KR102435841B1 - Electro-optical displays and their driving methods - Google Patents

Abstract

Various methods are described for driving electro-optic displays to reduce visible artifacts. Such methods include driving an electro-optical display having a plurality of display pixels and controlled by a display controller, the display controller associated with a host for providing operational instructions to the display controller, the method comprising: updating the first image, updating the display with a second image subsequent to the first image, processing the image data associated with the first image and the second image to identify display pixels having edge artifacts and the identified pixels generating image data associated with , storing image data associated with pixels having edge artifacts in a memory location, and initiating a waveform to clear the edge artifacts.

Description

Electro-optical displays and their driving methods

The present invention relates to methods for driving electro-optic displays. More particularly, the present invention relates to driving methods for reducing pixel edge artifacts and/or image persistence in electro-optic displays.

Electro-optical displays typically have a backplane provided with a plurality of pixel electrodes, each of the plurality of pixel electrodes defining one pixel of the display; Conventionally, a single common electrode extends over a number of pixels, and usually the entire display is provided on opposite sides of the electro-optic medium. The individual pixel electrodes may be driven directly (ie, a separate conductor may be provided for each pixel electrode) or the pixel electrodes may be driven in an active matrix manner familiar to those skilled in backplane art. Because adjacent pixel electrodes will often be at different voltages, they must be separated by inter-pixel gaps of finite width to avoid electrical shorts between the electrodes. At first glance it seems that the electro-optic medium overlying these gaps will not switch when driving voltages are applied to the pixel electrodes (and, in fact, it is a liquid crystal, where a black mask is usually provided to hide the non-switching gaps) Although it may appear to be common with some non-bistable electro-optic media, such as those that Switching due to phenomena.

Blooming refers to the tendency of application of a driving voltage to a pixel electrode to cause a change in the optical state of the electro-optic medium over an area larger than the physical size of the pixel electrode. Excessive blooming should be avoided (e.g., in high resolution active matrix displays, it is undesirable to apply a drive voltage to a single pixel to cause switching over an area covering several adjacent pixels, which reduces the effective resolution of the display. ), a controlled amount of blooming is often useful. For example, consider a black-on-white electro-optic display that displays numbers using a conventional 7-segment array of 7 directly driven pixel electrodes for each digit. For example, when 0 is displayed, 6 segments will turn black. Without blooming, the 6 inter-pixel gaps would be visible. However, by providing a controlled amount of blooming, for example, as described in supra-2005/0062714, inter-pixel gaps can turn black, resulting in a more visually pleasing digit. However, blooming can cause problems, meaning "edge ghosting".

The region of blooming is not a uniform white or black, but is typically a transition region where the color of the medium transitions from white through various shades of gray to black as it moves across the region of blooming. Thus, an edge ghost will typically be a region of various shades of gray rather than a uniform region of gray, but the human eye is particularly good at identifying regions of gray in monochrome images where each pixel is assumed to be pure black or pure white. Because it can be detected, it can still be visible and frustrating.

In some cases, asymmetric blooming may affect edge ghosting. “Asymmetric blooming” is, in some electro-optic media (eg, the copper chromite/titania encapsulated electrophoretic media described in US Pat. No. 7,002,728), from one extreme optical state of a pixel. refers to the phenomenon in which blooming is “asymmetric” in that more blooming occurs during transitions to other extreme optical states than during transitions in the reverse direction; In the media described in this patent, blooming during the black-to-white transition is typically greater than the blooming during the white-to-black transition.

As such, driving methods capable of reducing ghosting or blooming effects are desired.

Accordingly, in an aspect, there is provided a method for driving an electro-optical display having a plurality of display pixels and controlled by a display controller, the display controller associated with a host for providing operational instructions to the display controller, The method includes updating a display with a first image, updating the display with a second image subsequent to the first image, processing image data associated with the first image and the second image to identify display pixels having edge artifacts and generating image data associated with the identified pixels, storing image data associated with the pixels having edge artifacts in a memory location, and initiating a waveform to clear the edge artifacts.

In another embodiment, the subject matter presented herein provides a method for driving an electro-optical display having a plurality of display pixels. The method includes updating a display with a first image, identifying display pixels having edge artifacts after the first image update, applying waveforms designed to remove artifacts to the identified pixels, and applying another image to the display. including updating. In some embodiments, the method may also include determining display pixel gray tone transitions between the first image and the second image. In some other embodiments, the method may include determining display pixels having different gray tones than at least one of its cardinal neighboring pixels, and flagging the identified pixels in a memory associated with a controller of the display. may be

1 illustrates a circuit diagram representing an electrophoretic display;
2 illustrates a circuit model of an electro-optic imaging layer;
3A illustrates an example special pulse pair edge cancellation waveform for pixels going through a white to white transition;
3B illustrates an example special DC unbalanced pulse to cancel white edges for pixels going through a white to white transition;
3C illustrates an exemplary special full white to white drive waveform;
4A illustrates an example special edge cancellation waveform for pixels undergoing a black-to-black transition;
4B illustrates an exemplary special full black-to-black drive waveform;
5A illustrates a screen shot of a display with a blooming or ghosting effect; and
5B illustrates another screen shot of a display with blooming or ghost effect reduction applied in accordance with the subject matter presented herein; and
6 illustrates a sample Global Edge Clearing (GEC) waveform.

