Patent Application
20090002355
The present invention relates to an active matrix liquid crystal display device and a method for driving the same.
An active matrix liquid crystal display device, in which each of liquid crystal display pixels arranged in matrix form has its own controlling thin film semiconductor element, is broadly used for various applications such as personal computers.
Many of such matrix liquid crystal display devices employ an alternating current driving method. According to this driving method, the polarity of driving voltage applied to the liquid crystal is reversed for every frame, which is a countermeasure for some kinds of deterioration of a reduced resistivity due to the liquid crystal material composite denatured during the considerably long operation with the d.c. voltage supply. The more specified fundamental operation in such driving method is disclosed in a Non-Patent Document 1 listed below.
In such an a.c. driving method, the polarity reversal frequency of the driving voltage, once reaching a half of the frame frequency, typically causes flickering, but by spatially and time-varyingly averaging the polarity reversal, the basic wave components of optically responded ripples can be made the frame frequency or even higher so as to avoid the flickering (the visible flickering). More Particularly, an adjacent pixel to any single pixel (or an adjacent column or row of pixels to any set of pixels in series) is reversed in the polarity of the driving voltage applied thereto, and further, the corresponding pixels or the corresponding set of the pixels are made to assume alternately inverted polarities between any pair of consecutive frames.
In the aforementioned prior art, a polarity inverting rate of the driving voltage is considerably high, and this may generally cause the driver circuit to consume increased power. An improved prior technology for overcoming such a problem, has been designed to save the power consumption while the a.c. driving is maintained, which is also in the list below as Patent Document 1 filed by the applicant of this application. This driving method is a driving method to a.c. drive pixels arranged in matrix form, in which a plurality of row electrodes which extend horizontally in the picture to be displayed are selectively activated in a horizontal scanning period, and a plurality of column electrodes which extend vertically in the picture are provided pixel voltage corresponding to the picture and the horizontal scanning period by reversing its polarity frame by frame, resulting in the pixel voltages developing alternating polarities spatially and in the vertical direction in the picture of the frame period. By this method, a timing of applying a group of pixel voltages to one row of electrodes and another timing of applying another group of pixel voltages to another row of electrodes which are expected to have the same polarity as the one row are generated in time sequence, and in response to the supply timings of the pixel voltages, the corresponding row electrode is made active.
In this way, the example in Patent Document 1 attains a reduction of the power consumption by reducing the polarity inverting rate of the pixel voltage along time axis with the dimensional polarity reversal pattern of the pixel voltage in the field being unchanged from the prior art a.c. driving pattern.
In such a prior art, however, if a user desires, for example, a screen full of even dark gray monochromatic representation, there sometimes arises an inadvertently awkward phenomenon called ‘line-to-line artifact’ where relatively bright and dark horizontal stripes are repetitively alternated to fill the whole field.
The disclosure in Patent Document 2 in the list gives a solution to the poor representation with stripes that are caused in a situation where a plurality of data lines (multiples of two in number) are to be gathered in one to connect to data line driver circuits having a smaller number of data lines. This improvement includes a shift means, upon each scanning, capable of permuting a set of n data lines that are on standby and are to be sequentially connected to output signal lines of the data line driver circuits.
In addition, well known in the prior art is an driving apparatus that uses multiplexers and supplies picture signals to picture signal lines (picture buses) on the timesharing basis so as to drive the liquid crystal display device.
In this way, this type of the prior art liquid crystal display device has the multiplexers arranged adjacent to each other, and for the purpose of simplification of a timing circuit in liquid crystal display driver circuit, the order of selecting some among the picture signal lines keeps consistently fixed so as to avoid duplexity of any picture signal line. Additionally, a picture signal amplifier in the liquid crystal display driver circuit includes a reference voltage circuit that produces a predetermined voltage or a predetermined voltage depending upon polarity.
The configuration as mentioned above has an advantage to reduce the number of output terminals from the driver IC and the area of the same, and thus, the resultant driver IC can attain an advantage of cost reduction.
