CN101882423A - Methods for driving electro-optic displays - Google Patents

Abstract

An electro-optic display having a plurality of pixels divided into a plurality of groups is driven by selecting each of the plurality of groups of pixels in succession and applying to each of the pixels in the selected group either a drive voltage or a non-drive voltage, the scanning of all the groups of pixels being completed in a first frame period; repeating the scanning of the groups of pixels during a second frame period, and interrupting the scanning of the groups of pixels during a pause period between the first and second frame periods, this pause period being not longer than the first or second frame period.

Description

Drive the method that electro-optic displays is used

The application's denomination of invention that to be applicant E Ink Corp. submit on Dec 28th, 2005 is divided an application for the dividing an application of the Chinese patent application No.200480018385.9 of " driving the method that electro-optic displays is used " (submitted on March 31st, 2008, application number be 200810088490X).

The present invention relates to drive the method that electro-optic displays is used.Method of the present invention especially, although be not, the bistable electrophoretic display device (EPD) designs in order to drive.

The application's book is closely related with international patent application book PCT/US02/37241 (notification number WO03/044765) and PCT/US2004/10091, and following description will suppose that the reader is familiar with the content of these documents.

When term " electric light " is used in material or display, here use with its traditional meaning at imaging technique, refer to a kind of material with first and second different at least one optical characteristics show states, by applying electric field to this material, this material is changed into its second show state from its first show state.Although this optical characteristics generally is the appreciable color of human eye, but it can be another optical characteristics, such as light transmission, reflectance, luminous or under the situation of the demonstration that designs for the machine reading, the pseudo-color on the meaning that the electromagnetic wavelength reflectance that exceeds visible range changes.

Term " gray states " here uses with its traditional meaning at imaging technique, is meant the intermediateness between two extreme optical state of pixel, means that not necessarily Hei-the Bai between these two extremities changes.For example, several patents and disclosed application for patent relate to the electrophoretic display device (EPD) that describes below, and wherein this extremity is white and dark blue, so middle " gray states " is actually light blue.Really, just as already noted, the transformation between these two extremities may not be a color change.

Term " bistable " and " bistable state " are used on the traditional sense of imaging technique here, be meant and comprise that its display element has the display of first and second different at least one optical characteristics show states, after making that any given element is driven by the addressing pulse with a limited duration, just get its first or its second show state, after addressing pulse finishes, this state will continue to change several times at least of minimum length in time of the desired addressing pulse of state of this display element, for example at least four times.Show at international patent application book WO 02/079869, some electrophoretic display device (EPD) based on particle can have not only that gray scale is stable under its extremely black and white state, and also be stable in Intermediate grey states, the electro-optic displays situation of some other type also is like this.Such display can suitably be called " multistable ", rather than bistable, although for simplicity, term " bistable " here can make and be used for both containing the bistable demonstration, contains multistable demonstration again.

Term " pulse " here uses with its traditional meaning at imaging technique, refers to the integration of voltage to the time.But some bistable electro-optical medium plays the electric charge transmitter, thereby adopts such medium, can use one of pulse to replace definition, is exactly electric current to the integration of time (equal applied total electrical charge).The suitable definition of pulse should depend on that this medium has been a voltage time pulse transducer, or the effect of charge pulse transducer.

As described at above-mentioned WO 03/044765 and PCT/US2004/10091, the electro-optic displays of known several types for example rotates the Double-color film type, for example, and as U.S. Patent No. 5,808,783; 5,777,782; 5,760,761; 6,054,071; 6,055,091; 6,097,531; 6,128,124; 6,137,467; With 6,147,791 described and electrochromism types; For example see people such as O ' Regan, B., Nature 1991,353, and 737; And Wood, D., InformationDisplay, the article of 18 (3), 24 (March 2002).Other sees Bach, the Adv.Mater. that the people showed such as U., 2002,14 (11), 845.Again for example, U.S. Patent No. 6,3019038, international patent application is announced No.WO 01/27690 and also describe this Nanochromic film in U.S. Patent application book 2003/0214695.

Become the electro-optic displays of the another kind of type of nervous for many years research and development object, be based on the electrophoretic display device (EPD) of particle.Manyly yield Massachusetts Institute of Technology (MIT) (MIT) and E.InkCorporation (company) or described such display with its patent and the application form of name application; For example, see U.S. Patent No. 5,930,026; 5,961,804; 6,017,584; 6,067,185; 6,118,426; 6,120,588; 6,120,839; 6,124,851; 6,130,773; 6,130,774; 6,172,798; 6,177,921; 6,232,950; 6,249,721; 6,252,564; 6,262,706; 6,262,833; 6,300,932; 6,312,304; 6,312,971; 6,323,989; 6,327,072; 6,376,828; 6,377,387; 6,392,785; 6,392,786; 6,413,790; 6,422,687; 6,445,374; 6,445,489; 6,459,418; 6,473,072; 6,480,182; 6,498,114; 6,504,524; 6,506,438; 6,512,354; 6,515,649; 6,518,949; 6,521,489; 6,531,997; 6,535,197; 6,538,801; 6,545,291; 6,580,545; 6,639,578; 6,652,075; 6,657,772; 6,664,944; 6,680,725; 6,683,333; 6,704,133; 6,710,540; 6,721,083; 6,724,519; With 6,727,881; With U.S. Patent application bulletin 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; 2003/0102858; 2003/0132908; 2003/0137521; 2003/0137717; 2003/0151702; 2003/0189749; 2003/0214695; 2003/0214697; 2003/0222315; 2004/0008398; 2004/0012839; 2004/0014265; 2004/0027327; 2004/0075634; With 2004/0094422; With international patent application bulletin No.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; WO 03/092077; WO 03/107315; WO 2004/017035; And WO2004/023202.

Many above-mentioned patents and application form are all recognized, the wall that centers on discrete micro-capsule in the entrapped electrophoretic medium can replace with an external phase, thereby produce a what is called " polymer-dispersed electrophoretic display ", wherein this electrophoretic medium comprises a plurality of discrete electrophoresis droplets and the external phase of a polymeric material, and discrete electrophoresis droplet can be regarded as capsule or micro-capsule in such polymer-dispersed electrophoretic display, although the capsule film that interrelates with each each droplet not; For example, see above-mentioned 2002/0131147.Correspondingly, for the purpose of the application's book, such polymer-dispersed electrophoretic media is counted as the subclass of sealing electrophoretic medium.

The electrophoretic display device (EPD) of relevant type also claims " microcell electrophoretic display ".In a microcell electrophoretic display, charged particle and suspension liquid are not to be encapsulated in the capsule, but remain on mounting medium, generally are in a plurality of holes that form in the thin polymer film.For example, see international patent application bulletin No.WO 02/01281 and U.S. Patent application bulletin No.2002/0075556, both all yield SipixImaging, Inc. (company).

Although electrophoretic medium often opaque (because, for example, in many electrophoretic mediums, particle is block visible light transmission display device basically), and operate under the reflective-mode, many electrophoretic display device (EPD)s are operated under the what is called " shutter mode ", and one of them show state is opaque basically, and another is a printing opacity.For example, see above-mentioned U.S. Patent No. 6,130,774 and 6,172,798 and U.S. Patent No. 5,872,552; 6,144,361; 6,271,823; 6,225,971; With 6,184,856.Be similar to electrophoretic display device (EPD), but dielectrophoresis (Dielectrophoretic) display that depends on the electric field intensity variation may operate under the similar pattern; See U.S. Patent No. 4,418,346.The electro-optic displays of other type also may be operated under the shutter mode.

Bistable or multistable variation characteristic based on the electrophoretic display device (EPD) of particle, and other electro-optic displays that present similar variation characteristic (for simplicity, such display can be called " pulsed drive display " hereinafter), with traditional liquid crystal (" LC) display forms distinct contrast.Twisted nematic liquid crystals does not play bistable or multistable effect, but plays voltage transmitter, so apply given electric field for the pixel of such display, just produces a specific gray scale on this pixel, and the gray scale that presented in the past with this pixel is irrelevant.In addition, the LC display only drives in one direction and (from opaque or " secretly " to transparent or " bright "), carries out from brighter state-transition to darker state by reducing or eliminating this electric field.At last, the gray scale of LC display picture element is insensitive to the polarity of electric field, and only to its amplitude sensitivity, really, owing to technical reason, the merchant sells the generally polarity of upset driving electric field on frequent interval time of LC display.Otherwise bistable electro-optic displays is said like recently, plays the pulse transmitter, the electric field that makes the final state of a pixel not only depend on to be applied with apply the time of this electric field, and depend on this electric field state of this pixel before that applies.

May at first can expect, tackle a kind of like this Perfected process of pulsed drive electro-optic displays, to be so-called " general gray scale image stream ", its middle controller is an image of configuration write each time like this, makes each pixel directly be converted to its last gray scale from its initial gray scale.But, on a pulsed drive display, write image and have some error inevitably.The such error of some that runs into comprises in practice:

(a) original state dependence; For some electro-optical medium at least, make pixel switch to a desired pulse of new optical states and not only depend on the optical states of electric current and requirement, and depend on optical states before this pixel.

(b) residence time dependence; For some electro-optical medium at least, pixel is switched to a desired pulse of new optical states depend on that this pixel is in time that its different optical states has been spent.This dependent precise nature is still very not clear, but in general, this pixel is long more in its current optical states residence time, just requires many more pulses.

(c) temperature dependency; Pixel is switched to a desired pulse of new optical states seriously depend on temperature.

(d) humidity dependence; For the electro-optical medium of some type at least, pixel is switched to the humidity of a desired pulse of new optical states around depending on.

(e) mechanical homogeneity; Pixel is switched to the influence that a desired pulse of new optical states can be subjected to the mechanical outflow of population in this display, for example the influence of change of the thickness of electro-optical medium or relevant lamination cementing agent.The unevenness of the machinery of other type may be owing to inevitably change, make franchise and material between the different manufacturing of medium batch and change and cause.

(f) voltage error; The actual pulse that is applied to pixel will be inevitably be different from the pulse that applies in theory slightly because on the voltage that driver provides inevitable some error slightly.

As described at above-mentioned WO 03/044765 and PCT/US2004/10091, the problem that general gray scale image stream has " accumulation of error " phenomenon to cause, on the image of some type, it may produce the gray-scale deviation that general viewers can be discovered.This accumulation of error phenomenon is applicable to all types of errors of listing above.As above-mentioned 2003/0137521 described, it is possible compensating such error, but just on a limited accuracy.Thereby, general gray scale image stream will draw good result, and very accurate control must be arranged the pulse that is applied, and has been found that according to experience, under present state of the art, it is infeasible that general gray scale image stream is sold on the display the merchant at electro-optic displays.