The present invention relates to methods for driving electro-optic displays, in particular bi-stable electro-optic displays, and apparatus for use in such methods. More specifically, the present invention relates to driving methods that may allow for reduced “ghosting” and edge effects, and reduced flashing in such displays. The present invention relates particularly, but not exclusively, to particle-based electrophoretic displays in which one or more types of electrically charged particles are present in a fluid and are moved through the fluid under the influence of an electric field to change the appearance of the display. intended for use.

The term “electro-optic” as applied to a material or display is used herein in its conventional sense in imaging technology to refer to a material having first and second display states that differ in at least one optical property, and the material is changed from its first display state to its second display state by application of an electric field to the material. Although an optical property is usually a color perceptible to the human eye, it differs from pseudo-color in the sense of optical transmission, reflectivity, luminescence, or, in the case of displays intended for machine reading, a change in reflectivity of electromagnetic wavelengths outside the visible range. It may also have other optical properties such as

The term "gray state" is used herein in its conventional sense in imaging technology to refer to a state intermediate between two extreme optical states of a pixel, and does not necessarily imply a black-white transition between these two extreme states. . For example, several E Ink patents and published applications mentioned below describe electrophoretic displays where the extreme states are white and deep blue so that the intermediate "gray state" will actually be pale blue. Indeed, as already mentioned, a change in optical state may not be a color change at all. The terms “black” and “white” may be used hereinafter to refer to the two extreme optical states of a display, and usually refer to extreme optical states that are not strictly black and white, eg, the white and dark blue states described above. should be understood as including. The term “monochrome” may be used hereinafter to denote a drive scheme that drives pixels to only those two extreme optical states without intervening gray states.

Some electro-optic materials are solid in the sense that they have solid outer surfaces, but materials may and often have internal liquid or gas filled spaces. Such displays using solid-state electro-optic materials may be referred to hereinafter as “solid electro-optical displays” for convenience. Accordingly, the term “solid electro-optical displays” includes rotating two-color member displays, encapsulated electrophoretic displays, microcell electrophoretic displays and encapsulated liquid crystal displays.

The terms “bistable” and “bistable” include display elements having first and second display states that differ in at least one optical property, and thus, by an addressing pulse of finite duration, any given element At least several times the minimum duration of the addressing pulse for which the state is required to change the state of the display element, to assume either its first or second display state, after the addressing pulse is completed after it is driven. , for example, is used herein in its conventional sense in the art to refer to displays that will last for at least four times. It is shown in US Pat. No. 7,170,670 that some particle-based electrophoretic displays capable of gray scale are stable in their extreme black and white states as well as their intermediate gray states, as are some other types of electro-optic displays. This type of display is properly termed “multi-stable” rather than bistable, although for convenience the term “bistable” may be used herein to cover both bistable and multi-stable displays.

The term “impulse” is used herein in its conventional sense of the integral of a voltage with respect to time. However, some bistable electro-optic media operate as charge transducers, and with such media an alternative definition of impulse, ie, the integration of current over time (which is equal to the total charge applied), may be used. Depending on whether the medium operates as a voltage-time impulse transducer or a charge impulse transducer, an appropriate definition of impulse should be used.

Much of the discussion below will focus on methods for driving one or more pixels of an electro-optic display via a transition 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 denote the overall voltage versus time curve used to achieve a transition from one particular initial gray level to a particular final gray level. Typically such a waveform will include a plurality of waveform elements; wherein these elements are rectangular in nature (ie, a given element includes the application of a constant voltage for a period of time); 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 gray levels for a particular display. The display may use more than one drive scheme; For example, the aforementioned U.S. Patent No. 7,012,600 discloses that the drive scheme may need to be modified depending on parameters such as the time it has been in operation during its lifetime or the temperature of the display, so that the display has multiple uses to be used at different temperatures, etc. It teaches that different driving schemes of may be provided. A set of drive schemes used in this manner may be referred to as a “set of related drive schemes”. It is also possible to use more than one drive scheme at the same time in different areas of the same display, as described in several above-mentioned MEDEOD applications, and the set of drive schemes used in this way is a "set of simultaneous drive schemes" " may also be referred to as

Several types of electro-optic displays are known. One type of electro-optic display is 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 (this type of display is often referred to as a "rotating two-color ball" display, but in some of the above-mentioned patents the term " "rotating two-color member" is preferred as the more accurate one). Such displays use two or more sections with different optical properties, and multiple miniature bodies (typically spherical or cylindrical) having an inner dipole. These bodies are suspended in liquid-filled vacuoles within a matrix, and the vacuoles are filled with liquid so that the bodies rotate freely. The appearance of the display is changed by applying an electric field and thus rotating the bodies to various positions and changing which of the sections of the bodies are visible through the viewing surface. Electro-optical media of this type are typically bistable.

Another type of electro-optic display is in the form of an electrode formed at least in part from an electrochromic medium, for example a semiconducting metal oxide, and a nanochromic film comprising a plurality of reversible color changeable dye molecules attached to the electrode. using an electrochromic medium of See, eg, 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. Nanochromic films of this type are also described, for example, in US Pat. Nos. 6,301,038; 6,870,657; and 6,950,220. Media of this type are also typically bistable.

