This invention relates to methods for driving electro-optic displays. More specifically, this invention relates to driving methods for displaying videos.
Particle-based electrophoretic displays have been the subject of intense research and development for a number of years. In such displays, a plurality of charged particles (sometimes referred to as pigment particles) move through a fluid under the influence of an electric field. The electric field is typically provided by a conductive film or a transistor, such as a field-effect transistor. Electrophoretic displays have good brightness and contrast, wide viewing angles, state bistability, and low power consumption when compared with liquid crystal displays. Such electrophoretic displays have slower switching speeds than LCD displays. Additionally, the electrophoretic displays can be sluggish at low temperatures because the viscosity of the fluid limits the movement of the electrophoretic particles. Despite these shortcomings, electrophoretic displays can be found in everyday products such as electronic books (e-readers), mobile phones and mobile phone covers, smart cards, signs, watches, shelf labels, and flash drives.
Many commercial electrophoretic media essentially display only two colors, with a gradient between the black and white extremes, known as “grayscale.” Such electrophoretic media either use a single type of electrophoretic particle having a first color in a colored fluid having a second, different color (in which case, the first color is displayed when the particles lie adjacent the viewing surface of the display and the second color is displayed when the particles are spaced from the viewing surface), or first and second types of electrophoretic particles having differing first and second colors in an uncolored fluid. In the latter case, the first color is displayed when the first type of particles lie adjacent the viewing surface of the display and the second color is displayed when the second type of particles lie adjacent the viewing surface). Typically the two colors are black and white.
Although seemingly simple, electrophoretic media and electrophoretic devices display complex behaviors. For instance, it has been discovered that good video displaying requires more than simple “on/off” voltage pulses. Rather, complicated “waveforms” are needed to drive the particles between states and to assure the produced videos are of sufficiently good quality. As such, there exists a need for driving methods to perform video displaying in electrophoretic displays.
This invention provides a method for driving an electro-optic display having a plurality of display pixels, the method includes dithering a grayscale image into a black and white image, updating the plurality of display pixels to display the black and white image, and converting the black and white image back to the grayscale image.
In some embodiments, the method may further include applying a waveform configured to remove artifacts from the plurality of display pixels. In some other embodiments, the step of dithering the grayscale image into a black and white image comprises using a half-toning algorithm. And in another embodiment, the half-toning algorithm is a green noise half-toning algorithm.
The present invention relates to methods for driving electro-optic displays, especially bistable electro-optic displays, and to apparatus for use in such methods. More specifically, this invention relates to driving methods for display vidoes. This invention is especially, but not exclusively, intended for use with 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.
The term “electro-optic”, as applied to a material or a display, is used herein in its conventional meaning in the imaging art to refer to a material having first and second display states differing in at least one optical property, the material being changed from its first to its second display state by application of an electric field to the material. Although the optical property is typically color perceptible to the human eye, it may be another optical property, such as optical transmission, reflectance, luminescence or, in the case of displays intended for machine reading, pseudo-color in the sense of a change in reflectance of electromagnetic wavelengths outside the visible range.
The term “gray state” is used herein in its conventional meaning in the imaging art to refer to a state intermediate two extreme optical states of a pixel, and does not necessarily imply a black-white transition between these two extreme states. For example, several of the E Ink patents and published applications referred to below describe electrophoretic displays in which the extreme states are white and deep blue, so that an intermediate “gray state” would actually be pale blue. Indeed, as already mentioned, the 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 should be understood as normally including extreme optical states which are not strictly black and white, for example, the aforementioned white and dark blue states. The term “monochrome” may be used hereinafter to denote a drive scheme which only drives pixels to their two extreme optical states with no intervening gray states.
Some electro-optic materials are solid in the sense that the materials have solid external surfaces, although the materials may, and often do, have internal liquid- or gas-filled spaces. Such displays using solid electro-optic materials may hereinafter for convenience be referred to as “solid electro-optic displays”. Thus, the term “solid electro-optic displays” includes rotating bichromal member displays, encapsulated electrophoretic displays, microcell electrophoretic displays and encapsulated liquid crystal displays.
The terms “bistable” and “bistability” are used herein in their conventional meaning in the art to refer to displays comprising display elements having first and second display states differing in at least one optical property, and such that after any given element has been driven, by means of an addressing pulse of finite duration, to assume either its first or second display state, after the addressing pulse has terminated, that state will persist for at least several times, for example at least four times, the minimum duration of the addressing pulse required to change the state of the display element. It is shown in U.S. Pat. No. 7,170,670 that some particle-based electrophoretic displays capable of gray scale are stable not only in their extreme black and white states but also in their intermediate gray states, and the same is true of some other types of electro-optic displays. This type of display is properly called “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 meaning of the integral of voltage with respect to time. However, some bistable electro-optic media act as charge transducers, and with such media an alternative definition of impulse, namely the integral of current over time (which is equal to the total charge applied) may be used. The appropriate definition of impulse should be used, depending on whether the medium acts as a voltage-time impulse transducer or a charge impulse transducer.
