CN102074200A

CN102074200A - Methods for driving bistable electro-optic displays

Info

Publication number: CN102074200A
Application number: CN2010106210503A
Authority: CN
Inventors: K·R·阿蒙森; R·W·泽纳; A·克奈安; B·齐安
Original assignee: E Ink Corp
Current assignee: E Ink Corp
Priority date: 2003-03-31
Filing date: 2004-03-31
Publication date: 2011-05-25
Anticipated expiration: 2024-03-31
Also published as: KR20050116160A; JP2014063185A; JP5805167B2; JP2011008271A; HK1088107A1; JP2012133380A; JP2014059577A; CN102074200B; HK1128809A1; JP5005800B2; JP2006522372A; EP1614097A4; CN102768822A; CN102768822B; HK1157925A1; WO2004090857A1; JP5734395B2; EP1614097A1; HK1175579A1; JP4599349B2

Abstract

A gray scale bistable electro-optic display is driven by storing a look-up table containing data representing the impulses necessary for transitions, 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 a pixel voltage to be applied to the pixel. Compensation voltage data representing a compensation voltage is stored for each pixel, the compensation voltage for each pixel being calculated dependent upon at least one impulse previously applied to that pixel, and the pixel voltage is the sum of a drive voltage determined from the initial and final states of the pixel and the look-up table, and a compensation voltage determined from the compensation voltage data for the pixel. Other similar methods for driving such displays are also disclosed.

Description

Drive the method for bistable electro-optic displays

To be applicant E Ink Corp. submitted on 03 31st, 2004 the application, denomination of invention is divided an application for the Chinese patent application 200810176162.5 of " driving the method for bistable electro-optic displays ".

The application relates to international application no PCT/US02/37241, publication No. WO03/044765, and is by reference that their complete content is incorporated herein.

The present invention relates to be used to drive the method for electro-optic displays, particularly bistable electro-optic displays; The application also relates to the equipment that is used for these class methods.More particularly, the present invention relates to driving method and equipment (controller), they are used to realize the more accurate control of grey states of the pixel of electro-optic displays.The invention still further relates to the method for long-term direct current (DC) balance that realizes being applied to the driving impulse on the electrophoretic display device (EPD).The present invention especially but be not to estimate exclusively and be used based on the electrophoretic display device (EPD) of particle, in this electrophoretic display device (EPD) based on particle, the charged particle of one or more types is suspended in the fluid, and moves by fluid under electric field effects, thereby changes the outward appearance that shows.

The term " electric light " that is applied to material or display is used for representing to have the material of the first and second different show states of at least a optical properties in this article with its conventional sense in imaging field, by material is applied electric field, described material is changed into its second show state from its first show state.Though optical properties is the appreciable color of naked eyes normally, but also can be another kind of optical properties, for example transmittance, reflection, luminous, or the false colour on the meaning of the change of reflection of the electromagnetic wavelength under the situation of estimating to be used for the demonstration that machine reads, outside the visible range.

Term " grey states " is used for state in the middle of two extreme optical state of remarked pixel with its conventional sense in imaging field in this article, and represents that not necessarily the black and white between these two kinds of extremities changes.For example, some electrophoretic display device (EPD)s have been described in the some patents quoted below and the application of having announced, and extremity wherein is white and mazarine, and " grey states " is actually light blue in the middle of making.In fact, as mentioned above, the transformation between two extremities may not be a color change.

Term " bistable state " and " bistability " are used for representing to comprise the display of the display element with first and second different show states of at least one optical properties in this article with their conventional sense in field of display, make after the addressing pulse by finite duration drives any point element, in order to present its first or second show state, after addressing pulse finished, that state continued several times at least, for example changes at least four times of minimum duration of the required addressing pulse of status display module.In the Application No. of having announced 2002/0180687, show, some have gray scale capability based on the electrophoretic display device (EPD) of particle not only at its extreme black and white state but also all be stable in the grey states therebetween, also be like this for the electro-optic displays of some other type.Such display correctly is called " multistable " rather than bistable state, but for convenience's sake, term " bistable state " can be used for containing bistable state and multistable display in this article.

Term " gamma voltage " is used in this article representing that driver is used for determining being applied to the external voltage reference of the voltage on the pixel of display.Everybody will appreciate that, bistable state electric light medium do not show the relevant one to one type between the optical states feature of the voltage that applies and liquid crystal, the use of term " gamma voltage " not exclusively is equal to traditional LCD in this article, and wherein gamma voltage is determined the flex point in voltage level/output voltage curve.

Term " impulse (the impulse) " voltage with it in this article uses the conventional sense of the integration of time.But some bistable state electric light medium is as the electric charge transducer, for this class medium, can adopt impulse another definition, be electric current to the integration of time (it equal applied total electrical charge).According to medium is as voltage-time impulse transducer or as electric charge impulse transducer, should adopt the suitable definition of impulse.

The electro-optic displays of some types is known.One type electro-optic displays is the double-colored element type of rotation, for example (but such display often is called " rotation twin color ball " display described in the U.S. Patent number 5808783,5777782,5760761,6054071,6055091,6097531,6128124,6137467 and 6147791, or rather, it is preferably that term " rotates double-colored member ", because in the above-described patent of part, rotating member is not spherical).This display adopts a large amount of wisps (being generally spherical or cylindrical) and internal dipole of two or more parts with band different optical characteristic.These objects are suspended in the vacuole of the fluid filled in the matrix, and these vacuoles have been filled fluid, make object to rotate freely.The outward appearance of display is changed into to wherein applying electric field, thereby object is rotated to diverse location, and which part that changes object is by watching the surface to see.Such electro-optical medium is normally bistable.

The electro-optic displays of another kind of type adopts electrochromic media, for example comprises the electrochromic media of the form of electrode that is made of metal oxide semiconductor to small part and the millimicro optically variable films that appends to a plurality of dye molecule that have the reversible color ability on the electrode; For example referring to O ' Regan, people's such as B. " nature " (1991,353,737) and Wood, " the information demonstration " of D. (18 (3), 24 (in March, 2002)).Again referring to Bach, people's such as U. " Adv.Mater. " (2002,14 (11), 845).For example at U.S. Patent number 6301038, international application published WO01/27690 and in U.S. Patent application 2003/0214695, also described such millimicro optically variable films.Such medium also is bistable usually.

Be the electrophoretic display device (EPD) that the electro-optic displays of mainly researching and developing the another kind of type of theme is based on particle for many years, therein, a plurality of charged particles move through suspension under electric field influence always.Compare with LCD, electrophoretic display device (EPD) can have the attribute of good brightness and contrast, wide visual angle, state bistability and low-power consumption.But the problem that long-term image quality had of these displays has hindered their widespread use.For example, the particle that constitutes electrophoretic display device (EPD) tends to precipitation, makes the term of life of these displays not enough.

Announced recently and transferred Massachusetts Institute ofTechnology (MIT) and E Ink Corporation or with a large amount of patents and the application of its name, they have described encapsulated electrophoretic medium.This class encapsulation medium comprises many Caplets, and each capsule itself comprises and contains that the electrophoresis that is suspended in the fluid suspended medium moves the interior phase of particle and around the capsule wall of interior phase.Itself remains on capsule in the polymer adhesive usually, so that form the tack coat between two electrodes.For example, at U.S. Patent number 5930026,5961804,6017584,6067185,6118426,6120588,6120839,6124851,6130773,6130774,6172798,6177921,6232950,6249721,6252564,6262706,6262833,6300932,6312304,6312971,6323989,6327072,6376828,6377387,6392785,6392786,6413790,6422687,6445374,6445489,6459418,6473072,6480182,6498114,6504524,6506438,6512354,6515649,6518949,6521489,6531997,6535197,6538801,6545291,6580545,6639578,6652075,6657772,6664944,6680725,6683333 and 6704133, and Application No. 2002/0019081,2002/0021270,2002/0053900,2002/0060321,2002/0063661,2002/0063677,2002/0090980,2002/0106847,2002/0113770,2002/0130832,2002/0131147,2002/0145792,2002/0171910,2002/0180687,2002/0180688,2002/0185378,2003/0011560,2003/0011868,2003/0020844,2003/0025855,2003/0034949,2003/0038755,2003/0053189,2003/0096113,2003/0102858,2003/0132908,2003/0137521,2003/0137717,2003/0151702,2003/0189749,2003/0214695,2003/0214697,2003/0222315,2004/0008398,2004/0012839,2004/0014265 and 2004/0027327, and international application published WO 99/67678, WO 00/05704, WO 00/38000, WO 00/38001, WO00/36560, WO 00/67110, WO 00/67327, WO 01/07961, WO 01/08241, among WO 03/092077 and the WO 03/107315 such encapsulation medium has been described.

Above-mentioned many patents and application are recognized: the wall around discrete capsule in the encapsulated electrophoretic medium can be replaced by external phase, thereby produce so-called " electrophoretic display device (EPD) of polymer dispersed ", wherein electrophoretic medium comprises a plurality of discrete droplets of electrophoresis liquid and the external phase of polymeric material; And the discrete droplets of the electrophoresis liquid in the electrophoretic display device (EPD) of this polymer dispersed can regard capsule or microcapsules as, and is related with each individual drops even without discrete capsule film; Referring to for example above-mentioned 2002/0131147.Therefore, for the application, the electrophoretic medium that this base polymer disperses is counted as the subspecies of encapsulated electrophoretic medium.

Encapsulated electrophoretic display can not run into the clustering and the sedimentation fault mode of conventional electrophoretic device usually, and other advantage is provided, for example can prints or apply display on wide variety of flexible and rigid substrate.(use of speech " printing " is intended to comprise the printing and the coating of form of ownership, includes but not limited to: metering coating in advance, as sheet mould coating, slit or extrusion coating, slip or stacked coating, curtain coating; Roller coat is as knife-over-roll roller coat, forward and reverse roller coat; Gravure coating; Dip coated; Spraying; The crooked coating of liquid level; Spin coating; Brush; The air knife coating; Silk-screen printing technique; Electrostatic printing process; Hot stamping dataller skill; Ink-jet printing process; And other similar techniques.) therefore, the display that is produced can be flexible.In addition, owing to can print display medium (employing several different methods), therefore can make display itself at lower cost.

The electrophoretic display device (EPD) of correlation type is so-called " microcell electrophoretic display ".In microcell electrophoretic display, charged particle and suspension are not encapsulated in the capsule, but remain in a plurality of cavitys that form in the mounting medium that is generally thin polymer film.For example referring to international application published WO 02/01281 and U.S. Patent Application Publication No. 2002/0075556, they all transfer Sipix Imaging, Inc..

Though electrophoretic medium is opaque often (because for example in many electrophoretic mediums, particle has stopped the visible light transmissive display in fact), and carry out work with reflective-mode, but many electrophoretic display device (EPD)s can be made into so-called " shutter mode " and carry out work, wherein a kind of show state is opaque in fact, and a kind of then is printing opacity.For example referring to above-mentioned U.S. Patent number 6130774 and 6172798, and U.S. Patent number 5872552,6144361,6271823,6225971 and 6184856.Similar to electrophoretic display device (EPD) but dielectrophoretic displays that rely on electric field intensity to change can be carried out work by icotype; Referring to U.S. Patent number 4418346.

Based on the electrophoretic display device (EPD) of particle and show the bistable state of other electro-optic displays of similar performance or multistable performance and traditional liquid crystal (" LC ") display form distinct contrast.Twisted nematic liquid crystal action is not a bistable state or multistable, but as the voltage transducer, make pixel to this display apply given electric field and can produce particular grayscale on this pixel, and the gray shade scale that had before presented on the pixel therewith is irrelevant.In addition, the LC display only is driven with a direction (never transmission or " secretly " are to transmission or " bright "), and the reverse accommodation from brighter state to dark state is crossed reduction or eliminated electric field and realize.At last, the gray shade scale of the pixel of LC display is insensitive and only to its magnitude to the polarity of electric field, and in fact, because technical reason, commercial LC display is the polarity of inversion driving electric field continually usually.

On the contrary, bistable electro-optic displays as the impulse transducer, makes the end-state of pixel not only depend on electric field that is applied and the time that applies this electric field quite approx, but also depends on the electric field state of pixel before that applies.In addition, have been found that now, at least under the situation of many electro-optic displays based on particle, it is not necessarily constant that the equal variation (judging by eyes or by the normalized optical instrument) by gray shade scale changes the required impulse of given pixel, and they are also not necessarily switchable.For example, consider that each pixel wherein can show the display of preferably isolated gray shade scale 0 (white), 1,2 or 3 (black).(interval between these grades may be linear in by eyes or the number percent reflectivity by apparatus measures, but also can adopt other at interval.For example, at interval may in L* be linear (wherein L* has common CIE definition:

L*＝116(R/R ₀) ^1/3-16，

Wherein R is a reflectivity, and R ₀Be the standard reflectivity value), perhaps may be selected to provides specific gamma; Often adopt 2.2 gamma for monitor, and be used to replace under the situation of monitor at these displays, the use of similar gamma may meet demand.) have been found that pixel is changed into the required impulse of grade 1 (for simplicity following and be called " 0-1 transformation ") from grade 0 often to be changed required inequality with 1-2 or 2-3.In addition, to change required impulse not necessarily identical with the counter-rotating that 0-1 changes for 1-0.In addition, some system seems to show " memory " effect, makes whether change required impulse such as 0-1 is changing through 0-0-1,1-0-1 or 3-0-1 with specific pixel to a certain degree.(therein, wherein x, y and z are that representation " x-y-z " expression of

optical states

0,1,2 or 3 is that rank rear shows from arriving first, the sequence of the optical states that reaches successively in time.) though these problems can be by reducing all pixel drive of display the sufficient time section of required pixel drive before other state or solve to one of extremity, " flicker " of the pure color that is produced is unacceptable often; For example, the text that the reader of e-book may wish books rolls downwards along screen, if but display need glimmer continually ater or pure white, then may divert one's attention or can not find the position of reading last time.In addition, this flicker of display has increased its energy consumption, and may reduce the mission life of display.At last, have been found that, at least under some situation, the required impulse of special transition is subjected to the net cycle time of temperature and display and is subjected to specific pixel remained on the time in the particular optical state before given transformation influence, and is to guarantee that the accurate greyscale level reappears desirable to the compensation of these factors.

