Patent Abstract:
The present invention provides an image processing circuit for use in an electrooptic device having a plurality of scanning lines, a plurality of data lines, switching elements which are respectively disposed in correspondence with intersections between the scanning lines and the data lines, and pixel electrodes which are electrically coupled to the corresponding switching elements. The image processing circuit includes a delay circuit that delays externally supplied image data by a unit time so as to output delayed image data, first correction-data generation circuit that generates correction data on the basis of data which has been obtained by averaging a difference between the image data and the delayed image data every unit time, second correction-data generation circuit that generates second correction data on the basis of data which has been obtained by averaging a difference between the image data and predetermined reference data every unit time, correction circuit that generates corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data, and a phase expansion circuit which divides the corrected image data into a plurality of phase-expanded video signals and which feeds the phase-expanded video signals to the plurality of data lines. Thus, block ghosting can be cancelled in a case where an image is displayed by successively selecting blocks in each of which a plurality of data lines are collected.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The present invention relates to an image processing circuit as well as an image data processing method suited for application to an electrooptic device, wherein video signals obtained by dividing a video signal into a plurality of channels and extending the time axis thereof, so as to maintain a predetermined signal level every unit time, are fed to corresponding data lines at a predetermined timing. Also, it relates to an electrooptic device and electronic equipment which employ such a processing circuit or method.  
           [0003]    2. Description of Related Art  
           [0004]    A conventional electrooptic device, for example, an active matrix-type liquid-crystal display device, will be explained with reference to FIGS. 11 and 12. First, as shown in FIG. 11, the conventional liquid-crystal display device is constructed of a liquid-crystal display panel  100 , a timing circuit  200 , and a video signal processing circuit  300 . The timing circuit  200  outputs timing signals for use in various portions. The video signal processing circuit  300  can include a D/A converter circuit  301  that converts image data Da supplied by external equipment from a digital signal into an analog signal and outputs the resulting signal as a video signal VID. Further, a phase expansion circuit  302  can be included that expands the received video signal VID of one channel into video signals of N phases (N=6 in the figure) and outputs the resulting video signals. Here, the video signal is expanded into N phases by a sampling circuit so that a time period for which the video signal fed to thin film transistors (TFTs) is applied is lengthened, thereby sufficiently securing a sampling time period for the data signals and a charge/discharge time period for the TFT panel  100  for the data signals.  
           [0005]    In turn, an amplifier/inverter circuit  303  subjects the video signals to polarity inversion under the following conditions and amplifies the inverted signals as required, so as to feed phase-expanded video signals VID 1 -VID 6  to the liquid-crystal display panel  100 . Here, “polarity inversion” signifies alternately inverting the voltage levels of the video signals with respect to a reference potential set at the center potential of the amplitudes of the video signals. Besides, the inversion of the video signals is done when the method of applying the data signal is (1) polarity inversion in scanning line units, (2) polarity inversion in data signal line units, or (3) polarity inversion in pixel units, and the inversion period is set at one horizontal scanning period or one dot clock period.  
           [0006]    The liquid-crystal display panel  100  can be constructed so that an element substrate and a counter substrate are opposed to each other with a gap defined therebetween, and a liquid crystal is enclosed in the gap. Here, each of the element substrate and the counter substrate can be made of a quartz substrate, a hard glass, or the like.  
           [0007]    In the element substrate, a plurality of scanning lines  112  are arrayed and formed in parallel so as to extend in the X-direction in FIG. 12, while a plurality of data lines  114  are formed in parallel so as to extend in the Y-direction orthogonal to the scanning lines  112 . Here, the data lines  114  are divided into blocks each consisting of six lines, and the blocks are termed “blocks B 1 -Bm”. For brevity of the ensuing explanation, when referring to the data lines in general, they will be designated by the reference numeral  114 , but when referring to specified ones of the data lines  114 , they will be designated by reference numerals  114   a - 114   f.    
           [0008]    At the intersection points between the scanning lines  112  and the data lines  114 , TFTs  116  are connected as switching elements, by way of example. More specifically, the gate electrodes of the TFTs  116  are connected to the scanning lines  112 , while the source electrodes thereof are connected to the data lines  114 , and the drain electrodes thereof are connected to pixel electrodes  118 . Individual pixels are configured of the pixel electrodes  118 , a common electrode formed on the counter substrate, and the liquid crystal sandwiched in between both the electrodes, and they are arrayed in the shape of a matrix at the intersection points between the scanning lines  112  and the data lines  114 . Incidentally, retention capacitors (not shown) are further formed in a state where they are respectively connected to the pixel electrodes  118 .  
           [0009]    Meanwhile, a scanning line driver circuit  120  can be formed on the element substrate, and the scanning line driver circuit  120  outputs pulse-like scanning signals to the respective scanning lines  112  in succession on the basis of a clock signal CLY, the inverted clock signal CLYinv thereof, a transfer start pulse DY, etc. delivered from the timing circuit  200 . More specifically, the scanning line driver circuit  120  successively shifts the transfer start pulse DY fed at the beginning of a vertical scanning period in accordance with the clock signal CLY and the inverted clock signal CLYinv, and it outputs the resulting signals as scanning line signals, to thereby successively select the respective scanning lines  112 .  
           [0010]    On the other hand, a sampling circuit  130  includes a sampling switch  131  at one end of each of the data lines  114 . The switches  131  can be made of TFTs which are also formed on the element substrate, and the source electrodes of these switches  131  are fed with the corresponding video signals VID 1 -VID 6  through video signal feed lines L 1 -L 6 . Besides, the gate electrodes of the six switches  131  connected to the data lines  114   a - 114   f  of the block B 1  are connected to a signal line which is fed with a sampling signal S 1 , and those of the six switches  131  connected to the data lines  114   a - 114   f  of the block B 2  are connected to a signal line which is fed with a sampling signal S 2 . Likewise, the gate electrodes of the six switches  131  connected to the data lines  114   a - 114   f  of the block Bm are connected to a signal line which is fed with a sampling signal Sm. Here, each of the sampling signals S 1 -Sm is a signal for sampling the video signals VID 1 -VID 6  every block within a horizontal effective display period.  
           [0011]    A shift register circuit  140  is also formed on the element substrate, and the shift register  140  outputs the sampling signals S 1 -Sm in succession on the basis of a clock signal CLX, the inverted clock signal CLXinv thereof, a transfer start pulse DX, etc. delivered from the timing circuit  200 . More specifically, the shift register circuit  140  successively shifts the transfer start pulse DX fed at the beginning of the horizontal scanning period in accordance with the clock signal CLX and the inverted clock signal CLXinv, and it successively outputs the resulting signals as the sampling signals S 1 -Sm.  
