JP2003208140A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of performing smooth contour display by performing acceleration drive by data comparison between 2 fields to an interlace video signal so as to compensate the optical response characteristic of a liquid crystal display panel for suppressing the alias of an oblique contour part while suppressing the occurrence of an after image and tailing. <P>SOLUTION: The device is provided with an image memory 2 for holding image data preceding by at least 2 fields, and an arithmetic unit 3 which compares the image data preceding by at least 2 fields held in the image memory 2 with image data of a present field and converts inputted image data to enhancement data on the basis of enhancement converting parameter obtained from comparing result. By outputting the enhancement data obtained by the arithmetic unit 3 to the liquid crystal display panel as displayed image data, the panel 5 is accelerately driven. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for displaying an image using a liquid crystal display panel, and more particularly to an acceleration driving method capable of improving the response speed of the liquid crystal display panel.

[0002]

2. Description of the Related Art In recent image display devices, a liquid crystal display device (LCD) has been widely used instead of a cathode ray tube (CRT) for both PC and TV.
An LCD applies an electric field to a liquid crystal layer having an anisotropic dielectric constant that is injected between two substrates, and controls the intensity of the electric field to control the amount of light transmitted through the substrates. A display device for obtaining an image signal.

At present, various researches have been conducted to make the performance of LCDs as close as possible to that of cathode ray tubes, and one of them is to improve the response speed of liquid crystals. Various attempts have been made to speed up the response speed of the liquid crystal, such as optimizing the liquid crystal material and reducing the thickness (cell gap) of the liquid crystal cell, but on the other hand, the driving method is independent of the performance of the liquid crystal itself. Studies have been conducted to improve the response speed by devising the.

In order to improve the problem of the response speed of the liquid crystal, the input image data of the current field, which is predetermined according to the combination of the input image data of the previous field and the input image data of the current field, is used. A liquid crystal driving method is known in which a driving voltage higher (overshot) or lower (undershooted) than the gradation voltage is supplied to a liquid crystal display panel. Hereinafter, in this specification, this driving method is defined as acceleration driving.

For example, in Japanese Patent Laid-Open No. 4-365094, an image memory for storing one frame of display digital image data, two inputs of the digital image data and image data read from the image memory with a delay of one frame are input. R storing a table storing image data corresponding to
When the image data changes, the optimum image data stored in advance according to the direction and degree of the change is read out and the liquid crystal panel is driven, so that the light transmittance rises or rises. It has been proposed to make the fall steep in a necessary and sufficient range to improve the response speed of the liquid crystal.

Generally, in a liquid crystal display panel, it takes a long time to change from one halftone to another halftone, the halftone cannot be displayed within one field (about 16.6 msec), and an afterimage is generated. There is a problem that not only the generated halftone but also the halftone cannot be correctly displayed, but by using the above-described acceleration drive, the target halftone can be displayed in a short time.

[0007]

[Patent Document] Japanese Unexamined Patent Publication No. 4-365094

[0008]

By the way, as a method of displaying an image in a liquid crystal display device, a method called line doubler is often adopted for interlace scanning of a cathode ray tube. This is a pseudo interlace scanning method in which an interlace video signal sent from the broadcasting station is not subjected to IP conversion processing and a signal for one horizontal period is written in two lines of a liquid crystal display panel. Is.

However, when the acceleration drive (enhancement drive) based on the comparison between the image data of the previous field and the image data of the current field is applied to this line doubler processing, the diagonal lines appear as jagged jaggies. There is a problem that it will end up.

This problem will be described in detail with reference to FIGS. 11 to 15. FIG. 11 shows original image data of a still image in which an oblique contour exists in the image (the shaded portion is displayed in black, and the one-sided diagonal portion is displayed in gray). FIG. 12 is a schematic explanatory view showing a mechanism for displaying an original image using the line doubler method. By displaying two lines of each of the odd field and the even field in FIG.
A frame image is displayed (the shaded areas are gray shades between the shaded areas and the shaded areas).

Next, in order to compensate the response speed of the liquid crystal, 1
Generate emphasis data by comparing the data between fields,
The case of accelerating the liquid crystal display panel will be described.
FIG. 13 is a schematic explanatory diagram showing image data when the current field is an odd field, and the odd field (current field) of the odd field (current field) is changed according to the gradation transition of the odd field (current field) with respect to the even field (one field before). The image data is subjected to emphasis conversion, and a brighter part (white display) than the surroundings appears.

Similarly, FIG. 14 is a schematic explanatory view showing the image data when the current field is an even field, and the even number is displayed in accordance with the gradation transition of the even field (current field) with respect to the odd field (one field before). Emphasis conversion is applied to the image data of the field (current field),
A darker part (black display) than the surroundings appears.

