RU2754485C1 - Electrooptical displays and methods for actuation thereof - Google Patents

Abstract

FIELD: displays.

SUBSTANCE: invention relates to methods for actuation of electrooptical displays. An electrooptical display containing multiple of display pixels and a controlled display controller is actuated, wherein the display controller is connected with the host to provide working instructions to the display controller. The display with a first image is refreshed. The display with a second image following the first image is refreshed. The image data associated with the first image and the second image is processed to identify display pixels with edge artifacts and generate image data associated with the identified pixels. The pixels with edge artifacts associated with the image data are stored in the memory. A waveform is activated to eliminate edge artifacts.

EFFECT: reduced amount of visible artifacts.

8 cl, 10 dwg

Description

The technical field to which the present invention relates

[0001] The present invention relates to methods for driving electro-optical displays. In particular, the present invention relates to excitation methods that are used to reduce edge artifacts of pixels and / or afterimages in electro-optical displays.

Prior art of the present invention

[0002] Electro-optical displays are typically characterized by having back panels provided with a plurality of pixel electrodes, each of which defines one display pixel; moreover, traditionally a single common electrode covering a large number of pixels is provided, and in most cases the display as a whole is provided on the opposite side of the electro-optical medium. The individual pixel electrodes can be driven directly (i.e., a separate conductor can be connected to each pixel electrode), or the pixel electrodes can be driven in a manner similar to the active matrix, as would be familiar to those skilled in the art of back panel technology. Since adjacent pixel electrodes are often at different voltages, they must be separated by finite-width inter-pixel gaps to avoid short circuits between the electrodes. Although at first glance it may seem that the electro-optical medium bridging these gaps should not be switched when the excitation voltage is applied to the pixel electrodes (and indeed, this often happens with some non-bistable electro-optical media, such as liquid crystals, where a black mask is usually provided. to hide these non-switching gaps), in the case of many bistable electro-optical media, such a gap bridging medium is switched due to a phenomenon denoted by the term "spreading".

[0003] Blending refers to a phenomenon where the application of an excitation voltage to a pixel electrode typically changes the optical state of the electro-optical medium over an area larger than the physical dimensions of the pixel electrode. Although excessive blurring should be avoided (for example, in an active high-resolution matrix display, it is undesirable to apply a drive voltage to a single pixel to initiate switching to a region spanning multiple adjacent pixels, as this can reduce the effective resolution of the display), an adjustable amount of blurring is often desirable. Consider, for example, a black and white electro-optical display that displays digits using a standard seven-segment forward excitation array of seven pixel electrodes per digit. When, for example, zero is displayed, six segments turn black. If there is no blur, six inter-pixel gaps will be visible. However, if an adjustable amount of blur is provided, for example, as described in said document 2005/0062714, the inter-pixel gaps will turn black, which makes the discharge more visually appealing. However, blurring can cause a problem called "double vision".

[0004] The bleed area is not uniformly white or black, but is usually a transitional area where, as the blend area is crossed, the color of the medium gradually transitions from white to black through various shades of gray. Accordingly, the "halo" around the edge is usually an area of varying shades of gray, rather than a uniformly gray, but still visible and unwanted area, especially since the human eye is good at distinguishing areas of gray in monochrome images, where each pixel is supposed to be pure black or pure white.

[0005] In some cases, asymmetric bleeding can lead to ghosting at the edges. "Asymmetric spreading" refers to the phenomenon whereby in some electro-optical media (for example, in an electrophoretic medium encapsulated with copper chromite / titanium dioxide, as described in US Pat. No. 7,002,728), the spread is "asymmetric" in the sense that when going from one extreme optical state of the pixel to the other extreme optical state, a stronger spreading is observed than during the transition in the opposite direction; however, in the media described in this patent, the spreading from black to white is usually greater than from white to black.

[0006] Thus, there is a need for driving methods that can reduce the effects of ghosting or blurring.

Brief disclosure of the present invention

[0007] Accordingly, according to one aspect of the present invention, there is provided a method for driving an electro-optical display, which is characterized by the presence of a plurality of display pixels, and which is controlled by a display controller, the display controller being associated with a host providing operating instructions to the display controller, and the proposed method can provide for such stages as: updating the display with the first image; updating the display with a second image following the first image; processing image data associated with the first image and the second image to identify display pixels with edge artifacts and generate image data associated with the identified pixels; storing in memory associated with the image data pixels with edge artifacts; and initiating a waveform to eliminate edge artifacts.

[0008] In another embodiment of the claimed invention, the subject matter presented herein provides a method for driving an electro-optical display with multiple display pixels. This method involves updating the display with the first image; identifying display pixels with edge artifacts after updating the first image; the supply of waveforms designed to eliminate artifacts to the identified pixels; and updating another image on the display. In some embodiments, implementation of the present invention, the proposed method may also include determining the grayscale transition zones in display pixels between the first image and the second image. In some other embodiments of the present invention, the method may include determining display pixels with shades of gray other than at least one of their adjacent primary pixels, and labeling the identified pixels in memory associated with the display controller.

Brief description of the figures

[0009] FIG. 1 is a circuit diagram illustrating an electrophoretic display;

[0010] FIG. 2 shows a circuit model of an electro-optical imaging layer;

[0011] FIG. 3a shows an example of a special waveform in the form of a pair of pulses for erasing the edges of pixels in the transition from white to white;

[0012] FIG. 3b shows an example of a special DC unbalanced pulse for erasing the white edges of pixels when going from white to white;

[0013] FIG. 3c is an example of a specific waveform that initiates a full clear from white to white;

[0014] FIG. 4a shows an example of a specific waveform for erasing pixel edges when going from black to black;

[0015] FIG. 4b is an example of a specific waveform that initiates a full clear from black to black;

[0016] FIG. 5a is a screenshot of a display with a blurring or ghosting effect; and

[0017] FIG. 5b is another screenshot of a display with reduced blurring or ghosting resulting from application of the claimed subject matter described herein; and

[0018] FIG. 6 is an example of a full edge cleaning (GEC) waveform.