           [0012]    In such a construction, when the sampling signal S 1  is outputted, the video signals VID 1 -VID 6  are respectively sampled by the six data lines  114   a - 114   f  belonging to the block B 1 , and they are respectively written into the six pixels associated with the selected scanning lines at the current time by the corresponding TFTs  116 .  
           [0013]    Thereafter, when the sampling signal S 2  is outputted, the video signals VID 1 -VID 6  are respectively sampled by the six data lines  114   a - 114   f  belonging to the block B 2 , on this occasion, and they are respectively written into the six pixels associated with the selected scanning lines at that time by the corresponding TFTs  116 .  
           [0014]    Likewise, when the sampling signals S 3 , S 4 , . . . and Sm are successively outputted, the video signals VID 1 -VID 6  are respectively sampled by the six data lines  114   a - 114   f  belonging to the blocks B 3 , B 4 , . . . and Bm, and they are respectively written into the six pixels associated with the selected scanning lines at those times. Then, the next scanning lines are subsequently selected, and similar write operations are repeatedly executed in the blocks B 1 -Bm.  
           [0015]    With the above driving system, the number of stages of the shift register circuit  140  for driving and controlling the switches  131  in the sampling circuit  130  is reduced to ⅙ as compared with the number of stages in a system in which the respective data lines are driven in point sequence. Moreover, the frequencies of the clock signal CLX and the inverted clock signal CLXinv to be fed to the shift register circuit  140  may be as small as ⅙, so that a lower power dissipation can be attained along with a reduction in the number of stages.  
           [0016]    However, in the system in which a video signal of one channel is subjected to phase expansion into a plurality of channels so as to drive a liquid-crystal display panel by employing multi-channel video signals, there can be a problem in that gradations to be displayed deviating from the desired ones are displayed in block units (hereinbelow, the phenomenon shall be termed “block ghost”).  
           [0017]    By way of example, consider a liquid-crystal display panel which operates in a normally-white mode, and one screen of which is constituted by blocks B 1 -B 7 , as shown in FIG. 13A. It is assumed that black is displayed in the blocks B 1 -B 3  and in the area b 41  of the block B 4 , as shown in FIG. 13B, while a gray level is displayed in the area b 42  of the block B 4  and in the blocks B 5 , B 6  and B 7 . Then, the area b 42  becomes somewhat brighter than the gray level, and the following block B 5  becomes somewhat darker than the gray level.  
           [0018]    As a result of repeated experiments and studies on such block ghosts, it has been found that the major factors of the block ghost are the two factors stated below.  
           [0019]    In the liquid-crystal display panel  100  shown in FIG. 12, an equivalent circuit concerning the i-th block Bi is as shown in FIG. 14. Referring to FIG. 14, letter R indicates the equivalent resistance of the counter electrode (common electrode). Since the liquid crystal is sandwiched between the video signal feed lines L 1 -L 6  and the counter electrode, parasitic capacitances appear. Reference characters Cxa-Cxf denote the parasitic capacitances as equivalent capacitances. Further, reference characters  131   a - 131   f  denote the sampling switches  131  which correspond to the respective video signal feed lines L 1 -L 6 . In addition, reference characters Cya-Cyf denote the parasitic capacitances of the data lines  114   a - 114   f  (chiefly appearing between these data lines and the counter electrode) and the capacitances of pixel capacitors as equivalent capacitances.  
           [0020]    The first factor consists in the point that differentiator circuits are formed by the equivalent capacitances Cxa-Cxf and the resistance R, so when the video signals VID 1 -VID 6  are inputted to the liquid-crystal display panel  100 , a waveform corresponding to the magnitude of the voltage changes of the video signals VID 1 -VID 6  is generated on the counter electrode.  
           [0021]    The second factor is that voltage change of the counter electrode is due to charging/discharging in the case where the block Bi is selected. More specifically, when the block Bi is selected to turn ON the switches  131   a - 131   f , the equivalent capacitances Cya-Cyf are charged/discharged from an initial voltage Vs (the voltage at the nodes between the equivalent capacitances Cya-Cyf and the switches  113   a - 113   f  at the start of the selection time period of the block Bi) to the voltages of the video signals VID 1 -VID 6 . The second factor results from a differential waveform being generated on the counter electrode by charging/discharging currents on this occasion.  
           [0022]    The voltage distortions of the differential waveforms caused by the first and second factors appear at the start of the selection time period of the block Bi, and attenuate over time. Letting Ve denote an error voltage which remains on the counter electrode at the end of the selection time period of the block Bi, non-uniformity in display occurs unless Ve is set to zero. The reason is that the switches  113   a - 113   f  are turned OFF at the end of the selection time period, so voltages affected by the error voltage Ve are held in the pixel capacitors.  
           [0023]    A first error voltage Ve 1  attributable to the first factor is given by the following equation (1), where α denotes a constant, and V k,i  denotes the video signal which is to be fed to the k-th data line in the i-th block:  
             Ve1   =     α          ∑     k   =   1     6          (       V     k   ,   t       -     V     k   ,     i   -   1           )                 (   1   )                               
 
           [0024]    A second error voltage Ve 2  attributable to the second factor is given by the following equation (2), where β denotes a constant:  
             Ve2   =     β          ∑     k   =   1     6          (       V     k   ,   1       -   Vs     )                 (   2   )                               
 
           [0025]    Accordingly, the error voltage Ve which is the total of the error voltages Ve 1  and Ve 2  is given by the following equation (3):  
             Ve   =       α          ∑     k   =   1     6          (       V     k   ,   i       -     V     k   ,     i   -   1           )         +     β          ∑     k   =   1     6          (       V     k   ,   i       -   Vs     )                   (   3   )                               
 
           [0026]    Using equations (1)-(3), luminance changes in the blocks B 3  to B 5  shown in FIG. 13B will be studied. Here, as shown in FIG. 13B, it is assumed that a black level Vb is fed to the four left-hand data lines (in the area b 41 ) among the six data lines  114   a - 114   f  constituting the block B 4 , that a gray level Vc is fed to the two right-hand data lines (in the area b 42 ), and that the initial voltage Vs agrees with the gray level Vc.  
           [0027]    First, consider the change of the luminance level of the block B 3  at I=3. As shown in FIG. 13A, the block B 2  directly preceding the block B 3  displays black similarly to the block B 3 . Therefore, both the terms V k,i  and V k,i−1  in equation (1) become the black level Vb, and Ve 1 =0 holds. Since the initial voltage Vs agrees with the gray level Vc, Ve 2 =6β(Vb−Vc)&gt;0 holds. Accordingly, the error voltage Ve becomes positive, and the block B 3  brightens. Human vision, however, cannot substantially detect a luminance change for black though it can detect even a slight luminance change for a gray level. Therefore, a person would hardly notice that the block B 3  has become brighter.  
