CN102789764A

CN102789764A - Methods for driving bistable electro-optic displays

Info

Publication number: CN102789764A
Application number: CN2012101688096A
Authority: CN
Inventors: R·W·泽赫纳; H·G·加特斯; A·C·阿兰戈; K·R·阿穆德森; J·F·欧; A·N·克奈安; J·L·扎勒斯基
Original assignee: E Ink Corp
Current assignee: E Ink Corp
Priority date: 2001-11-20
Filing date: 2002-11-20
Publication date: 2012-11-21
Anticipated expiration: 2022-11-20
Also published as: HK1175287A1; EP1446791B1; CN101676980B; HK1176454A1; JP5905061B2; JP5618811B2; HK1142162A1; JP2007249231A; JP2017049608A; JP2013178580A; CN102789758A; WO2003044765A2; WO2003044765A3; JP4852478B2; EP1446791A2; CN102789764B; CN1589462A; JP2005509925A; AU2002366174A1; JP2011128625A

Abstract

A bistable electro-optic display has a plurality of pixels, each of which is capable of displaying at least three gray levels. The display is driven by a method comprising: storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level; storing data representing at least an initial state of each pixel of the display; receiving an input signal representing a desired final state of at least one pixel of the display; and generating an output signal representing the impulse necessary to convert the initial state of the one pixel to the desired final state thereof, as determined from the look-up table. The invention also provides a method for reducing the remnant voltage of an electro-optic display.

Description

Drive the method for bistable electro-optic displays

The application is to be on November 20th, 2002 applying date, and application number is 200910163444.6, and denomination of invention is divided an application for the application of the method for bistable electro-optic displays " drive ".

The present invention relates to a kind of method of bistable electro-optic displays and device that this method is used of driving.More properly, the present invention relates to a kind of driving method and device controller that is used for more accurately to control the grey states of electro-optic displays pixel.The invention still further relates to a kind of method that makes the driving pulse that is provided to electrophoretic display device (EPD) keep long-term direct current (DC) balance.The present invention especially is used for and uses together based on the electrophoretic display device (EPD) of particle, but is not limited thereto, and in this display, the charged particle of one or more types is suspended in the liquid and under electric field effects, in liquid, moves to change the demonstration of display.

On the one hand, the present invention relates to use the circuit that supplies the driving liquid crystal device to drive the device for the electro-optical medium of the polar sensitive of providing electric field, wherein liquid crystal material is insensitive to polarity.

Employed here as being used for the term " electric light " of material or display; Its conventional implication relates to a kind of material of the first and second different show states on a kind of optical characteristics at least that has in image technique; Through applying electric field to this material, this material changes to its second show state from its first show state.Although this optical characteristics is the color discerned of human eye normally; But it also can be other optical characteristics; Light transmission for example, reflectivity, brightness or be used for the pseudo-colours on the electromagnetic wavelength reflectance varies meaning outside the visible-range under the situation of machine-readable display.

Employed here term " grey states " its conventional implication in image technique relates to a kind of state in the middle of two extreme (extreme) optical states of pixel, and needn't mean the Hei-Bai conversion between two extreme states.For example, it is white and dark blue electrophoretic display device (EPD) that the patent of speaking of below several has been described its extremity with open application, and centre " grey states " in fact is exactly a pale blue like this.In fact, like what pointed out, the conversion between two extreme states can not be a kind of color transformed.

Employed here term " bistable state " and " bistability " their conventional implications in this technology relate to a kind of display; This display comprises the display unit that on a kind of optical characteristics, has the first and second different show states at least; Accomplish arbitrary driving of giving limiting-members with after presenting its first or second show state when the addressing pulse that relies on finite time like this; After addressing pulse finishes; This state can continue several times of times (several times) at least, for example at least four times of times of required addressing pulse shortest time of display unit state for a change.Shown in the common pending application (seeing the open NO.WO02/079869 of corresponding international application simultaneously) of the patent application serial numbers 10/063236 that is to submit on April 2nd, 2002; Some based on the electrophoretic display device (EPD) that gray level is arranged of particle not only at their extreme black and white state; And also be stable at their middle gray state, this is suitable for the electro-optic displays of some other types equally.It is more suitable for being called " multistable " to such display with respect to bistable state, although term " bistable state " can be used to contain bistable state and multistable display here usually.

The term " gamma electric voltage " that here uses is the external voltage reference that finger actuator is used for confirming to provide to displayer pixel voltage.Can be appreciated that bistable state electric light medium is not shown as the type corresponding to one-one relationship between voltage that is provided and the liquid crystal optics status flag; It is equally accurate here the use of term " gamma electric voltage " to be unlike in the conventional LCD, and gamma electric voltage is confirmed the flex point in electric pressure/output voltage curve in conventional LCD.

Employed here term " pulse " is meant the integration of voltage with respect to the time by its conventional implication.But some bistable state electric light media are as charge sensor, and for such medium, can use the definition of an alternative paired pulses, i.e. in time integration of electric current (its equal provided total charge dosage).The suitable definition of paired pulses depends on that medium is as voltage-time pulse sensor or charge pulse sensor.

The bistable electro-optic displays of known several types.One type electro-optic displays is the double-colored metaclass type of rotation, for example at U.S. Patent number 5808783; 5777782; 5760761; 6054071; 6055091; 6097531; 6128124; 6137467; With (although such display often is called as " Rotating Double chromosphere " display, it is more accurate that term " rotates double-colored unit ", because rotation unit is not spherical in more above-mentioned patents) described in 6147791.A kind of like this display uses has two or more corpusculums that a different optical characteristic part (section) and an interior dipole are arranged (being generally spherical or cylindrical) in a large number.These corpusculums are suspended in the vacuole of the full of liquid that is arranged in matrix, because the vacuole full of liquid, so corpusculum can rotate freely.The presentation of this display becomes through applying electric field to it, and then rotates to all places and the part that changes the corpusculum of seeing from a sightingpiston to corpusculum.

The electro-optical medium of another kind of type uses a kind of electrochromic media; For example a kind of electrochromic media, said film with receiving look form membrane comprise at least a portion be the electrode that constitutes by metal oxide semiconductor and a plurality of depend on electrode can reversible color dye molecule; Referring to for example O ' Regan, B. waits people's Nature 1991,353,737; And Wood, D., Information Display, 18 (3), 24 (in March, 2002).Also can be referring to Bach, U. waits people's Adv.Mater., 2002,14 (11), 845.Such receiving look film also has introduction, for example, at U.S. Patent number 6301038, the open NO.WO01/27690 of international application with and the common unsettled series application NO.60/365368 that all submits on March 18th, 2002; 60/365369 and 60/365385; The series application NO.60/319279 that all submits on May 31st, 2002; 60/319280 and 60/319281 and the series application NO.60/319438 that submits on July 31st, 2002.

Conscientiously studied and develop the electrophoretic display device (EPD) that for many years another kind electro-optic displays is based on particle, wherein a plurality of charged particles pass suspending liquid and move under electric field effects.Compare with LCD, electrophoretic display device (EPD) has good brightness and contrast, wide visual angle, the characteristic of bistable state state and low-power consumption.But, the problem of these displays on long-term image quality hindered being widely used of they.For example, the particle of forming electrophoretic display device (EPD) is easy to deposition, causes the serviceable life of these displays not enough.

Under Massachusetts Institute of Technology (MIT) (MIT) and E Ink exabyte or the patent of electrophoretic medium that transfers its a plurality of descriptions encapsulation disclosing in the recent period with application.Such encapsulation medium comprises a plurality of little endosomes (capsule), and each endosome itself comprises that includes the improved interior phase (internal phase) of electrophoresis that is suspended in the liquid suspension medium, and an interior body wall is round interior phase.Usually, endosome is positioned at itself remain in the polymer adhesive in two interelectrode binding layers (coherent layer) to form one.In following file, described such encapsulation medium, for example U.S. Patent number 5930026; 5961804; 6017584; 6067185; 6118426; 6120588; 6120839; 6124851; 6130773; 6130774; 6172798; 6177921; 6232950; 6249721; 6252564; 6262706; 6262833; 6300932; 6312304; 6312971; 6323989; 6327072; 6376828; 6377387; 6392785; 6392786; 6413790; 6422687; 6445374; 6445489 and 6459418; And U.S. Patent Application Publication 2001/0045934; 2002/0019081; 2002/0021270; 2002/0053900; 2002/0060321; 2002/0063661; 2002/0063677; 2002/0090980; 2002/106847; 2002/0113770; 2002/0130832; 2002/0131147 and 2002/0154382 and International Publication No. WO99/53373; WO99/59101; WO99/67678; WO 00/05704; WO00/20922; WO 00/38000; WO00/38001; WO00/36560; WO00/20922; WO00/36666; WO00/67110; WO00/67327; WO01/07961; WO01/08241; WO01/17029 and WO01/17041.

The patent of mentioning in a plurality of preceding text and application are recognized and can be substituted in the electrophoretic medium of encapsulation the wall round discrete microbody (microcapsule) with a kind of external phase; Make a kind of so-called dispersin polymerization body electrophoretic display device (EPD) thus; Electrophoretic medium comprises the discrete droplet of many electrophoresis liquid and the external phase of polymeric material in this display; Even each independent droplet of discrete endosome film discord combines, the discrete droplet of the electrophoresis liquid in such dispersin polymerization volumetric display can be regarded endosome or microbody as; For example referring to WO01/02899, the 10th page of 6-19 is capable.Also can be illustrated in the common unsettled series application NO.09/683903 and the corresponding International Application PCT/US02/06393 that submitted on February 28th, 2002.Therefore, for the application's purpose, such dispersin polymerization body electrophoretic medium is counted as subspecies of the electrophoretic medium of encapsulation.

The electrophoretic display device (EPD) of encapsulation can not suffer the grumeleuse and deposition defective pattern of conventional electrophoretic equipment usually, and further advantage is provided, for example the ability of printing or coating display on various flexibilities and rigid substrates.(use of speech " printing " is to comprise the printing of whole forms and coating, comprises (but do not limit to so): for example obedient sheet mouth mould applies, and slit or extrude coating slides or classification applies, and the metering in advance that curtain applies applies; Roller coat on the cutter for example, forward or the roller coat of reverse roller coat, notch board applies; Immersion coating; Spraying; Meniscus applies; Spin coating; Brush; Air knife applies; Serigraphy is handled; Xeroprinting is handled; The temperature-sensitive printing treatment; Ink jet printing is handled; With other similar techniques.) resulting thus display can be flexible.In addition, because display medium can (make and in all sorts of ways) printing, so display itself can become cheap.

A kind of electrophoretic display device (EPD) of respective type is so-called " microcell electrophoretic display ".In microcell electrophoretic display, charged particle and suspending liquid are not to be encapsulated in the microbody but to remain in a plurality of cavitys in the mounting medium that is formed on polymer film normally.For example, referring to all being the open NO.WO02/01281 of international application that transfers Sipix Imaging company, and disclosed U. S. application NO.2002-0075556.

Based on the formation of the similar characteristics of the bistable state of the electrophoretic display device (EPD) of particle or multistable characteristic and other electro-optic displays performance and traditional liquid crystal (" LC ") display striking contrast.Twisted nematic liquid crystal is not bistable state or multistable but as voltage sensor, so to the pixel of this display the electric field of a setting was provided no matter be present in the gray level on the pixel originally, on pixel, produces the gray level of an appointment.In addition, LCD only drive in a direction (from non-transmission or " deceive " to transmissive or " bright "), from bright state to the reverse transformation of deceiving state through reducing or removing electric field and realize.At last, the gray level of LCD pixel is insensitive to the polarity of electric field, and only to its magnitude, and in fact from technical reason, and the commercial liquid crystal display is often with the polarity of frequent interval upset driving electric field.

By comparison, first approximate part, bistable electro-optic displays is as pulse transducer, so the end-state of pixel not only depends on the time of applied field and applied field, but also depends on the electric field state of pixel before that applies.In addition; Have been found that now; At least in many electro-optic displays based on particle, change the required pulse of a given pixel through the equal change of (as judging through eyes or normalized optical instrument) in gray level and need not to be constant, they also need not to be interchangeable.For example, imagine a kind of display, its each pixel can show for 0 (in vain), and the gray level of 1,2,3 (deceiving) is relatively good at certain intervals.(can in reflection coefficient number percent, be linear at the interval between the gray level,, but also can use other distribution like what survey by eyes or instrument.For example, it is linear that distribution can be in L*, perhaps can select to provide a specific gamma value; 2.2 gamma value through being usually used in monitor, wherein use the alternative of this display as monitor, can use similar gamma value as required.) have been found that and often with 1-2 or 2-3 change required different from the required pulse of 0 grade to 1 grade variation (hereinafter being called " 0-1 conversion " for simplicity) pixel.And it is identical that the required pulse of 1-0 conversion needn't be changed with opposite 0-1.In addition, the performance of some systems shows a kind of " storage " effects, like this (such as) the required pulse of 0-1 conversion depends on whether particular pixels experiences 0-0-1,1-0-1 or 3-0-1 conversion and variation a little.(wherein, symbol " x-y-z " expression is the sequence of the optical states of visit in chronological order, x here, and y, z are

optical states

0,1,2 or 3.Although) can be through required pixel driving is being alleviated all pixel driving of display or overcome these problems to one of extremity with a basic cycle before another state, the pure color that is produced " flicker " often is unacceptable; For example, the reader of e-book possibly need the text of books to roll down to screen, if display needs black or pure white with frequent interval flicker, that reader may be made or lose dizzy his position.In addition, this flicker of display has increased power consumption and can reduce serviceable life of display.At last; Have been found that; At least in some cases, a certain particular conversion required pulse receives temperature and shows total operating time, and particular pixels remained on the influence of the time of a certain particular optical state before given conversion; In order to ensure gray-scale rendition accurately, need compensate these factors.