Detailed Disclosure of the Present Invention

[0019] The present invention relates to methods for driving electro-optical displays, in particular, bistable electro-optical displays, as well as to a device that is used in the implementation of such methods. In particular, the present invention relates to driving methods that can reduce ghosting and edge effects, as well as reduce flicker of such displays. The present invention is particularly, but not exclusively, intended for use with particle-based electrophoretic displays, in which electrically charged particles of one or more types are present in a liquid medium, moving in a liquid medium under the action of an electric field, changing the display image.

[0020] The term "electro-optical", as applied to a material or display, is used herein in the sense generally accepted in the field of imaging to denote a material that has first and second display states that differ from each other by at least one optical property, and this material transitions from the first display state to the second display state when an electric field is applied to it. While the optical property is usually a color perceptible to the human eye, other optical properties such as optical transmission, reflectance, luminosity or, in the case of machine readable displays, pseudo color in the sense of a change in the reflectance of electromagnetic waves for outside the visible region of the spectrum.

[0021] The term "gray" in the context of this document is used in the sense generally accepted in the field of imaging, to denote a state intermediate between two extreme optical states of a pixel, and does not necessarily imply a black and white transition between these two extreme states. For example, several patents and published applications from E Ink Corporation relate to the electrophoretic displays described below, in which the extreme states are white and dark blue, so that the intermediate "gray state" will actually be a light blue state. In fact, as mentioned above, a change in the optical state may not be associated with a change in color at all. The terms "black" and "white" can be used below to denote the two extreme optical states of the display, and are to be understood as usually including the extreme optical states that are not strictly black and old, but may be, for example, white and dark blue states indicated above. The term "monochrome" can be used below to refer to an excitation circuit that converts pixels only to their extreme optical states, bypassing the gray state.

[0022] Some electro-optical materials are solid in the sense that they have hard outer surfaces, although these materials may (and often are) have an interior filled with liquid or gas. Such displays that use solid electro-optical materials may be referred to herein as "solid-state electro-optical displays" for convenience of description. Thus, the term "solid state electro-optical displays" includes rotating dichromatic displays, electrophoretic encapsulated displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

[0023] The terms "bistable" and "bistable" are used herein in the sense generally accepted in the art to refer to displays containing display elements that are characterized by first and second display states differing from each other by at least one optical property; in this case, after the excitation of any given element with an address pulse of finite duration to give it the first or second display state, it is ensured that after the end of the address pulse, this state is maintained for a certain period of time, which is several times, for example, at least four times the minimum pulse width required to change the state of the display element. US Pat. No. 7,170,670 teaches that some gray scale particle electrophoretic displays exhibit stability not only in extreme black and white states, but also in intermediate gray states, with the same being true for some other electro-optical displays. types. Displays of this type are correctly referred to as "multistable" rather than bistable, although for convenience of description, the term "bistable" may be used herein for both bistable displays and multistable displays.

[0024] The term "pulse" is used herein in its conventional meaning of the integral of voltage over time. However, some bistable electro-optical media function as charge converters, and pulses with an alternative definition, namely, in the value of the current integral over time (equal to the total supplied charge), can be used in such a medium. An appropriate definition of impulse should be used depending on whether the medium acts as a volt-second converter or a charge converter.

[0025] The description below mainly focuses on methods of driving one or more pixels of an electro-optical display by transitioning from an initial gray level to a final gray level (which may or may not be different from the initial gray level). The term "waveform" will be used to refer to the voltage versus time curve used to make the transition from a specified initial gray level to a specified final gray level. Typically, such a waveform contains a plurality of waveform elements; moreover, these elements are characterized by a substantially rectangular shape (i.e., a given element provides for the supply of a constant voltage for a certain period of time); and these elements can be called "pulses" or "excitation pulses". The term "drive circuit" refers to a set of waveforms sufficient to effect all possible transitions between different gray levels in a particular display. The display can use more than one drive circuit; for example, the aforementioned US patent No. 7,012,600 indicates that modification of the drive circuit may be required depending on parameters such as the temperature of the display or the time it is in operation during its life, and therefore the display can be equipped with many different excitation schemes that are used at different temperatures, etc. The set of drive circuits used in this manner may be referred to as a "set of coupled drive circuits." In addition, it is possible, as described in several of the cited MEDEOD applications (methods of driving electro-optical displays), to simultaneously use more than one driving circuit in different parts of the same display; and the set of driving circuits so used may be referred to as a "simultaneous drive set".

[0026] Several types of electro-optical displays are known. One type of electro-optical display is a rotating dichromatic display, as described, for example, in US Pat. 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 dichromatic ball" display, with the term "rotating dichromatic" being preferred as more accurate since some of these patents do not have a spherical shape of the rotating members). Such displays use a large number of small-sized bodies (usually spherical or cylindrical) with two or more segments with different optical characteristics and an internal dipole. These bodies are suspended in liquid-filled bubbles of the matrix, and these bubbles are filled with liquid so that these bodies can rotate freely. The appearance of the image on the display changes when an electric field is applied to it, as a result of which the bodies rotate with their transition to different positions, and through the working surface of the display you can see the change of body segments. An electro-optical medium of this type is usually bistable.

[0027] Other types of electro-optical displays use electrochromic media, for example, an electrochromic medium in the form of a nanochromic film containing an electrode made - at least in part - of a semiconducting metal oxide and a plurality of reversibly colored colored molecules attached to the electrode; see, for example, O'Regan, B. et al., Nature, 1991, 353 , 737; and by an author named Wood, D., Information Display, 18 (3) , 24 (March 2002). See also Bach, U. et al., Adv. Mater., 2002, 14 (11) , 845. Nanochromic films of this type are also described, for example, in US Patent Nos. 6,301,038; 6,870,657; and 6,950,220. This type of environment is usually also bistable.