Much of the discussion below will focus on methods for driving one or more pixels of an electro-optic display through 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 entire voltage against time curve used to effect the transition from one specific initial gray level to a specific final gray level. Typically such a waveform will comprise a plurality of waveform elements; where these elements are essentially rectangular (i.e., where a given element comprises application of a constant voltage for a period of time); the elements may be called “pulses” or “drive pulses”. The term “drive scheme” denotes a set of waveforms sufficient to effect all possible transitions between gray levels for a specific display. A display may make use of more than one drive scheme; for example, the aforementioned U.S. Pat. No. 7,012,600 teaches that a drive scheme may need to be modified depending upon parameters such as the temperature of the display or the time for which it has been in operation during its lifetime, and thus a display may be provided with a plurality of different drive schemes to be used at differing temperature etc. A set of drive schemes used in this manner may be referred to as “a set of related drive schemes.” It is also possible, as described in several of the aforementioned MEDEOD applications, to use more than one drive scheme simultaneously in different areas of the same display, and a set of drive schemes used in this manner may be referred to as “a set of simultaneous drive schemes.”
Several types of electro-optic displays are known. One type of electro-optic display is a rotating bichromal member type as described, for example, in U.S. 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 bichromal ball” display, the term “rotating bichromal member” is preferred as more accurate since in some of the patents mentioned above the rotating members are not spherical). Such a display uses a large number of small bodies (typically spherical or cylindrical) which have two or more sections with differing optical characteristics, and an internal dipole. These bodies are suspended within liquid-filled vacuoles within a matrix, the vacuoles being filled with liquid so that the bodies are free to rotate. The appearance of the display is changed by applying an electric field thereto, thus rotating the bodies to various positions and varying which of the sections of the bodies is seen through a viewing surface. This type of electro-optic medium is typically bistable.
Another type of electro-optic display uses an electrochromic medium, for example an electrochromic medium in the form of a nanochromic film comprising an electrode formed at least in part from a semi-conducting metal oxide and a plurality of dye molecules capable of reversible color change attached to the electrode; see, for example O'Regan, B., et al., Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24 (March 2002). See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845. Nanochromic films of this type are also described, for example, in U.S. Pat. Nos. 6,301,038; 6,870,657; and 6,950,220. This type of medium is also typically bistable.
Another type of electro-optic display is an electro-wetting 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 U.S. Pat. No. 7,420,549 that such electro-wetting displays can be made bistable.
One type of electro-optic display, which has been the subject of intense research and development for a number of years, is the 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 attributes of good brightness and contrast, wide viewing angles, state bistability, and low power consumption when compared with liquid crystal displays. Nevertheless, problems with the long-term image quality of these displays have prevented their widespread usage. For example, particles that make up electrophoretic displays tend to settle, resulting in inadequate service-life for these displays.
As noted above, electrophoretic media require the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can be produced using gaseous fluids; see, for example, Kitamura, T., et al., “Electrical toner movement for electronic paper-like display”, IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y., et al., “Toner display using insulative particles charged triboelectrically”, IDW Japan, 2001, Paper AMD4-4). See also U.S. Pat. Nos. 7,321,459 and 7,236,291. Such gas-based electrophoretic media appear to be susceptible to the same types of problems due to particle settling as liquid-based electrophoretic media, when the media are used in an orientation which permits such settling, for example in a sign where the medium is disposed in a vertical plane. Indeed, particle settling appears to be a more serious problem in gas-based electrophoretic media than in liquid-based ones, since the lower viscosity of gaseous suspending fluids as compared with liquid ones allows more rapid settling of the electrophoretic particles.
Numerous patents and applications assigned to or in the names of the Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various technologies used in encapsulated electrophoretic and other electro-optic media. Such encapsulated media comprise numerous small capsules, each of which itself comprises an internal phase containing electrophoretically-mobile particles in a fluid medium, and a capsule wall surrounding the internal phase. Typically, the capsules are themselves held within a polymeric binder to form a coherent layer positioned between two electrodes. The technologies described in these patents and applications include:
(a) Electrophoretic particles, fluids and fluid additives; see for example U.S. Pat. Nos. 7,002,728 and 7,679,814;
(b) Capsules, binders and encapsulation processes; see for example U.S. Pat. Nos. 6,922,276 and 7,411,719;
(c) Microcell structures, wall materials, and methods of forming microcells; see for example U.S. Pat. Nos. 7,072,095 and 9,279,906;
(d) Methods for filling and sealing microcells; see for example U.S. Pat. Nos. 7,144,942 and 7,715,088;
(e) Films and sub-assemblies containing electro-optic materials; see for example U.S. Pat. Nos. 6,982,178 and 7,839,564;
(f) Backplanes, adhesive layers and other auxiliary layers and methods used in displays; see for example U.S. Pat. Nos. 7,116,318 and 7,535,624;
(g) Color formation and color adjustment; see for example U.S. Pat. Nos. 7,075,502 and 7,839,564.