In addition, the argumentation by the front will be perfectly clear, and the driving of bistable state electric light medium requires to make and is not suitable for display based on bistable state electric light medium for the unmodified driver that drives active matrix liquid crystal display (AMLCD) design.But, this class AMLCD driver is that to have an available market of big allowable voltage scope and high number of pins encapsulation on sale, and it is cheap, make this class AMLCD driver attractive for driving bistable electro-optic displays, and be in fact more expensive, and relate to a large amount of designs and production time based on the similar driver of the display Custom Design of bistable state electric light medium.Therefore, revising the AMLCD driver so that have cost and development time advantage aspect being used with bistable electro-optic displays, the present invention manages to provide and makes the method that this purpose can realize and the driver of modification.

In addition, as mentioned above, the present invention relates to realize being applied to the driving impulse on the display long-term DC balance, be used for the method for drive cataphoresis display.Have been found that, encapsulation and other electrophoretic display device (EPD) need adopt the waveform of DC balance accurately (electric current that is any specific pixel of display should remain zero in the prolongation period of display work to the integration of time) to drive, so that maintenance picture steadiness, keep symmetrical commutativity, and the maximum useful mission life that display is provided.Be used to keep the classic method of accurate DC balance to require the precise voltage modulating driver of accurate stabilized voltage supply, gray level and be used for crystal oscillator regularly, and the regulation of these and similar assembly has greatly increased the cost of display.

(strictly speaking, the DC balance should consider that " inside " is measured under the suffered voltage condition of electro-optical medium itself.But, in fact, it is infeasible carrying out this class internal measurement in may comprising the display of working of thousands of pixels, and in fact, the voltage that the DC balance adopts " outside " to measure, promptly be applied on the electrode set on the opposite side of electro-optical medium is measured.Usually carry out two kinds of hypothesis when in addition, discussing the DC balance.At first usually, have the supposition of adequate cause ground, the conduction of electro-optical medium is not the function of polarity, makes when applying constant voltage, and pulse length is to follow the tracks of the proper method of DC balance.Secondly supposition, the conduction of electro-optical medium is proportional with a voltage that applies, and makes to utilize impulse to follow the tracks of the DC balance.)

Below term " superframe " is used for representing realizing that the whole necessary gray shade scale from the initial pictures to the final image changes the sequence of required continuous reading scan frame.Display update is only initiated when superframe begins usually.

Above-mentioned WO 03/044765 has described a kind of driving to have and can show that all at least three gray shade scales are (as the convention of field of display, in order to calculate the quantity of gray shade scale, extreme black and white state is counted as two gray shade scales) the method for bistable electro-optic displays of a plurality of pixels.The method comprises:

It is the look-up table of the data of the required impulse of final gray shade scale with initial grayscale transition that storage comprises expression;

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

Receive the input signal of the expection end-state of at least one pixel of representing display; And

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, this determines from look-up table.

For convenience's sake, this can be called " basic look-up table method " below method.

The quantity that depends on the original state of being stored, the look-up table that uses in the look-up table method may become very big.Lift an extreme example, think deeply employing and considered the algorithm of initial, final and two original states, be used for 256 (2 ⁸) look-up table method of gray shade scale display.Necessary four-dimensional look-up table has 2 ³²Individual clauses and subclauses.If each clauses and subclauses require (such as) 64 (8 byte), then the total big young pathbreaker of look-up table is approximately 32 GB.Do not bring problem though store this quantity data for desk-top computer, may in portable unit, go wrong.On the other hand, the invention provides a kind of method that is used to drive bistable electro-optic displays, it obtains and the similar result of look-up table method, but does not need to store great look-up table.

One aspect of the present invention relates to the part that is used to take to allow display drives bistable electro-optic displays in the mode of bit depth (the being different gray level grade quantity) work of the remainder that is different from display method and apparatus.From the description of Figure 11 A of above-mentioned WO 03/044765 and the described sawtooth driving method of 11B, those skilled in the art is perfectly clear, and it is obviously longer to have transformation between the consecutive image in the general pattern stream of bistable electro-optic displays of an a plurality of gray level grades transformation may drive with monochromatic mode than same display the time.Greyscale transitions can reach four times of the corresponding monochromatic length that changes usually.When display be used for presenting a series of images, for example during the continuous page of a series of photos or e-book, slower greyscale transitions is may not can unhappy.But, realize the fast updating of the limited area of this display, be useful sometimes.For example, the situation below considering: the user adopts this display to come the photo series of storing in the review database, so as to every photo input key word or after to be used to help from other index entry of database retrieval image.In this case, becoming and to allow between the serial-gram than slow-speed; For example, if user effort one to two minute every photo of research and determine index entry, then one to two second transformation can greatly not influence user's throughput rate between the serial-gram.But, attempted in anyone all very understandings with operation word processor on the computing machine of not enough processing power, when being updated in the dialog box of index entry of the input of explicit user wherein, one to two second delay makes the people very dejected, and may cause a large amount of typing errors.Therefore, under this and similar situation, advantageously can be with the monochromatic mode run dialog to allow fast transition, the remainder that continues simultaneously to move display with grey-scale modes the invention provides the method and apparatus that this purpose can be realized so that image can accurately reproduce.

Another aspect of the present invention relates to the method that need not voltage trim control and realize impulse is driven into the fine setting control of the gray shade scale that looks like medium.Though show, electrophoresis and some other electro-optic displays present bistability, but this bistability is not unconfined, and the slowly decay in time of the image on the display, if make that image will keep prolonging the period, then image may essential periodic refresh, so that image is returned to its optical states when being written at first.

But image this refreshes may cause it self problem.Described in above-mentioned U.S. Patent number 6531997 and 6504524, do not produce zero on the electro-optical medium or on average apply electric field if be used for the method for driving display near zero net time, then may encounter problems, and the mission life of display may reduce.The driving method that the zero net time of generation on average applies electric field on electro-optical medium is called " dc balance " or " DC balance " aptly.If image will keep prolonging the period by applying refresh pulse, then these pulses must have with produce the uneven drive scheme of DC, be used for the related pixel of display is driven into the identical polarity of addressing pulse of the optical states that is kept at first.

A difficult problem that realizes the accurate greyscale level grade in the impulse drive medium is to apply suitable voltage impulse so that obtain the gray tone of expection.The fine setting of the voltage that gratifying transformation can be by all or part of drive waveforms between the optical states is controlled and is realized.Needs for degree of accuracy can be understood from following example.Consider following situation: present image is made up of the screen of half black and half white, and the next image of expection is the even gray scale between black and white.In order to realize even gray shade scale, it is essential through trickle adjustment to be used for forwarding grey to and forwarding the impulse of grey to from white from black, makes the gray shade scale that obtains from black and gray shade scale coupling from white.If resulting final gray shade scale is the function of the previous gray shade scale history of demonstration, then further need fine setting.For example, as mentioned above, the optical states of being realized when black forwards grey to may be not only the function of the waveform that applies, and is the function of what state of being reached before current black state.Wish then to allow some aspect of display module tracing display history, as previous image state, and allow fine setting, so that compensate this previous state history (vide infra) to obtain more detailed argumentation about this respect to waveform.

The fine setting of impulse can by with the width of high precision pulse that adjustment is applied, only adopt three voltage levels (0 ,+V ,-V) realize.But this is undesirable for Active Matrix Display, because frame frequency must improve so that obtain high pulse width resolution may.High frame frequency increases the power consumption of display, and control and drive electronics are proposed higher requirement.Therefore, it is not desirable operating Active Matrix Display with the frame frequency that is much higher than 60-75Hz.

But the fine setting of impulse also can realize in the voltage time spent of a plurality of minute interval.In driven with active matrix, this requires the Source drive of exportable one of available many voltages set at least one subclass of voltage available.For example, for output-10 and+driver between the 10V, maybe advantageously, has available 0V, and-10 and-7V between and 7 and 10V between the voltage of two scopes, wherein have-10 with-7V between 16 different voltage levels and 7 and 10V between 16 different voltage levels, thereby make the sum of required voltage level reach 33 (referring to table 1).Then, for example by to last one or more scanning frames of addressing period+7 and+10V between or-10 and-change voltage between the 7V, can realize fine setting control to the optics end-state.This method is an example that is used to realize to accept the voltage modulated technology of display performance.

Table 1: voltage modulated drives the example of required voltage

-10.0V	-7.8V	8.0V
			-9.8V	-7.6V	8.2V
-9.6V	-7.4V	8.4V
			-9.4V	-7.2V	8.6V
-9.2V	-7.0V	8.8V

-9.0V	0.0V	9.0V
			-8.8V	7.0V	9.2V
-8.6V	7.2V	9.4V
			-8.4V	7.4V	9.6V
-8.2V	7.6V	9.8V
			-8.0V	7.8V	10.0V

Adopt the shortcoming of voltage modulated technology to be, driver must have the voltage trim control of certain scope.The display module cost can only provide the driver of two or three voltages to reduce by adopting.

In yet another aspect, the present invention manages to be provided for adopting the driver of the small set that only has voltage available to realize that method, the especially control at impulse of the fine setting control of gray shade scale can't realize can accepting under the situation of the required fine setting of display performance too roughly.Therefore, the method that need not voltage trim control and realize impulse is driven into the fine setting control of the gray shade scale that looks like medium is managed to provide in this aspect of the present invention.This aspect of the present invention for example can be applicable to have the Active Matrix Display that only can export the Source drive of two or three voltage.

In yet another aspect, the present invention relates to adopt the drive scheme that comprises at least some direct currents (DC) balance change to drive the method for electro-optic displays.Owing to the reason that describes in detail in the above-mentioned common pending application, when driving electro-optic displays, wish to adopt the DC balance, promptly have a drive scheme of following attribute: for any sequence of optical states, when final optical states matching initial optical states, the integration of the voltage that applies is zero.This clean DC imbalance that guarantees that electrooptic layer runs into is subjected to the restriction of given value.For example, 15V, 300ms pulse can be used for electrooptic layer is driven into black state from white.After this changed, imaging layer ran into the uneven impulse of DC of 4.5V-s.For film is driven into white again, if the pulse of use-15V, 300ms, then imaging layer from white to black and the transformation series that turns back to white list to the DC balance.

Also have been found that and wish to adopt wherein to this drive scheme of small part transformation as the DC balance; This class is called " DC balance change " below changing.The DC balance change does not have clean voltage impulse.Only adopt the drive scheme waveform of DC balance change after each changes, to keep the DC balance by electrooptic layer.For example ,-pulse of following 15V, 300ms after the pulse of 15V, 300ms can be used for electrooptic layer is driven into black from white.Clean voltage impulse on the electrooptic layer on this changes is zero.Can use then to follow after the pulse of 15V, 300ms-pulse of 15V, 300ms is driven into white again with electrooptic layer.Clean voltage impulse is again zero on this changes.

The drive scheme of being made up of all DC balance change unit must be the waveform of DC balance.Also may formulate a kind of DC balance drive scheme, it comprises DC balance change and the uneven transformation of DC, discusses in detail below.

In one aspect, the invention provides the method that drives the bistable electro-optic displays with a plurality of pixels, wherein each pixel can show at least three gray shade scales, and this method comprises:

Storage representation is used for the bucking voltage data of bucking voltage of each pixel of display, and the bucking voltage that is used for any pixel is calculated according at least one impulse that before had been applied to that pixel;

Produce the output signal of the expression pixel voltage to a described pixel to be applied, described pixel voltage is for from the initial and end-state of pixel and the determined driving voltage of look-up table and from the determined bucking voltage sum of the bucking voltage data that are used for pixel.

For convenience's sake, this is called " bucking voltage " of the present invention method below method.

In this bucking voltage method, the bucking voltage that is used for each pixel can be calculated according at least one of the gray shade scale original state of the time original state of pixel and pixel.In addition, the bucking voltage that is used for each pixel can be applied to the cycle of pixel and not have driving voltage to be applied in the hold period of pixel and all be applied to that pixel at driving voltage.

Because following detailed description needs employed bucking voltage in the regular update bucking voltage method of the present invention.The bucking voltage that is used for each pixel can (the required cycle of complete addressing of display) renewal during each superframe.The bucking voltage that is used for each pixel can be upgraded in the following manner: (1) adopt with relevant superframe during the fixedly algorithm that has nothing to do of the pulse that applies revise the preceding value of bucking voltage; And (2) will increase the determined amount of pulse that applies by during the relevant superframe from the value of step (1).In a preferred variants of this renewal process, the bucking voltage that is used for each pixel is upgraded in the following manner: (1) with the preceding value of bucking voltage divided by fixed constant; And (2) will from the value increase of step (1) in fact with the proportional amount of the total area under the voltage/time curve that is applied to electro-optical medium during the relevant superframe.

In bucking voltage method of the present invention, the form by exponential damping voltage that bucking voltage can be taked to apply when at least one driving pulse finishes applies.

The present invention also is provided for the device controller in this bucking voltage method.Described controller comprises:

Memory unit is arranged to store and is comprised expression initial grayscale transition is the data of the required pulse of final gray shade scale, represents the look-up table of data of original state of each pixel of display and the bucking voltage data that are used for each pixel of display at least;

Input block is used to receive the input signal of expection end-state of at least one pixel of expression display;

Calculating unit, be used for determining the original state of a described pixel is changed to the required driving voltage of expection end-state from the data and the look-up table of the original state of input signal, the described pixel of expression of being stored, this calculating unit also is identified for the bucking voltage of described pixel from the bucking voltage data that are used for described pixel, and driving voltage is determined pixel voltage mutually with bucking voltage; And

Output block is used to produce the output signal of representing described pixel voltage.

In sort controller, calculating unit can be arranged to determine bucking voltage according in the gray shade scale original state of the time original state of pixel and pixel at least one.In addition, output block also can be arranged in the cycle that driving voltage is applied to pixel and all pixel be applied bucking voltage there not being driving voltage to be applied in the hold period of pixel.

In addition, in sort controller, calculating unit upgrades the bucking voltage that is used for each pixel during can being arranged in each required superframe of the complete addressing of display.For this renewal, calculating unit can be arranged to upgrade the bucking voltage that is used for each pixel in the following manner: (1) adopt with relevant superframe during the fixedly algorithm that has nothing to do of the pulse that applies revise the preceding value of bucking voltage; And (2) will increase the determined amount of pulse that applies by during the relevant superframe from the value of step (1).In a preferred variants of this process, calculating unit is arranged to upgrade the bucking voltage that is used for each pixel in the following manner: (1) with the preceding value of bucking voltage divided by fixed constant; And (2) will from the value increase of step (1) in fact with the proportional amount of the total area under the voltage/time curve that is applied to electro-optical medium during the relevant superframe.