Another type of electro-optic display is the electrowetting display developed by Philips and described in Hayes, R. A., et al., "Video-Speed Electronic Paper Based on Electrowetting", Nature, 425, 383-385 (2003). It is shown in US Pat. No. 7,420,549 that such electrowetting displays can be bistable.

One type of electro-optic display that has been the subject of intensive 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 influence of an electric field. Electrophoretic displays can have the properties of good brightness and contrast, wide viewing angles, state bistableness, and low power consumption when compared to liquid crystal displays. Nevertheless, problems with the long-term image quality of these displays have prevented their widespread use. For example, the particles that make up electrophoretic displays tend to settle, resulting in insufficient service life for these displays.

As mentioned above, the electrophoretic medium requires the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but the electrophoretic media can be prepared using gaseous fluids; For example, "Electrical toner movement for electronic paper-like display" by Kitamura, T., et al., IDW Japan, 2001, Paper HCS1-1, and "Toner display using insulative particles charged triboelectrically" by Yamaguchi, Y., et al. , IDW Japan, 2001, Paper AMD4-4. See also US Pat. Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic media solves the same types of problems with particle sedimentation as liquid-based electrophoretic media when the media is used in an orientation that allows such sedimentation, for example in a sign that the media is placed in a vertical plane. It seems easy to suffer. Indeed, particle sedimentation appears to be a more serious problem in gas-based electrophoretic media than in liquid-based electrophoretic media, because the lower viscosity of gaseous suspension fluids compared to liquid suspension fluids allows for faster sedimentation of electrophoretic particles. to be.

Numerous patents and applications assigned to, or in the name of, Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various techniques used in encapsulated electrophoresis and other electro-optic media. Such an encapsulated medium comprises a plurality of small capsules, each of which itself comprises an inner phase containing particles that are electrophoretically mobile in the fluid medium, and a capsule wall surrounding the inner phase. Typically, the capsules are themselves held in a polymer binder to form a coherent layer positioned between the two electrodes. Techniques described in these patents and applications include:

(a) electrophoretic particles, fluids and fluid additives; See, eg, US Patent Nos. 7,002,728 and 7,679,814;

(b) capsules, binders and encapsulation processes; See, eg, US Patent Nos. 6,922,276 and 7,411,719;

(c) microcell structures, wall materials, and methods of forming microcells; See, eg, US Patent Nos. 7,072,095 and 9,279,906;

(d) methods for filling and sealing microcells; See, eg, US Patent Nos. 7,144,942 and 7,715,088;

(e) films and sub-assemblies containing electro-optic materials; See, eg, US Patent Nos. 6,982,178 and 7,839,564;

(f) methods used in backplanes, adhesive layers and other auxiliary layers and displays; See, eg, US Patent Nos. 7,116,318 and 7,535,624;

(g) color formation and color adjustment; See, for example, US Pat. Nos. 7,075,502 and 7,839,564;

(h) applications of displays; See, for example, U.S. Patent Nos. 7,312,784; See No. 8,009,348;

(i) non-electrophoretic displays such as those described in US Pat. Nos. 6,241,921 and US Patent Application Publication No. 2015/0277160; and applications of encapsulation and microcell technology other than displays; See, eg, US Patent Application Publication Nos. 2015/0005720 and 2016/0012710; and

(j) methods for driving displays; 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 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; 2010/026561; 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; No. 2015/0070744; No. 2015/0097877; No. 2015/0109283; No. 2015/0213749; No. 2015/0213765; No. 2015/0221257; No. 2015/0262255; 2016/0071465; 2016/0078820; 2016/0093253; 2016/0140910; and 2016/0180777.

Many of the aforementioned patents and applications show that in an encapsulated electrophoretic medium the walls surrounding the individual microcapsules are replaced by a continuous phase, so that the electrophoretic medium is composed of a plurality of individual droplets of an electrophoretic fluid and a polymer material. It is possible to fabricate so-called polymer dispersed electrophoretic displays comprising a continuous phase, and individual droplets of electrophoretic fluid in such polymer dispersed electrophoretic displays can be encapsulated in capsules or It is recognized that they may be considered as microcapsules; See, eg, US Publication No. 2002/0131147. Accordingly, for the purposes of this application, such polymer dispersed electrophoretic media are regarded as subspecies of encapsulated electrophoretic media.

A related type of electrophoretic display is the so-called "microcell electrophoretic display". In microcell electrophoretic displays, the charged particles and suspending fluid are not encapsulated in microcapsules, but are instead held in a plurality of cavities formed in a carrier medium, such as a polymer film. . For example, both are Sipix Imaging, Inc. See International Application Publication No. WO 02/01281, assigned to , and published US Application No. 2002/0075556.

Many of the aforementioned E Ink and MIT patents and applications also contemplate microcell electrophoretic displays and polymer dispersed electrophoretic displays. The term “encapsulated electrophoretic displays” may refer to all such display types, which may also be described collectively as “microcavity electrophoretic displays” to generalize through the morphology of walls.

Another type of electro-optic display is the electrowetting display developed by Philips and described in Hayes, R. A., et al., "Video-Speed Electronic Paper Based on Electrowetting", Nature, 425, 383-385 (2003). That such electrowetting displays can be bistable is shown in co-pending application Ser. No. 10/711,802, filed Oct. 6, 2004.

