JP2003208138A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which harmful effect caused by an accelerated driving is more surely suppressed by conducting switching control of the accelerated driving and a normal driving based on the noise detection results that are multidimensional. <P>SOLUTION: In the liquid crystal display device, comparison is made between inputted image data that are prior to at least one vertical interval and the inputted image data of a present vertical interval and the inputted image data are converted into enhancement data based on emphasis conversion parameters obtained from the comparison result and the converted data are outputted to a liquid crystal panel 6 to conduct an accelerated driving of the panel 6. The device is provided with a noise detecting circuit 9 which detects noise included in the inputted image data and a selector 10 which selectively switch either one of the inputted image data of the present vertical interval or the enhancement data and supplies the selected data to the panel 6. <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 studies have been conducted to make the performance of LCDs as close as possible to a cathode ray tube, 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 of the current vertical period determined in advance according to the combination of the input image signal of the previous vertical period and the input image signal of the current vertical period. A liquid crystal driving method is known in which a driving voltage higher (overshot) or lower (undershot) driving voltage than a grayscale voltage for a signal 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]

In the conventional liquid crystal display device described above, the input image data of the current frame is emphasized and converted based on the gradation transition of the input image data of one frame before and after, and is supplied to the liquid crystal display panel. Therefore, when noise is superimposed on the input image signal, this noise is also subjected to emphasis conversion and supplied to the liquid crystal display panel, and the noise is emphasized and image quality deterioration such as white spots and flicker occurs. Occur.

FIG. 6 is an explanatory diagram showing a case where noise is superimposed on 3 × 3 pixel data. For example, as shown in FIG. 6A, when data of 128 gradation levels is input to all the pixels, noise as shown in FIG. When the normal driving is performed, the input gradation and the output gradation are equal to each other, so that the display data (write gradation) shown in FIG. 6B is output to the liquid crystal display panel. To be done.

On the other hand, if the data is emphasized by accelerating the drive, it works to increase the variation range of the data.
As shown in (c), the noise portion is emphasized at 140 and 135 gradation levels, and this noise is displayed conspicuously. In this way, when a weak signal source with a poor S / N ratio is input during acceleration drive, noise is further emphasized compared to normal drive, and the image quality of the displayed image deteriorates. There was a problem of letting it.

Therefore, for example, in Japanese Patent Application Laid-Open No. 3-96993, a difference signal of video signals separated by one frame period or one field period in a video signal to be displayed by a liquid crystal display device is obtained, and the difference signal When the magnitude is smaller than a predetermined value, it is regarded as noise and the input video signal is output as it is, and when the magnitude of the difference signal is larger than a predetermined value, It has been proposed to add the difference signal to an input video signal and output a video signal in a state where an afterimage is canceled.

This is a multiplier having an input / output characteristic as shown in FIG. 7, for example, a multiplier for multiplying an input signal by a predetermined coefficient,
Alternatively, it is realized by including a coefficient circuit configured using a ROM table. That is, the difference signal (motion detection signal) of the video signals supplied to the coefficient circuit and separated by one frame period or one field period is
If the size is within the range of 0 to + a and 0 to -a, that is, if it is smaller than the predetermined size | a |, the input video signal is output as it is.

Further, the difference signal (motion detection signal) supplied to the coefficient circuit is such that it is outside the range of 0 to + a and 0 to -a, that is, a predetermined magnitude |
When it is larger than a |, the output signal in the state where the input signal is multiplied by the coefficient having the same polarity as the polarity of the input signal is added to the input video signal to perform emphasis conversion on the input video signal, Cancels the afterimage of the image displayed on the liquid crystal display element.

However, the above-mentioned Japanese Patent Laid-Open No. 3-9699.
In the one described in Japanese Patent Publication No. 3, a coefficient circuit based on a multiplier or a ROM table is used for one frame period or one frame period.
Since the output video signal according to the magnitude of the difference signal between the video signals separated by the field period is obtained, only one-dimensional noise countermeasures based on temporal fluctuation can be taken, and the image quality of the displayed image is completely deteriorated. There was a problem that it was impossible to prevent.