(h) Applications of displays; see for example U.S. Pat. Nos. 7,312,784; 8,009,348;
(i) Non-electrophoretic displays, as described in U.S. Pat. No. 6,241,921 and U.S. Patent Application Publication No. 2015/0277160; and applications of encapsulation and microcell technology other than displays; see for example U.S. Patent Application Publications Nos. 2015/0005720 and 2016/0012710; and
(j) Methods for driving displays; see for example U.S. 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 U.S. Patent Applications 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.
Many of the aforementioned patents and applications recognize that the walls surrounding the discrete microcapsules in an encapsulated electrophoretic medium could be replaced by a continuous phase, thus producing a so-called polymer-dispersed electrophoretic display, in which the electrophoretic medium comprises a plurality of discrete droplets of an electrophoretic fluid and a continuous phase of a polymeric material, and that the discrete droplets of electrophoretic fluid within such a polymer-dispersed electrophoretic display may be regarded as capsules or microcapsules even though no discrete capsule membrane is associated with each individual droplet; see for example, the aforementioned 2002/0131147. Accordingly, for purposes of the present application, such polymer-dispersed electrophoretic media are regarded as sub-species of encapsulated electrophoretic media.
A related type of electrophoretic display is a so-called “microcell electrophoretic display.” In a microcell electrophoretic display, the charged particles and the suspending fluid are not encapsulated within microcapsules but instead are retained within a plurality of cavities formed within a carrier medium, e.g., a polymeric film. See, for example, International Application Publication No. WO 02/01281, and published U.S. Application No. 2002/0075556, both assigned to Sipix Imaging, Inc.
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” can refer to all such display types, which may also be described collectively as “microcavity electrophoretic displays” to generalize across the morphology of the walls.
Another type of electro-optic display is an electro-wetting 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 copending application Ser. No. 10/711,802, filed Oct. 6, 2004, that such electro-wetting displays can be made bistable.
Other types of electro-optic materials may also be used. Of particular interest, bistable ferroelectric liquid crystal displays (FLCs) are known in the art and have exhibited remnant voltage behavior.
Although electrophoretic media may be opaque (since, for example, in many electrophoretic media, the particles substantially block transmission of visible light through the display) and operate in a reflective mode, some electrophoretic displays can be made to operate in a so-called “shutter mode” in which one display state is substantially opaque and one is light-transmissive. See, for example, the patents U.S. Pat. Nos. 6,130,774 and 6,172,798, and U.S. Pat. Nos. 5,872,552; 6,144,361; 6,271,823; 6,225,971; and 6,184,856. Dielectrophoretic displays, which are similar to electrophoretic displays but rely upon variations in electric field strength, can operate in a similar mode; see U.S. Pat. No. 4,418,346. Other types of electro-optic displays may also be capable of operating in shutter mode.
A high-resolution display may include individual pixels which 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, with at least one non-linear element associated with each pixel, to produce an “active matrix” display. An addressing or pixel electrode, which addresses one pixel, is connected to an appropriate voltage source through the 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, although it is essentially arbitrary and the pixel electrode could be connected to the source of the transistor. In high-resolution arrays, the pixels may be arranged in a two-dimensional array of rows and columns, such that any specific pixel is uniquely defined by the intersection of one specified row and one specified column. The sources of all the transistors in each column may be connected to a single column electrode, while the gates of all the transistors in each row may be connected to a single row electrode; again the assignment of sources to rows and gates to columns may be reversed if desired.
The display may be written in a row-by-row manner. The row electrodes are connected to a row driver, which may apply to a selected row electrode a voltage such as to ensure that all the transistors in the selected row are conductive, while applying to all other rows a voltage such as to ensure that all the transistors in these non-selected rows remain non-conductive. The column electrodes are connected to column drivers, which place upon the various column electrodes voltages selected to drive the pixels in a selected row to their desired optical states. (The aforementioned voltages are relative to a common front electrode which may be provided on the opposed side of the electro-optic medium from the non-linear array and extends across the whole display. As in known in the art, voltage is relative and a measure of a charge differential between two points. One voltage value is relative to another voltage value. For example, zero voltage (“0V”) refers to having no voltage differential relative to another voltage.) After a pre-selected interval known as the “line address time,” a selected row is deselected, another row is selected, and the voltages on the column drivers are changed so that the next line of the display is written.