Other types of electro-optic materials may also be used. Of particular interest is that bistable ferroelectric liquid crystal displays (FLCs) are known in the art and exhibit residual voltage behavior.

Although electrophoretic media are opaque (for example, because, in many electrophoretic media, particles substantially block the transmission of visible light through the display) and may operate in a reflective mode, some electrophoretic displays have one display state. can be made to operate in a so-called "shutter mode", in which is substantially opaque and one is transmissive. For example, US Pat. Nos. 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. Dielectrophoretic displays similar to electrophoretic displays but dependent on variations in electric field strength can operate in a similar mode; See U.S. Patent No. 4,418,346. Other types of electro-optic displays may also be operable in shutter mode.

A high resolution display may include individual pixels that are addressable without interference from adjacent pixels. One way to obtain such pixels is to provide an array of non-linear elements, such as transistors or diodes, to produce an “active matrix” display, with at least one non-linear element associated with each pixel. The addressing or pixel electrode addressing one pixel is connected to an appropriate voltage source via an associated non-linear element. When the non-linear element is a transistor, the pixel electrode may be connected to the drain of the transistor, and this arrangement will be assumed in the following description, but it is arbitrary in nature and the pixel electrode may be connected to the source of the transistor. In high resolution arrays, pixels may be arranged in a two-dimensional array of rows and columns, such that any particular pixel is uniquely defined by the intersection of one specified row and one specified column. The sources of all transistors in each column may be connected to a single column electrode, while the gates of all transistors in each row may be connected to a single row electrode; Again the assignment of sources to rows and the assignment of gates to columns may be reversed if desired.

The display may be written in a row-by-row fashion. The row electrodes are coupled to a row driver, which applies a voltage to the selected row electrode, such as to ensure that all transistors in the selected row are conductive, such that all transistors in these unselected rows are non-conducting. A voltage may be applied to all other rows to ensure that they remain in the adult state. The column electrodes are coupled to column drivers, which place selected voltages on the various column electrodes to drive the pixels in the selected row to their desired optical states. (The voltages described above may be provided on opposite sides of the electro-optic medium from a non-linear array and are relative to a common front electrode that extends across the entire display. As is known in the art, voltage is relative and the voltage between two points is relative. It is a measure of the charge differential. One voltage value is relative to another voltage value. For example, zero voltage (“0V”) refers to no voltage difference with respect to the other voltages). After a preselected interval known as " , the selected row is deselected, another row is selected, and the voltages on the column drivers are changed to write the next line of the display.

However, in use, certain waveforms may create a residual voltage for the pixels of an electro-optic display, which, as is evident from the discussion above, creates some undesirable optical effects and is generally undesirable. not.

As presented herein, a “shift” in an optical state associated with an addressing pulse is such that the first application of a particular addressing pulse to the electro-optic display results in a first optical state (eg, a first gray tone), Refers to a situation in which subsequent application of the same addressing pulse to an electro-optic display results in a second optical state (eg, a second gray tone). Since the voltage applied to a pixel of an electro-optic display during application of the addressing pulse comprises the sum of the residual voltage and the voltage of the addressing pulse, the residual voltages may cause a shift in the optical state.

"Drift" in the optical state of a display over time refers to a situation in which the optical state of an electro-optic display changes while the display is stationary (eg, during periods in which no addressing pulses are applied to the display) do. Because the optical state of a pixel may depend on the residual voltage of the pixel, and the residual voltage of a pixel may decay over time, residual voltages may cause drift in the optical state.

As discussed above, “ghosting” refers to a situation in which after the electro-optic display has been rewritten, traces of the previous image(s) are still visible. Residual voltages may cause “edge ghosting,” a type of ghosting, in which the outline (edge) of a portion of the previous image remains visible.

Exemplary EPD

1 shows a schematic diagram of a pixel 100 of an electro-optic display according to the subject matter proposed herein. Pixel 100 may include an imaging film 110 . In some embodiments, imaging film 110 may be bistable. In some embodiments, imaging film 110 may include, without limitation, an encapsulated electrophoretic imaging film, which may include, for example, charged pigment particles.

The imaging film 110 may be disposed between the front electrode 102 and the back electrode 104 . The front electrode 102 may be formed between the imaging film and the front surface 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 without limitation indium tin oxide (ITO). The back electrode 104 may be formed opposite the front electrode 102 . In some embodiments, a parasitic capacitance (not shown) may be formed between the front electrode 102 and the back electrode 104 .

Pixel 100 may be one of a plurality of pixels. A plurality of 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 one specified row and one specified column. In some embodiments, the matrix of pixels may be an “active matrix,” where each pixel is associated with at least one non-linear circuit element 120 . The nonlinear circuit element 120 may be coupled between the backplate electrode 104 and the addressing electrode 108 . In some embodiments, nonlinear element 120 may include a diode and/or a transistor, including, without limitation, a MOSFET. A drain (or source) of the MOSFET may be coupled to a backplate electrode 104 , a source (or drain) of the MOSFET may be coupled to an addressing electrode 108 , and the gate of the MOSFET may be coupled to the activation and deactivation of the MOSFET may be coupled to a driver electrode 106 configured to control (For the sake of brevity, the terminal of the MOSFET coupled to the backplate electrode 104 will be referred to as the drain of the MOSFET, and the terminal of the MOSFET coupled to the addressing 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 a MOSFET may be interchanged.)

