JP2012145666A - Method for driving liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve moving image blur and to reconcile improvement of image quality to video change in the screen vertical direction.SOLUTION: There is provided a liquid crystal display includes: pixel cells arranged like a matrix on a liquid crystal panel; a source line for supplying pixel signals to the pixel cells; driving means for alternately inverting polarity of the pixel signals to be supplied to the source line for every one frame to reference potential; a gate line for supplying a scan signal for supplying or stopping the pixel signals to be supplied from the source line to the pixel cells; a feature quantity determination unit which detects feature quantity of an input video signal to be determined; and a frame rate conversion unit which converts frame rate by a determination result of the feature quantity determination unit. The feature quantity determination unit determines vertical sharpness of the input video signal, the frame rate conversion unit generates the pixel signals corresponding to the respective frames of the converted frame rate, and supplies the generated pixel signals to the driving means.

Description

  The present invention relates to a liquid crystal display device of an active matrix liquid crystal display device.

  Conventionally, many liquid crystal display devices have been used as screen display devices such as computer devices, but in recent years, they are also widely used in television applications. Particularly in television applications, moving images that move quickly are often displayed, and various driving methods are used to improve moving image blur, which is a problem of liquid crystal display devices.

Hereinafter, a driving method and a driving device of a conventional liquid crystal display device will be described.
FIG. 6 is a block diagram of a driving device of a conventional liquid crystal display device. The signal conversion unit 101 inputs a synchronization signal for synchronizing the video signal and the video signal, and outputs data corresponding to each pixel to the source driver 3 in accordance with the display timing on the liquid crystal panel. At the same time, the drive synchronization signal is output to the drive pulse generator 102. The drive pulse generation unit 102 receives the drive synchronization signal and outputs a signal for controlling the source driver 3 and the gate driver 4. The source driver 3 and the gate driver 4 are drivers that drive each of the pixels arranged on the liquid crystal panel 5 in a matrix.

  FIG. 3 shows a matrix pixel arrangement and an equivalent circuit formed on the liquid crystal panel 5. As shown in FIG. 3, pixels 51 formed in a matrix on the liquid crystal panel, TFTs 52 formed for each pixel, and pixel common electrodes 53 are arranged. S1, S2,. . . SM is a source line connected to the source driver 3 and is connected to the source electrode of the TFT 52. G1, G2,. . . GN is a gate line connected to the gate driver 4 and is connected to the gate electrode of the TFT 52. A pixel capacitance (capacitor) 54 of the liquid crystal layer is sandwiched between the pixel display electrode connected to the drain electrode of the TFT 52 and the pixel common electrode 53. This includes the capacitance when an auxiliary capacitance is added. In the following description, pixels connected to the gate line Gi are referred to as i rows of pixels in the pixel matrix, and pixels connected to the source line Sj are referred to as j columns of pixels in the pixel matrix, i rows and j columns. Are referred to as pixel (i, j).

  Also, the row direction of the pixel matrix may be referred to as the horizontal direction, and the column direction may be referred to as the vertical direction. In each pixel row (j = 1 to M), red (R), green (G), and blue (B) color filters of the same color are arranged in the vertical direction as shown in the figure. (Called a stripe arrangement).

  The operation of the liquid crystal driving device configured as described above will be described. In order to write the video signal to each pixel of the liquid crystal panel 5, the signal conversion unit 101 converts the data for one row of the pixel matrix into each pixel column (R, G) according to the luminance information and color information of the video signal according to the synchronization signal. , B) are converted into data corresponding to the data and sent to the source driver. The drive pulse generator 102 also receives the drive synchronization signal from the signal converter 101. The drive pulse generation unit 102 transmits a horizontal synchronization signal (a signal indicating a timing for writing data to each row) to the source driver 3. A source signal is applied to the source lines S1 to SM at the synchronization timing. The horizontal synchronization signal is also sent to the gate driver 4, a gate line corresponding to the pixel row to which data is to be written is selected, and the gate signal is applied to the gate line at the synchronization timing.