Nearly all electro-optical medium all has built-in resetting (error limitation) mechanism, and in other words, their extreme (general black and white) optical states plays " optics fence ".A specific pulse is applied to after the pixel of electro-optic displays, this pixel can't become whiter (or more black).For example, seal in the electrophoretic display device (EPD) at one, apply after the specific pulse, all electrophoresis particle all is forced to withstand each other or head on capsule wall, can't move again, thereby, produce a restrictive optical states or optics fence.Because in such medium, there are electrophoretic particles size and CHARGE DISTRIBUTION, some particle was met this fence before other particles, set up " soft fence " phenomenon, therefore when the last optical states of a transformation during near black and white extremity, reduced desired pulse degree of accuracy, thereby when the last optical states that changes near should be extreme black with in vain during state, desired optics degree of accuracy reduces, and when the terminal point that changes during near the optical range of this pixel middle, desired optics degree of accuracy is increased sharply.

The dissimilar drive scheme that utilizes the optics fence that the known electric optical display unit is used.For example, Fig. 9 of above-mentioned WO 03/044765 with 10 with relevant description, a kind of " showing slides " drive scheme has been described, wherein writing before any new image, whole display is driven to two optics fences.The drive scheme of showing slides like this produces gray scale accurately, and when still it being driven into the optics fence, the flicker of display makes the beholder vexed.The someone advises (seeing U.S. Patent No. 6,531,997), adopts a similar drive scheme, and wherein the pixel of having only its optical states to change in this new image just is driven to this optics fence.But, " limited showing slides " drive scheme of the type, if any, even more make the beholder vexed, because the integral body (solid) of the common drive scheme of showing slides flicker depended on the flicker of image and replaced, wherein write new image with forth screen on the feature of old image and new image with opposite chromatic flicker.

Obviously, gray scale image stream drive scheme can not look to utilizing this optics fence to avoid gamma error as single, because any given pixel all may experience the infinitely-great change of number on gray scale in a such drive scheme, and does not touch any optics fence.

In one aspect, the present invention makes every effort to be provided at and reaches the method that gray-scale Control is used on the electro-optic displays, and it reaches and is similar to the stable of the gray scale that drive scheme reached of showing slides, but the flicker problem that makes one nervous of the drive scheme of not showing slides.Preferable methods of the present invention can give one of beholder be similar to single as the visual experience that drive scheme provided of gray scale image stream.

In other respects, the present invention makes every effort to be provided at the method that reaches the meticulous control of gray scale in the display that is driven by width modulation.

Have the bistable electro-optical medium so that when writing the Active Matrix Display of gray scale image thereon when driving one, apply the pulsed quantity of a precision preferably can for each pixel, so that reach the accurate control of shown gray scale.Used driving method can rely on the modulation of " width " (duration) of the modulation that is applied to the voltage on each pixel and/or the voltage that applies.Because the power supply cost that the voltage modulated driver is relevant with them is higher relatively, and width modulation is commercial attractive.But in scanning process of the Active Matrix Display that utilizes such width modulation, traditional driving circuit only allows to apply a single voltage for any given pixel in any one scanning process of this matrix.Thereby the width modulation of Active Matrix Display drives to be undertaken by repeatedly scanning this matrix, depends on the change that specific pixel requires at zero degree, the driving voltage that several times or all applies in the scanning process on gray scale.Scanning each time can be regarded a frame drive waveforms as, and complete addressing pulse is a superframe that is formed by a plurality of frames in succession.Should be noted that, in each scanning process for the row address time, although driving voltage only is applied on any specific pixel electrode, but in the time course between the selection in succession with delegation, this driving voltage maintains on this pixel electrode, only slowly decay makes this pixel being driven between the selection in succession with delegation.

Just as already noted, each provisional capital of this matrix needs indivedual selecting in each frame process, makes that frame rate can't be above about 50 to 100Hz in practice for high resolution display (for example, 800 * 600 pixel display); Thereby each frame generally continues 10 to 20ms.The frame of this length cause being difficult to meticulous control example that electro-optical medium to many quick switchings carries out gray scale as, some is sealed electrophoretic medium and finish once switching basically between their extreme optical state (once change about 30L* unit) in about 100ms, and moves for the frame of a 20ms of the such medium gray scale corresponding to about 6L* unit.Like this one moves is too big for the accurate control of gray scale; Human eye is to about 1L* unit gray difference sensitivity, and only being equivalent to this pulse of control on the scale of 6L* unit, causes visible distortion probably, " ghost image " that causes such as the original state dependence of this electro-optical medium.More particularly, may experience ghost image, because as discussed, in some above-mentioned patents and application form, the change of the pulse gray scale that applies is not linear, and any specific gray scale changes needed overall pulse and may change along with the time that applies pulse and middle gray scale.For example, in simple 4 gray scales (2 a) display with gray scale 0 (deceiving), 1 (dark gray), 2 (bright gray scale) and 3 (in vain), drive by a simple width modulation drive scheme, nominally change the gray scale that is reached afterwards nominally these non-linear gray scales that may cause 0-2 to change the reality that is reached afterwards are different from 1-2, produce extremely undesirable vision distortion simultaneously.The invention provides the method that in the display that drives by width modulation, reaches the meticulous control usefulness of gray scale, thereby, the problems referred to above avoided.

Correspondingly, in one aspect, the invention provides a kind of driving and have at least one pixel, can reach any one at least four different gray scales, comprise the electro-optic displays of two extreme optical state.This method comprises:

On this display, show first image; With

Rewrite this display, so that show second image thereon,

Wherein, in the process that rewrites this display, number of transitions surpasses any pixel of a predetermined numerical value, this predetermined value is one at least, and do not touch extreme optical state, this pixel drive in this second image before its last optical states, be driven at least one extreme optical state.

For simplicity, this method can be called " limited transformation method " of the present invention.

In a form of this limited transformation method, the rewriting of display is carried out like this, in case make pixel be driven to opposite extreme optical state from an extreme optical state by the pulse of a polarity, before reaching opposite extreme optical state, this pixel does not just receive the pulse of opposite polarity.

In addition, in this limited transformation method, predetermined value (predetermined number of transitions) is not more than N/2, and wherein N is that a pixel can the gray-scale displayed sum.This limited transformation method can utilize three grades of drivers to carry out, that is the rewriting of display can apply voltage-V by giving this pixel or each pixel, 0 and+among the V any one or more than carry out.In addition, this limited transformation method can be the DC balance, that is the rewriting of this display can be carried out like this, makes that impressed voltage is a bounded to the integration of time for any transformation series that pixel stood.

Limited transformation method of the present invention, the rewriting of this display can be carried out like this, makes to be applied to the initial and last gray scale that this transformation is only depended in a pulse on the pixel in a transition process.As another program, this method can be designed to consider other state of this display, as described in greater detail below.In a preferred form,, be applied to the pulse of the following form of this pixel one sequence in this limited transformation method at least one transformation that at least one pixel stood from gray scale R2 to gray scale R1:

TM(R1，R2)IP(R1)-IP(R2)TH(R1，R2)

Wherein " IP (Rx) " representative all has the correlation values of the pulse electromotive force matrix of a numerical value from one for each gray scale, and TM (R1, R2) combination all has the correlation values of the transition matrix of a numerical value for each R1/R2 from one in representative.(for simplicity, the pulse train of the type can be abbreviated as " x/ Δ IP/x " sequence hereinafter.) such-x/ Δ IP/x sequence can be applied to the wherein initial whole transformations different with last gray scale.In addition, in such-x/IP/x sequence, it is over half that last " x " section can take maximum update time.This TM (R1, R2) or the x value can select like this, make the symbol of each numerical value only depend on R1; Specifically, for one or more bright gray scales, these values can be just to be chosen as, and are chosen as negatively for one or more dark gray, make gray scale beyond two extreme optical state near the direction convergence of extreme optical state.

Above-mentioned-x/ Δ IP/x sequence can comprise additional pulse.Specifically, such sequence can comprise the pulse of additional a pair of [+y] [y] form, and wherein y is the pulse value of negative or positive, should [+y] and [y] pulse insertion-x/ Δ IP/x sequence.This sequence can also comprise the pulse of second a pair of [+z] [z] form of adding, and wherein z is a pulse value that is different from y, and can be negative or positive, should [+z] and [z] pulse insertion-x/ Δ IP/x sequence.Should-x/ Δ IP/x sequence can also comprise that a no-voltage puts on the cycle of this pixel.Should " no-voltage " cycle can appear at this-two elements of x/ Δ IP/x sequence between, or in its single element.Should-x/ Δ IP/x sequence can comprise two or more " the no-voltage cycle.

Utilize above-mentioned-during x/ Δ IP/x sequence, this display can comprise and is divided into a plurality of pixels of a plurality of groups, and this transformation can be undertaken by following steps: (a) select each in a plurality of phase pixel groups, and to each pixel in this selected group, be not that to apply driving voltage just be non-driving voltage, the scanning of all pixel groups is all finished in first frame period; (b) in the second frame period process, repeat the scanning of this pixel groups; (c) interrupt the scanning of this pixel groups in the pause period process between this first and second frame period, this pause period is long unlike the one the second the second frame periods.

In this limited transformation method, the rewriting of this display can be carried out like this, makes always to be undertaken by one of same polarity last pulse to the transformation of a given gray scale.Specifically, two extreme optical state gray scale in addition can be from the direction convergence of more approaching extreme optical state.

The present invention also provides a method that drives electro-optic displays, and this electro-optic displays has a plurality of pixels that are divided into many groups.This method comprises:

(a) each in a plurality of pixel groups in succession of selection, and to the every pixel in the selected group, be not to apply driving voltage, applying non-driving voltage exactly, the scanning of all pixel groups is all finished in first frame period;

(b) in the second frame period process, repeat the scanning of this pixel groups; With

(c) in the pause period process between first and second frame periods, interrupt the scanning of this pixel groups, this pause period is no longer than first or second frame period.

For simplicity, this method can be called " interrupt scanning " of the present invention method hereinafter.

In such interrupt scanning method, the general first and second frame period equal in length.The length of this pause period can be the part (sub-multiple) of a length in first and second frame periods.This interrupt scanning method can comprise a plurality of pause period; Thereby this method can be included at least scanning element group in first, second and the 3rd frame period process, and interrupts the scanning of pixel groups between the frame period in succession at least in the first and second pause period processes.This first, second and the 3rd frame period can be equal in length basically, and the total length of each pause period equals a frame period or a frame period deducts a pause period.Generally, in this interrupt scanning method, this pixel is arranged in the matrix with a plurality of row and a plurality of row, and wherein each pixel is all by the intersection point definition of a given row and given row, and each group pixel comprises the delegation or row of this matrix.This interrupt scanning method is the DC balance preferably, that is the scanning of this display is preferably carried out like this, makes that impressed voltage is bounded to the integration of time for the transformation of any series that pixel stood.