[0028] Another type of electro-optical display is an electrowetting display, which was developed by Philips and described in "Electrowetting Video Speed Electronic Paper" by Hayes, RA et al. Nature, 425 , 383-385 (2003) ... US Pat. No. 7,420,549 teaches that such electrowetting displays can be bistable.

[0029] One electro-optical display that has been the subject of serious research and development for many years is a particle-based electrophoretic display in which a plurality of charged particles move through a fluid under the action of an electric field. Electrophoretic displays can be characterized by such features as high brightness and contrast, wide viewing angles, bistability of states and low power consumption, unlike liquid crystal displays. However, widespread use of these displays has been hampered by problems with maintaining adequate image quality on these displays for extended periods of time. For example, the particles that make up electrophoretic displays tend to settle, which leads to a decrease in the life of these displays.

[0030] As noted above, electrophoretic media require a fluid. In most prior art electrophoretic fluids, this fluid is a liquid, but the electrophoretic fluid can also be generated using gaseous fluids; see, for example, Movement of Electric Toner in an Electronic Paper-Like Display by Kitamura, T. et al, IDW, Japan, 2001, document HCS1-1; and "Toner Display Using Triboelectrically Charged Insulating Particles" by Yamaguchi, Y. et al, IDW, Japan, 2001, document AMD4-4). See also U.S. Patent Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic fluids appear to be susceptible to the same settling problems as liquid electrophoretic fluids when these fluids are used in an orientation that allows for such deposition as may be observed, for example, in a labeling with the position of the medium. in the vertical plane. In fact, particle deposition appears to be a more serious problem in gas-based electrophoretic fluids than in similar liquid-based fluids, since the lower viscosity of gaseous suspended fluids compared to liquid fluids results in faster deposition of electrophoretic particles.

[0031] Numerous patents and applications assigned to, or in their name, and filed on behalf of the Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various technologies used in encapsulated electrophoretic and other electro-optical media. Such encapsulated media include a plurality of small capsules, each of which itself includes an internal phase containing electrophoretically mobile particles in a fluid, this internal phase being enclosed by the capsule walls. The capsules themselves are usually held in a polymeric binder to form a cohesive layer that is sandwiched between the two electrodes. The technologies described in these patents and applications include:

[0032] (a) Electrophoretic particles, fluids and fluid additives; see, for example, US Pat. Nos. 7,002,728 and 7,679,814;

[0033] (b) Capsules, binders and encapsulation processes; see, for example, US Pat. Nos. 6,922,276 and 7,411,719;

[0034] (c) Microcellular structures, wall materials and methods for forming microcells; see, for example, US Pat. Nos. 7,072,095 and 9,279,906;

[0035] (d) Methods for filling and sealing microcells; see, for example, US Patent Nos. 7,144,942 and 7,715,088;

[0036] (e) Films and subunits containing electro-optical materials; see, for example, US Pat. Nos. 6,982,178 and 7,839,564;

[0037] (f) Back panels, adhesives and other auxiliary layers and methods used in displays; see, for example, US Pat. Nos. 7,116,318 and 7,535,624;

[0038] (g) Color change and color correction; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564.

[0039] h) Applications of displays; see, for example, US Patent Nos. 7,312,784; 8,009,348;

[0040] (i) Non-electrophoretic displays described in US Pat. No. 6,241,921 and US Patent Application Publication No. 2015/0277160; and non-display encapsulation and microcell technology applications; see, for example, US Patent Application Publication Nos. 2015/0005720 and 2016/0012710; and

[0041] (j) Methods for driving displays can be found, for example, in US Pat. 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 in US Patent Application Publication Nos. 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; 2008/0291129; 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; 2011/0221740; 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.

[0042] Many of these patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, resulting in a so-called polymer dispersed electrophoretic display, in which the electrophoretic medium contains a plurality of discrete electrophoretic fluid droplets and a continuous phase of polymeric material, and that discrete electrophoretic fluid droplets in such a dispersed polymer electrophoretic display can be considered capsules or microcapsules even if no discrete capsule membrane is associated with each individual droplet; see, for example, U.S. publication No. 2002/0131147. Accordingly, for the purposes of the present invention, such polymer dispersed electrophoretic media are considered to be a subset of encapsulated electrophoretic media.

[0043] A related type of electrophoretic display is the so-called "microcell electrophoretic display". In a microcellular electrophoretic display, charged particles and suspended fluid are not encapsulated in microcapsules, but are instead held in a plurality of cavities formed in a carrier medium, which is, for example, a polymer film. See, for example, International Publication No. WO 02/01281 and US Published Patent Application No. 2002/0075556, both of which are owned by Sipix Imaging, Inc.

[0044] Many of these patents and applications from E Ink and the MIT Institute also contemplate microcellular electrophoretic displays and polymer dispersed electrophoretic displays. The term "encapsulated electrophoretic displays" can refer to all such types of displays, which may also be referred to collectively as "microvoid electrophoretic displays" to summarize wall morphology.

[0045] Another type of electro-optical display is an electrowetting display, which was developed by Philips and described in "Electrowetting Video Speed Electronic Paper" by Hayes, RA et al. Nature 425 , 383-385 (2003) ... In co-pending application No. 10 / 711,802, filed October 6, 2004, it is shown that such electrowetting displays can be bistable.

[0046] Other types of electro-optical materials can also be used. Of particular interest are bistable ferroelectric liquid crystal displays (FLCs) known in the art and having pronounced residual voltage properties.

