Method for driving an electro-optical display

Abstract

A method for driving an electro-optic display with multiple display pixels is provided, the method comprising receiving an image, converting the image into a YCbCr image, and processing the YCbCr image to generate a luminance image. The method further includes calculating changes in local regions of the YCbCr image to obtain a change map, and using the calculated changes to calculate an effect ratio map.

Description

[0001] Citation of relevant applications

[0002] This application relates to and claims priority to U.S. Provisional Application 63 / 122,936, filed December 8, 2020.

[0003] The full disclosure of the above application is incorporated herein by reference. Technical Field

[0004] This invention relates to a method for driving an electro-optic display. More specifically, this invention relates to a driving method for rendering images on an electro-optic display having color filters or color filter arrays. Background Technology

[0005] Electro-optic displays typically have a backplane with multiple pixel electrodes, each defining a pixel of the display; traditionally, a single common electrode extends across a large number of pixels, and the entire display is usually positioned on opposite sides of the electro-optic medium. Individual pixel electrodes can be driven directly (i.e., a separate conductor can be provided to each pixel electrode) or they can be driven in an active matrix manner familiar to those skilled in backplane technology. One method of achieving color in electro-optic displays is to equip such displays with a color filter array (CFA).

[0006] However, CFA-based displays, including both reflective and reflective displays, suffer from a loss of color space resolution due to subpixels. A typical CFA display has red, green, and blue filters. Therefore, if one of these primary colors is displayed on the display, only one-third or less of the display area is utilized (even less because of fill between subpixels). One pixel in the source image corresponds to one pixel in the display, with one filter at each pixel location. In a simple rendering process, if a red filter is present at a given pixel location, only the red channel value will be obtained from the same pixel in the source image. The same applies to green and blue filters. This can sometimes lead to the loss of fine color details, such as finely colored text. This problem becomes more pronounced when the display has a small color gamut, low dynamic range, or low resolution.

[0007] Therefore, a driving method is needed to preserve fine color details in CFA displays. Summary of the Invention

[0008] Therefore, on the one hand, the subject matter presented herein provides a method for driving an electro-optical display with multiple display pixels, the method may include receiving an image, converting the image into a YCbCr image, and processing the YCbCr image to generate a luminance image.

[0009] In some embodiments, the step of processing a YCbCr image to generate a luminance image may further include enhancing the output from the red, green, and blue channels. Enhancing the output from the red, green, and blue channels may include matching the luminance to the luminance of the target pixel.

[0010] In some other embodiments, the method may further include calculating changes in local regions of a YCbCr image to obtain a change map, wherein calculating changes may include calculating changes in each of the red, green, and blue channels of the YCbCr image, and calculating changes includes maximizing the changes in each of the red, green, and blue channels of the YCbCr image.

[0011] In some embodiments, the method may further include using the calculated changes to calculate an effect ratio, wherein calculating the effect ratio may include obtaining pixel values ​​from a brightness image.

[0012] In some other embodiments, calculating the effect ratio may include obtaining pixel values ​​from the received image.

[0013] In yet another embodiment, the electro-optic display configured to perform the method may include a color filter array. In some embodiments, the display may also include an electrophoretic material comprising a plurality of charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field. In some other embodiments, the charged particles and fluid are confined within a plurality of capsules or microunits. In yet another embodiment, the charged particles and fluid exist as a plurality of discrete droplets surrounded by a continuous phase, and may include a polymeric material. Attached Figure Description

[0014] Figure 1 This is a circuit diagram representing an electrophoresis display;

[0015] Figure 2 The circuit model of the electro-optic imaging layer is shown;

[0016] Figure 3 A cross-sectional view of an electro-optic display with a color filter array is shown;

[0017] Figure 4 This is a block diagram illustrating a driving method based on the subject matter disclosed herein;

[0018] Figure 5 An exemplary processing flow for rendering a color image for a CFA display is shown;

[0019] Figure 6 A variance plot is shown based on the subject matter disclosed herein; and

[0020] Figure 7The diagram shows the effect comparison based on the subject matter disclosed in this article. Detailed Implementation

[0021] This invention relates to methods for driving electro-optic displays, particularly bistable electro-optic displays, and apparatus for such methods. More specifically, the invention relates to driving methods that can allow for reduction of "ghosting" and edge effects, as well as reduction of flicker in such displays. The invention is particularly, but not exclusively, intended for use with particle-based electrophoretic displays, in which one or more types of charged particles are present in a fluid and move through the fluid under the influence of an electric field to alter the appearance of the display.