In order to overcome the aforementioned disadvantages in the prior art, the applicant of the present invention has provided a solution that in applying a signal from a single signal source to more than one picture signal lines, the picture signal lines are divided into two groups, and the groups are selected in a varied sequence from first cycle to the second cycle.
While sequentially selecting the adjacent picture signal lines one from another, however, a variation in voltage level in the adjacent picture signal line(s) affects the voltage level in the reference picture signal line, and even a minor variation, when accumulated, may result in an adverse artifact that, for instance, red stripes are observed although a gray monochromatic representation is desired in some active matrix color liquid crystal display device having red, blue, and green secondary pixels.
The above-mentioned stripes are developed since the existing potential at the current picture signal line and the pixels connected thereto is deviated from a rated level because of the coupling to the parasitic capacitance upon supplying the adjacent picture signal line(s) with voltage from the signal source although the reference picture signal line and the associated pixels are in high impedance state while the pixel switch is closed and the reference picture signal line is disconnected from the signal source. Such coupling to the parasitic capacitance affects the picture signal lines selected the first and the last and the remaining ones differently from one another although they are connected to the common switch in the circuitry, and as a result, three different levels of the actual pixel voltage are developed, being deviated from the rated voltage, which causes the aforementioned artifact and/or the undesired tone.
Additionally, in driving any set of the adjacent picture signal lines in reverse polarity to each other, the signal source needs to supply voltage to each of the picture signal lines so as to make them assume alternately inverted polarity, and this also increases the deviation from the rated voltage which results in the artifact getting worse in addition to an increase of the power consumption.
With such a prior art multiplexer configuration, however, the picture buses in any single circuit must be supplied with signals of the same polarity. This is because it must be avoided to further deteriorate the resultant displayed picture due to fixing pixels at a level of voltage considerably deviated from the desired voltage level, which is resulted from an increase in electric power as a result of quick polarity reversing in the picture signal supply circuit and also from greater power loss as a result of capacity coupling between the buses and the pixels in comparison with the circuit featuring homogenized polarity of signals.
Such loss is caused by continuously selecting scan lines during selective driving of all the buses in the selected rows. All the busses and pixels turned in floating conditions after selecting the picture buses in some fixed order are affected and varied in potential from the fixed level in the amount of the divided capacity as a result of the capacity coupling when an adjacent one to any bus is selected and varied in potential. In this way, such potential variation of the adjacent bus twice affects the first selected bus and once affects all the remaining buses but the one selected last over a single cycle of the scanning.
Also, in the aforementioned prior art liquid crystal display apparatus where the multiplexers are used to supply the picture signal lines with picture signals on the timesharing basis, the scan lines are continuously selected while all the picture signal lines are being activated, and the buses and the pixels turned in floating conditions after the selections are affected and varied in potential from the fixed level by the divided capacity as a result of the capacity coupling when the adjacent one to any bus is selected and varied in potential.
In this way, such potential variation of the adjacent bus twice affects the first selected bus and once affects all the remaining buses but the one selected last over a single cycle of the scanning. Consequently, the resultant voltage is deviated from the targeted pixel voltage level, and this appears as inadvertently varied color or brightness.
Accordingly, it is an object of the present invention to provide an a.c. driven active matrix liquid crystal display device capable of inhibiting the aforementioned artifact of stripes as well as saving the power consumption, and a method of driving such a device.
According to one aspect of the present invention, there is provided an active matrix liquid crystal display device having a plurality of picture signal lines and a plurality of scan lines orthogonal to them, and a plurality of pixels arranged in matrix form and connected to the picture signal lines by switching elements intervening between them, comprising:
selection switches provided in the plurality of the picture signal lines on a substrate constituting a display device;
a plurality of picture signal sources smaller than the picture signal lines in number; and
a selective control device capable of selectively opening/closing the selection switches to skip connection with any picture signal line adjacent to each other, in the case that the plurality of picture signal sources are shared by the plurality of picture signal lines.