In other respects, the invention provides a method, in order to driving an electro-optic displays with a plurality of pixels, this pixel is with driving to the pulse-width modulation waveform that each pixel applies a plurality of different pulses.This method comprises:

(a) storage indication applies a given pulse for a pixel whether to produce one and be higher or lower than data that require the gray scale of gray scale;

(b) detect when two neighbors all require same gray scale; With

(c) regulate the pulse that is applied to these two pixels, make a pixel be lower than the gray scale of requirement, and one other pixel is higher than the requirement gray scale simultaneously.

For simplicity, this method can be called " balance gray level method " of the present invention hereinafter.

In the method, pixel can be divided into two groups, makes each pixel all have the neighbours of at least one opposite group, and these two groups are used different drive schemes.

As above-described, each method of the present invention can be applied to the electro-optical medium of any one the above-mentioned type.Thereby method of the present invention can be used with the electro-optic displays that comprises electrochromism or rotate double-colored film electro-optical medium, entrapped electrophoretic medium or microcell electrophoretic medium.Also can use the electro-optical medium of other type.

Figure 1A and 1B illustrate two parts of this limited transformation drive scheme of the present invention;

Fig. 2 illustrates the preferred-x/ Δ IP/x sequence that can be used for this method of the present invention;

Fig. 3 schematically illustrates waveform shown in Figure 2 and how can revise, so that comprise a pair of additional driving pulse;

Fig. 4 illustrates the waveform that changes Fig. 2 with the illustrational mode of Fig. 3 and produces a waveform;

Fig. 5 illustrates and illustrates the waveform that mode changes Fig. 2 with Fig. 3 and produce second waveform;

How the schematically routine explanation of Fig. 6 can further revise waveform shown in Figure 5 comprises a pair of additional driving pulse;

Fig. 7 illustrates and illustrates the waveform that mode changes Fig. 5 with Fig. 6 and produce a waveform;

Fig. 8-10 illustrates three modifications of waveform shown in Figure 2, so that comprise a no-voltage cycle;

From the above, obviously the present invention provides several different improvement methods on the electro-optic displays driving method.In the following description, various improvement provided by the invention generally will be described separately, although the imaging technique technical professional will be appreciated that single in practice display can utilize these main aspects more than; For example, use the display of limited transformation method of the present invention can also utilize the interrupt scanning method.In addition, because these improvement provided by the present invention can be used the method for above-mentioned WO 03/044765 and the described various driving electro-optic displays of PCT/US2004/10091, below describe basic driver method shown in WO03/044765 Fig. 1-10 and relevant description are familiar with in supposition (reader).Specifically, Fig. 9 of this application book and 10 describes so-called uncompensated n-prepulse with three root segments (n-PP SS) waveform of showing slides.At first, this pixel is erased to a uniform optical states, generally be not white be exactly black.Then, generally white again and black between two optical states, come and go and drive this pixel.At last, make this pixel be in a new optical states, it can be one of several gray states.This last (or writing) pulse is called addressing pulse, and other pulses (this first (or wiping) pulse and middle (or blank) pulse) collectively are called prepulse.

A major defect of the type waveform is it has large amplitude between several images a optical flicker.This can be by making the renewal sequence move the superframe time of half usefulness of pixel and improving with the high resolving power staggered pixels, as what discussed with reference to its figure 9 and 10 at WO 0303044765.Possible pattern comprises in every line, every row or a checkerboard pattern.Notice that this does not also mean that and utilize opposite polarity, that is " from black " and " from white " is because this can cause non-coupling gray scale on adjacent pixels.But can by make NEW BEGINNING more postpone one " superframe " (one group of several frame that are equivalent to the maximum length that Hei-Bai upgrades) finish pixel half (that is, first group of pixel finished erasing pulse, when this first group of pixel began first space pulse, this second group of pixel began this erasing pulse).This will require to add the superframe of a total update time, so that allow them synchronous.

Limited transformation method of the present invention

Above-mentioned flicker problem for fear of the drive scheme shown in Fig. 9 and 10 of WO 03/044765, and the problem of the general gray scale image stream of discussing before also avoiding simultaneously, preferably according to this limited transformation method configuration driven scheme of the present invention, make any given pixel, before by an extreme optical state (black or white), can only experience the transition in grayscale of a predetermined maximum number (at least one).In fact a transformation of leaving this extreme optical state cancels any error of accumulation in the past since an accurate known optical states.In WO03/044765, carried out having discussed the different technology of the optical effect that makes pixel by extreme optical state like this (such as the flicker of display) being reduced to minimum usefulness.

Appear at the black and white flicker on the display in the reset process process of above-mentioned such drive scheme, that yes is visible to the user, and is tedious for many users.In order to reduce the visual effect of such reset process, way is easily, and the pixel of this display is divided into two (or more a plurality of) groups, and this different group is applied dissimilar reset pulses.More particularly, if must use the reset pulse of alternately deceiving and drive in vain any given pixel, way is easily, pixel is divided at least two groups, and the configuration driven scheme, it is white to make that a pixel groups is driven into, and the one other pixel group is driven into black simultaneously.Suppose the space distribution of these two groups of careful selection, and these pixels are fully little, then the user will experience this reset process as experience gray scale interval time (some slight snowflake perhaps occurring) on this display, and a such gray scale is generally generally more less horrible than a series of black and white flickers interval time.

For example, with a kind of form of such one " two groups reset " step, the pixel that odd number lists can be included into " odd number " group, and the pixel that even number lists is included into second " even number " group.Then, odd pixel can be utilized drive scheme shown in Figure 9, in the erase step process, these pixel drive to black state, and simultaneously in the erase step process, the modification that can utilize this drive scheme these pixel drive to white state.Then, two pixel groups all can stand the even number reset pulse in the reset process process, and the reset pulse that makes two groups use differs 180 degree phase places basically, and this display gray scale all occurs in whole reset process.At last, in the process that second image of this step is write, odd pixel is from the black final state that is driven into them, and the while even pixel is from being driven into their final state in vain.For guarantee each pixel all reset in the same way for a long time (thereby, this reset mode is not introduced any distortion on this display), this controller is preferably between in succession the image and switches drive scheme, make to write display that each pixel alternately writes its final state from black and white state at a series of new images.

Obviously, can use similar scheme, wherein the pixel of the row of odd-numbered forms first group, and the pixel of the row of even-numbered forms second group.In another similar drive scheme, first group of pixel that comprises odd column and odd-numbered line and even column and even number line, and second group comprise odd column and even number line and even column and odd-numbered line, makes these two groups to be arranged to the chessboard mode.

Replace (or except) pixel be divided into two groups, and one group to differ 180 degree phase configuration reset pulses with another group, can be divided into the group that uses different reset process to these pixels, different on the number of pulse and frequency.For example, one group can be with six pulsed reset sequences, and the similar sequence of the second group of pulse that can use to have 12 these frequencies of twice simultaneously.In a meticulousr scheme, pixel can be divided into four groups, utilizes six pulse schemes for first and second groups, and phase place differs 180 degree each other, and simultaneously third and fourth group use 12 pulse schemes, but phase place differs 180 degree each other.

According to limited transformation method of the present invention, another method of dwindling the flicker problem can utilize such drive scheme to carry out, and allows any one given to be assumed to non-zero but the gray states number was limited in succession in the past touching an optics fence.In a such drive scheme, when rewriting display so that when showing a new image thereon, any one has stood the pixel that number of transitions surpasses predetermined value and do not touch an extreme optical state, be driven in this pixel before its last optical states, be driven at least one extreme optical state.In a preferred form of a such drive scheme, the pixel that is driven to an extreme optical state is driven to the more approaching extreme optical state of its gray scale after this transformation, supposes that certainly this requires optical states is not one of extreme optical state.In addition, utilize in the foregoing preferred form of looking into the drive scheme of table at such one, the transformation maximum times that pixel is allowed to stand under the situation of not touching optics fence (extreme optical state) is provided with to such an extent that equal the number of the previous optical states considered at this transition matrix; Such method does not require extra steering logic or storer.

The driving method that touches optics fence restriction transformation before maximum times needn't increase the used time of rewriting of finishing this display significantly.For example, investigate the display of four gray shade scales (2), one of them is from vain to black transformation or will make general gray scale image flow drive scheme and will rewrite display fully with this time with 200 milliseconds on the contrary.Changing the unique situation that needs to revise on a such display is when pixel repeats to switch between two central gray scales.If the number of transitions that a such pixel is switched between two central gray scales surpasses this predetermined number, then this limited transformation method of the present invention requires this next one switching to be undertaken by optics fence (extreme optical state).Have been found that under such a case forwarding the optics fence to needs 70 milliseconds, and forwarding this gray scale to and will make total fringe time approximately have only 200 milliseconds with about 13 milliseconds afterwards simultaneously.Thereby this limited transformation method is compared with general gray scale image stream, needn't prolong fringe time fully.

Now a limited transformation driving method that reduces the tedious influence of reset process is described with reference to Figure 1A and 1B.In this scheme, these pixels are divided into two groups again, and first (even number) organized according to the drive scheme shown in Figure 1A, and this second (odd number) group is according to the drive scheme shown in Figure 1B.In addition, in this scheme, black and white middle whole gray scales are divided into the adjacent dark gray of the black grade of first group of vicinity, and the adjacent bright gray shade scale of second group of contiguous white grade is divided the same with two pixel groups like this.Best, but be not important, in these two groups, the same number of gray shade scale is arranged; If have odd number gray shade scale, then central grade can give any one group arbitrarily.For the ease of illustrating, Figure 1A and 1B display application are in the drive scheme of one eight grade gray-scale monitor, and these grades were denoted as for 0 (deceiving) to 7 (in vain); Gray shade scale 1,2 and 3 is dark gray levels, and gray shade scale 4,5 and 6 is bright gray shade scales.

In Figure 1A and 1B graphics driver scheme, gray scale to the transformation of gray scale according to following rule treatments:

(a) in the first even pixel group, in turning to the process of dark gray levels, the final pulse that is applied always tend to white pulse (that is, its polarity trends towards driving black state shift its white state of this pixel from it), yet in the transformation that turns to bright gray scale, the final pulse that is applied always tends to the pulse of deceiving;

(b) in the second odd pixel group, in turning to the dark gray levels process, the final pulse that is applied always tends to the pulse of deceiving, and in the transformation that turns to bright gray shade scale, the final pulse that is applied always tends to white pulse;

(c) in all cases, reached after the white state, the black pulse of trend is only with after the white pulse of trend, and reached after the black state, and the white pulse of trend is only with after the black pulse of trend; With

(d) even pixel cannot drive to black from a dark gray levels with the black pulse of a single trend, odd pixel also cannot be with the white pulse of single trend from a bright gray shade scale to white driving.

(obviously, in all cases, white state to utilize the white pulse of last trend to reach, reaches with the pulse that utilizes last trend to deceive and deceive state only only.)