The form by exponential damping voltage that the output block of controller can be arranged to take to be applied when at least one driving pulse finishes applies bucking voltage.

In yet another aspect, the invention provides a kind of method that is used to upgrade bistable electro-optic displays, this bistable electro-optic displays comprises: be arranged in a plurality of pixels of many row and columns, make each pixel by the unique definition in the intersection of nominated bank and specify columns; And driver part, being used for applying electric field independently to change the show state of pixel to each pixel, each pixel has at least three kinds of different show states, and this method comprises:

Storage representation comprises the part of described display but is not the area data of whole institute's defined range;

For each pixel determine this pixel be within institute's defined range or outside;

Pixel in institute's defined range is used first drive scheme, and the pixel outside institute's defined range is used second drive scheme different with first drive scheme.

For convenience's sake, this is called " defined range " of the present invention method below method.

In this defined range method, the bit depth of first and second drive schemes may be different; Specifically, one of them may be monochromatic for first and second drive schemes, and another may be the gray level with at least four different gray shade scales.Institute's defined range can comprise and be used for text is input to text box on the display.

In yet another aspect, the invention provides the method that drives the bistable electro-optic displays with a plurality of pixels, wherein each pixel can show at least three gray shade scales, and this method comprises:

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, from look-up table, determine,

Wherein, at least one transformation from the original state to the end-state, output signal comprises the uneven fine setting of DC sequence, this sequence:

(a) has the clean impulse of non-zero;

(b) be discontinuous;

(c) cause the variation of the gray shade scale of pixel, this variation in fact with the variation different (differing more than 50% usually) of the optical states of its DC reference pulse, wherein the DC reference pulse is voltage V ₀Pulse, V wherein ₀Be to finely tune the maximum voltage that is applied during the sequence, but have and finely tune the identical symbol of clean impulse G of sequence, and the duration of reference pulse is G/V ₀And

(d) cause the variation of the gray shade scale of pixel, the variation of the gray shade scale that its amplitude is caused less than its time reference pulse (usually less than it half), wherein the time reference pulse is defined as and the unipolar voltage pulse of finely tuning the identical duration of sequence, but wherein the symbol of reference pulse is the symbol of bigger variation that gray shade scale is provided.

For convenience's sake, this method (and following defined similar approach) is following can be called " discontinuous addressing " of the present invention method; When needs were distinguished two kinds of methods, they can be called " the uneven discontinuous addressing of DC " method and " the discontinuous addressing of DC balance " method respectively.

In a preferred form of this discontinuous addressing method, the fine setting sequence causes the variation of the gray shade scale of pixel, half of the variation of the gray shade scale that it is caused less than its time reference pulse.

The present invention also provides the method that drives the bistable electro-optic displays with a plurality of pixels, and wherein each pixel can show at least three gray shade scales, and this method comprises:

Wherein, at least one transformation from the original state to the end-state, output signal comprises DC balance fine setting sequence, this sequence:

(a) have and be essentially zero clean impulse; And

(b) can be at any point of fine setting sequence, the gray shade scale that makes pixel differs the about more than 1/3rd of gray shade scale difference between two extreme optical state of pixel with it finely tuning gray shade scale that sequence begins to locate.

In two kinds of variants of discontinuous addressing method of the present invention, output signal also comprises at least one one pole driving pulse usually except the fine setting sequence.Discontinuous output signal may be acyclic.Change for the major part in the look-up table, output signal can have the clean impulse of non-zero and may be discontinuous.In at least one that adopts discontinuous output signal changes, output signal may be only by have voltage level+V, 0 and-pulse of V constitutes, preferably only by have voltage level 0 and+V and-one of them pulse of V constitutes.In a preferred variants of this method, for at least one transformation of adopting discontinuous output signal, and preferably for most of transformation the in the initial different look-up table of pixel with end-state, output signal by the pulse with voltage level 0 with and the having of front and back+V and-V at least two pulses of same voltage level constitute.Indicator is the DC balance preferably.In addition, change at least one that adopts discontinuous output signal, output signal can be made of a series of pulses as the integral multiple of monospace.

Discontinuous addressing method of the present invention also can comprise the data of at least one gray shade scale original state of at least one the time original state of the described pixel of storage representation and/or a described pixel, and produces output signal according to described at least one time original state and/or at least one gray shade scale original state of a described pixel.

The present invention also provides a kind of driving to have the method for the bistable electro-optic displays of a plurality of pixels, wherein each pixel can show at least three kinds of gray shade scales, this method comprises that each pixel to display applies the output signal of effectively pixel being changed into end-state from original state, wherein, at least one different with end-state changes for the original state of pixel, output signal by the having of pulse with voltage level 0 and front and back thereof+V and-at least two pulses of same voltage level constitute among the V.

In yet another aspect, the invention provides the method that a kind of driving has the bistable electro-optic displays of a plurality of pixels, wherein each pixel can show at least three kinds of gray shade scales, this method comprises that each pixel to display applies the output signal of effectively pixel being changed into end-state from original state, wherein change at least one, output signal is non-zero but DC balance.

For convenience's sake, this is called " addressing of DC balance " of the present invention method below method.

In this DC balance addressing method, at least one transformation, output signal can comprise first paired pulses, comprising the equal length of potential pulse and front thereof but the pulse of contrary sign.Perhaps, output signal also can comprise two no-voltage cycles between the pulse, and at least one in the pulse can be interrupted by the no-voltage cycle.Output signal also can comprise equal length but second paired pulses of contrary sign; Second paired pulses can have the length different with first paired pulses.In second paired pulses first have with first paired pulses in first opposite polarity.First paired pulses can appear in second paired pulses first and between second.

In addition, in this DC balance addressing method, for above-mentioned transformation, output signal can comprise at least one the pulse element that effectively pixel is driven in fact in the optics railing (rail).

Discuss in more detail below, DC balance addressing method of the present invention can utilize DC balance and the uneven combination that changes of DC.For example, change for initial identical with end-state each of pixel, output signal can be non-zero but DC balance, and for the initial of pixel and each transformation that end-state is inequality, output signal can not be the DC balance.In this addressing method, for each transformation inequality of the initial and end-state of pixel, output signal can have-form of x/ Δ IP/x, wherein, Δ IP is the impulse potential difference between the initial and end-state of pixel, and-x and x are equal length but a paired pulses of contrary sign.

DC balance addressing method of the present invention also can comprise:

It is the look-up table of the data of the required impulse of final gray shade scale with the initial grayscale transition of pixel that storage comprises expression;

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, from look-up table, determine.

The method that the present invention also provides a kind of driving to have the bistable electro-optic displays of at least one pixel, it comprises to pixel and applies waveform V (t), makes:

J = {&Integral;}_{0}^{T} V (t) M (T - t) dt - - - (1)

(wherein, T is the length of waveform, integration is to carry out on the duration of waveform, V (t) is the waveform voltage as the function of time t, and M (t) characterizes the memory function cause in the reduction of the effect of the residual voltage of time zero residence time correlativity that produces from short pulse of place) less than about 1 weber.For convenience's sake, this is called " the DTD integration reduces " of the present invention method below method.Comparatively ideally be, J is less than about 0.5 weber, and it would be desirable less than about 0.1 weber.In fact, J should be arranged to as far as possible little, and ideal situation is zero.

In a preferred form of this method, J is calculated by following formula:

J = {&Integral;}_{0}^{T} V (t) \exp (- \frac{T - t}{τ}) dt - - - (2)

Wherein, τ is decay (relaxing) time, and it preferably has from about 0.7 to about 1.3 seconds value.

Figure 1A-1E represents can be used for five waveforms of discontinuous addressing method of the present invention.

Fig. 2 illustrates at the various frame numbers that adopt unipolar voltage the problem in the electro-optic displays addressing.

Fig. 3 illustrates a kind of mode that adopts discontinuous addressing method of the present invention to solve problem shown in Figure 2.

Fig. 4 illustrates the second way that adopts discontinuous addressing method of the present invention to solve problem shown in Figure 13.

Fig. 5 explanation can be used for the waveform of discontinuous addressing method of the present invention.

Fig. 6 explanation can be made amendment according to the present invention to produce the basic waveform of waveform shown in Figure 5.

Fig. 7 explanation adopts the various frame numbers of unipolar voltage to the problem in the electro-optic displays addressing when keeping the DC balance.

Fig. 8 illustrates a kind of mode that adopts discontinuous addressing method of the present invention to solve problem shown in Figure 7.

Fig. 9 illustrates the second way that adopts discontinuous addressing method of the present invention to solve problem shown in Figure 7.

The gray shade scale that Figure 10 explanation does not adopt discontinuous addressing method of the present invention to obtain in four gray shade scale electro-optic displays in nominal.

Figure 11 illustrates the gray shade scale that adopts various discontinuous addressing sequences to obtain from the display identical with Figure 10.

Figure 12 explanation discontinuous addressing method according to the present invention adopts has revised the gray shade scale that drive scheme obtains from the display identical with Figure 10.

Figure 13 explanation can be used to drive the simple DC balanced waveform of electro-optic displays.

Figure 14 and Figure 15 have been illustrated as two kinds of modifications waveform shown in Figure 24 being carried out in conjunction with the no-voltage cycle.

How Figure 16 illustrative revises waveform shown in Figure 13 so that comprise that another is to driving pulse.

Figure 17 explanation is by revising the waveform that waveform was produced of Figure 13 in mode shown in Figure 16.

Figure 18 explanation is by revising second waveform that waveform was produced of Figure 24 in mode shown in Figure 27.

How waveform shown in Figure 19 illustrative Figure 18 is through further revising so that comprise the 3rd pair of driving pulse.

Figure 20 explanation is by revising the waveform that waveform was produced of Figure 18 in mode shown in Figure 19.

Figure 21 illustrates that one can be used in combination with the DC balanced waveform so that the uneven waveform of the preferred DC of employed complete look-up table in the method for the present invention to be provided.

Figure 22 is a chart, the residence time correlativity of the reduction that explanation can realize by bucking voltage method of the present invention.

Figure 23 is a chart, and the effect of the residence time correlativity in the electro-optic displays is described.

Can clearly know from the front, the invention provides in driving the method for electro-optic displays and in the equipment controller of carrying out this class driving method or a large amount of different improvement in other equipment. In the following description, various different improvement provided by the present invention are described usually independently, but the technical staff of imaging field will appreciate that in fact individual monitor can utilize an above aspect in these main aspects; For example, adopt the display of discontinuous addressing method of the present invention also can utilize the defined range method.

Seem that at first the Perfected process that impulse is driven the electro-optic displays addressing is so-called " general grayscale image stream ", its middle controller arranges at every turn writing of image, so that each pixel directly is converted to its final gray scale grade from its initial gray scale grade. But, have inevitably certain error when image is write impulse driving display. Mention such as part, this class error of some that in fact run into comprises:

(a) original state correlation; Not only depend on initial and expection optical states to the required impulse of new optical states pixel transitions, but also depend on the previous optical states of pixel.

(b) time of staying correlation; Pixel transitions is depended on the time that pixel has consumed to the required impulse of new optical states in its each optical states. The precise nature of this kind correlation is understood not yet fully, but in general, pixel stops more long in its current optical states, then requires bigger impulse.

(c) temperature dependency; Pixel transitions is depended on temperature to a great extent to the required impulse of new optical states.

(d) humidity correlation; For the electro-optical medium of at least a portion type, pixel transitions is depended on ambient humidity to the required impulse of new optical states.

(e) mechanical uniformity; With pixel transitions to the machinery that the required impulse of new optical states may be subjected to display change, the impact of the variation of the thickness of for example electro-optical medium or associated lamination adhesive. The difference that the mechanical inhomogeneities of other type may result from medium makes batch, make between tolerance and the changes in material and inevitably change.

(f) voltage error; The actual impulse that is applied to pixel will inevitably be slightly different from the impulse that applies in theory owing to inevitable fine error in the voltage of driver transmission.

General grayscale image stream suffers from " error accumulation " phenomenon. For example, the imagination temperature dependency on each changes just to producing the 0.2L* error. After five ten conversions, this error will accumulate 10L*. Suppose, take the average error of each represented transformation of the difference between the theory and practice reflectivity of display as ± 0.2L* perhaps actually. After 100 change continuously, pixel will show and their average deviation of expectation state 2L*; This class deviation does not generally watch the person fairly obvious for the image of some type.

This kind error accumulation phenomenon not only is applicable to Yin Wendu and the error that produces, but also is adapted to the error of other type. Compensation to this class error is feasible, but only reaches limited levels of precision. For example, the temperature error can compensate by adopting temperature sensor and look-up table, but the temperature sensor has limited resolution ratio, and may read the temperature slightly different from electro-optical medium. Similarly, the original state correlation can and adopt the multidimensional transition matrix to compensate by the storage original state, but the controller memory limitations quantity of the state that can record and the size of the transition matrix that can store, thereby the accuracy of such compensation has been applied restriction, as mentioned above.

Therefore, general grayscale image stream requires the extremely accurately control that applies impulse so that good result to be provided, and has been found that on the present level of electro-optic displays technology according to experience, and it is infeasible that general grayscale image circulation is everlasting in the commercial display.

Nearly all electro-optical medium all has built-in replacement (error limitation) mechanism, is its extreme (being generally black and white) optical states that they are as " optics railing ". After specific impulse has been applied to the pixel of electro-optic displays, that pixel can't become whiter (or more black). For example, in encapsulated electrophoretic display, after specific impulse had applied, all electrophoretic particles mutually pushed or are expressed on the capsule wall, can't move again, thereby produce limited optical states or optics railing. Owing in this kind medium, have electrophoretic particles size and charge distribution, therefore some particles arrived railing before other particles, set up " soft railing " phenomenon, thereby at the final optical states that changes during near extreme black and white states, required impulse precision is reduced, and sharply increases near the transformation that required optical accuracy finishes the optical range middle part of pixel. Obviously, general pure grayscale image stream drive scheme can't rely on and adopt the optics railing to prevent error in the gray scale grade, because in this kind drive scheme, any given pixel may experience the variation of the infinitely great number of times in the gray scale grade in the situation that does not touch any optics railing.