[0022] The term "electro-optic," used here in the context of materials or displays, refers to a material having first and second display states, where at least one optical property differs, and the material is changed from its first display state to its second display state by applying an electric field. While the optical property is typically color perceptible to the human eye, it can be another optical property, such as light transmission, reflection, emission, or, in the case of machine-reading displays, a pseudocolor in the sense of a change in reflectivity at electromagnetic wavelengths outside the visible light range.

[0023] The term "gray state" is used here in its conventional meaning in the imaging field, referring to a state between two extreme optical states of a pixel, but not necessarily a black-and-white transition between these two extreme states. For example, several IENK patents and publications mentioned below describe electrophoretic displays where the extreme states are white and dark blue, making the intermediate "gray state" actually a light blue. In fact, as already mentioned, a change in optical state may not be a color change at all. The terms "black" and "white" may be used below to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states that are not strictly black and white, such as the white and dark blue states mentioned above. The term "monochrome" may be used below to refer to a driving scheme that drives pixels only to their two extreme optical states without an intermediate gray state.

[0024] In the sense that a material has a solid outer surface, some electro-optic materials are solid, although the material may and often does indeed have internal spaces filled with liquid or gas. For convenience, such displays using solid electro-optic materials may be referred to as "solid-state electro-optic displays" below. Therefore, the term "solid-state electro-optic display" includes rotating dual-color component displays, encapsulated electrophoretic displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

[0025] The terms “bistable” and “bistable” are used herein in their conventional sense in the art, referring to a display comprising display elements having first and second display states, at least one optical characteristic of which differs such that, after any given element is driven to present its first or second display state using an addressing pulse of finite duration, the state will persist for at least several times (e.g., at least four times) the minimum duration of the addressing pulse required to change the state of the display element after the addressing pulse terminates. As shown in U.S. Patent No. 7,170,670, some particle-based electrophoretic displays supporting grayscale are stable not only in their extreme black and white states but also in intermediate gray states, as are some other types of electro-optical displays. Such displays are aptly referred to as “multistable” rather than bistable, but for convenience, the term “bistable” may be used herein to encompass both bistable and multistable displays.

[0026] The term "impulse" is used here in its conventional sense, referring to the integral of voltage with respect to time. However, some bistable electro-optic dielectrics are used as charge converters, and for such dielectrics, an alternative definition of impulse can be used: the integral of current with time (which equals the total applied charge). The appropriate definition of impulse should be used depending on whether the dielectric is used as a voltage-time impulse converter or a charge-impulse converter.

[0027] The majority of the following discussion focuses on methods for driving one or more pixels of an electro-optic display via a transition from an initial grayscale to a final grayscale (which may be different from or the same as the initial grayscale). The term "waveform" will be used to describe a curve of voltage over time used to achieve the transition from a particular initial grayscale to a particular final grayscale. Typically, such a waveform will include multiple waveform elements, where these elements are substantially rectangular (i.e., where a given element involves the application of a constant voltage over a time period); the elements may be referred to as "pulses" or "drive pulses." The term "drive scheme" refers to a set of waveforms sufficient to achieve all possible transitions between grayscales of a particular display. A display may utilize more than one drive scheme; for example, as taught in the aforementioned U.S. Patent No. 7,012,600, the drive scheme may need to be modified according to parameters such as the temperature of the display or the time it has been operating during its lifetime, and thus the display can provide multiple different drive schemes used at different temperatures, etc. A set of drive schemes used in this way may be referred to as a "set of related drive schemes." As described in several of the aforementioned MEDEOD applications, more than one driving scheme can be used simultaneously in different areas of the same display, and a group of driving schemes used in this manner can be referred to as a "group of simultaneous driving schemes".