Using these rules is utilized maximum three pulses in succession to carry out with regard to making each gray scale to the transformation of gray scale.For example, Figure 1A represents that even pixel stands the transformation from black (grade 0) to gray shade scale 1.This is to utilize to be denoted as 1102 the white pulse (representing with the positive gradient among Figure 1A certainly) of single trend and to reach.Then, this pixel drive to gray shade scale 3.Because gray shade scale 3 is dark gray levels, according to rule (a), must reach, thereby grade 1/ grade 3 changes and can handle by the white pulse 1104 of single trend by the white pulse of a trend, it has the pulse that is different from pulse 1102.

This pixel is driven to gray shade scale 6 now.Because this is a bright gray shade scale, it must reach by a black pulse of trend by rule (a).Correspondingly, application rule (a) and (c) calling hierarchy 3/ class 6 change and to be undertaken by two pulse trains, in other words, the white pulse 1106 of first trend, its drives pixel and bleaches (grade 7), one second black pulse 1108 of trend of heel, and it drives this pixel from grade 7 to calling hierarchy 6.

Then, this pixel drive to gray shade scale 4.Because this is a bright gray shade scale, to be undertaken by a used parameter of transformation that just is similar to grade 1/ grade 3 of early stage discussion, the transformation of this grade 6/ class 4 is undertaken by the black pulse 1110 of a single trend.The next transformation is to grade 3.Because this is a dark gray levels, undertaken by a used parameter of transformation that just is similar to grade 3/ class 6, the transformation of this grade 4/ grade 3 is handled by two pulse trains, in other words, the black pulse 1112 of first trend, to black (grade 0), one second of heel tends to white pulse 1114 this pixel drive for it, and it is driven into this pixel the grade 3 of requirement from grade 0.

Last transformation shown in Figure 1A is from grade 3 to grade 1.Because grade 1 is a dark gray levels, it must come convergence by tending to white pulse according to rule (a).Correspondingly, application rule (a) and (c), the transformation of this grade 3/ grade 1 must be handled by three pulse trains, comprise drive this pixel to first trend of white (grade 0) white 1116, drive this pixel and tend to white pulse 1120 from deceiving the 3rd of grade 1 state that requires to second trend of black (grade 7) black 1118 and this pixel of driving.

Figure 1B represents that odd pixel carries out same 0-1-3-6-4-3-1 gray states sequence, as the even pixel of Figure 1A.But, will find out that employed pulse train is very different.1, one dark gray levels of rule (b) calling hierarchy is by the pulse convergence that tends to deceive.Thereby it is to carry out to the white pulse 1122 of first trend of white (grade 7) by driving this pixel that this 0-1 changes, and one of heel drives the black pulse 1124 of the trend of this pixel from grade 7 to the grade 1 that requires.This 1-3 changes and requires three pulse trains, and one drives this pixel and drives this pixel to the black pulse of first trend of black (grade 0) 1126, one and drive 3 the black pulse 1130 of the 3rd trend from grade 7 to calling hierarchy of this pixel to the white pulse 1128 of second trend of white (grade 7) and one.It is to class 6 that this next one changes, this is a bright gray shade scale, according to rule (b), by a pulse convergence that trend is white, this grade 3/ class 6 changes and is undertaken by two pulse trains, comprise one drive this pixel to the black pulse of the trend of black (grade 0) 1132, this pixel of driving to the white pulse 1134 of the trend of the class 6 that requires.This grade 6/ class 4 changes and is undertaken by three pulse trains, in other words, one drives this pixel and drives pulse 1138 that this pixel deceives to the trend of black (grade 0) and this pixel of driving to the white pulse 1140 of the trend of the class 4 that requires to the white pulse of white (grade 7) trend 1136, one.The transformation of this grade 4/ grade 3 is undertaken by two pulse trains, comprises a white pulse 1142 of trend that drives this pixel to white (grade 7), and one of heel drives this pixel to the black pulse 1144 of the trend of the grade 3 that requires.At last, the transformation of grade 3/ grade 1 is to be undertaken by the black pulse 1146 of a single trend.

Will find out from Figure 1A and 1B, this drive scheme guarantees that each pixel follows a saw tooth pattern, wherein this pixel from black forward to white, and do not change direction (obviously, although this pixel can rest on one section weak point of any middle gray grade or long during), and after this black from forwarding in vain, and do not change direction.Thereby, top rule (c) and (d) can be to replace with following single rule (e):

(e) in case pixel by the pulse of a polarity from an extreme optical state (that is, white or black) drive to opposite extreme optical state, this pixel just cannot receive the pulse of opposite polarity, till it has reached above-mentioned opposite extreme optical state.

Thereby this drive scheme is one " fence is stablized gray scale " i.e. " RSGS " drive scheme.A RSGS drive scheme like this is special circumstances of limited transformation drive scheme, it guarantees that a pixel is at most only with the transformation of the number of transitions that stands to equal N/2 (or (N-1)/2) more precisely, wherein N is can the gray-scale displayed total number of grades, and does not require to change by an optics fence and take place.A drive scheme is like this avoided each slight errors in changing (for example, the voltage that applied by driver inevitably less fluctuation causes), infinite accumulation in face of the serious distortion of gray scale image appears at the observer till.In addition, this drive scheme designs like this, makes even number and odd pixel always from given middle gray of opposite direction convergence, that is in one case, the last pulse of this sequence is the white pulse of trend, and in another case, be the black pulse of trend.The even number and the odd pixel of equal number write a single gray shade scale if most of zone of this display comprises basically, and then " reverse direction " feature reduces to minimum to the flicker in this zone.

Those reasons owing to the drive scheme that relates to other above being similar to is discussed when realizing Figure 1A and 1B sawtooth drive scheme, are divided into two discrete groups to pixel, should carefully note the layout of pixel in even number and the odd number group.This configuration will guarantee best that any continuous basically display area all will comprise the odd and even number pixel of equal number basically, and the full-size of same group of continuous pixels piece is fully little, and general viewers is difficult for discovering.Just as already discussed, the configuration of the checkerboard pattern of two pixel groups meets these requirements.In addition, the random screen technology can be used for disposing the pixel of these two groups.

But in this sawtooth drive scheme, the use of checkerboard pattern often increases the energy consumption of display.Any given row at a such pattern, neighbor will belong to opposite group, and whole therein pixels all stand the sizable continuum of same transition in grayscale (one is not abnormal situation) size, and adjacent pixels will often require opposite polarity pulse in any given time.Apply opposite polarity pulse any listing, when whenever writing a newline, require row electrode (source electrode) discharge and charging again this display to the pixel that occurs in succession.In the driving of Active Matrix Display, to the row electrode discharge and again the charging be the principal element of a display energy consumption, this is well-known to the technician.Thereby checkerboard is arranged the energy consumption that often increases display.

Energy consumption and avoid between the hope in the big zone of continuous pixels on the same group one rationally compromise be to give rectangle to each group pixel, pixel wherein is positioned at same row all, but stretches several pixels along these row.Adopt such layout, when rewriting has same gray shade scale regional, have only when when a rectangle moves on to next rectangle, just must be to row electrode discharge and charging again.Rectangle is 1 * 4 pixel preferably, and disposes to such an extent that the rectangle in the adjacent column is not finishing with delegation, that is the rectangle in the adjacent column has difference " phase place ".Rectangle in each row is given each phase place and can be carried out randomly or in a looping fashion.

An advantage of the sawtooth drive scheme shown in Figure 1A and the 1B is that the zone of any monochrome of this image is all upgraded with single pulse simply, is not black in white, is exactly white to black, as the overall part of upgrading of this display.Rewrite so used maximum duration of monochromatic areas and be gray scale and rewrite half of required maximum duration to the desired zone of transition in grayscale, and this feature can advantageously be used for promptly upgrading image feature, such as user's character input, pull-down menu etc.Controller can check whether the requirement of an image requires the transformation of gray scale to gray scale; If do not require, the imagery zone that then needs to rewrite can utilize this more new model rewriting of monochrome rapidly.Thereby character, pull-down menu and other user interaction features of the input that the user can this display of fast updating seamlessly overlap in the slower renewal of general gray scale image.

A limited transformation drive scheme not necessarily requires usage counter to measure the number of transitions that each pixel stood of display, and do not hinder the use of drive scheme (such as the circulation RSGS drive scheme of having described) with reference to Figure 1A and 1B, even the latter does not reach predetermined number of transitions as yet, just require some to change and take place, suppose that the algorithm that definite mode of carrying out that changes is used does not allow any pixel to stand more than the transformation of pre-determined number not touch the optics fence by the optics fence.In addition, will appreciate that, needn't all carry out by every rewriting primary display image in the number of transitions that the next given pixel of the situation of not touching the optics fence stands, especially at display with frequent interval time more under the news.For example, this inspection can only just be carried out when alternately upgrading, and supposes that whole pixels are not to surpass predetermined number of transitions, and next exactly renewal may surpass this number after being driven to the optics fence.

Another preferred limited transformation method of the present invention now will be described, although just in illustrational mode.This preferable methods is used for moving four gray shade scales (2) Active Matrix Display, and its uses an initial and last gray shade scale (indicating " R2 " and " R1 " respectively) of only considering the transformation that will carry out and the transition matrix of the state formerly not considering to add.This display controller is three grade width modulation (PWM) controllers, can apply-V to each pixel electrode with respect to the public preceding termination electrode that remains on 0 (level), 0 or+V.

This display controller comprises two RAM image buffer zones.A buffer zone (" A ") is stored image current on this display.Generally, this controller is in park mode, preserves data and make this display driver keep non-activation in RAM.The bistable state of this electro-optical medium is preserved image same on this display.When receiving the image update command, this controller is new image this second buffer zone (" B ") of packing into.Then, according to the last state R1 (from buffer zone " B ") of this pixel request and current, the initial state R2 (from buffer zone " A ") of each pixel, for each pixel of this display, this controller is all checked (in flash memory) multiframe drive waveforms.

Data set in this flash file is made into a three-dimensional magnitude of voltage V (R1, R2, frame) array, wherein each all is the integer of from 1 to 4 (corresponding with four available gray shade scales) as the R1 that has shown and R2, and " frame " is the number of frame, that is, the number of associated frame in being used for the superframe of each transformation.Generally, superframe can be 1 second long, simultaneously each frame takies 20ms, makes that the number of frame can be in 1 to 50 scope.Thereby this array has 4 * 4 * 50=800 item.Because each in the array all must can be represented this magnitude of voltage-V, 0 and+any one of V, so generally store each magnitude of voltage (array of values) with two.