Described in above-mentioned U.S. Patent number 6504524 and 6531997, in many electro-optical mediums, especially in the electrophoretic medium based on particle, should be zero or approach as far as possible on zero the meaning in the algebraical sum of the electric current by specific pixel on the prolongation cycle, the drive scheme that wish to be used for drives this class medium is direct current (DC) balance, and drive scheme of the present invention will consider that this standard designs. More particularly, look-up table should be through design, so that any sequence of the transformation that begins in the extreme optical state (black or white) of pixel and finish should be the DC balance. May it seems at first that from the above this kind DC balance possibly can't realize because any specific gray scale to the required impulse that passes through pixel of transition in grayscale and thereby electric current be in fact constant. But, this only is so quite approximately, and have been found that according to experience, at least in the situation based on the electrophoretic medium of particle (and also be like this for other electro-optical medium situation), (such as) the effect of pulse from 50 milliseconds at five intervals to pixel that apply is not identical with 250 milliseconds of pulses that apply identical voltage. Therefore, have certain flexibility by pixel in the electric current of realizing given transformation, and this kind flexibility can be used to help to realize the DC balance. For example, the look-up table that the present invention uses can be provided by the value for each total current that provides of a plurality of impulses of given transformation and these impulses, and for each pixel, controller can keep being configured to the register of the algebraical sum of storage has been applied to pixel since certain previous time (for example being in black state from the pixel last time) impulse. When specific pixel will be driven into black state from white or gray states, controller can check the register related with that pixel, determine to carry out the required electric current of DC balance for the whole sequence of the transformation from previous black state to the black state that is about to occur, and select to be used for required white/grey to black change a plurality of store impulse one of them, it will accurately be reduced to associated registers zero or be reduced at least as far as possible little remainder (in this case, associated registers will keep the value of this remainder, and it is added in the electric current that applies during the later on transformation). Everybody is clear, and the repeatedly application of this process can realize the accurately long-term DC balance of each pixel.

Below to various aspects of the present invention discussion will be supposed complete content, the particularly various waveform disclosed herein of being familiar with above-mentioned WO03/044765. The technical staff of field of display will appreciate that various methods of the present invention can be through revising the various optional feature (such as temperature-compensating, work life-span compensation, humidity compensate etc.) to comprise the basic LUT Method described in the above-mentioned WO03/044765. Various method of the present invention also can utilize being used for described in the above-mentioned WO03/044765 reduce to be the method for the data amount of look-up table stores. In addition, can regard general cube as owing to comprise the data of look-up table, therefore, known to the skilled any canonical function, algorithm and the coding in data Storage and Processing field all can be used to reduce following one or more aspect: (a) the required memory block size of data set, (b) extract the required evaluation work of data, perhaps (c) searches and extracts the required time of element-specific from data centralization. These memory technologies comprise for example hash function, harmless and lossy compression method and the substantially expression of the data set of combination of function of conduct.

Discontinuous addressing method

The vernier control of the gray scale level grade in the method for the present invention can be realized by adopting discontinuous addressing method of the present invention. As mentioned above, discontinuous addressing method has two main variants, i.e. the uneven variant of DC and DC balance variant. The output signal that the uneven variant employing of DC has non-zero net impulse (length that is the positive and negative section is unequal) is carried out at least one transformation between the gray scale grade, therefore not the internal DC balance, and be discontinuous (being the part that pulse comprises no-voltage or phase reversed polarity). The output signal of using in the discontinuous addressing method may be or may not be acyclic (namely may be or may not be by such as+/-/+/-or ++ the repetition cell formation /--/++/--).

The discontinuous waveform of this kind (following being called " fine setting " or " FT " waveform) may not have the frame of phase reversed polarity for effective frontal plane voltage of display, and/or may only comprise three voltage level+V, 0 and-V is (as normal conditions, suppose the common front-end electrode that has the pixel electrode related with each pixel and extend in a plurality of pixels the Active Matrix LCD At device, be generally whole display, the electric field that therefore is applied to any pixel of electro-optical medium is determined by the voltage difference between its associated pixel electrode and the common front-end electrode). Perhaps, the FT waveform can comprise more than three voltage levels. The FT waveform can comprise any (such as n-prepulse etc.) of above-mentioned type of waveform, has wherein added discontinuous waveform.

The FT waveform may (and usually meeting) depend on one or more previous image states, and can be used so that the littler change in optical state that realizes can realizing than employing standard pulsewidth modulation (PWM) technology. (therefore, and for example be said to be some that prevent that electrophoretic particles is bonded to the pulse of adopting polarity alternately such as the surface of capsule wall and so on and have earlier the technology waveform to compare, the accurate FT waveform that adopts is different for each transformation in look-up table. ) in a preferred variants of discontinuous addressing method, the combination of all required waveforms of the possible optical transitions (" transition matrix ") that realizes all permissions in the display is provided, wherein at least one waveform is FT waveform of the present invention, and the combination of waveform is the DC balance. In another preferred variants of discontinuous addressing method, the length of all voltage sections is the monospace integral multiple of (" frame time "); The voltage section is that voltage keeps constant waveform portion.

Discontinuous addressing method of the present invention is based on following discovery: drive in the electro-optical mediums at many impulses, in fact the waveform of overall variation that has zero clean impulse thereby may estimate in theory not cause the gray scale grade of pixel may cause the little variation of gray scale grade owing to some nonlinear effect in the attribute of this class medium, with adopt simple PWM drive scheme or have the width that changes pulse and/or situation that the driver of the limited capability of height may be realized is compared, it can be used to realize the more intense adjustment to the gray scale grade. The pulse that can reach so a kind of " fine setting " waveform can separate with " the main driving " pulse of the Main change that causes the gray scale grade, and can be before or after the main driving pulse of this class. Perhaps, in the part situation, the intense adjustment pulse can mix with main driving pulse, or the autonomous block of the fine setting pulse on a single point in the sequence of main driving pulse, perhaps scatters separately on a plurality of points in the sequence of main driving pulse or is divided into group.

Although discontinuous addressing method has very general applicability, but main utilize the drive scheme of the waveform that adopts Source drive with three Voltage-outputs (positive and negative and zero) and consisted of by the waveform elements of following three types to describe as an example (owing to we think, necessity modification of the present invention being carried out in order to be used with the driver of other type and waveform elements is extremely obvious for the those skilled in the art of electro-optic displays):

1) saturation pulse: the frame sequence with voltage of a symbol or symbol and zero volt, reflectivity is driven near an extreme optical state (optics railing, perhaps for being referred to herein as the darkest state of black state, perhaps for being referred to herein as the brightest state of white states);

2) pulse is set: have the frame sequence of the voltage of a symbol or symbol and zero volt, reflectivity is driven into approaches expection gray scale grade (black, white or middle gray grade); And

FT sequence: have the frame sequence of the voltage that is chosen as separately positive and negative or zero, so that the optical states of ink moves much smaller than single symbol sebolic addressing of equal length. The example of FT drive sequences with total length of five scanning frames is: [+-+--] (here, the voltage of each frame is successively expression in such a way :+represent positive voltage, 0 expression no-voltage, and-the expression negative voltage), [--0++], [0 000 0], [0 0+-0], and [0-+0 0]. These sequences schematically illustrate in Figure 1A-1E of accompanying drawing respectively, and wherein, circle represents the starting and ending point of FT sequence, and five scanning frames are arranged between these points.

The FT sequence can be used for allowing the vernier control of optical states as mentioned above, perhaps produces similar from the situation of one pole (single symbol) contact potential series but has the variation of the optical states of different clean voltage impulse (impulse wherein be defined as the voltage that applies to the integration of time). Thereby the FT sequence in the waveform can be used as the instrument of realizing the DC balance.

At first description is used for realizing the use of FT sequence of the vernier control of optical states. Among Fig. 2, can adopt unipolar voltage zero, one, two, three frames or more the optical states realized of multiframe schematically illustrate and be the point on the reflectivity axle. See that from this figure the length of unipolar pulse may be selected to and realizes by the represented reflectivity of its respective point on this axle. But, may wish to realize the gray scale grade shown in " target " among Fig. 2 for example, it can't suitably be similar to by any of these gray scale grades. The FT sequence can be used for reflectivity is fine-tuning to expecting state, its mode or the end-state that after the one pole driving pulse, obtains by fine setting, or by fine setting original state and then use one pole drive sequences.

As shown in Figure 3, first case representation of FT sequence employed FT sequence after the dipulse one pole drives. The FT sequence is used for final optical states is fine-tuning to the target state. Similar to Fig. 2, Fig. 3 represents to adopt the optical states of various scanning frame numbers realizations, shown in solid dot. Also represented the objective optics state. Represented by applying the optical change of two scanning frames, as the optics skew that is caused by the FT sequence.

Second example of FT sequence as shown in Figure 4; In this case, the FT sequence is used for that at first optical states is fine-tuning to the one pole drive sequences and can be used to realize to expect the position of optical states. The optical states that can realize after the FT sequence is represented by the empty circles among Fig. 4.

The FT sequence also can be stablized gray scale level (RSGS) waveform with railing and be used, for example shown in Figure 11 A and 11B of above-mentioned WO 03/044765. The essence of RSGS waveform is that given pixel only was allowed to carry out the gray scale of limited number of times to transition in grayscale before being driven to one of its extreme optical state. Therefore, this class waveform utilization frequently is driven into extreme optical state (being called the optics railing) and reduces the optics error, keeps simultaneously DC balance (wherein the DC balance is the clean voltage impulse for zero, is described in more detail below). By selecting to be used for the intense adjustment voltage of one or more scanning frames, the gray scale level of suitably differentiating can adopt these waveforms to realize. But, if these intense adjustment voltages are unavailable, then must adopt another kind method to realize fine setting, preferably also keep simultaneously the DC balance. The FT sequence can be used to realize these purposes.

At first, consider that railing stablize the circulation form of gray scale level waveform, wherein each changes by zero, one or two saturation pulse (with the pulse of pixel driver to the optics railing) and the pulse (pixel is reached expect gray scale grade) that arranges as mentioned above of following thereafter form. In order to illustrate that how the FT sequence can be used for this waveform, symbolic notation will be for waveform elements: " sat " represents saturation pulse; " set " expression arranges pulse; And " N " expression FT drive sequences. The circulation railing of three basic forms of it is stablized gray scale level waveform:

Set (for example transformation 1104 among Figure 11 A of WO 03/044765)

Sat-set (for example transformation 1106/1108 among Figure 11 A of WO 03/044765)

Sat-sat '-set (for example transformation 1116/1118/1120 among Figure 11 A of WO 03/044765)

Wherein, sat is two different saturation pulse with sat '.

Adopt the FT sequence that first kind modification in these types is provided following waveform:

N-set

set-N

That is, follow the identical element that pulse or opposite order are set after the FT sequence.

Adopt one or more FT sequences that the modification of the second in these types is revised rear waveform as providing following FT:

N-sat-set

sat-N-set

sat-set-N

sat-N-set-N’

N-sat-set-N’

N-sat-N’-set

N-sat-N’-set-N”

Wherein, N, N ' and N " be three FT sequences, they may be or may not be mutual differences.

Second modification in these types can be by scattering the FT sequence between according to three waveform elements of form noted earlier and realize main. The incomplete tabulation of example comprises:

N-sat-sat’-set

N-sat-sat’-set-N’

sat-N-sat’-N’-set-N”

N-sat-N’-sat’-N”-set-N”’

Another basic waveform that can adopt the FT sequence to revise is to have the pulse lantern slide gray scale level that is driven into black (or white). In this waveform, at first make optical states arrive the optics railing, arrive then the expection image. The waveform of each transformation can be represented in the symbol mode by in two sequences any:

sat-set

set。

This kind waveform can by with basically with stablize the described identical mode of gray scale sequence for railing and comprise FT drive sequences unit and usually revise, thereby produce following sequence:

sat-set-N

sat-N-set

Etc..

More than two examples be described in the saturated of waveform and the insertion of the FT sequence before or after the pulse element be set. Maybe advantageously, saturated or arrange and insert the FT sequence in the middle of the pulse, that is, and basic sequence:

sat-set

To be modified and for example form:

{ sat, part I}-N-{sat, part II}-set

Perhaps

Sat-{set, part I}-N-{set, part II}

As mentioned above, have been found that, the optical states of many electro-optical mediums of after a series of transformations, realizing to previous optical states and in those previous optical states consume time-sensitive, and for transition waveforms compensates original state and previous residence time sensitive degree has been described certain methods by correspondingly adjusting. The FT sequence can be used for compensating previous optical states and/or the previous time of staying by similar fashion.

In order to describe this concept more detailedly, the sequence of the gray scale grade that consideration will represent in specific pixel; These grades are denoted as R₁、R ₂、R ₃、R ₄Etc., wherein, R₁Next one expection (finally) gray scale grade of the transformation that expression is considered, R₂The initial gray scale grade of that transformation, R₃The first previous gray scale grade, R₄The second previous gray scale grade, etc. The gray scale rate sequence then can be expressed as:

R _nR _n-1R _n-2...R ₃R ₂R ₁

The time of staying before the gray scale grade i is expressed as D_i。D _iCan be illustrated in the quantity of the frame scan that stops among the gray scale grade i.

Above-described FT sequence can be selected as being fit to from current to expecting the transformation of gray scale grade. In the simplest form, these FT sequences then are current and the function of expection gray scale grade, such as symbolic representation are:

N＝N(R ₂，R ₁)

Thereby show that FT sequence N depends on R₂And R₁。

For the performance that improves equipment, particularly reduce to be offset with the residual gray scale grade of previous image correlation, it is favourable that transition waveforms is carried out little adjustment. The selection of FT sequence can be used to realize these adjustment. The various final optical states of various FT sequence generations. Can select different FT sequences for the different optical history of given pixel. For example, in order to compensate the first previous image (R₃), optional selecting depended on R₃The FT sequence, be expressed as:

N＝N(R ₃，R ₂，R ₁)

That is, the FT sequence not only can be according to R₁And R₂Select, and can be according to R₃Select.

Make this concept vague generalization, can make the FT sequence depend on the previous gray scale grade of any amount and/or depend on previous time of staying of any amount, such as symbolic representation be:

N＝N(D _m，D _m-1，...D ₃，D ₂；R _n，R _n-1，...R ₃，R ₂，R ₁)

Wherein, symbol D_kBe illustrated in gray scale grade R_kThe middle time of staying of consuming, and the quantity n of optical states does not need to equal the quantity m that FT determines the time of staying required in the function. Therefore, the FT sequence can be previous image and/or the function that had before reached the current gray level grade time of staying.