[0028] Several types of electro-optic displays are known. One type of electro-optic display is the rotating bicolor component type, as described, for example, in U.S. Patent Nos. 5,808,783, 5,777,782, 5,760,761, 6,054,071, 6,055,091, 6,097,531, 6,128,124, 6,137,467, and 6,147,791 (although this type of display is often referred to as a "rotating bicolor sphere" display, the term "rotating bicolor component" is preferred as it is more accurate because in some of the patents mentioned above, the rotating component is not spherical). This display uses a number of small bodies (typically spherical or cylindrical) and internal dipoles, said bodies comprising two or more parts with different optical properties. These bodies are suspended within liquid-filled bubble chambers within a matrix, the bubble chambers being filled with liquid to allow the bodies to rotate freely. The appearance of a display is altered by applying an electric field to the display, thereby rotating the subject to various positions and changing which part of the subject is seen through the viewing surface. This type of electro-optic medium is typically bistable.

[0029] Another type of electro-optic display uses electrochromic media, such as those in the form of nanochromic films, which include electrodes formed at least partially of semiconductor metal oxides and multiple dye molecules attached to the electrodes capable of reversible color changes; see, for example, O'Regan, B. et al., Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24 (March 2002). See also Bach, U. et al., Adv. Mater., 2002, 14(11), 845. This type of nanochromic film is also described, for example, in U.S. Patent Nos. 6,301,038; 6,870,657 and 6,950,220. This type of medium is also typically bistable.

[0030] Another type of electro-optic display is the electrowetting display developed by Philips, which is described in Hayes, RA et al., “Video-Speed ​​Electronic Paper Based on Electrowetting,” Nature, 425, 383-385 (2003). U.S. Patent No. 7,420,549 shows that such an electrowetting display can be manufactured in a bistable manner.

[0031] Electro-optic displays, a type of display that has been the subject of intensive research and development for many years, are particle-based electrophoretic displays, in which multiple charged particles move through a fluid under the influence of an electric field. Compared to liquid crystal displays (LCDs), electrophoretic displays can offer advantages such as good brightness and contrast, wide viewing angles, state bistability, and low power consumption. However, long-term image quality issues have hindered their widespread use. For example, the particles constituting an electrophoretic display are prone to settling, resulting in a short lifespan for these displays.

[0032] As mentioned above, electrophoretic media require the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can be generated using a gaseous fluid; see, for example, Kitamura, T. et al., “Electricaltoner movement for electronic paper-like display,” IDW Japan, 2001, Paper HCS 1-1, and Yamaguchi, Y. et al., “Toner display using insulative particles charged triboelectrically,” IDW Japan, 2001, Paper AMD4-4. Also see U.S. Patent Nos. 7,321,459 and 7,236,291. When such gas-based electrophoretic media are used in a direction that allows particle settling, such as in signs where the media are arranged in a vertical plane, they are susceptible to the same type of problems as liquid-based electrophoretic media due to the same particle settling. In fact, particle sedimentation is more severe in gas-based electrophoretic media than in liquid-based electrophoretic media because the lower viscosity of gaseous suspensions allows electrophoretic particles to settle more quickly compared to liquids.

[0033] Numerous patents and applications transferred to or in the name of MIT and Einkel describe various techniques for encapsulating electrophoretic and other electro-optic media. These encapsulated media comprise a plurality of small capsules, each capsule comprising an inner phase and a capsule wall surrounding the inner phase, wherein the inner phase contains electrophoretically mobile particles in a fluid medium. Typically, the capsules themselves are held in a polymer binder to form a coherent layer located between two electrodes. Techniques described in these patents and applications include:

[0034] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0035] (b) Encapsulation, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0036] (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0037] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0038] (e) Thin films and sub-assemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0039] (f) Backplanes, adhesive layers and other auxiliary layers in displays, and methods thereof; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0040] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564;

[0041] (h) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348;

[0042] (i) Non-electrophoretic displays, as described in U.S. Patent No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160; and applications of packaging and microcell technologies other than displays; see, for example, U.S. Patent Application Publications Nos. 2015 / 0005720 and 2016 / 0012710; and