According to another aspect of the present invention, there is provided a method of driving an active matrix liquid crystal display device which is comprised of an active matrix liquid crystal display panel having a plurality of picture signal lines and a plurality of scan lines orthogonal to them, and a plurality of pixels in matrix and connected to the lines by switching elements intervening between them; selection switches provided in the plurality of the picture signal lines on a substrate constituting a display device; and a plurality of picture signal source smaller than the picture signal lines in number;
the method comprising the step of:
selectively opening/closing the selection switches to skip connection with any picture signal line adjacent to each other, thereby permitting the picture signal lines to share the picture signal sources smaller in number.
According to further aspect of the present invention, there is provided an active matrix liquid crystal display apparatus comprised of a plurality of picture signal lines and a plurality of scan lines orthogonal to them, and a plurality of pixels in matrix and connected to the lines by switching elements intervening between them, comprising selection switches respectively provided with the plurality of the picture signal lines on a substrate constituting a display device;
a plurality of picture signal source producing picture signals and smaller than the picture signal lines in number; and
a plurality of picture signal selecting circuits selecting a single picture signal line in one of groups of the picture signal lines and supplying picture signals from the picture signal sources on the time-sharing basis to the selected picture signal line;
The picture signal lines, which are simultaneously selected respectively by the picture signal selecting circuits, being arranged adjacent to one another.
According to still further aspect of the present invention, there is provided in a method of driving an active matrix liquid crystal display apparatus comprised of a plurality of picture signal lines and a plurality of scan lines orthogonal to them, an active matrix liquid crystal display panel including a plurality of pixels arranged in matrix from and connected to the lines by switching elements intervening between them, selection switches respectively provided with the plurality of the picture signal lines on a substrate constituting a display device and a plurality of picture signal sources producing picture signals and smaller than the picture signal lines in number, when the plurality of picture signal sources are shared among the plurality of the picture signal lines, corresponding selecting switches in adjacent picture signal lines to which the picture signal are provided by the picture signal sources are simultaneously selected.
In the active matrix liquid crystal device according to the present invention, a selection switch enables alternate ones of the picture signal lines to be connected to the signal source, and since the signal lines are divided in two groups such as a group of odd numbered ones and the other group of even numbered ones so that the connection sequence of the groups of them are varied from one of two consecutive periods to another, vivid stripes are prevented from coming up simply upon the connection to the picture signal lines related with any specific color, thereby enhancing the quality of the resultant picture displayed.
The similar effect can be attained by providing a plurality of picture signal lines adjacent to one another so that a plurality of picture signal selecting circuits synchronously select the picture signal lines.
When the adjacent picture signal lines are supplied with signals of the reversed polarities to each other, the method according to the present invention needs the switching of the polarity at the picture signal lines only twice during the single horizontal scan period, compared with the operation relying the sequential selection of the picture signal lines, and this effectively saves the power consumption.
Embodiments of the present invention will be described in detail in conjunction with the accompanying drawings.
As can be seen in
In the display panel 20, the TFTs 21 are arranged in matrix form of Y rows and X columns, and each TFT 21 has its gate electrode connected to a gate bus line (referred to as ‘gate line’ hereinafter) juxtaposed with each row of the TFTs and traversing the display field in the horizontal direction, and has its source electrode connected to a source bus line (abbreviated as ‘source line’ hereinafter) juxtaposed with each column of the TFTs and extending longitudinally across the display field. The TFTs 21 also have their respective drain electrodes connected to pixel electrodes 23 individually.
The display panel 20 provides a common electrode opposed to and spaced from the pixel electrodes 23, and liquid crystal is confined in the clearance between the common electrode and the pixel electrodes 23. Such a configuration is well known in the art, and therefore, omitted from the drawings.
The liquid crystal display device 10 is associated with driver circuits of a timing control circuit 30, a column driver circuit 40 controlled by the same, a column selection circuit 50, and a row selection circuit 60.
The timing control circuit 30 receives image data signals ‘data’ for respective colors, Red (R), Green (G), and Blue (B), clock signals CLK, and synchronization signals containing both horizontal and vertical synchronization signals from signal supply means (not shown), and then transfer the image data signals to the column driver circuit 40 and produces a latch signal St for synchronously driving the column selection circuit 50 and a control signal Gc for controlling the row selection circuit 60, respectively. The timing control circuit 30 also generates a voltage signal Vcom that is supplied to the common electrode 25 in the display panel 20.