  The gate signal is applied to the gate electrode of the pixel in the pixel row through the gate line, whereby the gate of the TFT 52 is opened, and the potential of the source line is applied to the pixel capacitance 54 of the liquid crystal layer to be charged. This charging operation is also called writing to each pixel. By repeating the above operation from i = 1 to N of the gate line at the timing of the horizontal synchronizing signal, the data of the entire screen is written in each pixel. In this way, the pixels arranged in the number of columns for each row are charged, and the pixel data for the entire screen is written by repeating the operation for the number of rows. This operation is sometimes called screen scanning, and the column direction is sometimes called the scanning direction. A period for writing the entire screen is called one frame, and the time is called a frame period. The number of times the entire screen is rewritten per second by the reciprocal of the frame period is called the frame rate.

  In general, in driving a liquid crystal panel, AC driving is performed to invert the pixel potential for each frame in order to prevent potential deviation of the liquid crystal layer, and charging is performed by switching between + polarity and -polarity for each frame (this is called Called frame inversion drive). Since the change in the transmittance of the liquid crystal layer is determined according to the absolute value of the charging potential, the same transmittance is obtained if the absolute value is the same regardless of the polarity of the charging potential. Has no effect.

  However, when the entire screen is switched between + polarity and -polarity for each frame, a slight luminance change due to the polarity change causes a phenomenon called flicker that occurs in the entire screen. Therefore, in order to prevent the occurrence of flicker, + polarity and -polarity are mixed for the entire screen during one frame period. Further, by reversing the polarity of each pixel for each frame, the luminance change due to the polarity change is dispersed and the occurrence of flicker can be suppressed. In this driving method, as shown in FIG. 3, within one frame, each column (column) of the pixel matrix has the same polarity, and adjacent columns have opposite characteristics. In addition, there is column inversion driving in which the polarity is inverted for each frame. Other than these, driving methods for preventing flicker include horizontal inversion and dot inversion.

  The light transmittance of the liquid crystal layer in each pixel changes in accordance with the charging potential (pixel potential) written in this way. On the other hand, when light is irradiated from the back surface of the liquid crystal layer with a backlight (not shown), the light passes through the liquid crystal layer according to the transmittance of each pixel and the light is colored by the color filter provided in each pixel. By mixing, a desired color image can be displayed on the whole liquid crystal panel.

  Next, changes in signals at the time of writing to each pixel will be described in detail. FIG. 7 is a timing chart when data is written to the pixel (i, j) by the source driver 3 and the gate driver 4 in the above-described operation. Changes in the horizontal synchronization signal from the previous i-1 row, the source signal in the j column, the gate signal in the i row, and the potential of the pixel (i, j) are shown with the i row as the signal writing row. The source signal in the current frame of the j column shown in FIG. 7 has a positive polarity and is assumed to be a constant potential + V in any row. The potential before writing to the pixel (i, j) is −polar potential −V written in the previous frame.

  Here, when the gate signal Gi is turned on as shown in FIG. 7, the charging of the pixel (i, j) starts from the −V potential written in the previous frame and the writing of the next row starts. Charging up to + V is completed (that is, until the next horizontal synchronizing signal comes). Thus, if the horizontal scanning period, which is an interval (= T / N) obtained by dividing the frame period (T) by the number of gate lines (N) with respect to the time required for charging, is sufficiently long, the potential of each pixel is the video. A desired value corresponding to the signal is obtained, and a correct video can be displayed.

  In the above description, it is described that the source signal and the pixel potential are inverted between the positive polarity and the negative polarity for each frame when the pixel common electrode 53 is 0 volt, that is, grounded. However, the configuration is not necessarily limited thereto. . That is, the pixel common electrode connected to the drain electrode of each pixel may be set to exactly + V, and the source signal may be switched between 0 to + V and + V to + 2 × V for each frame. At this time, since the relative voltage with respect to the potential + V of the pixel common electrode is applied to the liquid crystal layer and + polarity and −polarity are applied around the potential, the same effect as described above can be obtained.

  The normal frame period is about 16.6 ms, and the screen data is rewritten at that period. However, in the case of a fast moving image, a moving image blur occurs in which the image displayed on the liquid crystal panel is blurred as viewed from the viewer. In order to solve this, there is a method in which an interpolated frame is inserted between frames to shorten the cycle of one frame, frequently rewrite screen data, and smoothly display a moving image (see, for example, Patent Document 1).