Very obvious, because each 800 array item can have these three possible magnitudes of voltage any one, thus have a possible array (waveform) that number is huge, can't exhaustive search to such an extent as to number is too big.In theory, have 3 ⁸⁰⁰Or about 5 * 10 ³⁸¹Individual possible array; Because universe has 1078 atoms approximately, people's mean lifetime has 10 ⁹Second, virtual rating has 200 orders of magnitude at least, can't exhaustive search.Fortunately, existing knowledge, the especially needs of DC balance it on about the electro-optic displays variation characteristic force to add additional constraint and allow best or be limited in the feasible scope near the search of the waveform of the best for possible waveform.

As what discussed at above-mentioned U.S. Patent No. 6,504,524 and 6,531,997 and above-mentioned WO03/044765, known major part, if not all, electro-optical medium requires DC current (DC) balanced waveform, otherwise just injurious effects may occur.When using unbalance DC waveform, such influence can comprise the long term drift of the damage of electrode and the gray states in the scope of several L* units (cycle was above one hour).Therefore, it seems whenever making every effort to use the scheme of DC balance drive waveforms all should think thrice before acting.

May can expect at first that from the above such DC balancing method may be to be beyond one's reach, because any specific gray scale is passed through the pulse of this pixel so that electric current is constant basically to the transformation of gray scale is needed.But, say like this is just nearest and be only really, and have been found that by experience, at least under the situation based on the electrophoretic medium (other electro-optical medium too) of particle, the effect of pulse that applies 50 milliseconds at five intervals to a pixel is inequality with 250 milliseconds of pulses that apply same voltage.Correspondingly, some dirigibility is arranged flowing through on the electric current that a pixel reaches given transformation, and this dirigibility can be used for assisting to reach the DC balance.For example, this looks into a plurality of pulses that can store given transformation usefulness with table, numerical value together with each total current that is provided in the middle of these pulses, and this controller can be kept a register to each pixel, configuration deposits the algebraic sum that is applied to the pulse on this pixel from some the previous time (for example, maintaining black state from this pixel) in.When specific pixel will be when white or gray states be driven into black state, this controller can be checked the register that interrelates with this pixel, determine from before the desired electric current of overall sequence DC balance of transformation of the upcoming black state of black state shift, and select a plurality of storages from vain/ash is to one of pulse of black transformation usefulness, it is not exactly relevant register to be reduced to zero, be at least remainder reduce to as far as possible little (in this case, the value that should relevant register will keep this remainder, and it is added to institute applies on the electric current in transition process subsequently).Obviously, repeat to apply the long-term accurately DC balance that this processing can reach each pixel.

Must investigate the explication waveform of DC balance in the waveform.In order to determine whether DC balance of a waveform, generally use the resistive model of an electro-optical medium.A model so is not an entirely accurate, but can be that supposition is enough accurately to current purpose.Utilize a such model, the characteristic of definition DC balanced waveform is the voltage that applied to the integration of time (pulse that is applied) is bounded.Note that it is " bounded " and for " zero " that this definition will be quadratured.This point is described for example, investigates the addressing waveforms of a monochrome, it use a 300ms *-the 15V rect.p. drives from vain to black transformation, and drives from deceiving to white transformation with 300ms * 15V rect.p..This waveform obviously is the DC balance, but the integration of each voltage that is constantly applied is non-vanishing; This integration 0 and ± change between the 4.5V-sec.But with regard to this integration bounded, this waveform is the DC balance; For example, this integration never reaches 9 or 18V-sec.

In order to further consider the DC balanced waveform, some definition done in term is wise.Term " pulse " was defined as in specific interval time, and the voltage that is applied in a general addressing pulse or the pulse elementary process is to the integration of determining (M-sec of unit) of time.Term " pulse electromotive force " will be used to refer to from any starting point (starting points of general a series of transformations of considering) be applied to all pulses on this display and.In this starting point, the pulse electromotive force at random is set to zero, and this pulse electromotive force rises and descends when applying pulse.

Utilize these terms, the definition of DC balance is, when and and if only if this pulse electromotive force when being bounded, this waveform is only the DC balance.The pulse electromotive force that bounded has been arranged just means that people must be able to say that Pulse Electric will definitely be in each in the possible situation of finite population.

For the time independently controller (that is, the waveform of its pulse is influenced by the initial and last state of the transformation considered only, and do not stopped other the controller of factor affecting of number of times, temperature, such as above-mentioned R1/R2 controller), in order to show that a waveform is the DC balance, must be able to prove that Pulse Electric will definitely be a bounded after each of the optical states sequence of any endless changes.An adequate condition of such proof is the function that this pulse electromotive force can be expressed as the original state of fixed number, and provide the work notion of a DC balance for the electro-optic displays controller, that is this pulse electromotive force can be expressed as the function of the previous and current optical states of finite population.The pulse electromotive force that note that any pixel of this display is constant from the end that an image upgrades to the starting point that another image upgrades, because do not apply voltage during this period.

For each combination of (limited) number original state, this controller applies fixing pulse (pulse of being determined by the data in the above-mentioned flash memory), and these fixing pulses can be enumerated.In order to enumerate them, must be by the number (that is for the R1/R2 controller, being used for this number of enumerating original state need define at the combination of two whole original states in rear end) of the original state that in this controller, uses at least.

Pulse electromotive force when finishing in order to define this renewal has been known the fixing pulse that applies in this pulse process, the whole states in must enumerating at this are determined the pulse electromotive force at the starting point place of this renewal.This means that clean pulse that waveform applied must be the function of an original state that lacks than the required number of pulse electromotive force that defines end uniquely.For being changed into, it determines to this means the optimum waveform problem identificatioin that will apply by a controller function of the original state that the number of the Pulse Electric of the waveform state that certainly will must to be its number use than definite this waveform lacks.For example, if a controller has by three state R1, the definite pulse data of R2 and R3 (wherein R3 is the gray shade scale that was right after before the initial gray shade scale of the transformation of being considered), then each of R1 and R2 is in conjunction with all allowing this electro-optical medium remain in same and the irrelevant pulse electromotive force of R3.

In other words, this controller must " know " that this electro-optical medium works as the pulse electromotive force of the transformation of being considered when beginning, so it can apply the suitable value that correct pulse produces pulse electromotive force after this transformation.If this pulse electromotive force is allowed to according to whole R1 in above-mentioned example, R2 and R3 and change then in the next one changes, will have no idea to allow this controller " know " the pulse electromotive force that this begins, because the R3 information of using in the past may be thrown aside.

As what shown, limited transformation method of the present invention preferably utilize a R1/R2 controller (that is, wherein the pulse that in any transition process, applies only depend on this transformation initial with last gray shade scale) carry out, and by above discussion as can be known, this Pulse Electric certainly will must be defined as the function that has only R1 uniquely in a such controller.

More complicated situation is to produce from such one phenomenon that can be called " pulse hysteresis " when determining optimum waveform.Except that the rare situation of under the optics fence, extremely overdriving, always become more black by the electro-optical medium of the driven of a polarity, and always become whiter by the electro-optical medium of the driven of opposite polarity.But, for some electro-optical medium, specifically seal electro-optical medium for some, optical states is along with the variation of pulse demonstrates hysteresis; When this medium is driven further to leucismus, the optical change of the unit pulse that each applied reduces, but, make this display be driven to reverse direction and change that then the optical change of every unit pulse increases suddenly if the polarity of the voltage that is applied is overturn suddenly.In other words, the optical change of every unit pulse not only depends on current optical states consumingly, and depends on the change direction of optical states.

This pulse lags behind and produces intrinsic " restoring force ", trend towards making this electro-optical medium to the middle gray change of rank, defeat with unipolar pulse (the same) and drive of the effort of this medium, and still keep the DC balance simultaneously from a state to another state with general gray scale image flow process.When applying pulse, this medium swims in three-dimensional R1/R2/ pulse hysteresis surface, till it reaches a balance.For each pulse length, this balance is fixed, and is generally located at the center in this optical range.For example, by experience have been found that drive one seal four gray shade scale electro-optical mediums from black to 100ms of dark gray requirements *-the 15V unipolar pulse, drive it and get back to deceive from dark gray and require a 300ms * 15V unipolar pulse.Owing to tangible reason, this waveform is not the DC balance.

A scheme that solves pulse hysteresis problem is to use bipolarity to drive, in other words, in (potential) non-direct-path from a gray shade scale, drive this electro-optical medium to next gray shade scale, in case of necessity, at first apply a pulse and drive this pixel optics fence and enter the optics fence,, apply the optical states that second pulse reaches this requirement then so that keep the DC balance.For example, in these cases, people can by apply 100ms *-the 15V pulse is from the black dark gray that becomes, but by at first applying additional negative voltage, apply positive voltage then, the R1/R2 pulse curve is swum in downwards on the black state, become again white from dark gray.Just as already discussed, stablize gray scale by fence, error accumulation problem is also avoided in such indirect transformation.

The pulse hysteresis phenomenon of electro-optical medium and original state dependence, as discussed above, in above-mentioned patent and application form, require the waveform of each transformation to change along with the pixel original state resume of being considered.As described at above-mentioned WO 03/044765, the optimum waveform of each transformation, can determine (that is the indicator corresponding with above-mentioned data array can be " tuning ") by utilizing initial " conjecture " transition matrix to set up waveform (it is used for being generally pseudorandom or original state is finished this electro-optical medium of optical states series access by fixing).A program deducts the optical states of the reality that reaches the same combination from the target gray states of each original state, so that calculate an error matrix, its size is identical with this transition matrix.Each element in this error matrix is all corresponding to an element in the transition matrix.If an element in this transition matrix is too high, then also push away higherly elements corresponding in this error matrix.Can use PID (proportional-integral-differential) control to come error matrix is driven to zero then.There is cross term (each element in this transition matrix all influences the more than one element in this error matrix), but these effects are smaller, often undertaken by repeatedly iterating, along with the amplitude of the value in this error matrix reduces and reduces along with tuning.(note that the I or the D constant of PID controller can be set to 0 sometimes, the result is PI, PD or P control.)

When this is tuning when finishing dealing with, the previous optical states of finding some number should be in this transition matrix, so that reach the accurate performance of some gray shade scale.For example, utilize this processing specific seal electro-optical medium, the result obtains a waveform, the more previous optical states of this controller ratio of record in this transition matrix wherein, and the pulse that utilizes algorithm to calculate in first section of this waveform guarantees the DC balance.In this waveform, the combination that this pulse electromotive force is allowed to each original state that is covered by this transition matrix is different.

Obtain relevant (" TM size ") and the greatest optical error of this waveform between the number of this transition matrix size, list as following table 1:

Table 1

The TM dimension	Greatest optical error (L*)
		??1	??10.6
??2	??3.8
		??3	??2.1
??4	??1.7

Because the limit of general viewers visual experience is about 1L* unit, the data in this table show that it is very useful having more than one dimension in this transition matrix, and two-dimensional matrix is better than one dimension, and three-dimensional matrice is better than two dimension etc.