The column driver circuit 40 receives the image data signal from the timing control circuit 30 to apply it to the picture signal lines. In this embodiment, six columns of the pixels are regarded as one set that are connected to the picture signal lines Sb11 to Sb16, respectively, with selection switches intervening between them. Specifically, the first column connected to the picture signal line Sb11 is connected to the common picture signal line IM1 via a switch SW11, the second column connected to the picture signal line Sb12 is connected to the common picture signal line IM1 via a switch SW12, and repeating similarly, and the sixth column connected to the picture signal line Sb16 is connected to the common picture signal line IM1 via a switch SW16. Similarly, the second set starts with the seventh column of the pixels. The seventh column connected to the picture signal line Sb21 is connected to the common picture signal line IM2. Repeating similarly, the twelfth column is connected to the common picture signal line IM2 via a switch SW26. Further similarly, the succeeding sets, each consisting of six columns of the pixels, are provided with the switches, and eventually, the final n-th set are provided with the switches SWn1 to SWn6 (n is an integer).
The column selection circuit 50 controls opening/closing the aforementioned groups of the switches SW respectively provided for the sets of the six picture signal lines. Specifically, upon receiving the latch signal St from the timing control circuit 30, the column selection circuit 50 divides a single period into six sub-periods to sequentially produce signals to six output lines for the sub-periods separately. The six output lines are used to control the switches provided for the set of the six columns of the pixels. For instance, the first output line is dedicated to the first switches, SW11, SW21, . . . , in the switch groups, the second output line is dedicated to the second switches, SW12, SW22, . . . , in the switch groups, and so forth.
In response to the control signal Gc received from the circuit 30, the row selection circuit 60 selectively applies a high voltage to the bus lines to selectively activate the gate lines in the display panel 20, for example. Any gate bus line activated in this manner turns the corresponding TFTs on so as to enable source signals applied to the current series of TFTs to simultaneously activate all of these TFTs in one line. In this way, the row of the pixels corresponding to the activated gate line are optically modulated simultaneously in response to a series of pixel data of one line.
The timing control circuit generates horizontal timing clock signals corresponding to scan lines between two consecutive vertical timing signals that indicate the commencement of a new frame in the field. An interval from the two consecutive horizontal timing signals is designated by a period of 1H during which the timing control circuit 30 and the column driver circuit 40 transfer a picture signal D to the common picture signal lines IM1, IM2, . . . . The column driver circuit 40 includes a digital-analog converter dedicated to each of the image data signals, R, G and B, and the image data signals of the respective colors are analog-converted for every horizontal scan period, so that a set of pixel signals (comprehensively referred to as ‘picture signal’ herein) are produced for each color, carrying a cluster of pixel data to be displayed during the single horizontal scan period (i.e., a single line of the pixel data in series).
On the other hand, in synchronization with the horizontal timing signals, the row selection circuit 60 produces row selection signals G1, G2, G3, and so forth, and the signals corresponding to the columns of the pixels permit the TFTs 21 in the selected columns to turn on.
The column selection circuit 50 produces column selection signals Ssw1 to Ssw6, which sequentially turn on the group of the switches SW dedicated to the set of the six columns of the pixels in the predetermined order. This permits every six TFTs in the identical row to be activated simultaneous with one another, thereby simultaneously carrying out optical modulation of the pixels activated by the corresponding picture signal lines Sb.
As a consequence, the rows selected at each horizontal timing are activated and the column selection signals sequentially turn the selection switches on, and hence, the TFTs in the corresponding column are turned on by the picture signal lines. The level of the picture signals applied to the TFTs in their ON-state is used as the reference the determine how much the TFTs should be activated to be sufficient to the image data given to display, and resultantly, the desired level of potential is applied to the pixel electrode 23 through the drain electrodes of those ON-state transistors. The electric field of a strength determined by the difference between the potential at the pixel electrodes and the voltage level applied the common electrode (not shown) effectively controls an orientation of the liquid crystal medium on the basis of one pixel electrode at a time. This manner enables the liquid crystal to modulate backlight irradiated from the back light system (not shown) and front light incident on the display device from the outside, depending upon the pixel data of each pixel. Operations of the liquid crystal display device are well known in the art, and therefore, the further explanation about them is omitted herein.