As the special case of this general concept, have been found that no-voltage scanning frame can change resulting final optical states to the insertion of other unipolar pulse. For example, inserted therein the optical states that obtains after the sequence of no-voltage scanning frame, Fig. 5 will from do not have no-voltage scanning frame but to have an optical states that obtains after the corresponding one pole sequence of total impulse identical with the sequence of Fig. 5, Fig. 6 slightly different.

Have been found that also given pulse depends on the length of the time-delay between this pulse and the front pulse to the impact of final optical states. Therefore, the no-voltage frame can be inserted between the pulse element to realize the fine setting of waveform.

The present invention expands to the insertion of the use of FT driving element and zero volt scanning frame in the one pole driving element of other waveform configuration.Other example includes but not limited to therein two kinds of optics railings two prepulses (comprising three prepulses, four prepulses etc.) lantern slide gray level waveform of accessed from a kind of optical states to alternative process (surpassing once) under the situation of the prepulse of higher quantity, and the railing of other form is stablized the gray level waveform.The FT sequence also can be used for general pattern stream gray level waveform, wherein directly changes between gray shade scale.

Though the insertion of no-voltage frame can be considered to the special case that the FT sequence is inserted, be that these special circumstances arouse attention under zero the situation entirely in the FT sequence, be effective because have been found that it revising aspect the final optical states.

The above concentrates on the fine setting of using the FT sequence to realize gray shade scale.To consider to use this class FT sequence to realize the DC balance now.The FT sequence can be used to change the uneven degree of DC in the waveform (preferably reduce or eliminate DC imbalance).The DC balance means that all whole circuit gray shade scale sequences (sequence that begins and finish with the same grayscale grade) have zero clean voltage impulse.By using one or more FT sequences, can make waveform DC balance or DC imbalance not too consumingly, utilize following true: the FT sequence can or (a) with saturated or be provided with pulsion phase with mode but adopt the clean voltage impulse that is different in essence to change optical states; Perhaps (b) produces the non-substantial variations of optical states but has clean DC imbalance.

Below how explanation expression FT sequence can be used to realize the DC balance.In this example, it can be variable-length that pulse is set, promptly one, two, three or more scanning frames.For the final gray shade scale that each was realized in the scanning frame quantity as shown in Figure 7, wherein the numbering on each some next door represents to be used for to realize the quantity of the scanning frame of gray shade scale.

The available optical states of scanning frame that Fig. 7 represents to adopt positive voltage, one pole to drive, number designation are wherein specified the quantity of the one pole frame that is used for producing final gray shade scale.Suppose in this example and need apply the clean voltage impulse of two positive voltage frames in order to keep the DC balance.Expection (target) gray shade scale can realize by three scanning frames that adopt impulse; But when carrying out this operation, system will keep the DC imbalance by a frame.On the contrary, the DC balance can realize by adopting two positive voltage scanning frames rather than three, but final optical states will be very big with target deviation.

A kind of mode that realizes the DC balance is to adopt two positive voltage frames that electro-optical medium is driven near the expection gray shade scale, and adopt DC balance FT sequence (FT sequence) to make final adjustment fully near the target gray shade scale with zero clean voltage impulse, as symbolic representation among Fig. 8, wherein, the target gray shade scale adopts the FT sequence of the zero clean voltage impulse of following the suitable variation that is chosen to provide optical states after two scanning frames to realize.

Three positive voltage scanning frames that perhaps can adopt one pole to drive make reflectivity reach the objective optics state, adopt then to have the unbalanced FT sequence of the clean DC that is equivalent to a negative voltage scanning frame.If select to produce the FT sequence of unconverted in fact optical states, then final optical states will keep correctly, and the DC balance will be resumed.This example as shown in Figure 9.Everybody will appreciate that, the use of FT sequence will be referred to certain adjustment of optical states and usually to certain influence of DC balance, and above two examples explanation extreme case.

Only the mode of explanation provides following example by way of example, so that explanation is according to the experiment utilization of FT sequence of the present invention.

Example: the use of the FT sequence in circulation RSGS waveform

The use of the FT sequence of this example explanation when the optical property of the designed waveform of 4 gray shade scales (2) addressing that is improved to the single pixel display of realization.This display adopts encapsulated electrophoretic medium, and constructs according to above-mentioned 2002/0180687 the described mode of [0069] to [0076] section in fact.Single pixel display is monitored by photodiode.

Waveform voltage is applied to pixel according to transition matrix (look-up table), so that realize the sequence of 2 gray shade scales in (4 state) gray level.As mentioned above, transition matrix or look-up table just are used for voltage is applied to pixel so that carry out one group of rule from gray shade scale in the gray level to another transformation.

Waveform is subjected to voltage and regularly restriction.Have only three voltage level-15V, 0V and+15V is applied on the pixel.In addition, in order to simulate the driven with active matrix with 50Hz frame frequency, voltage applies with the 20ms increment.Tuning algorithm is used iteratively, so that optimized waveform, promptly realizes being minimum condition for the dispersion degree in each the actual optical state of four gray shade scales on the cycle tests.

In initial experiment, the circulation railing is stablized gray level (cRSGS) waveform and is adopted simple saturated and pulse optimization is set.The consideration of original state is limited to initial (R when determining transition matrix ₂) and the expection final (R ₁) gray shade scale.Waveform is overall DC balance.Owing to R in rough property (15V, 20ms) that can be used for tuning minimum impulse and the transition matrix ₂Lacking of state before, the performance that expection is on duty mutually from this waveform.

The performance of transition matrix is tested by " complete five-tuple " the gray shade scale sequence conversion testing pixel via all gray shade scale five-tuple sequences that comprise random arrangement.(the five-tuple sequential element is the sequence of five gray shade scales, for example 0-1-0-2-3 and 2-1-3-0-3, wherein four available gray shade scales of 0,1,2 and 3 expressions.) for perfect transition matrix, the reflectivity of each is identical for whole appearance of that gray shade scale in the random series in four gray shade scales.The reflectivity of each will be obviously different for the actual transition matrix in the gray shade scale.In fact the bar chart of Figure 10 represents the bad performance of the transition matrix of voltage and timing restriction.The measured reflectivity of the various appearance of each is very different in the target gray shade scale.Be called basic waveform below the cRSGS waveform of in this part of experiment, developing that does not have the FT sequence to be optimized.

Then, the FT sequence is added into the cRSGS waveform; In this experiment, the FT sequence is restricted to five scanning frames, and only comprises DC balance FT sequence.The FT sequence is arranged on the end of the basic waveform that is used for each transformation, that is, the waveform that is used for each transformation has one of following form:

set-N

sat-set-N

sat-sat’-set-N

The FT sequential element requires two steps to the successful combination in the waveform; The first, determine of the effect of various FT sequences to the optical states of each gray shade scale, the second, selection appends to the FT sequence of various waveform elements.

In order to determine of the effect of various FT sequences, carry out " FT effect " experiment to the optical states of each gray shade scale.At first, set up consistent starting point by between black and white optics railing, changing electrophoretic medium repeatedly.Then, film is set to one of four gray shade scales (0,1,2 or 3), is called optical states R here ₂Subsequently, apply and be fit to carry out from R ₂(be called R here to one of other gray shade scale ₁) transformation, have the basic waveform of additional FT sequence.This step adopts 5 frame FT sequences of whole 51 DC balances to carry out repeatedly.For the final optical states of each FT sequential recording.The FT sequence then sorts according to the final reflectivity of its association.This process is for initial (R ₂) and final (R ₁) all combinations of gray shade scale carry out repeatedly.Final gray shade scale 1 (R ₁=1) and current gray level grade 0,2 and 3 (R ₂Shown in table 2-4, the tabulation that wherein is labeled as " frame 1 " to " frame 5 " is shown in the current potential of unit for lying prostrate that is applied during five successive frames of relevant FT sequence respectively in the ordering of FT sequence=0,2,3).The final optical states of realizing for the waveform that adopts various FT sequences as shown in Figure 11.See that from this figure the FT sequence can be used to realize the big variation of final optical states, and the selection of five scanning frame FT sequences provides for the fine setting of final optical states control, all do not have clean voltage impulse poor.

Table 2: the final optical states of the gray shade scale 0 to 1 of various FT sequences.

Table 3: the final optical states of the gray shade scale 2 to 1 of various FT sequences.

Call number	Optics (L*)	Frame 1	Frame 2	Frame 3	Frame 4	Frame 5
							1	34.85	0	15	15	-15	-15
2	34.91	15	0	15	-15	-15
							3	35.07	15	15	-15	-15	0
4	35.15	15	15	0	-15	-15
							5	35.35	15	15	-15	0	-15
6	35.43	0	15	-15	15	-15
							7	35.46	15	-15	0	15	-15
8	35.51	0	0	15	-15	0
							9	35.52	0	15	-15	0	0
10	35.52	0	0	0	15	-15
							11	35.61	15	-15	15	-15	0
12	35.62	0	0	15	0	-15
							13	35.63	15	-15	0	0	0
14	35.65	-15	15	0	15	-15
							15	35.67	0	15	0	-15	0
16	35.70	-15	0	15	15	-15
							17	35.75	15	-15	15	0	-15
18	35.76	0	15	0	0	-15
							19	35.77	15	0	-15	0	0
20	35.78	15	0	-15	15	-15
							21	35.80	-15	15	15	-15	0
22	35.97	-15	15	15	0	-15

23	35.98	15	0	0	-15	0
							24	36.00	0	-15	15	15	-15
25	36.06	0	0	0	0	0
							26	36.09	-15	0	0	15	0
27	36.10	-15	0	0	0	15
							28	36.10	15	0	0	0	-15
29	36.14	-15	0	15	0	0
							30	36.28	-15	15	0	0	0
31	36.38	15	-15	-15	0	15
							32	36.40	0	15	-15	-15	15
33	36.41	0	-15	0	0	15
							34	36.44	0	-15	0	15	0
35	36.45	15	-15	-15	15	0
							36	36.49	-15	15	-15	0	15
37	36.49	0	-15	15	0	0
							38	36.55	-15	0	15	-15	15
39	36.57	-15	15	-15	15	0
							40	36.59	0	0	-15	0	15
41	36.63	0	0	-15	15	0
							42	36.72	15	-15	0	-15	15
43	36.72	15	0	-15	-15	15
							44	36.77	0	0	0	-15	15
45	36.81	-15	15	0	-15	15

46	36.89	0	-15	15	-15	15
							47	36.98	-15	-15	15	0	15
48	37.16	-15	-15	15	15	0
							49	37.19	-15	-15	0	15	15
50	37.42	-15	0	-15	15	15
							51	37.51	0	-15	-15	15	15

Table 4: the final optical states of the gray shade scale 3 to 1 of various FT sequences.

Call number	Optics (L*)	Frame 1	Frame 2	Frame 3	Frame 4	Frame 5
							1	36.86	0	15	15	-15	-15
2	36.92	15	0	15	-15	-15
							3	37.00	15	15	-15	-15	0
4	37.13	15	15	0	-15	-15
							5	37.39	15	15	-15	0	-15
6	37.47	0	15	-15	15	-15
							7	37.48	15	-15	0	15	-15
8	37.50	0	15	-15	0	0
							9	37.52	0	0	15	-15	0
10	37.53	0	0	0	15	-15
							11	37.60	15	-15	15	-15	0
12	37.62	15	-15	0	0	0
							13	37.63	0	0	15	0	-15
14	37.65	0	15	0	-15	0

15	37.67	-15	15	0	15	-15
							16	37.71	-15	0	15	15	-15
17	37.76	0	15	0	0	-15
							18	37.77	15	-15	15	0	-15
19	37.79	15	0	-15	15	-15
							20	37.80	15	0	-15	0	0
21	37.82	-15	15	15	-15	0
							22	37.96	15	0	0	-15	0
23	38.01	-15	15	15	0	-15
							24	38.03	0	-15	15	15	-15
25	38.04	0	0	0	0	0
							26	38.09	-15	0	0	15	0
27	38.09	15	0	0	0	-15
							28	38.15	-15	0	0	0	15
29	38.16	-15	0	15	0	0
							30	38.24	-15	15	0	0	0
31	38.40	15	-15	-15	0	15
							32	38.43	0	-15	0	0	15
33	38.44	0	-15	0	15	0
							34	38.44	0	15	-15	-15	15
35	38.46	15	-15	-15	15	0
							36	38.51	-15	15	-15	0	15
37	38.52	0	-15	15	0	0

38	38.59	-15	0	15	-15	15
							39	38.61	-15	15	-15	15	0
40	38.65	0	0	-15	0	15
							41	38.66	0	0	-15	15	0
42	38.74	15	0	-15	-15	15
							43	38.74	15	-15	0	-15	15
44	38.82	0	0	0	-15	15
							45	38.89	-15	15	0	-15	15
46	38.95	0	-15	15	-15	15
							47	39.02	-15	-15	15	0	15
48	39.21	-15	-15	15	15	0
							49	39.22	-15	-15	0	15	15
50	39.44	-15	0	-15	15	15
							51	39.53	0	-15	-15	15	15

Subsequently, the cRSGS waveform adopt utilize table 2 to 4 and the analog of the FT sequence chosen of result shown in Figure 11 (specifically, from the sequence 33 of table 2, from the sequence 49 of table 3 and from the sequence 4 of table 4) and their other final gray shade scale construct.Be noted that on the y axle among Figure 11～36.9 with～37.5L* between the identical final (R of region representation ₁) state with by adopting DC balance FT sequence to become available different initial (R ₂) overlapping between the optical reflectivity of state.Therefore, R ₁=1 target gray shade scale is chosen at the 37.2L* place, and each R near the final optical states of this target is provided to provide ₂The FT sequence.This process is to other final optical states (R ₁=0,2 and 3) carry out repeatedly.

At last, the gained waveform adopts the foregoing pseudo-random sequence that comprises whole five degree of depth state histories to test.This sequence comprises 324 and is subjected to pay close attention to transformation.CRSGS waveform through selected FT sequence modification is used for realizing that the institute in this sequence changes, and writes down the reflectivity of each optical states of being realized.The optical states of being realized is drawn among Figure 12.Be perfectly clear by comparing Figure 12 and Figure 10, the dispersiveness of the reflectivity of each gray shade scale is by greatly being reduced in conjunction with the FT sequence.