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 are the same row electrode. may be connected to The row electrodes may be coupled to a row driver, which by applying a voltage to the selected row electrodes sufficient to activate the non-linear elements 120 of all pixels 100 in the selected row(s). One or more rows of pixels may be selected. The column electrodes may be coupled to column drivers, which may place on the addressing electrode 106 of the selected (activated) pixel a voltage suitable to drive the pixel to the desired optical state. The voltage applied to the addressing electrode 108 may be relative to the voltage applied to the front plate electrode 102 of the pixel (eg, a voltage of approximately zero volts). In some embodiments, the front plate electrodes 102 of all pixels in the active matrix may be coupled to a common electrode.

In some embodiments, the pixels 100 of the active matrix may be written in a row-by-row manner. For example, a row of pixels may be selected by a row driver, and voltages corresponding to desired optical states for the row of pixels may be applied to the pixels by column drivers. After a preselected interval known as "line address time", the selected row may be deselected, another row may be selected, and the voltages on the column drivers may be changed so that another line of the display is written.

2 shows a circuit model of an electro-optic imaging layer 110 disposed between a front electrode 102 and a back electrode 104 according to the subject matter presented herein. Resistor 202 and capacitor 204 may represent the resistance and capacitance of electro-optic imaging layer 110 , front electrode 102 , and back electrode 104 , including any adhesive layers. Resistor 212 and capacitor 214 may represent the resistance and capacitance of the lamination adhesive layer. Capacitor 216 is disposed between front electrode 102 and back electrode 104 , eg, interfacial contact areas between layers, such as between an imaging layer and a lamination adhesive layer and/or between a lamination adhesive layer and a backplane electrode. It may also represent the capacitance that may be formed at the interface. The voltage Vi across the imaging film 110 of the pixel may include the residual voltage of the pixel.

Detecting and reducing or eliminating edge artifacts and ghosting in the electro-optic display described above will likely require additional image data processing, and US Patent Publication No. 2013/0194250 A1 to Amundson et al. (“Amundson”) and US Patent Publication No. 2016/0225322 A1 (“Sim”) to Sim et al., are some image data processing methods that may be employed, all of which are incorporated herein in their entirety. However, such image data processing methods and also clearing of edge artifacts and pixel ghosting may require their own processing time, which may not always be available. As such, in a fast-paced updating waveform mode, such as the direct update waveform mode described below, it may be desirable to perform image data processing concurrently with the image data updating process. Additionally, edge artifact and pixel ghosting clearing may be triggered and performed only if desired.

Direct update or DUDS

In some applications, the display may use a fast-paced updating waveform mode, such as a “direct update” waveform mode (“DUDS). DUDS can achieve transitions between all possible gray levels, typically gray Although it may have two or more gray levels, less than a scale driven scheme ("GSDS), the most important feature of DUDS is a simple one-way from initial gray level to final gray level, in contrast to the "indirect" transitions often used in GSDS. Transitions are handled by driving, wherein in at least some transitions a pixel is driven from an initial gray level to one extreme optical state and then in the reverse direction to a final gray level; In some cases, the transition may be achieved by driving from an initial gray level to one extreme optical state, then to an opposite extreme optical state, and only then to a final extreme optical state—eg, the United States described above. Reference is made to the drive scheme illustrated in FIGS. 11A and 11B of Patent No. 7,012,600. Thus, the present electrophoretic displays are characterized by about two to about two to about the length of a saturation pulse (where "length of saturation pulse" is defined as a period of time sufficient to drive, at a particular voltage, a pixel of the display from one extreme optical state to another). DUDS has a maximum update time equal to the length of the saturation pulse, or about 200-300 milliseconds, while it may have an update time in triple grayscale mode, or approximately 700-900 milliseconds.

It should be noted that the direct update (DU) waveform mode or drive scheme described above is used herein to describe the general working principles of the subject matter disclosed herein. It is not intended to serve as a limitation on the present subject matter. These working principles can be readily applied to other waveform modes or schemes.

The DU waveform mode is a driving scheme that usually considers updates to white and black with no self-transitions. DU mode minimizes the appearance of "flash" transitions, so will have short update times to quickly bring up black and white, where the display will appear flickering and may be visually unsightly to some viewers . DU mode may sometimes be used to bring up menus, progress bars, keyboards, etc., on the display screen. Because both white-to-white and black-to-black transitions are null (ie, undriven) in DU mode, edge artifacts may occur in black and white backgrounds.

As explained above, when an undriven pixel is placed adjacent to the pixel being updated, driving of the driven pixel causes a change in optical state over an area slightly larger than that of the driven pixel and this area is adjacent to A phenomenon known as "blooming" occurs when it enters a region of pixels. Such blooming manifests itself as edge effects along edges where undriven pixels lie adjacent to driven pixels. Similar when using regional updates (where only a specific region of the display is updated to show an image for example), except that with regional updates, edge effects occur at the boundary of the updated region. Edge effects occur. Over time, such edge effects are visually distracting and must be cleared. To date, such edge effects (and effects of color drift in undriven white pixels) have typically been eliminated by using a single global clearing or GC update at intervals. Unfortunately, the use of such occasional GC updates may re-introduce the problem of "flash" updates, and in practice the flashiness of updates may be increased by the fact that flash updates only occur over a long period of time.