In one aspect, the present invention seeks to provide a kind of method and controller, can need not on display, to carry out the pure color flicker and to electro-optic displays gray level accurately is provided with frequent interval.

In addition, as from top description, being easy to find out, the driving of bistable state electric light medium requires feasible the modification for the driver that drives AMLCD (AMLCD) design to be inappropriate for the display that is used for based on bistable state electric light medium.But; Such AMLCD driver obtains commercial being easy to, and has big allowable voltage scope and high pin count encapsulation, has the basis that can be purchased off the shelf; Low price; Therefore such AMLCD driver is attractive for driving bistable electro-optic displays, and customization similarly be driver based on bistable state electric light medium display in fact can be more expensive, also to take basic design and manufacturing time.Therefore, revise the AMLCD driver and be used for bistable electro-optic displays and have the advantage on cost and construction cycle, the present invention seeks to provide a kind of method that can satisfy this point and the driver of modification.

Equally,, the present invention relates to the method for drive cataphoresis display, make the driving pulse that is provided to electrophoretic display device (EPD) keep long-term direct current (DC) balance as already mentioned.Have been found that need driving with the waveform of accurate dc balance (promptly of encapsulation with other electrophoretic display device (EPD); To in the whole expanded period of display operation, remain zero for the arbitrary particular pixels electric current of display to the integration of time) to keep image stabilization, keep the switching characteristic of symmetry and the maximum service life (MSL) that display is provided.Be used to keep the accurately power supply supply of control of conventional method needs of accurate dc balance, be used for the precise voltage modulating driver of gray scale and be used for crystal oscillator regularly, top and like the cost that has increased display greatly is provided.

And, even increased such expensive component, still do not realize real dc balance.Find empirically that many electrophoretic mediums have asymmetric current/voltage (I/V curve),, believe that this skew curve is attributed to the electrochemical voltage source in medium although the present invention does not receive any restriction of this understanding.Even this skew curve mean under two kinds of situation voltage carefully is controlled to be accurate unanimity in, inequality when the electric current of (supposing black) was addressed to relative extreme optical state (suppose white) with this medium when medium was addressed to an extreme optical state.

The unbalanced degree of direct current in the electrophoretic medium that in display, uses that has been found that now can be found out through measuring open electrochemical current potential (hereinafter for conveniently being called " residual voltage (the remnant voltage) " of medium).When the residual voltage of pixel was zero, it had been good dc balance just.If it is non-equilibrium that residual voltage for just, is exactly a direct current on the positive dirction.If it is non-equilibrium that residual voltage for negative, is exactly a direct current on negative direction.The present invention uses the residual voltage data to keep the long-term dc balance of display.

Therefore; In one aspect; The present invention provides a kind of method that drives bistable electro-optic displays; Said display has a plurality of pixels, and wherein each can show at least three gray levels (as in conventional display technique, extreme black and white state is regarded as in order to be used to calculate two gray levels of gray level).This method comprises:

Store a question blank, it preserves the data of indicating to change the final gray level required pulse of an initial grey levels to;

Store the data of at least one original state of each pixel of representing display;

Receive the input signal of an expectation end-state of at least one pixel of representing display; With

Produce an output signal, represent the original state of said pixel is transformed into the required pulse of end-state of its expectation, like what from said question blank, confirm.

This method is called " question blank method " of the present invention for simplicity hereinafter.

The present invention also provides a kind of device controller that makes in this way.This controller comprises:

Memory storage is used to store preserve and indicates to change the question blank of the final gray level required pulse data of an initial grey levels to one and the data of at least one original state of each pixel of representing display;

Input media is used to receive the input signal of an expectation end-state of at least one pixel of expression display;

Calculation element is used for confirming that from the data and the question blank of the original state of input signal, the said pixel of expression stored the original state that is used for a said pixel changes the required pulse of end-state that expires and hope; And

Be used to produce the output unit of the output signal of representing said pulse.

The present invention also provides a kind of method that drives bistable electro-optic displays, and said display has a plurality of pixels, and wherein each can show at least three gray levels.This method comprises:

Produce an output signal, expression is transformed into the required pulse of its expectation end-state with the original state of said pixel, and like what from said question blank, confirm, the output signal indication will offer the time cycle of the substantially invariable driving voltage of said pixel.

Calculation element is used for confirming to be used for original state with a said pixel from the data of the original state of input signal, the said pixel of expression stored and question blank and changes to expire and hope the required pulse of end-state; And

Be used to produce the output unit of the output signal of representing said pulse, the output signal indication will offer the time cycle of the substantially invariable driving voltage of said pixel.

In yet another aspect, the present invention provides a kind of device controller that uses the inventive method.This controller comprises:

Memory storage is used to store preserve and indicates to change the question blank of the final gray level required pulse data of an initial grey levels to one and the question blank of at least one initial condition data of each pixel of expression display;

Be used to produce the output unit of the output signal of the said pulse of expression, a plurality of pulses that in one of voltage and duration at least, change of output signal indication, exporting signal indication at a predetermined period of time at the expiration is no-voltage.

In yet another aspect, the present invention provides a kind of drive circuit with output line of the drive electrode that is used to be connected to electro-optic displays.This drive circuit comprises first input media, is used to receive a plurality of signal voltage and (n+1) bit digital of polarity of indicating to be placed on the drive electrode; And second input media that is used for the receive clock signal.One receives clock signal, and drive circuit just is presented at selected voltage on its output line.In a preferred form of this drive circuit, selected voltage can be between R and R+V 2 ⁿIn the individual discrete voltage any or between R and R-V 2 ⁿIn the individual discrete voltage any, wherein R is predetermined reference voltage (voltage of electrode before Active Matrix Display public normally, as be described in more detail below), V is that this drive circuit is confirmed (assert) and maximum differential pressure reference voltage.These selected voltages can be that linear distribution is in R ± V scope; Also can be that nonlinear way distributes; This non-linear can control by two or more gamma electric voltages that are positioned at particular range, each gamma electric voltage define one in gamma electric voltage and adjacent gamma value or the linear conditions between the reference voltage (regime).

In yet another aspect, the present invention provides a kind of drive circuit with output line of the drive electrode that is used to be connected to electro-optic displays.This drive circuit comprises first input media, is used to receive a plurality of signal voltage and 2 bit digital of indicating to be placed on the drive electrode (2-bit number) of polarity; And second input media that is used for the receive clock signal.One receives clock signal, and drive circuit is just from R+V, and selected voltage is presented on its output line among R and the R-V (wherein R and V as above define).

In yet another aspect, the present invention provides a kind of method of driving bistable electro-optic displays method, particularly drive cataphoresis display, and said display shows a residual voltage.This method comprises:

(a) pixel to display provides first driving pulse;

(b) after first driving pulse, measure the residual voltage of pixel; And

(c) after the measurement of residual voltage, second driving pulse is provided, relies on size that measured residual voltage controls second driving pulse to reduce the residual voltage of pixel to pixel.

This method can be called " residual voltage " of the present invention method hereinafter for convenience's sake.

Fig. 1 is expression apparatus of the present invention, by the display of this device driving and the synoptic diagram of associated apparatus, is designed to show the structure of total system;

Fig. 2 is the schematic block diagram of the controller unit shown in Fig. 1, and the output signal that is produced by this unit has been described;

Fig. 3 is the schematic block diagram that the controller unit shown in expression Fig. 1 and 2 produces the mode of a certain output signal shown in Fig. 2;

Figure 4 and 5 represent to be used for two kinds of different reference voltage settings of display shown in Figure 1;

Fig. 6 is illustrated in the synoptic diagram of between width modulation and voltage modulated method, weighing in the look-up-table method of the present invention;

Fig. 7 is the block diagram of customization (custom) driver that is used for look-up-table method of the present invention;

Fig. 8 is that explanation can be by the process flow diagram of the program of controller unit shown in Fig. 1 and 2 operation;

Fig. 9 and 10 has showed two kinds of drive arrangements of the present invention;

Figure 11 A and 11B have showed two parts of the third drive arrangements of the present invention.

Pointed out that as top question blank of the present invention partly provides method and the controller that is used to drive electro-optic displays, said display has a plurality of pixels, and wherein each can show at least three gray levels.The present invention certainly is used to have the electro-optic displays of greater number gray level, and for example 4,8,16 or more.

Equally as stated, drive bistable electro-optic displays need be generally used for the method that driving liquid crystal device (LCD) is entirely different.In conventional (non-cholesteric) LCD, apply the specific voltage in enough cycle to pixel, can make pixel obtain a particular gray level.And, liquid crystal material a magnitude to electric field, and insensitive to its polarity.By comparison, bistable electro-optic displays is as pulse transducer, so do not applying voltage and obtaining man-to-man mapping between grey states; Must be applied to pulse (with voltage thus) that pixel is used to obtain a given grey states changes with " initially " grey states of corresponding pixel.In addition, owing to need (arriving in vain to black and black) on both direction in vain, bistable electro-optic displays drives, so need to specify the polarity and the size of required pulse.

Here, need to consider to define some terms in this use according to its conventional sense in display technique.Following most of discussion concentrates on one or more pixels of the single gradation conversion (that is, from a kind of gray scale to alternative variation) of experience from " initially " state to " finally " state.Obviously, original state and end-state are appointed as and are only considered the single conversion of being studied, and in most of the cases, pixel has lived through conversion before " initially " state, and behind " finally " state, also will pass through conversion.Like following explanation, some embodiments of the present invention not only will consider the initial sum end-state of pixel, also will consider pixel existing before reaching original state " preceding " state.Here need between preceding state, distinguish a plurality of; Term " first at preceding state " is used in reference to the state that there is (non-zero) conversion before original state in corresponding pixel; Term " second at preceding state " is used in reference to corresponding pixel and has one at first state in (non-zero) conversion before of preceding state, and the like.Term " non-zero conversion " is used in reference to " conversion " that realizes at least one gray scale unit change; Term " zero conversion " is used in reference to " conversion " (although other pixel of display can experience the non-zero conversion simultaneously) of any variation that does not produce selected pixel gray scale.

Be easy to find out like those skilled in the art, a simple embodiment of method of the present invention can only consider the original state and the end-state of each pixel, and in this case, question blank is two-dimentional.But like what pointed out, some electro-optical mediums show storage effect; And such medium needs; When producing the output signal, need not only consider the original state of each pixel for this medium, but also will (at least) consider this pixel first at preceding state; In this case, question blank is three-dimensional.In some cases, possibly need consider each pixel more than one at preceding state, cause in question blank, there are four thus (if only considering first and second) or various dimensions more at preceding state.

See from the form mathematical terms; The present invention can regard as and comprise an algorithm; Provide the initial sum of relevant electric light pixel final and (optional) in the information of preceding state; And the information of the physical state of (optional-as to discuss in more detail in vide infra) relevant display, one can be produced and the function V (t) that pixel is changed with the end-state that is implemented to expectation can be used for.From this form viewpoint, controller of the present invention can be regarded a physical embodiments of this algorithm in fact as, and controller is used as at the equipment of desired display information and the interface between the electro-optic displays.

Temporarily ignoring physical state information, according to the present invention, is this algorithm coding question blank or transition matrix.This matrix has the one dimension of each end-state that is used to expect, and in calculating, be used for other state each dimension of (initial sum is any at preceding state).The key element of matrix can comprise to be used for electro-optical medium function V (t).

The key element of question blank or transition matrix can have various ways.In some cases, each key element can comprise single number.For example, electro-optic displays can use can export multiple high-accuracy voltage modulating driver circuit at a reference voltage different voltages up and down, and to pixel required voltage is provided with the predetermined period of a standard simply.In this case, each clauses and subclauses in question blank can simply have the form of individual integer, and this integer is specified will provide to given pixel for which voltage.Under another kind of situation, each key element can comprise a series of numbers of the diverse location that relates to waveform.For example, the embodiments of the invention that are described below use single or two prepulsing waveforms, and specify such required pulse to it may be noted that several numbers of the diverse location of waveform.What talk about equally below is embodiments of the invention, and it is selected in a complete scan in the several process in a plurality of sub-scan periods, effective apply pulse length modulated through a predetermined voltage is provided to pixel.In such embodiment, the key element of transition matrix can have several the forms that indicate whether in each sub-scan period of corresponding conversion, to apply predetermined voltage.At last, as described in more detail below, in some cases, for example the temperature compensation display can be the form (perhaps, in fact more definite is various coefficient in such function) of function for the key element of question blank more easily.