Notice above-mentioned all each points, be two gray-scale Control device designs of above-mentioned R1/R2 preferred wave shape form.This waveform is kept fixing pulse electromotive force for each last optical states R1, but is to use two-dimentional transition matrix.Stablized fence, so that reduce the accumulation of error, and design comes to have low divergence in the process of upset, because its considers pulse hysteresis curve.

Below in the symbol of usefulness, the digitized representation pulse.By apply one given period-V (that is ,-15V) apply negative pulse, by apply one given period+V applies positive pulse (that is waveform is width modulation), makes the amplitude of volt-time product equal the amplitude of this pulse.Voltage modulated can be used as another program and uses.

In this preferred waveform, applying following pulse train in the renewal process each time, from left to right timely reading:

-TM(R1，R2)IP(R1)-IP(R2)TM(R1，R2)

Wherein " IP (Rx) " representative has the correlation values (being vector in this case) of the pulse electromotive force matrix of a numerical value from each gray shade scale, and TM (R1, R2) combination has the correlation values of the transition matrix of a numerical value from each R1/R2 in representative.Certainly, for the value of some R1 and R2, (R1 R2) can bear TM.(just as already noted, for simplicity, the pulse train of the type can be abbreviated as " x/ Δ IP/x " sequence hereinafter.)

Value in this transition matrix can be regulated as required, and needn't worry the DC balance, because first and the 3rd section clean pulse of this waveform always is 0.Pulse potential difference values between the initial and last state is applied to the interlude of this waveform.

Have been found that by experience this last driving pulse almost always has bigger effect than initial pulse to last gray shade scale, so this transition matrix that this waveform is used can be tuning with above-mentioned same PID method.For fixing last gray shade scale, influence the renewal speed of this waveform for the value of this pulse electromotive force setting.For example, all pulse electromotive forces can be set to zero, but it causes a long update time, because this last driving pulse (the 3rd section) is always opposite with the initial pulse (first section) of equal in length.Thereby in this case, this last driving pulse can not be longer than half of total update time.By careful strobe pulse electromotive force, might be used for this last pulse to much bigger total update time of percent; For example, can reach and account for last driving pulse over half and up to 80% of maximum total update time.

The length of different pulses is preferably selected by computing machine, utilizes gradient to follow optimization method, similarly PID control, limited difference in conjunction with evaluation etc.

Pointed as WO 03/044765, the transformation in the electro-optical medium generally is temperature sensitive, has been found that when all to the transformation of specific gray shade scale during all always from same optics fence, gray shade scale increases the uncompensated stability of temperature.Its reason is very simple, changes along with temperature, and the switch speed of electro-optical medium becomes comparatively fast or be slower.If in 2 gray-scale monitors, dark gray is ejected from black fence to the transformation of bright gray scale, but is ejected from white fence to the transformation of bright gray scale in vain.If the switch speed of this medium becomes slower, then the bright grey states from black addressing will become darker, but will become brighter from the bright grey states of black addressing.Thereby for the waveform of temperature stabilization, a given gray shade scale is always from same one " side " convergence, that is the last pulse of this waveform always has same polarity, and this is important.(R1, R2) (R1, R2) in the preferred drive scheme of sequence, this requires to select TM, and (R1, R2) value makes the symbol of each numerical value only depend on R1, at least for some gray shade scale to IP (R1)-IP (R2) TM at above-mentioned utilization-TM.A method for optimizing is, allowing TM value is any one symbol in the black and white state, but only just uses for bright gray scale, and for dark gray only with negative, thereby, from more approaching optics fence convergence middle gray.

This preferred waveform and technology are compatible fully, such as this waveform of insertion of short pause period so that increase pulse resolution, as what describe below.

As what shown, above-mentioned-x/ Δ IP/x pulse train can be revised, so that comprise additional pulse.Such modification allows to comprise the pulse of an additional classes, is called " y " pulse hereinafter.The feature of " y " pulse is, it is the form of [+y] [y], and wherein y is a pulse value, can be negative or positive (in other words, this form [y] [+y] is effectively same).This y pulse is completely different with " x " pulse of describing in the past, be that half [x] and [+x] that this " x " pulse is right is provided with before this Δ IP pulse and afterwards, yet " y " pulse can be arranged on other position of this pulse train.

Second such modification be add on the arbitrfary point in this pulse train a 0V " pulse " (that is, one-period when related pixel is not applied voltage), improve the performance of this sequence, for example move up or down slightly, or reduce or change the influence of previous state information this pixel final state by this gray shade scale that this transformation is caused.Such 0V section is not can insert between the different pulse elements, inserts exactly in the middle of the single pulse element.

A structure fence is stablized the preferable methods that waveform is used, and utilizes at WO 03/044765 described indicator, and this method is as follows:

(a) numerical value (generally calculating by experience) of the pulse electromotive force that each gray shade scale uses is set, and for each changes the suitable Δ IP pulse of insertion indicator;

(b) for each transformation, pick the numerical value that an x uses, and before Δ IP, insert one-x pulse, and after Δ IP pulse, insert one+x pulse (just as already noted, the value of x can be born, so-x and+the x pulse can have polarity arbitrarily);

(c) for each transformation, pick a y value, and insert one-y and+the y pulse is to this pulse train.Should-the y/+y pulse combined can insert this pulse train in any edge of pulse circle, for example before-x pulse, before the Δ IP pulse ,+the x pulse before or+the x pulse after;

(d) change any point in this sequence or what time insert n frame 0V, wherein n=0 or bigger for each; With

(e) repeat above-mentioned steps as required repeatedly, till this waveform performance meets the requirements of level.

Now illustrate this processing with reference to the accompanying drawings.Fig. 2 represents the basic-x/ Δ IP/+x structure of the waveform of a transformation usefulness, and for the purpose of illustrating, the value of supposing two of x and Δ IP all is positive.Unless require Δ IP and+be provided between the x pulse 0V interval time, be applied to the voltage that this is tied otherwise needn't be reduced between these two pulses, make this Δ IP and+in fact the x pulse form a long positive pulse.

Fig. 3 illustrates [y] [+y] pulse to inserting basic-x/ Δ IP/+x waveform shown in Figure 2 with symbol.Should-y and+the y pulse not necessarily will occur in succession, but can insert original waveform in different positions.Two particularly advantageous special circumstances are arranged.

First kind of special circumstances, should " y ,+y " pulse to be placed on-starting point of x/ Δ IP/+x waveform ,-the x pulse before so that produce waveform shown in Figure 4.Have been found that when y and x opposite in sign as illustrational at Fig. 4, this last optical states can be by coming tuning subtly to duration y even the coarse adjusting of appropriateness.Thereby the value of x can be regulated and the value of y can be regulated at the last control of the last optical states of this electro-optical medium at coarse control.Believe that this will take place, because y pulse increase-x pulse, thereby, change the degree that this electro-optical medium is pushed into its one of optics fence.The degree that pushes one of optics fence is known, so that the meticulous adjusting (providing by the x pulse in this case) away from this last optical states after the pulse of this optics fence is provided.

Second kind in particular cases, illustrate at Fig. 5, should-the y pulse is placed on this again-starting point of x/ Δ IP/+x waveform, before-x the pulse, but should+the y pulse is placed on the end of this waveform, should+the x pulse after.In the waveform of the type, this last pulse provides coarse tuning, because this last optical states is very responsive to the amplitude of y.It is thinner tuning that this x pulse provides, and drives the amplitude that enters this optics fence because last optical states generally depends on less intensely.

As what shown, a pair of above " y " pulse can be inserted this basic-x/ Δ IP/+x waveform, so that allow the gray shade scale of this electro-optical medium is carried out " fine tuning ", and so manyly can differ from one another to " y " pulse.Fig. 6 in a kind of like this mode that is similar to Fig. 3, inserts second pair of y type pulse (indicating " z ", "+z ") waveform of Fig. 5 with the explanation of symbol example.Be readily understood that because should-z and+the z pulse can introduce on any pulse border of waveform shown in Figure 5, from introduce this-z can cause a large amount of different waveforms with+z pulse.A preferred gained waveform as shown in Figure 7; The waveform of the type is useful to the fine tuning of last optical states, and its reason is as follows.Investigation do not have-z and+situation of z pulse (that is, Fig. 5 waveform discussed above).This x pulse element is used for fine tuning, and this last optical states can reduce by increasing x, and increases by dwindling x.But, be undesirable beyond x reduced to certain point, because this electro-optical medium does not bring and stablizes this waveform and requiredly enough approach an optics fence then.For fear of this problem,, add-z that+z pulse is right by as shown in Figure 7, make z have the symbol opposite with x, not to dwindle x, can (in fact) increase-x pulse and do not change+the x pulse.Should+z pulse increase-x pulse, and while-z pulse keeps this transformation under the clean pulse of this requirement, thereby, keep a DC balance change table generally.

In limited transition waveforms scheme of the present invention, (this indicator key element and zero changes corresponding for " diagonal line key element ", wherein this initial and last gray shade scale are same, and address is because such key element is on the leading diagonal line in one of an indicator common matrix formulation like this; Such diagonal line key element has Δ IP=0) so that comprise x and two pulses of y.Any given indicator element can comprise zero group or organize x and/or the y pulse more.

Limited transformation method of the present invention can also be utilized the frame period.For rewriteeing fully in the needed frame group of this display (the being called superframe easily) process, repeat the scanning of pixel groups, and on a typical electrical optical display unit, more than this scanning will repeat once.Generally, fixing sweep speed is used for upgrading, 50Hz for example, and this is to 20 milliseconds frame, and this allows.But this frame length may provide the resolution to optimized waveform performance deficiency.In many cases, the frame of length t/2 is best, for example in the waveform of general 20 milliseconds of frame lengths.Might be n/2 so that produce a pulse resolution in conjunction with the frame of difference number of times time delay.In order to consider a specific situation, can be length the starting point that the single frame of 1.5*t inserts this waveform, and a similar frame inserts this waveform end, and a similar frame (was right after before the end of 0V frame in this waveform end, this should occur with common frame rate, and it generally is used for the end of this waveform, so that avoid by the caused undesirable influence of the residual voltage on the pixel).These two long frames can be realized by the 0.5*t between the scanning that adds two consecutive frames simply time delay.This waveform can have following structure then:

T ms frame: t/2ms time delay: t ms frame [...] t ms frame: t/2ms time delay: t ms frame (all outputing to 0V)

For a length is 20 milliseconds normal frames, and initial and last frame add that their respective delay amounts to and all be 30 milliseconds.

Utilize this waveform, structure, initial and last pulse allow to change 10 milliseconds of length by following algorithm:

(a) if the length of this inceptive impulse can be divided exactly by t, then first frame is driven by 0V and constitutes, and the frame of the t ms of a corresponding number is activated so that meet the requirements of pulse length; Or

(b) if the length of this inceptive impulse stays the remainder of t/2 during divided by t, then the first frame 1.5*t is activated, and the t millisecond frame of number is activated so that meet the requirements of pulse length accordingly continue this initial frame after.