Simultaneous image updating and edge artifacts data processing

In comparison, some of the display pixel edge artifacts reduction methods may incur additional latency due to image processing designed to detect and remove edge artifacts after each image update. Further, the use of DC unbalanced waveforms in these reduction methods would not be feasible because the small dwell time between updates (such as the DU mode presented above) does not allow sufficient time to perform the post drive discharge. will be. And without post-drive discharge, there is a potential risk to overall optical performance and module reliability.

Alternatively, in some embodiments, image data processing, such as those described in Amundson and Sim, may be executed concurrently with the image updating process. For example, when display 100 is updating a first image, the image data of the first and subsequent second images may be processed to identify pixels that may create edge artifacts or other undesirable optical defects. have. Subsequently, such data may be stored in buffer memory so that an edge artifact clearing process is performed at a later time. In some embodiments, this data processing of images may occur when subsequent images are being supplied to the EPDC. In some other embodiments where it is known which images will be updated to the display, this data processing of images may occur before subsequent images are updated.

One way to track or generate and store this edge artifacts information as an electro-optic display undergoes optical changes is to generate a map, where the map indicates which pixels in the display are likely to cause edge artifacts. It may contain information such as One such method is described in US Patent Application No. US 2016/128,996 to Sim et al., which is incorporated herein in its entirety.

For example, in some embodiments, pixel edge artifacts generated under the driving scheme or waveform modes may be stored in a memory (eg, a binary map), eg, each display pixel is i,j), pixels that may introduce edge artifacts may be flagged and their map information (ie, MAP(i,j) specifier) may be stored in a binary map. One approach that may be used to track edge artifacts generated on a map and flag those pixels is illustrated below:

In this approach, when certain conditions are met, the display pixel designated MAP(i,j) may be flagged with a numerical value of 1 indicating that dark edge artifacts have formed on this pixel. Some of the required conditions may include, (1). These display pixels are undergoing a white-to-white transition; (2). All four cardinal neighbors (ie, the four nearest neighboring pixels) have the next gray tone of white; and (3). At least one cardinal neighbor has a current gray tone that is not white; and (4). None of the neighboring pixels (ie, 4 cardinal neighbors and also diagonal neighbors) are currently flagged for edge artifacts.

Similarly, when certain conditions are met, the display pixel MAP(i,j) may be flagged with a number 2 indicating that white edges have been formed on this pixel. Some of the required conditions may include, (1). This pixel is going through a black-to-black transition; (2). at least one cardinal neighbor has a current gray tone that is not black and the next gray tone is black; and (3). None of the neighboring pixels (ie, 4 cardinal neighbors and also diagonal neighbors) are currently flagged for edge artifacts.

In use, one advantage of this approach is that the above-mentioned image processing (ie map generation and pixel flagging) may occur concurrently with display image updating cycles, whereby, at least in part, the generated map is only updated It is possible to avoid creating extra latencies for updating cycles, due to the fact that it is only required at the completion of a cycle.

Once the update mode has been completed (e.g., the display stops using a particular update mode), the pixel information accumulated by the generated map is later (e.g., out waveform mode) ) may be used to clear edge artifacts. For example, pixels flagged for edge artifacts may be cleared with a low flash waveform with specialized waveforms.

In some embodiments, full clearing white to white and black to black waveforms along with special edge clearing white to white and black to black waveforms may be used to clear edge artifacts. Balanced pulse pairs described, for example, in US Patent Application No. 2013/0194250, which are incorporated herein in their entirety, describe the following;

In this approach, a DU_OUT transition scheme (eg, a modified DU scheme with an edge artifact reduction algorithm included) may be applied to pixels that are not undergoing a white-to-white or black-to-black transition, for example, these pixels They may receive normal transition updates as if they were under a normal DU drive scheme. Otherwise, for a pixel that has dark edge artifacts (ie, MAP(i,j) = 1) and is going through a white-to-white transition, a special full white-to-white waveform may be applied. In some embodiments, this white to white waveform may be a waveform similar to that illustrated in FIG. 3C , which may be substantially DC balanced, which means that the sum of the magnitude and time voltage bias supply is all substantially zero. it means; Otherwise, if the pixel is going through a white-to-white transition, and at least one cardinal neighbor has a dark edge artifact (i.e., MAP(i,j) = 1), then a special edge-clearing white-to-white waveform is applied ( For example, Fig. 3a); Also, if a pixel has a white edge artifact (ie, MPA(i,j) = 2) and is going through a black-to-black transition, a special full black-to-black waveform, as illustrated in FIG. 4B , may be applied; Also, if a pixel is going through a black-to-black transition, and at least one cardinal neighbor is flagged for a white edge artifact (ie, MAP(i,j) = 2), then special edge cancellation, as illustrated in FIG. 4A , apply a black-to-black waveform; In other cases, waveforms from the DU-OUT waveform table are used to apply black-to-black or white-to-white transition waveforms to all other pixels.