However, in use, certain waveforms may produce a remnant voltage to pixels of an electro-optic display, and as evident from the discussion above, this remnant voltage produces several unwanted optical effects and is in general undesirable.
As presented herein, a “shift” in the optical state associated with an addressing pulse refers to a situation in which a first application of a particular addressing pulse to an electro-optic display results in a first optical state (e.g., a first gray tone), and a subsequent application of the same addressing pulse to the electro-optic display results in a second optical state (e.g., a second gray tone). Remnant voltages may give rise to shifts in the optical state because the voltage applied to a pixel of the electro-optic display during application of an addressing pulse includes the sum of the remnant voltage and the voltage of the addressing pulse.
A “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 at rest (e.g., during a period in which an addressing pulse is not applied to the display). Remnant voltages may give rise to drifts in the optical state because the optical state of a pixel may depend on the pixel's remnant voltage, and a pixel's remnant voltage may decay over time.
The “ghosting” effect refers to a situation in which, after the electro-optic display has been rewritten, traces of the previous image(s) are still visible. Remnant voltages may give rise to “edge ghosting,” a type of ghosting in which an outline (edge) of a portion of a previous image remains visible.
An exemplary EPD
Imaging film 110 may be disposed between a front electrode 102 and a rear electrode 104. Front electrode 102 may be formed between the imaging film and the front of the display. In some embodiments, front electrode 102 may be transparent. In some embodiments, front electrode 102 may be formed of any suitable transparent material, including, without limitation, indium tin oxide (ITO). Rear electrode 104 may be formed opposite a front electrode 102. In some embodiments, a parasitic capacitance (not shown) may be formed between front electrode 102 and rear electrode 104.
Pixel 100 may be one of a plurality of pixels. The plurality of pixels may be arranged in a two-dimensional array of rows and columns to form a matrix, such that any specific 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,” in which each pixel is associated with at least one non-linear circuit element 120. The non-linear circuit element 120 may be coupled between back-plate electrode 104 and an addressing electrode 108. In some embodiments, non-linear element 120 may include a diode and/or a transistor, including, without limitation, a MOSFET. The drain (or source) of the MOSFET may be coupled to back-plate electrode 104, the source (or drain) of the MOSFET may be coupled to addressing electrode 108, and the gate of the MOSFET may be coupled to a driver electrode 106 configured to control the activation and deactivation of the MOSFET. (For simplicity, the terminal of the MOSFET coupled to back-plate electrode 104 will be referred to as the MOSFET's drain, and the terminal of the MOSFET coupled to addressing electrode 108 will be referred to as the MOSFET's source. However, one of ordinary skill in the art will recognize that, in some embodiments, the source and drain of the MOSFET may be interchanged.)
In some embodiments of the active matrix, the addressing electrodes 108 of all the pixels in each column may be connected to a same column electrode, and the driver electrodes 106 of all the pixels in each row may be connected to a same row electrode. The row electrodes may be connected to a row driver, which may select one or more rows of pixels by applying to the selected row electrodes a voltage sufficient to activate the non-linear elements 120 of all the pixels 100 in the selected row(s). The column electrodes may be connected to column drivers, which may place upon the addressing electrode 106 of a selected (activated) pixel a voltage suitable for driving the pixel into a desired optical state. The voltage applied to an addressing electrode 108 may be relative to the voltage applied to the pixel's front-plate electrode 102 (e.g., a voltage of approximately zero volts). In some embodiments, the front-plate electrodes 102 of all the 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 the row driver, and the voltages corresponding to the desired optical states for the row of pixels may be applied to the pixels by the column drivers. After a pre-selected interval known as the “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.
In practice, conventional video rate displays using non-bistable media, such as the phosphors on cathode ray tubes and conventional liquid crystal displays, require frame rates in excess of about 25 frames per second (fps) to provide acceptable video quality. (Video display at 15 fps is common on internet videos but results in a noticeable lack of video quality.) However, it is been found that bistable, and certain other, electro-optic displays can produce good quality images at frame rates substantially below 25 fps, and in the range of about 10 to about 20 fps, preferably about 13 to about 20 fps. Experienced observers have determined that encapsulated electrophoretic displays running at 15 fps can produce video quality which appears substantially equal to that produced by non-bistable displays running at about 30 fps.
There are many possible reasons for this unexpectedly high video quality at low frame rates, one being that it appears that part of the explanation lies in the manner in which the persistent image on a bistable display assists the eye in “blending” successive images to create the illusion of motion. All video displays rely upon the ability of the eye to blend a series of still images to create the illusion of motion. However, many types of video display actually introduce transient intervening “images” which hinder the blending process. For example, a motion film display using a mechanical film projector actually places a first static image on the screen, then displays a blank screen for a very short period as the projector advances the film to the next frame, and thereafter displays a second static image.