When line doubler processing is performed on the image data that has been subjected to the emphasis conversion as described above to display an image of an odd field and an even field of two lines at a time, as shown in FIG. Since a false signal that is whitened and blackened is generated and a one-frame image in which jaggies (bright / dark steps) are emphasized is displayed, there is a problem that the image quality of the display image is deteriorated.

The present invention has been made in view of the above-mentioned problems, and compensates the optical response characteristics of a liquid crystal display panel by performing acceleration drive by data comparison between two fields on an interlaced video signal. Provided is a liquid crystal display device capable of performing smooth contour display while suppressing generation of afterimages and trailing while suppressing generation of false signals in oblique contour portions.

[0015]

The invention according to claim 1 of the present application is as follows.
In a liquid crystal display device for displaying an image using a liquid crystal display panel, an image memory holding at least image data of two fields before, an image data of two fields before and image data of the current field held in the image memory, A liquid crystal display panel, wherein the liquid crystal display panel is provided with calculation means for performing comparison and converting input image data into emphasis data based on an emphasis conversion parameter obtained from the comparison result, and the emphasis data obtained by the calculation means as display image data. Is output to accelerate the liquid crystal display panel.

According to the invention of claim 2 of the present application, line doubler processing is performed on the emphasized data to display an image of odd fields and even fields by two lines each.
It is characterized by displaying a frame image.

According to the invention of claim 3 of the present application, further, the scene change detecting means for detecting a scene change of the input image data, and the input image data and the emphasized data are selected based on a detection result of the scene change. Switching means for selectively switching and outputting to the liquid crystal display panel.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the present invention will be described below.
A detailed description will be given with reference to FIGS. 1 to 8. Here, FIG. 1 is a block diagram showing a schematic configuration of the liquid crystal display device of the present embodiment, and FIG. 2 is an RO in the liquid crystal display device of the present embodiment.
FIG. 3 is a schematic explanatory view showing the table contents of M, FIG. 3 is a schematic explanatory view showing image data when the current field in the liquid crystal display device of this embodiment is an odd field, and FIG. 4 is a current field in the liquid crystal display device of this embodiment. FIG. 6 is a schematic explanatory diagram showing image data when is an even field.

FIG. 5 is a schematic explanatory diagram showing one frame image in the liquid crystal display device of the present embodiment, and FIG. 6 is a schematic explanatory diagram showing one frame image in the liquid crystal display device of the present embodiment when the line doubler method is not used. FIG. 7 is a schematic explanatory view showing the relationship between the applied voltage and the transmittance in the liquid crystal display device of the present embodiment, and FIG. 8 is a conceptual explanatory diagram showing the display screen by the acceleration drive at the scene change in the liquid crystal display device of the present embodiment. is there.

In FIG. 1, reference numeral 1 denotes an RO which stores enhancement conversion parameters according to gradation changes of input image data.
M, 2 are a frame memory (FM), 3 is a comparison between the image data of the current field and the image data of two fields before read from FM2, and the emphasis conversion parameter corresponding to the comparison result (gradation transition) is stored in ROM1. The arithmetic unit 4 which reads out from the arithmetic unit 3 and determines / outputs emphasis data (corrected image data) outputs a liquid crystal drive signal to the gate driver 6 and the source driver 7 of the liquid crystal panel 5 based on the emphasis data from the arithmetic unit 3. LCD controller.

The FM2, which is an image memory, is a memory capable of holding image data of at least two fields. Further, the input image data is an interlace signal such as an RGB signal or a YUV signal, and here, an R signal of 8
This will be described as bit data. Further, the liquid crystal controller 4 transfers data for two lines in one horizontal period to the liquid crystal panel 5.
By controlling the gate driver 6 to write to
A line doubler image display is realized.

Further, in the above configuration, the ROM 1
Stores a table storing enhancement conversion parameters corresponding to gradation transitions of input image data before and after two fields, and the number of display signal levels, that is, the number of display data is 8
In the case of 256 gradations of bits, there may be an emphasis conversion parameter for all 256 × 256 gradation transition patterns, but here, in order to reduce the memory capacity of the ROM 1, for example, as shown in FIG. , Every 32 gradations
It is configured by using a table that stores only the 9 × 9 enhancement conversion parameters (measured values) for one representative gradation.

The arithmetic unit 3 responds to the R transition in accordance with the gradation transition between the image data of two fields before and the image data of the current field.
By referring to OM1, the corresponding enhancement conversion parameter is read out, and by performing an operation such as linear complementation on this enhancement conversion parameter, the enhancement data (correction image data) to be output to the liquid crystal controller 4 for all gradation transitions. ) Can be determined.

