JP2004220022A - Method of driving display device, display device, its program, recording medium with the program recorded thereon and computer program products including recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which has an excellent display quality in a relatively small circuit scale. <P>SOLUTION: A frame memory 31 stores an image data before correction of the present and previous frames until the next frame. Whereas, a previous frame gradation correcting circuit 34 reads the image data before correction of one before previous and previous frames from the frame memory 31 and corrects the image data of the previous frame so as to approximate the image data of the one before previous frame. Further, a modulation processing part 33 refers to the image data of the previous frame after correction and corrects the image data of the present frame so as to emphasize the gradation transition from the previous frame to the present frame. In the constitution, when the gradation transition from the one before previous frame to the present frame is decay to rise although an error due to the correction is not superimposed, the degree of the emphasis of the gradation transition is suppressed, and the occurrence of white luster is suppressed even when the response speed of a pixel is slow. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a display device driving method, a display device, a program thereof, a recording medium on which the program is recorded, and a computer program product including the recording medium.

  2. Description of the Related Art Liquid crystal display devices that can be driven with relatively little power are widely used as display devices for stationary devices as well as portable devices. The liquid crystal display device has a slow response speed as compared with a CRT (Cathode-Ray Tube) or the like, and does not complete a response in a rewrite time (16.7 msec) corresponding to a normal frame frequency (60 Hz) due to a transition gray scale. For this reason, a method of driving by modulating a driving signal so as to emphasize the gradation transition from the previous time to the current time is also adopted (see Patent Document 1 described later).

  For example, when the gradation transition from the previous frame FR (k-1) to the current frame FR (k) is rise driving, specifically, the current frame FR (k-1) is emphasized so as to emphasize the gradation transition from the previous frame to the current frame. A voltage higher than the voltage level indicated by the video data D (i, j, k) of (k) is applied to the pixel.

  As a result, when the gray level changes, the luminance level of the pixel is compared with the luminance level when the voltage level indicated by the video data D (i, j, k) of the current frame FR (k) is applied from the beginning. , Increases more steeply, and reaches a luminance level near the video data D (i, j, k) of the current frame FR (k) in a shorter period of time. Thus, the response speed of the liquid crystal display device can be improved even when the response speed of the liquid crystal is low.

  However, even if the response speed of the liquid crystal is not sufficient and the gradation transition is emphasized, the target frame cannot reach the target luminance level due to the gradation transition from the previous time to the current one. If the gradation transition is emphasized on the assumption that the gradation transition has been sufficiently performed from the previous two times to the previous time, the gradation transition may not be appropriately emphasized.

  Therefore, in Patent Document 2 described below, a transmittance curve is created or predicted from at least continuous three-field signal data applied to an arbitrary pixel, and the transmittance curve deviates from a desired transmittance curve by a predetermined value or more. Discloses a display device for correcting the signal data of the continuous fields.

Specifically, as shown in FIG. 11, in the display device 101, the data input unit 111 causes the field memory 112 to store video data for each pixel. Further, the data correction unit 113 corrects the video data in the field memory 112 with reference to the field memory 112 when the difference between the ideal transmittance and the predicted actual transmittance is larger than a predetermined threshold. . Further, the data output unit 114 sequentially reads the corrected video data from the field memory 112 and drives a pixel (not shown).
JP-A-2002-116743 (publication date: April 19, 2002) Japanese Patent No. 2650479 (Date of issue: September 3, 1997)

  However, in the above-described conventional configuration, the corrected video data is stored in the memory, and when driving the pixel next time, the necessity of the correction and the correction are performed with reference to the video data. When a deviation occurs between the transmittance and the actual transmittance, correction errors due to the deviation are sequentially superimposed and accumulated. As a result, it is necessary to sufficiently increase the accuracy in estimating the transmittance, which causes a problem that it is difficult to simplify the circuit.

  The present invention has been made in view of the above problems, and has as its object to realize a display device with a relatively small circuit scale and good display quality.

  In order to solve the above-described problem, a display device driving method according to the present invention includes a first driving signal (for example, video data of a previous frame) input at a first time, and a first driving signal input from a first time. A determining step of determining a value corresponding to a previous drive signal (for example, video data of a frame before the previous frame) input at a previous time point, and a second step following the first time point from the first time point. The second drive signal (eg, video data of the current frame) input at the second time is modulated based on the determined value so as to emphasize the gradation transition to the time, and And a modulation step of generating a corrected second drive signal for supplying the second drive signal to the second drive signal.

  In the case where video data of one or a plurality of frames is formed from the first and second drive signals before the above, the modulating step includes performing the correction for obtaining the corrected second video signal. Based on the first drive signal, the grayscale transition of the pixel from the previous frame indicated by the first drive signal to the current frame indicated by the second drive signal is emphasized. The method may include a step of correcting video data indicated by the second drive signal.

  In the above configuration, in the modulation step, when the second drive signal is modulated so as to emphasize the gradation transition from the first time point (previous time) to the second time point (current time), it is determined in the above determination step. Since the modulation is performed based on the determined value, the amount of correction can be suppressed when the gradation transition from the last two times to the previous time is a predetermined gradation transition, as compared with the case where there is no correction (modulation) in the determination step.

  As a result, for example, when the gradation transition from the last two times to the current time is performed in the modulation process as in the case of decay → rise or rise → decay, the following phenomenon occurs: Due to the synergistic effect of the lack of response of the pixel in the transition from the previous to the previous gradation and the enhancement of the gradation transition in the modulation step, the gradation of the current pixel greatly differs from the gradation indicated by the second drive signal, Even in the case where a phenomenon such as blackening or black sun phenomenon occurs, by suppressing the amount of correction in the modulation step, the occurrence of the phenomenon can be suppressed, and the display quality of the display device can be improved.

  On the other hand, in the determination step, the determined value is determined based on the previous and first drive signals (data before correction), and in the modulation step, the second value is determined based on the determined value. Since the drive signal (data before correction) is modulated, the above steps can be performed by storing the data (drive signal) before correction. Therefore, unlike a configuration in which the corrected drive signal is stored, errors due to the correction in the modulation process are not superimposed and accumulated. Therefore, even if each of the above steps is performed by a circuit having a relatively small circuit scale and a low calculation accuracy for correction, the gradation control of the pixel does not diverge or vibrate. As a result, a display device with good display quality can be realized with a relatively small circuit scale.

  Note that the determined value may always be the corrected first drive signal, but if the necessity of correction changes depending on conditions such as an input drive signal, the corrected first drive signal may be used. It may be one of the first drive signal and the first drive signal that is not corrected. Further, in addition to the above-described configuration, when including a step of storing the previous video data related to the first drive signal together with the video data two times before related to the previous drive signal, in the determining step, The value corresponding to the previous drive signal may be determined based on the stored video data before and after the last time. Further, in addition to the above configuration, the determined value is one of a corrected first drive signal and an uncorrected first drive signal, and the determining step includes a predetermined two-time and a previous image. The determined value may be generated according to a combination of data. In this case, in addition to the configuration, in the case of the predetermined combination, the determining step is indicated by the first drive signal in order to obtain the corrected first drive signal. The method may further include the step of correcting the previous video data and the step of outputting the first drive signal without correction when the combination of the video data before and after the previous video data is not a predetermined combination. Good.

  On the other hand, in addition to the above configuration, video data of one or a plurality of frames is configured from the first and second drive signals before the above, and the determining step is performed in a previous time indicated by the first drive signal. In order to correct the video data, the grayscale level reached by the pixel due to the grayscale transition from the video data two times before indicated by the previous drive signal to the previous video data indicated by the first drive signal is calculated. A prediction step may be included. In this configuration, since the previous video data can be corrected to the predicted gradation level and set to the determined value, it is possible to suppress the occurrence of white light and black sun and improve the display quality.

  Furthermore, in addition to the above configuration, the predetermined combination corresponds to a correction amount to be given to the corrected first drive signal, and the determining step includes determining at least one of a type of image and a temperature. An adjustment step of changing the correction amount based on the correction amount may be included.

  In this configuration, the correction amount is changed based on at least one of the image type and the temperature. Therefore, the determined value can be changed according to the image type and the temperature, and the display quality can be further improved.

  Further, in addition to the above configuration, when at least one of the type and the temperature of the image satisfies a predetermined threshold condition, the execution of the adjustment step may be stopped.

  Here, in the case where the gradation transition from the last two times to the current time is decay → rise or rise → decay, the degree of emphasizing the gradation transition from the previous time to the current time in the modulation step is reduced in the determination step. If the previous video data is corrected to the video data of the previous two times, the following may occur. That is, as in the case where the temperature of the pixel is high or the type of image is a slow-moving image, at least one of the image type and the temperature satisfies the predetermined conditions, and the previous image data need not be corrected. However, when the previous video data is corrected, the response speed may be undesirably reduced, even though it is expected that no white light or black sun will occur.

  On the other hand, in the above configuration, when at least one of the image type and the temperature satisfies the predetermined condition, the correction in the determining step is stopped. Therefore, it is possible to prevent a decrease in response speed in a case where it is expected that no whitening or blackening will occur. If the above condition is not satisfied, the previous video data is corrected, so that it is possible to prevent the occurrence of white light and black sun without any trouble.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, the previous drive signal includes the video data of the previous time, and the determining step includes the gray level of the previous time. When the gradation level determined on the basis of the previous and the previous image data falls from the gradation level of the previous two times at the time of the gradation transition from the previous to the previous gradation level, the pixel is caused by the gradation transition. The method may include a step of correcting the previous video data so as to indicate a higher gray level than the predicted gray level.

  Here, in the above-mentioned first determining step, the previous video data may be corrected so that the gray level transition from the last two times to the previous time becomes the gray level predicted to reach the pixel by the gray level transition. However, in this case, if the reached gradation cannot be predicted with sufficient accuracy, there is a possibility that a whitening or blackening may occur due to a difference between the predicted value and the actual gradation.

  On the other hand, in the above configuration, in the case where the gray level transition from the previous two times to the previous level is a gray level transition that lowers the gray level, the previous video data is displayed so as to indicate a gray level larger than the predicted attained gray level. Since the correction is made, even if a deviation occurs between the predicted value and the actual gradation, it is possible to prevent the occurrence of white light. As described above, by preventing the occurrence of white light which tends to cause a decrease in display quality between white light and black sun, even if a deviation occurs between the predicted value and the actual gradation, the display quality can be reduced. Can be suppressed.

  By the way, the video data stored for performing each of the above steps may have the same bit width as the current video data. However, when a reduction in circuit scale is particularly required, in addition to the above configuration, The two-time video data and the previous video data have a predetermined combination of bit widths, and the bit width is twice as large as the bit width of the current video data for the second drive signal. Is also set to be small, the bit width of the video data of the last two times before is set to be the same as or narrower than the bit width of the previous video data, and in the storing step, in the storing step, the video data of the last two times of the video data and the previous video data are set. The video data before and after the previous video data may be stored with a limited bit width so that the bit width becomes the predetermined value. In this configuration, since the bit width for storing both video data is more limited than when both video data are stored as they are, the circuit scale can be reduced as compared with the case where all video data are stored.

  On the other hand, a computer program product according to the present invention is a computer program product including a recording medium on which a computer program for driving a display device to a processor that processes the computer program product is recorded. Determining a first drive signal input at a first time point and a value according to a previous drive signal input at a time point earlier than the first time point; A second time point input at the second time point based on the determined value so as to emphasize a gradation transition from the first time point to a second time point subsequent to the first time point. Modulating the drive signal to generate a corrected second drive signal to supply the modulated drive signal to the pixel. It is characterized in that it is a lamb. A program according to the present invention is a program that causes a computer to execute the above-described steps. Further, the above-mentioned program is recorded on a recording medium according to the present invention.