The subject matter presented herein includes driving methods that utilizes interruptible waveform updates while maintaining a substantial DC balance, meaning, the net resulting impulse from the updating is substantially zero, thereby allowing for a smooth pipeline animation updating. In some embodiments, driving methods presented herein further provides strategies to address the ghosting effect. Where as described 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. Remnant voltages may give rise to “edge ghosting,” a type of ghosting in which an outline (edge) of a portion of a previous image remains visible.
Referring now to
In practice, the dithering step 302 of
In some embodiments, with the half-toning process of step 302 producing only black and white images for the displaying pixels, one needs to only consider the following transitions:
In practice, the transitions of white→white and black→black may be left empty as with driving methods that utilizes relatively short pulses to change pixel grayscales (e.g. the Direct Update or DU method mentioned below), which will maintain a DC balance and also reduces transition appearance.
As described above, for some display applications, a display may make use of a “direct update” drive scheme (“DU” drive scheme). The DU drive scheme may have two or more than two gray levels, typically fewer than a gray scale drive scheme (“GSDS), which can effect transitions between all possible gray levels, but the most important characteristic of a DU drive scheme is that transitions are handled by a simple unidirectional drive from the initial gray level to the final gray level, as opposed to the “indirect” transitions often used in a GSDS, where in at least some transitions the pixel is driven from an initial gray level to one extreme optical state, then in the reverse direction to a final gray level; in some cases, the transition may be effected by driving from the initial gray level to one extreme optical state, thence to the opposed extreme optical state, and only then to the final extreme optical state—see, for example, the drive scheme illustrated in FIGS. 11A and 11B of the aforementioned U.S. Pat. No. 7,012,600. Thus, present electrophoretic displays may have an update time in grayscale mode of about two to three times the length of a saturation pulse (where “the length of a saturation pulse” is defined as the time period, at a specific voltage, that suffices to drive a pixel of a display from one extreme optical state to the other), or approximately 700-900 milliseconds, whereas a DUDS has a maximum update time equal to the length of the saturation pulse, or about 200-300 milliseconds.
In some embodiments, the white→black mentioned above can include a pulse driven with positive polarity voltage for pulse length frame, and the black→white transition can include a pulse driven with negative polarity voltage, where the pulse length can be between 15 to 21 frames at a temperature of roughly 25 Celsius.
However, for smooth video transitions, the white→black and black→white transitions will be configured to be interruptible. Preferably, at every update frame since in an animation mode a given pixel may require change of optical states to black or white at every frame.
Rule #1: Apply a single frame negative polarity voltage when a pixel switches from black to white and a single frame positive polarity voltage when a pixel switches from white to black.
Rule #2: continuously apply a single frame voltage for an unchanged state until pulse length is reached in which case subsequent update to the same state will be driven with zero volt.
Rule #3: at the end of an animation sequence, apply the left over impulse potential to reach desired black and white states and completes the DC balancing cycle.
In practice, a waveform of n frames in duration may be used to permute all the possible voltage combinations of −15 volts, 0 volts, and +15 volts required to drive the pixels. Which gives a total of nn, or n3 in this case, of possible voltage combinations. Such list of voltage combination (e.g., n3) is possible to implement with a 5 bit waveform look up table (LUT), which provides 32 waveform slots. In some other embodiments, with a 4-bit waveform LUT, which provides 16 waveform slots, n2 voltage combinations can be achieved.
Referring now to
Furthermore, specialized waveforms may be utilized to clear artifacts such as blooming and/or ghosting at the end, or during a video updating. In some embodiments, this artifact clearing may be performed when the display process comes out of the black and white dither pattern to the original last gray scale image. For example, monopole waveforms may be used to clear artifacts on the white or black states with the use of post drive discharging.
It will be apparent to those skilled in the art that numerous changes and modifications can be made to the specific embodiments of the invention described above without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be interpreted in an illustrative and not in a limitative sense.