Obviously employed in some embodiments of the invention question blank can become very big.Take an extreme example, imagination considers that with a kind of initial, two algorithms at preceding state of final sum are used for 256 (2 ⁸) operation of the present invention of gray level display.Required four-dimensional question blank has 2 ³²Individual clauses and subclauses.If each clauses and subclauses needs (hypothesis) 64 (8 byte), the total amount of question blank can be about 32G byte so.Although what problem is the so big quantity data of storage do not have on desktop computer, in portable equipment, just possibly have problems.But the size of in fact so big question blank can reduce greatly.Under many circumstances, have been found that and have only the different switching that seldom type of waveform of number need be a large amount of that for example the length of the independent pulse of common waveform changes between different switching.Therefore, can reduce in question blank the length of clauses and subclauses separately through each clauses and subclauses comprised with the lower part: (a) sensing be used to specify one of the peanut type of waveform that will use at the second table discal patch purpose pointer; And (b) parameter of specifying the peanut how common waveform change for relevant conversion.

Can confirm in advance in question blank discal patch purpose value through optimum processing of an experience.Basically; Pixel is set to corresponding original state; Provide the estimation of a certificate to need the roughly the same pulse of expectation end-state that obtains, and the end-state of measurement pixel is to confirm the deviation between reality and the expectation end-state, if this deviation exists.Then should the processing meeting repeat up to deviation less than predetermined value with modulating pulse, this can be confirmed by the function of the instrument that is used to measure end-state.Considering in the situation in this method of preceding state of or more pixels; Except original state; When pixel state be used for confirming pulse original state and whole at preceding state in constant; General at first confirm the required pulse of particular conversion, consider that then different at preceding state " accurate adjustment " to be carried out in this pulse be easily.

Paired pulses modulation and because " wear out " of some electro-optical mediums and the variation of their states maybe needs after long period of operation compensation when the present invention expectation is provided at the variation of the total operating time of considering temperature and/or display to the running time.Such modulation can one or both methods realize.At first, can come the expanding query table by the additional dimension of the every kind of variable that is used for when calculating the output signal, being considered.Obviously, when handling the continuous variable of for example temperature and operation,, need quantize continuous variable in order question blank to be remained in the specific finite size.In order to find out the waveform that will be applied to pixel, calculation element can select the question blank clauses and subclauses as near the form of measured temperature simply.Alternatively, for temperature compensation more accurately is provided, calculation element can be sought in the continuous variable both sides that record two in abutting connection with the question blank clauses and subclauses, and uses a suitable interpolation algorithm and obtain the required clauses and subclauses at the variable intermediate value place that records.For example, hypothesis matrix comprises the temperature clauses and subclauses that increase progressively with 10 ℃.If actual display temperature is 25 ℃, calculating can be sought the clauses and subclauses of 20 ℃ and 30 ℃ and use this intermediate value of two so.Notice owing to the characteristic variations with temperature electro-optical medium together often is not linear, so the clauses and subclauses for the temperature setting of question blank storage can be by linear distribution; Therefore for example, many electro-optical medium variation of temperature mostly accelerate at the high temperature place, and it is just enough to be in the question blank 20 ℃ spacing at low temperature, and 5 ℃ spacing can meet the demands at the high temperature place.

But a kind of system of selection that is used for the compensation of temperature/running time is to use with the functional form of physical descriptor or perhaps in the question blank clauses and subclauses of the more severity factor of such function normal term.Consider the situation modulate the display of drive scheme service time for simple; Wherein control each conversion through the constant voltage (arbitrary polarity) that a variable time span is provided to each pixel; Therefore; Save the correction of any environmental variance, each clauses and subclauses in question blank can only comprise the duration of the constant voltage of indicating to apply and the single signed number of its polarity.Be the such demonstration of temperature variation correction if desired, the time T of the constant voltage that on temperature t, need apply so for particular conversion _tProvide by following formula:

T _t＝T ₀+AΔt+B(Δt) ²

T wherein ₀Be the time that needs in several criteria temperature place, normally display is estimated the mid point of operating temperature range, and Δ t is at t with at T ₀Poor between the measured temperature, the clauses and subclauses in question blank can comprise T ₀And the A and the value of B that are used to relate to the particular conversion of given clauses and subclauses, and calculation element can use these coefficients to calculate the T at the measured temperature place _tIt is pushed into more at large, and calculation element is found out the question blank clauses and subclauses that are suitable for corresponding initial sum end-state, uses the function by this clauses and subclauses definition to calculate the suitable output signal of having considered other variable that need consider then.

The associated temperature that is used for temperature compensation calculating is the temperature of the electro-optical medium on corresponding pixel; And this temperature can be obviously different with environment temperature; Particularly will be used under the situation of outdoor application at display, for example sunlight causes the temperature of electro-optical medium layer in fact will be higher than environment temperature through the front fender effect there.In fact, in the situation of the huge outdoor sign of bulletin template, for example, if the part of display falls under the shade of adjacent building, then in sunlight, the temperature on the so same display between different pixels can be different to other part.Therefore, maybe be in electrooptic layer or contiguous its embed one or more electric heating occasionally other temperature sensor to survey the actual temperature of this layer.In the situation of big display, possibly also need be defined in method of interpolation between the temperature that records through many temperature sensors to estimate the temperature of each particular pixels.At last, in the situation of the big display that is made up of the many modules that can replace separately, method of the present invention and controller can be the regulation different operation time of the pixel in the disparate modules.

Method of the present invention and controller it is also conceivable that the residence time (being the cycle that pixel is kept non-zero conversion) of the particular pixels that will drive.Have been found that at least in some cases, for the required pulse of given conversion along with the residence time of pixel in its optical states changes.Like this, with regard to expectation or must change as pixel the pulse that is used for given conversion at the function of the residence time of its initial optical state.In order to accomplish it, question blank can comprise an additional dimension that is used in reference to the residence time of aspect element in its initial optical state by a counter index.In addition, controller need contain an additional storage of the counter that is useful on each pixel in the display.This also needs a read clock, and it is increased to be provided with at interval by the count value that is stored in each pixel.Length at interval must be the integral multiple of display frame-period, therefore must be not less than a frame period.The size of counter and clock frequency can be decided with necessary temporal resolution by the pulse elapsed time length of used variation.For example, for one 4 digit counter of each pixel storage can allow pulse in 4 second cycle (4 seconds * 4 times counting/second=16 time count=4) with 0.25 second interval variation.In case this counter of particular event takes place can zero clearing, for example pixel has been transformed into a kind of new state.In case reach its maximal value, can counter be set to " upset " to zero count, the maximal value that perhaps keeps it up to it by zero clearing.

Certainly consider that according to the pulse of any or more particular conversion that need the generation electro-optical medium any physical parameter that other has detectable effect changes question blank method of the present invention.For example, if find that electro-optical medium to humidity sensitive, can change the correction of this method with combining environmental humidity.

For bistable state electric light medium, question blank can have following characteristic, and for zero identical conversion of the initial sum end-state of any pixel, clauses and subclauses are zero, perhaps in other words, do not have voltage and are applied on the pixel.As an inevitable outcome,, just needn't apply pulse if in given interval, there is not pixel to change on the display.This can realize the super low-power consumption operation, has guaranteed that also electro-optical medium can excessively not drive when showing still image.Generally, question blank only can keep the information about the non-zero conversion.In other words, for two images, I and I+1, if given pixel is in identical state in I and I+1, state I+1 just can not be stored in preceding state table so, and after the conversion of pixel experience canned data.

Like the professional for the modern electronic technology field is conspicuous, and controller of the present invention can have various physical form.And can use any routine data processing element.For example, can use universal digital computer to realize this method, this computing machine be used for output converts suitable pixel into and combines with the suitable equipment of voltage (for example, one or multiple digital analog converter more, " DAC ") from the numeral of computing machine.Optional, method of the present invention can realize through using special IC (ASIC).Special, controller of the present invention can have the form of video card, and it can be inserted into and make the image that is produced by computer be presented in the PC to replace on the existing display screen or the electric light screen that replenishes as existing display screen of LCD for example.Because the structure of controller of the present invention is just on the technical merit in image processing techniques, so needn't describe its circuit details in detail at this.

The preferred physical embodiments of controller of the present invention is a kind of timing controller integrated circuit (IC).This IC receives input image data and output is used for data aggregation and the control signal of selecting drive IC, produces desired images on pixel, to produce suitable voltage.This IC can receive view data through the memory buffer unit of visit preservation view data, perhaps can receive the signal that is used to drive traditional LC D panel, therefrom extracts view data.It can also receive the serial signal of preserving its necessary pulse computing information that need carry out arbitrarily.On the other hand, this timing controller available software realizes, or is combined into the part of CPU.This timing controller can also have the for example any ability that influences the external parameter of display operation of temperature of measuring.

Controller can be operated as follows.The question blank that memory controller can obtain in storer.For each pixel successively, initial, the final sum (optional) that are necessary all provide as input in preceding and physical state information.These status informations are used for calculating the index of question blank then.In the situation of the temperature that quantizes or other correction, can be a voltage from the rreturn value of this inquiry, or the array of voltages of a relative time.Controller can repeat this operation for two bracketing temperature in question blank, between these values, carries out interpolation then.For the correction of algorithm temperature, the rreturn value of question blank has one or more parameter, then as stated, and can be with equality of the synthermal substitution together of these parameters to confirm the appropriate format of driving pulse.This program can need the system variable of driving pulse real-time change to realize in a similar fashion for other is any.One or more such system variables can be confirmed by the memory that for example in structure, is arranged on the value of the programmable resistance on the display panel for the performance of optimizing display or be stored among the EPROM.

An important feature of this display controller is that it does not resemble most of displays, in most of actual conditions, needs several complete reading scans in order to accomplish an image update.Be that the required several scannings of image update should be formed one and can not be interrupted the unit.If display controller and figure image source synchronous operation, must to guarantee to be used for calculating the data of the pulse that provides constant in whole scanning maintenance for this controller so.This can realize with one or both methods.At first, input image data can be stored in (alternatively, if display controller is visited display buffer through dual-ported memory, it should block the visit from CPU) in the independent impact damper by display controller.Secondly, in scanning for the first time, controller can be stored in the pulse of calculating in the pulse buffer.The benefit of this second option is that the house-keeping (overhead) that each conversion is used for scanning panel is only carried out once, and the data that are used to keep scanning can directly be exported from impact damper.

Optional, image update can be handled with a kind of synchronous mode.In general, although the general complete conversion that produces once between two images can spend scanning several times, independent pixel can begin the conversion changing or overturn and begun in the centre of frame.In order to realize this, controller must be remembered that for which part of the whole conversion of given pixel have been accomplished.Change the not request of the optical states of the pixel in current conversion if receive, the counter of this pixel can be by zero clearing so, and this pixel can begin conversion in next frame.If pixel is effectively in the conversion when receiving a new request, then controller can provide an algorithm to confirm how from the current new state of frame intermediateness arrival.For 1 normal image stream, a kind of possible algorithm is the pulse that a upset polarity is provided simply, and it is through amplifying and having with already provided in the identical duration of prepulse part.

In order to make the required minimum power of operation display; And the picture steadiness of electro-optical medium is maximized; When in display, not having pixel to change, this display controller can stop the scanning of display and reduce to be applied to the voltage of all pixels or make it near zero.Very advantageously be that this display controller can be closed to the power supply of its corresponding line and row driver when display is in " maintenance " state, can make minimise power consumption like this.In this scheme, this driver can be activated again when asking pixel conversion next time.

Accompanying drawing 1 schematically shows the device of the present invention that uses together with associated apparatus.Whole devices shown in Fig. 1 (be often referred to and be shown 10) comprise a figure image source, the PC 12 of on data line 14, exporting the presentation video data shown in.Data line 14 can be any general type and can be an independent data line or bus; For example, data line 14 can comprise USB (USB), and serial is parallel, I EEE-1394 or other line.The data of placing on online 14 can be conventional bit map as form, for example bitmap (BMP), TIF (TIF), GIF (GIF) or associating (Jooint) motion picture expert group version (JPEG) file.Yet optional, the data of placing on online 14 can be the signal forms that is used to drive video equipment; For example, many computers provide a kind of video output that is used to drive external display, and the signal in this output can be used for the present invention.Can recognize that the technician of image processing field the present invention's device described below carries out basic document format conversion and/or decoding possibly; To use dissimilar available input signals; But such conversion and/or decoding are known to those skilled in the art; Therefore, only can describe device of the present invention: be transformed into as the view data of its original input and be the manageable form of device of the present invention from this point.

As described in detail later, data line 14 extends to controller unit 16 of the present invention.This controller unit 16 is producing one group of output signal and is producing second group of signal on the data bus 20 separately on the data bus 18.Data bus 18 is connected to two row (perhaps grid) driver 22, and data bus 20 is connected to a plurality of row (perhaps source) driver 24 (number at the row driver shown in Fig. 1 greatly reduces for the ease of expression).The operation of row and column driver control bistable electro-optic displays 26.