As described above, in the liquid crystal display device of the present embodiment, the acceleration drive for comparing the image data of two fields before and the image data of the current field and determining the emphasis data based on the comparison result is performed. Since it has been performed, as shown in FIGS. 3 and 4, no false signal in which the white and black portions are formed in the oblique contour portion is generated. Further, when the line doubler process is performed on the emphasized data to display the data of each field by two lines, it is possible to display the contour diagonal line without jaggies (bright and dark steps) as shown in FIG. Becomes

In the first embodiment of the present invention described above, the image display of the line doubler system is performed on the image data of each field. However, when the line doubler system is not used, one frame as shown in FIG. Images can be obtained. In this case, the vertical image size is 1 /
Since it becomes 2, processing such as thinning out pixel data in the horizontal direction is required, but it is effective for a liquid crystal panel having a small screen size.

Further, the relationship between the applied voltage and the transmittance of the liquid crystal panel 4 will be described with reference to FIG. here,
A case will be described in which, using a normally black mode liquid crystal panel, continuous black screen data as an input image suddenly changes to halftone data (for example, 128). Normally, in a normally black mode liquid crystal panel, the higher the applied voltage is, the higher the gray scale can be displayed,
That is, the higher the applied voltage, the whiter the screen.

In FIG. 7, the broken line at the bottom shows the transition of the transmittance when the normal driving is performed without the acceleration driving, and the two fields (one field is about 16.6 m).
The target transmittance is reached by applying s). On the contrary,
When the acceleration drive based on the comparison with the data one field before is performed, it can be seen that the target transmittance is achieved within one field as shown by the chain double-dashed line in FIG.

Next, when the acceleration drive based on the comparison with the data two fields before is performed, the data is emphasized from black to halftone over two fields after the change to the halftone screen. 7 As indicated by the thick solid line,
In the second field after the change to the halftone, the transmittance becomes too high, and as a result, a white screen appears for the moment when the change to the halftone occurs.

That is, when the acceleration drive is performed based on the comparison between the two-field previous data and the current field data as in the present embodiment, the jaggies are prevented from occurring while suppressing the afterimage and the tailing. Although it is possible to display a smooth contour, as shown in FIG. 8, since the highlighting process is performed over two fields at the time of scene change, the data is overemphasized and blinks white like flicker. Such a phenomenon may occur.

A device for preventing such a phenomenon will be described below with reference to FIGS. 9 and 10 as a second embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Is omitted. Here, FIG. 9 is a block diagram showing a schematic configuration of a main part of the liquid crystal display device of the present embodiment,
FIG. 10 is a block diagram showing a configuration example of the scene change detection unit in the liquid crystal display device of this embodiment.

In FIG. 9, 11 is a scene change detection circuit for detecting the scene change point of the input image, and 12 is the input of the current field based on the scene change detection result (switch control signal) by the scene change detection circuit 11. This is a selector that selectively switches either one of the image data and the emphasis data from the arithmetic unit 3 in field units and outputs it to the liquid crystal controller 4.

That is, in the present embodiment, in order to prevent the second field from the scene turning point being overemphasized and blinking white, the scene changing point detected by the scene change detection circuit 11 is changed to the second field. In other words, the selector 12 is switch-controlled so that the input image data is output as it is as the display image data.

In the above structure, the scene change detection circuit 11 generates the timing data corresponding to a predetermined screen position based on, for example, the horizontal synchronizing signal and the vertical synchronizing signal, and the predetermined timing generating circuit 21 according to the timing data. And flip-flops 22 and 23 for latching pixel data corresponding to the screen position. Here, the data held in the flip-flops 22 and 23 has a relation of pixel data at corresponding screen positions before and after one field.

A difference calculation circuit 24 for calculating the difference value of the data held in the flip-flops 22 and 23.
And a comparison circuit 25 for comparing the difference value with a scene conversion determination threshold value, and a delay circuit 26 for delaying the comparison result, that is, the scene conversion determination result by one field and outputting the delayed result to the selector 12. Accordingly, when the difference value of the pixel data at the same screen position in one field is larger than a predetermined threshold value, a determination result that the current field is the scene conversion field is obtained, and the field next to the scene conversion field is obtained. , The selector 12 is switched and controlled, the input image data is selected, and the liquid crystal controller 4 is selected.
Can be output to.

The structure of the scene change detection circuit 11 is not limited to that described above, and various circuit structures such as one based on a change (difference) in screen average luminance for one field may be adopted. Needless to say.