           [0028]    Secondly, regarding the block B 4 , black is displayed in the ⅔ area b 41 , and a gray level is displayed in the remaining ⅓ area b 42 . Therefore, Ve 1 =−2α(Vb−Vc)&lt;0 and Ve 2 =4β(Vb−Vc)&gt;0 hold. Whether the error voltage Ve takes a positive value or a negative value, depends upon the values of the constants α and β. In general, the values of the equivalent capacitances Cya-Cyf are greater than those of the equivalent capacitances Cxa-Cxf, so that β&gt;α holds in many cases. Accordingly, the error voltage Ve usually becomes positive, and the entire block B 4  brightens. Owing to the visual characteristic stated above, however, a person can detect that the area b 42  displaying the gray level has brightened, though they hardly notices that the luminance of the area b 41  displaying black has increased.  
           [0029]    Thirdly, since the gray level is displayed in the block B 5 , Ve 1 =−4α(Vb−Vc)&lt;0 and Ve 2 =0 hold, and the error voltage Ve takes a negative value. Therefore, the block B 5  darkens.  
         SUMMARY OF THE INVENTION  
         [0030]    The present invention has been made in view of the above circumstances, and has one object to strongly enhance the display quality in such a way that, in a case where a gray level to be displayed changes midway in a block, block ghosting in the remaining area (for example, b 42 ) of the pertinent block and in the next block (for example, B 5 ) are cancelled.  
           [0031]    In order to accomplish the object, an image processing circuit according to a first aspect of the present invention is an image processing circuit for use in an electrooptic device having a plurality of scanning lines, a plurality of data lines, switching elements which are respectively disposed in correspondence with intersections between the scanning lines and the data lines, and pixel electrodes which are electrically connected to the corresponding switching elements. The image processing circuit can include a delay circuit which delays externally supplied image data by a unit time so as to output delayed image data, a first correction-data generation circuit for generating first correction data on the basis of data which has been obtained by averaging a difference between the image data and the delayed image data every unit time, a second correction-data generation circuit for generating second correction data on the basis of data which has been obtained by averaging a difference between the image data and predetermined reference data every unit time, a correction circuit for generating corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data, and a phase expansion circuit which divides the corrected image data into a plurality of phase-expanded video signals and which feeds the phase-expanded video signals to the plurality of data lines.  
           [0032]    In the electrooptic device to which the invention is applied, an image is displayed on the basis of phase-expanded video signals divided into a plurality of channels. In this regard, parasitic capacitances occur in video signal feed lines which lead to the corresponding data lines. Further, parasitic capacitances also occur in the data lines themselves, and pixel capacitors are disposed. Moreover, a distributed resistance exists in a counter electrode. Therefore, differentiator circuits are equivalently formed between the video signal feed lines and the counter electrode, while differentiator circuits are equivalently formed between the data lines and the counter electrode. Accordingly, when the signal level of a video signal which is fed to the electrooptic device changes, a first error voltage is induced in the counter electrode by the differentiator circuit formed between the video signal feed line and the counter electrode. Moreover, when a certain one of the data lines is selected, charging/discharging takes place, so that the second error voltage of the counter electrode changes. Ghosting can be caused by these factors.  
           [0033]    According to the first aspect of present invention, the first correction-data generation circuit can average the first difference data every unit time, thereby generating the first correction data, which corresponds to the first error voltage. The second correction-data generation means averages the second difference data every unit time, thereby generating the second correction data, which corresponds to the second error voltage. That is, the first and second correction data correspond to the voltage changes of the counter electrode as predicted. The corrected image data is generated by correcting the delayed image data on the basis of the first and second correction data, so that even when the first and second error voltages occur in the counter electrode, they can be cancelled by generating the video signals on the basis of the corrected image data. As a result, the block ghosting can be greatly reduced and the quality of a displayed image can be strongly enhanced.  
           [0034]    In the first aspect of performance of the present invention, the first correction-data generation circuit can preferably include a first subtracter circuit which calculates the difference between the image data and the delayed image data as first difference data, a first averaging circuit which generates first average data obtained by averaging the first difference data every unit time, and a first coefficient circuit which generates the first correction data by multiplying the first average data by a first coefficient.  
           [0035]    The first averaging circuit may preferably include an accumulator circuit which accumulates the first difference data every unit time, and a divider circuit which divides the accumulated result by the number of the video signals divided the corrected image data into the plurality of phase-expanded video signals.  
           [0036]    In the first aspect of the present invention, the second correction-data generation circuit can include a second subtracter circuit which calculates the difference between the image data and the reference data as second difference data, a second averaging circuit which generates second average data obtained by averaging the second difference data every unit time, and a second coefficient circuit which generates the second correction data by multiplying the second average data by a second coefficient.  
           [0037]    The second averaging circuit can include an accumulator circuit which accumulates the second difference data every unit time, and a divider circuit which divides a result of the accumulation by the number of the video signals divided the corrected image data into the plurality of phase-expanded video signals.  
           [0038]    Accordingly, the accumulated results are divided by the number of the divided video signals (the number of the phase-expanded video signals), so that the first and second difference data averaged in each block can be calculated.  
           [0039]    Preferably, the reference data corresponds to an initial voltage which is applied to pixel capacitors including the pixel electrodes, a counter electrode held opposite to the pixel electrodes, and an electrooptic material.  
           [0040]    Alternatively, the reference data may be a precharge voltage which is applied to pixel capacitors including the pixel electrodes, a counter electrode held in opposition to the pixel electrodes, and an electrooptic material.  
           [0041]    Since the second error voltage described above is due to the charging/discharging, the changes of the voltages of the data lines and the pixel capacitors become problematic. Therefore, the initial voltage or the precharge voltage can be employed as the reference data. In the actual electrooptic device, however, the optimum value of the reference data can deviate from the initial or precharge voltage on account of various factors, and hence, the reference data may be essentially set so as to visually minimize the block ghosting.  
           [0042]    The electrooptic device can further include a plurality of switching elements which sample the respective phase-expanded video signals in accordance with sampling signals and which feed them to the corresponding data lines, and video signal feed lines which feed the respective video signals to the corresponding switching elements. The first coefficient of the first coefficient circuit may preferably be determined on the basis of, at least, parasitic capacitance components due to the respective video signal feed lines and a resistance component of a counter electrode held opposite to the pixel electrodes. Thus, the ghosting attributable to the first error voltage can be effectively cancelled.  
           [0043]    The second coefficient of the second coefficient circuit may preferably be determined on the basis of, at least, parasitic capacitance components due to the respective data lines and a resistance component of a counter electrode held opposite to the pixel electrodes. Thus, the ghosting attributable to the second error voltage can be effectively cancelled.  
