JP2003015108A - Video display device and video display method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a driving method effective for improving moving image blur of a hold-type image display device. A video display device includes a display panel having pixels arranged in a matrix and having a luminance that changes in response to a signal.
And a row driving circuit 15 connected to each row of pixels and sequentially selecting pixels on a row-by-row basis. A row driving circuit 15 connected to each column of pixels and writing a signal to the sequentially selected pixels to produce an image for one frame. Is displayed. The column drive circuit 16 includes a correction unit and a modulation unit. The correction means corrects the signal in accordance with the luminance difference between the signal written in the previous frame and the signal written in the current frame, thereby making the response of each pixel uniform. The modulating means modulates, when comparing a region with a large luminance difference with a region with a small luminance difference, an amount of correction to be applied to the signal from the large region to the small region so that the amount of correction applied to the signal is increased. Suppress blur

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and a driving method thereof. More specifically, the present invention relates to a technique for suppressing moving image blur that is typical of a so-called hold type image display device represented by an active matrix type liquid crystal display or the like.

[0002]

2. Description of the Related Art An active matrix type image display device basically comprises a display panel, a row driving circuit and a column driving circuit. The display panel includes pixels arranged in a matrix and having a luminance that changes in response to a signal. The row driving circuit is connected to each row of pixels and sequentially selects the pixels on a row-by-row basis. The column driving circuit is connected to each column of pixels and writes a signal to sequentially selected pixels to display an image for one frame. The signal written in each pixel is held for one frame and is therefore called a hold type.

[0003]

It is known that a hold-type image display device represented by an active matrix liquid crystal display or the like is different from a CRT which is a non-hold-type image display device in that so-called moving image blur is observed. ing. Causes of moving image blur include delay in response speed of liquid crystal used as an electro-optical material and visual afterimage effect. Regarding the delay of the response speed, various attempts have been made to increase the speed in terms of materials and driving. Further, so-called intermittent display has been proposed in order to deal with the visual afterimage effect.

For reference, the above intermittent display method will be briefly described. This intermittent display method is disclosed, for example, in Japanese Patent Laid-Open No. 9-325.
No. 715 is disclosed. As shown in FIG. 11, the direct-view type image display device includes a light source lamp 101 that continues to emit light at a constant brightness, a transmissive display panel 102 whose transmittance changes according to a drive signal, a shutter 103, and a drive circuit 10.
4. A pulse generation circuit 105 is provided. Display panel 1
Reference numeral 02 denotes, for example, a TFT type liquid crystal display, which converts an electrical video signal into video display light while continuing the operation of transmitting light from the light source lamp (backlight) 101 for a certain display period. It is arranged between the lamp 101 and the observer. The drive circuit 104 generates a drive signal for driving the display panel 102 according to the video signal and the synchronizing signal which are the input signals of the display panel 102, and outputs the drive signal to the display panel 102. An image is displayed by changing the transmittance of the display panel 102 according to the video signal by the drive signal and modulating the light from the light source lamp 101. The shutter 103 turns on / off the transmission of display light. As the shutter 103, for example, a polymer dispersed liquid crystal device or a ferroelectric liquid crystal device, which is not suitable for gradation display required for television display but can turn on / off light transmission at high speed, can be used. The pulse generation circuit 105 generates a shutter control pulse synchronized with the vertical synchronization of the input synchronization signal, and controls the transmission of display light through the shutter 103 by the shutter control pulse. As a result, the image display light displayed to the observer is modulated by the shutter 103 as well as the display panel 102. By using these shutter control pulses, the image display light displayed to the observer on the hold type display panel shown in FIG. 11 is 50% to 2% of the field period together with each field.
Limited to 0% of the time only. As a result, the afterimage effect of the observer is blocked and image blur is suppressed.