This application is related to and claims priority to U.S. Provisional Application 63/086,118 filed on Oct. 1, 2020. The entire disclosures of the aforementioned application is herein incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
4418346 | Batchelder | Nov 1983 | A |
5760761 | Sheridon | Jun 1998 | A |
5777782 | Sheridon | Jul 1998 | A |
5808783 | Crowley | Sep 1998 | A |
5872552 | Gordon, II et al. | Feb 1999 | A |
5930026 | Jacobson et al. | Jul 1999 | A |
6054071 | Mikkelsen, Jr. | Apr 2000 | A |
6055091 | Sheridon et al. | Apr 2000 | A |
6097531 | Sheridon | Aug 2000 | A |
6128124 | Silverman | Oct 2000 | A |
6130774 | Albert et al. | Oct 2000 | A |
6144361 | Gordon, II et al. | Nov 2000 | A |
6172798 | Albert et al. | Jan 2001 | B1 |
6184856 | Gordon, II et al. | Feb 2001 | B1 |
6225971 | Gordon, II et al. | May 2001 | B1 |
6241921 | Jacobson et al. | Jun 2001 | B1 |
6271823 | Gordon, II et al. | Aug 2001 | B1 |
6301038 | Fitzmaurice et al. | Oct 2001 | B1 |
6445489 | Jacobson et al. | Sep 2002 | B1 |
6504524 | Gates et al. | Jan 2003 | B1 |
6512354 | Jacobson et al. | Jan 2003 | B2 |
6531997 | Gates et al. | Mar 2003 | B1 |
6672921 | Liang et al. | Jan 2004 | B1 |
6753999 | Zehner et al. | Jun 2004 | B2 |
6788449 | Liang et al. | Sep 2004 | B2 |
6825970 | Goenaga et al. | Nov 2004 | B2 |
6866760 | Paolini, Jr. et al. | Mar 2005 | B2 |
6870657 | Fitzmaurice et al. | Mar 2005 | B1 |
6900851 | Morrison et al. | May 2005 | B2 |
6922276 | Zhang et al. | Jul 2005 | B2 |
6950220 | Abramson et al. | Sep 2005 | B2 |
6982178 | LeCain et al. | Jan 2006 | B2 |
6995550 | Jacobson et al. | Feb 2006 | B2 |
7002728 | Pullen et al. | Feb 2006 | B2 |
7012600 | Zehner et al. | Mar 2006 | B2 |
7023420 | Comiskey et al. | Apr 2006 | B2 |
7034783 | Gates et al. | Apr 2006 | B2 |
7061166 | Kuniyasu | Jun 2006 | B2 |
7061662 | Chung et al. | Jun 2006 | B2 |
7072095 | Liang et al. | Jul 2006 | B2 |
7075502 | Drzaic et al. | Jul 2006 | B1 |
7116318 | Amundson et al. | Oct 2006 | B2 |
7116466 | Whitesides et al. | Oct 2006 | B2 |
7119772 | Amundson et al. | Oct 2006 | B2 |
7144942 | Zang et al. | Dec 2006 | B2 |
7170670 | Webber | Jan 2007 | B2 |
7177066 | Chung et al. | Feb 2007 | B2 |
7193625 | Danner et al. | Mar 2007 | B2 |
7202847 | Gates | Apr 2007 | B2 |
7236291 | Kaga et al. | Jun 2007 | B2 |
7242514 | Chung et al. | Jul 2007 | B2 |
7259744 | Arango et al. | Aug 2007 | B2 |
7304787 | Whitesides et al. | Dec 2007 | B2 |
7312784 | Baucom et al. | Dec 2007 | B2 |
7312794 | Zehner et al. | Dec 2007 | B2 |
7321459 | Masuda et al. | Jan 2008 | B2 |
7327511 | Whitesides et al. | Feb 2008 | B2 |
7408699 | Wang et al. | Aug 2008 | B2 |
7411719 | Paolini, Jr. et al. | Aug 2008 | B2 |
7420549 | Jacobson et al. | Sep 2008 | B2 |
7453445 | Amundson | Nov 2008 | B2 |
7492339 | Amundson | Feb 2009 | B2 |
7528822 | Amundson et al. | May 2009 | B2 |
7535624 | Amundson et al. | May 2009 | B2 |
7545358 | Gates et al. | Jun 2009 | B2 |
7583251 | Arango et al. | Sep 2009 | B2 |
7602374 | Zehner et al. | Oct 2009 | B2 |
7612760 | Kawai | Nov 2009 | B2 |
7679599 | Kawai | Mar 2010 | B2 |
7679813 | Liang et al. | Mar 2010 | B2 |
7679814 | Paolini, Jr. et al. | Mar 2010 | B2 |
7683606 | Kang et al. | Mar 2010 | B2 |
7688297 | Zehner et al. | Mar 2010 | B2 |
7715088 | Liang et al. | May 2010 | B2 |