Then, the operation of the driver circuit 10 will be described. Before unique operations of the embodiment, an example of the operation based upon the fundamental technology of this embodiment will be outlined with reference to
In selecting the column electrodes in the frame (n), the picture signal lines are selected as in the order of Red 1 at time ta, Green 2 at time tb, Blue 3 at time tc, Red 4 at time td, Green 5 at time te, and Blue 6 at time tf, where at any moment of the selection, the polarity is also concurrently reversed at the moments indicated above.
In the next frame (n+1), the picture signal lines are selected as in the order of Red 1 at time tg, Green 2 at time th, Blue 3 at time tj, Red 4 at time tk, Green 5 at time tl, and Blue 6 at time tm, where at any moment of the selection, the polarity is also reversed.
As can be recognized, the column selections in the frame (n) and the frame (n+1) are fulfilled in the same order.
As to the line Red 1, the polarity reversal in the adjacent picture signal line Green 2 at time tb gives an effect of coupling to the capacitance to result in the voltage level dropping by one step. The polarity reversal in the line Blue 6 at time tf further reduces the voltage level, and thus, the total two-step drop is observed. Such a reduction of the voltage level eventually causes the development of the color red in the field. As for the remaining picture signal lines, the similar variation of the voltage level is recognized, but at most one-step drop or even minor as will be recognized in
Similarly, in the frame (n+1) where the alternate columns assume reversed polarities, the polarity reversal in the picture signal line Green 2 at time t3 and in the picture signal line Blue 6 at time t4, respectively, results in the voltage level rising by two steps to cause the color red accordingly as much to be developed. In the remaining picture signal lines of other colors, there arise adverse effects of the polarity reversal at the adjacent electrodes, but any variation in the voltage level will not exceed as much as two steps.
Assuming that such two-step level variation is expressed by ‘2’ while the single step level variation is ‘1’, the residual level variations for six of the column electrodes can be expressed in a sequence as (2, 1, 1, 1, 1, 0) in both the frame (n) and the frame (n+1). Consequently, red strips are more striking than others in the resultant frame picture, which causes the artifact of the red stripes in the field to significantly degrade the quality of the picture.
The present invention is advantageous to eliminate the striped artifact developed in the aforementioned manner.
In the frame (n), unlike the example depicted in
In the subsequent frame (n+1), however, the column selection signals and the column driving signals are produced in a different order from that in the frame (n). More specifically, the column selection signals are generated in the order of Ssw2, Ssw4, Ssw6, Ssw1, Ssw3, and Ssw5, and corresponding to this sequence of the selection signals, the column driving signal D is produced in series as in S2, S4, S6, S1, S3 and S5.
The polarity of the signal data applied to the selected picture signal lines are reversed in the frame (n) to that in the frame (n+1).
In this way, the previously selected group of the picture signal lines, once supplied with voltage, will not be affected by the coupling to the parasitic capacitance to vary from the existing potential upon the voltage supply to the picture signal lines orthogonal to those lines, unlike the prior art embodiment, and the subsequently selected group of the picture signal lines, after fully supplied with voltage, have their pixel potentials assuredly fixed at the end of selecting the scan lines of the pixels orthogonal to that group of the picture signal lines.
As in this embodiment, the order of selecting the signal sets or the signal line groups is varied from one frame to another in the present invention, and moreover, the order can be varied from one column to another, or otherwise, may be varied from one column to another and between the two consecutive frames. In either case, the required time from the previous selection of the picture signal lines to the activation of those selected next can be averaged, and, the operation efficiency, as a whole, can be enhanced.