In a word, discontinuous addressing of the present invention aspect provides FT sequence, it or (i) allow the variation of optical states, perhaps (ii) allow to realize the DC balance of waveform or the method for the change of the uneven degree of DC at least.As mentioned above, for example, can provide the definition of the more mathematics of FT sequence for the uneven variant of the DC of this method:

(a) cause the applying of the uneven FT sequence of DC of different with the change in optical state of its DC reference pulse in fact change in optical state." DC reference pulse " is voltage V ₀Pulse, V wherein ₀Be with the FT sequence during the maximum voltage amplitude that applies corresponding but have the voltage of the symbol identical with the clean impulse of FT sequence.The clean impulse of sequence be at voltage to the area under the time curve, and represent by symbol G.The duration of reference pulse is T=G/V ₀This FT sequence is used for introducing the DC imbalance very different with the clean DC imbalance of its reference pulse.

(b) cause amplitude applying much smaller than the uneven FT sequence of DC of the change in optical state of the optical change that adopts its time reference pulse to obtain." time reference pulse " is defined as the single symbol potential pulse with the identical duration of FT sequence, but wherein the symbol of reference pulse changes with the maximum that optical states is provided through selection.That is to say that when electro-optical medium during near its white states, it is whiter slightly that negative voltage pulse only can drive electro-optical medium, positive voltage then can greatly be driven into black with electro-optical medium.The symbol of reference pulse is in this case for just.The purpose of such FT pulse is to adjust clean voltage impulse (for example being used for the DC balance), can greatly not influence optical states simultaneously.

Discontinuous addressing of the present invention aspect also relates to notion between the pulse element that utilizes transition waveforms or that insert one or more FT sequence, and relates to the notion that employing FT sequence is come previous gray shade scale of balance and the effect of the previous residence time.A particular instance of the present invention is to insert in the middle of certain pulse element of waveform or the no-voltage frame between some pulse elements of waveform is used to change final optical states.

Discontinuous addressing of the present invention aspect also allows waveform is finely tuned so that realize having the expection gray shade scale of anticipate accuracy, and allow to adopt the Source drive that do not allow voltage trim, the Source drive that particularly only has two or three voltage levels make waveform can be more near the mode of DC balance zero clean voltage impulse of any cyclic process of various gray shade scales (that is, to).

DC balance addressing method

It should be noted that, Figure 11 A of above-mentioned WO 03/044765 and the sawtooth drive scheme utmost point shown in Figure 11 B are suitable for the DC balance, only can be between any given continuous pixels is by black state because this sawtooth drive scheme is guaranteed through the transformation of limited number of times, and in fact on average, pixel will be at half process black state of its transformation.

But, as mentioned above, according to DC balance addressing method of the present invention, DC balance according to the present invention is not limited to carry out balance for the total amount of the impulse that is applied to electro-optical medium in a series of transition processes, but also expand to the pixel that makes display at least a portion " inside " DC balance of transformation of process; To describe this method in detail now.

DC balance addressing method of the present invention relates to and is advantageously used in the DC balance change that the encapsulation electrophoresis that drives display application and other impulse drive electro-optical medium.This method for example can be applicable to have the Active Matrix Display that only can export the Source drive of two or three voltages.Though can use the driver of other type, following detailed description major part concentrates on the example that adopts the Source drive with three voltage outputs (positive and negative and zero).

In following description to DC balance addressing method of the present invention, in the description of others of the present invention, the gray shade scale of electro-optical medium will be expressed as 1 to N as the front, and wherein, 1 the darkest state of expression and N represent the brightest state.Intermediateness is from secretly to the bright numbering that increases progressively.Being used for drive scheme that impulse drives image forming medium utilizes one group of rule to realize transformation from initial gray shade scale to final gray shade scale.Drive scheme can be expressed as the voltage as the function of the time of each transformation, as in the table 5 for shown in 16 each that may change of 2 (4 gray shade scale) gray level display devices.

Table 5

In the table 5, the waveform that Vij (t) expression is used to carry out the transformation from gray shade scale i to gray shade scale j.The DC balance change is that the time integral of waveform Vij (t) is zero transformation.

Be defined as the extreme optical state of expression electro-optical medium more than the term " optics railing ".To adopt phrase " medium to be pushed or shifted onto to the optics railing " below." to " represent that voltage is applied in so that the optical states of medium is shifted to one of optics railing." push away " the expression potential pulse have make electro-optical medium optical states in fact near the abundant duration and the amplitude of one of optics railing.Be noted that importantly " shifting the optics railing onto " is not that expression optics railing state necessarily is implemented when end-of-pulsing, but expression is implemented when end-of-pulsing near the optical states of final optical states in fact.For example, consider to have the electro-optical medium of the optics railing that is in 1% and 50% reflectivity.Find that 300 milliseconds of pulses make final optical states (from 1% reflectivity) change to 50% reflectivity.May mention 200 milliseconds of pulses and shift display onto high reflectance optics railing, even it realizes having only the final reflectivity of 45% reflection.These 200 milliseconds of pulses are considered to shift medium one of onto optics railing, because compare with the major part of passing optical range, as the required time of the centre 1/3rd of optical range, 200 milliseconds of duration are long (in this case, pass through the centre 1/3rd of reflectivity range, be the required pulsion phase ratio of from 17% to 34% reflection that with making medium 200 milliseconds long here).

To describe now according to three of DC balance addressing method of the present invention dissimilar DC balance changes, and adopt DC balance and the uneven combination drive scheme that changes of DC.For convenience of explanation, in the following description, pulse will be by numeric representation, the duration of the big or small indicating impulse of numerical value.If numerical value is being for just, then pulse is being for just, and if numerical value for negative, then pulse is for negative.Therefore, for example, if voltage available be+15V, 0V and-15V, and the duration of pulse measure with millisecond (msec), 300 milliseconds, the pulse of 15V are represented in the pulse that then is characterized by x=300, and x=-60 represent 60 milliseconds ,-pulse of 15V.

Type i:

In the DC balance change of first simple types of the present invention, the front of potential pulse (" x ") is equal length but the pulse (" x ") of contrary sign, as shown in figure 13.(notice that itself can bear the value of x, so the positive and negative pulse may be to occur with reverse order shown in Figure 13.)

As mentioned above, have been found that according to discontinuous addressing method of the present invention, the effect that is used for realizing the waveform that changes by among any of the pulse of waveform or before exist (being actually time delay) in no-voltage cycle revise.Figure 14 and Figure 15 explanation are to the modification of the waveform of Figure 13.In Figure 14, time delay is inserted between two pulses of Figure 13, and in Figure 15, time delay is inserted in second pulse of Figure 13, and perhaps the result is the same, and second pulse of Figure 13 is divided into two independent veins separating by time delay and dashes.As mentioned above, time delay can add waveform so that realize not having these to postpone with regard to unavailable optical states.Time delay also can be used to finely tune final optical states.This fine-tuning capability is important, because in driven with active matrix, the temporal resolution of each pulse is defined by the sweep speed of display.The temporal resolution that sweep speed provided is out of true very, does not have certain additional method for trimming just can't realize accurate final optical states.Time delay provides the little degree fine setting to final optical states, and supplementary features as described below then provide the append mode to the coarse adjustment and the fine setting of final optical states.

Type II:

The Type II waveform is made up of the above-mentioned type I waveform that wherein in certain positive and negative pulse of naming a person for a particular job (being expressed as " y " and " y " pulse) is inserted the type i waveform, as Figure 16 with symbolic representation.Y and-the y pulse needs not to be continuous, but can appear in the original waveform at diverse location.The Type II waveform that two particularly advantageous forms are arranged.

Type II: special case A:

In this special shape, " y, y " pulse is to being arranged on " x, x " pulse to before.Have been found that when y and x are contrary sign, as shown in figure 17, final optical states can by the duration y's in addition rough adjustment of appropriateness finely tune.Therefore, the value of x can be coarse adjustment control and adjusts, and the value of y is that the fine setting of the final optical states of electro-optical medium is adjusted.We think can this thing happens, because y pulse increases-x pulse, thereby the change electro-optical medium is pulled to the degree of one of its optics railing.Shift that the degree of one of optics railing is known to provide meticulous adjustment to final optical states afterwards in the pulse of leaving that optics railing (being provided by the x pulse in this case) onto.

Type II: special case B:

For above-mentioned reason, having been found that advantageously to adopt to have to look is enough to electro-optical medium is driven in fact the waveform of at least one pulse element of an optics railing.In addition,, also wish to reach final optical states, only need short final pulse near the gray shade scale of optics railing because realize from nearer optics railing for the more joyful transformation of vision.Such waveform needs at least one long pulse to bring to be driven into optics railing and short pulse to reach final optical states near this optics railing, thereby can't have the structure of the above-mentioned type I.But the special case of Type II waveform can realize such waveform.Figure 18 represents an example of this waveform, and wherein the y pulse is arranged on-x, the x pulse to after, and-the y pulse is arranged on-x, the x pulse is to before.In such waveform, final y pulse provides coarse adjustment, because final optical states is very responsive to the amplitude of y.The x pulse provides fine setting, because final optical states can greatly not depend on the amplitude that is driven into the optics railing usually.

Type-iii:

The DC balanced waveform of the third type of the present invention (type-iii) is introduced waveform with another DC equalizing pulse to (being expressed as " z ", " z "), shown in Figure 19 signal.A preferred embodiment of this type-iii waveform as shown in figure 20; Because underlying cause, such waveform is useful for the fine setting of final optical states.Consider not have z and-situation (being the above-mentioned type II waveform) of z pulse.X pulse element is used for fine setting, and final optical states can reduce and increases by reducing x by increasing x.But, do not wish x is reduced to above certain point, because can as waveform stable required, not make electro-optical medium at that time enough near the optics railing.For fear of this problem, be not to reduce x, but can (in fact) by interpolation-z, the z pulse is to increasing-x pulse and do not change the x pulse, as shown in figure 20, wherein z has the symbol opposite with x.Z pulse increase-x pulse, and-the z pulse makes to change and remains zero clean impulse, promptly keeps the DC balance change.

The above-mentioned type I, II and III waveform can be revised by variety of way undoubtedly.Additional pulse to adding waveform to so that realize more generally structure.The advantage that this class is additional right reduces along with the pulse number of elements that increases, but this class waveform is the natural expansion of type i, II and III waveform.In addition, as mentioned above, one or more time delays can be inserted all places in any of waveform, and its mode is with identical shown in Figure 14 and Figure 15.As previously described, the final optical states that the time delay influence of pulse is realized, thereby be useful for fine setting.In addition, by changing Transition element with respect to other element in the same transition and with respect to the position of the Transition element of other transformation, the setting of time delay can change the visual appearance of transformation.Time delay also can be used to aim at some waveform Transition element, and this may be favourable for some display modules with some controller ability.In addition, recognize that the little variation of the ordering of the pulse that applies may change the fact of pulse optical states afterwards in fact, output signal also can be by changing all or part of of one of above-mentioned pulse train or changing or form by in any position one or more 0V cycle being inserted one of above-mentioned sequence by all or part of the repeating of one of above-mentioned sequence.In addition, these transposings and insertion operational character can make up (for example, inserting the 0V part, transposing then, and then insertion 0V part) according to any order.Be noted that importantly all these class pulse trains that these conversion form keep having the zero fundamental characteristics of impulse only.

At last, the DC balance change can combine to form complete drive scheme with uneven transformation of DC.For example, the common pending application sequence number 60/481053 that on July 2nd, 2003 submitted to has been described type-TM (R1, R2) [IP (R1)-IP (R2)] TM (R1, R2) preferred wave shape form, wherein the difference of the impulse current potential between the final sum original state of the transformation considered of [IP (R1)-IP (R2)] expression represents that then the DC equalizing pulse is right for all the other two.For convenience of explanation, this is called below waveform-x/ Δ IP/x waveform, and as shown in figure 21.Though satisfactory for the transformation between the different optical state, this waveform is then not too satisfactory for zero identical transformation of initial and final optical states.For these zero transformations, adopt for example Figure 17 and Type II waveform shown in Figure 180 in this example.With symbolic representation, from wherein seeing ,-x/ Δ IP/x waveform is used for non-zero to be changed, and the Type II waveform is used for zero transformation in this complete waveform such as the table 6.

Table 6

		Final gray shade scale
							1	2	3	4
Initial gray shade scale	?1	Type II	-x/ΔIP/x	-x/ΔIP/x	-x/ΔIP/x
						?2	-x/ΔIP/x	Type II	-x/ΔIP/x	-x/ΔIP/x
	?3	-x/ΔIP/x	-x/ΔIP/x	Type II	-x/ΔIP/x
						?4	-x/ΔIP/x	-x/ΔIP/x	-x/ΔIP/x	Type II

DC balance addressing method is not limited to wherein undoubtedly, and the DC balance change is limited to such transition matrix that identical " principal diagonal " of initial and final gray shade scale changes; In order to produce the greatest improvement of gray shade scale control, wish to make the quantity maximum of the transformation that belongs to the DC balance.But, according to employed specific electro-optical medium, may be difficult to relate to or from extreme gray shade scale, for example to or from black and white, promptly be respectively the DC balance change of the transformation of gray shade scale 1 and 4.In addition, when which selecting change the DC balance into, importantly do not allow whole transition matrix imbalance, that is, producing the closed circulation that wherein begins and finish in the same grayscale grade is the unbalanced transition matrix of DC.For example, only relate to gray shade scale Unit 0 or 1 variation change the DC balance into but other to change the unbalanced rule of DC into be not required because this will make whole transition matrix imbalance, in the example below; The pixel of the sequence of process gray shade scale 2-4-3-2 will make that whole circulation is uneven through changing 2-4 (DC imbalance), 4-3 (balance) and 3-2 (balance).Reality between the hope of these two conflicts is compromise can be to adopt the DC balance change under the situation that only relates to middle gray grade (grade 2 and 3), and adopts the DC imbalance to change under the situation that extreme gray shade scale (grade 1 or 4) begins or finishes in transformation.Obviously, the middle gray grade of selecting for this rule can change along with employed specific electro-optical medium and controller; For example, in three (8 gray shade scale) displays, perhaps can in being changed, adopt the DC balance change with gray shade scale 2-7 (perhaps perhaps 3-6) beginning or the institute that finishes, and employing DC imbalance transformation in being changed with gray shade scale 1 and 8 (or 1,2,7 and 8) beginning or the institute that finishes.

Can see from the above, DC balance addressing method of the present invention allows waveform is finely tuned realizing the expection gray shade scale accurately, and adopts and do not allow the Source drive of voltage trim, particularly only have the Source drive of two or three voltage levels can make waveform change the mode with zero clean voltage.We think that the DC balanced waveform changes provides the uneven waveform more performance than DC.The present invention generally is applicable to display, especially but be not to be applicable to the Active Matrix LCD At module with Source drive that two or three voltages only are provided exclusively.The present invention also is applicable to have provides the more Active Matrix LCD At module of the Source drive of voltage levels.