           [0044]    An image processing circuit according to a second aspect of the present invention can include a delay circuit which delays externally supplied image data by a unit time so as to output delayed image data, a first correction-data generation circuit that generates first correction data on the basis of data which has been obtained by averaging a difference between the image data and the delayed image data every unit time, a second correction-data generation circuit that generates second correction data on the basis of data which has been obtained by averaging a difference between the image data and predetermined reference data every unit time and a correction circuit that generates corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data.  
           [0045]    According to the second aspect of the present invention, the first correction-data generation circuit averages the first difference data every unit time, thereby generating the first correction data, which corresponds to a first error voltage. The second correction-data generation circuit averages the second difference data every unit time, thereby generating the second correction data, which corresponds to a second error voltage. That is, the first and second correction data correspond to the voltage changes of a counter electrode as predicted. The corrected image data is generated by correcting the delayed image data on the basis of the first and second correction data, so that even when the first and second error voltages occur in the counter electrode, they can be cancelled by generating video signals on the basis of the corrected image data. As a result, block ghosting can be substantially reduced and the quality of the displayed image can be strongly enhanced.  
           [0046]    An electrooptic device according to a third aspect of the present invention can include a plurality of scanning lines, a plurality of data lines, switching elements which are respectively disposed in correspondence with intersections between the scanning lines and the data lines, pixel electrodes which are respectively electrically connected to the switching elements, and a delay circuit which delays externally supplied image data by a unit time so as to output delayed image data. The device can further include a first correction-data generation circuit for generating first correction data on the basis of data which has been obtained by averaging a difference between the image data and the delayed image data every unit time, a second correction-data generation circuit for generating second correction data on the basis of data which has been obtained by averaging a difference between the image data and predetermined reference data every unit time, a correction circuit for generating corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data, and a phase expansion circuit which divides the corrected image data into a plurality of phase-expanded video signals and which feeds the phase-expanded video signals to the plurality of data lines.  
           [0047]    According to the electrooptic device, block ghosting can be substantially reduced and quality of the displayed image can be strongly enhanced.  
           [0048]    Preferably, the above electrooptic device may further include a data line driver circuit which generates sampling signals in succession; and a sampling circuit which samples the phase-expanded video signals on the basis of the sampling signals and feeds the sampled signals to the corresponding data lines.  
           [0049]    According to this electrooptic device, the quality of the display image can be strongly enhanced, and a time period for which the video signals are fed to the data lines can be lengthened.  
           [0050]    Electronic equipment according to the present invention is characterized by including the electrooptic device described above, and includes, for example, a video projector, a notebook-type personal computer, and a mobile telephone.  
           [0051]    A a first image data processing method according to a fourth aspect of the present invention is an image data processing method for use in an electrooptic device wherein video signals are fed to a plurality of data lines. The method includes the steps of generating delayed image data by delaying externally supplied image data by a unit time, generating a difference between the image data and the delayed image data as first difference data, generating first average data by averaging the first difference data every unit time, generating first correction data by multiplying the first average data by a first coefficient, generating a difference between the image data and predetermined reference data as second difference data, generating second average data by averaging the second difference data every unit time, generating second correction data by multiplying the second average data by a second coefficient, generating corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data, and dividing the corrected image data into the plurality of phase-expanded video signals, and then feeding said video signals to the plurality of data lines.  
           [0052]    According to this image data processing method, the first correction data corresponds to a first error voltage, and the second correction data corresponds to a second error voltage, so that the first and second correction data correspond to the voltage changes of a counter electrode as predicted. The corrected image data is generated by correcting the delayed image data on the basis of the first and second correction data, so that even when the first and second error voltages occur in the counter electrode, they can be cancelled by generating the video signals on the basis of the corrected image data. As a result, block ghosting can be substantially reduced and the quality of the displayed image can be strongly enhanced.  
           [0053]    An image data processing method according to a fifth aspect of the present invention can include the steps of generating delayed image data by delaying externally supplied image data by a unit time, generating a difference between the image data and the delayed image data as first difference data, generating first average data by averaging the first difference data every unit time, generating first correction data by multiplying the first average data by a first coefficient, generating a difference between the image data and predetermined reference data as second difference data, generating second average data by averaging the second difference data every unit time, generating second correction data by multiplying the second average data by a second coefficient, and generating corrected image data by correcting the delayed image data on the basis of the first correction data and the second correction data.  
           [0054]    According to this image data processing method, block ghosting can be substantially reduced and the quality of the displayed image can be greatly enhanced.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0055]    The invention is described in detail with reference to the following Figures, wherein like numerals reference like elements, and wherein:  
         [0056]    [0056]FIG. 1 is an exemplary block diagram showing the overall construction of a liquid-crystal display device in accordance with the present invention;  
         [0057]    [0057]FIG. 2 is a block diagram showing the construction of a deghosting circuit in the liquid-crystal display device;  
         [0058]    [0058]FIG. 3 is a block diagram showing the construction of a phase expansion circuit in the liquid-crystal display device;  
         [0059]    [0059]FIG. 4 is a timing chart showing the operation of a first correction unit of the deghosting circuit;  
         [0060]    [0060]FIG. 5 is a timing chart showing the operation of a second correction unit of the deghosting circuit;  
         [0061]    [0061]FIG. 6 is a timing chart showing the operation of the phase expansion circuit in the liquid-crystal display device;  
         [0062]    [0062]FIG. 7 is a timing chart of phase-expanded video signals in the case of phase-expanding image data without employing the deghosting circuit, and corrected image data generated by employing the deghosting circuit;  
         [0063]    [0063]FIG. 8 is a sectional view showing the construction of a projector which is an example of electronic equipment to which the liquid-crystal display device is applied;  
         [0064]    [0064]FIG. 9 is a perspective view showing the construction of a personal computer which is an example of electronic equipment to which the liquid-crystal display device is applied;  
         [0065]    [0065]FIG. 10 is a perspective view showing the construction of a portable telephone which is an example of electronic equipment to which the liquid-crystal display device is applied;  
         [0066]    [0066]FIG. 11 is a block diagram showing the overall construction of a conventional liquid-crystal display device;  
         [0067]    [0067]FIG. 12 is a connection diagram showing the electrical construction of a liquid-crystal display panel in the conventional liquid-crystal display device;  
         [0068]    [0068]FIGS. 13A and 13B are explanatory diagrams showing an example of ghosting; and  
         [0069]    [0069]FIG. 14 is a circuit diagram showing an equivalent circuit in a given block.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0070]    First, an active matrix-type liquid-crystal display device will be described as an example of an electrooptic device according to the present invention.  
         [0071]    [0071]FIG. 1 is a block diagram showing the overall construction of the liquid-crystal display device. The liquid-crystal display device in this embodiment is constructed similarly to the conventional liquid-crystal display device shown in FIG. 11, except that, in a video signal processing circuit  300 A, a deghosting circuit  304  is included at a stage preceding a D/A converter  301 . The image data Da in this example can be a data string which has 8 bits in a parallel and whose sampling period is equal to the period of a dot clock signal DCLK, and it is supplied by external equipment (not shown).  