  When the program is executed by a computer or a processor, the computer or the processor executes the above-described steps. Therefore, similarly to the above-described method of driving the display device, a display device with high display quality can be realized with a relatively small circuit scale.

  Further, in order to solve the above problem, the display device according to the present invention includes a first drive signal input at a first time point and a drive signal before input at a time point before the first time point. Determining means for determining a value in accordance with the above, and for emphasizing a gradation transition from the first time point to a second time point subsequent to the first time point, based on a determination result from the determining means. And a modulating means for modulating the second drive signal input at the second time point to generate a corrected second drive signal for supply to the pixels.

  The determining means of the display device can execute the above-described determining step, and the modulating means of the display device can execute the above-described modulating step. Therefore, similarly to the above-described method of driving the display device, a display device with high display quality can be realized with a relatively small circuit scale.

  Further, in addition to the above configuration, the determined value may be one of a corrected first drive signal and an uncorrected first drive signal.

  Further, in addition to the above-described configuration, the image processing apparatus further includes a storage unit that stores the previous video data related to the first drive signal together with the video data two times before that related to the previous drive signal. A value corresponding to the previous drive signal may be determined based on the performed two-time and previous video data.

  Further, in addition to the above configuration, video data of one or a plurality of frames is configured from the first and second drive signals before the above, and the determining unit determines the last time represented by the first drive signal. In order to correct the video data, the grayscale level reached by the pixel due to the grayscale transition from the video data two times before indicated by the previous drive signal to the previous video data indicated by the first drive signal is calculated. It may be predicted.

  Further, in addition to the above configuration, the modulating means may further include, based on the corrected first drive signal for obtaining the corrected second video signal, a signal of the first drive signal of the pixel. The video data indicated by the second drive signal may be corrected so as to emphasize the gradation transition from the previous frame to the current frame indicated by the second drive signal.

  Further, in addition to the above-described configuration, the determined value is one of a corrected first drive signal and an uncorrected first drive signal, and the determining unit performs a predetermined two-time and a previous image. The determined value may be generated according to a combination of data.

  In addition, in addition to the above configuration, in the case of the predetermined combination, the determining unit may obtain the corrected first drive signal by using the previous image indicated by the first drive signal. The data may be corrected, and if not, the first drive signal may be output without correction.

  Further, in addition to the above configuration, the predetermined combination corresponds to a correction amount to be given to the corrected first drive signal, and the determining unit determines at least one of a type of image and a temperature. Based on this, the correction amount may be changed.

  Further, in addition to the above configuration, the determining unit may stop changing the correction amount when at least one of the type and the temperature of the image satisfies a predetermined threshold condition.

  Further, in addition to the above-described configuration, the last two-time video data and the previous video data have a predetermined combination of bit widths, and the bit width is the current video data for the second drive signal. The bit width of the video data is set to be smaller than twice the bit width of the data, the bit width of the video data before the last is set to be the same as or narrower than the bit width of the previous video data, and the storage means is stored in the storage means. The video data and the previous video data may be stored with a bit width limited so that their bit widths become the predetermined value.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, the previous drive signal includes the video data before the previous video, and the determining unit determines that the video data before the previous video and the video video of the previous video are included. If the gradation level determined based on the data drops from the previous two-time gradation level at the time of the gradation transition from the previous two-time gradation level to the previous gradation level, the pixel is caused by the gradation transition. The previous video data may be corrected so as to indicate a gray level higher than the predicted gray level.

  Since each of these display devices can execute the corresponding display device driving method, a display device with a relatively small circuit scale and high display quality can be realized similarly to the above-described display device driving method.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, the previous drive signal includes the video data before the previous video, and the determining unit performs the video data before the previous video and the video before the previous video. A look-up table in which the gradation of the previous video data after correction is stored corresponding to each combination of data is provided, and the bit width of the gradation of the previous video data described in the lookup table is provided. , May be set to the shorter one of the bit widths of the gradation of the video data before and after the previous video data.

  In this configuration, the bit width of the previous video data described in the look-up table is set to the same bit width as the significant digit of the operation using the video data before and after the previous video data, that is, the shorter bit width. I have. Therefore, the storage capacity required for the look-up table can be reduced to the greatest extent that the calculation accuracy is not reduced.

  In addition to the above configuration, the look-up table stores the gradation of the previous video data after correction of a predetermined combination among the combinations of the video data before and after the previous video, and The determining means interpolates the gradation of the previous video data after correction stored in the look-up table to calculate the gradation of the previous video data after correction corresponding to the combination of the last two times and the previous video data. May be provided.

  According to this configuration, since the control means calculates the gradation of the previous video data after correction by interpolation, the gradation of the previous video data after correction corresponding to all combinations is stored in the lookup table. The amount of data to be stored in the look-up table can be reduced as compared with the configuration in which the data is stored. Therefore, with a simpler circuit configuration than a configuration in which all are stored, it is possible to suppress the occurrence of whitening and blackening while suppressing a decrease in display quality due to a correction error of the determination unit.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, the previous drive signal includes the video data before the previous video, and the determining unit performs the video data before the previous video and the video before the previous video. Among the combinations of data, the gradation of the previous video data after correction is stored for a predetermined combination, and the gradation itself to which the previous video data should reach for other combinations is stored. A stored lookup table may be provided.

  In this configuration, when the combination is other than the predetermined combination, the look-up table stores the gradation itself to which the previous video data should reach. Therefore, by correcting the previous video data with reference to the look-up table, the correction of the previous video data can be stopped in cases other than the predetermined combination. As a result, with a simpler circuit configuration than when a table for separately determining whether or not the combination is provided is provided, while suppressing a decrease in display quality due to an error in the correction of the determination means, it is possible to reduce the occurrence of whitening or blackening. Generation can be suppressed.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, the previous drive signal includes the video data two times before, and the determination unit determines the predetermined temperature. A look-up table provided for each range, in which the gradation of the previous video data after correction is stored corresponding to each combination of the video data two times before and the previous video, and Control means for selecting a look-up table to be used for data correction, and the control means may switch the selected look-up table in accordance with the temperature.

  In this configuration, the control unit switches the look-up table used for the correction of the previous video data according to the temperature. For this reason, regardless of the temperature, it is possible to accurately suppress the occurrence of white light and black sun, and to maintain the display quality of the display device at a high level. Further, since a lookup table is provided for each temperature range, even when the change in the correction process due to the temperature cannot be described by a simple mathematical expression, the correction process can be changed by a simple circuit.

  Further, in addition to the above configuration, the control means may switch the selected lookup table according to the type of the video data. Here, when the gradation value of the previous video data after the correction is different from the gradation value to be reached by the previous video data, an appropriate value of the difference between the two differs depending on the type of video. In the above configuration, the control unit switches the look-up table used for the previous correction of the video data according to the type of the video data. Accordingly, even if any type of video such as a fast-moving video and a slow-moving video is input, it is possible to suppress the occurrence of white glow within a range where the reduction in response speed is not conspicuous.

  Further, in addition to the above configuration, the total of the bit widths of the video data of the previous and the previous two times stored in the storage unit is limited to a predetermined bit width, and the control unit stores the total in the storage unit. The bit width of the previous video data and the bit width of the video data two times before may be changed according to the pixel temperature.

  Here, when the pixel is a liquid crystal element, the response speed of the pixel changes according to the temperature. Further, the gradation reached by the pixel due to the transition of the gradation from the previous two times to the previous time becomes more susceptible to the image data of the previous two times as the response speed of the pixel becomes slower. For this reason, the optimal allocation of the bit widths of the video data before and after the previous video data stored in the storage means also changes.

  According to the above configuration, the allocation of each bit width can be maintained in an appropriate state regardless of the temperature change. For this reason, the previous video data can be corrected with higher precision, and the occurrence of white light and black sun can be suppressed more accurately.

  Further, in addition to the above configuration, the first drive signal includes the previous video data, and the previous drive signal includes the video data of the last time and the video data of the last and the last time stored in the storage unit. The total bit width of the video data is limited to a predetermined bit width, and the bit width of the previous video data stored in the storage means and the bit width of the video data two times before are stored in the storage means. It may be changed according to the type.

  Here, the gradation reached by the pixel due to the transition of the gradation from the previous two times to the previous time is more likely to be affected by the video data of the second previous time when a fast moving image is input. Therefore, when the type of video changes and the expected speed of movement changes, the optimal allocation of the bit width of the video data before and after the previous video data stored in the storage means also changes.

  According to the above configuration, the assignment of the bit width of the video data before and after the video data stored in the storage unit is changed according to the type of the video. Therefore, regardless of the type of video, the allocation of each bit width can be maintained in an appropriate state. Therefore, the previous video data can be corrected with higher accuracy, and the occurrence of white light and black sun can be suppressed more accurately.

  In addition to the above configuration, the current video data included in the second drive signal has an 8-bit width for each of the three primary colors. Of the previous and previous video data, the bit width of at least the previous video data may be limited and stored such that the total of the bit width of the previous video data and the bit width of the previous video data is 10 bits.

In this configuration, since the total bit width of the video data of the three primary colors is 30 (3 × 10) bits, when a general-purpose memory (a memory in which the data bit width is set to 2 ⁿ ) is used, the previous video is used. The storage means can be realized by a memory having the same storage capacity as when data (for three primary colors) is stored as it is.

  Further, in addition to the above configuration, the pixel may be a liquid crystal element of a normally black mode and a vertical alignment mode. Here, when the liquid crystal element of the normally black mode and the vertical alignment mode is used as a pixel, the response speed to the gradation transition of the decay is slower than the case of the rise, and the modulation is performed so as to emphasize the gradation transition. Even in the case of the decay gradation transition from the last two times to the previous time, a difference easily occurs between the actual gradation transition and the desired gradation transition. Therefore, when a gradation transition from decay to rise occurs, white light is generated, and the user can easily recognize the white light. On the other hand, in the above-described configuration, the occurrence of white light is suppressed by the second correction unit. Therefore, the generation of white light can be suppressed, and the display quality of the display device can be improved even though the liquid crystal element in the normally black mode and the vertical alignment mode is used as a pixel.

  According to the present invention, the present video data is corrected so as to emphasize the gradation transition from the previous time to the current time, and is supplied to the pixels. Since the correction can be made so as to approach the video data, a display device with good display quality can be realized with a relatively small circuit scale. Therefore, it can be suitably used for various display devices such as a liquid crystal display device such as a liquid crystal television broadcast receiver and a liquid crystal monitor.

[First Embodiment]
One embodiment of the present invention will be described below with reference to FIGS. That is, the image display device (display device) 1 according to the present embodiment emphasizes the gradation transition from the previous time to the current time, thereby improving the response speed of the pixel, but in spite of improving the gradation transition. Due to the synergistic effect of the lack of response of the pixel in the transition from the previous to the previous gradation, the gradation of the current pixel is significantly different from the gradation indicated by the current video data, causing the phenomenon that white flash or black sun phenomenon occurs. The image display device 1 can be prevented with a relatively small circuit scale.