[0043] (j) A method for driving a display; see, for example, U.S. Patent Nos. 5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997; 6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600; 7,023,420; 7,034,783; 7,061,166; 7,061,662; 7,116,466; 7,119,772; 7,177,066; 7,193,625; 7,202,847; 7,242,514; 7,259,744; 7,304,787; 7 312,794; 7,327,511; 7,408,699; 7,453,445; 7,492,339; 7,528,822; 7,545,358; 7,583,251; 7,602,374; 7,612,760; 7,679,599; 7,679,813; 7,683 ,606;7,688,297;7,729,039;7,733,311;7,733,335;7,787,169;7,859,742;7,952,557;7,956,841;7,982,479;7,999,787;8,077,141;8,125,501 ; 8,139,050; 8,174,490; 8,243,013; 8,274,472; 8,289,250; 8,300,006; 8,305,341; 8,314,784; 8,373,649; 8,384,658; 8,456,414; 8,462,102; 8, 537,105;8,558,783;8,558,785;8,558,786;8,558,855;8,576,164;8,576,259;8,593,396;8,605,032;8,643,595;8,665,206;8,681,191;8,730 153; 8,810,525; 8,928,562; 8,928,641; 8,976,444; 9,013,394; 9,019,197; 9,019,198; 9,019,318; 9,082,352; 9,171,508; 9,218,773; 9,224,338; 9,224,342; 9,224,344; 9,230,492; 9,251,736; 9,262,973; 9,269,311; 9,299,294; 9,373,289; 9,390,066; 9,390,661; and 9,412,314; and U.S. Patent Application Publication No.2003 / 0102858; 2004 / 0246562; 2005 / 0253777; 2007 / 0070032; 2007 / 0076289; 2007 / 0091418; 2007 / 0103427; 2007 / 0176912; 2007 / 0296452; 2008 / 0024429; 2008 / 0024482; 2008 / 0136774; 2008 / 0169821; 2008 / 0218471; 2008 / 02911 29; 2008 / 0303780; 2009 / 0174651; 2009 / 0195568; 2009 / 0322721; 2010 / 0194733; 2010 / 0194789; 2010 / 0220121; 2010 / 0265561; 2010 / 0283804; 2011 / 0063314; 2011 / 0175875; 2011 / 0193840; 2011 / 0193841; 2011 / 0199671; 2011 / 02 21740; 2012 / 0001957; 2012 / 0098740; 2013 / 0063333; 2013 / 0194250; 2013 / 0249782; 2013 / 0321278; 2014 / 0009817; 2014 / 0085355; 2014 / 0204012; 2014 / 0218277; 2014 / 0240210; 2014 / 0240373; 2014 / 0253425; 2014 / 0292830; 2014 / 0293398; 2014 / 0333685; 2014 / 0340734; 2015 / 0070744; 2015 / 0097877; 2015 / 0109283; 2015 / 0213749; 2015 / 0213765; 2015 / 0221257; 2015 / 0262255; 2016 / 0071465; 2016 / 0078820; 2016 / 0093253; 2016 / 0140910; and 2016 / 0180777.

[0044] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thereby producing a so-called polymer dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and the discrete droplets of electrophoretic fluid within such a polymer dispersion electrophoretic display can be considered as capsules or microcapsules, even without a discrete capsule film associated with each individual droplet; see, for example, the aforementioned 2002 / 0131147. Therefore, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0045] One related type of electrophoretic display is the so-called "micro-unit electrophoretic display." In a micro-unit electrophoretic display, charged particles and suspended fluid are not encapsulated within microcapsules, but rather held within multiple cavities formed within a carrier medium (e.g., a polymer film). See, for example, International Application Publication No. WO 02 / 01281 and U.S. Application No. 2002 / 0075556, both assigned to Sipix Imaging.

[0046] Many of the aforementioned Einkel and MIT patents and applications also consider microcell electrophoretic displays and polymer dispersion electrophoretic displays. The term "encapsulated electrophoretic display" can refer to all such display types, and can also be collectively referred to as "microcavity electrophoretic display" to encompass the morphology of the entire wall.

[0047] Another type of electro-optic display is the electrowetting display developed by Philips, described in Hayes, RA et al., “Video-Speed ​​Electronic Paper Based on Electrowetting,” Nature, 425, 383-385 (2003). It is shown in co-pending application sequence No. 10 / 711,802, filed October 6, 2004, that this electrowetting display can be fabricated to be bistable.