The response speed of the liquid crystal can be improved to some extent by taking measures from the material side and the driving side. However, simply increasing the response speed does not improve the sharpness of the moving image so much. This is because the improvement of the response speed is limited, and the response speed is finite in the end, and the problem of the visual effect for the hold type remains. Regarding the problem of visual effect, it has been proposed to blink the backlight to perform intermittent display as described above. By the intermittent display, the image quality of the moving image is improved to some extent, but the response speed cannot be corrected, so that the deterioration due to the finite response speed appears. Furthermore, since the average brightness of the screen drops according to the ratio of the blinking time of the backlight, and high-speed switching performance of the backlight is required,
There is a problem that the cost becomes high in order to obtain the desired performance.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a driving method effective for improving the moving image blur of a hold type image display device. The following measures have been taken to achieve this purpose. That is, the present invention provides a display panel including pixels arranged in a matrix and having a luminance that changes in response to a signal, and a row driving circuit connected to each row of pixels and sequentially selecting pixels on a row-by-row basis. , A column driving circuit connected to each column of pixels and writing a signal to sequentially selected pixels to display an image of one frame, wherein the column driving circuit includes a correction unit and a modulation unit. And means. The correction means corrects the signal according to the brightness difference between the signal written in the previous frame and the signal written in the current frame, and thereby makes the responsiveness of each pixel uniform. When the area with a large difference in brightness is compared with the area with a small difference in brightness, the modulation means performs modulation so that the amount of correction to be added to the signal increases from the large area to the small area, thus changing between frames. It is characterized by suppressing the blurring of the image. In some cases, the modulation means switches the amount of correction applied to the signal in a region where the difference in brightness is the smallest from a direction in which the correction is strong to a direction in which it is weak, so as to suppress noise that appears in the region where the difference in brightness is the smallest. You can or,
The display panel has a laminated structure in which plasma cells having row-shaped discharge channels and liquid crystal cells having column-shaped signal electrodes are stacked, and a pixel is provided at a portion where the discharge channels intersect with the signal electrodes. Are formed.

According to the present invention, in the hold type image display device, strong modulation is applied mainly to the luminance change in the low frequency range, or strong modulation is applied mainly to the luminance change in the middle frequency range, so that the cost is reduced. It is possible to improve the blurring of moving images.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a display panel incorporated in the image display device according to the present invention. In this embodiment, a plasma addressed liquid crystal display is used as the display panel 0. However, the present invention is not limited to this, and is applicable to various types of display panels as long as it is a hold type.
For example, it can be applied to an active matrix type liquid crystal display using TFTs.

As shown in the figure, the plasma addressed display panel 0 has a flat panel structure composed of a liquid crystal cell 1, a plasma cell 2 and a thin glass plate 3 interposed therebetween. The thin glass plate 3 is called a microsheet. The plasma cell 2 is composed of a lower glass substrate 4 bonded to a thin glass plate 3 with a frit 10.
Helium in the gap between the thin glass plate 3 and the glass substrate 4,
An ionizable gas such as neon, argon, or xenon is enclosed. Striped discharge electrodes are formed on the inner surface of the lower glass substrate 4. These discharge electrodes alternately function as the anode electrode A and the cathode electrode K. A partition wall 7 is formed on each anode electrode A, and a discharge channel X is formed by dividing a space filled with an ionizable gas. The top of the partition wall 7 is in contact with one surface of the thin glass plate 3. In the discharge channel X surrounded by the pair of barrier ribs 7, plasma discharge is generated between the anode electrode A and the cathode electrode K having opposite polarities. The thin glass plate 3 and the lower glass substrate 4 are bonded to each other by the glass frit 10 or the like as described above.

On the other hand, the liquid crystal cell 1 is constructed by using a transparent upper glass substrate 8. The glass substrate 8 is adhered to the other surface side of the thin glass plate 3 with a sealing material 6 with a predetermined gap, and a liquid crystal 9 as an electro-optical material is provided in the gap.
Is enclosed. A transparent signal electrode Y is formed on the inner surface of the upper glass substrate 8. Matrix-shaped pixels are formed at the intersections of the signal electrodes Y and the discharge channels X. Although not shown, a color filter is also provided on the inner surface of the glass substrate 8, and each pixel has, for example, RGB color filters.
Assign the three primary colors. The flat panel having such a configuration is a transmissive type, and for example, the plasma cell 2 is located on the incident side and the liquid crystal cell 1 is located on the emitting side. In this case, a backlight (not shown) is attached to the plasma cell 2 side.