  As shown in FIG. 2, the panel 11 of the image display device 1 includes a pixel array 2 having pixels PIX (1,1) to PIX (n, m) arranged in a matrix, and a data signal of the pixel array 2. A data signal line driving circuit 3 for driving the lines SL1 to SLn and a scanning signal line driving circuit 4 for driving the scanning signal lines GL1 to GLm of the pixel array 2 are provided. Further, the image display device 1 includes a control circuit 12 for supplying a control signal to both drive circuits 3 and 4 and a control circuit 12 for enhancing the gradation transition based on an input video signal. And a modulation drive processing section 21 for modulating a given video signal. Note that these circuits operate by power supply from the power supply circuit 13.

  Hereinafter, before describing the detailed configuration of the modulation drive processing unit 21, the schematic configuration and operation of the entire image display device 1 will be described. For convenience of description, for example, only when it is necessary to specify the position, such as the i-th data signal line SLi, a reference is given with a numeral or alphabetic character indicating the position, and there is no need to specify the position. In cases or collective terms, reference is made by omitting characters indicating the position.

  The pixel array 2 includes a plurality of (in this case, n) data signal lines SL1 to SLn and a plurality of (in this case, m) scanning signal lines GL1 crossing each of the data signal lines SL1 to SLn. GLm, and i is an arbitrary integer from 1 to n and j is an arbitrary integer from 1 to m. For each combination of the data signal line SLi and the scanning signal line GLj, the pixel PIX ( i, j) are provided.

  In the case of the present embodiment, each pixel PIX (i, j) includes two adjacent data signal lines SL (i-1) .SLi and two adjacent scanning signal lines GL (j-1) .GLj. It is arranged in the part surrounded by.

  As an example, the case where the image display device 1 is a liquid crystal display device will be described. In the pixel PIX (i, j), for example, as shown in FIG. 3, as a switching element, a gate is connected to a scanning signal line GLj, and a drain is connected. A field effect transistor SW (i, j) connected to the data signal line SLi; and a pixel capacitor Cp (i, j) having one electrode connected to the source of the field effect transistor SW (i, j). ing. The other end of the pixel capacitance Cp (i, j) is connected to a common electrode line common to all the pixels PIX. The pixel capacitance Cp (i, j) is composed of a liquid crystal capacitance CL (i, j) and an auxiliary capacitance Cs (i, j) added as needed.

  When the scanning signal line GLj is selected in the pixel PIX (i, j), the field effect transistor SW (i, j) is turned on, and the voltage applied to the data signal line SLi is changed to the pixel capacitance Cp (i, j). ). On the other hand, while the selection period of the scanning signal line GLj ends and the field effect transistor SW (i, j) is shut off, the pixel capacitance Cp (i, j) continues to hold the voltage at the time of shutting off. Here, the transmittance or reflectance of the liquid crystal changes according to the voltage applied to the liquid crystal capacitance CL (i, j). Therefore, if the scanning signal line GLj is selected and a voltage corresponding to the video data D to the pixel PIX (i, j) is applied to the data signal line SLi, the display state of the pixel PIX (i, j) is changed to It can be changed according to the video data D.

  In the liquid crystal display device according to the present embodiment, as a liquid crystal cell, a liquid crystal cell of a vertical alignment mode, that is, when no voltage is applied, the liquid crystal molecules are aligned substantially perpendicular to the substrate, and the pixel PIX (i, x) A liquid crystal cell in which liquid crystal molecules are tilted from a vertical alignment state according to a voltage applied to the liquid crystal capacitance CL (i, j) is employed. Mode).

  In the above configuration, the scanning signal line driving circuit 4 shown in FIG. 2 outputs a signal indicating whether or not the current period is a selection period, such as a voltage signal, to each of the scanning signal lines GL1 to GLm. Further, the scanning signal line driving circuit 4 changes the scanning signal line GLj that outputs a signal indicating the selection period based on a timing signal such as a clock signal GCK or a start pulse signal GSP provided from the control circuit 12, for example. I have. Thus, the scanning signal lines GL1 to GLm are sequentially selected at a predetermined timing.

  Further, the data signal line drive circuit 3 extracts the video data D... Input to the pixels PIX. Further, the data signal line drive circuit 3 sends the data signal lines SL1 to SLIX to the pixels PIX (1, j) to PIX (n, j) corresponding to the scan signal line GLj selected by the scan signal line drive circuit 4. Output an output signal corresponding to each of the video data D through SLn.

  The data signal line drive circuit 3 determines the sampling timing and the output timing of the output signal based on timing signals such as the clock signal SCK and the start pulse signal SSP input from the control circuit 12.

  On the other hand, each of the pixels PIX (1, j) to PIX (n, j) outputs the output signal supplied to its corresponding data signal line SL1 to SLn while the corresponding scanning signal line GLj is selected. In accordance with the signal, the brightness or the transmittance at the time of light emission is adjusted to determine its own brightness.

  Here, the scanning signal line driving circuit 4 sequentially selects the scanning signal lines GL1 to GLm. Therefore, all the pixels PIX (1,1) to PIX (n, m) of the pixel array 2 can be set to the brightness (gradation) indicated by the video data D for each pixel, and the image displayed on the pixel array 2 can be displayed. Can be updated.

  Note that the video data D may be the gradation level itself or a parameter for calculating the gradation level as long as the gradation level of the pixel PIX (i, j) can be specified. Now, as an example, a case where the video data is the gradation level itself of the pixel PIX (i, j) will be described.

  In the image display device 1, the video signal DAT provided from the video signal source S0 to the modulation drive processing unit 21 may be transmitted in frame units (entire screen units), or one frame may be divided into a plurality of fields. Although the data may be divided and transmitted in the field unit, a case where the data is transmitted in the field unit will be described below as an example.

  That is, in the present embodiment, the video signal DAT provided from the video signal source S0 to the modulation drive processing unit 21 divides one frame into a plurality of fields (for example, two fields) and is transmitted in units of the field. .

  More specifically, when transmitting the video signal DAT to the modulation drive processing unit 21 of the image display device 1 via the video signal line VL, the video signal source S0 transmits all video data for a certain field. Video data for each field is transmitted in a time-division manner by transmitting video data for the next field.

  The field is composed of a plurality of horizontal lines. In the video signal line VL, for example, after all the video data for a certain horizontal line is transmitted in a certain field, the horizontal signal for the next horizontal line is transmitted. The video data for each horizontal line is transmitted in a time-division manner, for example, by transmitting the video data of the horizontal line.

  In the present embodiment, one frame is composed of two fields. In the even field, video data of an even-numbered horizontal line among the horizontal lines constituting one frame is transmitted. In the odd field, video data of an odd-numbered horizontal line is transmitted. Further, the video signal source S0 also drives the video signal line VL in a time-division manner when transmitting video data for one horizontal line, and each video data is sequentially transmitted in a predetermined order.

  Here, as shown in FIG. 1, the modulation drive processing unit 21 according to the present embodiment is inputted to a frame memory (storage means) 31 for storing video data for one frame up to the next frame, and to an input terminal T1. The video data D (i, j, k) of the current frame FR (k) is written to the frame memory 31 and the video data D0 (i, j, k-1) of the previous frame FR (k-1) is written from the frame memory 31. ) And outputs it as the previous frame video signal DAT0, and the video data D (i, j, k) of the current frame FR (k) so as to emphasize the gradation transition from the current frame to the previous frame. ), And outputs a corrected video data D2 (i, j, k) as a corrected video signal DAT2. In the present embodiment, for convenience of explanation, of the video data output from the frame memory 31, the video data of the previous frame FR (k-1) is denoted by D0 (i, j, k-1), and before and after. The video data (described later) of the frame FR (k-2) is referred to as D00 (i, j, k-2). Further, based on both the video data D00 (i, j, k-2) and D0 (i, j, k-1), the video video data generated by the previous frame gradation correction circuit 34 described below is converted to D0a (i, j, k). j, k-1).

  Further, in the present embodiment, the frame memory 31 also stores the video data of the previous frame up to the next frame, and the control circuit 32 stores the video data of the frame before the previous frame FR (k−2) from the frame memory 31. The data D00 (i, j, k-2) is read out and output as a two-frame video signal DAT00 before the previous one.

  Further, in the modulation drive processing unit 21 according to the present embodiment, for each pixel PIX (i, j), the pixel PIX (i, j) converts the video data D00 (i, j, k-2) to the video data D0. (i, j, k-1) is predicted, and the video data D0 (i, j, k-1) of the previous frame FR (k-1) is replaced with the predicted value D0a. A previous frame tone correction circuit (second correction means) 34 for correcting and outputting the corrected signal to (i, j, k-1) is provided, and the modulation processing unit 33 outputs the corrected previous frame video signal DAT0a and Based on the current frame video signal DAT, the video data D (i, j) of the current frame FR (k) is emphasized so that the gradation transition from the previous frame of each pixel PIX (i, j) to the current frame is emphasized. , k).

  Here, if the response speed of the pixel PIX (i, j) is very slow, in the previous frame FR (k-1), although the gradation transition from the frame before the previous frame to the previous frame is emphasized, The pixel PIX (i, j) may not be able to reach the gradation indicated by the video data D (i, j, k-1) of the previous frame FR (k-1). In this case, in the current frame FR (k), if it is assumed that the gradation transition has been sufficiently performed from the previous two times to the previous time, and the gradation transition is emphasized, the gradation transition cannot be appropriately emphasized, and there is a possibility that white light or black sun phenomenon may occur. There is.

  For example, as shown by the solid line in FIG. 4, when the gradation transition from the last two previous times to this time is from decay to rise, as shown by the broken line in FIG. Although the luminance level at the start of the frame FR (k-1) has not sufficiently decreased, the current frame FR (k) has the same effect as when the gradation has sufficiently transitioned (indicated by a chain line in the figure). When the pixel is driven, the grayscale transition is excessively emphasized, and white light is generated.

  In addition, as shown by the solid line in FIG. 5, when the gradation transition from the last two previous times to the current time is rise → decay, as shown by the broken line in FIG. Although the luminance level at the start of the frame FR (k-1) has not risen sufficiently, the current frame FR (k) has the same gradation transition as in the case of the current frame FR (k) (indicated by the chain line in the figure). When the pixels are driven, the gradation transition is overemphasized, and blackening occurs.

  When the above-mentioned white lightening or blackening occurs, these gradations are out of the range from the previous gradation to the current gradation, so that they are easily noticeable by the user, and the display quality of the image display device is greatly reduced. Let it. In particular, when white light occurs, even if the occurrence period is instantaneous, it is easy for the user to notice, so that the display quality is particularly deteriorated.

  On the other hand, the previous frame gradation correction circuit 34 according to the present embodiment performs the correction based on both the video data D00 (i, j, k-2) and D0 (i, j, k-1) before correction. The gradation reached by the pixel PIX (i, j) is predicted by the gradation transition from the frame before the previous frame to the previous frame, and the video data D0 (i, j, k-1) of the previous frame FR (k-1) is predicted. To the predicted value D0a (i, j, k-1). As a result, it is possible to prevent the occurrence of whitening and blackening, and to improve the display quality of the image display device 1.

  Further, since the frame memory 31 stores the video data D (i, j, k) before the correction, unlike the display device 101 shown in FIG. It does not accumulate over time. Therefore, even if the accuracy of the prediction calculation is reduced to such an extent that it is possible to prevent the occurrence of white light and black sun, unlike the image display device 101, the gradation control of each pixel PIX diverges or vibrates. Nothing. As a result, it is possible to realize the image display device 1 capable of preventing the occurrence of white light and black sun with a circuit scale smaller than that of the image display device 101.