DC balance addressing method of the present invention can provide some attendant advantages.As mentioned above, in driving methods more of the present invention, transition matrix is to be different from the variable of previous optical states, the function of the temperature of the time span since the last time upgrades or display medium for example.In having uneven these situations that change, keep the DC equilibrium phase when difficulty.For example, consider 25 ℃ from white to black then at 0 ℃ of display that repeats to change from black to white.Indicate adopting than long pulse length usually of low temperature than slow-response.Therefore, display will experience the clean DC imbalance towards white.On the other hand, if to change be internal balance, then different transition matrix can freely be mixed, and does not introduce the DC imbalance.

The defined range method

As mentioned above, the undesirable effect of replacement step can be upgraded, promptly further reduce by those parts that only are rewritten as in the display that changes between the consecutive image by adopting the part rather than the overall situation, and part to be rewritten is selected based on " regional area " or individual element.For example, as at the diagrammatic sketch of the part of explanation mechanical hook-up or be used for the diagrammatic sketch of accident reconstruct, find that a series of images that moves than small object is not rare on bigger static background.In order to use local updating, display controller need compare final image and initial pictures, and determines which (which) zone is different and thereby need to rewrite between two images.Controller can be discerned and be generally the rectangular area with the axle that aligns with pixel grid, the one or more regional areas that comprise the pixel that need be updated, and perhaps just discerns each pixel that need be updated.In the above-described drive scheme any then can be used for only upgrading regional area or the individual pixel that is identified as the needs rewriting by this way.This local updating scheme can reduce the energy consumption of display in fact.

In addition, as mentioned above, defined range method of the present invention provides a kind of permission to adopt different update methods to upgrade the defined range method of bistable electro-optic displays in the zones of different of display.

Electro-optic displays is known, and wherein whole display can adopt one or grey-scale modes to drive.When display is in a bit pattern, upgrade and adopt general image stream (GIF) waveform to realize, and when display is in grey-scale modes, upgrade and adopt many prepulses lantern slide waveform or other certain slow wave shape to realize, even have only an information to be updated in the specific region of display.

By two additional commands of definition in controller, i.e. " defined range " order and " removing All Ranges " order, this electro-optic displays can be revised as the defined range method of the present invention of carrying out." defined range " order usually the position of the rectangular area that is enough to intactly define display as argument, for example upper right corner of institute's defined range and the position in the lower left corner; This order also can have the additional argument of specifying the set bit depth of institute's defined range, but this last argument is always optional in the defined range method of monochromatic simple form at institute's defined range.The set bit depth of last argument surpasses undoubtedly to the previous any bit depth that is provided with of institute's defined range.Perhaps, " defined range " order can be specified the series of points on the polygonal summit of definition.Argument may not be got in " removing All Ranges " order, and just whole display is reset to single predefined bit depth, perhaps may get specify various possible bit depth which after clear operation by the single argument of whole display employing.

Everybody will appreciate that defined range method of the present invention is not limited to have only the use in two zones, and more multizone can provide as required.For example, in image editor, having the main areas of the image of being edited with complete bit depth demonstration and information display area territory (frame that for example shows current cursor position) and dialog box zone (being of moving with a bit pattern that user input text provides dialog box), may be helpful.Mainly describing the present invention with two area formats below, is that the technician in structure field of display controller is perfectly clear because revise for necessity of allow using more than two zones to carry out.

In order to follow the tracks of the degree of depth of zones of different, controller can keep memory element array, and an element is related with each pixel in the display, and the value of the present bit degree of depth of each element storage representation associated pixel.For example, can adopt 800 * 600 arrays (respectively comprise 0 for 1 bit pattern, respectively comprise 1) of 1 bit unit with XVGA (800x600) display of 1 or 2 bit pattern work for 2 bit patterns.In sort controller, element in the defined range of " defined range " order display is set to the bit depth of being asked, and " removing All Ranges " order then resets to all elements of array identical value (perhaps for predetermined value or be the defined value of argument of order).

Alternatively, when the zone is defined or removes, controller can be carried out the pixel in that zone and upgrade sequence, thereby with display from a kind of mode shifts to another kind of pattern, so that guarantee the optical states of DC balance or adjustment related pixel, for example by adopting aforesaid FT sequence to carry out.

When display was worked with the defined range pattern, new images was sent to controller, and display must be refreshed, and three kinds of possible situations are arranged:

1. have only defined (such as) pixel in zone changes.In this case, (soon) waveform can be used to refresh display;

2. have only the pixel in undefined (gray level) zone to change.In this case, gray level (slowly) waveform must be used for refresh display (noticing that owing to according to definition, do not have pixel to be changed, therefore the clarity of institute's defined range, for example dialog box is not a problem during screen-refresh in institute's defined range); And

3. define and undefined zone in pixel all change.In this case, gray-level pixels adopts the gray level waveform to upgrade, and a pixel adopts a digit wave form to upgrade (short digit wave form must suitably carry out zero padding so that the length that the coupling gray level is upgraded).

Controller can be before type scanner, by carrying out following logic testing, determine these situations any existence (suppose a place value and the storage pixel pattern related with each pixel, as mentioned above):

(Old_image XOR new_image)＞0: pixel changes in display

(Old_image XOR new_image) AND mode_array＞0: gray-level pixels is changed

(Old_image XOR new_image) AND (NOTmode_array)＞0: include monochrome pixels is changed

When the controller type scanner, for situation 1 or situation 2, can adopt a waveform look-up table for all pixels, will not receive 0V because change pixel, suppose zero in the bit pattern change with grey-scale modes in identical (in other words, two kinds of waveforms are local updating).On the contrary, if the gray level waveform upgrades (upgrading all pixels when refresh display) for the overall situation, then controller need be tested so that whether check pixel is in the appropriate area, upgrades waveform so that determine whether to apply the overall situation.For situation 3, controller must be checked the value of the pattern bit array of each pixel in scanning when determining to use which waveform.

Alternatively, if the brightness value of the black and white state of in a bit pattern, realizing with in grey-scale modes, realize identical, then in above-mentioned situation 3, the gray level waveform can be used for all pixels in the display, thereby has eliminated the needs for the transport function between and the gray level waveform.

Defined range method of the present invention can be utilized any of optional feature of basic look-up table method, as mentioned above.

The major advantage of defined range method of the present invention is that it allows to use a quick digit wave form on the display that just shows the grayscale image that had before write.The display controller of prior art only allows display in any one time or be in gray level or be in a bit pattern usually.Though can write a bit image at grey-scale modes, waveform correlation is quite slow.In addition, defined range method of the present invention is transparent for the host computer system (system is generally computing machine) that image is offered controller basically, because host computer system does not need which waveform of controller suggestion use.At last, the defined range method allows one and gray level waveform to use on display simultaneously, and if two kinds of waveforms all are used, two update event of separating of other solution requirement then.

Further general waveform is discussed

Above-mentioned drive scheme can change in many aspects, depends on the characteristic of employed certain electric optical display unit.For example, in some cases, perhaps can eliminate the many replacement steps in the above-mentioned drive scheme.For example, if employed electro-optical medium is bistable (gray shade scale that promptly writes pixel only compole slowly change) at any time at long period, and the required impulse of special transition can greatly not change along with the cycle that pixel is in its initial grey states, then look-up table can be arranged to directly make grey states to reach grey states to change and need not any centre to black or white states and return, wherein only when after the abundant cycle of process, pixel from its nominal gray shade scale gradually " drift " caused when presenting appreciable error the image, the replacement of display just is performed.Therefore, for example,, then perhaps can before the replacement that needs display, show a lot of information screens if the user is used as electronic book readers with display of the present invention; Find by experience, adopt suitable waveform and driver, nearly 1000 information screens can be shown before needs are reset, and made that the typical reading phase that in fact is reset at electronic book readers is unnecessary.

The technician in display technique field can be perfectly clear, and individual equipment of the present invention can dispose a plurality of different drive schemes effectively, uses under the different condition.For example, because in the Fig. 9 of above-mentioned WO 03/044765 and drive scheme shown in Figure 10, a big chunk that pulse consumes the total power consumption of display is set, so controller possible configuration first drive scheme, its display of resetting continually, thus make the grey level errors minimum, and the configuration alternative plan, it is only with the long display of resetting at interval, thereby allows bigger grey level errors but reduce energy consumption.Conversion between two schemes can manually or according to external parameter be carried out; For example, if display is used for laptop computer, then when computing machine relies on the mains electricity operation, can adopts first drive scheme, and when computing machine relies on the internal battery power operation, can adopt second drive scheme.

The bucking voltage method

Another change for basic look-up table method of the present invention and equipment provides by bucking voltage method and apparatus of the present invention, is elaborated now.

As mentioned above, bucking voltage method and apparatus of the present invention is managed to realize and the similar result of above-mentioned basic look-up table method, but be need not to store great look-up table.The size of look-up table is along with the quantity about the indexed original state of look-up table increases rapidly.For this reason, as mentioned above, employed original state quantity exists physical constraints and cost consideration during the impulse of the expection transformation of increase selection realization bistable electro-optic displays.

In bucking voltage method and apparatus of the present invention, the size of required look-up table reduces, and is each pixel storage bucking voltage data of display, and data based at least one impulse that before had been applied to related pixel of this bucking voltage calculates.The voltage that is applied to pixel at last for the driving voltage from look-up table, selected in due form with from the determined bucking voltage sum of the bucking voltage data that are used for related pixel.In fact, the bucking voltage data apply " correction " to pixel, and this correction for example originally applies by one or more additional original states are consulted look-up table by index.

Employed look-up table can be any of the above-mentioned type in the bucking voltage method.Therefore, look-up table can be a simple bivariate table of only considering the initial and end-state of pixel in the relevant transition process.Perhaps, look-up table can be considered one or more times and/or gray shade scale original state.Bucking voltage can also only be considered the bucking voltage data for the related pixel storage, but also can consider one or more times and/or gray shade scale original state alternatively.Bucking voltage can be not only be applied in cycle of pixel but also having driving voltage to be applied in what is called " maintenance " state of pixel at driving voltage and is applied to related pixel.

The butt formula can the greatly variation along with the characteristic of employed bistable state electric light medium really to determine the bucking voltage data.The bucking voltage data are come periodic modification in the determined mode of driving voltage that is applied to pixel in current and/or one or more scanning frames usually.In a preferred form of the invention, the bucking voltage data comprise single number (register) value related with each pixel of display.

In a preferred embodiment of the invention, scanning frame is formed superframe in foregoing mode, makes the display renewal only begin at the section start of superframe.For example, superframe can be made up of ten reading scan frames, makes for the display with 50Hz sweep speed, and reading scan is that 20ms is long, and superframe is then long for 200ms.During each superframe when display is rewritten, the bucking voltage data related with each pixel are updated.Renewal comprises two parts of following order:

(1) adopt with relevant superframe during the fixedly algorithm that has nothing to do of the pulse that applies revise preceding value; And

(2) will increase the determined amount of impulse that applies during the relevant superframe from the value of step (1).

In a certain preferred embodiment of the present invention, carry out according to following manner step (1) and (2):

(1) with preceding value divided by the fixed constant that is preferably two; And

(2) will from the value of step (1) increase with relevant superframe during be applied to the proportional amount of the total area under the voltage/time curve of electro-optical medium.

In step (2), increment can be accurately or just approx with relevant superframe during voltage/time curve under area proportional.For example, followingly describe in detail with reference to Figure 22, increment can " quantize " to the finite aggregate of class of the waveform that might apply, each class comprises all waveforms with two total areas between the boundary, and determines increment by the class under the applying waveform in step (2).

Provide following example now.Employed display is two gray level encapsulated electrophoretic display, and the driving method that is adopted uses two-dimensional look-up table as shown in table 7 below, the initial and end-state that its consideration expection changes; In this table, column heading is represented the expection end-state of display, and row headers represents original state, and the numeral in each cell will be applied to the voltage of the unit of pixel for volt at predetermined period.

Table 7

In order to consider the enforcement of bucking voltage method of the present invention, the odd number value register is related with each pixel of display.Various impulses shown in the table 7 are classified, and the pulse class is related with each impulse, as shown in table 8 below.

Table 8

Pulse voltage (V)	-15	-9	-6	?0	+6	+9	+15
								The pulse class	-30	-18	-12	?0	12	18	30

During each superframe, the numerical value register related with each pixel increases for the pulse that is applied to related pixel during identical superframe at the numerical value shown in the table 13 then divided by 2.The voltage that is applied to each pixel during superframe is the bucking voltage V that driving voltage as shown in table 12 and following formula provide _CompSum:

V _Comp=A* (pixel register)

Wherein, the pixel register value reads from the register related with related pixel, and " A " is predefined constant.

In the proof of the laboratory of this preferred compensation voltage method of the present invention, adopt single pixel display of being clipped in the encapsulated electrophoretic medium between the parallel pole (electrode in front is made of and printing opacity ITO) by 300 milliseconds+/-the 15V square-wave pulse is driven between its black and white state.The display that begins with its white states is driven to black, drives again then to be white after the residence time.The brightness that has been found that the final white state is the function of stop state, shown in Figure 22 as accompanying drawing.Therefore, this encapsulated electrophoretic medium is to residence time sensitive, and the L* of white states wherein changes about 3 units according to the residence time.

In order to represent the effect of bucking voltage method of the present invention, experiment is carried out repeatedly, but appends to each pulse by the bucking voltage of forming by exponential damping voltage that begins when each driving pulse finishes.The voltage that applies is driving voltage and bucking voltage sum.As shown in figure 22, much even under than situation in the white states that adopts each residence time under the situation of bucking voltage at compensated pulse not.Therefore, this experiment shows, can greatly reduce the residence time sensitive of encapsulated electrophoretic medium according to the use of this class compensated pulse of the present invention.

Bucking voltage method of the present invention can be utilized any of optional feature of above-mentioned basic look-up table method.

Can see that from the above description the invention provides the method for the work that is used to control electro-optic displays, their utmost points are suitable for the characteristic based on the electrophoretic display device (EPD) and the similar display of bistable state particle.