The present invention has been made in view of the above-mentioned problems, and makes it possible to control the switching between the acceleration drive and the normal drive based on the multidimensional noise detection result, so that the adverse effects of the acceleration drive can be further reduced. A liquid crystal display device that can be reliably suppressed.

[0015]

The invention according to claim 1 of the present application is as follows.
The liquid crystal display panel compares the input image data at least one vertical period before and the input image data in the current vertical period, converts the input image data into the enhanced data based on the enhancement conversion parameter obtained from the comparison result. In the liquid crystal display device for accelerating and driving the liquid crystal display panel by outputting to the noise detection means for detecting noise included in the input image data, and based on the detection result of the noise detection means, the current vertical period It is characterized by further comprising a switching means for selectively switching one of the input image data and the emphasis data and supplying the selected image data to the liquid crystal display panel.

According to the second aspect of the present invention, the noise detecting means detects two-dimensional noise based on the correlation between pixels in the horizontal and vertical directions of the input image data. Characterize.

According to a third aspect of the present invention, the noise detecting means is based on the correlation between pixels in the horizontal and vertical directions of the input image data and the correlation between pixels in the time direction of the input image data. It is characterized in that three-dimensional noise is detected.

In the liquid crystal display device of the present invention, since either the input image data or the emphasis data can be selectively switched by the switching means and supplied to the liquid crystal display panel, a multidimensional noise detection result can be obtained. Accordingly, it is possible to switch between the acceleration drive and the normal drive, and it is possible to more surely suppress the adverse effect of the acceleration drive.

[0019]

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 4. Here, FIG. 1 is a block diagram showing a schematic configuration of a main part of the liquid crystal display device of the present embodiment, FIG. 2 is a schematic explanatory diagram showing a table content of a ROM in the liquid crystal display device of the present embodiment, and FIG. FIG. 4 is a block diagram showing a noise detection circuit in the liquid crystal display device of FIG. 4, and FIG. 4 is an explanatory diagram showing a noise detection circuit in the liquid crystal display device of the present embodiment.

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 the previous field read from FM2, and the emphasis conversion parameter corresponding to the comparison result (gradation transition) is read from the ROM1. An arithmetic unit 4 that reads out and determines / outputs emphasis data (corrected image data) is a liquid crystal that 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. The controller.

Numeral 8 is a calculator 3 for adjusting the phase of the input image data with respect to the time axis to the phase of the emphasized data.
, A noise detection circuit for detecting noise superimposed on the input image data, and a reference numeral 10 based on the noise detection result by the noise detection circuit 9. This is a selector for selectively switching one of the above and the emphasized data from the arithmetic unit 3 for each pixel and outputting it to the liquid crystal controller 4.

In the above structure, the ROM 1 stores a table storing the enhancement conversion parameters corresponding to the gradation transition of the input image data before and after one field, and the number of display signal levels, that is, the number of display data is 25 bits of 8 bits.
In the case of 6 gradations, the enhancement conversion parameters for all 256 × 256 gradation transition patterns may be included, but here, in order to reduce the memory capacity of the ROM 1,
For example, as shown in FIG. 2, it is configured using a table that stores only 9 × 9 enhancement conversion parameters (actually measured values) for nine representative gradations for every 32 gradations.

The arithmetic unit 3 reads the corresponding emphasis conversion parameter by referring to the ROM 1 in accordance with the gradation transition before and after one field, and performs an operation such as linear complementation on the emphasis conversion parameter to perform all operations. It is possible to determine the emphasis data (corrected image data) to be output to the liquid crystal controller 4 for the gradation transition of.

As described above, according to this embodiment, the selector 10 independent of the emphasis conversion processing unit is provided to selectively switch either the input image data and the emphasis data whose phases are matched with each other. Since the output is made, as will be described later, not only the one-dimensional (time-axis) noise detection result of the conventional example described above but also the multi-dimensional noise detection result is used to switch between the acceleration drive and the normal drive. It is possible to control.