  More specifically, as shown in FIG. 1, the previous frame tone correction circuit 34 according to the present embodiment performs, for each combination of the previous tone and the present tone, the video data of the combination in the modulation process. When the pixel PIX (i, j) is inputted to the unit 33, the pixel PIX (i, j) is provided with an LUT (Look Up Table) 41 which records the gradation reached at the time when the pixel PIX (i, j) is driven by the next video data. ing. Furthermore, in the present embodiment, in order to reduce the storage capacity required for the LUT 41, the reaching gradation stored in the LUT 41 is not a reaching gradation of all combinations of gradations, but a predetermined combination. The preceding frame tone correction circuit 34 interpolates the reached tone corresponding to each combination stored in the LUT 41 to obtain the two video data D00 (i, j, k-2) and An arithmetic circuit 42 is provided for calculating the attained tone corresponding to the combination of the data D0 (i, j, k-1) and outputting the calculation result as a predicted value D0a (i, j, k-1). .

  In the present embodiment, in order to reduce the storage capacity required for the frame memory 31, the control circuit 32 reduces the data depth of the video data D (i, j, k) of the current frame FR (k). Then, the data is stored in the frame memory 31, and is output as the video data D0 (i, j, k) of the previous frame FR (k) in the next frame FR (k + 1). The control circuit 32 further reduces the data depth of the video data D0 (i, j, k-1) of the previous frame FR (k-1), stores the data depth in the frame memory 31, and stores the next frame FR (k-1) k + 1), it is output as the video data D00 (i, j, k-1) of the frame FR (k-1) before the previous frame.

As an example, in the present embodiment, the data depth of the video data D00 (i, j, k-2) of the frame before the previous frame FR (k-2) and the video data D0 (i) of the previous frame FR (k-1) , j, k-1) are set to 4 bits and 6 bits. In this case, even if each of R, G, and B is stored, only 30 bits are required. Therefore, when a general-purpose memory (a memory having a data bit width set to 2 ⁿ ) is used, the video data D00 (i, j, k-2) of the frame FR (k-2) before the previous frame is also stored. Despite this, a memory having the same storage capacity as that for storing the video data D0 (i, j, k-1) of the previous frame FR (k-1) can be used.

  Further, in the present embodiment, as shown in FIG. 6, the area expressed by the combination of gradations is divided into 8 × 8 calculation areas. As shown in FIG. Attained gradations are stored for the four corner points (9 × 9 points). In FIGS. 6 and 7, the vertical axis indicates the start grayscale (the grayscale of the frame before the previous frame), and the horizontal axis indicates the end grayscale (the grayscale of the previous frame). The gradation is increasing. Further, FIGS. 6 and 7 show the case where each of the gradations is 256 gradations, so that the reaching gradation is stored every 32 gradations.

  Here, FIG. 7 shows a numerical example in the case where a liquid crystal element of a vertical alignment mode and a normally black mode is employed as the pixel PIX (i, j). In this liquid crystal element, the response speed to the decay gradation transition is slower than in the case of the rise, and even if it is modulated and driven so as to emphasize the gradation transition, in the decay gradation transition from the last time to the previous time, A difference easily occurs between the actual gradation transition and the desired gradation transition. Therefore, the area α1 in which the actual arrival value is much larger than the gradation (E) to be reached is wider than the area α2 in which the arrival value is much smaller than the gradation to be reached. Has become. Note that the regions α1 and α2 are not corrected by the previous frame tone correction circuit 34, and the modulation processing unit 33 performs processing based on the video data D (i, j, k-1) of the previous frame FR (k-1). When the video data D (i, j, k) of the current frame FR (k) is corrected, it is an area where the video data D (i, j, k) and the actual gradation are different enough to be visually recognized by the user. .

  Further, when the combination (S, E) of the two video data D00 (i, j, k-2) and the video data D0 (i, j, k-1) is input, the arithmetic circuit 42 Which of the above-mentioned calculation areas belong.

Further, the arithmetic circuit 42 sets the reached gradations at the four corners of the calculation area to A, B, C, and D in the order of upper left corner, upper right corner, lower right corner, and lower left corner, respectively, and sets the width of the calculation area. Y × X, and the value obtained by normalizing the difference between the combination (S0, E0) of the upper left corner and both combinations (S, E) to (1, 1) is (Δy, Δx) = ((S−S0) / Y, (E−E0) / X), when Δx> = Δy, the arithmetic circuit 42 reads the reaching gradations A, B, and C from the LUT 41, and calculates the following expression (1). As shown,
D0a (i, j, k-1) = A + Δx · (BA) + Δy · (CB) (1)
D0a (i, j, k-1) is calculated.

If Δx <Δy, the arithmetic circuit 42 reads out the respective reaching gradations A, C, and D from the LUT 41, and as shown in the following equation (2):
D0a (i, j, k-1) = C + Δx · (C−D) + (1−Δy) · (DA) (2)
D0a (i, j, k-1) is calculated.

  For example, in the examples of FIGS. 6 and 7, when (S, E) is (144, 48), it is surrounded by (128, 32), (128, 64), (160, 64), and (160, 32). The calculated calculation area is specified, and the video data D0a (i, j, k-1) of the corrected previous frame FR (k-1) becomes 70. Therefore, based on the video data D (i, j, k) = 48 of the previous frame FR (k-1), the modulation processing unit 33 converts the video data D (i, j, k) of the current frame FR (k) into Unlike the case of correction, the video data D (i, j, k) is corrected based on the corrected video data D0a (i, j, k-1) = 70, so that the occurrence of white light can be prevented.

  In the above description, the case where the data depth (bit width) of the reached gradation stored in the LUT 41 is the same value (8 bits) as the video data D (i, j, k) has been described as an example. If the storage capacity of the LUT 41 is strongly required to be reduced, the data depth (bit width) of each reaching gradation stored in the LUT 41 is changed to the video data D00 (i, j) of the frame immediately before the previous frame FR (k-2). , k-2) and the data depth of the video data D0 (i, j, k-1) of the previous frame FR (k-1). desired.

  Even in this configuration, the bit width is set to the same bit width as the significant figure of the operation using the video data two times before and the previous time, that is, the shorter bit width. Therefore, the storage capacity required for the LUT 41 can be reduced to the greatest extent that the calculation accuracy is not reduced.

[Second embodiment]
In the above description, the case where the previous frame tone correction circuit 34 constantly corrects the previous frame video signal DAT0 has been described as an example. On the other hand, in the modulation drive processing unit 21a according to the present embodiment, the prediction value D0a (i, j, k-1) by the previous frame gradation correction circuit 34 and the video data D0 of the previous frame FR (k-1) are provided. If the difference (absolute value) from (i, j, k-1) is equal to or greater than a predetermined threshold, the previous frame tone correction circuit 34a outputs the predicted value D0a (i, j, k-1), In other cases, the previous frame tone correction circuit 34a outputs the previous frame video signal DAT0 as it is.

  In the present embodiment, the threshold value is set to about four gradations, as an example when the gradation of each video data D (i, j, k) is 8 bits. Note that there are various factors such as quantization noise as factors for lowering the prediction accuracy, and the threshold may be set to about 4 to 16 depending on these influences.

  Here, when the difference between the predicted value and the target value (D0 (i, j, k-1)) is small, the pixel difference in the previous frame FR (k-1) is larger than when the difference is large. The gradation of PIX (i, j) is sufficiently close to the gradation indicated by the video data D0 (i, j, k-1) of the previous frame FR (k-1). Therefore, the previous frame tone correction circuit 34a does not correct the image data, and the modulation processing unit 33 performs the image data D (i, j) of the current frame FR (k) based on the image data D0 (i, j, k-1). , k), there is little risk of whitening or blackening, and even if it occurs, the degree of whitening or blackening is small. Further, when the difference between the predicted value and the target value is small, the relative magnitude of the error at the time of prediction becomes larger than when the difference between the two is large. Therefore, when the gradation transition is emphasized by the modulation processing unit 33, a change in gradation due to an error at the time of prediction is easily recognized by the user.

  On the other hand, when the difference between the predicted value and the target value (D0 (i, j, k-1)) is large, whitening or blackening tends to occur unless the previous frame video signal DAT0 is corrected. Further, since the relative error at the time of prediction is small, even if the previous frame video signal DAT0 is corrected, a change in gradation caused by the error at the time of prediction is difficult to be visually recognized by the user.

  In the present embodiment, if the difference between the predicted value and the target value (D0 (i, j, k-1)) is smaller than the threshold value, that is, even if the previous frame video signal DAT0 is not corrected, When the previous frame video signal DAT0 is corrected, and the display quality is likely to be reduced when an error occurs during prediction, the previous frame gradation correction circuit 34a corrects the previous frame video signal DAT0. If the previous frame video signal DAT0 is not corrected, the previous frame video signal DAT0 is corrected only when white lightening or black sun phenomenon occurs. As a result, it is possible to prevent the occurrence of white glow and black sun, while suppressing a decrease in display quality due to an error in prediction.

[Third embodiment]
In the second embodiment, the configuration in which the previous frame gradation correction circuit 34a determines whether or not correction is necessary based on the difference between the predicted value and the target value has been described. A description will be given of a configuration in which information indicating the necessity is written, and the preceding frame gradation correction circuit refers to the information and determines whether the necessity of the correction is required.

  That is, in the LUT 41b according to the present embodiment, as shown in FIG. 8, the respective regions α1 and α2, that is, the previous frame gradation correction circuit 34 does not perform correction, and the modulation processing unit 33 performs the previous frame FR (k−1) When the video data D (i, j, k) of the current frame FR (k) is corrected based on the video data D (i, j, k-1) of the current frame, the video data D (i, In the area where the actual gradation is different from (j, k), the same value as in FIG. 7 is stored, but in the remaining area α3, the target value (E) itself is stored.

  On the other hand, the arithmetic circuit 42b according to the present embodiment receives the combination (S, E) of the video data D00 (i, j, k-2) and the video data D0 (i, j, k-1), When it is specified which of the calculation areas the combination (S, E) belongs to, the predetermined arrival gradation is read out from among the arrival gradations A to D at the four corners of the calculation area, and It is determined whether or not the attained tone matches the tone at the boundary of the calculation area, and it is determined whether or not the target value is recorded as the attained tone, that is, whether or not the area α3. Further, when the arithmetic circuit 42b determines that it belongs to the region α3, the arithmetic circuit 42b does not correct the previous frame video signal DAT0, and only when it determines that it belongs to the regions α1 and α2, The frame video signal DAT0 is corrected.

  Therefore, as in the second embodiment, if no whitening or blackening occurs and a decrease in display quality due to an error in prediction is expected, the previous frame video signal DAT0 is not corrected, and Only when black sun phenomenon occurs, the previous frame video signal DAT0 can be corrected.

[Fourth embodiment]
In the present embodiment, a configuration will be described in which the correction processing by the previous frame gradation correction circuit is changed according to the temperature. The present invention can be applied to any of the first to third embodiments. Hereinafter, a case where the present invention is applied to the third embodiment will be described.

  That is, as shown in FIG. 9, the modulation drive processing unit 21c according to the present embodiment is provided with a temperature sensor 35 for detecting the temperature of the pixel PIX in addition to the configuration of the third embodiment. When a combination of the video data D00 of a certain frame before the previous frame and the video data D0 of the previous frame is input, the frame gradation correction circuit 34c determines whether to correct the video data D0 and the corrected video data D0a. It changes according to the temperature detected by the temperature sensor 35.

  Specifically, the previous frame gradation correction circuit 34c according to the present embodiment is provided with a plurality of LUTs 41c respectively corresponding to each predetermined temperature range. In each LUT 41c, the attained value in the corresponding temperature range is stored similarly to the LUT 41.