Also see from the above description, the invention provides the method for the work that is used to control electro-optic displays, their allow that the accurate control of gray level be need not whole display and frequently glimmer to one of its extremity inconveniently.The present invention also allows the accurate control of display regardless of its temperature and the variation of working time, is reduced the power consumption of display simultaneously.These advantages can realize at a low price, because controller can be constructed by the assembly of market sale.

The DTD integration reduces method

As mentioned above, have been found that, as if under the part situation, the required impulse of the given transformation in the bistable electro-optic displays changed with the hold-up time of pixel in its optical states at least, be not called " residence time correlativity " or " DTD " below this phenomenon of not discussing in the past in the document.Therefore, may wish or even in fact must change into the impulse that given transformation applies under the part situation as the function of the hold-up time of pixel in its initial optical state.

Be described in more detail the phenomenon of residence time correlativity referring now to Figure 23 of accompanying drawing, it is expressed as the reflectivity of pixel by R ₃→ R ₂→ R ₁The function of the time of represented transformation sequence, wherein, R _kGray shade scale in each expression gray shade scale sequence of item, the R with big index appears at before the R with less index.Also represented R ₃With R ₂Between and R ₂With R ₁Between transformation.DTD is optical states R ₂The final optical states R that variation produced of middle consumption time ₁Variation, the described consumption time is called the residence time.The method of the residence time correlativity when DTD integration of the present invention reduces method and is provided for reducing to drive bistable electro-optic displays.

Though the present invention never is subjected to the restriction about any theory in its source, as if to a great extent, DTD is caused by the remaining electric field that electro-optical medium experienced.These remaining electric fields are the residues that are applied to the driving pulse on the medium.Usually say that residual voltage is produced by applying pulse, and residual voltage is just to be fit to the common mode scalar electromotive force corresponding with remaining electric field of static theory.These residual voltages can make the optical states of display membrane drift about in time.They also can change the effect of subsequent drive voltage, thereby change that succeeding impulse resulting final optical states afterwards.Like this, can make end-state after the waveform subsequent be different from situation when two transformations are very independent each other from the residual voltage of a transition waveforms.Enough separate feasible residual voltage decay in fact before applying second transition waveforms on " very independent " express time from first transition waveforms greatly.

From transition waveforms and the measurement that is applied to the residual voltage that the simple pulse of other of electro-optical medium produces show that residual voltage decays in time.It seems that decay be dull, but be not only by index law.But quite approx, decay can be approximately by index law, under the situation of most of encapsulated electrophoretic medium of being tested, has about one second damping time constant, and other bistable state electric light medium estimates to show similar die-away time.

Therefore, DTD integration of the present invention reduces the method that method provides a kind of driving to have the bistable electro-optic displays of at least one pixel, and it comprises to pixel and applies waveform V (t), makes:

J = {&Integral;}_{0}^{T} V (t) M (T - t) dt - - - (1)

(wherein, T is the length of waveform, integration is to carry out on the duration of waveform, V (t) is the waveform voltage as the function of time t, and M (t) characterizes the memory function cause in the reduction of the residual voltage effect of time zero residence time correlativity that produces from short pulse of place) less than about 1 weber.Comparatively ideally be, J is less than about 0.5 weber, and it would be desirable less than about 0.1 weber.In fact, J should be arranged to as far as possible little, and ideal situation is zero.

Waveform can be through design, and they are by producing J value and thereby the minimum DTD that composite vein is brought provides extremely low.For example, the long negative voltage pulse before shorter positive voltage pulse (having identical size but the voltage amplitude of contrary sign) can produce the DTD that more reduces.We think (but the present invention never is subjected to the restriction of this view), and two pulses provide the residual voltage with contrary sign.When the length ratio of two pulses correctly is provided with, can makes from the residual voltage of two pulses and cancel out each other to a great extent.The adequate rate of the length of two pulses can be determined by the memory function of residual voltage.

In currently preferred embodiment of the present invention, J is calculated by following formula:

J = {&Integral;}_{0}^{T} V (t) \exp (- \frac{T - t}{τ}) dt - - - (2)

Wherein, τ is optimum by rule of thumb decay (relaxing) time of determining.

For some encapsulated electrophoretic medium, have been found that rule of thumb the waveform that produces little J value also produces low especially DTD, the waveform with king-sized J value then produces big DTD.In fact, can find good relevantly between the J value of calculating by following formula (2), τ wherein is set to one second, be substantially equal to measured die-away time of the potential pulse that applies residual voltage afterwards.

Therefore, advantageously, by wherein (perhaps most of at least transformation the look-up table) is to adopt the waveform of the waveform realization that little J value is provided to use above-mentioned patent and the method described in the application from a kind of gray shade scale to alternative each transformation.This J value is preferably zero, but has been found that rule of thumb that at least for the encapsulated electrophoretic medium described in above-mentioned patent and the application, as long as J has the amount less than about 1 weber at ambient temperature, the residence time correlativity that is then produced is quite little.

Therefore, the invention provides a kind of waveform that is used to realize one group of transformation between the optical states, wherein, change for each, institute's calculated value of J has fractional value.J calculates by the memory function of estimating the possibility monotone decreasing.This memory function is not arbitrarily, but can estimate the residence time correlativity of simple potential pulse or composite voltage pulse by the observation display film.For example, can apply the transformation that potential pulse is realized from first to second optical states, wait for the residence time, apply second potential pulse then and realize from second the transformation to the tertiary voltage pulse to display membrane.By the skew of monitoring, can determine the approximate shapes of memory function as the 3rd optical states of the function of the residence time.Memory function have roughly be similar to the 3rd optical states and it the value of long residence time poor, as the shape of the function of the residence time.Memory function then is endowed this shape, and has the odd number amplitude when its argument is zero.This method only produces the approximate value of memory function, and for various final optical states, the measured shape of memory function is estimated slightly to change.But, total characteristic, as the characteristic time of the decay of memory function should be similar for various optical states.But, be to obtain in centre three/a period of time that the 3rd optical states is in the optical range of display medium if having the notable difference of shape, the best memory function shape that then will adopt for final optical states.The total characteristic of memory function also should be can estimate by the decay of test institute's potential pulse that applies residual voltage afterwards.

Yet described here being used to estimates that the method for memory function is not accurate, has been found that even is good guidance to the waveform with low DTD from the J value that approximate memory is calculated.Useful memory function is represented the total characteristic of the temporal correlation of aforesaid DTD.For example, have been found that by index law, memory function with die-away time of one second and be applicable to that very prediction provides the waveform of low DTD.To change into the validity of the J value that produces of the predictive operator that can not destroy the low DTD waveform of conduct in 0.7 or 1.3 second die-away time.But, can not decay but ad infinitum to remain the memory function of odd number obviously not too useful as predictive operator, and have extremely short die-away time, be not the good predict operator of low DTD waveform as 0.05 second memory function.

The example that the waveform of little J value is provided is above-mentioned Figure 19 and waveform shown in Figure 20, and wherein, x, y and z pulse all have the duration of the characteristic decay time that is far smaller than memory function.Operational excellence when this waveform satisfies in this condition is because this waveform is made up of the reversed in order pulse element that its residual voltage trends towards roughly offsetting.For not being much smaller than characteristic decay time of memory function but being not more than x and the y value of this die-away time, have been found that, the waveform that x wherein and y have contrary sign often provides lower J value, and can find that in fact x and y duration of pulse allow minimum J value, because being provided at, various pulse element applies the residual voltage of cancelling out each other or cancelling out each other at least to a great extent after the waveform.

Everybody will appreciate that the J value of given waveform can be by inserting the no-voltage cycle waveform or adjusting the length in any cycle of the no-voltage that has existed in the waveform and control.Like this, can use various waveforms, the J value is kept near zero.

DTD integration of the present invention reduces method and has general applicability.Waveform configuration can be designed to the J value of calculating by parameter, its various value for these parameters and the J value is described for minimum selected suitable parameter value, thereby reduces the DTD of waveform.

Claims

1. a driving has the method for the bistable electro-optic displays of a plurality of pixels, and wherein each pixel can show at least three gray shade scales, and described method comprises:

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, determine from described look-up table,

Wherein at least one transformation from the original state to the end-state, described output signal comprises the uneven fine setting of DC sequence, described sequence:

(a) has the clean impulse of non-zero;

(b) be discontinuous;

(c) cause the variation of the gray shade scale of pixel, this changes in fact different with the variation of the optical states of its DC reference pulse, and wherein the DC reference pulse is voltage V ₀Pulse, V wherein ₀Be to finely tune the maximum voltage that is applied during the sequence, but have and finely tune the identical symbol of clean impulse G of sequence, and the duration of reference pulse is G/V ₀And

(d) cause the variation of the gray shade scale of pixel, the variation of the gray shade scale that the amplitude that changes is caused less than its time reference pulse, wherein the time reference pulse is defined as and the unipolar voltage pulse of finely tuning the identical duration of sequence, but wherein the symbol of reference pulse is the symbol of bigger variation that gray shade scale is provided.

2. the method for claim 1 is characterized in that, half of the variation of the gray shade scale that the variation of the gray shade scale of the pixel that described fine setting sequence causes is caused less than its time reference pulse.

3. the method for claim 1 is characterized in that, for described at least one transformation, output signal also comprises at least one one pole driving pulse except the fine setting sequence.

4. the method for claim 1 is characterized in that, for described at least one transformation, output signal is acyclic.

5. the method for claim 1 is characterized in that, changes for the major part in the described look-up table, and output signal has the clean impulse of non-zero and is discontinuous.

6. the method for claim 1 is characterized in that, for described at least one change, output signal only by have voltage level+V, 0 and-pulse of V forms.

7. method as claimed in claim 5 is characterized in that, for described at least one change, output signal only by have voltage level 0 and+one of them pulse of V and-V forms.

8. method as claimed in claim 7 is characterized in that, for described at least one change, output signal by having before and after the pulse with voltage level 0 and this pulse+V and-at least two pulses of same voltage level are formed among the V.

9. method as claimed in claim 8, it is characterized in that, for most of transformation the in the initial different with end-state described look-up table of pixel wherein, output signal is made up of at least two pulses of voltage level same among having before and after the pulse with voltage level 0 and this pulse+V and the-V.

10. the method for claim 1 is characterized in that, indicator is the DC balance.

11. the method for claim 1 is characterized in that, for described at least one change, output signal is made up of a series of pulses as the integral multiple at single interval.

12. the method for claim 1, it is characterized in that also comprising the data of at least one gray shade scale original state of at least one the time original state of the described pixel of storage representation and/or a described pixel, and wherein output signal produces according to described at least one time original state and/or at least one gray shade scale original state of a described pixel.

13. a driving has the method for the bistable electro-optic displays of a plurality of pixels, wherein each pixel can show at least three gray shade scales, described method comprises that each pixel to display applies the output signal of effectively pixel being changed into end-state from original state, wherein, initial different with end-state at least one for pixel changes, and output signal is made up of at least two pulses of voltage level same among having before and after the pulse with voltage level 0 and this pulse+V and the-V.

14. a driving has the method for the bistable electro-optic displays of a plurality of pixels, wherein each pixel can show at least three gray shade scales, and described method comprises:

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, from described look-up table, determine,

Wherein at least one transformation from the original state to the end-state, output signal comprises DC balance fine setting sequence, described sequence:

(a) have and be essentially zero clean impulse; And

(b) can be in the fine setting sequence any point, the amount that the gray shade scale that makes pixel and the gray shade scale that it begins to locate in the fine setting sequence differ is above about 1/3rd of the gray shade scale difference between two extreme optical state of pixel.

15. method as claimed in claim 14 is characterized in that, for described at least one transformation, output signal also comprises at least one one pole driving pulse except the fine setting sequence.

16. a driving has the method for the bistable electro-optic displays of a plurality of pixels, wherein each pixel can show at least three gray shade scales, described method comprises that each pixel to display applies the output signal of effectively pixel being changed into end-state from original state, wherein, change at least one, described output signal is non-zero but DC balance.

17. method as claimed in claim 16 is characterized in that, for described at least one transformation, output signal comprises first paired pulses, comprising potential pulse with at the equal length of its front but the pulse of contrary sign.

18. method as claimed in claim 17 is characterized in that, described output signal also comprises the no-voltage cycle between described two pulses.

19. method as claimed in claim 17 is characterized in that, at least one in the described pulse interrupted by the no-voltage cycle.

20. method as claimed in claim 17 is characterized in that, for described at least one transformation, output signal also comprises equal length but second paired pulses of contrary sign.

21. method as claimed in claim 20 is characterized in that, described second paired pulses has and the different length of described first paired pulses.

22. method as claimed in claim 20 is characterized in that, first in described second paired pulses have with described first paired pulses in first opposite polarity.

23. method as claimed in claim 20 is characterized in that, described first paired pulses appear in described second paired pulses first and between second.

24. method as claimed in claim 16 is characterized in that, for described at least one transformation, output signal comprises at least one the pulse element that effectively pixel is driven into an optics railing in fact.

25. method as claimed in claim 16, it is characterized in that for each initial identical with end-state transformation of pixel, output signal is non-zero but DC balance, and for each transformation inequality of the initial and end-state of pixel, output signal is not the DC balance.

26. method as claimed in claim 25, it is characterized in that, initial and end-state each transformation inequality for pixel, output signal has-form of x/ Δ IP/x, wherein Δ IP is the impulse potential difference between the initial and end-state of pixel, and-x and x are equal length but a paired pulses of contrary sign.

27. method as claimed in claim 16 is characterized in that also comprising:

Produce the output signal of representing the original state of a described pixel is converted to the required impulse of its expection end-state, from described look-up table, determine.

28. a driving has the method for the bistable electro-optic displays of at least one pixel, comprising apply waveform V (t) to pixel, makes:

J = {&Integral;}_{0}^{T} V (t) M (T - t) dt

(wherein, T is the length of waveform, integration is to carry out on the duration of waveform, V (t) is the waveform voltage as the function of time t, and M (t) characterizes the memory function cause in the reduction of the residual voltage effect of time zero residence time correlativity that produces from short pulse of place) less than about 1 weber.

29. method as claimed in claim 28 is characterized in that, J is less than about 0.5 weber.

30. method as claimed in claim 29 is characterized in that, J is less than about 0.1 weber.

31. method as claimed in claim 28 is characterized in that, J is calculated by following formula:

J = {&Integral;}_{0}^{T} V (t) \exp (- \frac{T - t}{τ}) dt

Wherein τ is decay (relaxing) time.

32. process as claimed in claim 31 is characterized in that, τ has from about 0.7 to about 1.3 seconds value.