         [0072]    The deghosting circuit  304  predicts block ghost components caused by the first and second factors explained above, and corrects the image data Da so as to cancel the predicted block ghost components, thereby generating corrected image data Dout.  
         [0073]    A phase expansion circuit  302  subjects a video signal VID obtained by D/A-converting the corrected image data Dout, to serial-to-parallel conversion, thereby generating phase-expanded video signals VID 1 -VID 6  expanded into six phases. More specifically, the phase expansion circuit  302  samples-and-holds the video signal VID on the basis of a sample-and-hold pulse SS and 6-phase sample-and-hold pulses SP 1 -SP 6 , which become active every six cycles of the dot clock signal DCLK, so as to extend the time axis of the video signal VID by a factor of six, and it divides the extended video signal into six channels, thereby generating the phase-expanded video signals VID 1 -VID 6 .  
         [0074]    The phase-expanded video signals VID 1 -VID 6  are generated on the basis of the video signal VID obtained by D/A-converting the corrected image data Dout in synchronization with the dot clock signal DCLK. Therefore, if the value of the original corrected image data Dout changes every dot clock cycle, the respective phase-expanded video signals VID 1 -VID 6  change every six dot clock cycles. Accordingly, the phase-expanded video signals VID 1 -VID 6  become signals which change with one unit time being a time period that is determined by the product between the number of expanded phases (the number of divided channels) and one cycle of the dot clock signal DCLK.  
         [0075]    A liquid-crystal display panel  100  is the same as that employed in the conventional liquid-crystal display device shown in FIG. 12, and therefore a description is omitted here.  
         [0076]    [0076]FIG. 2 is a detailed circuit diagram of the deghosting circuit  304 . As shown, the deghosting circuit  304  is constructed of a delay unit Ud, a first correction unit Uh 1 , a second correction unit Uh 2 , and a subtracter circuit  45 .  
         [0077]    First, the delay unit Ud is constructed by connecting six latch circuits LAT 1 -LAT 6  in series, and it delays the image data Da by a predetermined time period so as to output image data Db. Here, the latch circuits LAT 1 -LAT 6  latch the 8-bit input data Da on the basis of the dot clock signal DCLK.  
         [0078]    The dot clock signal DCLK is the master clock of the liquid-crystal display device, and is generated in the timing circuit  200 . The timing circuit  200  divides the frequency of the dot clock signal DCLK so as to generate a clock signal CLX for driving the data line driver circuit of the liquid-crystal display panel  100 , and a clock signal CLY for driving the scanning line driver circuit thereof. In this example, phase expansion into six phases is carried out in the phase expansion circuit  302 . Therefore, the clock signal CLX is generated by dividing the frequency of the dot clock signal DCLK by 6.  
         [0079]    Since the delay unit Ud is constructed of the series connection consisting of the six latch circuits LAT 1 -LAT 6  which are driven by the dot clock signal DCLK, the image data Db becomes data delayed by six dot clock periods relative to the image data Da.  
         [0080]    Meanwhile, as described above, the phase-expanded video signals VID 1 -VID 6  change with one unit time being the time period which is determined by the product between the number of expanded phases (the number of channels into which the video signal VID is divided) and one period of the dot clock signal DCLK. In this example, one unit time becomes the six dot periods, which agree with the delay time of the delay unit Ud. In other words, the delay unit Ud generates the image data Db by delaying the image data Da for the time period which corresponds to one unit time of the phase-expanded video signals VID 1 -VID 6  (the selection time period of a certain block) obtained by the phase expansion (serial-to-parallel conversion). Here, when the image data Da is current data, the image data Db is previous data one unit time before the current data one unit time.  
         [0081]    Next, the first correction unit Uh 1  includes a first subtracter circuit  41 , a first averaging circuit  42 , a first coefficient circuit  43 , and a latch circuit  44 , and it generates first correction data Dh 1  corresponding to the first error voltage Ve 1  explained before. The first subtracter circuit  41  subtracts the image data Db (previous) from the image data Da (current), thereby generating first difference data Dx.  
         [0082]    Subsequently, the first averaging circuit  42  averages the first difference data Dx for each block, thereby generating first average data Dw 1 . The averaging circuit  42  has an adder circuit  421  and a latch circuit  422 . The latch circuit  422  latches the output signal of the adder circuit  421  on the basis of the dot clock signal DCLK. The first difference data Dx is fed to one input terminal of the adder circuit  421 , while the output data of the latch circuit  422  is fed back to the other input terminal thereof. Accordingly, the adder circuit  421  and the latch circuit  422  function as an accumulator circuit. A reset signal RS of six dot clock cycles is fed to the reset terminal R of the latch circuit  422 . Therefore, the first difference data Dx is reset and is accumulated every unit time.  
         [0083]    The first averaging circuit  42  further includes a divider circuit  423  and a latch circuit  424 . The divider circuit  423  divides data obtained by accumulating the first difference data Dx in block units by “6” (the number of expanded phases). The latch circuit  424  latches the output data of the divider circuit  423  in accordance with a block clock signal BCLK which becomes active every unit time, and it outputs the latched data as the first average data Dw 1 . Incidentally, the block clock signal BCLK is generated by the timing circuit  200  shown in FIG. 1.  
         [0084]    Subsequently, the first coefficient circuit  43  includes a multiplier unit, and first coefficient circuit  42  multiplies the first average data Dw 1  by a first coefficient K 1  and outputs the resulting product. The latch circuit  44  is used for time adjustment, and latch circuit yy latches the output data of the coefficient circuit  43  and outputs the latched data as the first correction data Dh 1 .  
         [0085]    In this manner, in the first correction unit Uh 1 , the image data Db of the directly preceding block is subtracted from the image data Da of the current block, the subtracted result is integrated in block units, the integrated result is divided by the number of expanded phases (the number of divided channels), and the divided result is multiplied by the first coefficient K 1 , whereby the first correction data Dh 1  is obtained. Accordingly, when K 1 /6=α is set, the first correction data Dh 1  agrees with the first error voltage Ve 1  explained before. Here, the first coefficient K 1  should desirably be determined on the basis of, at least, the parasitic capacitance components occurring in the respective video signal feed lines L 1 -L 6  and the resistance component of the counter electrode.  
         [0086]    Next, the second correction unit Uh 2  includes a second subtracter circuit  51 , a second averaging circuit  52 , a second coefficient circuit  53 , and a latch circuit  54 , and it generates second correction data Dh 2  corresponding to the second error voltage Ve 2  explained before.  
         [0087]    The second subtracter circuit  51  subtracts predetermined reference data Dref from the image data Da, thereby generating second difference data Dy. Here, the reference data Dref can be experimentally determined so as to minimize the block ghosting.  