Same algorithm is followed in last pulse.Note that this algorithm is suitably worked that this initial and last pulse must be distinguished the starting point alignment and terminal point aligns.In addition, in order to keep the DC balance, this initial and last pulse can be that one-x/+x is to corresponding part.

No matter whether adopt pause period, have been found that, the effect of waveform that realize to change usefulness is by in this waveform in any pulse process or before it, exist a no-voltage cycle (being actually a time delay) to revise, limited transformation method of the present invention can comprise the no-voltage cycle in the subsequent pulses or between them in this waveform, that is this waveform can be " discrete ", as this term in the above and use in above-mentioned PCT/US2004/010091.Fig. 8 to 10 illustrates the variation of the basic-x/ Δ IP/+x waveform in comprising of Fig. 2 in such no-voltage cycle.In the waveform of Fig. 8, this-insert a time delay between x pulse and this Δ IP pulse.In the waveform of Fig. 9, go into a time delay at this Δ IP pulse interpolation, perhaps, still the same, this Δ IP pulse is split as two independent pulses of this time delay of being separated by.The waveform of Figure 10 is similar to the waveform of Fig. 9, just this time delay insert should+the x pulse in.Time delay can be contained in a waveform, and reaching does not have such delay optical states that just is beyond one's reach.Time delay can also be used to the last optical states of fine tuning.This fine tuning ability is important, because in a driven with active matrix, the temporal resolution of each pulse is by the sweep speed definition of this display.The temporal resolution that is provided by this sweep speed may be very coarse, so that there is not the additional means of some fine tuning just can not reach accurate last optical states.

Interrupt scanning method of the present invention

Just as already noted, the present invention provides a kind of " interrupt scanning " method for driving the electro-optic displays with a plurality of pixels that are divided into a plurality of groups.This method comprises each that select in a plurality of pixel groups in succession, and is not to apply driving voltage to each pixel in this selected group, applies non-driving voltage exactly, finishes the scanning of all pixel groups in first frame period.In second frame period (should be understood that any specific pixel can apply driving voltage in first frame period, and apply non-driving voltage in the second frame period process, vice versa) process, apply the scanning that repeats this pixel groups in the driving voltage process.In interrupt scanning method of the present invention, between first and second frame periods, interrupt the scanning of this pixel groups in the pause period, this pause period is no longer than first or second frame period.In the method, this general equal in length of first and second frame periods, and the length of this pause period generally is the part (best 1/2,1/4 etc.) of the length in one of each frame period.

Between difference was to adjacent frame periods, this interrupt scanning method can comprise a plurality of pause period.The best length of a plurality of pause period like this equates basically, and the total length of a plurality of pause period preferably is not to equal a complete frame period, equals a frame period exactly to deduct a pause period.For example, as following will more detailed argumentation, an embodiment of first method can use a plurality of 20ms frame periods, and not to be three be exactly four 5ms pause period.

In this interrupt scanning method, pixel groups generally is each row of a traditional row/show source matrix pixel array certainly.This interrupt scanning method comprise each that select in a plurality of pixel groups in succession (that is, generally, scan each row of this matrix), and in this selected group, be not to apply driving voltage, apply non-driving voltage exactly, the scanning of all each pixel groups is all finished in first frame period.Repeat the scanning of this pixel groups, and on a typical electro-optic displays, in rewriteeing the desired superframe process of this display, repeat this more than run-down.Interrupt in the pause period process of the scanning of this pixel groups between first and second frame periods, this pause period is no longer than first or second frame period.

Although driving voltage only is applied to any specific pixel electrode with delegation's addressing time in the process of scanning each time, this driving voltage continues on this pixel electrode in selecting with the time course between the delegation in succession, just decay lentamente, other is gone just when chosen when this matrix, make this pixel in this time course, continue to be driven, and the interrupt scanning method rely on this pixel this continue to be driven.In its " non-selected " time course, ignore this moment, in its non-seclected time in the process, the slow decay of this voltage on this pixel electrode, be right after in the frame period of this pause period front process, the pixel that is set to this driving voltage will continue this driving voltage of experience in this pause period process, make that in fact the frame period of front prolongs the length of one section pause period for a such pixel.On the other hand, be set to the pixel of this non-driving (be generally zero) voltage, in the frame period process that is right after in this pause period front of x front, will in this pause period process, continue to experience no-voltage.May wish to regulate the length of this pause period,, have the numerical value of requirement to guarantee the overall pulse of in this pause period process, carrying so that allow the slow decay of the voltage on this pixel electrode.

Presented for purposes of illustration in order to lift simple example of this interrupt scanning method, investigate the simple width modulation drive scheme of superframe that has by a plurality of (for example, 10) 20ms frame formation.Generally, the last frame of this superframe will be provided with whole pixels to this non-driving voltage, because maybe just be driven relatively long interval time when bistable electro-optic displays just thinks generally that shown image changes when thinking to be in when preferably refreshing shown image, make each superframe with long cycle of general heel, wherein this display is not driven, and change rapidly for fear of in this long non-drive cycle process, on some pixel, taking place, to be set to non-driving voltage be extraordinary to whole pixels when this superframe finishes.In order to change a such drive scheme according to interrupt scanning method of the present invention, can between two 20ms frames in succession, insert a 10ms pause period, and this simple modification makes the pulse that is applied and finishes that possible maximum difference reduces by half between the pulse that a given transformation needs ideally, roughly reduces by half in the maximum deviation of the gray shade scale that is reached in practice with this.This 10ms pause period is inserted in each superframe after the frame second from the bottom easily, but inserts on other the point that in case of necessity can be in this superframe.

In the practice, in this example, preferably not only insert the 10ms pause period, but also an additional 20ms frame is inserted each superframe.Unmodified drive scheme makes people apply such pulse to any one given pixel:

0,20,40,60...160,180 units

One of them unit pulse be defined as apply that driving voltage 1ms causes pulse.Thereby the maximum difference between the desirable pulse of available pulse and a given transformation usefulness is 10 units.(, have only 1/9 frame of this superframe to can be used to apply this driving voltage because the last frame of this superframe all is set to non-driving voltage to whole pixels.Just as already explained, the any pixel that is set to this driving voltage on the frame of this pause period front all continues to experience one of this driving voltage and equals the cycle that this frame period adds pause period, thereby, for this frame, be the pulse of one 30 unit of experience, rather than 20 units.Correspondingly, amended drive scheme allows to apply such pulse to any given pixel:

0,20,30,40,50,60 units etc.

Preferably this additional frame is inserted superframe, so that allow this amended drive scheme can transmit a just pulse of 180 units.Because any just is the pulse of the several times of 20 units, require all that this related pixel is set to non-driving voltage in the frame process of this pause period front, reach one just the pulse of 180 units require the superframe of one 11 frame, make any pixel that will receive this 180 pulse in 9 frame processes, to be set to this driving voltage, in the frame of this pause period front, be set to this non-driving voltage, and (as always) is set to non-driving voltage in the last frame of this superframe.Thereby when utilizing this amended drive scheme, the maximum difference between the ideal pulse of available pulse and a given transformation usefulness is reduced to 5 units.Although (this amended drive scheme can not apply the pulse of one 10 unit, and its consequence is very little in practice.In order to produce quite consistent gray shade scale, the number of available pulse must be significantly greater than the gray shade scale number of this display, makes that any transition in grayscale is all unlikely to require a little pulse to 10 units.)

Certainly this pause period can have desired any number of control and the length that reaches the requirement of the pulse that applied.For example, not to change this above-mentioned drive scheme to comprise a 10ms pause period, but this drive scheme can be revised to such an extent that comprise three 5ms pause period after different 20ms drives frame, preferably returns the driving frame that this drive scheme adds other three 20ms, not the heel pause period.This amended drive scheme allows to apply some such pulses to any given pixel:

0,20,25,30,35....170,175,180 units

Reduce to 2.5 units with the maximum difference between the ideal pulse of this available pulse and a given transformation usefulness, compare with original unmodified drive scheme and dwindled four times.

The polarity problems of the pulse that is applied has been ignored in the discussion of this interrupt scanning method front.As top and discuss at above-mentioned WO 03/044765, the bistable electro-optical medium requires the pulse of two kinds of polarity all to apply.In some drive scheme, such as the drive scheme of showing slides, before new image writes display, whole pixels of this display all at first are driven into an extreme optical state, be not black be exactly white, and after this this pixel drive is arrived their last gray states by the pulse of single polarity.Such drive scheme can be revised according to this interrupt scanning method with the mode of having described.Other drive scheme requires the pulse of two kinds of polarity all to apply the last gray states of this pixel drive to them.The pulse of two polarity can be to be applied in the independent frame, perhaps the pulse of two polarity can be to be applied on the same frame, for example utilizes three grade drive schemes, and wherein public preceding termination electrode remains on the V/2 voltage, and each pixel electrode remains on 0 simultaneously, on V/2 or the V.When the pulse of two polarity is applied on the single frame, then expect by providing at least 2 single pause period to influence the interrupt scanning method, a pause period is followed the frame that wherein is applied in a polar impulse, and another pause period is followed the frame that wherein is applied in the opposite polarity pulse.But, when utilizing that one wherein the pulse of two kinds of polarity all is applied to drive scheme on the same frame, this interrupt scanning method can only be utilized a single pause period, because as what will become apparent from the above, the effect that comprises a pause period after a frame is, increase the amplitude be applied to the pulse on any pixel that in this frame, has applied driving voltage, and irrelevant with the polarity of this driving voltage.

Also as above-mentioned WO 03/044765 and discussed above, the most handy such drive scheme of many bistable electro-optical media drives, it reaches long-term DC current (DC) balance, and such DC balance utilizes such drive scheme to realize easily, the immovable basically DC balancing segment of the gray shade scale of one of them its pixel is applied in and will changes the main of gray shade scale and drive before the section, selects to such an extent that to make the pulse algebraic sum that is applied be 0 or at least very little for these two sections.If this main section that drives is revised according to this interrupt scanning method, then strong this DC balancing segment of proposed amendments is to avoid causing the serious unbalance caused additional pulse of pause period of DC by inserting accumulation.But this DC balancing segment needn't be revised in the mode that drives the accurate mirror image that shed repair changes as this master, because this DC balancing segment can have gap (no-voltage frame), and most of electro-optical medium is not subjected to the unbalance injury of short time DC.Thereby that discusses in the above utilizes in the drive scheme that inserts the single 10ms pause period in the middle of 10 20ms frames, and the duration of first frame by making this drive scheme is 30ms, can reach the DC balance.In this frame process, apply or do not apply driving voltage, can make overall pulse equal the several times of 20 units, make this pulse balance easily subsequently to a pixel.At the drive scheme that utilizes three 5ms pause period, first two frames of this drive scheme can be 25 and 30ms (with any order) similarly on the duration, make overall pulse equal the several times of 20 units again.

