Patent Application
20140192079
This disclosure relates to the field of temporal dithering of color channels in displays and more particularly to electromechanical systems based display devices.
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.
Digital images are commonly quantized into a plurality of grayscale or color levels for printing or displaying the digital images on a medium with limited tonescale resolution. Various techniques have been developed to reduce errors associated with quantization and to create the illusion of continuous-tone imagery in printed and displayed images.
Halftoning techniques have been developed to create the illusion of continuous-tone images on display devices that display a finite number of tones (for example, colors). For example, halftoning techniques can be used to display or print high resolution images (e.g. images having 24 bits per pixel, 8 bits per color channel) on a medium (e.g. a display device) having lower resolution (e.g. 2 or 4 bits per color channel). Examples of common halftoning techniques include spatial or temporal dithering and error diffusion.
The systems, methods and devices of this 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 an apparatus comprising a display device having a plurality of display pixels and a processor configured to communicate with the display device. Each display pixel is configured to display a plurality of colors in a color space associated with the display device. In various implementations, a color in the color space of the display device can represent tone, grayscale, hue, chroma, saturation, brightness, lightness, luminance, correlated color temperature, dominant wavelength, or a coordinate in the color space. The processor is configured to process an image data including a plurality of image pixels for display by the display device. The processor is further configured to map the image data to the plurality of display pixels to provide data associated with each color plane in the color space associated with the display device. The color plane data includes a color value for each display pixel in the display device. The processor is configured to identify display pixels having spatial frequencies below a threshold for each color plane. For each of the identified display pixels in each color plane, the processor is configured to calculate a dither visibility score based at least in part on comparison of the color value for the display pixel and a dither visibility function for the color plane and determine an accumulated dither visibility score for each color plane. The processor is configured to apply temporal dither to a subset of the plurality of color planes based on the determined accumulated dither visibility scores. In various implementations, the temporal dither can include a Floyd-Steinberg dither.
In some implementations, the processor can be configured to apply temporal dither to the color plane having the highest dither. In various implementations, the processor is configured to apply temporal dither to the color plane determined to have the second-highest accumulated temporal dither visibility score. In various implementations, the temporal dither applied to the color plane determined to have the second-highest accumulated dither visibility score is less than the temporal dither applied to color plane determined to have the highest accumulated dither visibility score. In some implementations, the temporal dither applied to the color plane determined to have the highest accumulated dither visibility score can be a 3-bit temporal dither, and the temporal dither applied to the color plane determined to have the second-highest accumulated dither visibility score can be a 1-bit temporal dither. In various implementations, the processor can be configured to apply temporal dither to only the color plane determined to have the highest accumulated dither visibility score. In various implementations, the dither visibility function can be stored as a look-up table (LUT). In some implementations, the plurality of color planes can include at least two color planes selected from the group consisting of a red color plane, a green color plane, and a blue color plane. In various implementations, the plurality of color planes can include a first color plane configured to display a first hue of a color and a second color plane configured to display a second hue of the color, the first hue different from the second hue. In various implementations, the display device can have a frame refresh rate less than 60 Hz. In various implementations, the display device can be a reflective display device. In some implementations, each display pixel can include at least three or four subpixels. In various implementations, each subpixel can include a movable mirror element. In some implementations, the movable mirror elements of two different subpixels in each pixel can have different reflective areas. In various implementations, each subpixel can be configured to display two bit color in the color space associated with the display device.
Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus comprising a means for displaying image data including a plurality of image pixels and a means for processing the image data for display by the displaying means. The displaying means have a plurality of display pixels that are configured to display a plurality of colors in a color space associated with the displaying means. The processing means is configured to map the image data to the plurality of display pixels to provide data associated with each color plane in the color space associated with the displaying means. The color plane data includes a color value for each display pixel in the displaying means. The processing means is configured to identify display pixels having spatial frequencies below a threshold for each color plane. For each of the identified display pixels in each color plane, the processing means is configured to calculate a dither visibility score based at least in part on comparison of the color value for the display pixel and a dither visibility function for the color plane and determine an accumulated dither visibility score for each color plane. The processing means is configured to apply temporal dither to a subset of the plurality of color planes based on the determined accumulated dither visibility scores. In various implementations, the displaying means can include a reflective display device. In various implementations, the processing means can include a processor in communication with the displaying means. In various implementations, the processing means can include at least one of an accumulator and a comparator.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for adaptively applying temporal dithering to display an input image having reduced dither visibility on a display device having a plurality of display pixels. Each display pixel is configured to display a plurality of colors in a color space associated with the display device. The method is performed in its entirety by a physical computing device. The method comprises mapping the input image to the plurality of display pixels to provide data associated with each color plane data for each color in the color space associated with the display device. The color plane data includes a color value for each display pixel in the display device. The method comprises identifying display pixels having spatial frequencies below a threshold for each color plane. The method further comprises calculating a dither visibility score for each of the identified pixels in each color plane. The dither visibility score is calculated based at least in part on comparison of the color value for the display pixel and a dither visibility function for the color plane. The method comprises determining an accumulated dither visibility score for each color plane and applying temporal dither to a subset of the plurality of color planes based on the determined accumulated dither visibility scores.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer storage medium comprising instructions that when executed by a processor cause the processor to perform a method for adaptively applying temporal dithering to display an input image having reduced dither visibility on a display device having a plurality of display pixels. Each display pixel is configured to display a plurality of colors in a color space associated with the display device. The method comprises mapping the input image to the plurality of display pixels to provide data associated with each color plane data for each color in the color space associated with the display device. The color plane data includes a color value for each display pixel in the display device. The method comprises identifying display pixels having spatial frequencies below a threshold for each color plane. The method further comprises calculating a dither visibility score for each of the identified pixels in each color plane. The dither visibility score is calculated based at least in part on comparison of the color value for the display pixel and a dither visibility function for the color plane. The method comprises determining an accumulated dither visibility score for each color plane and applying temporal dither to a subset of the plurality of color planes based on the determined accumulated dither visibility scores.
Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Although the examples provided in this disclosure are primarily described in terms of EMS and MEMS-based displays the concepts provided herein may apply to other types of displays such as liquid crystal displays, organic light-emitting diode (“OLED”) displays, and field emission displays. Other features, aspects, and advantages will become apparent from the description, the drawings and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
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.
The systems and methods described herein can be used to display high resolution color images (e.g. images having 24 bits per pixel, 8 bits per color channel) on a display device including a plurality of display pixels having lower color resolution (for example, 2 or 4 bits per color channel). Each display pixel in the display device can display a color in a color space associated with the display device with a color resolution associated with a number of bits (for example, 2 or 4 bits). To display high resolution color images (for example, with 8 bits per color channel or 256 color levels per color channel) on a display device having a lower color resolution, a method referred to as color quantization can be used to reduce the number of possible distinct color levels per channel (for example, 256 color levels per channel) in the image to the number of possible distinct color levels that can be produced by the display device (for example, 4 or 16 color levels per channel).
The color quantization process can be associated with a quantization error which can result in visual artifacts that can degrade the visual quality of the displayed image. For example, color quantized images can appear speckled or grainy. Techniques such as dithering can be used to enhance the visual quality of the displayed image. One form of dithering that can be used to enhance the visual quality of the displayed image is temporal dithering. In temporal dithering, a display pixel can be configured to display different color values from the display color space at different times to create the illusion of color depth.
Systems and methods that can apply adaptive temporal dither based on the content of a given input image as described herein can more fully exploit the benefit of applying temporal dither for a given input image. An implementation of an adaptive temporal dithering scheme includes identifying smooth portions of the display image. In various implementations, this can be achieved by identifying display pixels that are associated with low spatial frequencies in each color plane. A dither visibility score can be computed for each of the identified display pixels. The dither visibility score can quantitatively represent an amount of visible dither noise in the smooth portions of the image for each color plane. An accumulated dither visibility score can be computed for each color plane by aggregating the dither visibility score for the identified display pixels in the color plane. A higher accumulated dither visibility score is generally associated with higher visibility of dither artifacts (for example, graininess or noisiness). Thus, temporal dither can be applied adaptively based on the image content. For instance, temporal dither can be applied to the color plane that is determined to have the highest accumulated dither visibility score, which may reduce the visibility of dither artifacts.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. It is possible to display high resolution continuous-tone digital images on display devices having low native resolution that can display a limited number of tones or color levels by using halftoning to render intermediate tones that cannot be natively displayed by the display device. However, the halftoning process trades-off spatial resolution for tone resolution. For example, if the pixel size of the display device is not small enough to be invisible to the human eye, halftone patterns for various tones generally will be visible. For image content that is smooth (or without texture), the halftone pattern can be perceived as dither noise on a solid background. As discussed above, temporal dithering can advantageously reduce the visible dither noise. However, temporal dithering may not reduce the dither noise equally for all portion of the displayed image. For example, temporal dithering can enhance the visual quality of smooth portions of the displayed image to a greater extent than the edges or the portions of the displayed image having high frequency content. Additionally, due to limitations on processor speed, it may not be practical to temporally dither all the color planes displayed by the display device. Thus, applying temporal dither to only those regions of the displayed image and/or only those color planes that have the highest amounts of visible dither noise, as discussed in certain implementations of the adaptive temporal dither scheme described herein, can provide the benefits of temporal dithering while making efficient use of processor speed and other available hardware resources. Accordingly, certain implementations of the adaptive temporal dithering scheme discussed herein can be used to display high resolution continuous tone images on low resolution display devices constrained by processor speeds and other hardware resources with reduced dither visibility.