[0048] Other types of electro-optic materials can also be used. Of particular interest are bistable ferroelectric liquid crystal displays (FLCs), which are known in the art and exhibit residual voltage behavior.

[0049] While electrophoretic media can be opaque (because, for example, in many electrophoretic media, particles essentially block visible light from passing through the display) and operate in reflective mode, some electrophoretic displays can be made to operate in a so-called "shutter mode," in which one display state is substantially opaque and the other is transmissive. See, for example, U.S. Patent Nos. 6,130,774 and 6,172,798 and U.S. Patent Nos. 5,872,552, 6,144,361, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, similar to electrophoretic displays but dependent on changes in electric field strength, can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optic displays are also capable of operating in shutter mode.

[0050] High-resolution displays can include addressable, individual pixels that are independent of interference from adjacent pixels. One way to obtain such pixels is to provide an array of nonlinear elements (such as transistors or diodes), with at least one nonlinear element associated with each pixel to produce an "active matrix" display. The addressing or pixel electrode used to address a pixel is connected to an appropriate voltage source via the associated nonlinear element. When the nonlinear element is a transistor, the pixel electrode can be connected to the drain of the transistor, and this arrangement will be used in the description below, although it is essentially arbitrary and the pixel electrode can be connected to the source of the transistor. In a high-resolution array, pixels can be arranged in a two-dimensional array of rows and columns, such that any particular pixel is uniquely defined by the intersection of a particular row and a particular column. The sources of all transistors in each column can be connected to a single column electrode, while the gates of all transistors in each row can be connected to a single row electrode; furthermore, the source-to-row and gate-to-column arrangements can be reversed as needed.

[0051] The display can be written line by line. Row electrodes are connected to a row driver that applies a voltage to the selected row electrode, for example, to ensure that all transistors in the selected row are turned on, while applying a voltage to all other rows, for example, to ensure that all transistors in the unselected rows remain off. Column electrodes are connected to a column driver that applies a voltage to each column electrode, selected to drive the pixels in the selected row to their desired optical state. (The aforementioned voltage is relative to a common front electrode, which may be positioned on the opposite side of the electro-optic medium from the nonlinear array and extend across the entire display. As is known in the art, voltage is relative and is a measurement of the charge difference between two points. One voltage value is relative to another voltage value. For example, zero voltage (“0V”) means there is no voltage difference relative to another voltage.) After a pre-selection interval called the “row address time,” the selected row is deselected, another row is selected, and the voltage on the column driver is changed so that the next row of the display is written.

[0052] However, in use, certain waveforms may produce residual voltages on the pixels of the electro-optic display, and as is evident from the discussion above, these residual voltages produce several unwanted optical effects, which are generally undesirable.

[0053] As described herein, an “offset” in an optical state associated with an addressing pulse refers to a situation where a particular addressing pulse is first applied to an electro-optic display resulting in a first optical state (e.g., a first grayscale), and the same addressing pulse is subsequently applied to the electro-optic display resulting in a second optical state (e.g., a second grayscale). Since the voltage applied to a pixel of the electro-optic display during the application of the addressing pulse comprises the sum of the residual voltage and the addressing pulse voltage, the residual voltage may cause an offset in the optical state.

[0054] The "drift" of the optical state of a display over time refers to the change in the optical state of an electro-optic display when the display is stationary (e.g., during a period when no addressing pulse is applied to the display). Since the optical state of a pixel may depend on the pixel's residual voltage, and the residual voltage of a pixel may decay over time, residual voltage can cause the optical state to drift.

[0055] As mentioned above, "ghosting" refers to the situation where traces of a previous image remain visible after an electro-optic display has been rewritten. Residual voltage can cause "edge ghosting," a type of ghosting where the outline (edge) of a portion of the previous image remains visible.

[0056] Exemplary EPD

[0057] Figure 1A schematic diagram of a pixel 100 of an electro-optic display according to the subject matter presented herein is shown. Pixel 100 may include an imaging film 110. In some embodiments, the imaging film 110 may be bistable. In some embodiments, the imaging film 110 may include, but is not limited to, an encapsulated electrophoretic imaging film, which may include, for example, charged pigment particles.