  An example is shown in FIG. FIG. 8 is a timing chart when one frame period is set to 1/4 of the example of FIG. 7 (that is, when the frame rate is four times that of FIG. 7), except that the frame period is 1/4. This is the same as FIG.

JP 2005-268912 A

However, the conventional method for driving a video display apparatus has the following problems.
In the case of FIG. 8, when the gate signal (Gi) of the row in which data is written is turned ON, charging of the pixel potential (i, j) is started from the potential in the previous frame. However, as indicated by the solid line of the pixel potential (i, j) in FIG. 8, the desired potential level + V of the source signal Sj has not yet been reached even at the end of the frame period. This is because the frame period is shortened to ¼, and the capacitor, which is a liquid crystal layer, is insufficiently charged to complete charging.

  The reason why the voltage at the start of charging of the pixel potential (i, j) is not −V but smaller in absolute value is that it could not be completely charged up to −V in the previous frame as well. . Ideally, the change in pixel potential (i, j) in FIG. 8 should be charged from -V to + V as shown by the dashed line. However, the pixel potential becomes a solid line due to insufficient charging time for the pixel. The video displayed at this time is not a desired video and there is a problem that display quality deteriorates.

  In addition, as a means for solving the problem of insufficient charging due to shortening of the writing time, a method for eliminating insufficient charging by performing preliminary charging (also called precharging) from several lines before the gate line is disclosed. .

  FIG. 9 shows the operation timing of the preliminary charging method. In this example, the gate signal Gi is applied to the gate line from the third row before the i row (i-3 row) which is the signal write row, and charging of the pixels in the i row starts. As a result, the pixels (i, j) are charged for a total of four frames, and sufficient writing is possible.

  That is, as shown in FIG. 9, charging is started from three rows before i row, which is a signal writing row. In the section of the i-3 row, the source signal is a source signal corresponding to the video signal of the i-3 row, and this is directly added to the pixels of the i row. There is no problem if the video signal is such that the video signal does not change between the i-3 line and the i line as in the example of FIG. However, the following problems arise when displaying an image that changes rapidly in the vertical direction of the screen.

  FIG. 10 exemplifies a case where an image in which the image signal changes suddenly when the i-1 line changes to the i line is displayed. In the period from the i-3 line to the i-1 line, the result of the preliminary charging from the charging potential -V in the previous frame is not utilized, and the result is similar to charging only in the i line period. Therefore, it cannot be charged to a desired value. Thus, as shown in FIG. 11, when there is a portion where the video signal changes rapidly in the vertical direction, writing on the scanning line at the boundary is not performed correctly. That is, the input video in FIG. 11A becomes a display video as shown in FIG. 11B, and there is a problem of image quality deterioration that the outline near the boundary is blurred.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device capable of achieving both improvement in moving image resolution and prevention of blurring of an outline due to a change in image in the vertical direction due to insufficient charging. To do.

  In order to solve the above problems, a liquid crystal display device according to the present invention includes a pixel cell arranged in a matrix on a liquid crystal panel, a source line that supplies a pixel signal to the pixel cell, and the source line that supplies the source line. Driving means for alternately inverting the polarity of the pixel signal for each frame with respect to a reference potential; a gate line for supplying a scanning signal for supplying or stopping the pixel signal supplied from the source line to the pixel cell; A feature amount determination unit that detects and determines a feature amount of an input video signal; and a frame rate conversion unit that converts a frame rate based on a determination result of the feature amount determination unit. The vertical sharpness is determined, and the frame rate conversion unit generates the pixel signal corresponding to each frame of the converted frame rate, and sends the generated pixel signal to the driving unit. Characterized by feeding.

  By having such a configuration, it is possible to achieve both resolution of blurring due to insufficient charging and improvement of moving image resolution.

  The liquid crystal display device of the present invention supplies the pixel signal corresponding to the pixel cell connected to a certain source line at least when the frame rate converted by the frame rate conversion unit is a predetermined number or more. The pixel signal is supplied to the pixel cell connected to one or a plurality of source lines different from the source line.

  By having such a configuration, so-called precharging is performed to eliminate insufficient charging and prevent contour blurring.