[0047] Although electrophoretic media can be opaque (because, for example, in many electrophoretic media, particles substantially block the transmission of visible light through the display) and operate in reflection, some electrophoretic displays can be configured to operate in a so-called "shutter mode" which provides for two display states, in one of which it is opaque, and in the other, it can transmit light. See, for example, US Pat. Nos. 5, 6,130,774 and 6,172,798, and US Pat. Nos. 5,872,552; 6,144,361; 6,271,823; 6,225,971; and 6,184,856. In a similar mode, dielectrophoretic displays can function, which are similar to electrophoretic displays, but the principle of operation of which is based on a change in the strength of the electric field; see US patent No. 4,418,346. Other types of electro-optical displays can also operate in shutter mode.

[0048] To obtain a high-resolution display, the addressing of individual display pixels should not be interfered with by neighboring pixels. One way to achieve this goal is to provide an array of non-linear elements such as transistors or diodes; moreover, to obtain a display with an "active matrix", at least one non-linear element must be associated with each pixel. Through a corresponding nonlinear element, an address or pixel electrode, which refers to one pixel, is connected to a corresponding voltage source. When a transistor is used as a non-linear element, the pixel electrode can be connected to the drain of the transistor, and this circuit will be adopted in the following description, although such a choice is essentially arbitrary and the pixel electrode can be connected to the source of the transistor. In high-resolution arrays, pixels can be arranged in a two-dimensional array of rows and columns so that each individual pixel is uniquely identified at the intersection of one particular row and one 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 horizontal electrode. We repeat once again that the scheme with the binding of sources to rows, and gates to columns, if necessary, can be reversed.

[0049] The display can be filled line by line. The line electrodes are connected to a line driver that can supply voltage to the selected line electrode, ensuring that all transistors in the selected row are conductive, while applying voltage to all other rows ensures that all transistors in those unselected rows remain non-conductive. The columnar electrodes are connected to columnar drivers, which apply to the various columnar electrodes the voltages selected to drive the pixels in the selected row until the desired optical state is obtained (these voltages are related to a common front electrode that may be provided on the opposite side of the electro-optical medium relative to the nonlinear array and runs across the entire display). As is known in the art, voltage is a relative value and serves as a measure of the difference in charge between two points. One voltage value is relative to another voltage value. For example, zero voltage ("0V") means no voltage difference. After a predetermined time, known as "row addressing time," the selection of the selected row is deselected, the next row is selected, and the voltages on the column drivers change, causing the display to display the next row.

[0050] However, during operation, some waveforms can create residual voltage on the pixels of the electro-optical display, and as described above, this residual voltage generates unnecessary optical effects and is therefore generally undesirable.

[0051] In the context of this document, the term "shift" of the optical state in relation to an address pulse denotes a situation in which the first supply of a specific address pulse to an electro-optical display leads to the first optical state (for example, the first gray level), and the subsequent supply of the same address pulse to the electro-optical display results in a second optical state (eg, a second gray level). Shifts in the optical state can be generated by residual voltages, since the voltage applied to the pixel of the electro-optical display during the application of the address pulse is the sum of the residual voltage and the voltage of the address pulse.

[0052] The term "displacement" of the optical state of a display over time denotes a situation in which the optical state of an electro-optical display changes when that display is at rest (eg, during a period when no address pulse is applied to the display). Displacements of the optical state can be generated by residual stresses, since the optical state of a pixel can depend on the residual voltage on the pixel, and this residual voltage can decrease over time.

[0053] As stated above, "ghosting" refers to a situation in which, after refilling the electro-optical display, traces of the previous image (s) are still visible. Residual stresses can give rise to "ghosting", which is a type of ghosting that leaves the outline (s) of a portion of the previous image visible.

[0054] An exemplary embodiment of an electrophoretic display (EPD)

[0055] FIG. 1 schematically illustrates an electro-optical display pixel 100 in accordance with the claimed subject matter presented herein. Pixel 100 may include film 110 for imaging. In some embodiments, the imaging film 110 may be bistable. In some embodiments, the imaging film 110 may be, but is not limited to, an encapsulated electrophoretic imaging film, which may include, for example, charged pigment dye particles.

[0056] The image forming film 110 may be disposed between the front electrode 102 and the back electrode 104. The front electrode 102 may be formed between the image forming film and the display face. In some embodiments, implementation of the present invention, the front electrode 102 may be transparent. In some embodiments, implementation of the present invention, the front electrode 102 can be made of any suitable transparent material, including but not limited to indium tin oxide (ITO). The back electrode 105 may be formed opposite the front electrode 102. In some embodiments of the present invention, a stray capacitance (not shown) may be formed between the front electrode 102 and the back electrode 104.

[0057] Pixel 100 can be any of a variety of pixels. The plurality of pixels can be arranged in a two-dimensional array of matrixed rows and columns such that each individual pixel is uniquely identified at the intersection of one particular row and one particular column. In some embodiments, implementation of the present invention, the pixel array may be an "active matrix" in which each pixel is associated with at least one non-linear element 120. The non-linear element 120 of the circuit can be included between the back electrode 104 and the address electrode 108. In some embodiments of the present invention, the non-linear element 120 may be a diode and / or a transistor, including but not limited to a MOSFET (metal oxide semiconductor field effect transistor). The drain (or source) of the MOS transistor may be connected to the back electrode 104; the source (or drain) of the MOS transistor can be connected to the address electrode 108; and the gate of the MOS transistor may be connected to a driver electrode 106 configured to control activation and deactivation of the MOS transistor (for simplicity, the terminal of the MOS transistor connected to the rear electrode 104 will be referred to as the drain of the MOS transistor; and the terminal of the MOS transistor, connected to the address electrode 108 will be referred to as the source of the MOS transistor, however, it will be apparent to one skilled in the art that in some embodiments of the present invention the terms drain and source of a MOS transistor may be used interchangeably).