Be selected to represent various available cell at the device shown in Fig. 1, it is suitable for a kind of experimental " breadboard " unit most.In the commerce of reality was made, as in the conventional portable computer and personal digital assistant of assembling LCD, controller 16 can become the part of the same physical location of display 26 usually, and the figure image source also can become the part of this physical location.Same; The present invention is illustrated among Fig. 1 and a kind of Active Matrix Display structure of main below combination is described; This display device structure has the independent common transparent electrode on a side of electrooptic layer, and this public electrode extends through whole pixels of display.Usually, this public electrode is between electrooptic layer and observer and form an observer and watch the sightingpiston of display through it.Be sidelong the pixel capacitors matrix of putting with the row and column layout at opposite one of electrooptic layer, like this by unique definite each pixel capacitors of independent row and the infall that is listed as separately.Thus, through the voltage that is provided to corresponding pixel electrode of change with respect to the voltage (generally being expressed as " Vcom ") that is provided to public preceding electrode, control is by the electric field that each pixel stood of electrooptic layer.Each pixel capacitors is connected with a transistor at least, normally thin film transistor (TFT).Be connected on one of line driver 22 through independent prolongation column electrode at transistorized grid on every row.Be connected on one of row driver 24 through independent prolongation row electrode whenever listing transistorized source electrode.Each transistorized drain electrode is directly connected on the pixel capacitors.Be appreciated that grid is at random to row and source electrode to the distribution that is listed as, such just as the distribution of source electrode and drain electrode, can reverse.But below describing can the conventional distribution of hypothesis.

In operation, line driver 22 applies voltage to grid, has one and to have only the transistor of delegation be conducting in arbitrary preset time like this.Simultaneously, row driver 24 provides predetermined voltage to arrive each row electrode.Thus, the voltage that is applied to row driver only is provided in the delegation of pixel capacitors, on electro-optical medium, writes (or part writes at least) delegation's desired images like this.Line driver switches the transistor turns that makes in next line then, and a different set of voltage is applied to the row electrode, writes the next line image.

It is emphasized that and the invention is not restricted to such Active Matrix Display.As long as determine the precision waveform that is used for each pixel of image, can use any handover scheme to come waveform to be provided to pixel according to the present invention.For example, the present invention can use the scheme of a kind of so-called " directly driving ", and wherein independent drive wire offers each pixel.On principle; The present invention can also use a kind of passive-matrix drive scheme that is used for some LCD; But it should be noted that because many bistable state electric light media lack switching threshold (that is, as long as a very little electric field that prolongs the cycle is provided; This medium will change optical states), so being inappropriate for passive-matrix, such medium drives.But owing to it seems that the present invention finds that it is mainly used in the Active Matrix Display, the present invention mainly is to describe with reference to such display at this.

Controller unit 16 (Fig. 1) has two major functions.The first, use method of the present invention, controller calculates and will change to the two-dimensional matrix that final image must be applied to the pulse (or waveform) on the displayer pixel from initial pictures.The second, the conventional driver that is used for the LCD design drives bistable electro-optic displays, and controller 16 calculates from this dither matrix and will apply the required whole timing signals of expectation pulse in pixel capacitors.

As shown in Figure 2, have two major parts at the controller unit shown in Fig. 1 16, promptly a buffer memory representes that controller 16B will be written to the frame buffer 16A of the final image data of display 26 (Fig. 1), and controller itself, is designated as 16B.Controller 16B pixel reads data one by one and produce the various signals be described below at

data bus

18 and 20 from impact damper 16A.

Signal shown in Fig. 2 is following:

Six magnitudes of voltage of D0:D5-pixel (obviously, the figure place in this signal can change according to used particular row and row driver)

POL-is with respect to the pixel polarity of Vcom (vide infra)

START-places a start bit to start the loading of pixel value in row driver 24

The horizontal-drive signal of HSYNC-breech lock row driver

PCLK-follows the pixel clock that driver switches the start bit

VSYNC-is loaded into the start bit vertical synchronizing signal of line driver

The output enabling signal of OE-breech lock line driver.

In these signals; Although the definite timing of these signals can change according to employed accurate electro-optical medium certainly; Because line scanning method is identical with the LCD scan method on principle in device shown in Fig. 1, so it is the same with the corresponding signal that in conventional thin film transistor, is provided to line driver basically with OE to be provided to the VSYNC of line driver 22.Similarly, for START, HSYNC and PCLK, although their timing meeting changes according to employed accurate electro-optical medium, these signals that are provided to row driver are the same with the corresponding signal that in conventional thin film transistor, is provided to row driver basically.Therefore, can think that there is no need to further describe these exports signal.

Fig. 3 is illustrated in the method that the controller 16B shown in Fig. 2 produces D0:D5 and POL signal with highly schematic mode.As stated; Controller 16B storage representation final image 120 (this image be expectation write display) writes initial pictures 122 and selectable one or more data at preceding image 123 that before initial pictures, write display of display in advance.Embodiments of the invention shown in Figure 3 stored two such at preceding image 123.(obviously, the storage of necessary data can be at controller 16B or in an external data storage device.Controller 16B uses particular pixels (as shown in Fig. 3 shade; Be expressed as first first pixel of row) initial, final and at preceding image 120; 122 and 123 data are as the pointer that gets into question blank 124, this question blank provide the state that will change this pixel to the expectation gray level in final image must be applied to the value of the pulse of particular pixels.To and be provided to one from the synthetic output of question blank 124 and produce D0:D5 and POL voltage of signals v. frame array 128 from the output of frame counter 126.

Controller 16B is designed to use together with the TFT lcd driver, and this driver is equipped with the pixel reverse circuit that changes adjacent image point polarity usually with respect to end face.Pixel at interval can be designed as by even number and odd number and is connected in the two opposite sides of voltage ladder.In addition, the driver input that is labeled as " polarity " is used to switch the polarity of even number and odd number pixel.Driver provides together with four or more gamma electric voltage grades, to the slope local that can confirm voltage-class curve that is provided with of above-mentioned electric pressure.Exemplary with commercial integrated circuit (IC) of these characteristics is the KS0652 300/309 passage TFT-LCD Source drive of Samsung.As stated, the display that drive uses the public electrode on electro-optical medium one side, and the Voltage Reference that is applied to this public electrode is like " end face voltage " or " Vcom ".

In an embodiment shown in accompanying drawing 4, the reference voltage of driver is arranged as end face voltage and is positioned on maximum voltage (Vmax) that driver can provide half the, promptly

Vcom＝Vmax/2

And gamma electric voltage is arranged as linear change about end face voltage.(gamma electric voltage of an odd number of Figure 4 and 5 hypothesis is drawn, thus for example in Fig. 4 gamma electric voltage VGMA (n/2+1/2) equal Vcom.If there is the gamma electric voltage of an even number, VGMA (n/2) and VGMA (n/2+1) are provided with and equal Vcom.Similarly, in Fig. 5, if there is the gamma electric voltage of an even number, VGMA (n/2) and VGMA (n/2+1) are provided with and equal ground voltage Vs s).The required pulse length of the whole conversions of acquisition is set up the required maximum impulse of new images by distribution through Vmax/2 and is decided.This pulse can be converted into frame number through multiply by the reading scan rate.Necessary then frame number multiply by 2 even number and odd-numbered frame to provide a great deal of.These even numbers and odd-numbered frame can be to be set to height or low with respect to this frame corresponding to polarity bit.For each pixel in every frame, controller 16B must provide a kind of algorithm, is even number or odd number with (1) pixel; (2) for the frame of being considered, polarity bit is a height or low; (3) desired pulse is just or negative; And the size of (4) expectation pulse is imported as it.Algorithm confirms that again can this pixel be addressed with the polarity of expectation in this frame then.If just suitable driving voltage (pulse length) is provided to this pixel.If not, then this pixel is parked in end face voltage (Vmax/2) to be located at hold mode, wherein in this frame, there is not electric field to be applied to pixel.

For example, consider two adjacent image points in the display, the plain 1 and icon plain 2 of odd image.And, suppose that the odd image element can be visited positive drive voltage range (promptly on end face voltage) when polarity bit when being high, the icon element can be visited negative voltage (promptly below end face voltage).If

pixel

1 and 2 all need drive with positive pulse, must there be following order so:

(a) in the positive polarity frame, with positive voltage driving pixel 1, pixel 2 remains on the end face voltage; With

(b) in the negative polarity frame, pixel 1 remains on end face voltage, and with positive voltage driving pixel 2.

Although general frame can alternately (that is, replace) with 1: 1 positive-negative polarity each other, this is optional; For example, all odd-numbered frame can flock together, and and then are all even frame.This can cause the alternate column of meeting driving display in the group of two separation.

The major advantage of present embodiment is needn't switch during operation public preceding electrode.This major advantage is that the maximum drive voltage of available electro-optical medium is the half the of driver maximum voltage, and each row can only drive for 50% time.Like this, under identical maximum drive voltage, the refresh time of this display is four times of electro-optical medium switching time.

In second embodiment of this form of the present invention, the gamma electric voltage of driver layout as shown in Figure 5, public electrode switches between V=0 and V=Vmax.The gamma electric voltage of in this way arranging allows plain with single direction driving icon element and odd image simultaneously, but need public electrode be switched near opposite driving polarity.In addition, because this layout is about the end face voltage symmetry, therefore the specific input to driver can cause identical voltage to be provided on odd image element or the icon element.In this case, the input of algorithm is the size and the symbol of desired pulse, and the polarity of end face.If the symbol corresponding to the expectation pulse is provided with current public electrode, should value be exactly output then.If the expectation pulse is in opposite direction, so this pixel is arranged on end face voltage, in this frame, there is not electric field to be applied on this pixel like this.

Of last embodiment, in the present embodiment can be through calculating the necessary length of driving pulse divided by maximum impulse with maximum drive voltage, and this value is converted into frame number through multiply by display refresh rates.The fact that frame number must be double again can only drive corresponding to end face with the explanation display at every turn in one direction.

The major advantage of second embodiment is to use the full voltage of driver, and can drive all output at once.But two frames need to drive in the opposite direction.Thus, under identical maximum drive voltage, the refresh time of this display is the twice of the switching time of electro-optical medium.Its major defect is to need to switch public electrode, and this possibly cause at electro-optical medium, transistor that links to each other with pixel capacitors or the voltage noise of not expecting among both.

In arbitrary embodiment, gamma electric voltage generally all is distributed between the maximum voltage and end face voltage of driver with linear gradient.Depend on the design of driver, can in output, really produce top voltage, possibly need one or more gamma electric voltages on the end face value in order to ensure driver.

Method of the present invention is suitable for be used for the restriction of the conventional driver of LCD design to make reference in the preceding text to needs.More specifically; The row driver of conventional LCD; Particularly supertwist is to row (STN) LCD (can control higher voltage than the row driver of other type); In arbitrary preset time, can only apply one of two voltages, because Here it is to whole needs of the non-sensitive liquid crystal material of polarity to drive wire.Opposite, for driving the electro-optic displays to polar sensitive, three actuator electrical voltage levels of minimum needs.These three required actuator voltages are with the V-of relative end face voltage for negative driving pixel, are the V+ of positive driving pixel with relative end face voltage, and the voltage that to keep pixel be 0V at the relative end face voltage of identical show state.

But; Method of the present invention can realize with such conventional lcd driver; For necessary pulse will be provided to the pixel of electro-optic displays, the controller of arranging to be provided is to one or more multiple row driver and relative line driver provide a suitable voltage sequence.

This method has two primary variabless.In first variable, the pulse that is provided to some extent must have+I, one of-I or 0 three values, wherein:

+I＝-(-I)＝Vapp×t _pulse

Wherein Vapp is the voltage on end face voltage that is provided, and t _PulseBe to be the pulse length of unit with the second.This variable only allows display to operate with scale-of-two (black/white) pattern.In second variable, the pulse that is provided can change to-I from+I, but must be the integral multiple of Vapp/freq, and wherein freq is the refreshing frequency of display.

The following fact that this aspect utilization of the present invention has been pointed out, conventional lcd driver are designed to avoid some not expect but the effect that may in display, produce with frequency interval upset polarity.Therefore, such design of Driver becomes to receive the polarity or the control voltage of self-controller, and it can or be low for height.When showing when being a low control voltage; The output voltage on arbitrary given driver output line can adopt maybe be required three voltages outside one of two; For example V1 or V2; And when showing when being a high control voltage, the output voltage on arbitrary given driver output line can adopt one of different in three voltages that possibly need two, for example V2 or V3.Thus, only two outside three required voltages can be addressed at arbitrary special time, and three whole voltages just can obtain in different time.These three required voltages can satisfy following relational expression usually:

V2＝(V?3+V1)/2

V1 can or near logically.

In this method of the present invention, display can be by scanning 2 * t _Pulse* freq time.Half the for these scannings (that is, for t _Pulse* freq time scanning), output that can driver is set to V1 or V2, and it can equal respectively-V and Vcom usually.Thus, in these scannings, pixel or driving perhaps remain on identical show state for negative.For second half of scanning, can driver be outputted to V2 or V3, it can equal Vcom and+V usually respectively.In these scannings, pixel or driving perhaps remain on identical show state for just.Following these options of table 1 explanation are driving or hold modes that how to make up to be created in arbitrary direction; The negative driving that just drives and can obtain bright state that can obtain black state certainly accordingly is a kind of function of used specific electro-optical medium.