  In the liquid crystal display device according to the aspect of the invention, when the feature amount determination unit determines that the vertical sharpness of the input video signal is lower than a predetermined value, the frame rate conversion unit sets the frame rate to a high frame rate. The frame rate conversion unit converts the frame rate into a low frame rate when it is determined that the vertical sharpness of the input video signal is higher than a predetermined value.

  By having such a configuration, an appropriate frame rate is selected according to the vertical sharpness of the displayed video, thereby achieving both the elimination of blurring due to insufficient charging and the improvement of the video resolution.

  Further, in the liquid crystal display device of the present invention, the frame rate conversion unit lowers the frame rate as the vertical sharpness increases, based on the vertical sharpness determination result of the displayed video determined by the feature amount determination unit. It is characterized by being driven like this.

  By having such a configuration, it is possible to determine the optimum frame rate by adjusting the frame rate according to the vertical sharpness of the displayed video, and to reduce the outline blur.

  In addition, the liquid crystal display device of the present invention is characterized in that the pixel cells have a stripe arrangement.

  By having such a configuration, precharging can be performed between columns of the same color, so that precharging can be realized regardless of complicated driving, and lack of charging is eliminated and contour blurring is prevented.

  The liquid crystal display device of the present invention is characterized in that the vertical sharpness of the input video signal and the amount of motion of the input video signal are detected and determined.

  By having such a configuration, the frame rate is increased / decreased by the balance between the vertical sharpness of the input video signal and the amount of motion of the input video signal, thereby improving the resolution of the moving image and reducing the outline blur due to insufficient pixel charging. .

  In the liquid crystal display device of the present invention, the feature amount determination unit determines that at least the vertical sharpness of the input video signal is higher than a predetermined value and the amount of motion of the input video signal is lower than a predetermined amount. In this case, the frame rate conversion unit converts the frame rate into a low frame rate.

  By having such a configuration, driving at a low frame rate is performed only when contour blur is truly conspicuous, thereby improving motion picture resolution and reducing contour blur due to insufficient pixel charging.

  In the liquid crystal display device according to the present invention, when it is determined that at least the amount of motion of the input video signal is larger than a predetermined amount, the frame rate conversion unit does not depend on the vertical sharpness of the input video signal. The frame rate is converted to a high frame rate.

  With this configuration, when the amount of motion of the displayed video is large, the resolution of the moving image is improved by increasing the frame rate.

  In the liquid crystal display device of the present invention, the vertical sharpness of the input video signal is based on the vertical sharpness of the input video signal determined by the feature amount determination unit and the determination result of the amount of movement of the input video signal. Is higher than a predetermined value, the frame rate conversion unit performs conversion so that the frame rate increases as the amount of motion of the input video signal increases.

  By having such a configuration, the optimum frame rate can be determined by adjusting the frame rate according to the vertical sharpness and the amount of motion of the displayed image, and the outline blurring due to the improvement of the video resolution and insufficient charging. Reduction can be realized.

  According to the liquid crystal display device of the present invention, it is possible to provide a liquid crystal display device capable of achieving both improvement in moving image resolution and prevention of blurring of the outline against a change in the vertical image due to insufficient charging.

1 is a block diagram illustrating a configuration of a liquid crystal display device according to a first embodiment. Detailed block diagram of signal conversion unit according to Embodiment 1 FIG. 5 shows a pixel arrangement configuration of the liquid crystal panel according to Embodiment 1. The figure which shows the operating conditions of the liquid crystal display device which concerns on Embodiment 2. FIG. The figure which shows the operation timing in the liquid crystal display device which concerns on Embodiment 2. FIG. Block diagram showing the configuration of a conventional liquid crystal display device The figure which shows the operation timing of the conventional liquid crystal display device The figure which shows the operation timing of the conventional liquid crystal drive device The figure which shows the operation timing of the conventional liquid crystal drive device The figure which shows the operation timing of the conventional liquid crystal drive device The figure which shows the example of an image in operation | movement of the conventional liquid crystal drive device