[0058] In some active matrix embodiments, address electrodes 108 of all pixels in each column may be connected to one common electrode, and driver electrodes 106 of all pixels in each row may be connected to the same horizontal electrode. The line electrodes can be connected to a line driver that can select one or more lines by supplying the selected line electrodes with a voltage sufficient to activate the nonlinear elements 120 of all pixels 100 in the selected line / lines. The columnar electrodes can be connected to columnar drivers that can supply the target electrode 106 of the selected (activated) pixel with a voltage calculated to bring the pixel to the desired optical state. The voltage applied to the address electrode 108 may be a voltage relative to the voltage applied to the front pixel electrode 102 (eg, about zero volts). In some embodiments, implementation of the present invention, the front electrodes 102 of all pixels in the active matrix may be connected to a common electrode.

[0059] In some embodiments, implementation of the present invention, pixels 100 of the active matrix may be filled line by line. For example, a row of pixels is selected by a line driver, and voltages corresponding to the required optical states for a row of pixels are supplied to the pixels by the column drivers. After a predetermined time, known as "row addressing time," the selected row can be deselected, the next row can be selected, and the voltages on the column drivers can be changed, causing the display to display the next row.

[0060] FIG. 2 shows a circuit model of an electro-optical imaging layer 110 disposed between a front electrode 102 and a back electrode 104, in accordance with the subject matter described herein. Resistor 202 and capacitor 204 can represent the resistance and capacitance of the electro-optical imaging layer 110, the front electrode 102 and the back electrode 104, including any adhesive layers. Resistor 212 and capacitor 214 can represent the resistance and capacitance of the multi-layer adhesive. Capacitor 216 may represent electrical capacitance that may be formed between the front electrode 102 and the back electrode 104, for example, in interface contact areas between layers such as the interface between the imaging layer and the multi-layer adhesive and / or between the multi-layer adhesive and the back electrode. The voltage Vi on the imaging film 110 may include residual voltage across the pixels.

[0061] Detecting and reducing or removing edge artifacts and ghosting in the electro-optical display described above may require additional processing of the image data; however, some of the image data processing techniques that can be used are artifact detection and removal techniques described in US Patent Publication No. 2013/0194250 A1 to Amundson et al. ("Amundson") and US Patent Publication No. 2016/0225322 A1 issued to the author named Sim et al ("Sim"), and the contents of which are incorporated herein in their entirety. However, such methods of processing image data and removing edge artifacts and ghosting of pixels may require additional time on their own processing, which is not always available. Thus, in a high-speed refresh waveform mode such as the "forward refresh" waveform mode described below, it may be appropriate to perform image data processing at the same time as the image data refresh process. In addition, edge artifacts and ghosting can be initiated and performed only when needed.

[0062] Direct Update or DUDS Mode

[0063] In some applications, the display may use a high speed update waveform mode, such as a "direct update" signal (DUDS) mode. DUDS mode can provide two or more two gray levels, but is usually less than a grayscale drive circuit (GSDS) that can provide transitions between all possible gray levels, but the most important characteristic of DUDS mode is that the control of transitions from the original level gray level to the final gray level is carried out by the method of simple unidirectional excitation, as opposed to the "indirect" transitions often used in the GSDS scheme, in which, at least in some transitions, the pixel is transferred from the original gray level to one of the extreme optical states, and then to back to the final gray level; and in some cases, the transition can be carried out by exciting the pixel with its transfer to one of the extreme optical states from the initial gray level, then to the opposite extreme optical state, and only then to the final extreme optical state; see, for example, the driving circuit illustrated in FIG. 11A and 11B of said US Pat. No. 7,012,600. Thus, the presented electrophoretic displays can have a refresh time in grayscale mode, approximately two to three times longer than the saturation pulse duration (where the phrase "saturation pulse duration" is defined as a period of time at a given voltage sufficient to excite a display pixel with its transfer from one extreme optical state to another), or about 700-900 milliseconds; while DUDS mode has a maximum refresh time of saturation pulse width, or approximately 200-300 milliseconds.

[0064] It should be noted that the waveform mode or "Direct Update" (DU) drive circuit described above is used herein to explain the general operating principles of the subject matter disclosed herein. This does not mean that they in any way limit the current subject matter of the invention, as these operating principles can be effectively applied to other drive waveforms or drive circuits.

[0065] The DU mode is a driving scheme that typically treats white and black updates as empty self-transition updates. DU mode is characterized by short refresh times for fast black or white display with minimal flash transition times where the display flickers, which may be visually unattractive to some users. DU mode can sometimes be used to display menus, status indicators, keyboards, and more on the display screen. Since both white-to-black and black-to-white transitions are zero (ie, unexcited) in DU mode, edge artifacts can occur on a black or white background.

[0066] As mentioned above, when a non-excited pixel is adjacent to a pixel that is being updated, a phenomenon known as "blurring" occurs, in which the excitation of the excited pixels causes a change in the optical state in a region whose area is slightly larger than the area of the excited pixel. and this area partially overlaps the area of neighboring pixels. This blurring appears as edge effects along the boundaries of the abutment of unexcited pixels to excited pixels. Similar edge effects occur when using local updates (where only a specific area of the display is updated, for example, to display an image), and in addition to occurring with local updates, edge effects also occur at the border of the updated area. Over time, these edge effects become distracting and should be addressed. Until now, such edge effects (and color shifting effects in unexcited white pixels) have usually been removed with only Full Clear or GC updates at regular intervals. Unfortunately, using such irregular updates using the GC method can revive the update problem as a brief glimpse; and, of course, the flashy nature of the update can be compounded by the fact that flash updates are performed at long intervals.

Refreshing the image while processing edge artifact data

[0067] By comparison, some techniques for reducing edge artifacts in display pixels can introduce additional time lag due to the image processing required to detect and eliminate edge artifacts after each image refresh. In addition, the use of dc unbalanced waveforms in these edge artifact mitigation techniques will be nearly impossible, since the short delay between updates (eg, in the DU mode presented above) does not allow enough time to discharge after excitation. And without discharge after excitation, there is a potential hazard to the overall optical performance and reliability of the modules.