[0058] An imaging film 110 may be disposed between the front electrode 102 and the rear electrode 104. The front electrode 102 may be formed between the imaging film and the front of the display. In some embodiments, the front electrode 102 may be transparent. In some embodiments, the front electrode 102 may be formed of any suitable transparent material, including but not limited to indium tin oxide (ITO). The rear electrode 104 may be formed opposite to the front electrode 102. In some embodiments, a parasitic capacitance (not shown) may be formed between the front electrode 102 and the rear electrode 104.

[0059] Pixel 100 may be one of a plurality of pixels. These pixels may be arranged in a two-dimensional array of rows and columns to form a matrix, such that any particular pixel is uniquely defined by the intersection of a particular row and a particular column. In some embodiments, the matrix of pixels may be an “active matrix” in which each pixel is associated with at least one nonlinear circuit element 120. The nonlinear circuit element 120 may be coupled between a backplane electrode 104 and an address electrode 108. In some embodiments, the nonlinear element 120 may include diodes and / or transistors, including but not limited to metal-oxide-semiconductor field-effect transistors (MOSFETs). The drain (or source) of the MOSFET may be coupled to the backplane electrode 104, the source (or drain) of the MOSFET may be coupled to the address electrode 108, and the gate of the MOSFET may be coupled to a driver electrode 106 configured to control the activation and deactivation of the MOSFET. (For simplicity, the terminal of the MOSFET coupled to the backplane electrode 104 will be referred to as the drain of the MOSFET, and the terminal of the MOSFET coupled to the address electrode 108 will be referred to as the source of the MOSFET. However, those skilled in the art will recognize that in some embodiments, the source and drain of the MOSFET may be interchanged.)

[0060] In some embodiments of the active matrix, the addressing electrodes 108 of all pixels in each column may be connected to the same column electrode, and the driver electrodes 106 of all pixels in each row may be connected to the same row electrode. The row electrodes may be connected to a row driver that can select one or more rows of pixels by applying a voltage sufficient to activate the nonlinear elements 120 of all pixels 100 in the selected row. The column electrodes may be connected to a column driver that can apply a voltage suitable for driving the pixel to a desired optical state on the addressing electrodes 106 of the selected (activated) pixel. The voltage applied to the addressing electrodes 108 may be relative to the voltage applied to the front panel electrodes 102 of the pixel (e.g., approximately zero volts). In some embodiments, the front panel electrodes 102 of all pixels in the active matrix may be coupled to a common electrode.

[0061] In some embodiments, the pixels 100 of the active matrix can be written row by row. For example, a row driver can select a row of pixels, and a column driver can apply a voltage to the pixel corresponding to the desired optical state of that row of pixels. After a pre-selection interval known as "row address time," the selected row can be deselected, another row can be selected, and the voltage on the column driver can be changed so that another row of the display is written.

[0062] Figure 2 A circuit model of an electro-optic imaging layer 110, arranged between a front electrode 102 and a rear electrode 104, is shown according to the subject matter presented herein. Resistors 202 and 204 may represent the resistance and capacitance of the electro-optic imaging layer 110, the front electrode 102, and the rear electrode 104 (including any adhesive layers). Resistors 212 and 214 may represent the resistance and capacitance of the laminated adhesive layer. Capacitor 216 may represent the capacitance that may be formed between the front electrode 102 and the rear electrode 104, for example, at the interfacial contact region between layers, such as the interface between the imaging layer and the laminated adhesive layer and / or the interface between the laminated adhesive layer and the backplane electrode. The voltage Vi on the imaging film 110 of a pixel may include the residual voltage of the pixel.

[0063] During use, it is hoped that... Figure 1 and Figure 2The electro-optical display shown updates to subsequent images without flickering the display background. However, a direct approach using empty transitions in image updates with background-to-background color (e.g., white-to-white, or black-to-black) waveforms can lead to the accumulation of edge artifacts (e.g., halos). In monochrome electro-optical displays, edge artifacts can be reduced by using specialized waveforms (e.g., cutoff waveforms). However, maintaining color quality and contrast can sometimes be challenging in electro-optical displays such as electrophoretic displays (EPDs) that generate colors using color filter arrays (CFAs).