In some frame (n), after the picture signal is selected as in the sequence of Red 1 at time t11, Blue 3 at time t12, and Green 5 at time t13, the polarity is reversed in the picture signal lines of Green 2 at time t14, Red 4 at time t15, and Blue 6 at time t16, respectively. As a consequence, the potential variation in the adjacent picture signal lines and the coupling to the parasitic capacitor result in the voltage level at the picture signal lines of Red 1, Blue 3 and Green 5 dropping by two steps. Corresponding to the voltage drop as much as the two steps, there arises the artifact of stripes of the colors of red, blue and green. The residual level variation can be expressed by (2, 0, 2, 0, 2, 0) as in the similar samples shown in
In the subsequent frame (n+1), the selection of the column electrodes is carried out as in the sequence of Green 2 at time t21, Red 4 at time t22, Blue 6 at time t23, Red 4 at time t24, Blue 3 at time t25, and Green 5 at time t26, and the level drop is caused as much as two steps, which develops the artifact of the stripes of the colors of red, green and blue, respectively. The stripes can be expressed by using the residual level variation in the picture signal lines as in (0, 2, 0, 2, 0, 2).
Since the frame (n) and the frame (n+1) are consecutive with each other, however, viewing over both the frames leads to the perception that there are developed the stripes of the same level for any corresponding columns in the frames, and they, as a whole, assume the color of gray which is invisible as the artifact.
When the adjacent signal lines are supplied with signals of the reversed polarities to each other, the method according to the present invention needs the switching of the polarity at the picture signal lines only twice during the single horizontal scan period, compared with the operation relying the sequential selection of the picture signal lines, and this effectively saves the power consumption.
In
On the other hand, the column selection in the second half of the frame (n+1) is completely reversed in the order to that in the first half of the frame (n). For instance, the picture signal line is selected in the sequence of Blue 6 at time t21, Red 4 at time t22, Green 2 at time t23, Green 5 at time t24, Blue 3 at time t25, and Red 1 at time t26, one after another. In this case, also, as in
As has been described, in the embodiments shown in
Referring to
The polarity reversal during the transition from the frame (n) to the frame (n+1) is different from that of
Specifically, as to the picture signal line of Green 2, upon the polarity reversal, the inherent low potential is further dropped by two steps due to the effect of the other picture signal line(s). Although its potential is normally raised to the predetermined positive level, the potential at the picture signal line is expected to raise its level twice due to the polarity reversal in the adjacent picture signal line(s) in the future, and therefore, a potential increase as much as the predicted rise needs not to be raised. Thus, the potential is raised to the level two-step lower than the inherent peak level. Such circumstances occur in common for the picture signal lines of Red 4 and Blue 6. The bottom level at the picture signal lines of Red 1, Blue 3 and Green 5 is gradually raised due to the polarity reversal in the adjacent picture signal line(s), and a potential increase as much as the rise by two steps causes the stripes for each color. As the polarity of the stripes is negative, the residual level variation can be expressed by (−2, 0, −2, 0, −2, 0).
Thus, the stripes derived from the picture signal lines of Red 1, Blue 3 and Green 5 for two cycles (n) and (n+1) countervail one another, and the striped artifact is not observed.
In this embodiment, the potential variation in the future is preliminarily counted in to raise the potential to a level as satisfied after the polarity reversal, and hence, the power consumption can be reduced.
In the aforementioned embodiment, since the field essentially consists of three colors, the column electrodes as many as multiples of three can be selected (e.g., six of the columns), but the number of colors may be optionally increased or decreased although sets of the columns subjected to the selection must be even in number.
Furthermore, although the columns of the electrodes can be selected so that more than one columns are permitted to selectively connect with the picture signal lines in the aforementioned embodiment according to the present invention, rows of the electrodes instead of the columns may be selected in some construction of the display device so as to selectively connect more than one rows to the picture signal lines.
Although the column selection is carried out for each unit period of the horizontal scanning, the vertical period may be the alternative to the unit period.
When one frame is read out in the sequence different from that in another frame, various orders can be contemplated as well as the sequence described in the embodiments.
The present invention can also be applied to active matrix liquid crystal display devices activated on the basis of row-to-row reversed polarity in addition to those activated on the basis of column-to-column reversed polarity in order to attain the similar effects of saving the supplied power of the picture signal source and stably providing quality pictures. The present invention can be further applied to active matrix liquid crystal display device activated on the basis of both the row-to-row polarity reversal and the frame-to-frame polarity reversal so as similarly to stably provide quality pictures.