         [0088]    As the reference data Dref, it is desirable to select the initial voltage Vs which was written to and held in the pixel capacitors of the pixels belonging to a certain block when the block was selected. The reason for this is that, as explained before, the second factor arises when the initial voltages Vs of the pixel capacitors change, to the voltages of the video signals VID 1 -VID 6 .  
         [0089]    Meanwhile, the liquid-crystal display panel  100  is driven by an A.C. drive method so as not to apply a D.C. voltage to the liquid crystal. Therefore, at a certain pixel, the polarity of a voltage which is applied to the liquid crystal needs to be inverted with respect to the voltage of the counter electrode as a center voltage between even-numbered fields and odd-numbered fields. An image has a high correlation between the fields, so that when black is displayed in the even-numbered field for the certain pixel, it is often displayed in the succeeding odd-numbered field. In this case, the voltage which is applied to the pixel capacitor needs to be greatly changed between the fields. Since, however, the data line  114  and the pixel capacitor are capacitive loads, the voltage of the pixel capacitor sometimes fails to be changed to a target voltage during the selection time period of the block. In this regard, a predetermined voltage is sometimes applied to the pixel capacitors beforehand in a vertical blanking period, a horizontal blanking period, or the like. This voltage is called a “precharge voltage” and is set to, for example, a gray level. In a drive method wherein the precharge voltage is applied, this precharge voltage acts as the initial voltage Vs, and it may well be employed as the reference data Dref.  
         [0090]    Subsequently, similarly to the first averaging circuit  42 , the second averaging circuit  52  includes an adder circuit  521  and a latch circuit  522  which perform accumulation every block, a divider circuit  523 , and a latch circuit  524 . The second averaging circuit  52  averages second difference data Dy for each block, thereby generating second average data Dw 2 .  
         [0091]    Further, the second coefficient circuit  53  includes a multiplier unit, and it multiplies the second average data Dw 2  by a second coefficient K 2  and outputs the resulting product. The latch circuit  54  is used for time adjustment, and it latches the output data of the second coefficient circuit  53  and outputs the latched data as the second correction data Dh 2 .  
         [0092]    In this manner, in the second correction unit Uh 2 , the reference data Dref is subtracted from the image data Da of the current block, the subtracted result is integrated in block units, the integrated result is divided by the number of expanded phases (the number of divided channels), and the divided result is multiplied by the second coefficient K 2 , whereby the second correction data Dh 2  is obtained. Accordingly, when K 2 /6=β is set, the second correction data Dh 2  agrees with the second error voltage Ve 2  described before. Here, the second coefficient K 2  should desirably be determined on the basis of, at least, the parasitic capacitance components due to the respective data lines  114   a - 114   f  and the resistance component of the counter electrode. According to the second correction unit Uh 2 , in a case, by way of example, where luminance has changed from black to a gray level midway within a certain block, the value of the second correction data Dh 2  can be adjusted in accordance with the black area occupied in the pertinent block.  
         [0093]    Next, the subtracter circuit  45  subtracts the first correction data Dh 1  and the second correction data Dh 2  from the image data Db and outputs the resulting difference as the corrected image data Dout. Since the first correction data Dh 1  and second correction data Dh 2  correspond to the respective error voltages Ve 1  and Ve 2  as explained before, the subtraction thereof from the image data Db permits the generation of the corrected image data Dout in which reverse block ghost components are contained in the image data Db. Thus, the block ghosting caused by the first and second factors can be cancelled.  
         [0094]    The reason why the image data Da before the phase expansion is subjected to correction in this embodiment is as follows. Since the signals after the phase expansion have been divided into the six channels, when deghosting circuits are disposed for the respective channels, the circuit arrangement becomes complicated. In contrast, when the image data Da is subjected to correction, the ghosting can be cancelled by the circuit for one channel. Therefore, according to this embodiment, the ghosting can be effectively cancelled by asing a simple construction.  
         [0095]    Next, the phase expansion circuit  302  will be described. FIG. 3 is a block diagram showing the main construction of the phase expansion circuit  302 . As shown in the figure, the phase expansion circuit  302  has a first sample-and-hold unit USa which includes sample-and-hold circuits SHa 1 -SHa 6 , and a sample-and-hold unit USb which includes sample-and-hold circuits SHb 1 -SHb 6 .  
         [0096]    The sample-and-hold circuits SHa 1 -SHa 6  of the first sample-and-hold unit USa sample-and-hold the video signal VID on the basis of the sample-and-hold pulses SP 1 -SP 6  fed from the timing circuit  200 , so as to generate signals vid 1 -vid 6 , respectively. Here, one period of all the sample-and-hold pulses SP 1 -SP 6  is six times larger than the period of the dot clock signal DCLK, and the phases of the adjacent ones of these pulses are shifted by one period of the dot clock signal DCLK. Accordingly, the time axis of all the signals vid 1 -vid 6  is extended by a factor of six relative to that of the video signal VID, and the phases of the signals vid 1 -vid 6  are successively shifted by a dot clock signal period.  
         [0097]    Next, the sample-and-hold circuits SHb 1 -SHb 6  of the second sample-and-hold unit USb sample-and-hold the signals vid 1 -vid 6  on the basis of the sample-and-hold pulse SS fed from the timing circuit  200 , so as to output the resulting signals as the phase-expanded video signals VID 1 -VID 6  through corresponding buffer circuits (not shown). The sample-and-hold pulse SS has a period of one unit time. Accordingly, the signals vid 1 -vid 6  are phased at a timing at which the sample-and-hold pulse SS becomes active, so that in-phase phase-expanded video signals VID 1 -VID 6  are generated.  
         [0098]    Now, the operation of the liquid-crystal display device will be described. First, the operation from after the input of the image data Da until the corrected image data Dout is generated by the deghosting circuit  304  will be explained. FIG. 4 is a timing chart for explaining the operation of the deghosting circuit  304 . In this figure, suffix X in symbol DX,Y denotes the number of the data lines  114  within one block in the scanning direction of the block, while suffix Y denotes the number of blocks. By way of example, data D 1 ,n+1 corresponds to the first data line  114   a  in a block, and the pertinent block is the (n+1)-th block.  
         [0099]    The operation of the first correction unit Uh 1  will be explained. When the image data Da is fed to the deghosting circuit  304 , the delay unit Ud delays the image data Da by one unit time (six dot clock cycles) and outputs the delayed data as the image data Db.  