As described above, according to the liquid crystal display device of the present embodiment, the acceleration drive based on the comparison between the two fields is stopped (turned off) and switched to the normal drive according to the scene change detection result. Therefore, it is possible to prevent a phenomenon such as flicker that blinks in white due to over-enhancement of data, which occurs at a scene turning point, and high-quality image display can be realized.

[0037]

Since the liquid crystal display device of the present invention is configured as described above, the image data of two fields before and the image data of the current field are compared, and the input image data is obtained based on the comparison result. Since it is converted into emphasis data and supplied to the liquid crystal display panel, it is possible to suppress the occurrence of afterimages and tailing, suppress the generation of false signals in the oblique contour portion, and perform smooth contour display. Therefore, high quality image display can be realized.

Further, the scene change of the input image is detected, and the input image data and the emphasis data are selectively switched based on the detected result of the scene change to be supplied to the liquid crystal display panel. It is possible to prevent the adverse effect of acceleration drive (deterioration of image quality due to over-enhancement) that occurs based on the comparison between two fields, and to realize high-quality image display.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration in a first embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic explanatory diagram showing an example of table contents of a ROM 1 in the first embodiment of the liquid crystal display device of the present invention.

FIG. 3 is a schematic explanatory diagram showing image data when the current field is an odd field in the first embodiment of the liquid crystal display device of the present invention.

FIG. 4 is a schematic explanatory diagram showing image data when the current field is an even field in the first embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a schematic explanatory diagram showing one frame image in the first embodiment of the liquid crystal display device of the present invention.

FIG. 6 is a schematic explanatory view showing one frame image when the line doubler method is not used in the first embodiment of the liquid crystal display device of the present invention.

FIG. 7 is a schematic explanatory diagram showing the relationship between applied voltage and transmittance in the first embodiment of the liquid crystal display device of the present invention.

FIG. 8 is a block diagram showing a conceptual explanatory view showing a display screen by acceleration driving at the time of scene change in the first embodiment of the liquid crystal display device of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a main part in a second embodiment of a liquid crystal display device of the present invention.

FIG. 10 is a block diagram showing a configuration example of a scene change detection unit in the second embodiment of the liquid crystal display device of the present invention.

FIG. 11 is a partial schematic diagram of an interlaced input image including an oblique contour.

FIG. 12 is a schematic explanatory view showing a mechanism of displaying an original image using a line doubler method.

FIG. 13 is a schematic explanatory view showing image data when the current field is an odd field in the conventional liquid crystal display device.

FIG. 14 is a schematic explanatory diagram showing image data when a current field is an even field in a conventional liquid crystal display device.

FIG. 15 is a schematic explanatory diagram showing one frame image in a conventional liquid crystal display device.

[Explanation of symbols]

1 ROM 2 frame memory 3 calculator 4 LCD controller 5 LCD panel 6 gate driver 7 Source driver 11 Scene change detection circuit 12 selector 21 Timing creation circuit 22 flip-flops 23 flip-flops 24 Difference calculation circuit 25 Comparison circuit 26 Delay circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 622 G09G 3/20 622N 631 631B 641 641R 650 650E 660 660V (72) Inventor Shiomi Makoto Osaka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Ltd. (72) Inventor Takashi Yoshii 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture F-term (reference) 2H093 ND10 ND12 ND15 ND32 ND34 ND58 5C006 AA01 AA16 AB03 AC29 AF03 AF04 AF11 AF42 AF44 AF45 AF46 AF51 AF53 AF84 BB11 BC03 BC12 BC22 BF02 BF06 BF07 BF08 BF14 BF24 BF28 FA14 FA18 FA29 FA44 FA56 5C080 AA10 BB05 DD02 DD07 DD22 EE19 EE29 FF09 GG08 GG15 GG17 JJ01 JJ02 JJ03 JJ04 JJ05 KK43

Claims (3)

[Claims] 1. A liquid crystal display device for displaying an image using a liquid crystal display panel, comprising: an image memory for holding image data of at least two fields before; and image data for two fields before and current field held in the image memory. Of the image data of the display image data based on the emphasis conversion parameter obtained from the comparison result, and the input image data is converted into the emphasis data. By outputting to the liquid crystal display panel as
A liquid crystal display device, wherein the liquid crystal display panel is accelerated and driven. 2. The liquid crystal display device according to claim 1, wherein a line doubler process is performed on the emphasized data to display an image of an odd field and an image of an even field by two lines to display one frame image. A liquid crystal display device characterized by the above. 3. The liquid crystal display device according to claim 1, wherein a scene change detection unit that detects a scene change of the input image data, and the input image data based on a detection result of the scene change. A liquid crystal display device comprising: switching means for selectively switching the emphasized data and outputting to the liquid crystal display panel.