Referring to
In this embodiment, two of the multiplexers together serve as a primary part as in the embodiment in
On the other hand, ones of the selecting switches for both of the multiplexers, which are related to a specific pair of the adjacent picture signal lines, are turned simultaneously on and off by the column selection circuit 55. For instance, the switch SW1 associated with the picture signal line C1 and the switch SW4 associated with the picture signal line C2 adjacent to the signal line C1 are turned simultaneously on and off based on a shared selecting signal SSW1, and the remaining switches are connected in the similar operative manner.
During the subsequent column selection period, the switches SW1 and SW2 are turned off while the selection signal SSW2 causes the switches SW2 and SW5 to turn simultaneously on so as to make the picture signal sources supply picture signals C3n and C4n to the picture signal liens C3 and C4, respectively. The similar sequence is applied to each of the remaining pairs of the adjacent picture signal lines to produce picture signals thereto.
With such control, the adjacent picture signal lines in pair are simultaneously selected and simultaneously varied in state, and hence, no coupling loss is observed between the adjacent picture signal lines.
On the other hand, there arises the coupling loss between the adjacent picture signal lines respectively activated during different selection periods, and this brings about two types of signal line pairs at the same time in the single circuitry; that is, the ones that would not cause such coupling loss and the ones that would cause the coupling loss. During a single scanning period of time. However, such loss is theoretically identical in amount for any bus pair so that no level shift is caused as observed in the prior art as a transient between two levels.
Applying the configuration of this embodiment to the following execution sequence can attain the similar effects.
In this case, producing the selection signals SSW1, SSW2, and SSW3 simultaneously from the column selection circuit permits all the selecting switches SW1 to SW6 for both the multiplexers to turn on at the same time so as to energize all the picture signal lines and convert their polarity into the writable or their voltage level to the ground potential in advance, and subsequently, the switches are sequentially turned off, starting with opening the switches SW1 and SW2.
With the execution in such a manner, all the data lines are energized to reach the approximate targeted level of voltage in advance, and an instantaneous inspection proves that the voltage variation due to the capacity coupling is reduced to a half while an additional inspection for a single frame gives a level equivalent to a root-mean-square (rms) value. In this way, the level variation can be more effectively restricted.
In another case, a possible application to the execution sequence is as follows.
In this case, a selecting time for each bus is determined depending upon the number of buses that are to be activated simultaneously. Specifically, a period of time for which all the buses are being selected is several times as long as the time spent to select only a single bus.
With the execution in such a manner, the amplifier as a whole can reduce its driving power, and this leads to a reduction of the total power consumption.
As has been described, this embodiment using the multiplexers to selectively activate specific pairs of the adjacent picture signal lines can restrict color variations especially in the intermediate gradation that is caused by the voltage level variations due to the coupling of the adjacent buses in the prior art circuit configuration when those buses are in their respective floating conditions. It is especially noted that even if the adjacent buses are activated at the reversed polarity, such reduction of the voltage level can be attained.
As has been described in the case particularly allowing for three of the picture signal lines C1 to C3, the switches SW1 to SW3 associated with the picture signal lines are sequentially selected during the scanning period of time, and upon receiving data from the picture signal sources, a coupling capacity between the adjacent pixels and signal liens results in the potential being varied from one picture signal line to another, despite the identical voltage supply, as denoted by the relation as Vc3>Vc2>Vc1.
Therefore, in this case, it is devised that the voltage compensating for the known potential variations is applied to the picture signal source.
In
Configured in this way, the potential of the picture signal lines can be prevented from varying during the operation so as to enable more accurate signal detections, and thus, the resultant picture can be enhanced in quality.
In this case, also, the potential of the picture signal lines can be prevented from varying so as to attain the enhanced quality of the picture.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-277831 | Sep 2004 | JP | national |
| 2005-132943 | Apr 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2005/053117 | 9/22/2005 | WO | 00 | 7/1/2008 |