  On the other hand, the calculation circuit 42c of the previous frame gradation correction circuit 34c selects the LUT 41c to be referred to at the time of the interpolation calculation from each LUT 41c according to the temperature information from the temperature sensor 35. The arithmetic circuit 42c and an arithmetic circuit 42e described later correspond to the control means described in the claims.

  Here, for example, when a liquid crystal element is adopted as the pixel PIX, the response speed of the liquid crystal element changes depending on the temperature. As described above, when the pixel PIX whose response speed changes depending on the temperature is employed, when the previous frame gradation correction circuit 34c does not perform correction, the modulation processing unit 33 corrects the video data D of the current frame, and the brightness of the current frame is reduced. Whether or not black sun sinks occurs changes.

  However, in the above-described configuration, even if the response speed of the pixel PIX changes depending on the temperature and the correction processing required to prevent the white light and the black sun phenomenon changes, the previous frame gradation correction circuit 34c outputs the current pixel PIX. The video signal DAT0 of the previous frame can be corrected in accordance with the temperature of .times., So that regardless of the temperature, it is possible to prevent the occurrence of white light and black sun.

  Further, the previous frame gradation correction circuit 34c according to the present embodiment stops correction of the previous frame video signal DAT0 when the temperature rises and reaches a predetermined temperature range. Therefore, when the temperature rises and the pixel PIX (i, j) can respond at a sufficient speed, and the whitening or the black sun due to the lack of response does not occur, the modulation processing unit 33 performs the correction before the correction. The video signal DAT of the current frame is corrected based on the video signal DAT0 of the previous frame and the video signal DAT of the current frame so as to emphasize the gradation transition from the previous frame to the current frame.

  As a result, the following phenomenon, that is, the phenomenon that the transition of the gradation is suppressed by the previous frame gradation correction circuit 34c does not occur despite the temperature at which the white light and the black sun due to the insufficient response do not occur. Thus, it is possible to prevent the response speed of the image display device 1 from decreasing.

  In the above description, the case where the LUT 41c is switched has been described as an example. However, since the attained value changes monotonously with respect to a change in the temperature direction, the arithmetic circuit 42c determines that the two LUTs 41c that are closest to the current temperature. Then, the reached value at the current temperature may be calculated by reading the reached value at each temperature and interpolating between the reached values. With this configuration, even if the number of LUTs 41c is small, it is possible to more accurately prevent the occurrence of white light and black sun.

[Fifth Embodiment]
In the present embodiment, the bit width of the video data D00 (i, j, k-2) of the frame before the second frame stored in the frame memory 31 and the video data D0 (i, j, k-1) of the previous frame are stored according to the temperature. ) Will be described. The present invention can be applied to any of the first to fourth embodiments. Hereinafter, a case where the present invention is applied to the fourth embodiment will be described.

  That is, in the modulation drive processing unit 21d according to the present embodiment, as shown in FIG. 9, the control circuit 32d stores the video data D00 (i , j, k-2) and the bit width of the video data D0 (i, j, k-1) of the previous frame, and as the temperature range becomes lower, the video data D00 (i , j, k-2), and the bit width of the video data D0 (i, j, k-1) of the previous frame is reduced by the increased bit width.

  Here, in order to reduce the storage capacity of the frame memory 31, the bits of both the video data D00 (i, j, k-2) and D0 (i, j, k-1) stored in the frame memory 31 are set. The total width is limited to a predetermined bit width (for example, 10 bits), and the bit width of each of the video data D00 (i, j, k-2) and D0 (i, j, k-1) Are set so that the video data D0 (i, j, k-1) of the previous frame can be corrected most accurately. On the other hand, as the response speed of the pixel PIX (i, j) becomes slower, the gradation reached by the pixel PIX (i, j) by the gradation transition from the frame before the previous frame to the previous frame changes the video data of the frame before the previous frame. Therefore, when the temperature changes, the optimal allocation of the bit widths of the video data D00 (i, j, k-2) and D0 (i, j, k-1) also changes.

  When the response speed of the pixel PIX changes according to the temperature and the optimal bit allocation changes, the previous-frame gradation correction circuit 34d according to the present embodiment sets both video data D00 (i) according to the current temperature of the pixel PIX. , j, k-2) and D0 (i, j, k-1) are changed, and as the temperature range becomes lower, the video data D00 (i, j, k-2) of the frame immediately before the previous frame is obtained. ) To increase the bit width. As a result, irrespective of the temperature change, the allocation of the respective bit widths can be maintained in an appropriate state, and the video data D0 (i, j, k-1) can be corrected with higher accuracy. Therefore, it is possible to more accurately prevent the occurrence of white light and black sun.

  For example, assuming that the total value of the bit widths of the video data of the previous and previous frames is 10 bits as in the numerical example described above, in the normal temperature range, the video data D00 (i, j, k- The bit width of 2) is set to 3 bits, and is changed to 2 bits when the temperature becomes higher, and to 4 bits when the temperature becomes lower.

  The arithmetic circuit 42c (42 to 42b) refers to the LUT 41c (41 · 41b) to generate the corrected video data D0a. In addition, as a result of a strong demand for reducing the storage capacity of the LUT, When Δy described in the above equations (1) and (2) cannot be calculated when the bit width of the video data D00 is the smallest, the arithmetic circuit 42 determines the more of the arrival values A to D at the four corners of the calculation area. It is desirable to calculate the corrected video data D0a (i, j, k-1) based on the two corners (C and D) corresponding to the low video data D00 (i, j, k-2). If the calculation area cannot be specified because the bit width of the video data D00 is insufficient, the lowest video data D00 (of the arrival values A to D of the four corners of the plurality of calculation areas corresponding to the video data D00 is the lowest. It is preferable to calculate the corrected video data D0a (i, j, k-1) based on the two corners corresponding to (i, j, k-2).

  For example, as shown in FIGS. 7 and 8, the combination (S, E) of the video data D00 (i, j, k-2) and the video data D0 (i, j, k-1) is 8 × 8. When the reached values at the four corners of each calculation area are stored in the LUT 41c, when the bit width of the video data D00 (i, j, k-2) is reduced to 3 bits, The calculation area can be specified, but Δy cannot be calculated (always 0). In this case, the arithmetic circuit 42c calculates the corrected video data D0a (i, j, k-1) based on C and D among the arrival values A to D at the four corners. When the bit width is 2 bits, the calculation area itself cannot be specified. For example, (SE) = (128,48) is (128,32), (128,64), (160,64) And a calculation area surrounded by (160, 32) and a calculation area surrounded by (160, 32), (160, 64), (192, 64), and (192, 32). I will. In this case, the arithmetic circuit 42c calculates the corrected video data D0a (i, j, k-1) based on (192,64) and (192,32) among the four corner arrival values. .

  Here, among the arrival values stored in the LUT 41c, the arrival value corresponding to the lower video data D00 is lower. Also, white light that occurs when the corrected video data D0a (i, j, k-1) is too large is more noticeable to the user than black sink that occurs when the image data D0a (i, j, k-1) is too small.

  Therefore, the arithmetic circuit 42c corrects the video data D0a (i, j, k-1) based on the two corners (C and D) corresponding to the lower video data D00 (i, j, k-2). ) Can realize the image display device 1 in which the deterioration of the display quality is less noticeable.

[Sixth embodiment]
By the way, in each of the above embodiments, the case where the reached value is stored in the LUT 41 (41b / 41c) has been described as an example, but the present invention is not limited to this. As described above, since the occurrence of white light is most likely to degrade the display quality, a gradation larger than the reached value is described in the LUT 41 in the LUT 41 so that the occurrence of white light can be reliably prevented. When the correction of the previous frame video signal DAT0 is necessary, the correction circuit 34 (34a to 34d) may correct the previous frame video signal DAT0 to a gradation larger than the reached value.

  In this configuration, the gradation transition enhancement from the previous frame to the current frame can be suppressed as compared with the case where the arrival value is described, so that it is possible to reliably prevent the occurrence of white light.

  Further, the correction processing by the previous frame gradation correction circuit may be changed according to the type of video. Note that the present invention can be applied to any of the first to fifth embodiments, but the case where the present invention is applied to the third embodiment will be described below.

  Specifically, in the modulation drive processing unit 21e according to the present embodiment, as shown in FIG. 10, in addition to the configuration of the third embodiment, a determination circuit 36 that determines the type of video is provided. When the combination of the video data D00 of a certain frame before the previous frame and the video data D0 of the previous frame is input, the previous frame gradation correction circuit 34e determines whether or not the video data D0 should be corrected and the corrected video data D0a. Is changed according to the determination result of the determination circuit 36.

  Specifically, the previous frame gradation correction circuit 34e according to the present embodiment is provided with a plurality of LUTs 41e respectively corresponding to predetermined temperature ranges. In each LUT 41e, the arrival value when a corresponding type of video is input is stored in the same manner as in the LUT 41. On the other hand, the calculation circuit 42e of the previous frame gradation correction circuit 34e selects the LUT 41e to be referred to at the time of interpolation calculation from each LUT 41e according to the temperature information from the determination circuit 36.

  Here, as described above, when the correction of the previous frame video signal DAT0 is necessary, the previous frame tone correction circuit 34e sets the correction value larger than the arrival value when correcting the previous frame video signal DAT0 to a tone larger than the arrival value. If it is excessively performed, while the occurrence of white light can be surely prevented, the response speed decreases. Therefore, the difference between the correction value and the attained value is set so that the occurrence of white glow can be suppressed within a range where the response speed decrease is not conspicuous. However, since the appropriate value of the difference between the two differs depending on the type of video, if the difference between the two is fixed, if many types of video are input, the appropriate value Difficult to set to a value.

  On the other hand, in the modulation drive processing unit 21e according to the present embodiment, the difference between the correction value and the reached value is changed according to the type of video. Therefore, for example, no matter what kind of video is input, such as a fast-moving video and a slow-moving video, it is possible to suppress the occurrence of white glow within a range where the reduction in response speed is not conspicuous.

  Further, the previous frame tone correction circuit 34e according to the present embodiment indicates that the type of video is a slow-moving video, and the previous frame tone correction circuit 34e does not correct the previous frame video signal DAT0. Also, if it is expected that no white light or black sun due to insufficient response will occur, the correction of the previous frame video signal DAT0 is stopped. As a result, in spite of displaying the following phenomenon, that is, displaying an image in which the motion is slow and no white light or black sun phenomenon occurs due to insufficient response, the gradation transition is performed by the previous frame gradation correction circuit 34e. The phenomenon of being suppressed does not occur, and the response speed of the image display device 1 can be prevented from lowering.

[Seventh embodiment]
In the present embodiment, the bit width of the video data D00 (i, j, k-2) of the immediately preceding frame stored in the frame memory 31 and the video data D0 (i, j, k) of the previous frame are stored according to the type of video. A configuration for changing the bit width of -1) will be described. The present invention can be applied to any of the first to sixth embodiments. Hereinafter, a case where the present invention is applied to the fourth embodiment will be described.

  That is, in the modulation drive processing section 21f according to the present embodiment, as shown in FIG. 10, the control circuit 32f stores the video data D00 (i , j, k-2) and the bit width of the video data D0 (i, j, k-1) of the previous frame are changed. The bit width of the video data D00 (i, j, k-2) is further expanded, and the bit width of the video data D0 (i, j, k-1) of the previous frame is reduced by the increased bit width. I have.

