above.
Some implementations may involve determining an image content type and selecting the current operational mode based, at least in part, on the image content type. For example, if the image data input module 4332 or the image processing module 4345 provide input to the mode switching controller 4305 indicating that video data will be provided on the reflective display device 3200, the mode switching controller 4305 may determine that an FSC operational mode would be appropriate under certain ambient lighting (and/or other) conditions. For example, the mode switching controller 4305 may determine that a black and white FSC operational mode or a grayscale FSC operational mode would be appropriate under predetermined ambient light conditions and/or battery states. However, if the mode switching controller 4305 receives input indicating that text will be displayed on the display device, the mode switching controller 4305 may select a different operational mode, e.g., a less power-intensive operational mode.
In this implementation, the control system 3205 also includes a CBU detection module 4335. In some implementations, the CBU detection module 4335 may be configured to compute an objective measure of CBU, also referred to herein as a CBU score, and to provide the CBU score to the mode switching controller 4305. Based at least in part on the CBU score, the mode switching controller 4305 may be configured to provide corresponding instructions to the front light controller 4320 and/or the drive scheme/panel controller 4315.
The CBU score may be based on input display color palette data 4405 and input CBU criteria 4410. The CBU criteria 4410 may include one or more of input pattern data, image object velocity data, viewing distance data, etc. The CBU simulator 4400 also may be configured for outputting an output pattern 4415, which may indicate the degree of CBU of the input pattern.
In some implementations wherein the CBU detection module 4335 is used for system design and/or set-up, the CBU simulator 4400 may determine an objective measure of CBU by using a black-to-white step edge as image content for an input pattern, where eye saccades or eye tracking is assumed corresponding to whether the input pattern is stationary or moving. Due to field sequential color driving, the white input pattern may be decomposed, at least in part, by one or more of the causes of CBU. Accordingly, the white input pattern may be spatially displaced, at least in part, into its individual color components. The degree of spatial displacement of the color components may depend on various criteria, such as the relative motion between the eyes and the display or the tracked object, the speed of eye saccades, etc. The levels of the color components may depend on the display color palette. The CBU score may be a function of the difference between the input pattern and the displayed pattern containing color breakup. The CBU score may be directly related to the relative displacement and levels of the color components into which the white pattern decomposes. In some implementations, the CBU score may be based on a CIELAB metric or an S-CIELAB metric, which is a spatial adaptation of CIELAB known as perceptual color fidelity. Some implementations may involve some degree of smoothing and/or motion blurring of a reference image when computing a CBU score.
The CBU simulator 4400 may be configured to calculate an objective measure of CBU in various ways, e.g., as described in one or more of the following references: A. Yoshida, M. Kobayashi and Y. Yoshida, “Subjective and Objective Assessments of Color Breakup on Field Sequential Color Display Devices,” 2011 SID Digest, pp. 313-316, 2011; X. Zhang and J. E. Farrell, “Spatial Color Breakup Measured with Induced Saccades,” in Proc. SPIE 2003, vol. 5007, pp. 210-217; and K. Sekiya, T. Miyashita and T. Uchida, “A Simple and Practical Way to Cope with Color Breakup on Field Sequential Color LCDs,” 2006 SID Digest, pp. 1661-1664.
As noted in these references, saccadic eye movements, relative motion between the head and the display, and eye tracking of moving objects in a scene can cause color breakup perception. The strength of perceived color breakup in general depends on the amount of relative motion between the eyes/head and the displayed content, the extent and range of colors in the displayed content, the viewing distance, the display brightness and contrast, ambient lighting level, and the colors that the display is capable of generating (the display color palette). Peak retinal velocity, background luminance level, sub-frame frequency and target size may all have significant effects on perceived color break-up.
In some implementations, the CBU detection module 4335 may be configured to provide a CBU score to the mode switching controller 4305 (see
The display device 40 includes a housing 41, a display 30, an antenna 43, a speaker 45, an input device 48, a sensor system 3210 and a microphone 46. The housing 41 can be formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing 41 may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber, and ceramic, or a combination thereof. The housing 41 can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.
The display 30 may be any of a variety of displays, such as a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display 30 can include an IMOD-based display, such as a bi-stable IMOD or SM-IMOD display as described herein.
In this example, the display device 40 includes a front light system 3215. The front light system 3215 may provide light to the interferometric modulator display when there is insufficient ambient light. The front light system 3215 may include one or more light sources and light-turning features configured to direct light from the light source(s) to the interferometric modulator display. The front light system 3215 may also include a wave guide and/or reflective surfaces, e.g., to direct light from the light source(s) into the wave guide. In some implementations, the front light system 3215 may be configured to provide red, green, blue, yellow, cyan, magenta and/or other colors of light, e.g., as described herein. Alternatively, or additionally, in some implementations the front light system 3215 may be configured to provide substantially white light.