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same components are denoted by the same reference numerals. The following embodiment is an example embodying the present invention, and is not of a character that limits the technical scope of the present invention.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration of a liquid crystal display device according to an embodiment. In FIG. 1, the signal converter 1 and the drive pulse generator 2 are different from those in FIG. 6, and the other components are the same as those in FIG. The signal conversion unit 1 inputs a synchronization signal for synchronizing the input video signal and the input video signal, and outputs data corresponding to each pixel to the source driver 3 in accordance with the timing displayed on the liquid crystal panel. At the same time, a drive synchronization signal is output to the drive pulse generator 2. The drive pulse generator 2 receives the drive synchronization signal and outputs a signal for controlling the source driver 3 and the gate driver 4. The source driver 3 and the gate driver 4 are drivers that drive each of the pixels arranged on the liquid crystal panel 5 in a matrix.

  FIG. 2 shows a detailed configuration of the signal conversion unit 1. In FIG. 2, a feature amount determination unit 11 receives an input video signal and detects and determines the feature amount. In the present embodiment, the vertical sharpness of the input video signal is detected and determined as the feature amount. Here, the vertical sharpness is an index representing the distribution of luminance variations in the direction of the source line (scanning direction) of an image written in one frame period. In general, a monochrome image has a low vertical sharpness, and a horizontal stripe image has a high vertical sharpness.

  The frame rate conversion unit 12 receives the output of the determination result of the feature amount determination unit 11 and converts the frame rate of the input video signal. The frame rate conversion unit 12 includes a frame memory (not shown) and an interpolation image processing circuit (not shown), and stores the original input video in the frame memory. Then, the interpolated image processing circuit generates an interpolated image corresponding to the frame rate, inserts it between the original input videos, and outputs it.

  Specifically, when the frame rate is 1 × speed, the original input video is output as it is. When the frame rate is greater than 1 × speed, a video signal corresponding to the frame corresponding to the frame rate is generated by interpolating from the original input video signal. Then, the video signal generated in accordance with the frame rate is output to the source driver 3. At the same time, a drive synchronization signal corresponding to the frame rate is output to the drive pulse generator 2.

  FIG. 3 shows a matrix pixel arrangement and an equivalent circuit formed on the liquid crystal panel 5 in the first embodiment. FIG. 3 is a diagram showing a pixel arrangement structure of the liquid crystal panel according to the present embodiment. Pixels 51 are formed in a matrix on the liquid crystal panel, and a TFT 52 is formed for each pixel 51. A pixel common electrode 53 is connected to each TFT 52. The source lines (S 1, S 2,..., SM) are connected to the source driver 3 and the source electrode of the TFT 52. The gate lines (G 1, G 2,..., GN) are connected to the gate driver 4 and the gate electrode of the TFT 52. A pixel capacitance (capacitor) 54 of the liquid crystal layer is sandwiched between the pixel display electrode connected to the drain electrode of the TFT 52 and the pixel common electrode 53.

  In the present embodiment, red (R), green (G), and blue (B) color filters of the same color are formed in each pixel row (j = 1 to M) in order in the vertical direction (stripe). Array).

  In order to write the input video signal to each pixel of the liquid crystal panel 5, the signal conversion unit 1 converts the data for one row of the pixel matrix into each pixel column (R, R) according to the luminance information and color information of the video signal according to the synchronization signal. It is converted into a pixel signal corresponding to G, B) and sent to the source driver. Further, the drive pulse generation unit 2 receives the drive synchronization signal from the signal conversion unit 1, and a horizontal synchronization signal (a signal indicating the timing for writing data in each row) is sent to the source driver 3. A source signal is applied to the source lines S1 to SM at the synchronization timing. The horizontal synchronization signal is also sent to the gate driver 4, a gate line corresponding to the pixel row to which data is to be written is selected, and the gate signal is applied to the gate line at the synchronization timing.

  When the gate signal is applied to the gate electrode of the pixel in the row through the gate line, the gate of the TFT 52 is opened, and the potential of the source line is applied to the pixel capacitance 54 of the liquid crystal layer to be charged. By repeating the above operation from i = 1 to N of the gate line at the timing of the horizontal synchronization signal, the data of the entire screen is written to each pixel. In this way, the pixels arranged in the number of columns for each row are charged, and the pixel data for the entire screen is written by repeating the operation for the number of rows.