7729039 | LeCain et al. | Jun 2010 | B2 |
7733311 | Amundson et al. | Jun 2010 | B2 |
7733335 | Zehner et al. | Jun 2010 | B2 |
7787169 | Abramson et al. | Aug 2010 | B2 |
7839564 | Whitesides et al. | Nov 2010 | B2 |
7859742 | Chiu et al. | Dec 2010 | B1 |
7952557 | Amundson | May 2011 | B2 |
7956841 | Albert et al. | Jun 2011 | B2 |
7982479 | Wang et al. | Jul 2011 | B2 |
7999787 | Amundson et al. | Aug 2011 | B2 |
8009348 | Zehner et al. | Aug 2011 | B2 |
8077141 | Duthaler et al. | Dec 2011 | B2 |
8125501 | Amundson et al. | Feb 2012 | B2 |
8130192 | Feng | Mar 2012 | B2 |
8139050 | Jacobson et al. | Mar 2012 | B2 |
8174490 | Whitesides et al. | May 2012 | B2 |
8179387 | Shin et al. | May 2012 | B2 |
8243013 | Sprague et al. | Aug 2012 | B1 |
8274472 | Wang et al. | Sep 2012 | B1 |
8289250 | Zehner et al. | Oct 2012 | B2 |
8300006 | Zhou et al. | Oct 2012 | B2 |
8305341 | Arango et al. | Nov 2012 | B2 |
8314784 | Ohkami et al. | Nov 2012 | B2 |
8373649 | Low et al. | Feb 2013 | B2 |
8384658 | Albert et al. | Feb 2013 | B2 |
8456414 | Lin et al. | Jun 2013 | B2 |
8462102 | Wong et al. | Jun 2013 | B2 |
8514168 | Chung et al. | Aug 2013 | B2 |
8537105 | Chiu et al. | Sep 2013 | B2 |
8558783 | Wilcox et al. | Oct 2013 | B2 |
8558785 | Zehner et al. | Oct 2013 | B2 |
8558786 | Lin | Oct 2013 | B2 |
8558855 | Sprague et al. | Oct 2013 | B2 |
8576164 | Sprague et al. | Nov 2013 | B2 |
8576259 | Lin et al. | Nov 2013 | B2 |
8593396 | Amundson et al. | Nov 2013 | B2 |
8605032 | Liu et al. | Dec 2013 | B2 |
8643595 | Chung et al. | Feb 2014 | B2 |
8665206 | Lin et al. | Mar 2014 | B2 |
8681191 | Yang et al. | Mar 2014 | B2 |
8730153 | Sprague et al. | May 2014 | B2 |
8810525 | Sprague | Aug 2014 | B2 |
8928562 | Gates et al. | Jan 2015 | B2 |
8928641 | Chiu et al. | Jan 2015 | B2 |
8976444 | Zhang et al. | Mar 2015 | B2 |
9013394 | Lin | Apr 2015 | B2 |
9019197 | Lin | Apr 2015 | B2 |
9019198 | Lin et al. | Apr 2015 | B2 |
9019318 | Sprague et al. | Apr 2015 | B2 |
9082352 | Cheng et al. | Jul 2015 | B2 |
9171508 | Sprague et al. | Oct 2015 | B2 |
9218773 | Sun et al. | Dec 2015 | B2 |
9224338 | Chan et al. | Dec 2015 | B2 |
9224342 | Sprague et al. | Dec 2015 | B2 |
9224344 | Chung et al. | Dec 2015 | B2 |
9230492 | Harrington et al. | Jan 2016 | B2 |
9245485 | Hu | Jan 2016 | B1 |
9251736 | Lin et al. | Feb 2016 | B2 |
9262973 | Wu et al. | Feb 2016 | B2 |
9269311 | Amundson | Feb 2016 | B2 |
9279906 | Kang | Mar 2016 | B2 |
9299294 | Lin et al. | Mar 2016 | B2 |
9373289 | Sprague et al. | Jun 2016 | B2 |
9390066 | Smith et al. | Jul 2016 | B2 |
9390661 | Chiu et al. | Jul 2016 | B2 |
9412314 | Amundson et al. | Aug 2016 | B2 |
9460666 | Sprague et al. | Oct 2016 | B2 |
9495918 | Harrington et al. | Nov 2016 | B2 |
9501981 | Lin et al. | Nov 2016 | B2 |
9513743 | Sjodin et al. | Dec 2016 | B2 |
9514667 | Lin | Dec 2016 | B2 |
9542895 | Gates et al. | Jan 2017 | B2 |
9564088 | Wilcox et al. | Feb 2017 | B2 |
9612502 | Danner et al. | Apr 2017 | B2 |
9620048 | Sim et al. | Apr 2017 | B2 |
9620067 | Harrington et al. | Apr 2017 | B2 |
9672766 | Sjodin | Jun 2017 | B2 |
9691333 | Cheng et al. | Jun 2017 | B2 |
9721495 | Harrington et al. | Aug 2017 | B2 |
9792861 | Chang et al. | Oct 2017 | B2 |
9792862 | Hung et al. | Oct 2017 | B2 |
9966018 | Gates et al. | May 2018 | B2 |
10229641 | Yang et al. | Mar 2019 | B2 |