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.
Various implementations of the display device 500 can include a reflective display device. In some such implementations, the subpixels 501a-501d can include a reflective mirror that can be moved between different positions to display black (or no color) or to display one or more colors in the display device color space. The reflective mirror can form a portion of the active area of the subpixel. In various implementations, the subpixels 501a-501d can include interferometric modulators similar to the IMOD display elements 12 discussed above. The display device illustrated in
A digital color image includes a plurality of image pixels and each of the plurality of image pixels includes a combination of colors. The color of an image pixel can be represented by coefficients in a coordinate system in a multi-dimensional color space. For example, each image pixel of a digital color image can be represented by a number of coefficients (such as three or four) in a color space (e.g., standard RGB (sRGB) color space, International Commission on Illumination (CIE) XYZ color space, etc.). The coefficients can represent weights or levels for each of the color channels that make up the color space. For example, in various implementations, the coefficients can represent each of the three color channels red (R), green (G), and blue (B) in the sRGB color space. As another example, the coefficients can represent the color channels cyan (C), magenta (M), yellow (Y) and black (K) in a color space that uses CMYK color model. For further discussion of
A high-tonescale-resolution color image can have a number of bits, n, representing each color channel making up the image pixel. In various implementations, the number of bits, n, can be, for example, 2, 4, 8, 16 or 24. When a high-tonescale-resolution image (such as an image having 8, 16 or 24 bits per color channel) is displayed on a display device having lower color resolution (for example, 2 or 4 bits per color channel), each color channel may be quantized to reduce the number of color levels to the number of bits displayable by each color channel. The quantization process can be associated with a quantization error. A halftone pattern can be used to provide intermediate color levels and create the illusion of continuous tone. If the size of the display pixels is not small enough to be invisible to the human eye, the quantization error and/or the halftone pattern can be visible and affect the visual quality of the displayed image. For example, the quantized and halftoned images may appear grainy or speckled. Various implementations of a display device having a BWG pixel architecture, such as, the display device 500 illustrated in
In various implementations, temporal dithering can be used to reduce the dither visibility. Temporal dithering refers to a modulation technique to render different pixel values in different time intervals. In temporal dithering, a display pixel can be configured to display different color values from the display color space at different times to create the illusion of color depth. If used, temporal dither can be applied to one, some, or all of the color channels of the display device. Temporal dither algorithms include Floyd-Steinberg dither algorithms. In some implementations of the display device 500, a 7-level temporal dither can be applied to the subpixels 501b that display a first shade or hue of green (G) and/or to the subpixels 501d that display a second shade or hue of green (g). The subpixels that are not temporally dithered can be halftoned with 3-level error diffusion. Although, temporal dithering can reduce dither visibility, it may not do so consistently for different portions of the image. In certain implementations of display devices where each display pixel can be individually controlled, temporal dithering may be performed on a pixel level. In such implementations, each pixel can be individually temporally dithered. In some other implementations of display devices, a group of pixels that display the same color in the display device color space (for example, a color plane or a portion of the color plane) can be collectively temporally dithered. Such a scheme for applying a temporal dither collectively to an entire group of pixels displaying the same color can be useful in reducing the complexity of drivers and processors that are used to control the display pixels. Furthermore, applying a temporal dither collectively to an entire group of pixels displaying the same color can be advantageous in realizing high-speed display devices having fast refresh rate.