  Here, in order to reduce the storage capacity of the frame memory 31, the bits of both the video data D00 (i, j, k-2) and D0 (i, j, k-1) stored in the frame memory 31 are set. The total width is limited to a predetermined bit width (for example, 10 bits), and the bit width of each of the video data D00 (i, j, k-2) and D0 (i, j, k-1) Are set so that the video data D0 (i, j, k-1) of the previous frame can be corrected most accurately. On the other hand, the gradation reached by the pixel PIX (i, j) due to the gradation transition from the frame before the previous frame to the previous frame is more affected by the video data of the frame before the previous frame when a fast moving image is input. Easy to receive. Therefore, when the type of video changes and the expected speed of movement changes, the optimal bit width of each video data D00 (i, j, k-2) and D0 (i, j, k-1) Assignment also changes.

  When the type of video changes and the optimal bit allocation changes, the previous frame tone correction circuit 34f according to the present embodiment sets both video data D00 (i, j, k-) in accordance with the current video type. 2) and the bit widths of D0 (i, j, k-1) are changed, and if the type of video is a video with a faster movement, video data D00 (i, j, k-2) ) To increase the bit width. As a result, the allocation of each bit width can be maintained in an appropriate state regardless of the type of video, and the video data D0 (i, j, k-1) can be corrected with higher accuracy. Therefore, it is possible to more accurately prevent the occurrence of white light and black sun.

  In each of the above embodiments, a case where a liquid crystal cell of a vertical alignment mode and a normally black mode is used as a display element has been described as an example, but the present invention is not limited to this. A display in which the response speed is slow and a difference occurs between the actual gradation transition and the desired gradation transition in the gradation transition from the previous two times to the previous time even if the driving is performed by modulating so as to emphasize the gradation transition. With a device, substantially the same effects can be obtained.

  However, the liquid crystal cell in the vertical alignment mode and the normally black mode has a slower response time to the decay gradation transition than the rise case, and even if the liquid crystal cell is modulated and driven so as to emphasize the gradation transition, the liquid crystal cell is operated two times before. In the decay gradation transition to the previous time, a difference easily occurs between an actual gradation transition and a desired gradation transition, and white light is likely to occur. Therefore, it is particularly preferable to prevent the occurrence of white light with the configuration of the above embodiment.

  Further, in each of the above-described embodiments, a case has been described as an example where each member constituting the modulation drive processing unit is realized only by hardware, but the present invention is not limited to this. All or a part of each member may be realized by a combination of a program for realizing the above-described functions and hardware (computer) for executing the program. As an example, the modulation drive processing units (21 to 21f) may be realized as device drivers used when a computer connected to the image display device 1 drives the image display device 1. In the case where a modulation drive processing unit is realized as a conversion board built in or external to the image display device 1 and the operation of a circuit that realizes the modulation drive processing unit can be changed by rewriting a program such as firmware. By distributing the software and changing the operation of the circuit, the circuit may be operated as the modulation drive processing unit in each of the above embodiments.

  In these cases, if hardware capable of executing the above-described functions is provided, the modulation drive processing unit according to each of the embodiments can be realized only by causing the hardware to execute the program.

  In each of the above embodiments, the video data D00 (i, j, k-2) and the video of the previous frame FR (k-1) of the above-before-previous frame FR (k-2) stored in the frame memory 31 are stored. In order to limit the total bit width of the data D0 (i, j, k-1) to a predetermined bit width, the lower bits are truncated and stored. However, the present invention is not limited to this. Various storage methods and their combinations can be arbitrarily applied depending on the accuracy.

  In the following, some storage methods are exemplified, but the later methods increase the processing required for the memory instead of improving the memory use efficiency. As a result, the later method requires a larger circuit scale and requires an increase in the operating frequency of the circuit, which makes the method more difficult to implement. Therefore, the storage method (including a combination of a plurality of storage methods) should be selected so that the balance between the purpose of use of the display, the accuracy required to secure the required display characteristics, and the circuit scale is optimized. It is preferable to select.

1. Bit Cutting
This is a storage method exemplified in each of the above embodiments, in which lower bits exceeding required precision are discarded and necessary upper bits are recorded. As a result, the recording area can be saved most simply. For example, when the original video data is represented by 8 bits (in the case of 256 gradations), 0, 32, 64, 96, 128, 160, 192, and 224 are reduced from 0 by truncating the lower 5 bits. 7 can be recorded with 3 bits. In this method, since only necessary bits are cut out, the circuit scale required for this operation can be almost ignored.

2. Table of Contents (Indexing)
Dividing the range of values that can be taken by the original video data into predetermined small ranges, and storing the index assigned to each of the small ranges as to which small range the original video data belongs to. Is a method of storing. For example, focusing on the most significant bit that is not 0, for example, the range of values that can be taken by the original video data represented by 8 bits is 0 to 1 gradation, 2 to 3 gradation, 4 to 7, 8 to 15 gradation. If the image data is divided into gray scales, 16-31 gray scales, 32-63 gray scales, 64-127 gray scales, and 128 gray scales or more, and each is indexed by a numerical value from 0 to 7, 8-bit video data can be obtained. The table of contents can be set with 3 bits. Generally, a tone error is more remarkably observed on a lower tone side, and by recording a tone using such an index, a region where an error is more conspicuous can be recorded in more detail. In general, in order to prevent an increase in the circuit scale, each of the small areas is set so as to determine which small area the original video data belongs to by a relatively simple rule. By combining various conditions and rules, it is possible to more appropriately divide each small area or change the division of the small area. Therefore, it is desirable to combine appropriate conditions and rules within a range that does not reduce efficiency.

3. Hashing, coding (Huffman Coding, etc.) or other dictionary system Similar to the table of contents, but the data to be recorded (video data; gradation information) is expected to be clearly biased By allocating a lower-bit table of contents to an area having a higher appearance probability, more storage area can be saved. In addition, a storage and retrieval bidirectional translation system is required. For example, at the time of storage, the control circuit 32 refers to a correspondence table between regions and a table of contents, determines a table of contents corresponding to each region, and stores the table of contents. In addition to storing the data in the frame memory 31 and taking out the image data, the image data indicating the area corresponding to the table of contents stored in the frame memory 31 is output by referring to the correspondence table between the area and the table of contents. Translate in both directions.

4. Translation
Further, in order to more efficiently execute the above-described or later-described storage methods, data to be recorded may be appropriately converted. For example, an RGB gradation signal may be converted into a luminance signal and a color difference signal. With this conversion, 1. And 2. As described above, even when a storage method that can be realized with a relatively small circuit scale is adopted, the degree of deterioration of gradation information can be suppressed. As another conversion method, another appropriate method such as converting an RGB gradation signal into an RGB average value and a difference value from the average value may be selected.

5. Compression
When the limitation on the circuit size is relatively small, generally-used compression can be used, and the memory use efficiency is considerably improved. For example, after the above-described appropriate data conversion and encoding, compression may be performed by a technique such as run length. As an appropriate data conversion, in addition to the conversion methods exemplified above, frequency conversion (cosine conversion, Fourier conversion) or video data D00 (i, j, When converting (k-2), a conversion method such as conversion to a difference value using video data D0 (i, j, k-1) of the previous frame FR (k-1) may be adopted. As a known method in image processing, for example, conversion (image compression method) specified by JPEG (Joint Photographic Experts Group) or MPEG (Moving Picture Expert Group) may be appropriately combined. In addition, in order to store data of required accuracy with a smaller bit width, various storage methods are often combined in a range where an increase in circuit scale is allowed.

  Whichever storage method is used, the bit width of the video data D00 (i, j, k-2) of the frame FR (k-2) before the previous frame is limited to restrict the bit width of the previous frame FR (k-1). ) Can be stored with a smaller number of bits than the original data, so that the frame memory 31 can be stored in the same manner as in the above embodiments. Storage capacity can be reduced. Note that, in order to reduce the storage capacity of the frame memory 31, data having an accuracy necessary to correct the video data D0 (i, j, k-1) of the previous frame FR (k-1) is obtained by: It is desirable to store data with a bit width as small as possible.

  Further, not only the bit width of the video data D00 (i, j, k-2) of the frame before the previous frame FR (k-2) but also the video data D0 (i, j, k- If the bit width of 1) is also limited and stored, the storage capacity of the frame memory 31 can be further reduced. In this case, for example, the bit width of each of them may be limited separately by compressing them separately, or the data of the combination of both may be compressed, for example, to compress the data of both. On the other hand, the bit width may be limited. However, as described above, in many cases, if the use efficiency of the memory is to be further improved, the implementation becomes more difficult due to an increase in the circuit scale, an increase in the operating frequency of the circuit, and the like, and the frame FR (k− If the bit width of the video data D0 (i, j, k-1) as well as the bit width of the video data D00 (i, j, k-2) in 2) is limited, the implementation becomes more difficult. Therefore, it is only necessary to select the video data and the storage method that limit the bit width so that the balance between the accuracy and the circuit scale required to secure the intended use of the display and the required display characteristics is optimized. preferable.

  The driving method of the display device according to the present invention, in order to solve the above problems, with reference to the previous video data, to correct the current video data so as to emphasize the gradation transition from the previous to the current, In a driving method of a display device including a first correction step for supplying pixels, a previous data storage step of storing the current video data before correction in the first correction step until the next time, If the combination of the last two-time data storage step and the last two-time and previous video data stored in the two data storage steps is a predetermined combination, the previous video data referred to in the first correction step is stored. , A second correction step of correcting the previous video data so as to approach the video data of the previous time, that is, of increasing / decreasing the previous video data. It is characterized in that.

  In the above configuration, in the case where the combination of the previous and previous video data stored in the two data storage steps is a predetermined combination, the previous video data referred to in the first correction step is the video data of the previous two previous times. Is corrected so as to approach. Therefore, when the gradation transition from the previous two times to the previous time is a predetermined gradation transition, in the first correction step, when correcting the current video data so as to emphasize the gradation transition from the previous time to the current time, The correction amount can be reduced as compared with the case where there is no correction in the two correction steps.

  As a result, for example, when the gradation transition from the last two times to the present is performed in the first correction step as in the case of decay → rise or rise → decay, the following phenomenon occurs. That is, due to the synergistic effect of the insufficient response of the pixel in the gradation transition from the previous two times to the previous time and the gradation transition enhancement in the first correction step, the gradation of the current pixel is larger than the gradation indicated by the current video data. On the other hand, even when a phenomenon such as whitening or black sun phenomenon occurs, the occurrence of the phenomenon can be suppressed by suppressing the correction amount in the first correction step, and the display quality of the display device can be improved. On the other hand, since the two data storage steps store the video data before being corrected in the first correction step, unlike the configuration in which the corrected video data is stored, the two data storage steps are caused by the correction in the first correction step. No errors are superimposed and accumulated. Therefore, even if each of the above steps is performed by a circuit having a relatively small circuit scale and a low calculation accuracy for correction, the gradation control of the pixel does not diverge or vibrate. As a result, a display device with good display quality can be realized with a relatively small circuit scale.

  Further, the video data stored in the two data storage steps may have the same bit width as the current video data. However, in a case where a reduction in circuit size is particularly required, in addition to the above configuration, The sum of the bit widths of the video data before and after the previous video data stored in both data storage steps is set to a set value smaller than twice the bit width of the current video data, and is stored in the data storage step before the previous video data. The bit width of the video data before and after the last data storage is set to be equal to or less than the bit width of the previous video data stored in the previous data storage step, and at least one of the two data storage steps includes The bit width may be limited and stored so that the total value of the bit width of the previous video data becomes the above set value. In this configuration, since the bit width of the video data stored in each storage step is limited, the circuit scale can be reduced as compared with the case where all are stored.