[0068] Alternatively, in some embodiments of the present invention, image data processing such as described by authors such as Amundson and Sim may be performed concurrently with the image refresh process. For example, as the display 100 updates the first image, the data of the first and subsequent second images may be processed to identify pixels in which edge artifacts or other unwanted optical defects may occur. This data can then be stored in a buffer memory so that the edge artifact removal process can be performed later. In some embodiments of the present invention, such image data processing may be performed when subsequent images are transmitted to the EPDC (Electrophoretic Display Controller) controller. In some other embodiments of the present invention, when the images to be updated are known, such processing of the image data may be performed before updating subsequent images.

[0069] One way to track or generate and store this edge artifact information as the optical states of an electro-optical display change is to generate an appropriate map, which map may contain information such as which pixels on the display will have a large share. the likelihood of contributing to the development of edge artifacts. One such method is described in US patent application No. 2016 / 128,996, filed by Sim et al., The entire contents of which are incorporated herein.

[0070] For example, in some embodiments of the present invention, pixel edge artifacts generated using the drive circuit or drive waveform modes may be stored in memory (eg, as binary maps); for example, each pixel of the display may be represented by a MAP pointer (i, j), and pixels that may contribute to the development of edge artifacts may be labeled and information about them (i.e., the MAP pointer (i. j)) may be saved in a binary card. Illustrated below is one approach that can be used to track the generated edge artifacts on the map and mark such pixels.

MAP (i, j) = 0 for all i, j;

For all DU updates in sequential order

For all pixels (i, j) in any order:

If the color transition of the pixel is carried out in the direction White → White; And all four cardinal neighboring pixels are characterized by the following shade of white; And in the presence of at least one cardinal neighboring pixel, characterized by a current hue other than white; And the MAP pointer (i, j) of all neighboring pixels is zero; then MAP (i, j) = 1.

Otherwise, if the color transition of the pixel is carried out in the direction Black → Black; And, at least one cardinal adjacent pixel has a current hue other than black; And the next shade is black; And the pointer MAP (i, j) of all neighboring pixels is zero, then MAP (i, j) = 2.

End

End

End

[0071] This approach provides that if certain conditions are met, a display pixel designated as MAP (i, j) may be labeled with a numeric value of 1, indicating that dark edge artifacts are generated at that pixel. Some of the required conditions may include: (1) a given display pixel is in a white-to-white transition state; (2) all four cardinal neighboring pixels (ie, the four nearest neighboring pixels) have the following shade of white; And (3) at least one cardinal neighboring pixel has a current hue other than white; and (4) none of the neighboring pixels (i.e., the four cardinal adjacent pixels and diagonal pixels) is marked at this point in time as having edge artifacts.

[0072] Likewise, if certain conditions are met, the MAP pixel (i, j) may be labeled with a numeric value of 2, indicating the formation of white edges on this pixel. Some of the required conditions may include: (1) a given display pixel is in a black-to-black transition state; (2) at least one cardinal neighboring pixel has a current hue other than black, but the next hue is black; and (3) none of the neighboring pixels (ie, the four cardinal neighboring pixels and diagonal pixels) is marked at this point in time as having edge artifacts.

[0073] One of the advantages of this approach is that, in operation, the above image processing (ie, map generation and pixel labeling) can be performed concurrently with the display refresh cycles, thus avoiding an excessive increase in refresh cycle latency. due to - at least in part - that only the generated map is required to complete the update cycle.

[0074] Upon completion of the refresh mode (eg, the display stops using a particular refresh mode), the pixel information collected in the generated map can subsequently be used to remove edge artifacts (eg, using the DU_OUT mode). For example, pixels labeled as having edge artifacts can be cleaned up with waveforms that give a faint glimpse.

[0075] In some embodiments of the present invention, waveforms can be used to eliminate edge artifacts to initiate full cleanup on the transition from white to white and from black to black, in combination with specific waveforms to erase the edges during the transition from white to white, and from black to black. For example, balanced pulse pairs disclosed in U.S. Patent Application Publication No. 2013/0194250, the contents of which are incorporated herein in its entirety, specify the following:

For all pixels (i, j) in any order

If the color transition of the pixel is in the direction White → White, and not Black → Black, then the normal transition DU_OUT is initiated.

Otherwise, if MAP (i, j) = 1, and the color transition of the pixel is carried out in the White → White direction, then a special oscillatory signal is generated, initiating a complete cleaning when changing from white to white.

Otherwise, if the color transition of a pixel is in the White → White direction, AND the MAP (i, j) pointer of at least one cardinal neighboring pixel is 1, then a special waveform is generated to initiate edge erasure when transitioning from white to white.

Otherwise, if MAP (i, j) = 2, and the color transition of the pixel is carried out in the direction Black → Black, then a special waveform is generated that initiates a complete cleaning when changing from black to black.

Otherwise, if the color transition of a pixel is in the direction Black → Black, AND the MAP (i, j) pointer of at least one cardinal neighboring pixel is 2, then a special waveform is generated to initiate edge erasure when transitioning from black to black.

Otherwise, the transition Black → Black / White → White is initiated according to the DU_OUT waveform table.

End

End

[0076] With this approach, a DU_OUT transition circuit (eg, a modified DU circuit with an edge artifact reduction algorithm enabled) can be applied to pixels that do not transition from white to white or black to black; for example, these pixels can perceive normal transient updates as if they were being driven by a conventional DU circuit. In other cases, a special waveform can be applied to a pixel that has dark edge artifacts (i.e., MAP (i, j) = 1) and transitions from white to white state, initiating a complete cleanup when transitioning from white to white. In some embodiments of the present invention, this white-to-white waveform may be a waveform similar to that illustrated in FIG. 3c, and which can be substantially DC balanced, which means that the sum of the applied bias voltages as a function of magnitude and time is generally substantially zero; otherwise, if a pixel goes from white to white, and at least one cardinal neighboring pixel is characterized by the presence of a dark edge artifact (i.e. MAP (i, j) = 1), then a special waveform is generated that initiates erasing the edges in the transition from white to white (see Fig. 3a); otherwise, if a pixel has a white edge artifact (i.e., MAP (i, j) = 2) and goes from black to black, then a special waveform can be generated, initiating a complete clear in the transition from black to black, which is shown in FIG. 4b; otherwise, if a pixel goes from black to black, AND at least one cardinal adjacent pixel is marked as having a white edge artifact (i.e., MAP (i, j) = 2), then a special waveform is generated to initiate erasure edges in the black-to-black transition, which is shown in FIG. 4a; otherwise, all other pixels are supplied with black-to-black or white-to-white waveforms using waveforms from the waveform table DU-OUT.