Using the aforementioned method, the full clearing white to white and black to black waveforms are used along with the special edge clearing white to white and black to black waveforms to clear edge artifacts. In some embodiments, the special edge clearing white to white waveform is a pulse pair as described in US Patent Publication No. 2013/0194250 to Amundson et al., which is incorporated herein in its entirety, or white as illustrated in FIG. 3B . can take the form of DC unbalanced pulse drive of , in which case the post drive discharge described herein may be used to discharge residual voltages and reduce device stresses. Similarly, a DC unbalanced pulse, as illustrated in FIG. 4A , may be used to drive a pixel to black, in which case a post drive discharge may be performed again. As illustrated in FIG. 4 , such a DC unbalanced pulse is only driven to positive 15 volts for a period of time. In this configuration, good edge clearing performance can be achieved at the expense of small transient appearance defects (eg, flashes) due to the use of a special full clearing waveform.

In another embodiment, transition appearance defects (eg, flashes) may be reduced using an alternative implementation described below.

In this approach, instead of using specialized edge clearing waveforms as described in the first method above, DC unbalanced waveforms may be used to clear edge artifacts. In some instances, post drive discharges may be used to reduce hardware stress due to unbalanced waveforms. In use, if a display pixel is not undergoing either a white-to-white or black-to-black transition, a normal DU-OUT transition is applied to the pixel. Otherwise, if a display pixel is identified as having dark edge artifacts (i.e., MAP(i,j) = 1) and is going through a white-to-white transition, then a DC unbalanced drive pulse causes the pixel to be white (e.g., a pulse similar to that illustrated in Figure 3b); Otherwise, if a display pixel is identified as having white edge artifacts (ie, MAP(i,j) = 2) and is undergoing a black-to-black transition, then a DC unbalanced drive pulse (eg, as illustrated in FIG. 4A ) a pulse similar to that shown above) is applied to drive the pixel to black; Otherwise, invoke black-to-black or white-to-white transitions of the DU-OUT waveform table to the display pixels.

In another embodiment, instead of storing edge artifact information in a designated memory location, edge artifact information in an image buffer associated with a controller unit (EPDC) of the display (eg, using a next image buffer associated with the controller unit) can also take out

In this approach, for a pixel going through a white-to-white transition and for all its four cardinal neighbors with the next graytone of white, if the current graytone of at least one cardinal neighbor is not white, then a special white-to-white set the next graytone of the pixel as the image state; Otherwise, if the graytone transition of a pixel is black to black, and at least one cardinal neighbor has a current graytone that is not black and a next graytone that is black, then the next graytone of the pixel is a special black-to-black image in the next image buffer. state is set In use, during an update cycle, the special white-to-white and special black-to-black image states may be identical to the white-to-white and black-to-black image states for image processing and for application of waveform transitions. For the application of waveform transition, this means:

특수 화이트 상태

화이트 상태 (즉, 화이트 상태 투 화이트 상태) 는 파형 룩업 테이블의 화이트 상태

화이트 상태 (즉, 화이트 상태 투 화이트 상태) 와 등가이다

special white state

The white state (i.e., white state to white state) is the white state in the waveform lookup table.

is equivalent to the white state (i.e. the white state to the white state)

특수 화이트 상태

임의의 그레이 상태들 (즉, 화이트 상태 투 임의의 그레이 상태) 은 파형 룩업 테이블 등의 화이트 상태

임의의 그레이 상태들 (즉, 화이트 상태 투 임의의 그레이 상태) 과 등가이다

special white state

Any gray state (ie, white state to any gray state) is a white state in a waveform lookup table, etc.

is equivalent to any gray state (ie, white state to any gray state)

특수 블랙 상태

블랙 상태 (즉, 블랙 상태 투 블랙 상태) 는 파형 룩업 테이블의 블랙 상태

블랙 상태 (즉, 블랙 상태 투 블랙 상태) 와 등가이다

special black state

The black state (i.e. black state to black state) is the black state in the waveform lookup table.

is equivalent to the black state (i.e. black state to black state)

특수 블랙 상태

임의의 그레이 상태들 (즉, 블랙 상태 투 임의의 그레이 상태) 은 파형 룩업 테이블 등의 블랙 상태

임의의 그레이 상태들 (즉, 블랙 상태 투 임의의 그레이 상태) 과 등가이다

special black state

Any gray state (ie, black state to any gray state) is a black state such as a waveform lookup table.

is equivalent to any gray state (ie, black state to any gray state)

During the output mode, the special white state to white state received a DC imbalance pulse as white (eg, FIG. 3B illustrates an exemplary such pulse) and the special black state to black state turns the DC imbalance pulse into black received (eg, FIG. 4A illustrates an example such pulse). Imaging algorithm processing occurs in the background during DU mode updating, meaning that DU updating time can be used to process images.

5A and 5B illustrate displays without edge artifacts reduction applied and with edge artifacts reduction applied. Indeed, when no edge artifact reduction is applied, white edges on a black background are clearly visible, as shown in FIG. 5A . In contrast, FIG. 5B shows that the white edges are cleared using one of the proposed methods presented herein.