The components of the display device 40 are schematically illustrated in
In this example, the processor 21 is configured to control the front light system 3215. According to some implementations, the processor 21 may be configured to control the front light system 3215 in accordance with one or more of the operational modes, including but not limited to FSC operational modes, described herein. In some such implementations, the processor 21 may be configured to control the front light system 3215 according to data from the sensor system 3210. For example, the processor 21 may be configured to select one of the operational modes described herein and to control the front light system 3215 and the display array 30 based, at least in part, on the ambient light data from the sensor system 3210. Alternatively, or additionally, the processor 21 may be configured to select one of the operational modes described herein for controlling the front light system 3215 and the display array 30 based on user input or other types of input described above. The processor 21, the array driver 22, the driver controller 29 and/or other devices also may control the display array 30 in accordance with one or more of the operational modes described herein. Accordingly, the processor 21, the array driver 22 and/or the driver controller 29 may be elements of a control system such as the control system 3205 of
The network interface 27 includes the antenna 43 and the transceiver 47 so that the display device 40 can communicate with one or more devices over a network. The network interface 27 also may have some processing capabilities to relieve, for example, data processing requirements of the processor 21. The antenna 43 can transmit and receive signals. In some implementations, the antenna 43 transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, and further implementations thereof. In some other implementations, the antenna 43 transmits and receives RF signals according to the Bluetooth® standard. In the case of a cellular telephone, the antenna 43 can be designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G, 4G or 5G technology. The transceiver 47 can pre-process the signals received from the antenna 43 so that they may be received by and further manipulated by the processor 21. The transceiver 47 also can process signals received from the processor 21 so that they may be transmitted from the display device 40 via the antenna 43.
In some implementations, the transceiver 47 can be replaced by a receiver. In addition, in some implementations, the network interface 27 can be replaced by an image source, which can store or generate image data to be sent to the processor 21. The processor 21 can control the overall operation of the display device 40. The processor 21 receives data, such as compressed image data from the network interface 27 or an image source, and processes the data into raw image data or into a format that can be readily processed into raw image data. The processor 21 can send the processed data to the driver controller 29 or to the frame buffer 28 for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation and gray-scale level.
The processor 21 can include a microcontroller, CPU, or logic unit to control operation of the display device 40. The conditioning hardware 52 may include amplifiers and filters for transmitting signals to the speaker 45, and for receiving signals from the microphone 46. The conditioning hardware 52 may be discrete components within the display device 40, or may be incorporated within the processor 21 or other components.
The driver controller 29 can take the raw image data generated by the processor 21 either directly from the processor 21 or from the frame buffer 28 and can re-format the raw image data appropriately for high speed transmission to the array driver 22. In some implementations, the driver controller 29 can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array 30. Then the driver controller 29 sends the formatted information to the array driver 22. Although a driver controller 29, such as an LCD controller, is often associated with the system processor 21 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor 21 as hardware, embedded in the processor 21 as software, or fully integrated in hardware with the array driver 22.
The array driver 22 can receive the formatted information from the driver controller 29 and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display's x-y matrix of display elements.
In some implementations, the driver controller 29, the array driver 22, and the display array 30 are appropriate for any of the types of displays described herein. For example, the driver controller 29 can be a conventional display controller or a bi-stable display controller (such as an IMOD display element controller). Additionally, the array driver 22 can be a conventional driver or a bi-stable display driver (such as an IMOD display element driver). Moreover, the display array 30 can be a conventional display array or a bi-stable display array (such as a display including an array of IMOD display elements). In some implementations, the driver controller 29 can be integrated with the array driver 22. Such an implementation can be useful in highly integrated systems, for example, mobile phones, portable-electronic devices, watches or small-area displays.
In some implementations, the input device 48 can be configured to allow, for example, a user to control the operation of the display device 40. The input device 48 can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, a touch-sensitive screen integrated with the display array 30, or a pressure- or heat-sensitive membrane. The microphone 46 can be configured as an input device for the display device 40. In some implementations, voice commands through the microphone 46 can be used for controlling operations of the display device 40.
The power supply 50 can include a variety of energy storage devices. For example, the power supply 50 can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. In implementations using a rechargeable battery, the rechargeable battery may be chargeable using power coming from, for example, a wall socket or a photovoltaic device or array. Alternatively, the rechargeable battery can be wirelessly chargeable. The power supply 50 also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply 50 also can be configured to receive power from a wall outlet.
In some implementations, control programmability resides in the driver controller 29 which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver 22. The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.
As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
The various illustrative logics, logical blocks, modules, circuits and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and steps described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system.
The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular steps and methods may be performed by circuitry that is specific to a given function.
In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus.
If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a non-transitory computer-readable medium. The steps of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a non-transitory computer-readable medium. Computer-readable media include both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage medium may be any available medium that may be accessed by a computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above also may be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a non-transitory machine readable medium and/or computer-readable medium, which may be incorporated into a computer program product.
Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. For example, although various implementations are described primarily in terms of reflective displays having red, blue and green subpixels, many implementations described herein could be used in reflective displays having other colors of subpixels, e.g., having violet, yellow-orange and yellow-green subpixels. Moreover, many implementations described herein could be used in reflective displays having more colors of subpixels, e.g., having subpixels corresponding to 4, 5 or more colors. Some such implementations may include subpixels corresponding to red, blue, green and yellow. Alternative implementations may include subpixels corresponding to red, blue, green, yellow and cyan. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of, e.g., an IMOD display element as implemented.
Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, a person having ordinary skill in the art will readily recognize that such operations need not be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.
This application claims priority to U.S. Provisional Patent Application No. 61/736,419 (attorney docket number QUALP084P/130049P1), filed on Dec. 12, 2012 and entitled “DYNAMIC ADAPTIVE ILLUMINATION CONTROL FOR FIELD SEQUENTIAL COLOR MODE TRANSITIONS,” which is hereby incorporated by reference. This application is a continuation-in-part of U.S. patent application Ser. No. 13/712,716 (attorney docket number QUALP165/122763), filed on Dec. 12, 2012 and entitled “FIELD-SEQUENTIAL COLOR MODE TRANSITIONS,” which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61736419 | Dec 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13712716 | Dec 2012 | US |
| Child | 13766045 | US |