Table 1 obtains the drive sequences of bi-directional drive pulse with the maintenance of STN driver

There is multiple distinct methods to arrange two parts of this drive scheme (that is, two dissimilar scanning or " frame ").For example, two types frame can replace.In fact when in the frame that replaces, driving in the opposite direction, if carry out with high refresh rate, electro-optical medium can show luminous and deepening simultaneously so.Optional, all frames of one type can be in any appearance before of second type frame; This can cause the driving external characteristic in a kind of two steps.Certainly other layout also is fine; For example follow the frame of two or more opposite types with more one type frame for two.In addition, if in one of both direction, there is not pixel to need to drive, can cancel the frame of this polarity so, 50% ground reduces driving time.

When first variable can only produce binary picture, second variable can provide the image with multi-grey level.This is to realize through the drive scheme that combines above-mentioned width modulation to different pixels.In this case, again to scanning of a display 2 * t _Pulse* freq time, but in these enough scannings, only provide driving voltage to guarantee to obtain the desired pulse of particular pixels to arbitrary particular pixels.For example, for each pixel, can write down the total pulse that is provided, when pixel reached the pulse of its expectation, this pixel can remain on end face voltage in the scanning below all.For need be to be less than the pixel that total scanning time drives; The time of drive part (promptly; At the show state of pixel for a change the time portion of pulse is provided, the retaining part of show state of simply keeping pixel with the voltage that is provided is relative) can be distributed in total time with diverse ways.For example, whole drive parts can be set to begin in beginning place of total time, and perhaps whole drive parts can change at the end of T.T. and regularly accomplishing.As in first variable, if no longer including the pulse of particular polarity, the arbitrary time in second variable need offer arbitrary pixel, can cancel the scanning that this polar impulse is provided so.This possibly mean whole pulse meeting shortening, for example, if the maximum impulse that provides with the positive and negative direction allows pulse less than maximum.

Take the situation of high simplified for illustrative purposes, suppose that the above-mentioned grey scale solutions that is used for display has four gray levels, be i.e. black (0 grade), dark gray (1 grade), bright gray scale (2 grades) and white (3 grades).In the table 2 below overview a kind of possible drive scheme of such display.

Table 2

Frame No.	1	2	3	4	5	6
							Parity	Very	Idol	Very	Idol	Very	Idol
Conversion
							0-3	+	0	+	0	+	0
0-2	+	0	+	0	0	0
							0-1	+	0	0	0	0	0
0-0	0	0	0	0	0	0
							3-0	0	-	0	-	0	-
2-0	0	-	0	-	0	0
							1-0	0	-	0	0	0	0

Although in reality, can use the more frame of more number usually, explanation supposes in this drive scheme, only to use six frames for ease.These frames alternately are odd and even number.Be tending towards white conversion (that is, the conversion that gray level increases) and only in odd-numbered frame, drive, and the conversion that is tending towards deceiving (that is, gray level reduce conversion) only drives in even frame.In arbitrary frame that does not drive pixel, its remain on public before on the identical voltage of electrode, as in table 2 by " 0 " indication.(Hei-Bai) conversion in each odd-numbered frame, can provide one to be tending towards white pulse (that is, pixel capacitors being remained on a voltage that trends towards increasing the pixel gray scale with respect to electrode before public) in the frame 1,3 and 5 for 0-3.On the other hand, for 0-2 (black in bright gray scale) conversion, only in frame 1 and 3, providing one is tending towards white pulse, and pulse is not provided in frame 5; Yes for this at random, for example, can in frame 1 and 5, apply one and be tending towards white pulse and in frame 3, do not apply pulse.For 0-1 (black in dark gray) conversion, only applying one at frame 1 frame is tending towards white pulse, and does not apply pulse at frame 3 and 5 frames; In addition, this also is at random, for example can in frame 3, apply one and be tending towards white pulse, and not apply pulse at frame 1 and 5 frames.

The conversion that is tending towards deceiving is to handle with a kind of method that is similar to very much the conversion that is tending towards white accordingly, except this pulse that is tending towards deceiving only applies in the even frame of this drive scheme.Believe that the technician who drives the electro-optic displays field can be readily appreciated that the method for unshowned conversion in table 2 through the description of front.

Above-mentioned pulsegroup can be independence (stand-along) conversion between two images, and perhaps they also can be the parts for the pulse train of accomplishing image transitions (as with magic lantern (slide-show) waveform) that is designed.

Above although emphasis has been placed on the method that allows to be used for the conventional driver that uses together with LCD and design of the present invention; But the present invention also can use the driver of customization and a kind of being used for accurately to control the driver of grey states at electro-optic displays, and will introduce the realization that writes fast of display now with reference to Fig. 6 and 7.

As stated, at first, many electro-optical mediums are in response to a potential pulse, and this pulse can be expressed as V timing t (or more conventional, by the integration of V with respect to t), and wherein V is the voltage that is applied to pixel, and t applies this voltage institute elapsed time.Thus, can be through modulation to the potential pulse length that is applied to display, perhaps through to applying the modulation of voltage, perhaps their both combinations obtain grey states.

In the situation of the width modulation of Active Matrix Display, available pulse width resolution is the inverse of display refresh rate.In other words, for the display of 100Hz refresh rate, pulse length can be sub-divided into the interval of 10ms.This is because of each pixel addressing in the display in each scanning once, exactly when the selection wire of pixel in that delegation is activated.In all the other times, described in the WO01/07961 that mentions in front, the voltage on the pixel can be kept by holding capacitor.Along with the response speed of electro-optical medium accelerates, can be more and more precipitous with respect to the slope of the reflectance curve of time.Thus, in order to keep identical gray level resolution, the refresh rate of display must corresponding increase.The increase of refresh rate causes higher power consumption, finally the charging of pixels and line capacitance in the shorter and shorter time, becomes impossible like expectation transistor and driver.

In yet another aspect, in the voltage modulated display, pulse resolution just confirmed by the number of voltage level, and is independent of the speed of electro-optical medium.Nonlinear Distribution through utilizing electric pressure can increase effective resolution, and they concentrate on the most precipitous place of voltage/reflectivity responses of electro-optical medium.

Accompanying drawing 6 has schematically shown the balance between width modulation (PWM) and voltage modulated (VM) mode.Transverse axis is represented pulse width, and the vertical axes representative voltage.Be expressed as one as the reflectivity based on the electrophoretic display device (EPD) of particle of the function of these two parameters and have the district and contour map at interval that is illustrated in the difference of 1L* in the display reflects brightness, wherein L* has the definition of ICE commonly used:

L*＝116(R/R ₀) ^1/3-16

Wherein R is a reflectivity, and R0 is the value of a standard reflectivity.(found empirically that difference in 1L* brightness is significant for the mean value theme just in two excitations test.) the specific electrophoretic medium based on particle response time with the 200ms that locates at maximum voltage (16V) as shown in the figure of in this test, using of in Fig. 6, summing up.

The effect of width modulation can be confirmed by the segment that crosses along top, horizontal separately, and the effect of individual voltage modulation is found out through the vertical edge on inspection right side.Can be clear that from this segment, be in width modulation (PWM) pattern, to drive with the refresh rate of 100Hz if use the display of this particular medium, can not obtain the reflectivity in ± 1L* in the middle gray zone of profile steepest so.In voltage modulated (VM) pattern, the reflectivity that obtains in ± 1L* can need 128 grades of equally spaced voltage levels, simultaneously with low frame frequency operation (certain, as to suppose that the voltage hold facility that is provided by capacitor is sufficiently high) to 5Hz.In addition, can combine these two kinds of methods with the littler same precision of voltage level acquisition.In order further to reduce required voltage progression, can be in the precipitous segment set in the centre of curve shown in Fig. 6 and sparse in exterior lateral area with them.This can accomplish with the input gamma electric voltage of peanut.In order further to reduce required voltage progression, can they be concentrated on the favourable value.For example, if in the addressing time of being distributed, use very little voltage can not satisfy any desired grey states conversion, so such small voltage is for realizing that conversion is otiose.The voltage distribution of selecting to get rid of such small voltage can make the voltage that is allowed have more favourable distribution.

Point out as top; Because bistable electro-optic displays is for the polar sensitive of the electric field that applies, the polarity of driving voltage so that kind that is unlike among the LCD to be done is overturn in continuous frame (image), and frame; Pixel and line upset all are unnecessary, and in fact can have the opposite effect.For example, the lcd driver that has the pixel upset is carried the voltage that changes polarity in the frame that replaces.Like this, only possibly in half the frame, carry the pulse of suitable polarity.This is not a problem in LCD, because liquid crystal material is insensitive to polarity, still in bistable electro-optic displays, needs the time addressing electro-optical medium of twice.

Similarly, because bistable electro-optic displays is pulse transducer rather than voltage sensor, so display integral voltage error in time, this can cause the pixel of display to depart from the big skew of their expectation optical states.This makes and uses the driver with high voltage precision to become very important, recommends use ± 3mV or littler tolerance.

In order to make driver can come the display panel of the monochromatic XGA of addressing (1024*768), need the maximum pixel clock rate of a 60Hz with the refresh rate of 75Hz; Obtain such clock frequency in the present art.

As already mentioned, be the stability of their images based on the electrophoresis of particle and a major advantage of other similar bistable electro-optic displays, and then have an opportunity with extremely low power consumption operation display.Utilize this chance substantially, when image does not change, can disable to the power supply of driver.Therefore, driver can be designed as under the situation that does not produce any stray voltage on the output line and comes power down with a kind of controllable mode.Can become a kind of common event because get into and leave such " sleep " pattern,, and will on the serviceable life of driver, have minimum influence so power down and the order that powers on are fast as much as possible.

In addition, should having one, to make all output pins of driver be the input pin of Vcom, and it can remain on all pixels on their current optical states under the situation of not power down of driver.

Driver of the present invention is useful, wherein in particular for the driving high definition medium, and the portable display of high information capacity, for example 7 inches (178mm) diagonal line XGA monochrome displays.For the number of integrated circuit required in such high resolution panel minimizes, need to use driver with the every high number of encapsulation (for example, 324) output.Also needing this driver to have one operates in the option under a kind of or more kinds of other pattern and has less output enable.The method for optimizing that is placed on integrated circuit on the display panel is to be with to carry to encapsulate (TCP), so just needs the size of arrangement driver output and places the use that is beneficial to this method.

This driver is typically used in little voltage to about the 30V and comes the driven medium active matrix board.Therefore, this driver needs to drive the capacitive load of about 100PF.

In accompanying drawing 7, provided the block diagram of preferred driver of the present invention (being designated as 200 usually).Driver 200 comprises shift register 202, data register 204, data latches 206, digital analog converter (DAC) 208 and output buffer 210.This driver is different from those places that are generally used for driving LCD and is that it provides a polarity bit relevant with each pixel of display, and produces one in the output up and down of end face voltage through the control of corresponding polarity bit.

Provide in the signal description table 3 below of this preferred driver:

Driver 200 is operated by following mode.At first, be that height provides a starting impulse to make shift register 202 reset to an initial state through setting (for example) DIO1.(technician in the display actuation techniques field can be readily understood that; The various DIOx inputs that provide to shift register can make driver and the display with varying number row use together; But only use in these inputs for arbitrary given display, and being restricted to forever of other is low.) now shift register will operate with the usual manner that in LCD, uses; In each CLK1 pulse place, have one and have only one to uprise in 162 outputs of shift register 202, other maintenance low level, and when each CLK1 pulse position of this high level output transform.Schematically show like Fig. 7, each in 162 outputs of shift register 202 all is connected to two inputs of data register 204, a strange input and an idol input.

Display controller (comparison diagram 2) provides the polar signal D0POL and the D1POL of two six digit pulse value D0 (0:5) and D1 (0:5) and two single positions in the input of data register 204.At the rising edge of each time clock CLK1, in conjunction with shift register 202 selected (high level) output, (D0POL+D0 (0:5) and D1POL+D1 (0:5)) is written in the register of data register 204 with two seven figure places.Thus, after 162 time clock CLK1, be written to 324 seven figure places (with respect to the pulse value that is used for complete delegation in the frame demonstration) in 324 registers of data register 204.

At the rising edge of each time clock LCK2, these 324 seven figure places are sent to data latches 206 from data register 204.These numbers that are placed in the data latches 206 are read by DAC208; And in a usual manner; The corresponding analogue value is placed on output place of DAC208; And pass through the row electrode that impact damper 210 is fed to display, there they are offered by the line driver (not shown) by the pixel capacitors in the delegation of usual manner selection.But, it is pointed out that by the polarity bit D0POL or the D1POL that are written in the data latches 206 and control the polarity of each row electrode that these polarity can not change like the usual manner that in LCD, uses like this between the adjacent columns electrode corresponding to Vcom.

Fig. 8 is that one of explanation can be by the process flow diagram of the program of the controller unit shown in Fig. 1 and 2 operation.This program (generally being designated as 300) is used for using together with look-up-table method of the present invention (hereinafter have more and describe in detail), and wherein when each image write or refreshes, all pixels of display were wiped free of and addressing again.