That is, in the present embodiment, as the noise detection circuit 9, as shown in FIG. 3, a high-pass filter 9a for extracting high-frequency components contained in the input image data of the current field and a high-pass filter 9a are used for extraction. Non-linear processing unit 9 for performing non-linear processing on high-frequency components
By including b, noise detection is performed based on the correlation between pixels in the horizontal direction and the vertical direction on the screen of the input image data.

The non-linear processing section 9b, as shown in FIG.
Data having an amplitude level equal to or lower than the threshold value ± N is regarded as a noise component, and "1" is output at the noise superposed portion. In this way, it is possible to detect the two-dimensional spatial noise of the input image data and switch the selector 10 so that the input image data of the current field is output at the pixel portion where the noise is detected. Therefore, it is possible to reliably suppress the adverse effects due to the acceleration drive, such as white spots and flicker caused by emphasizing an unwanted noise component.

The noise detection circuit 9 detects noise based on the correlation between pixels in the horizontal and vertical directions on the screen, but this is not limited to the correlation between adjacent pixels. Noise detection may be performed based on the correlation between pixels separated by two or more. Further, it is needless to say that various circuits can be adopted as a specific circuit configuration for detecting such spatial noise, and the present invention is not limited to the above-described circuit configuration.

For example, in the case of inputting / decoding image coded data that is coded using a coding method that performs orthogonal transformation in block units composed of M × N pixels and displaying an image, Depending on the compression ratio, block distortion in which the boundaries of the processing block are visible in the flat part of the decoded image, and mosquito noise that is messy around the edges such as characters and contours, but these noises are detected. It is obvious that the image quality deterioration caused by emphasizing the block distortion or the mosquito noise may be prevented by providing the circuit configuration of (1).

Further, in the above embodiment, the ROM
1. The emphasis conversion processing unit is composed of the arithmetic unit 3,
Instead of providing the ROM 1, for example, a two-dimensional function f (pre, cur) having the gradation before transition and the gradation after transition as variables is used to obtain emphasis data for compensating the optical response characteristic of the liquid crystal display panel 6. Also good.

In the above embodiment, the image data of the previous field is compared with the image data of the current field, and the emphasis conversion parameter obtained from the comparison result is used to improve the response speed of the liquid crystal display panel 6. But
For example, it goes without saying that it is also possible to adopt a configuration in which the enhancement conversion parameter is obtained by using the image data of two fields before and three fields before.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. 5. The same parts as those of the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted. Here, FIG. 5 is a block diagram showing a noise detection circuit in the liquid crystal display device of the present embodiment.

The configuration of the liquid crystal display device of this embodiment is shown in FIG.
Further, in the above-described first embodiment, in addition to the image data of the current field, the image data of one field before from the FM2 is also input to the noise detection circuit 9, and the noise detection circuit 9 uses these image data, By performing three-dimensional noise detection and switching control of the selector 10, the adverse effect of the acceleration drive is more reliably eliminated.

That is, the noise detection circuit 9 of this embodiment
As shown in FIG. 5, in addition to the high-pass filter 9a and the non-linear processing unit 9b for performing two-dimensional spatial noise detection, the difference calculation unit 9 for performing temporal noise detection is used.
c, a comparison unit 9d, and an AND circuit 9e for taking a logical product of a spatial noise detection result and a temporal noise detection result.

The difference calculation unit 9c calculates the difference value of the image data level before and after one field, and the comparison unit 9d compares this difference value with the threshold value ± M. If the difference value is less than the threshold value ± M, This is regarded as noise and "1" is output, and it is possible to detect noise based on the correlation between pixels in the input image data in the time direction.

Incidentally, here as well, it is not limited to around one field,
It is obvious that temporal noise detection may be performed based on the difference value of the image data levels over two or more fields. Also, various circuits can be adopted as a specific circuit configuration for detecting such temporal noise.