[0077] When using this method to eliminate edge artifacts, waveforms that initiate a complete cleanup on the transition from white to white and from black to black are used in parallel with special waveforms that initiate the erasure of the edges during the transition from white to white and from black to black. ... In some embodiments, implementation of the present invention, specific waveforms that initiate erasing of edges in the transition from white to white, can take the form of a pair of pulses, as described in US patent publication No. 2013/0194250 issued to the author under the name Amundson et al. included herein, or a DC unbalanced drive pulse initiating a transition to white, which is illustrated in FIG. 3b; and in this case, the discharge after excitation described above can be used to discharge residual voltages and reduce the loads on the device. Likewise, the DC unbalanced pulse shown in FIG. 4a can be used to blacken a pixel; and in this case, as in the previous, discharge after excitation can be performed. As shown in FIG. 4, such a DC unbalanced pulse only needs to drive a positive voltage of 15 volts over a period of time. In this configuration, excellent edge cleaning performance can be obtained by small size externally noticeable transition deviations (eg, flashes) by using a special waveform to initiate full cleaning.

[0078] In yet another embodiment of the present invention, visually perceptible transition deviations (eg, gleams) can be reduced using an alternative implementation described below.

For all pixels (i, j) in any order

If the color transition of the pixel is in the direction White → White, and not Black → Black, then the normal transition DU_OUT is initiated.

Otherwise, if MAP (i, j) = 1, and the color transition of the pixel is in the White → White direction, then an unbalanced DC drive pulse is supplied to transition to the white state.

Otherwise, if MAP (i, j) = 2, and the color transition of the pixel is in the direction Black → Black, then an unbalanced DC drive pulse is applied to go to the black state.

Otherwise, the transition Black → Black / White → White is initiated according to the DU_OUT waveform table.

End

End

[0079] This approach provides that instead of using the specific edge erasure waveforms described above in relation to the first method, DC unbalanced waveforms can be used to eliminate edge artifacts. In some cases, a post-excitation vacuum may be performed to reduce the hardware load caused by unbalanced waveforms. In operation, when the display pixel does not transition from white to white, as well as from black to black, a normal DU-OUT transition is initiated with respect to this pixel. Otherwise, if a display pixel is identified as having dark edge artifacts (i.e., MAP (i, j) = 1), and it goes from white to white, then an unbalanced DC drive pulse ( for example, a pulse similar to that shown in Fig. 3b); otherwise, if a display pixel is identified as having white edge artifacts (i.e., MAP (i, j) = 2) and it goes from black to black, then a DC unbalanced drive pulse ( for example, a pulse similar to that shown in Fig. 4a); otherwise, black-to-black or white-to-white transitions of the display pixels are initiated using the waveforms contained in the waveform table DU-OUT.

[0080] In yet another embodiment of the present invention, instead of storing edge artifact information in dedicated memory, it may be transferred to an image buffer associated with an electrophoretic display controller (EPDC) (eg, using a next image buffer associated with the controller).

For all DU updates in sequential order

For all pixels (i, j) in any order:

If the color transition of the pixel is carried out in the direction White → White; And all four cardinal neighboring pixels are characterized by the following shade of white; And there is at least one cardinal adjacent pixel having a current tone other than white; then the next shade is set as transitioning from a special white state to white.

Otherwise, if the color transition of the pixel is carried out in the direction Black → Black; And, at least one cardinal adjacent pixel has a current hue other than black; And the next shade is black; then the next shade is set to transition from a special black state to black.

End

End

End

[0081] This approach provides that if a pixel transitions from white to white, and all four adjacent cardinal pixels are characterized by the next shade of white, and the current shade of at least one cardinal neighboring pixel is different from white, then the next shade of the pixel set to transition from a special white state to white in the next image buffer; otherwise, if the color transition of a pixel is in the direction from black to black, and at least one cardinal neighboring pixel has a current hue other than black, and the next hue is black, then the next pixel hue is set as transition from a special black state to black in the next image buffer. During operation during the refresh cycle, the image transitions from the special white state to white and from the special black state to black can be the same as the transitions from the white state to the white state and from the black to black state, as for the transition with the application of waveforms and for image processing. For a waveform transition, this means:

• Special white state → White state transition (ie from white state to white state) is equivalent to White state → White state transition (ie from white state to white state) according to the waveform lookup table.

• the transition Special white state → Any gray state (ie from white state to any gray state) is equivalent to the transition White state → Any gray state (ie from white state to any gray state) according to the waveform look-up table, etc. ...

• The Special Black State → Black State (ie, from black to black state) transition is equivalent to the Black State → Black State transition (ie, from black to black state) according to the waveform look-up table.

• the transition Special black state → Any gray state (ie from black state to any gray state) is equivalent to the transition Black state → Any gray state (ie from black state to any gray state) according to the waveform look-up table, etc. ...

During the OUT mode, for the transition from the special white state to white, it is provided to receive an unbalanced DC-to-white pulse (for example, one of the variants of such a pulse is shown in Fig.3b), and to transition from the special black to black state, an unbalanced by direct current of the pulse of transition to the black state (for example, one of the variants of such a pulse is shown in Fig. 4a). The data processing using the imaging algorithm happens in the background during the DU mode update, which means that the DU update time can be used for image processing.