FIG. 2 is a schematic diagram showing an electrode structure of the display panel 0 shown in FIG. As shown, the glass substrate 4
The anode electrodes A and the cathode electrodes K are alternately formed on the anodes, and the partition walls 7 are further formed on each anode electrode A. The region partitioned by the pair of barrier ribs 7 constitutes one discharge channel X. On the other hand, transparent signal electrodes Y are formed in stripes on a glass substrate (not shown) on the liquid crystal cell side. Discharge channel X and signal electrode Y
Pixels are formed at intersections with. In the plasma-addressed liquid crystal display panel having such a configuration, the row-shaped discharge channels X for plasma discharge are line-sequentially switched and scanned, and in synchronization with this scanning, the video signal is supplied to the column-shaped signal electrodes Y on the liquid crystal cell side. The display drive is performed by applying. When plasma discharge is generated in the discharge channel X, the inside becomes almost uniformly at the anode potential, and pixel selection is performed for each row. That is, one discharge channel X corresponds to one scanning line and functions as a sampling switch. When a video signal is applied to each signal electrode Y while the plasma sampling switch is in a conducting state, sampling is performed and it is possible to control lighting or extinction of pixels. The video signal is held in the pixel as it is even after the plasma sampling switch is turned off. The liquid crystal cell 1 modulates the incident light from the backlight into the emitted light according to the video signal and displays the video.

FIG. 3 schematically shows one pixel of the display panel shown in FIGS. When a predetermined voltage is applied between the anode electrode A and the cathode electrode K forming the discharge channel X, the gas in the discharge channel X is ionized and plasma discharge is generated. As a result, the discharge channel X becomes conductive, and the back surface of the thin glass plate 3 on the bottom surface of the liquid crystal layer 9 is virtually grounded. Here, when a signal potential is applied from the column driving circuit 16 to the signal electrode Y on the upper surface of the liquid crystal layer 9, a potential difference is generated between the upper and lower sides of the liquid crystal layer 9, and the liquid crystal layer 9 which is a capacitive component is charged. Since the thin glass plate 3 itself is an insulator, a plurality of transparent signal electrodes Y are arranged so as to be orthogonal to the discharge channel X, and when different signal potentials are applied at the time of plasma generation, after the plasma disappears, the discharge channel is discharged. X becomes non-conductive, and the signal potential written in the liquid crystal layer 9 corresponding to each pixel is held as it is.

FIG. 4 is a schematic diagram showing the overall structure of a video display device including the display panel shown in FIGS. As shown in the figure, this video display device is composed of a display panel 0, a row drive circuit 15, and a column drive circuit 16. The display panel 0 includes pixels arranged in a matrix and having a luminance that changes in response to a signal. Specifically, the display panel 0 is composed of a pair of an upper substrate 8 and a lower substrate 4, and has a flat structure in which a liquid crystal cell and a plasma cell are laminated.
FIG. 4 also includes a partially enlarged view of the display panel 0,
Matrix pixels are defined between the signal electrode on the liquid crystal cell side and the discharge electrode on the plasma cell side. The display panel 0
A backlight 13 is attached to the back side of the.
The row drive circuit 15 is a flexible printed cable (FP
C) is connected to each row of pixels of the display panel 0 via 14 and sequentially selects the pixels row by row. The scanning direction of the pixel row is, for example, from top to bottom of the display panel 0. The column drive circuit 16 is also connected to each column of pixels via a flexible printed cable (FPC) 14, and sequentially writes a signal to the selected pixels to display an image for one frame.

As a characteristic feature, the column drive circuit 16 provided separately above and below the display panel 0 includes a correction means and a modulation means. The correction means corrects the signal according to the brightness difference between the signal written in the previous frame and the signal written in the current frame, and thereby makes the responsiveness of each pixel uniform. When comparing a region having a large luminance difference and a region having a small luminance difference, the modulating unit performs modulation so that the amount of correction to be added to the signal increases from the large region to the small region, and accordingly, the image that changes between frames is changed. Control blur. In some cases, the modulation means may switch the amount of correction to be added to the signal from the direction of increasing the intensity to the direction of decreasing the intensity in the region with the smallest luminance difference, and thus suppress the noise that appears in the region with the smallest luminance difference.