Program starts from controller initialized " powering on " step 302, and this is the result of user's input usually, and for example the user presses the power button of personal digital assistant (PDA).Step 302 also can be caused by following mode; For example; The opening of PDA box (can survey this opening) by mechanical pick-up device or photoelectric sensor; Input pen leaves moving of its shelf on PDA, survey and move when the user picks up PDA, or when user's hand survey during near PDA near detection.Next procedure 304 is " resetting " steps, wherein all pixel driven of display is arrived their black and white state.Have been found that at least that in some electro-optical mediums in the writing successively of image, this " flicker " of pixel is for guaranteeing that accurate grey states is essential on display.Need at least usually also to find 5 flickers (calculating black continuously and white each time state) for once glimmering, perhaps in some cases more times.The number of times that glimmers is many more, and the time of cost and energy are just many more in this goes on foot, and can see on display that the user the before necessary elapsed time of desired images is also just long more thus simultaneously.Therefore, just hope under meeting the situation that writes accurate grey states supply in the image subsequently, to make the number of times of flicker as much as possible little.When reset process 304 finished, all pixel of display was all at identical black or white state.

Next procedure is to write or " seeing image off " step, and its middle controller 16 is seen signal off to row and column driver 22 and 24 (Fig. 1 and Fig. 2) respectively with the method for having said, on display, writes desired images thus.Because display is bistable; So in case image writes; Do not need to rewrite at once, and thus after writing image, controller through being set, blanking signal (for example signal BL is set to height in Fig. 7) interrupts row and column driver writing display usually.

Controller has got into one by step 308 now, the judgement circulation of 310 and 312 formations.In step 308, whether controller 16 inspection computing machines 12 (Fig. 1) ask the demonstration of a new images.If controller continues, in an erase step 314, will in step 306, be written to the image wipe of display, thus display is turned back to the state that arrives when reset process 304 finishes basically.Controller turns back to step 304 from erase step 314, foregoing resetting, and continue to write new image.

If in step 308, there is not to be written to the new images of display, controller advances to step 310, determines there when the image that on display, has kept surpasses a predetermined period.Such as the technician in display technique knowledge, being written to image on the bistable state medium is not to keep indefinite duration, image can fade away gradually (that is, contrast reduces).In addition; In the electro-optical medium of some types; Electrophoretic medium is particularly weighed between the writing speed of medium and bistable state through regular meeting because several hours with kept in several days bistable medium basically than only kept several seconds or a few minutes bistable medium have the longer write time.Therefore, although continuous rewriting electro-optical medium need not resembling in the situation in LCD for the image with good contrast is provided, need come refreshed image with the interval of (for example) a few minutes.Thus; Judge since in step 306, writing image at step 310 middle controller and to begin the over and done with time and whether surpassed predetermined refresh interval; If; Controller proceeds to erase step 314 and arrives reset process 304 then, resets as stated, and continues identical image is rewritten on the display.

(can become simultaneously in the program shown in Fig. 8 and to use local and overall the rewriting, like more detailed description hereinafter.Step 310 whether needs local or overall the rewriting if like this, will change decision into.If in the program of conversion, program judges that preset time does not expire, and will not operate at step 310 place.If but the schedule time arrive, step 310 is the wiping and rewriteeing of calling graph picture at once not, but only be provided with an indication generally to the renewal of next image than more effective mark (usually at the term aspect the computing machine) partly.Program arrives step 306 in the next time, and certification mark is if be provided with this mark, then to the overall rewriting of image with remove this mark then.But if this mark is not set, then just effective to the part rewriting of image.)

If judge that in step 310 refresh interval does not also exceed, controller advances to step 312, has judged whether to close the time of display and/or figure image source there.In order in mancarried device, to preserve energy, controller can not allow a single image to refresh down indefinitely, as shown in Figure 8 can be after the no operating cycle of a prolongation terminator.Therefore; Judge at step 310 controller whether " closing " cycle of after the new image rewriting of preceding image (rather than) is written to display, being scheduled to (greater than refresh interval above-mentioned) expires; If as 314 represented, program stops.Step 314 can comprise the power down of figure image source.That is, stop the back user and can also on display, visit the slowly image of desalination in such program.Do not close the cycle if also exceed this, then controller turns back to step 308 from step 312.

The various possible waveform that by way of example method introduction only is used to carry out look-up-table method of the present invention.But, at first will introduce some general provisions as used waveform among the present invention.

The waveform that shows the bistable display of foregoing storage effect can be divided into main two types, i.e. offset-type and non-compensated.In the offset-type waveform, consider that the arbitrary storage effect in pixel is carried out minute adjustment to whole pulses.For example, the pixel of the series conversion of an experience gray level 1-3-4-2 can receive that a pixel with experience 1-2-4-2 conversion compares the slightly different pulse that is used for the 4-2 conversion.Such impulse compensation can be through regulating impulse length, voltage or the V (t) through pulse distribute other change and carry out.In non-compensated waveform, have no consideration any in the behave of (being different from original state) of preceding status information.In non-compensation waveform, the pixel of all experience 2-4 conversions can be received identical pulse.In order to make non-compensated wave form merit work, must meet one of two conditions.One is electro-optical medium performance storage effect not in its blocked operation, and any storage effect in the pixel must be effectively eliminated in perhaps each conversion.

Generally, non-compensation waveform is best suited for the system that can only carry out thick pulse resolution.For example be display, perhaps have only the display of 2-3 position voltage conversion capabilities with three grades of drivers.The compensation waveform needs accurate pulse regulation, is impossible with such system.Obviously, when rough pulse system preferably was limited to non-compensation waveform, the system with accurate pulse regulation can realize this waveform of two types.

The simplest non-compensation waveform is 1 a normal image stream (1 GIF).In 1 GIF, show that conversion arrives the next one reposefully from a white image of black.Transformation rule to this sequence can carry out simply as follows: black if image is changed to from white cut, pulse I then is provided.If it switches to whitely from black, the pulse of opposite polarity then is provided ,-I.If image keeps identical state, then pulse is not provided to pixel.Like front regulation, pulse polarity can rely on the respective function (function) of material for the mapping of the polarity of voltage of system.

The another kind of non-compensation waveform that can produce gray level image is a non-offset-type n prepulsing magic lantern (n-PPSS).This non-compensation magic lantern (slide show) waveform has three essential parts.At first, wipe pixel to unique optical states, normally white or black.Then, pixel is driven between two optical states backward or forward, still white usually and black.At last, pixel being addressed to one can be the new optical states of grey states more than.Finally (or writing) pulse is called as addressing pulse, and other pulse (first (or wiping) pulse and centre (or blanking) pulse) is collectively referred to as prepulsing.Such waveform can be described with reference to Fig. 9 and 10 below.

Prepulsing magic lantern waveform can be divided into two citation forms, have odd number prepulsing with have even number prepulsing.For the situation of odd number prepulsing, the erasing pulse meeting in pulse, equate with relatively directly in the preceding pulse description of Fig. 9 and hereinafter (still referring to) the antipole property that writes.In other words, if pixel is write ash from black, the erasing pulse meeting makes pixel turn back to black state.In the situation of even number prepulsing, the erasing pulse meeting have with directly preceding write pulsion phase with polarity and also can equal from deceiving in the pulse sum that preceding writes pulse and erasing pulse to the required pulse of white complete conversion.In other words, if pixel writes from black in the situation of even number prepulsing, must it be erased to white so.

After erasing pulse, waveform comprises zero or even number blanking pulse.These blanking pulses normally equate but opposite polarity pulse, are arranged to first pulse to be and erasing pulse antipole property.These pulses are generally equal to whole deceiving-white pulse, but this is not a necessary condition.Also can only need pulse equate but opposite polarity pulse having-can be the pulse that is linked at paired great changes together, promptly+I ,-I ,+0.1I ,-0.1I ,+4I ,-4I.

The pulse that provides at last is to write pulse.To the selection of this pulse only based on desired optical states (do not rely on current state, or any) at preceding state.Generally, this pulse meeting adds deduct few with grey states value monotone increasing, but this is optional.Owing to being in particular rough pulse system use, this waveform designs; So generally can be included in the mapping of one group of expectation grey states on the possible pulse choice of peanut to the selection that writes pulse, for example 4 grey states in 9 kinds of pulses that possibly apply.

The inspection of n the prepulsing magic lantern waveform of non-compensation of dual numbers or odd number form can demonstrate and write pulse and always begin from identical direction, promptly from black perhaps from vain.This is the key character of this waveform.Because the principle of non-compensation waveform is can't be for guaranteeing that pixel reaches identical optical states paired pulses length and compensates accurately, so can not look to when reaching consistent optical states when setting about from antipole end optical states (black or white).Therefore, for one of these forms that can be designated as " from black " and " confession ", there are two kinds of possible polarity.

A major defect of this type waveforms is between image, to have the optical flicker of amplifying greatly.As said hereinafter, can be that order is upgraded in half pixel conversion through the superframe time, and improve with high resolving power staggered scanning pixel with reference to Fig. 9 and 10.Possible pattern comprises every at a distance from (every) other row, and is every at a distance from other row, or the inspection plate pattern.Notice that this does not also mean that and use relative polarity, promptly " from black " to " confession ", because this can cause not matching of on adjacent image point gray scale.As substituting; Can pass through with (promptly half pixel; First group of pixel accomplished erasing pulse, and second group of pixel begins erasing pulse and first group of pixel begins first blanking pulse then) postpone more NEW BEGINNING with one " superframe " (a frame group that equals the maximum length that Hei-Bai upgrades) and realize.Consider that this need increase a superframe for total update time synchronously.

Can find out that at first Perfected process of the present invention can be called " common grayscale image flow ", the writing of its each image of middle controller arrangement, each pixel can directly be transformed into its final gray level from its initial grey levels like this.But in fact, common grayscale image flow faces the problem from the accumulation of error.Because following practical work, for example by driver, electro-optical medium causes the variation that in voltage output, is difficult to avoid in the variation of the production on the thickness etc., is applied to the inevitable and theory of pulse on arbitrary given gradation conversion and need has difference.Suppose that average error in every kind of conversion is expressed as display and in theoretical difference terms with the actual frame reflectivity is ± 0.2L*.Through 100 conversions continuously, pixel can demonstrate a mean deviation from their desirable 2L* states; This skew is tangible for general viewers in the image of some type.For fear of this problem, need be arranged to the drive scheme that uses in the present invention in that before, arbitrary given pixel can only experience the gradation conversion of a predetermined maximum number through an extreme optical state (black or white).These extreme optical state are as " fence " after on electro-optical medium, having applied certain pulses, and it is more black or whiter that medium can not become.Thus, the conversion next time from extreme optical state always can begin from the optical states of accurately knowing, and has effectively compensated for any error in preceding accumulation.Through extreme optical state the minimized various technology of optical effect of such one section pixel will be described below.

At first; Has black (0 grade) referring now to a kind of, dull gray (1 grade), bright ash (2 grades) and white (3 grades) optical states; Use pulse modulation technology and simple two gray scale systems, introduce useful in the present invention simple drive scheme as realizing at the conversion query table shown in the following table 4 changing.

Table 4

Conversion	Pulse	Conversion	Pulse
				0-0	0	0-0	0
0-1	n	1-0	-n
				0-2	2n	2-0	-2n
0-3	3n	3-0	-3n

Wherein n is a number according to particular display, but and-n representes a pulse that has with pulse n equal length opposite polarity.Also further suppose the end of the reset pulse 304 in Fig. 8, all pixels of display all are black (0 grades).Therefore, as described below, all conversions all take place through the black state in a centre, and having only those is effective to this grey states or from the conversion of this grey states.Like this, required question blank size obviously reduces, and obviously the scale factor according to the question blank size that reduces can increase along with the number of display gray level.

Fig. 9 has shown a pixel conversion relevant with the drive scheme of Fig. 8.At the place that begins of reset process 304, pixel is in a certain random greyscale.In reset process 304,, finish at its black state with pixel driven to three a black state and two white states in centre.Write for the first image suitable gray level to pixel at 306 places then, suppose it is 1 grade.This pixel keeps a period of time on this level during this identical image shows; Length for the ease of the explanation display cycle in Fig. 9 has reduced greatly.Sometimes a new images need write; In this; Pixel turns back to black (0 grade) in erase step 308; Then in being appointed as 304 ' second reset process through replacing 6 times white and black reset pulses, in this reset process 304 ' end, pixel has turned back to black state like this.At last, in being appointed as 306 ' second write state, write one for the second image suitable gray level, suppose it is 2 grades to pixel.

That yes is possible for many different drive scheme among Fig. 9.A kind of useful variation has been shown in Figure 10.In the step 304 shown in Figure 10,306 with 308 the same with among Fig. 9.But; In step 304 ' in; Used 5 reset pulses (obviously also can use a different odd number impulse), like this in step 304 ' end, pixel is at white state (3 grades); And in second write step 306 ', pixel write be realize from white state rather than realize from resembling the black state described in Fig. 9.Consecutive image is just alternately from the black state of pixel and writing of white state like this.

In the variation of the another drive scheme shown in Fig. 9 and 10, erase step 308 is not deceived according to the driving pixel but white (3 grades) are realized.Then in reset process under white state the even number reset pulse be added to the pixel end, write second image from white state.Like drive scheme, in this programme, alternately write continuous images with white state from the black state of pixel at Figure 10.