[0082] FIG. 5a and 5b show displays, for one of which edge artifact reduction was performed, and for the other, edge artifact reduction was not performed. In practice, where edge artifact reduction is not performed, white edges on a black background are clearly visible, as shown in FIG. 5a. Conversely, in FIG. 5b shows that the white edges are erased using one of the proposed methods presented in this document.

[0083] In some embodiments of the present invention, pixels with edge artifacts, or pixels that can potentially contribute to the development of edge artifacts, can be marked as described above and stored in a memory other than the buffer memory used to update images, for example, in memory, separate from the buffer memory used to update the image. However, in some cases it may be advisable to reduce the amount of memory used. Thus, in some embodiments of the present invention, the memory used to update the images (eg, the buffer memory to update the image) may also be used to store summary information about edge artifacts. For example, when the optical state of an electro-optical display changes (eg, during image refresh), instead of generating a map with all pixels, it is possible to map individual pixels to an indicator configured to determine if a particular pixel has edge artifacts. This indicator can be used to determine if a particular pixel is marked as having edge artifacts. As the display undergoes more and more image updates (e.g., more and more changes in optical state), presumably more pixels can be labeled as having edge artifacts (e.g., an edge artifact indicator associated with these pixels is signaled or turned on) ). Later, these pixels, marked as having edge artifacts, can collectively be cleared or reset using a reset waveform.

[0084] Elimination of edge artifacts

[0085] The processed edge artifact data can be used at any convenient time to eliminate edge artifacts. The erasing or cleaning process can be activated or initiated by various conditions.

[0086] In some embodiments, a clear request may be initiated by a host (eg, a processor) like another request sent by a host to a controller, and such a request may be sent concurrently with other image update requests. For example, after an interactive dialog where the DUDS waveform mode was used to update the display to remove accumulated edge artifacts generated by using the DUDS mode, the host may request the EPDC to set a specific time frame to remove edge artifacts.

[0087] In some other embodiments, implementation of the present invention, the cleaning process can be initiated when it is convenient for the display. For example, when the EPDC goes idle for a specified time, it may decide to initiate a cleanup process to remove edge artifacts using the collected edge artifact data.

[0088] In yet another embodiment of the present invention, this processed image data, which includes pixel identification with edge artifacts, may be used by a drive circuit or refresh waveform mode using waveforms to eliminate edge artifacts. For example, in pen input where the DUDS waveform mode is used to provide high performance, a subsequent waveform mode used for smoothing may include waveforms to eliminate edge artifacts, and this subsequent waveform mode may use processed image data with edge information. artifacts to eliminate them.

[0089] In some embodiments, the Full Edge Erase (GEC) waveform mode may be used to eliminate edge artifacts. FIG. 6 illustrates a simple GEC waveform, the waveform including flat top pulses configured to drive a pixel transition to an optical edge state. This waveform can be six frames long or 66 microseconds long at 25 degrees Celsius. The GEC mode can have a shorter duration compared to the waveform mode with integrated edge cleaning phases. Thus, the GEC mode can be easily adapted to edge cleaning in combination with the various drive waveforms currently used without introducing excessive time delays. For example, when the GEC mode is used in conjunction with the DUDS waveform mode described above, since the GEC mode is triggered for a short period of time, post-GEC discharge may be performed after excitation before updating the subsequent display. In some embodiments, implementation of the present invention, the EPDC controller can sort and select the waveform to use depending on the amount of edge artifacts present. For example, if the amount of edge artifacts exceeds a certain threshold, the EPDC can select the full clear waveform (mode) to clear the entire display.

[0090] In another embodiment of the present invention, the EPDC may activate a clear waveform if there are too many pixels with edge artifacts. For example, an EPDC may provide an algorithm configured to track the total number of pixels with edge artifacts and compare it to the total number of pixels on the display. The result of such a comparison can be stored in the buffer memory as a percentile value. This stored value can be periodically compared to a predetermined threshold, and if the stored value exceeds the threshold, the EPDC can decide to activate the full clear waveform mode, in which the full clear waveform can reset every pixel on the display to its original state ( for example, trigger the transition of each pixel to an extreme gray or color state).

[0091] It will be apparent to those skilled in the art that numerous changes and modifications can be made to the specific embodiments of the present invention described above without departing from the scope of the claimed invention. Accordingly, the foregoing description in its entirety is to be construed as illustrative and not restrictive.

Claims (15)

1. A method of driving an electro-optical display characterized by the presence of a plurality of display pixels and controlled by a display controller, the display controller being associated with a host for providing operating instructions to the display controller, the method comprising: updating the display with the first image; updating the display with a second image following the first image; updating the display with a third image following the second image; processing image data associated with the first image and the second image while simultaneously updating the third image to identify display pixels with edge artifacts and generate image data associated with the identified pixels; storing in memory the image data associated with the identified pixels; selecting a waveform depending on the generated image data, and activation of the waveform to eliminate edge artifacts in response to a request initiated by the host. 2. The method of claim 1, wherein generating image data associated with the identified pixels comprises marking the identified pixels with an indicator. 3. The method of claim 2, wherein the step of identifying display pixels with edge artifacts comprises determining display pixels whose hues differ from at least one of their adjacent cardinal pixels. 4. The method of claim 2, wherein the step of identifying edge artifact display pixels comprises marking the identified pixels in a buffer memory associated with the display controller. 5. The method of claim 1, wherein the step of activating the waveform set comprises receiving a clear command from a host. 6. The method of claim 1, wherein the step of activating the waveform set comprises activating the cleaning waveform by the display controller after a pause in operation for a predetermined amount of time. 7. The method of claim 1, wherein the step of activating the waveform set comprises applying a waveform mode that uses waveforms to eliminate edge artifacts. 8. The method of claim 1, wherein the step of activating the waveform set comprises supplying a DC unbalanced waveform.

Images