[0064] Figure 3 A cross-sectional view of a CFA-based colored EPD is shown, based on the subject matter disclosed herein. Figure 3 As shown, the color electrophoretic display (generally designated 300) includes a backplate 302 carrying a plurality of pixel electrodes 304. The backplate 302 may be laminated with an inverted front-plane laminate, which may include a monochromatic electrophoretic dielectric layer 306 having black and white extreme optical states, an adhesive layer 308, a color filter array 310 having red, green and blue regions aligned with the pixel electrodes 304, a substantially transparent conductive layer 312 (typically formed of indium tin oxide), and a front protective layer 314.

[0065] In fact, changes in local regions of an image can be used to preserve fine color details on a CFA display. The topic presented in this article uses subpixel rendering or LVS rendering based on local changes. The process involves taking the color changes of a local region of a given input image and then determining whether that region is a detail-preserving area to better represent fine color details. Now refer to... Figure 4 An exemplary method 400 for driving a CFA display is presented in accordance with the subject matter disclosed herein.

[0066] In some embodiments, the LVS rendering algorithm may first take a source image (e.g., an sRGB image or img_sRGB) and a subpixel location map (e.g., imMASK) defining which pixel location has which color filter as input. Subsequently, in Figure 4 Step 402 can use industry-standard methods, such as the linear transformation defined in ITU-R Recommendation BT.601, to convert the sRGB image to a YCbCr image.

[0067] Next, in Figure 4 Step 404 can be used to define the luminance image (e.g., img_luma) according to the exemplary algorithm presented below:

[0068] For k = 1:3

[0069] img_luma(imMASK==k)=img_Y(imMASK==k)*c_boost_RGB(k)

[0070] Finish

[0071] Where `img_Y` is the Y channel image from a YCbCr image, and `c_boost_RGB` is a list of three coefficients used to enhance the output of the red, green, and blue channels. This enhancement can be ideal for matching the brightness of the target pixels because the transparency differs between the three channels. These coefficients are adjustable parameters designed to balance the image brightness. Figure 6 As shown.

[0072] After creating the brightness image, in step 406, local changes can be calculated to generate a change map of the image (see [link]). Figure 6 For each channel in YCbCr, calculations can be performed in a localized region. For illustrative purposes, a localized region size of 3×3 pixels is used here, for example, as shown. Figure 5 As shown. An exemplary algorithm for generating the change map is shown below:

[0073] For each channel in YCbCr:

[0074] For each local region:

[0075] Calculate the average pixel value.

[0076] For each pixel:

[0077] Subtract the average,

[0078] Take the absolute value.

[0079] Take the square root.

[0080] Finish

[0081] Calculate the average of the square root values ​​of all pixels. This is conceptually...

[0082] Changes in local areas.

[0083] Finish

[0084] Finish

[0085] For each pixel:

[0086] Take the maximum change among the three channels

[0087] Finish

[0088] In some embodiments, for each channel in YCbCr and for each local region as defined above, the average pixel value can be calculated by subtracting the average from each pixel, taking the absolute value, and then taking the square root of that value. The pixel value can be defined as a value describing how bright a pixel is and / or what color it should be. In the simplest case of a binary image, the pixel value can be a 1-bit number representing the foreground or background. For grayscale images, the pixel value can be a single number representing the pixel's brightness. For example, for a byte image, this number can be stored as an 8-bit integer, giving a range of possible values ​​from 0 to 255, where zero represents black and 255 represents white. Values ​​in between constitute different shades of gray. To represent a color image, separate red, green, and blue components can be assigned to each pixel, so the pixel value can actually be a vector of three numbers. Typically, these three distinct components can be stored as three separate grayscale images, called color planes (one each for red, green, and blue), which must be recombinated during display or processing. The variation in a local region can then be calculated by averaging the square root values ​​of all pixels in the local region.