With reference to FIG. 5, a specific structure of the correction means included in the above-mentioned column drive circuit will be described. The circuit configuration shown in FIG. 5 is the same as that disclosed in, for example, Japanese Patent Laid-Open No. 64-10299. As shown in FIG. 5, the column drive circuit includes a liquid crystal driver 51, a driver control circuit 52, a correction circuit 53, and a frame memory 54. Here, the correction circuit 53 and the frame memory 54 constitute the correction means described above. Correction circuit 53
Is connected to the liquid crystal driver 51, and 53c is an output side of the correction circuit 53. The output side 53c outputs the data corrected by the correction circuit 53 to the liquid crystal driver 51. The frame memory 54 is adapted to store data corresponding to the brightness of the liquid crystal immediately before the gradation change. Reference numeral 53a is an input side for inputting gradation data to the correction circuit 53, 53b is an input side for inputting the output of the frame memory 54 to the correction circuit 53, and 53d is an output side for inputting the output of the correction circuit 53 to the frame memory 54. . By combining the data stored in the frame memory 54 and the input gradation data, the correction circuit 53 converts the data.

The operation of the column drive circuit shown in FIG. 5 will be described in detail with reference to FIG. It is assumed that a certain gradation data is D, a liquid crystal applied voltage corresponding to this data is V, and a voltage of this V is applied and the state of the liquid crystal which is a gradation when it is sufficiently stable is K. If the gradation is constant K1, and the gradation data is D1, the input side 53 of the correction circuit 53
The gradation data of D1 is input to a and 53b, and the correction circuit 5
The output side 3c, 3d of 3 outputs the grayscale data of D1.

Now, as shown in FIG. 6a, the gradation data is D
In the case of changing from 1 to D2 (D1 <D2), if the correction is not performed, the voltage V2 as shown in FIG. 6b is applied to the liquid crystal. However, the liquid crystal cannot follow the change in the voltage, and the liquid crystal display operates as shown in FIG. 6c, and it takes several frames to change from K1 to K2.

Here, the applied voltage is changed from V1 to V3 (V3> V
When changing to 2), a voltage V3 (K3 state after a sufficient period of time) is applied so that the liquid crystal is K2 state after one frame, as shown in FIG. 3d. ,
After that, when the applied voltage is set to V2, the liquid crystal operates as shown in FIG. 3e and can reach a predetermined gradation K2 in one frame.

The above operation is performed by the correction circuit 53 shown in FIG.
FIG. 7 shows the change in the data on the input / output side (53a to 53d). First, the input side 53 of the correction circuit 53
The gradation data of D1 is input to a and 53b, and the correction circuit 5
The gradation data of D1 is output from the output side 53c, 53d of No. 3. When the grayscale data changes from D1 to D2 at time T1, the grayscale data input to the input side 53a of the correction circuit 53 changes to D2, but the input side 53 of the correction circuit 53 changes.
As the gradation data to be input to b, the data (data indicating the current liquid crystal state) D1 written in the frame memory 54 one frame before is read and input. The output side 53d of the correction circuit 53 predicts the state K2 of the liquid crystal after one frame, outputs the grayscale data D2 corresponding to K2, and writes it in the frame memory 54. Output side 53c of the correction circuit 53
Then, at a time T2 one frame later, a predetermined liquid crystal state K
The gradation data D3 corresponding to the voltage V3 that becomes 2 is output and input to the liquid crystal driver 51. At time T2 after one frame, the grayscale data input to the input side 53b of the correction circuit 53 also becomes D2 (that is, the liquid crystal is in the K2 state), and the output from the output side 53c of the correction circuit 53 is output. Also becomes the gradation data of D2.