  In the present embodiment, when a source signal is applied from the source driver 3 to the source lines S1 to SM, AC driving for inverting the pixel potential with respect to the reference potential for each frame is performed. That is, frame inversion driving is performed in which charging is performed by switching between + polarity and -polarity in units of frames. Furthermore, in this embodiment, as shown in FIG. 3, each column (column) of the pixel matrix has the same polarity, and adjacent columns have opposite polarities.

  The operation of the liquid crystal display device configured as described above will be described. The feature amount determination unit 11 analyzes data for one screen included in the input video signal and detects the vertical sharpness. The feature amount determination unit 11 compares the detected vertical sharpness with a predetermined value set in advance, and outputs the comparison result to the frame rate conversion unit 12. The frame rate conversion unit 12 converts the determination result of the feature amount determination unit to a high frame rate (for example, quadruple speed) when the feature amount is lower than a predetermined value. At the same time, a drive synchronization signal is output to the drive pulse generator 2. On the other hand, when it is determined that the vertical sharpness is higher than a predetermined value, the original video is output as it is at 1 × speed or converted to a low frame rate and output.

  In this embodiment, the high frame rate is set to 4 × speed, and the low frame rate is set to 1 × speed. However, the present invention is not limited to this, and the high frame rate may be triple speed and the low frame rate may be double speed. The frame rate is relative. That is, the frame rate changes depending on the vertical sharpness of the input video signal. Then, the frame rate for images with high vertical sharpness such as horizontal stripe images is compared with the frame rate for images with low vertical sharpness such as monochrome images, and the former has a lower frame rate than the latter. In some cases, the former can be a low frame rate and the latter can be a high frame rate.

  The frame rate conversion unit 12 outputs a drive synchronization signal to the drive pulse generation unit 2. In this embodiment, pre-charging is performed when driving at a high frame rate with a frame rate of a predetermined number or more. Specifically, the drive pulse generator 2 outputs a gate driver control signal (horizontal synchronization signal and gate selection signal) to the gate driver 4 from several rows before a pixel signal corresponding to a pixel cell row on a certain gate line is input. To do. Thereby, the supply of the scanning signal to each pixel cell row in the gate line is set so as to be preceded by a period corresponding to the predetermined number of rows from the timing of supplying the pixel cell row, before the pixel cell row. The pixel cells in the pixel cell row are precharged with a pixel signal corresponding to the previous pixel cell row. This preliminary charging prevents the pixel from being blurred due to insufficient charging. The drive pulse generation unit 2 outputs a source driver control signal (horizontal synchronization signal) corresponding to the frame rate to the source driver 3.

  In addition, the drive pulse generator 2 does not perform preliminary charging when driving at a low frame rate with a frame rate of a predetermined number or less. A gate driver control signal (horizontal synchronization signal and gate control signal) is output to the gate driver 4 in order to charge only at a timing when a pixel signal corresponding to a pixel cell column on a certain gate line is input from the source line. The drive pulse generation unit 2 outputs a source driver control signal (horizontal synchronization signal) corresponding to the frame rate to the source driver 3.

  In the present embodiment, preliminary charging is performed only at a high frame rate. However, the preliminary charging may always be driven regardless of the frame rate. However, in order to eliminate contour blur due to insufficient charging, at least in the case of a high frame rate, the effect of preliminary charging can be exhibited more by performing preliminary charging.

  Further, in this embodiment, since stripe arrangement is employed and column inversion driving is performed, there is no need to perform complicated driving when performing preliminary charging, and contour blurring due to insufficient charging is prevented with an easy configuration. be able to.

  The vertical sharpness evaluation amount can be obtained by defining the maximum vertical sharpness value, the number or degree of areas with high vertical sharpness (brightness change amount), and the combination of these evaluation values. Obtainable.

  Further, in the present embodiment, the feature amount determination unit 11 distributes the frame rate between high and low by comparing the detected vertical sharpness with a predetermined value set in advance. However, the present invention is not limited to this, and a configuration may be adopted in which a more optimal frame rate is selected by switching the frame rate stepwise in accordance with the vertical sharpness determination result.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. This embodiment differs from the first embodiment in that the feature quantity determination unit 11 determines not only the vertical sharpness of the input video signal but also the amount of motion of the input video signal, and the other parts have the same configuration. Since there is, explanation is omitted.