Be appreciated that in all in front schemes that according to the characteristic of employed electro-optical medium, the number of reset pulse and duration can change.Similarly, can change the pulse that is applied to pixel with voltage modulated rather than width modulation.

The black lightning that in the reset process of above-mentioned drive scheme, on display, shows dodges with white that yes is visible for the user, and possibly dislike for a lot of users.In order to reduce the visual effect of this reset process, can be easily the pixel of display be divided into two (or more) group, and dissimilar reset pulses be provided different groups.More particularly, use if desired reset pulse drive any given black and white between the pixel that replaces, can easily pixel be divided at least two groups, and arrange drive scheme to make one group of pixel driving drive to black for white another group simultaneously.This two groups the space distribution that is provided be meticulously select and also pixel all enough little; The user experiences reset process just as the interval of the gray scale on display (what preferably some were slight flashes), and such gray scale induces one to detest unlike a series of black and white flicker at interval usually.

For example, in such " two groups reset " step of a kind of form, the pixel on odd column can be assigned as one " very " group, and the pixel in even column is assigned to second " idol " group.Then the odd number pixel can use at the drive scheme shown in Fig. 9, and the even number pixel can use the mutation of this drive scheme, and wherein pixel is not to be driven to black state but white state in erase step.These two groups of pixels all can experience the even number reset pulse in reset process 304 ' then, be used for this reset pulse of two groups like this and can separate 180 degree phase places basically, and display is shown as ash in whole reset process.At last, in step 306 ' second image write during, the odd number pixel is from the black end-state that is driven into them, and the even number pixel is from be driven into their end-state in vain.In order to ensure in the very long time with identical method each pixel (and the method that resets does not so cause any noise on display) that resets; Between consecutive image, switching this drive scheme is favourable for controller; When being written to display to a series of new images, each pixel is alternately to be written to its end-state from black and white state like this.

Obviously, can use by the pixel in the odd-numbered line and form first group and pixel in even number line forms second group similar scheme.In another similar drive scheme, first group of pixel that is included in odd column and the odd-numbered line, and even column and even number line, and second group of pixel that is included in odd column and the even number line, and even column and odd-numbered line are pressed the chessboard arranged in form for such two groups.

Replace or except pixel being divided into two groups and be arranged in the 180 degree phase places that differ in reset pulse and another group in a group, can pixel be divided into the group of use distinct different reset pulses on quantity and pulsed frequency.For example, one group can be used 6 pulsed reset sequences as shown in Figure 9, and second group of 12 pulse that can use similar doubled frequency.In more accurate scheme, pixel can be divided into four groups, and but first and second groups are used 6 pulse schemes differ 180 degree phase places each other, and third and fourth group used 12 pulse schemes but differ 180 degree phase places each other.

To be illustrated as another program of the adverse effect that reduces reset process now with reference to Figure 11 A and 11B.In this scheme, pixel is divided into two groups again, second (odd number) group of pressing first (even number) group of drive scheme shown in Figure 11 A and pressing the drive scheme shown in Figure 11 B.Equally in this scheme, black and white in the middle of all gray levels be divided into first group of contiguous dull gray level against black level, and second group of contiguous bright ash level against white level is the same for two groups of this point-scores of pixel.The expectation but not necessarily, in these two groups, have the gray level of similar number; If the odd number gray level is arranged, intergrade can Random assignment be given arbitrary group so.For the ease of explanation, Figure 11 A and 11B illustrate this drive scheme provides 8 grades of gray scales to show, is appointed as the grade of 0 (deceiving) to 7 (in vain);

Gray level

1,2 and 3 is dull gray levels, and gray level 4,5 and 6 is bright ash levels.

In the drive scheme of Figure 11 A and 11B, control the conversion between gray scale according to following rule:

(a) at first; The even sets pixel; In the conversion of dull gray level, the final pulse that is provided always one be tending towards white pulse (that is, have tend to pixel) from of the pulse of its black state to the polarity of its white state-driven; Otherwise in the conversion of bright ash level, the final pulse that is provided is a pulse that is tending towards deceiving always.

(b) secondly, the odd number group pixel, in the conversion of dull gray level, the final pulse that is provided is a pulse that is tending towards deceiving always, and in the conversion of bright ash level, the final pulse that is provided always one be tending towards white pulse.

(c) in all situation, after obtaining white state, the pulse that is tending towards deceiving can be only after being tending towards white pulse, and after obtaining black state, being tending towards white pulse can be only after the pulse that is tending towards deceiving.

(d) the even number pixel can not be driven into from a dull gray level by a single pulse that is tending towards deceiving black, the odd number pixel can not use yet one single be tending towards white pulse from bright ash level in vain.(obviously, in two kinds of situation, can only use one finally to be tending towards white pulse and to obtain white state, also can only obtain black state with a pulse that finally is tending towards deceiving.)

These regular application allow to use maximum in three a consecutive pulses conversion that realizes between gray scale.For example, Figure 11 A shows black through associating (0 grade) even number pixel to the conversion of gray level 1.This is to be designated as 1102 the white pulse (in Figure 11 A, being expressed as a positive slope certainly) that is tending towards and to obtain with independent.Then, arrive gray level 3 to pixel driving.Because gray level 3 is dull gray levels, with good grounds rule (a) it must be tending towards white pulse through one and realize, and 1 grade thus/3 grades conversions can be controlled through an independent white pulse 1104 that is tending towards, it has a pulse difference with pulse 1102.

Arrived gray level 6 to pixel driving now.Because this is a bright gray level, it must be realized by a pulse that is tending towards deceiving according to rule (a).Therefore; Rule (a) and application need (c) are realized 3 grades/6 grades conversion by one two pulse train; Promptly one pixel driving to white (7 grades) first be tending towards white pulse 1106, and then one pixel from 7 grades of one second pulses 1108 that are tending towards deceiving of 6 grades that are driven into expectation.

Then arrive gray level 4 to pixel driving.Because this is a bright gray level,, realize 6 grades/4 grades conversion by an independent pulse that is tending towards deceiving 1110 according to foregoing the very similarly theoretical of 1 grade/3 grades of conversions that is used for.Ensuing conversion is to 3 grades.Because this is a dull gray level; According to foregoing the very similarly theoretical of 3 grades/6 grades of conversions that is used for; Control 4 grades/3 grades conversion by one two pulse train; Promptly one first pulse 1112 that be tending towards deceive of pixel driving to black (0 grade), and and then one is tending towards white pulse 1114 to pixel from 0 grade be driven into 3 grades of expectation one second.

In the final conversion shown in Figure 11 A is the conversion from 3 grades to 1 grade.Because this is a dull gray level, it must be tending towards white pulse by one and realizes according to rule (a).Therefore; Application rule (a) and (c); Must control 3 grades/1 grade conversion by a three-pulse sequence; This pulse train comprise one with pixel driving to white (7 grades) first be tending towards 1116, one of white pulses with second pulse 1118 that be tending towards deceiving of pixel driving to black (0 grade), and one is expected that from black being driven into the 3rd of 1 grade of state is tending towards white pulse 1120 with pixel.

Figure 11 B shows the sequence of the 0-1-3-6-4-3-1 grey states as the even number pixel among Figure 11 A of an odd number pixel realization.But, can see that used pulse train is very different.Rule (b) need realize 1 grade of a dull gray level through a pulse that is tending towards deceiving.Therefore, 0-1 conversion be by one with pixel driving to white (7 grades) first be tending towards white pulse 1122, and then one with pixel from 7 grades of 1 grade the pulse that is tending towards deceiving, 1124 realizations that are driven into expectation.The 1-3 conversion needs a three-pulse sequence; One with first pulse 1126 that be tending towards deceive of pixel driving to black (0 grade); One with pixel driving to white (7 grades) second be tending towards white pulse, and one with pixel from 7 grades of the 3rd pulses 1130 of being tending towards deceiving that are driven into 3 grades of expectation.Ensuing conversion is to 6 grades for bright ash level; This is to be tending towards white pulse through one to realize according to rule (b), 3 grades/6 grades conversions be through one comprise with pixel driving to the pulse that is tending towards deceiving 1132 of black (0 grade) with one with pixel driving to the two pulse trains realization of white pulse 1134 of 6 grades that expect be tending towards.6 grades/4 grades conversions are realized by a three-pulse sequence; Promptly one with the be tending towards white pulse 1136 of pixel driving to white (7 grades); One with the pulse that be tending towards deceive 1138 of pixel driving to black (0 grade), and one with the be tending towards white pulse 1140 of pixel driving to 4 grades that expect.4 grades/3 grades conversions are to comprise the be tending towards white pulse 1142 of pixel driving to white (7 grades) through one, and then one pixel driving are realized to two pulse trains of 3 grades the pulse of expecting that is tending towards deceiving 1144.At last, 3 grades/1 grade conversion is to be realized by an independent pulse that is tending towards deceiving 1146.

Can find out that from Figure 11 A and 11B this drive scheme guarantees that each pixel is along " sawtooth " shape and go; Wherein under the situation that does not change direction (although obviously pixel can in a static short or long cycle of arbitrary intermediate grey scales) each pixel from deceive be transformed into white, and black from being transformed in vain under the situation of change direction not subsequently.Thus, top rule (c) and (d) can replace by following single rule (e):

(e) in case pixel from an extreme optical state (promptly by the pulse of a single polarity; White or black) drive to antipole end optical states; Before it arrived foregoing antipole end optical states, pixel no longer received the pulse of opposite polarity so.

This drive scheme guarantees that the maximum only experience of a pixel equal (N-1)/2 time number purpose conversion thus, and wherein N is the number of grayscale levels before being driven into an extreme optical state; This has prevented that the serial distortion that the slight errors (unavoidable minor swing causes in for example by the voltage that driver provided) in each conversion ad infinitum accumulates in a gray level image from being tangible degree for the observer.In addition, this drive scheme is designed to even number and the odd number pixel always arrives given intermediate grey scales the other way around, that is, the final pulse in the sequence is to be tending towards white and under another kind of situation, to be tending towards deceiving in one case.If be written to a single gray level to the effective coverage of the display of the even number of a basic equal amount of maintenance and odd number pixel, " reverse direction " characteristic can make the flicker in this zone minimize so.

In two discrete groups, drive the drive scheme of pixel for other, from above said similar reason, when the sawtooth drive scheme of execution graph 11A and 11B, concentrate one's energy by even number and odd number group arrangement pixel.This arrangement need guarantee that any adjacent areas basically on the display will keep the odd and even number pixel of basic equal number, and on the same group the full-size of adjacent image point piece wants the enough little general viewers that makes to offer an explanation easily mutually.As stated, can satisfy these requirements with two group of pixels of checker board pattern arrangement.The random screen technology also can be used for the arrangement of two groups of pixels.But in the sawtooth drive scheme, the use of checker board pattern can be tending towards increasing the power consumption of display.In the arbitrary given row in such pattern; Adjacent image point can belong to opposite group; And all stand in the adjacent area of basic size of same grey level transition (general case) at all pixels, adjacent image point needing to be tending towards the pulse of opposite polarity in arbitrary preset time.Each is new when capable when writing, to continuous pixel in arbitrary row provide opposite polarity pulse need to row (source) electrode discharge of display with recharge.The technician who drives in the Active Matrix Display field knows, the discharge of row electrode and to recharge be a principal element of power consumption for displays.Therefore, the chessboard distribution makes the power consumption of display be tending towards increasing.

Power consumption and expectation avoid big phase on the same group between the adjacent area of pixel reasonably compromise be that pixel in every group is distributed into rectangle, the pixel in this rectangle all in same column only along the several pixels of this row continuity.With such arrangement, when overwritten area has identical gray level, have only when when a rectangle switches to another rectangle, just needing the discharge of row electrode and recharging.Desirable rectangle is 1 * 4 pixel, and the rectangle that is arranged in adjacent columns can not finish in delegation, that is, the rectangle in adjacent columns can have different " phase places ".Rectangle can be with perhaps round-robin method realization at random to the distribution of phase place in each row.

A benefit at the sawtooth drive scheme shown in Figure 11 A and the 11B is that as the part of display whole updating, any monochromatic areas of image can be black in upgrading to black single pulse in vain or in vain with one simply.For rewrite maximum time that such monochromatic areas spends just rewritings need maximum time half the of transition region between gray scale, the use of this characteristic to help the character of importing like the user, the fast updating of characteristics of image such as drop-down menu.Controller can check image upgrade whether need the conversion between any gray scale; If do not need, the image-region that need to rewrite can use quick monochrome more new model rewrite.Thus, the user can have input character, the fast updating of other of drop-down menu and display and user interaction features, and it seamlessly cooperates with upgrading more slowly of common gray level image.