The AND circuit 9e regards this as a noise component only when the output signal of the non-linear processing section 9b is "1" and the output signal of the comparison section 9d is also "1", and at this noise superposed portion. Outputs "1". by this,
It becomes possible to detect three-dimensional noise in the input image data, and in the pixel portion where the noise is detected, the selector 1 is set so that the input image data in the current field is output.
Since the switching control of 0 is performed, it is possible to more reliably suppress the adverse effects due to the acceleration driving, such as white spots and flicker caused by emphasizing an unwanted noise component.

As described above, in the above-described embodiment of the present invention, the image data supplied to the liquid crystal display panel 6 is changed to the input image data by the selector (switching means) 10 provided independently of the emphasis conversion section. Since it is configured to switch with the emphasized data, there is no limitation on the noise detection method, multi-dimensional noise detection of two or more dimensions is performed, and acceleration drive and normal drive are switched and controlled according to the noise detection result. Is possible. Therefore, it is possible to more surely suppress the adverse effect caused by emphasizing the unwanted noise component and prevent the deterioration of the display image.

In the above embodiment of the present invention,
The threshold values ± N and ± M used for noise determination may be fixed values that are predetermined at the time of design, or may be set to arbitrary values based on various conditions such as user instruction input and source type of input image data. The configuration may be variable.

[0039]

Since the liquid crystal display device of the present invention is configured as described above, noise included in input image data is detected, and either the input image data or the emphasis data is detected based on the detection result. Since one of them can be selectively switched to be supplied to the liquid crystal display panel, it is possible to more reliably suppress the adverse effect of the acceleration drive.

[Brief description of drawings]

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

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

FIG. 3 is a block diagram showing a noise detection circuit in the first embodiment of the liquid crystal display device of the present invention.

FIG. 4 is an explanatory diagram illustrating a noise detection circuit in the first embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a block diagram showing a noise detection circuit in a second embodiment of the liquid crystal display device of the present invention.

FIG. 6 is an explanatory diagram showing display data when noise is superimposed on input image data.

FIG. 7 is an explanatory diagram showing input / output characteristics of a residual image canceling circuit 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 8 delay circuits 9 Noise detection circuit 10 Selector

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 631 G09G 3/20 631V 632 632G 660 660U 660V H04N 5/66 102 H04N 5/66 102Z (72 ) Inventor Makoto Shiomi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture F-term (reference) within Sharp Corporation (reference) 2H093 NC28 NC29 NC49 NC52 ND06 ND10 ND32 5C006 AF13 AF45 BB11 BC16 BF01 BF14 BF24 BF26 FA14 5C058 AA06 BA14 BA14 BA35 BA14 BA35 BB21 5C080 AA10 BB05 DD06 DD08 EE26 FF09 GG12 JJ02 JJ05

Claims (3)

[Claims] 1. The input image data of at least one vertical period before and the input image data of the current vertical period are compared, and the input image data is converted into the enhanced data based on the enhancement conversion parameter obtained from the comparison result. By outputting to the liquid crystal display panel above, in a liquid crystal display device that accelerates and drives the liquid crystal display panel, a noise detection unit that detects noise included in the input image data, and based on a detection result of the noise detection unit, A liquid crystal display device comprising: switching means for selectively switching one of the input image data and the enhancement data in the current vertical period and supplying the selected image data to the liquid crystal display panel. 2. The liquid crystal display device according to claim 1, wherein the noise detection means detects noise based on a correlation between pixels in the horizontal direction and the vertical direction of the input image data. A liquid crystal display device characterized by the above. 3. The liquid crystal display device according to claim 2, wherein the noise detection unit is configured to correlate pixels in the horizontal and vertical directions of the input image data and pixels in the time direction of the input image data. A liquid crystal display device, wherein noise is detected based on the correlation between the liquid crystal display devices.