[0089] In alternative embodiments, instead of taking the square root of the absolute difference between a pixel value and its neighboring averages, standard deviation, variance, or any other method can be used to define local variation. Similarly, when pooling variations across the three channels, any form can be used, such as the average and median, instead of the maximum. Variation can be calculated across all three channels together, rather than calculating it for each channel individually.

[0090] Next, in step 408, a comparison chart can be generated, such as... Figure 7 As shown, the effect ratio is configured to define the detail retention effect for each display pixel. The effect ratio for a given pixel is defined in a piecewise linear function as shown below:

[0091] r = (v - k1) / (k2 - k1)

[0092] If r > 1, then r = 1

[0093] If r < 0, then r = 0

[0094] Where r is the effect ratio, v is the change calculated above, and k1 and k2 are adjustable parameters.

[0095] If full effect is selected (r=1), the pixel value is taken from the `img_luma` at the specified pixel position. If no effect is selected (r=0), the pixel value is taken from the corresponding color channel at the specified pixel position in `img_sRGB`. If the effect is between 0 and 1, the pixel value is linearly interpolated.

[0096] Please note that the effect ratio can be calculated in any linear or nonlinear function that takes a change as input.

[0097] It will be apparent to those skilled in the art that various changes and modifications can be made to the specific embodiments of the present invention described above without departing from the scope of the invention. Therefore, the entire foregoing description should be interpreted as illustrative rather than restrictive.

Claims

1. A method for driving an electro-optic display having a plurality of display pixels, the method comprising: Receive image; Convert the image to a YCbCr image; The YCbCr image is processed to generate a luminance image; Calculate the changes in brightness or color, or both brightness and color, in local regions of the YCbCr image to obtain a change map; and The calculated changes are used to calculate an effect ratio map, wherein the effect ratio map is configured to define the detail retention effect of each display pixel, and the effect ratio map represents the degree of luminance dominance and chrominance dominance of each display pixel, wherein if the effect ratio is 1, i.e., the degree of luminance dominance is maximum, the pixel value of the display pixel is taken from the luminance image at the specified pixel location; if the effect ratio is 0, i.e., the degree of chrominance dominance is maximum, the pixel value is taken from the corresponding color channel at the specified pixel location in the received image; and if the effect ratio is between 0 and 1, the pixel value is linearly interpolated.

2. The method of claim 1, wherein, The step of processing the YCbCr image to generate a luminance image also includes enhancing the output from the red, green, and blue channels.

3. The method of claim 2, wherein, Enhancing the output from the red, green, and blue channels involves matching the brightness to the brightness of the target pixel.

4. The method of claim 1, wherein, Calculating the changes includes calculating the changes in each of the red, green, and blue channels of the YCbCr image.

5. The method of claim 4, wherein, Calculating the changes involves maximizing the changes in each of the red, green, and blue channels of the YCbCr image.

6. An electro-optic display configured to perform the method of claim 1, further comprising a color filter array.

7. The electro-optic display of claim 6, comprising an electrophoretic material, the electrophoretic material comprising a plurality of charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field.

8. The electro-optical display according to claim 7, wherein, The charged particles and the fluid are confined within multiple capsules or micro-units.

9. The electro-optic display according to claim 7, wherein, The charged particles and the fluid exist as multiple discrete droplets surrounded by a continuous phase containing polymer material.

10. A display controller capable of controlling the operation of a bistable electro-optic display, the controller being configured to perform a driving method for operating the display, the method comprising: Receive image; Convert the image to a YCbCr image; The YCbCr image is processed to generate a luminance image; Calculate the changes in brightness or color, or both brightness and color, in local regions of the YCbCr image to obtain a change map; and The calculated changes are used to calculate an effect ratio map, wherein the effect ratio map is configured to define the detail retention effect of each display pixel, and the effect ratio map represents the degree of luminance dominance and chrominance dominance of each display pixel, wherein if the effect ratio is 1, i.e., the degree of luminance dominance is maximum, the pixel value of the display pixel is taken from the luminance image at the specified pixel location; if the effect ratio is 0, i.e., the degree of chrominance dominance is maximum, the pixel value is taken from the corresponding color channel at the specified pixel location in the received image; and if the effect ratio is between 0 and 1, the pixel value is linearly interpolated.

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