The feature amount determination unit 11 detects and determines the amount of motion of the input video signal at the same time as detecting the vertical sharpness of the input video signal. Further, the feature amount determination unit 11 compares the vertical sharpness with a predetermined value set in advance, the amount of motion and a predetermined amount set in advance, and outputs the comparison result to the frame rate conversion unit 12. The frame rate conversion unit 12 inputs these comparison results, and when it determines that the vertical sharpness is higher than a predetermined value and the amount of motion is smaller than the predetermined amount, converts it to a low frame rate. On the other hand, in other cases, the frame rate is converted to a high frame rate.
For the detection of the motion amount, there are various methods such as the maximum value of the motion amount in the screen, the motion amount and the number of regions in the fast motion region in the screen, or the feature amount weighted by combining them. Applicable.

  In FIG. 4, the horizontal axis represents the amount of motion of the input video signal, the vertical axis represents the vertical sharpness of the input video signal, and the operating conditions of the liquid crystal display device of the present embodiment when corresponding to each of them are shown. Region A in FIG. 4, that is, when the vertical sharpness is lower than a predetermined number and the amount of motion is smaller than a predetermined amount, and when the amount of motion is larger than a certain amount regardless of the vertical sharpness, the frame rate is converted to a high frame rate. In the case of a region B in FIG. 4, that is, a video having a vertical sharpness higher than a predetermined value and a motion amount smaller than a predetermined amount, the image is driven at a low frame rate.

  In general, the degree of image quality deterioration (outline blur) at the boundary of an image with high vertical sharpness is large. On the other hand, in a video with a large amount of motion, image quality deterioration due to moving image blurring is large. Therefore, moving images larger than a predetermined amount are converted to a high frame rate, and moving image blur is prevented by displaying the video at a high frame rate. When the video has a vertical sharpness higher than a predetermined value, the video is converted to a low frame rate. Thereby, outline blurring is prevented. Even in a video with a high vertical sharpness, if the amount of motion is large, image quality deterioration at the video boundary is not noticeable. Therefore, it is preferable to convert to a high frame rate.

  A case will be described in which the driving of the preliminary charging described in the first embodiment is performed simultaneously with the driving.

  FIG. 5A shows an operation timing chart in a case where an image with low vertical sharpness is converted to a high frame rate (4 × speed) and driven. The pixel (i, j) is charged to a desired potential by preliminary charging. Each pixel can be charged to a desired potential while moving image blur is reduced by a high frame rate, and high-quality display can be performed. Further, in this case, even when the amount of motion in the area A in FIG. 4 is larger than a predetermined amount and the vertical sharpness is higher than a predetermined value, the frame is converted to a high frame rate and displayed. Therefore, even if preliminary charging is performed, charging becomes insufficient and outline blurring at the boundary portion occurs in principle. However, since the motion of the image is fast, that is, the contour moves quickly, the blurring of the contour is difficult to visually recognize, and the image quality is unlikely to deteriorate.

  On the other hand, FIG. 5B is an operation timing chart in the region B in FIG. 4 and shows a case where an image with high vertical sharpness is driven at a low frame rate (in this embodiment, 1 × speed). . The pixel (i, j) can be sufficiently charged and charged to a desired potential even without preliminary charging. As a result, even a video with a high vertical sharpness can be displayed with high image quality without blurring the outline. On the other hand, since the video is originally a small amount of motion, there is almost no moving image blur even at a low frame rate.

  According to the present embodiment, by switching the frame rate according to the amount of motion of the input video signal and the vertical sharpness of the input video signal, it is possible to perform optimum driving for the displayed video. That is, for a video with a high vertical sharpness and a small amount of motion, an image with a small outline blur due to insufficient charging can be drawn by driving at a low frame rate. On the other hand, in a video with a large amount of motion, it is possible to improve the moving image characteristics by driving at a high frame rate. Note that in the case of an image with a low vertical sharpness and a small amount of motion, there is no problem of moving image blur even if the image is displayed at a low frame rate. Moreover, the problem of insufficient charging does not occur even when the frame is displayed at a high frame rate. Accordingly, there is no problem even if the frame is displayed at any frame rate, but in the present embodiment, since the display at the high frame rate is the default, the frame rate is converted to a high frame rate.