In some embodiments, pixels that have or may potentially cause edge artifacts may be flagged as described above and stored in a different memory location than the memory buffer used for image updating. For example, a memory physically separate from the buffer memory is used for image updating. However, in some cases, it may be desirable to reduce the amount of memory used. As such, in some embodiments, memory used for image updating (eg, image updating buffer memory) may also be used to store cumulative edge artifacts information. For example, while an electro-optic display is undergoing optical changes (eg, image updates), instead of creating a map with all pixels, individual pixels are designed to indicate if a particular pixel has edge artifacts. It may be associated with an indicator. This indicator can be used to indicate whether a particular pixel is flagged for edge artifacts. As the display undergoes more image updates (eg, more optical changes), perhaps more pixels may be flagged for edge artifacts (eg, as these pixels are flagged or turned on). associated edge artifact indicator). Later, these pixels flagged for edge artifact may all be reset or cleared together by the reset waveform.

Edge Artifact Clearing

The processed edge artifact data may be used at a convenient time to clear edge artifacts. The clearing process may be triggered or initiated by various conditions.

In some embodiments, a clearing request may be initiated by a host (eg, a processor), similar to another request sent by a host to the EPDC, and such request may be sent concurrently with other image updating requests. may be For example, according to the interaction dialog where the DUDS waveform mode was used to update the display, for clearing the accumulated edge artifacts due to the DUDS waveform mode, the host is asked to set a specific time frame for clearing the edge artifacts. You may also request it from the EPDC.

In some other embodiments, the clearing process may be initiated when convenient for the display. For example, when the EPDC is idle for a certain amount of time, the EPDC may elect to initiate a clearing process to clear the edge artifacts using the accumulated edge artifacts data.

In another embodiment, this processed image data comprising identification data of pixels with edge artifacts may be used by a driving scheme or updating waveform mode that includes waveforms for clearing edge artifacts. For example, in an application to a pen input where the DUDS waveform mode is used for its fast response time, the subsequent waveform mode used for anti-aliasing may include edge artifacts clearing waveforms, and this subsequent waveform mode is To clear edge artifacts, processed image data with edge artifacts information may be utilized.

In some embodiments, a global edge clearing (GEC) waveform mode may be used to clear edge artifacts. 6 illustrates a sample GEC waveform comprising top-off pulses configured to drive a display pixel to an extreme optical state. Such a waveform may consist of 6 frames at 25 degrees Celsius or a duration of 66 ms. GEC may be shorter in duration compared to waveform mode with built-in edge clearing portions. In this way, the GEC may be conveniently employed to clear edges with respect to various existing drive waveform modes without introducing excessive latencies. For example, when GEC is used with the DUDS waveform mode mentioned above, a post-drive discharge may be performed following the GEC before the subsequent image is updated on the display, since GEC only occupies a short duration. In some embodiments, the EPDC may pick a waveform to use depending on the amount of edge artifacts present. For example, if the amount of edge artifacts exceeds a threshold, the EPDC may select a global clearing waveform (mode) to clear the entire display.

In another embodiment, the EPDC may initiate a clearing waveform when there are too many pixels with edge artifacts. For example, the EPDC may have an algorithm configured to track the total number of pixels with edge artifacts and make a comparison to the total number of pixels in the display. Such comparisons may be stored as percentile values in buffer memory. Such a stored value may be periodically compared to a predetermined threshold value, and if the stored value exceeds the threshold, the EPDC may elect to initiate a global clearing waveform mode, wherein the global clearing waveform resets all pixels in the display. You can also (e.g., drive every pixel to an extreme grayscale level or color state).

It will be apparent to those skilled in the art that many changes and modifications can be made to the specific embodiments of the invention described above without departing from the scope of the invention. Accordingly, all of the above description should be interpreted in an illustrative rather than a restrictive sense.

Claims (8)

A method for driving an electro-optical display having a plurality of display pixels and controlled by a display controller, the method comprising:
The display controller is associated with a host for providing operational instructions to the display controller, the method comprising:
updating the display with a first image;
updating the display with a second image subsequent to the first image;
processing image data associated with the first image and the second image to identify display pixels having edge artifacts and to generate image data associated with the identified pixels;
storing the generated image data associated with the identified pixels in a memory location; and
initiating a waveform for clearing the edge artifacts;
The method is:
updating the display with a third image following the second image;
the processing of the image data associated with the first image and the second image is effected concurrently with the updating of the third image;
wherein the initiation of the waveform to clear the edge artifacts is effected in response to a request initiated by the host.
A method for driving an electro-optic display. The method of claim 1,
and generating image data associated with the identified pixels comprises flagging the identified pixels as an indicator. 3. The method of claim 2,
wherein identifying display pixels having edge artifacts comprises determining display pixels having different gray tones than at least one of its cardinal neighboring pixels. 3. The method of claim 2,
and identifying display pixels having edge artifacts comprises flagging the identified pixels in a buffer memory associated with the display controller. The method of claim 1,
Initiating a series of waveforms comprises receiving a clearing command from the host. The method of claim 1,
wherein initiating a series of waveforms includes the display controller initiating a clearing waveform after an idle state for a predetermined duration. The method of claim 1,
Initiating the series of waveforms includes applying a waveform mode having the waveforms to clear edge artifacts. The method of claim 1,
Initiating a series of waveforms comprises applying a DC unbalanced waveform.

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