         [0100]    Thus, the image data Db which precedes the image data Da by one unit time is obtained. By way of example, for a time period Tx indicated in FIG. 4, the image data Da is data D 2 ,n, which corresponds to the data line  114   b  of the block Bn. On the other hand, the image data Db is data D 2 ,n−1, which corresponds to the data line  114   b  of the block Bn−1. The data line  114   b  of each of the blocks is fed with the video signal VID 2  through the video signal feed line L 2 . That is, both the image data Da and the image data Db in the pertinent time period Tx correspond to the video signal VID 2  which is fed through the video signal feed line L 2 . Moreover, since the image data Da and the image data Db correspond to adjacent blocks, they are data before and after the signal level of the video signal VID 2  is changed over.  
         [0101]    When the image data Da and Db are fed to the first subtracter circuit  41 , this circuit  41  subtracts the image data Db (previous: one block before) from the image data Da (current), thereby generating the first difference data Dx. By way of example, in the time period Tx indicated in the figure, the image data Da and the image data Db are the data “D 2 ,n” and “D 2 ,n−1”, respectively, and hence, the first difference data Dx becomes data “D 2 ,n−D 2 ,n−1”.  
         [0102]    As shown in FIG. 14, the video signal feed lines L 1 -L 6  are capacitively coupled. Therefore, when the video signal VID which is applied to any of the video signal feed lines L 1 -L 6  changes, the first error voltage Ve 1  is induced in the counter electrode, and the whole pertinent block is affected. Since the whole block is affected by the change of the video signal fed to a certain video signal feed line, the first averaging circuit  42  is used in order to reflect this change in the other video signals.  
         [0103]    Since the first difference data Dx are accumulated by the adder circuit  421  and the latch circuit  422  included in the first averaging circuit  42 , the output data of the latch circuit  422  corresponding to the last timing within each block becomes the sum of the first difference data Dx accumulated in the pertinent block. By way of example, in a time period from a time t 10  to a time t 12  indicated in FIG. 4, the output data of the latch circuit  422  becomes Dx 1 ,n+Dx 2 ,n+ +Dx 6 ,n.  
         [0104]    The output data of the latch circuit  422  is divided by the divider circuit  423 , and the latch circuit  424  latches the divided result on the basis of the block clock signal BCLK. Therefore, the latch circuit  424  generates the first average data Dw 1  before the output data of the latch circuit  422  is reset. In the illustrated example, when the block clock signal BCLK rises from a low level to a high level at a time t 11 , the latch circuit  424  generates the first average data Dw 1  in synchronization with the rising edge of the signal BCLK. Thereafter, when the time t 12  is reached, the reset signal RS becomes active (high level), and hence, the latch circuit  422  has its output data reset to prepare for the accumulation of the first difference data Dx of the next block.  
         [0105]    Further, when the first average data Dw 1  is fed to the coefficient circuit  43 , it is multiplied by the first coefficient K 1 . The resulting data, however, is out of phase with the image data Db. Therefore, the latch circuit  44  latches the output data of the coefficient circuit  43  in accordance with the dot clock signal DCLK so as to output the first correction data Dh 1  in-phase with the image data Db.  
         [0106]    Next, the operation of the second correction unit Uh 2  will be explained. FIG. 5 is a timing chart showing the operation of the second correction unit Uh 2 . When the second subtracter circuit  51  is fed with the image data Da, it subtracts the reference data Dref from the image data Da (current), thereby generating the second difference data Dy. By way of example, in the time period Tx indicated in the figure, the second difference data Dy becomes data “D 2 ,n−Dref”.  
         [0107]    As shown in FIG. 14, the equivalent capacitances constituted by the parasitic capacitances of the data lines  114   a - 114   f  and the capacitances of the pixel capacitors are capacitively coupled. Therefore, when a voltage which is applied to any of the equivalent capacitances changes, the error voltage Ve 2  corresponding to the magnitude of the change is induced in the counter electrode, and the whole pertinent block is affected. Since the whole block is affected by the voltage change of a certain one of the data lines  114   a - 114   f , the second averaging circuit  52  is used in order to reflect this change in the video signals in advance.  
         [0108]    In a similar manner to that of the first averaging circuit  42  averaging the first difference data Dx, the second averaging circuit  52  averages the second difference data Dy every block, thereby generating the second average data Dw 2 . When the second average data Dw 2  is fed to the coefficient circuit  53 , it is multiplied by the second coefficient K 2 . The resulting data, however, is out of phase with the image data Db, as illustrated in the figure. Therefore, the latch circuit  54  latches the output data of the coefficient circuit  53  in accordance with the dot clock signal DCLK so as to output the second correction data Dh 2  in-phase with the image data Db.  
         [0109]    Further, the first and second correction data Dh 1  and Dh 2  are subtracted from the image data Db, whereby the corrected image data Dout is generated. The corrected image data Dout is converted into an analog signal through the D/A converter  301 , and the analog signal is fed to the phase expansion circuit  302  as the video signal VID.  
         [0110]    Next, the operation in which the phase-expanded video signals VID 1 -VID 6  are generated on the basis of the video signal VID will be explained. FIG. 6 is a timing chart showing the operation of the phase expansion circuit  302 .  
         [0111]    When the video signal VID is fed to the phase expansion circuit  302 , the sample-and-hold circuits SHa 1 -SHa 6  extend the time axis of the video signal VID by a factor of six and divide the extended video signal into six channels in synchronization with the corresponding sample-and-hold pulses SP 1 -SP 6 , thereby generating the respective signals vid 1 -vid 6  shown in the figure. Further, the sample-and-hold circuits SHa 1 -SHa 6  sample-and-hold the signals vid 1 -vid 6  in synchronization with the sample-and-hold pulse SS, thereby generating the video signals VID 1 -VID 6 , respectively.  
         [0112]    Here, the operation in which the ghost is cancelled will be concretely explained. FIG. 7 is a timing chart of the phase-expanded video signals VID 1 -VID 6  in the case of phase-expanding the video signal VID by feeding the image data Da to the D/A converter  301  without employing the deghosting circuit  304 , and the corrected image data Dout generated by employing the deghosting circuit  304 . In FIG. 7, in order to facilitate understanding, data values are expressed in terms of the levels of the analog signals, and delay times due to the phase expansion are ignored. In this example, it is assumed that the same display as in FIG. 13A is presented and that the initial voltage Vs is the gray level Vc.  
         [0113]    As shown in FIG. 7, the image data Da takes the data value corresponding to the black level Vb for the time period t 0 -t 10 , and it takes the data value corresponding to the gray level Vc for the time period t 10 -t 18 . Therefore, the phase-expanded video signals VID 1 -VID 4  shift from the level Vb to the level Vc at the time t 12  at which the selection time period of the block B 4  changes over to that of the block B 5 . On the other hand, the phase-expanded video signals VID 5  and VID 6  shift from the level Vb to the level Vc at the time t 6  at which the selection time period of the block B 3  changes over to that of the block B 4 .  