FIG. 8 is a table showing the effect of the above correction. For reference, (A) represents the response speed when the above-described correction is not performed. The horizontal column of the table shows the video signal level (luminance) of the previous frame, and the vertical column shows the video signal level of the current frame. The video signal level is expressed in hexadecimal notation with 8-bit 256 gradations. For example, when the gradation data of the previous frame is 00 and the gradation data of the current frame is 3F (when the brightness difference is relatively small), the response speed is 76 ms. The previous frame is also 0
When 0 and the current frame is FF (when the brightness difference is large),
The response speed is 23 ms. In this way, if no correction is performed, the response speed of the liquid crystal greatly varies depending on the brightness difference between the previous frame and the current frame.

(B) shows the response speed when the above-mentioned correction is performed. As is apparent from the table, when the correction is performed according to the brightness difference between the previous frame and the current frame, the response speed is made uniform. For example, when the gradation data of the previous frame is 00 and the gradation data of the current frame is 3F (when the brightness difference is relatively small), the response speed is 17 ms.
Is. When the previous frame is also 00 and the current frame is FF (when the brightness difference is large), the response speed is 17 m as well.
s. Conversely, even if the brightness difference between the previous frame and the current frame is different, a predetermined correction is applied to the gradation data so as to make the response speed uniform without depending on it.

However, even if the response speed is made slightly faster and uniform by correcting the data as shown in FIG. 8B, the sharpness of the actual moving image is not dramatically improved. This is a feature of the image display device that has the hold-type property as described above. It is a method of blinking the light source (backlight) using a shutter or the like, or a black display is inserted between frames by performing high-speed driving. The method of doing is proposed. Certainly, the sharpness of the moving image is improved by using these methods. However, since the actual response speed cannot be made uniform by these methods, it is necessary to use the means for making the response speed uniform by the data correction shown in FIG. Further, when the backlight blinks or the black display is inserted, as long as the light amount of the backlight is constant, the average luminance is lowered. In order to increase the average brightness, a backlight with high light quantity is required. In addition, the backlight requires high-speed switching performance, resulting in extremely high component cost.

Therefore, when a method for improving the sharpness of a moving image is attempted without blinking the backlight by using only the above-mentioned correction circuit which is indispensable for equalizing the response speed, an actual response is obtained. It was confirmed that the sharpness of the moving image was improved more by emphasizing the luminance change in the low range where the luminance difference was smaller than the speed compensation. This result is explained as follows. That is, in an actual hold-type image display device, not only is the hold-type principle of video sharpness deterioration that can be canceled by blinking the backlight, but also the amount of luminance deterioration due to the finite response speed that actually occurs. This affects the visual brightness resolution, which further affects the sharpness of the moving image. The low-frequency enhancement processing with a small brightness difference compensates for the brightness degradation due to the finite response speed that actually occurs, so the sharpness should be relatively improved without canceling the hold effect by blinking the backlight. You can FIG. 9 shows a specific example of the emphasis coefficient as the modulation degree α. Here, the modulation degree α is a coefficient after normalizing compensation amounts of different response speeds required for each gradation, and α
= 1 is the correction amount required to make the response speed uniform.
For example, the applied voltage V3 shown in FIG. 6d is a correction amount necessary for just equalizing the response speed when α = 1. The more the modulation degree α becomes larger than 1, the more the degree is enhanced, and the level of the applied voltage V3 becomes higher due to the excessive correction. Therefore, in the graph shown in FIG. 9, when a region having a large luminance difference and a region having a small luminance difference are compared, modulation is performed so that the amount of compensation added to the gradation signal increases from the large region to the small region, As a result, blurring of the image that changes between frames is suppressed.

However, if the modulation α is increased in the low frequency range, noise will be increased. Therefore, an example in which this is improved is shown in FIG. As shown in the figure, the lowest part of the low-frequency part that contains noise is not emphasized, but the mid-range is set to the peak to improve the sharpness of the video while reducing the effect of increasing the noise. It is possible. That is, in the region with the lowest luminance, the amount of correction to be added to the gradation signal is switched from the stronger direction to the weaker direction,
Therefore, the noise appearing in the area having the smallest brightness difference is suppressed.

Although the emphasis processing in the temporal direction has been described so far, it is also possible to perform motion detection in the spatial direction and emphasize the low range in the spatial direction. By using such a method, the required memory amount is reduced,
The low-frequency modulation processing can be performed without interfering with the response speed correction processing.