Temporal dithering can be more beneficial in a display device having a fast refresh rate since flickering between sub-frames can be reduced in such a display device. For a majority of human eyes, flicker starts to appear when the frame rate drops below about 60 Hz. Various implementations of the display device 500 illustrated in
Accordingly, implementations of the adaptive temporal dither systems and methods described herein can determine which color plane (or planes) to temporally dither when the refresh rate is too low to temporally dither all color planes. The implementations of the adaptive temporal dither systems and methods described herein can advantageously apply temporal dither to an entire or a portion of color plane when it may not be practical to apply temporal dither to each individual display pixel. In various implementations, temporal dither can be applied to one, two, or all the color planes of the display device. In various implementations, temporal dither can be applied to a portion of one, two, or all the color planes of the display device. Additionally, implementations of the adaptive temporal dither systems and methods discussed herein can switch the color plane to which temporal dithering is applied (for example between a color plane having a first shade or hue of green (G) and a color plane having a second shade or hue of green (g)) per image frame, based at least partly on the image content so as to reduce dither visibility consistently for different portions of the image. As such, the adaptive temporal dither systems and methods can more fully exploit the benefit of temporal dither for a given input image. The adaptive temporal dither systems and methods discussed herein can be used for a wide variety of displays and are not limited to the BWG display architecture illustrated in
The dither visibility can depend at least in part on the input tone and the quantization levels of the display device. Dither visibility can be quantified using models of the human visual system (HVS). Without subscribing to any particular theory, generally the HVS has a low-pass effect, wherein the HVS response falls off rapidly with increasing spatial frequency. The HVS is also generally less sensitive to chrominance than luminance. The HVS response functions can be used to quantify the dither visibility.
Dither visibility can be quantified in many ways. In one method used to quantify dither visibility, x and y are the continuous tone and halftoned patches respectively, and Hy and Hc are the luminance and chrominance responses of the HVS respectively. The dither visibility in each color plane can be calculated by converting the continuous tone and halftoned patches in the color space of the display device to a perceptually linear color space (e.g., the linearized CIELab color space), which can be used as a reference. The components of the linearized CIELab color space are one luminance channel and 2 chrominance channels. The visible error, e, between the continuous tone and the halftoned patches for vectorized versions of x and y can be calculated from the following equation:
where H is a block matrix with the HVS luminance and chrominance responses, and C transforms the display device color space values to linearized CIELab space. The matrix F is the discrete Fourier transform matrix and transforms the color space values to frequency space, because the luminance and chrominance responses (H) are in frequency space. In some implementations, the error e can be used to measure the dither visibility. Higher values of dither visibility represent higher errors perceived by the HVS.
For each color plane:
The accumulated dither visibility score for each color plane that is accumulated in the accumulator can be compared using a comparator, as shown in block 730, and the color plane with the highest dither visibility score can be identified. In various implementations, temporal dither can be applied to a subset of the plurality of color planes based on the determined accumulated dither visibility scores as shown in block 735. As an example, in some implementations, temporal dither can be applied to the color plane with the highest accumulated dither visibility scores. For example, if the color plane G has a higher accumulated dither visibility score than either the R or B color planes, temporal dither is applied to the G color plane. Although, the method illustrated in the flowchart 700 is for the case of three color planes R, G, and B, in other implementations, the method can be applied to two color planes (for example, color plane G and color plane g) or to four or more color planes.
If the device refresh rate can support temporal dither of additional color channels, then temporal dither can be additionally applied to the color plane having the second highest accumulated dither visibility score, and so forth. In some implementations, the amount of temporal dither applied to the two color planes can be the same. In other implementations, the amount of temporal dither applied to the two color planes can be different. For example, in some implementations, a higher temporal dither (for example, a 3-bit temporal dither) can be applied to the color plane having the highest accumulated dither visibility score and a lower temporal dither (for example, a 1-bit temporal dither) can be applied to the color plane having the second highest accumulated dither visibility score. In various implementations, temporal dithering can be adaptively applied between two different color planes (for example, a color plane having the highest and the second highest dither visibility score) on a frame-by-frame basis based on the image content. For example, in a display device having the four color channel BWG pixel architecture described in
In various implementations, the method illustrated in flowcharts 700, 800 and 810 can be performed by a hardware processor included in the display device (for example, the processor 21 described below with reference to
The display device 40 includes a housing 41, a display 30, an antenna 43, a speaker 45, an input device 48 and a microphone 46. The housing 41 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, including a bi-stable or analog display, as described herein. The display 30 also can be configured to include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display 30 can include an IMOD-based display, as described herein. In various implementations the display 30 can be a RGB display device or a reflective display device with a four color channel pixel architecture as shown in
The components of the display device 40 are schematically illustrated in
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), NEV-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 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 computer-readable medium. Computer-readable media includes 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 media may be any available media that may be accessed by a computer. By way of example, and not limitation, such 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 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 machine readable medium and 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. 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.