  Further, in addition to the above configuration, the ratio of the bit width of the video data two times before the image data to the set value may be changed according to at least one of the type of the image and the temperature.

  Here, if the set value is limited to a value smaller than the bit width of the current video data, and if the ratio of the bit width of the video data two times before is too large in the set value, the previous value after the correction is corrected. In this case, the influence of the video data of the previous time can be more accurately reflected on the video data, but the influence of the previous video data cannot be accurately reflected. Therefore, it is desirable to set the ratio of the bit width of the video data two times before in the set value to an appropriate value according to the influence of both video data. On the other hand, when a fast-moving video is input, it is more susceptible to the video data of the frame before the previous frame. Therefore, if the type of video changes and the expected speed of the motion changes, The appropriate value changes. Similarly, when the temperature changes, the response speed of the pixel changes, so that an appropriate value of the above ratio changes.

  On the other hand, in the above configuration, the ratio of the bit width of the video data of the previous two times in the set value is changed according to at least one of the type of the image and the temperature. Therefore, the above ratio can be kept at an appropriate value. As a result, the display quality of the display device can be maintained at a high level.

  Further, in addition to the above configuration, the first correction step may include, if a difference between the previous video data after the correction and the previous video data before the correction is smaller than a predetermined threshold value, The current video data may be corrected with reference to the data.

  In this configuration, if the difference between the previous video data after correction and the previous video data before correction is smaller than a predetermined threshold, that is, even if the previous video data is not corrected, Is less likely to occur, and if the previous video data is corrected, and if an error occurs during the correction, the display quality is likely to deteriorate, the current video data is not the previous video data after the correction but the previous video data. It is corrected with reference to the previous video data. As a result, it is possible to prevent the occurrence of white glow and black sun, while suppressing a decrease in display quality due to a correction error in the second correction step.

  Also, instead of comparing with the threshold value, the second correction step may correct the previous video data only when the combination of the video data before last time and the previous video data is a predetermined combination. .

  With this configuration, the previous video data can be corrected only in the case of a combination that is predicted to have a high possibility of causing whitening or blackening, so that the display quality is deteriorated due to a correction error in the second correction process. While suppressing the occurrence of white glow and black sun.

  Further, in addition to the above configuration, in the second correction step, at least one of the combination to be corrected, a predetermined combination, and a correction amount may be changed according to a temperature.

  Here, when the temperature changes, the response speed of the pixel changes, so the combination in which the occurrence of white light or black sun phenomenon is predicted and the appropriate correction amount change. However, in the above configuration, at least one of the combination to be corrected, the predetermined combination, and the correction amount is changed according to the temperature, so that regardless of the temperature, it is possible to accurately prevent the occurrence of whitening or black sunshine. Thus, the display quality of the display device can be maintained at a high level.

  In addition, in addition to the above-described configuration, when at least one of the image type and the temperature satisfies a predetermined condition, the correction in the second correction step may be stopped. By the way, in the second correction step, when the previous video data is corrected to the video data of the previous two times, if the gradation transition from the previous two times to the current time is decay → rise or rise → decay, in the first correction step, The degree to which the gradation transition from the current to the present is emphasized is weakened. Therefore, at least one of the image type and the temperature satisfies the predetermined conditions, such as when the pixel temperature is high or the image type is a slow-moving image, and the previous image data need not be corrected. However, when the previous video data is corrected, the response speed may be undesirably reduced, even though it is expected that no white light or black sun will occur.

  On the other hand, in the above configuration, when at least one of the image type and the temperature satisfies the predetermined condition, the correction in the second correction step is stopped. Therefore, it is possible to prevent a decrease in response speed in a case where it is expected that no whitening or blackening will occur. If the above condition is not satisfied, the previous video data is corrected, so that it is possible to prevent the occurrence of white light and black sun without any trouble.

  Further, in addition to the above configuration, in the second correction step, in a case where the gradation transition from the previous two times to the previous time is a gradation transition that lowers the gradation, the gradation predicted to reach the pixel by the gradation transition The previous video data may be corrected so as to show a larger gradation.

  Here, in the second correction step, the previous video data may be corrected so that the gray level transition from the last two times to the previous time becomes a gray level that is predicted to reach a pixel due to the gray level transition. However, in this case, if it is not possible to predict the reached gradation with sufficient accuracy, there is a possibility that whitening or blackening may occur due to a difference between the predicted value and the actual gradation.

  On the other hand, in the above configuration, in the case where the gray level transition from the previous two times to the previous level is a gray level transition that lowers the gray level, the previous video data is displayed so as to indicate a gray level larger than the predicted attained gray level. Since the correction is made, even if a deviation occurs between the predicted value and the actual gradation, it is possible to prevent the occurrence of white light. As described above, by preventing the occurrence of white light which tends to cause a decrease in display quality between white light and black sun, even if a deviation occurs between the predicted value and the actual gradation, the display quality can be reduced. Can be suppressed.

  On the other hand, in order to solve the above problem, the display device according to the present invention refers to the previous video data, corrects the current video data so as to emphasize the gradation transition from the previous time to the current time, and corrects the pixel data. In the display device having the first correction means for supplying the current video data and the previous video data before correction by the first correction means to the next time, the storage means stores the current video data and the previous video data until the next time. A second correction unit that corrects the previous video data referred to by the first correction unit so as to approach the video data before the previous one, when the combination of the video data before and the previous time is a predetermined combination. .

  The display device having such a structure can drive pixels by the above-described display device driving method. Therefore, similarly to the method of driving the display device, a display device with high display quality and a relatively small circuit scale can be realized.

  In addition to the above configuration, the second correction unit includes a look-up table in which the previous video data after correction is stored corresponding to each combination of the video data two times before and the previous video data. The bit width of the previous video data described in the up-table may be set to the shorter one of the bit widths of the previous and previous video data.

  In this configuration, the bit width of the previous video data described in the look-up table is set to the same bit width as the significant digit of the operation using the video data before and after the previous video data, that is, the shorter bit width. I have. Therefore, the storage capacity required for the look-up table can be reduced to the greatest extent that the calculation accuracy is not reduced.

  In addition to the above configuration, the look-up table stores the gradation of the previous video data after correction of a predetermined combination among the combinations of the video data before and after the previous video, and The second correction means interpolates the gradation of the previous video data after correction stored in the look-up table and obtains the gradation of the previous video data after correction corresponding to the combination of the last two times and the previous video data. May be provided.

  According to the above configuration, the combination of the video data before and after the last time stored in the look-up table is limited to a predetermined combination. Therefore, the storage capacity of the lookup table can be reduced.

  Further, in addition to the above-described configuration, the second correction unit may output, for a predetermined combination among the combinations of the video data before the last time and the previous video data, the previous video data after the correction or the previous video data after the correction. A gradation table of video data may be stored, and for other combinations, a look-up table may be provided in which the previous video data itself or the gradation itself to be reached by the previous video data is stored. .

  In this configuration, when the combination is other than the predetermined combination, since the previous video data itself or the gradation itself to which the previous video data should reach is stored, refer to the lookup table. By correcting the previous video data, the correction of the previous video data can be stopped in cases other than the above combination. As a result, compared to the case where a table for judging whether or not the combination is provided separately, with a simple circuit configuration, it is possible to suppress a decrease in display quality due to a correction error in the second correction process and to reduce The occurrence of black sun can be prevented.

  Further, in addition to the above configuration, the second correction means is provided for each predetermined temperature range, and corresponds to the previous video data after correction or the previous video data corresponding to each combination of the video data before and after the previous time. A look-up table in which the gradation of the video data is stored; and a control unit for selecting a look-up table to be used for the previous correction of the video data from the look-up table. The look-up table may be switched accordingly.

  In this configuration, since the look-up table is switched according to the temperature, it is possible to accurately prevent the occurrence of white light and black sun regardless of the temperature, and to maintain the display quality of the display device at a high level. Further, since a lookup table is provided for each temperature range, even if the change in the correction process due to the temperature cannot be described by a simple mathematical expression, the correction process can be changed by a simple circuit.

  Further, the control means may switch the selected look-up table according to the type of the video data.

  When the gradation value of the previous video data after the correction is different from the gradation value that the previous video data should reach, an appropriate value of the difference between the two differs depending on the type of video. Therefore, in the above configuration, the control means switches the look-up table used for the previous correction of the video data according to the type of the video data. Accordingly, even if any type of video such as a fast-moving video and a slow-moving video is input, it is possible to suppress the occurrence of white glow within a range where the reduction in response speed is not conspicuous.

  Further, in addition to the above configuration, the total of the bit widths of the video data of the last time and the previous two times stored in the storage means is limited to a predetermined bit width, and the sum of the bit widths of the previous video data stored in the storage means is limited. The bit width and the bit width of the video data two times before may be changed according to the temperature.

  The response speed of the pixel changes according to the temperature. For example, as the response speed of the pixel becomes slower, the gradation reached by the pixel becomes more susceptible to the frame before the previous frame due to the gradation transition from the previous frame to the previous frame. For this reason, the optimal allocation of the bit widths of the video data before and after the previous video data stored in the storage means also changes.

  On the other hand, according to the above configuration, the allocation of each bit width can be maintained in an appropriate state regardless of the temperature change. For this reason, the previous video data can be corrected with higher accuracy, and the occurrence of white light and black sun can be prevented more accurately.

  Further, the control unit may change the bit width of the video data stored in the storage unit according to the type of the video data.

  The gray level reached by the pixel due to the gray level transition from the frame before the previous frame to the previous frame is more likely to be affected by the frame before the previous one when a fast moving image is input. Therefore, when the type of video changes and the expected speed of movement changes, the optimal allocation of the bit width of the video data before and after the previous video data stored in the storage means also changes.

  On the other hand, according to the above configuration, the assignment of the bit width of the video data before and after the video data to be stored in the storage unit is changed according to the type of the video. Therefore, regardless of the type of video, the allocation of each bit width can be maintained in an appropriate state. Therefore, the previous video data can be corrected with higher accuracy, and the occurrence of white light and darkening can be more accurately prevented.

  Further, in addition to the above configuration, the present video data has an 8-bit width for each of the three primary colors, and the storage means stores, for each of the three primary colors, the bit width of the video data two times before and the previous video data. At least the bit width of the video data at least two times out of the previous and previous video data may be limited so that the total with the bit width becomes 10 bits.

In this configuration, since the total bit width of the video data of the three primary colors is 30 (3 × 10) bits, when a general-purpose memory (a memory in which the data bit width is set to 2 ⁿ ) is used, the previous video is used. The storage means can be realized by a memory having the same storage capacity as when data (for three primary colors) is stored as it is.

  Further, in addition to the above configuration, the pixel may be a liquid crystal element of a normally black mode and a vertical alignment mode. Here, when the liquid crystal element of the normally black mode and the vertical alignment mode is used as a pixel, the response speed to the gradation transition of the decay is slower than the case of the rise, and the modulation is performed so as to emphasize the gradation transition. Even in the case of the decay gradation transition from the last two times to the previous time, a difference easily occurs between the actual gradation transition and the desired gradation transition. Therefore, when a gradation transition from decay to rise occurs, white light is generated, and the user can easily recognize the white light. On the other hand, in the above-described configuration, the occurrence of white light is suppressed by the second correction unit. Therefore, the generation of white light can be prevented, and the display quality of the display device can be improved, even though the liquid crystal element in the normally black mode and the vertical alignment mode is used as a pixel.