         [0114]    A voltage Vcom 1  which is induced in the counter electrode due to the first factor appears in accordance with the change of each of the phase-expanded video signals VID 1 -VID 6 . Accordingly, the waveform of the induced voltage Vcom 1  becomes a differential waveform at the time t 6  and the time t 12 , as shown in the figure.  
         [0115]    Besides, a voltage Vcom 2  which is induced in the counter electrode due to the second factor appears in accordance with the change of each of the phase-expanded video signals VID 1 -VID 6 . Accordingly, the waveform of the induced voltage Vcom 2  becomes a differential waveform at the time t 6  and the time t 12 , as shown in the figure. The polarity of the induced voltage Vcom 2 , however, becomes opposite to that of the induced voltage Vcom 1 .  
         [0116]    A voltage Vcom which is actually induced in the counter electrode is given by the total of the induced voltages Vcom 1  and Vcom 2 , and the value of the voltage Vcom at the time at which the selection time period of each block ends becomes the error voltage Ve. Accordingly, the absolute value of the error voltage Ve of the block B 4  becomes 4β(Vb−Vc)−2α(Vb−Vc), while the absolute value of the error voltage Ve of the block B 5  becomes 4α(Vb−Vc).  
         [0117]    In the deghosting circuit  304  according to this embodiment, as explained before, the first correction data Dh 1  based on the first factor is generated by the first correction unit Uh 1 , while the second correction data Dh 2  based on the second factor is generated by the second correction unit Uh 2 . The first and second correction data Dh 1  and Dh 2  correspond to the error voltages Ve 1  and Ve 2 , respectively.  
         [0118]    Here, letting signs Vea, Veb, and Vec denote the differences between the counter electrode voltage Vcom and its center voltage at the times t 6 , t 12 , and t 18 , the corrected image data Dout obtained by the deghosting circuit  304  becomes as shown in FIG. 7. Also in this case, a voltage is induced in the counter electrode in accordance with the change of each of the phase-expanded video signals VID 1 -VID 6  or the proportion of the black level in a certain block. Since, however, the corrected image data Dout has been corrected in consideration of the differences Vea, Veb, and Vec shown in FIG. 7, the induced voltage of the counter electrode can be cancelled. Accordingly, even in the case where the black level changes to a gray level within a block, it is permitted to cancel the block ghosting which appears in the pertinent block and in the following block, and to strongly enhance the quality of the displayed image.  
         [0119]    Next, modifications to the foregoing embodiments will be described.  
         [0120]    In the foregoing embodiment, the D/A converter  301  is interposed between the deghosting circuit  304  and the phase expansion circuit  302 . It is to be understood, however, that it is possible to construct either of the phase expansion circuit  302  and the amplifier/inverter circuit  303  out of a digital circuit, and to dispose the D/A converter  301  on the output side of the digital circuit without departing from the spirit and scope of the present invention.  
         [0121]    In the foregoing embodiment, the phase expansion circuit  302  includes the first sample-and-hold unit USa and the second sample-and-hold unit USb shown in FIG. 3, and the signals vid 1 -vid 6  are phased by the second sample-and-hold unit USb. It is also to be understood, however, that it is possible to omit the second sample-and-hold unit USb. In this case, the signals vid 1 -vid 6  whose phases shift every dot clock cycle may be outputted as the phase-expanded video signals VID 1 -VID 6 .  
         [0122]    Next, examples in which the liquid-crystal display devices explained in the foregoing embodiments are applied to electronic equipment will be described.  
         [0123]    A projector which employs the liquid-crystal display device as a light valve will be explained first. FIG. 8 is a plan view showing an example construction of the projector. As shown in the figure, a lamp unit  1102  including a white light source, such as halogen lamp, is disposed inside the projector  1100 . Projection light emerging from the lamp unit  1102  is separated into three primary colors R, G and B by four mirrors  1106  and two dichroic mirrors  1108  which are arranged in a light guide  1104 . The lights of the three primary colors enter liquid-crystal panels  1110 R,  1110 B and  1110 G which act as light valves for the respective primary colors.  
         [0124]    Each of the liquid-crystal panels  1110 R,  1110 B and  1110 G has the same construction as that of the foregoing liquid-crystal display panel  100 , and these liquid-crystal panels are respectively driven by primary color signals R, B and G which are supplied by video signal processing circuits (not shown). Further, the light modulated by these liquid-crystal panels enters a dichroic prism  1112  in three directions. In the dichroic prism  1112 , the light of the colors R and B is refracted at 90 degrees, whereas the light of the color G is transmitted straight through. The images of the respective colors are accordingly combined, with the result that a color image is projected on a screen or the like through a projection lens  1114 .  
         [0125]    Incidentally, the light corresponding to the respective primary colors R, G and B enters the liquid-crystal panels  1110 R,  1110 B and  1110 G owing to the dichroic mirrors  1108 , so that color filters need not be disposed on the counter substrates.  
         [0126]    As explained before, the deghosting circuit  304  or  305  is included in an image processing circuit  300  of the liquid-crystal display device. It is therefore possible to cancel the first or second ghost component and to strongly enhance the quality of the displayed image.  
         [0127]    Next, an example in which the liquid-crystal display device is applied to a portable computer will be explained. FIG. 9 is a front view showing the construction of the computer. Referring to the figure, the computer  1200  is constructed of a body  1204  including a keyboard  1202 , and a liquid-crystal display  1206  including a liquid-crystal panel  1005 . The liquid-crystal display  1206  is constructed by attaching a back light onto the rear surface of the liquid-crystal panel  100  described above.  
         [0128]    Further, an example in which the liquid-crystal display device is applied to a mobile telephone will be explained. FIG. 10 is a perspective view showing the construction of the mobile telephone. Referring to the figure, the mobile telephone  1300  includes a reflection-type liquid-crystal panel  1005  together with a plurality of operating buttons  1302 . The reflection-type liquid-crystal panel  1005  is furnished with a front light on its front surface, as required.  
         [0129]    Apart from the electronic equipment described with reference to FIGS.  8 - 10 , the present invention can also be used in a liquid-crystal television set, a viewfinder-type or monitor direct-view-type video tape recorder, car navigation equipment, a pager, an electronic notebook, a pocket or desk calculator, a word processor, a workstation, a video telephone, a POS terminal, equipment including a touch panel, and the like.  
         [0130]    As thus far described, according to the present invention, in a case where video signals generated by dividing an input video signal into a plurality of channels and extending the time axis thereof, so as to maintain a predetermined signal level every unit time, are fed to corresponding data lines at a predetermined timing, ghosting which appears in a display image is predicted even when a luminance level changes midway in a block, and image data is corrected so as to cancel the ghosting, so that the quality of the display image can be strongly enhanced.  
         [0131]    While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, preferred embodiments of the invention as set forth herein are intended to be illustrative not limiting. Various changes may be made without departing from the spirit and scope of the invention.

Technology Classification (CPC): 6