  In the present embodiment, the feature amount determination unit 11 divides both matrices into two regions by comparing the vertical sharpness and the amount of motion with a predetermined value (amount) set in advance, and sets the frame rate. Sorted into high and low. However, it is not limited to this. For example, in the case of a video whose vertical sharpness is higher than a predetermined value, according to the determination result of the amount of motion of the input video signal, by switching so that the frame rate is gradually increased as the amount of motion increases, It may be configured to select a more optimal frame rate.

  Each of the above-described embodiments is not limited to a specific type of liquid crystal panel, but includes various types such as an IPS (In Plane Switching) method, a VA (Vertical Alignment) method, and a TN (Twisted Nematic) method. A drive system can be applied.

  The liquid crystal driving device according to the present invention has been described based on the embodiments. However, the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to the said embodiment, and the form constructed | assembled combining the component in a different embodiment is also contained in the scope of the present invention. .

  The present invention is suitable as a liquid crystal display device capable of achieving both improvement in moving image resolution and prevention of blurring due to insufficient charging.

DESCRIPTION OF SYMBOLS 1,101 Signal conversion part 2,102 Drive pulse generation part 3 Source driver 4 Gate driver 5 Liquid crystal panel 51 Pixel 52 TFT
53 pixel common electrode 54 pixel capacitance

Claims (9)

Pixel cells arranged in a matrix on a liquid crystal panel;
A source line for supplying a pixel signal to the pixel cell;
Driving means for alternately inverting the polarity of the pixel signal supplied to the source line for each frame with respect to a reference potential;
A gate line for supplying a scanning signal for supplying or stopping the pixel signal supplied from the source line to the pixel cell;
A feature amount determination unit for detecting and determining a feature amount of the input video signal;
A frame rate conversion unit that converts a frame rate based on a determination result of the feature amount determination unit,
The feature amount determination unit determines a vertical sharpness of the input video signal,
The frame rate conversion unit generates the pixel signal corresponding to each frame of the converted frame rate,
A liquid crystal display device, wherein the generated pixel signal is supplied to the driving means. When at least the frame rate converted by the frame rate conversion unit is a predetermined number or more,
The pixel signal corresponding to the pixel cell connected to a certain source line is supplied, and at the same time, the pixel signal is supplied to the pixel cell connected to one or a plurality of source lines different from the source line. Item 2. A liquid crystal display device according to item 1. The feature amount determination unit;
When it is determined that the vertical sharpness of the input video signal is lower than a predetermined value, the frame rate conversion unit converts the frame rate to a high frame rate,
3. The liquid crystal according to claim 1, wherein when it is determined that the vertical sharpness of the input video signal is higher than a predetermined value, the frame rate conversion unit converts the frame rate to a low frame rate. Display device. Based on the vertical sharpness determination result of the input video signal determined by the feature amount determination unit, the frame rate conversion unit converts the frame rate so as to decrease as the vertical sharpness increases. The liquid crystal display device according to claim 1 or 2. 5. The liquid crystal display device according to claim 2, wherein the pixel cell has a stripe arrangement. The liquid crystal display device according to claim 1, wherein the feature amount determination unit detects and determines the vertical sharpness of the input video signal and the amount of motion of the input video signal. When the feature amount determination unit determines that at least the vertical sharpness of the input video signal is higher than a predetermined value and the amount of motion of the input video signal is lower than a predetermined amount, the frame rate conversion unit 7. The liquid crystal display device according to claim 6, wherein the frame rate is converted to a low frame rate. When the feature amount determination unit determines that at least the amount of motion of the input video signal is greater than a predetermined amount, the frame rate conversion unit does not depend on the vertical sharpness of the input video signal. The liquid crystal display device according to claim 6, wherein the frame rate is converted to a high frame rate. Based on the vertical sharpness of the input video signal determined by the feature amount determination unit and the result of determination of the amount of motion of the input video signal, when the vertical sharpness of the input video signal is higher than a predetermined value, The liquid crystal display device according to claim 6, wherein the frame rate conversion unit converts the frame rate to increase as the amount of motion of the input video signal increases.