  A program according to the present invention is a program that causes a computer to execute the above-described steps. Therefore, when the program is executed by the computer, the computer can drive the display device by the above driving method. As a result, the display quality of the display device can be improved with a relatively small circuit scale, as in the method of driving the display device.

  Further, these programs may be used as computer data signals. For example, the display device can be driven by the above-described driving method by receiving the above-described computer data signal embedded and transmitted in a carrier wave and causing a computer to execute the signal.

  In addition, by recording these programs on a computer-readable recording medium, it is possible to easily store the program and distribute the recording medium or a computer program product including the recording medium. Further, by causing the computer to read the recording medium, the display device can be driven by the above driving method. As the computer program product, for example, a product in which the recording medium and the manual are packaged in one package, a computer including the recording medium, and the like are included.

  According to the present invention, a display device with high display quality can be realized with a relatively small circuit scale, so that it can be suitably used for various display devices including a liquid crystal display device such as a liquid crystal television broadcast receiver and a liquid crystal monitor. .

1 FIG. 1 illustrates an embodiment of the present invention, and is a block diagram illustrating a main configuration of a modulation drive processing unit provided in an image display device. FIG. 3 is a block diagram illustrating a main configuration of the modulation drive processing unit. FIG. 3 is a circuit diagram illustrating a configuration example of a pixel provided in the image display device. 9 is a timing chart showing an operation of the modulation drive processing unit and showing an actual luminance level when the gradation transition from the last two times to the current time is from decay to rise. 9 is a timing chart showing an operation of the modulation drive processing unit and showing an actual luminance level when the gradation transition from the last two times to the current time is rise → decay. 5 is a diagram showing a relationship between a region represented by a combination of video data of a frame before the previous frame and video data of the previous frame and a calculation area. FIG. 3 is a diagram showing contents of a lookup table provided in the modulation drive processing unit. FIG. 8 illustrates another embodiment of the present invention, and is a diagram illustrating contents of a lookup table provided in the modulation drive processing unit. FIG. 14 illustrates yet another embodiment of the present invention, and is a block diagram illustrating a main configuration of a modulation drive processing unit. FIG. 8 illustrates another embodiment of the present invention, and is a block diagram illustrating a main configuration of a modulation drive processing unit. FIG. 23, showing a conventional technique, is a block diagram illustrating a main configuration of a display device.

Explanation of reference numerals

1 image display device (display device)
31 frame memory (storage means)
33 Modulation processing unit (modulation means)
34-34f Previous frame gradation correction circuit (decision means)
41 / 41c / 41e Look-up table 42c / 42e Arithmetic circuit (control means)

Claims (34)

Determining a first drive signal input at a first time and a value corresponding to a previous drive signal input at a time before the first time;
Based on the determined value, a second input at the second time point is performed based on the determined value so as to emphasize a gradation transition from the first time point to a second time point subsequent to the first time point. A modulating step of generating a corrected second drive signal for modulating the drive signal and supplying the modulated drive signal to the pixel.   The method according to claim 1, wherein the determined value is one of a corrected first drive signal and an uncorrected first drive signal. Storing the previous video data associated with the first drive signal together with the last two video data associated with the previous drive signal;
The method according to claim 1, wherein in the determining step, a value corresponding to the previous drive signal is determined based on the stored second and last video data. Before the above, one or more frames of video data are configured from the first and second drive signals,
The deciding step is to correct the previous video data indicated by the first drive signal from the last two video data indicated by the previous drive signal to correct the previous video data indicated by the first drive signal. 2. The method according to claim 1, further comprising a step of predicting a gray level reached by a pixel by gray level transition to data.   The modulating step includes, based on the corrected first drive signal for obtaining the corrected second video signal, from the previous frame of the pixel indicated by the first drive signal, from the second frame of the pixel. 5. The display device according to claim 4, further comprising a step of correcting video data indicated by said second drive signal so as to emphasize a gradation transition to a current frame indicated by said drive signal. Drive method. The determined value is one of a corrected first drive signal and an uncorrected first drive signal,
4. The method according to claim 3, wherein the determining step generates the determined value according to a combination of predetermined two-time and previous video data. The determining step, in the case of the predetermined combination, correcting the previous video data indicated by the first drive signal to obtain the corrected first drive signal;
7. The display device according to claim 6, further comprising a step of outputting the first drive signal without correction when the combination of the video data two times before and the previous time is not a predetermined combination. Drive method. The predetermined combination corresponds to a correction amount to be given to the corrected first drive signal,
7. The method according to claim 6, wherein the determining step includes an adjusting step of changing the correction amount based on at least one of a type of the image and a temperature.   9. The method according to claim 8, wherein when at least one of the type and the temperature of the image satisfies a predetermined threshold condition, the execution of the adjusting step is stopped. . The first drive signal includes the previous video data,
The previous drive signal includes the video data from the previous time,
In the above-described determination step, the gradation level determined based on the video data two times before and the previous time falls from the gradation level two times before when the gradation transitions from the previous two-time gradation level to the previous gradation level. 2. The method according to claim 1, further comprising the step of: correcting the previous video data so that the pixel has a higher gray level than the gray level predicted to be reached by the gray level transition. The driving method of the display device according to the above. The two-time video data and the previous video data have a predetermined combination of bit widths, and the bit width is twice as large as the bit width of the current video data for the second drive signal. Is also set small,
The bit width of the video data two times before is set to be the same as or narrower than the bit width of the previous video data,
In the storing step, the pre-last video data and the previous video data are stored with a limited bit width such that the bit widths of the video data of the last preceding video and the previous video data are the predetermined values. 7. The method for driving a display device according to claim 6, wherein: A computer program product including a recording medium on which a computer program for driving a display device to a processor that processes the computer program product,
A determining step of determining a value corresponding to a first drive signal input at a first time point and a previous drive signal input at a time point earlier than the first time point; Based on the determined value, a second input at the second time point is performed based on the determined value so as to emphasize a gradation transition from the first time point to a second time point subsequent to the first time point. A computer program product for causing the processor to execute a modulation step of generating a corrected second drive signal for modulating the drive signal and supplying the modulated drive signal to the pixel.   A program for causing a computer to execute the steps according to claim 1.   A recording medium on which the program according to claim 13 is recorded. Determining means for determining a value corresponding to a first drive signal input at a first time point and a drive signal input at a time point earlier than the first time point;
In order to emphasize the gradation transition from the first time point to a second time point subsequent to the first time point, a second time point inputted at the second time point based on the determination result from the determining means is emphasized. A modulation means for modulating the second drive signal to generate a second drive signal corrected for supply to the pixels.   The display device according to claim 15, wherein the determined value is one of a corrected first drive signal and an uncorrected first drive signal. Storage means for storing the previous video data related to the first drive signal together with the last two video data related to the previous drive signal;
16. The display device according to claim 15, wherein the determining unit determines a value corresponding to the previous drive signal based on the stored last two-time and previous video data. Before the above, one or more frames of video data are configured from the first and second drive signals,
The determination means corrects the previous video data indicated by the first drive signal from the last two video data indicated by the previous drive signal to correct the previous video data indicated by the first drive signal. 16. The display device according to claim 15, wherein a gradation level reached by a pixel is predicted by a gradation transition to data.   The modulating means is configured to determine, based on the corrected first drive signal for obtaining the corrected second video signal, the second frame from the previous frame of the pixel indicated by the first drive signal. 19. The display device according to claim 18, wherein the video data indicated by the second drive signal is corrected so as to emphasize the gradation transition to the current frame indicated by the drive signal. The determined value is one of a corrected first drive signal and an uncorrected first drive signal,
18. The display device according to claim 17, wherein the determining unit generates the determined value according to a combination of predetermined two-time and previous video data.   The determination means corrects the previous video data indicated by the first drive signal to obtain the corrected first drive signal in the case of the predetermined combination, 21. The display device according to claim 20, wherein the first device outputs the first drive signal without correction. The predetermined combination corresponds to a correction amount to be given to the corrected first drive signal,
21. The display device according to claim 20, wherein the determination unit changes the correction amount based on at least one of a type of the image and a temperature.   23. The display according to claim 22, wherein the determination unit stops changing the correction amount when at least one of the image type and the temperature satisfies a predetermined threshold condition. apparatus. The two-time video data and the previous video data have a predetermined combination of bit widths, and the bit width is twice as large as the bit width of the current video data for the second drive signal. Is also set small,
The bit width of the video data two times before is set to be the same as or narrower than the bit width of the previous video data,
The storage means stores the video data before and after the previous video data in a bit width limited so that their bit widths become the predetermined value. 20. The display device according to 20. The first drive signal includes the previous video data, and the previous drive signal includes the video data two times before,
The above-mentioned deciding means is such that the gradation level determined based on the video data before the previous time and the previous video data falls from the gray level before the previous time when the gradation transition from the previous gray level to the previous gray level is performed. 16. The display device according to claim 15, wherein in the case, the previous video data is corrected so that the pixel has a higher gray level than a gray level predicted to be reached by the gray level transition. The first drive signal includes the previous video data, and the previous drive signal includes the video data two times before,
The determination means includes a look-up table in which the gradation of the previous video data after correction is stored in correspondence with each combination of the last two video data and the previous video data,
The bit width of the gradation of the previous video data described in the look-up table is set to a shorter one of the bit widths of the gradations of the previous and previous video data. 15. The display device according to 15. The look-up table stores the gradation of the previous video data after the correction of the predetermined combination among the combinations of the video data before and after the previous time,
The determining means interpolates the tone of the previous video data after correction stored in the look-up table to calculate the tone of the previous video data after correction corresponding to the combination of the last two times and the previous video data. The display device according to claim 26, further comprising control means for calculating. The first drive signal includes the previous video data, and the previous drive signal includes the video data two times before,
The determination means stores the gradation of the previous video data after correction for a predetermined combination among the combinations of the video data two times before and for the previous time, and stores the gradation of the previous video data for the other combinations. 16. The display device according to claim 15, further comprising a look-up table in which the gradation itself to which the video data should reach is stored. The first drive signal includes the previous video data, and the previous drive signal includes the video data two times before,
The look-up table is provided for each predetermined temperature range, and a look-up table in which the gradation of the previous video data after correction is stored, corresponding to each combination of the previous and next video data,
Control means for selecting a lookup table to be used for the correction of the previous video data from the lookup table,
16. The display device according to claim 15, wherein the control unit switches the lookup table to be selected according to a temperature.   30. The display device according to claim 29, wherein the control means switches the look-up table to be selected according to a type of the video data. The total of the bit widths of the video data of the previous time and the last two times before stored in the storage means is limited to a predetermined bit width,
30. The display device according to claim 29, wherein the control unit changes the bit width of the previous video data and the bit width of the video data two times before stored in the storage unit according to the temperature of the pixel. . The first drive signal includes the previous video data, and the previous drive signal includes the video data two times before,
The total of the bit widths of the video data of the previous time and the last two times before stored in the storage means is limited to a predetermined bit width,
16. The display device according to claim 15, wherein the bit width of the previous video data and the bit width of the video data two times before stored in the storage unit are changed according to the type of the video data. The current video data included in the second drive signal has an 8-bit width for each of the three primary colors.
The storage means stores, for each of the three primary colors, at least two of the previous and previous video data so that the total of the bit width of the video data of the previous two times and the bit width of the previous video data becomes 10 bits. 18. The display device according to claim 17, wherein the bit width of the video data is limited and stored.   18. The display device according to claim 17, wherein the pixels are liquid crystal elements of a normally black mode and a vertical alignment mode.

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