[0026]

As described above, in the hold type image display device, by performing strong modulation mainly on the luminance change in the low range or by strongly modulating centering on the luminance change in the middle range, You can improve the blurring of the video at a cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a display panel incorporated in an image display device according to the present invention.

FIG. 2 is a partial perspective view of a display panel incorporated in the image display device according to the present invention.

FIG. 3 is a schematic view of one pixel of a display panel incorporated in the video display device according to the present invention.

FIG. 4 is a block diagram showing an overall configuration of a video display device according to the present invention.

5 is a block diagram showing a specific configuration of a column driving circuit included in the video display device shown in FIG.

6 is a waveform diagram provided for explaining the operation of the column drive circuit shown in FIG.

FIG. 7 is a table for explaining the operation of the column drive circuit shown in FIG.

8 is a table showing an effect of correction performed by the column driving circuit shown in FIG.

9 is a graph showing a modulation process performed by the column driving circuit shown in FIG.

10 is a graph showing a modulation process performed by the column driving circuit shown in FIG.

FIG. 11 is a schematic diagram showing an example of a conventional video display device.

[Explanation of symbols]

0 ... Display panel, 1 ... Liquid crystal cell, 2 ... Plasma cell, 3 ... Thin glass plate, 4 ... Glass substrate,
7 ... Partition wall, 8 ... Glass substrate, 9 ... Liquid crystal, 1
3 ... Backlight, 15 ... Row drive circuit, 16 ...
..Column drive circuits, A ... Anode electrodes, K ... Cathode electrodes, X ... Discharge channels, Y ... Signal electrodes

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/66 H04N 5/66 AF terms (reference) 2H093 NA16 NA31 NA41 NA51 NC11 NC28 NC34 NC42 ND06 ND07 NE01 5C006 AA01 AC01 AC18 AC21 AF50 BB18 BC11 BC16 BF02 FA18 FA29 FA54 5C058 AA06 AB05 BA01 BA35 BB13 5C080 AA10 BB05 DD01 DD09 EE19 FF10 JJ02 JJ04 JJ05 JJ06

Claims (4)

[Claims] 1. A display panel having pixels arranged in a matrix and having a luminance that changes in response to a signal, and a row driving circuit connected to each row of the pixels and sequentially selecting the pixels row by row. An image display device comprising a column drive circuit connected to each column of pixels and writing a signal to sequentially selected pixels to display an image of one frame, wherein the column drive circuit is a correction unit and a modulation unit. Comprising, the correction means, the signal is corrected in accordance with the difference in brightness between the signal written in the previous frame and the signal written in the current frame, thereby making the response of each pixel uniform, When comparing a region having a large luminance difference and a region having a small luminance difference, the modulating unit performs modulation so that the amount of correction to be added to the signal increases from the large region to the small region, thus changing the video between frames. The Bo A video display device, characterized in that to suppress. 2. The modulation means switches the amount of correction applied to the signal in a region where the luminance difference is the smallest from a direction in which the correction is strong to a direction in which it is weak, thereby suppressing noise that appears in the region where the luminance difference is the smallest. The video display device according to claim 1, wherein: 3. The display panel has a laminated structure in which plasma cells having row-shaped discharge channels and liquid crystal cells having column-shaped signal electrodes are stacked, and the discharge channels and the signal electrodes are The image display device according to claim 1, wherein pixels are formed at the intersecting portions. 4. A row driving procedure for sequentially selecting pixels on a row-by-row basis for driving a display panel having pixels arranged in a matrix and having a luminance that changes in response to a signal, and the sequentially selected pixels. In a video display method for performing a column driving procedure for writing a signal to a frame and displaying a video of one frame, the column driving procedure includes a correction procedure and a modulation procedure, and the correction procedure is written in a previous frame. The signal is corrected according to the brightness difference between the signal written in this frame and the signal written in this frame, and the responsiveness of each pixel is made uniform. When compared, the image display method is characterized in that modulation is performed so that the amount of correction applied to the signal increases from a large region to a small region, thereby suppressing image blur that changes between frames.