From the above, will find out, interrupt scanning method of the present invention require prolong the addressing time and improve paired pulses and the control of the gray scale that therefore this method produced between weigh the advantages and disadvantages, prolonging the addressing time is owing to the pause period for each insertion in each superframe comprises that the needs of an additional frame cause.But,, can provide the improvement of the control highly significant of paired pulses as long as this interrupt scanning method makes the addressing time lengthening not many; For example, an above-mentioned superframe comprises that 10 20ms frames revise the drive scheme that comprises three 5ms pause period, can be cost with 40% addressing time lengthening, produces four times improvement on the pulse accuracy.

The gray scale method of balance of the present invention

Just as already noted, the present invention also provides a kind of balance gray scale method, in order to drive the electro-optic displays of a plurality of pixels of configuration in an array.This pixel drives with the pulse-width modulation waveform that can apply a plurality of different pulses.Drive circuit stores indicates whether to apply the data of a given pulse, is higher or lower than the gray shade scale that requires gray shade scale with producing one.When two of two neighbors all required to be in same gray scale, the pulse regulation that is applied on these two pixels must make a pixel be lower than the gray scale of requirement, and the while one other pixel is higher than the gray scale of requirement.

In form preferred one of this method, pixel is divided into two groups, indicates hereinafter " even number " and " odd number ".These two pixel groups can be configured to checkerboard pattern (making the pixel of each row and column replace) between these two groups, perhaps do other configuration, as described at above-mentioned WO 03/044765, suppose that each pixel has the neighbours of at least one opposite group, and two groups use different drive schemes.If the data of storage point out that it is the transformation of requirement gray shade scale basically that one of available pulse will produce, the then pulse that applies at this transformation, both the dual numbers pixel applied this pulse to odd pixel again.But, if the data of storage point out that a specific gray shade scale changes desired pulse and is between these two available pulses half basically, then one of these pulses are used for this transformation in even pixel, and other of these pulses are used for the transformation of odd pixel.Thereby, if two adjacent pixels want to be in same gray states (under the most important state of accurate control to gray scale), one of these pixels will have the gray shade scale that is slightly higher than calling hierarchy, and another will have the gray shade scale that is lower than this calling hierarchy slightly simultaneously.Vision with the optics averaged result will be see these two gray shade scales average, thereby, produces one and compares the approximate gray scale that the grade that reaches with available pulse more approaches calling hierarchy.In fact, this balance gray shade scale method uses small-signal spatial jitter (applying the error of proofreading and correct the pulse that is applied) to overlap on the true gray scale of large-signal, increases the factor of two available impulse ratings.Because still on ballpark gray shade scale, the effective resolution of actual display is not compromise for each pixel.

The necessary calculating of a complete realization provides as follows with the MATHLAB false code.This floor function is rounded up to nearest integer downwards, and its first independent variable of mod function calculation is divided by the remainder of its second independent variable:

quotient＝floor(desired_impuslse)

remainder＝mod(desired_impulse，1)

if?remainder＜＝0.25

even_parity_impulse＝quotient

odd_parity_impulse＝quotient

else?if?remainder＜＝0.75

even_parity_impulse＝quotient+1

odd_parity_impulse＝quotient

else

even_parity_impulse＝quotient+1

odd_parity_impulse＝quotient+1

end.

In some drive scheme of former description, for example top circulation RSGS drive scheme with reference to Figure 1A and 1B description, the pixel of this display has been divided into two groups, and different drive schemes is applied to these two groups so that meet the requirements of the amplitude of the needed pulse of gray shade scale will be two groups different.Can revise such " two groups " drive scheme according to balance gray shade scale method, but the realization details of this method slightly is different from simple situation discussed above.Compared the transformation of available pulse and requirement is needed simply, but calculated the error of two groups of gray scales individually, this error is got arithmetic mean, and determine to move a group and whether will reduce this arithmetic mean to different available pulses.Note that in this case, reduce arithmetic mean and can depend on differently which group is moved to a different pulse, and obviously which moves to produce less which on average just to carry out.

Again, this method it is contemplated that and be the small-signal spatial jitter that realizes at the top of large-signal interior intensity, shakes the pulse error that the limitation of proofreading and correct used width modulation causes with this small-signal.Because in this scheme, each pixel and is proofreaied and correct and is just proofreaied and correct approximation error still roughly on correct gray scale, and the true resolution of display is not compromised.Say it in another way, this method realizes the small-signal spatial jitter at the top of the real gray scale of large-signal.

Diverse ways of the present invention can utilize at above-mentioned application form, the different additional variation and the technology of especially above-mentioned WO03/044765 and PCTUS2004/010091 description.Will appreciate that, on in order to the total waveform that drives an electro-optic displays, at least in some cases, some transformation can be carried out according to diverse ways of the present invention, and other transformation simultaneously can not utilize this method of the present invention, but can utilize the transformation of other type that describes below.For example, diverse ways of the present invention can utilize any one or more:

Discontinuous addressing (seeing above-mentioned PCT/US2004/010091, paragraph [0142] to [0234] and Fig. 1-12);

The addressing of DC balance is as (also the seeing above-mentioned PCT/US2004/010091, paragraph [0235] to [0260] and Figure 13-21) of upper part ground discussion;

Defined area update (see above-mentioned PCT/US2004/010091, paragraph [0261] is to [0280]);

(see above-mentioned PCT/US2004/010091, paragraph [0284] to [0308] and Figure 22) in the bucking voltage addressing;

The DTD integration dwindles addressing, and (see above-mentioned PCT/US2004/010091, paragraph [0309] to [0326] and Figure 23); With

Residual voltage addressing (seeing 03/044,765,59 to 62 pages of above-mentioned WO).

Claims (23)

1. method that is used to drive electro-optic displays with at least one pixel, described at least one pixel can reach any one gray shade scale at least four different gray shade scales that comprise two extreme optical state, and described method comprises:

On described display, show first image; With

Rewrite described display, so that show second image thereon,

Described method is characterised in that: in the rewriting period of described display, any pixel drive of not touching extreme optical state having stood to surpass the number of transitions of predetermined value is before its last optical states in described second image, to at least one extreme optical state, described predetermined value is one at least with described pixel drive.

2. according to the method for claim 1, wherein, realize the rewriting of described display, make in case the pulse by a kind of polarity is driven into opposite extreme optical state with pixel from an extreme optical state, then described pixel does not receive the pulse of opposite polarity, till it has reached described opposite extreme optical state.

3. according to the process of claim 1 wherein, described predetermined value is not more than N/2, and wherein N is the sum that pixel can the gray-scale displayed grade.

4. according to the process of claim 1 wherein, the rewriting of described display by apply to described pixel or each pixel voltage-V, 0 and+any one or a plurality of realization among the V.

5. according to the process of claim 1 wherein, realize the rewriting of described display, make for any transformation series that pixel stood, the voltage that applies all be bounded to the integration of time.

6. according to the process of claim 1 wherein, realize the rewriting of described display, make the pulse that between tour, applies only depend on the initial gray shade scale and the last gray shade scale of this transformation to pixel.

7. according to the process of claim 1 wherein, change at least one from gray shade scale R2 to gray shade scale R1 that described at least one pixel stood, what give that described pixel applies is the pulse train of following form:

-TM(R1，R2)IP(R1)-IP(R2)TM(R1，R2)

Wherein " IP (Rx) " representative is from the correlation values of the pulse electromotive force matrix that each gray shade scale is had a numerical value, and TM (R1, R2) representative is from each R1/R2 combination is had the correlation values of the transition matrix of a numerical value.

8. according to the method for claim 7, wherein, for wherein said initial gray shade scale and the last different whole transformations of gray shade scale, described pulse train has following form:

-TM(R1，R2)IP(R1)-IP(R2)TM(R1，R2)。

9. according to the method for claim 7, wherein, (R1, R2) (R1, R2) in the sequence, (R1, R2) section takies the over half of maximum update time to last TM to IP (R1)-IP (R2) TM at described-TM.

10. according to the process of claim 1 wherein, realize the rewriting of described display, feasible transformation to given gray shade scale always realizes by the final pulse of identical polar.

11. according to the method for claim 10, wherein, the gray shade scale beyond described two extreme optical state is from the direction convergence of nearer extreme optical state.

12. according to the method for claim 7, wherein, (R1, numerical value R2) make the symbol of each numerical value only depend on R1 to select described TM.

13. method according to claim 12, wherein, described TM (R1, R2) numerical value be chosen to one or more bright gray shade scales for just to one or more dark gray levels for negative, make gray shade scale beyond described two extreme optical state from the direction convergence of nearer extreme optical state.

14. according to the method for claim 7, wherein, the extra-pulse that described at least one transformation also comprises [+y] [y] form is right, wherein y is the pulse value that can just maybe can bear, described [+y] and [y] pulse are inserted into described-TM (R1, R2) IP (R1)-IP (R2) TM (R1, R2) sequence.

15. method according to claim 14, wherein, second extra-pulse that described at least one transformation also comprises [+z] [z] form is right, wherein z is different from the pulse value of y and can bears or can be just, described [+z] and [z] pulse are inserted into-TM (R1, R2) IP (R1)-IP (R2) TM (R1, R2) sequence.

16. according to the method for claim 7, wherein, described at least one transformation also comprises the period that does not apply voltage to described pixel.

17. according to the method for claim 16, wherein, (R1, R2) (R1 is R2) between two of sequence elements for IP (R1)-IP (R2) TM not appear at described-TM to the described period that described pixel applies voltage.

18. according to the method for claim 16, wherein, (R1, R2) (R1 is R2) between the intermediate point in the individual element of sequence for IP (R1)-IP (R2) TM not appear at described-TM to the described period that described pixel applies voltage.

19. according to the method for claim 16, wherein, described at least one transformation comprises at least two periods that do not apply voltage to described pixel.

20. according to the method for claim 7, wherein, described display comprises and is divided into a plurality of pixels of a plurality of groups, and described transformation realizes by following steps:

(a) each pixel groups in the described a plurality of pixel groups of Continuous Selection, and each pixel in described selected group applies driving voltage or non-driving voltage, and all the scanning of pixel groups was finished in first frame period;

(b) during second frame period, repeat the scanning of described pixel groups; With

(c) between the pause period between described first and second frame periods, interrupt the scanning of described pixel groups, described suspending period is no longer than described first or second frame period.

21. according to the process of claim 1 wherein, described electro-optic displays comprises electrochromism or rotates double-colored film electro-optical medium.

22. according to the process of claim 1 wherein, described electro-optic displays comprises the electrophoretic medium through encapsulation.

23. according to the process of claim 1 wherein, described electro-optic displays comprises microcell electrophoretic medium.

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