10319313 | Harris et al. | Jun 2019 | B2 |
10339876 | Lin et al. | Jul 2019 | B2 |
10444553 | Laxton | Oct 2019 | B2 |
10672350 | Amundson et al. | Jun 2020 | B2 |
20030102858 | Jacobson et al. | Jun 2003 | A1 |
20040246562 | Chung et al. | Dec 2004 | A1 |
20050253777 | Zehner et al. | Nov 2005 | A1 |
20070091418 | Danner et al. | Apr 2007 | A1 |
20070103427 | Zhou et al. | May 2007 | A1 |
20070146561 | Zhou et al. | Jun 2007 | A1 |
20070176912 | Beames et al. | Aug 2007 | A1 |
20080024429 | Zehner | Jan 2008 | A1 |
20080024482 | Gates et al. | Jan 2008 | A1 |
20080136774 | Harris et al. | Jun 2008 | A1 |
20080303780 | Sprague et al. | Dec 2008 | A1 |
20090174651 | Jacobson et al. | Jul 2009 | A1 |
20090267970 | Wong | Oct 2009 | A1 |
20090322721 | Zehner et al. | Dec 2009 | A1 |
20100194733 | Lin et al. | Aug 2010 | A1 |
20100194789 | Lin et al. | Aug 2010 | A1 |
20100220121 | Zehner et al. | Sep 2010 | A1 |
20100265561 | Gates et al. | Oct 2010 | A1 |
20110063314 | Chiu et al. | Mar 2011 | A1 |
20110175875 | Lin et al. | Jul 2011 | A1 |
20110193840 | Amundson et al. | Aug 2011 | A1 |
20110193841 | Amundson et al. | Aug 2011 | A1 |
20110199671 | Amundson et al. | Aug 2011 | A1 |
20110221740 | Yang et al. | Sep 2011 | A1 |
20120001957 | Liu et al. | Jan 2012 | A1 |
20120019509 | Wei | Jan 2012 | A1 |
20120098740 | Chiu et al. | Apr 2012 | A1 |
20120242642 | Yamazaki | Sep 2012 | A1 |
20130063333 | Arango et al. | Mar 2013 | A1 |
20130249782 | Wu et al. | Sep 2013 | A1 |
20140009817 | Wilcox et al. | Jan 2014 | A1 |
20140204012 | Wu et al. | Jul 2014 | A1 |
20140240210 | Wu et al. | Aug 2014 | A1 |
20140253425 | Zalesky et al. | Sep 2014 | A1 |
20140293398 | Wang et al. | Oct 2014 | A1 |
20150005720 | Zang | Jan 2015 | A1 |
20150262255 | Khajehnouri et al. | Sep 2015 | A1 |
20150262551 | Zehner et al. | Sep 2015 | A1 |
20160140910 | Amundson | May 2016 | A1 |
20160180777 | Lin et al. | Jun 2016 | A1 |
20180254020 | Buckley | Sep 2018 | A1 |
20190113821 | Paolini, Jr. | Apr 2019 | A1 |
Number | Date | Country |
---|---|---|
2015143883 | Aug 2015 | JP |
Entry |
---|
Lau et al., “Digital halftoning by means of green-noise masks,” Optical Society of America, vol. 16, No. 7, Jul. 1999, pp. 1575-1586. |
O'Regan, B. et al., “A Low Cost, High-efficiency Solar Cell Based on Dye-sensitized colloidal TiO2 Films”, Nature, vol. 353, pp. 737-740 (Oct. 24, 1991). |
Wood, D., “An Electrochromic Renaissance?” Information Display, 18(3), 24 (Mar. 2002) Mar. 1, 2002. |
Bach, Udo et al., “Nanomaterials-Based Electrochromics for Paper-Quality Displays”, Adv. Mater, vol. 14, No. 11, pp. 845-848, (Jun. 5, 2002). |
Hayes, R.A. et al., “Video-Speed Electronic Paper Based on Electrowetting”, Nature, vol. 425, No. 25, pp. 383-385 (Sep. 2003). |
Kitamura, T. et al., “Electrical toner movement for electronic paper-like display”, Asia Display/IDW '01, pp. 1517-1520, Paper HCS1-1 (2001). |
Yamaguchi, Y. et al., “Toner display using insulative particles charged triboelectrically”, Asia Display/IDW '01, pp. 1729-1730, Paper AMD4-4 (2001). |
Korean Intellectual Property Office, “International Search Report and Written Opinion”, PCT/US2021/052812, dated Jan. 21, 2022. |
Number | Date | Country | |
---|---|---|---|
20220108648 A1 | Apr 2022 | US |
Number | Date | Country | |
---|---|---|---|
63086118 | Oct 2020 | US |