As described in the common pending application sequence number 09/561424 and 09/520743 of preceding text; In a lot of electro-optical mediums; Particularly based on the electrophoretic medium of particle; It is desirable being used to drive direct current (DC) balance that the drive scheme of such medium has on whole expanded period meaning, and the algebraic sum of the electric current through particular pixels should be zero or as far as possible near zero, the design of drive scheme of the present invention will be devoted to this standard.More specifically, any conversion sequence that the question blank that uses in the present invention will be designed to a feasible extreme optical state that begins or end at pixel (black or white) should be a dc balance.According to mentioned above, can at first find out owing to this pulse, thus be constant basically through the required electric current of conversion between the arbitrary specific gray scale of pixel thus, so such dc balance may not be realized.Yet; This is genuine for first approximation just; Find empirically; At least in based on the situation of the electrophoretic medium of particle (and being genuine equally in the situation of other electro-optical medium), (for example) provides effect and the 250ms pulse that identical voltage is provided to pixel different of the 50ms pulse at 5 intervals to pixel.Therefore, passing through to exist in the electric current of pixel some flexible for obtaining given conversion, this flexible acquisition that can be used to participate in dc balance.For example; The question blank that uses in the present invention can store a plurality of pulses that are used for given conversion together with each the total current value that provides by these pulses; Controller can keep one to be used for storing the register that works the pulse algebraic sum that is provided to pixel from certain in the preceding time (for example, since pixel being maintained black state) for each pixel.When will be when white or grey states be driven into black state a particular pixels; Controller can be checked the register relevant with this pixel; Confirm the required electric current of dc balance the whole conversion sequence from original black state to black state on the horizon; And the white/ash of selecting to be stored that is used for is changed one of required some pulses to deceiving; In them any can accurately be reduced to zero with corresponding registers, perhaps is reduced to as far as possible little residual value (wherein corresponding registers can keep this residual value and in next one conversion, it is added on the electric current that is provided) at least.Can find out that using repeatedly of this process can obtain the accurate long-term dc balance of each pixel.

It should be noted that at the sawtooth drive scheme shown in Figure 11 A and the 11B and be very suitable for using such dc balance technology; Because this drive scheme is guaranteed can only pass through the conversion of effective quantity through between the passing through continuously of any given pixel of black state, and in its half the conversion, there is the pixel can be in fact on an average through black state.

Through using part rather than overall renewal can further reduce the ill-effect of reset process; Promptly through only rewriteeing in the display part that only between consecutive image, changes, can be in " part " zone or the part that selection will rewrite on basis of pixel one by one.For example, when for example explaining that the figure of component movement in the plant equipment perhaps is used for the figure of accident reconstruction, is not difficult to find a series of images that wherein smaller object moves with respect to bigger static background.In order to use local updating, controller need be compared final image and initial pictures and confirm that between two figure two ways is different and then need to rewrite.Controller can be confirmed one or more regional area, is generally the rectangular area that will upgrade pixel of preserving that has with the limit of pixel grillages row, need perhaps can only to confirm the independently pixel that upgrades.Arbitrary drive scheme of having described thus only can be used for upgrading perhaps pixel independently of the regional area confirming to rewrite as needs.Such local updating scheme can fully reduce the power consumption of display.

Characteristics according to used certain electric optical display unit can change above-mentioned drive scheme with several different methods.For example, can in above-mentioned drive scheme, save many reset process in some cases.For example; If used electro-optical medium for very macrocyclic bistable state (promptly; The gray level that writes pixel only changes with the very slow time); And the required pulse change of the particular conversion of carrying out with this cycle for the pixel that is in its initial grey states is little; Question blank can be arranged to the intervention that does not turn back to black or white state and directly realize the conversion between grey states, after through a basic cycle, only when " skew " gradually of their nominal gray level can cause the appreciable error of present image, just carries out resetting of display when pixel.Thus; For example, if the user with display of the present invention as electronic book reader, it can show the information of many screens before needing the resetting of display; Empirical ground; Have been found that and use suitable waveform and driver, before needs reset, can show, so in fact can not reset between to the read period of electronic book reader common like the information more than 1000 screens.

The personnel in display technique field are easy to find out that isolated system of the present invention can be used for providing with many different drive schemes under different condition.For example; Because in the drive scheme shown in Fig. 9 and 10; Reset pulse consumes very little part in the display total power consumption, so can come together to provide controller with first drive scheme of the display that resets with frequency interval, gamma error is minimized; And, allowed that so bigger error has still reduced power consumption only with the alternative plan of the display that resets than long interval.Can manually or rely on external parameter to be implemented in two kinds of switchings between the scheme; For example, if display can use first drive scheme, and when computer moves, can use alternative plan on the internal cell power supply as portable computer when computer moves on primary power.

According to noted earlier, can find out to the invention provides a kind of driver that electro-optic displays controls that is used for that it is very suitable for based on the bistable electro phoretic display of particle and the characteristics of similar display.

According to noted earlier, can find out to the invention provides a kind of method and controller of controlling electro-optic displays operation that it allows in the accurate control that does not need whole display with frequency interval gray scale under the situation of the flicker of the inconvenience of its extremity.The present invention also when reducing power consumption for displays, allows the accurate control of display regardless of the variation of temperature and its running time.Because can using from the commercial parts that get, controller constitutes, so can realize these advantages at an easy rate.

In residual voltage method of the present invention, expect to realize the measurement of residual voltage, for example a kind of metal-oxide semiconductor (MOS) (MOS) comparer by the high impedance voltage measuring apparatus.When display is a kind of little pixel that has, per inch 100 point (DPI) matrix displays for example, wherein each pixel has 10 ^-4Square inch or about 6 * 10mm ²Area, when the resistance of so single pixel arrives 10 ¹²During the quantitative value of ohm, comparer need have extremely low input current.But suitable comparer is easy in commercial acquisition; For example, the INA111 chip as the Texas Instrument with the input current that is merely about 20pA is suitable.(technical, this integrated circuit is a kind of instrumentation amplifier, if but its output gets into a Schmidt trigger, and it can be used as a comparer and uses.) for the display with big single pixel; For example be used to the big direct driving display (following regulation) that indicates; Each pixel possibly have several square centimeters zone; Requirement to comparer is not very high, and all basically commercial FET input comparators can use, for example from the LF311 comparer of National Semiconductor.

Personnel for the electronic display technology field are easy to find out; For expense and other reason; The electronic console of large-scale production can have the driver of special IC (ASIC) form usually, and in such display, comparer can provide as the part of ASIC usually.Although this approach can be provided at the feedback circuit among the ASIC, this has the power supply that makes ASIC and oscillating part is simpler and littler advantage on area.3 grades of normal image flow drivers if desired, and this method can also make the drive part of ASIC simpler and littler on area.Thus, this method can reduce the cost of ASIC usually.

Easily, using a kind ofly can provide driving voltage, makes pixel electrical short or unsteady driver that driving pulse is provided.When using such driver, on each addressing period of realizing the dc balance correction, pixel is addressed, and electrical short is floated then.(be meant on display the total cycle required from first image change to second image in the conventional sense of term " addressing period " in the electro-optic displays technology of this use.As above point out and since electrophoretic display device (EPD) lower be generally tens to the switch speeds of the hundreds of millisecond order of magnitude, an independent addressing period can comprise the scanning of many complete demonstrations.) after of short duration time delay, comparer is used to measure the residual voltage through pixel, and confirm on symbol it is just or negative.If residual voltage is for just, controller can prolong the cycle (perhaps increasing its voltage a little) of negative addressing pulse a little in next addressing period so.If but residual voltage is negative, controller can prolong the cycle (perhaps increasing its voltage a little) of positive addressing voltage pulse a little in next addressing period so.

Thus, the feedback cycle that residual voltage method of the present invention is placed on a kind of switching regulator with electro-optical medium just drives residual voltage through the length of regulating addressing pulse towards zero.When residual voltage near zero the time, media table reveals the life-span of perfect performance and raising.Especially, use of the present invention allows to improve the control to gray scale.Point out like the front, seen that the gray level that in electro-optic displays, obtains is a beginning gray level and the pulse that provides, and display is at the function of preceding state.One of reason of believing this " history " effect on (although the present invention does not receive this restriction of believing) gray level is that residual voltage acts on the electric field that electro-optical medium experiences; The actual electric field that influences medium state is the virtual voltage sum that is applied by electrode and residual voltage.Thus, the electric field of the control of residual voltage having been guaranteed to be experienced by electro-optical medium according to the present invention allows to improve the control of gray scale thus accurately corresponding to through the voltage that electrode provided.

Residual voltage method of the present invention is particularly useful in the display of so-called " directly driving " type; This display is divided into each a series of pixel that separate mesh electrode is provided, and this display further comprises the switching device shifter that is used for independently controlling the voltage that is applied to each separate mesh electrode.Direct driving display like this for text or other for example the demonstration of the limited character group of many numerals be useful, and be described in the International Publication No. of mentioning especially in front 00/05704.But residual voltage method of the present invention can also be used for the display of other type, for example has the Active Matrix Display of transistor matrix, and wherein each pixel of at least one transistor and display links to each other.The gate line of the thin film transistor (TFT) of the driving of in such Active Matrix Display, using (TFT) is connected to source electrode with pixel capacitors.Residual voltage is compared less than grid voltage (absolute value of residual voltage generally can not surpass 0.5V), so gate drive voltage conducting TFT all the time.Source electrode line can float for electricity then, and is connected to the MOS comparer, allows to read the residual voltage of each independent pixel of Active Matrix Display thus.

Although it should be noted that on the pixel of electrophoretic display device (EPD) residual voltage can the degree of the electric current of the pixel of dc balance closely connects with flowing through, zero residual voltage needn't mean desirable dc balance.But from practical point of view, this has no difference, because be that the history of residual voltage rather than dc balance is responsible for the adverse effect pointed out at this.

Personnel for the display technique field are easy to find out; Because the purpose of residual voltage method of the present invention is to reduce residual voltage and direct current imbalance; So this method needn't be used in each addressing period of display, it is to provide to prevent that the long-term direct current that forms is uneven on particular pixels with suitable frequency.For example; Need be if a kind of to use at interval the display of " refreshing " or " blanking " pulse, so refresh or blanking pulse in all pixels be driven to identical show state, normally a kind of extreme display state is (perhaps; More general; Can be at first with all pixel driving to one of extreme display state, then arrive another extreme display state again), this method of the present invention can refresh or blanking pulse in use.

Although residual voltage method of the present invention has been carried out description roughly in the application of encapsulated electrophoretic display, this method also can be used for non-encapsulated electrophoretic display, and the display of other type, for example shows the electrochromic display device (ECD) of residual voltage.

Said from preamble; Can find out that residual voltage method of the present invention provides a kind of method that is used to drive electrophoresis and other electro-optic displays; It is in the display serviceable life that increase is provided; In the time of action pane that strengthens and long-term display optical performance, reduced expense for the pixel dc balance equipment needed thereby of guaranteeing display.

Claims

1. method that drives bistable electro-optic displays; Said display comprises bistable state electric light dielectric layer, be arranged on the side of said electro-optical medium layer and limit said display first and second pixels first and second pixel capacitors and be arranged on the public electrode on the opposite side of said electro-optical medium layer, described method comprises:

(a) first public electrode voltages is applied on the public electrode; First gamma electric voltage is applied on said first pixel capacitors; And said first public electrode voltages is applied on said second pixel capacitors; Thereby electric field is applied on said first pixel of said display with a direction, and does not have electric field to be applied on second pixel basically; And

Second public electrode voltages that (b) will be different from said first public electrode voltages is applied on the said public electrode; Said second public electrode voltages is applied on said first pixel capacitors; And second gamma electric voltage is applied on said second pixel capacitors; Thereby do not apply electric field basically to said first pixel of said display, and electric field is applied on said second pixel of said display with opposite direction.

2. method as claimed in claim 1, wherein said displaying appliance are useful on the device that produces a plurality of different gamma electric voltages, and said first public electrode voltages is set to maximum gamma electric voltage and said second public electrode voltages is set to minimum gamma electric voltage.

3. method as claimed in claim 2 wherein is arranged on said gamma electric voltage between said first and second public electrode voltages with linear gradient.

4. according to the process of claim 1 wherein at a rewriting period of display repeating step (a) and (b) repeatedly.

5. according to the method for claim 4, the applying step that wherein in continuous rewriting period, replaces (a) and (b).

6. a bistable electro-optic displays comprises bistable state electric light dielectric layer, is arranged on the side of said electro-optical medium layer and limits first and second pixel capacitors of first and second pixels of said display, the display controller that is arranged on the public electrode on the opposite side of said electro-optical medium layer and is used for the voltage that is applied on said first and second pixel capacitors and the public electrode is controlled, and said controller is set to:

Second public electrode voltages that (b) will be different from said first public electrode voltages is applied on the said public electrode; Said second public electrode is applied on said first pixel capacitors; And second gamma is applied on said second pixel capacitors; Thereby do not apply electric field basically to said first pixel of said display, and electric field is applied on said second pixel of said display with opposite direction.

7. according to the display of claim 6; Has the device that is used to generate a plurality of different gamma electric voltages; And wherein said display controller is set to said first public electrode voltages is arranged to equal maximum gamma electric voltage, and the gamma electric voltage of will said second public electrode voltages being arranged to equal minimum.

8. according to the display of claim 7, wherein said gamma electric voltage is set to linear gradient.

9. according to the display of claim 7, wherein said controller is set in a rewriting period of said display, repeatedly repeat (a) and (b).

10. according to the display of claim 9, wherein said controller is set in continuous rewriting period, alternately use (a) and (b).