JP3500145B1 - Liquid crystal display - Google Patents

Abstract

Provided is a liquid crystal display device capable of removing an adverse effect of acceleration driving by detecting an edge portion of an input image and controlling ON / OFF of acceleration driving for each pixel. SOLUTION: This liquid crystal display device displays an image using the liquid crystal display panel 4, and changes an optical response characteristic of the liquid crystal display panel 4 according to a gradation transition of input image data before and after at least one vertical period. A computing unit 2 for obtaining enhanced data to be compensated, an edge detector 6 for detecting an edge portion included in the input image data, and any one of the enhanced data and the input image data based on a detection result of the edge portion. And a selector 7 for selectively switching one of them in units of pixels and supplying it to the liquid crystal display panel 4 as display image data.

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 that displays an image using a liquid crystal display panel, and more particularly to a liquid crystal display device that performs acceleration driving to improve 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.

FIG. 8 shows a schematic configuration of such a conventional general acceleration drive circuit. In FIG. 8, reference numeral 1 is a ROM in which emphasis conversion parameters corresponding to combinations of gradation transitions before and after one vertical period of input image data, which are digital signals such as RGB signals and YUV signals, are stored, and 2 is the emphasis conversion parameters. An arithmetic unit for obtaining corrected image data (emphasized data) for compensating the liquid crystal response characteristic by using 3 is a frame memory (hereinafter abbreviated as FM) capable of holding at least one field of image data, and 4 is display image data. It is a liquid crystal panel that is accelerated by being supplied with the corrected image data to display an image.

In the table stored in the ROM 1, for example, the number of display signal levels, that is, the number of display data is 8.
In the case of 256 gradations of bits, correction image data for all 256 gradations may be stored. For example, as shown in FIG. 9, enhancement conversion parameters for 9 representative gradations for every 32 gradations. Only (measured value) is stored,
The corrected image data (enhancement data) for other gradation transitions may be obtained from the above-mentioned emphasis conversion parameter (actual measurement value) by calculation such as linear interpolation.

Generally, in the liquid crystal panel 4, 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 halftones but also the halftones cannot be displayed correctly. However, by using the above-mentioned acceleration drive, the optical response characteristics of the liquid crystal panel 4 are compensated, and the target halftones can be displayed in a short time. Can be displayed with.

[0009]

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

[0010]

As described above, in the conventional liquid crystal display device, the acceleration driving is performed by comparing the input image data of one field before and the image data of the current field and outputting the emphasis data. However, if the optimization of the emphasis data is wrong, the error of the inter-field data will be expanded, and the video noise which is not in the original input data will be created.

FIGS. 10 and 11 are explanatory diagrams showing the relationship between the applied voltage to the liquid crystal panel and the transmittance when the input image data changes from black to a certain halftone value. In FIG. 10, since the emphasis data is optimized according to the characteristics of the liquid crystal panel, it takes three fields to reach the target brightness when the normal driving is performed, whereas the acceleration driving is performed. This makes it possible to reach within one field. On the other hand, in FIG. 11, since the emphasis data used is too strong, the brightness equal to or higher than the target brightness is output.

Here, in the images shown in FIGS. 10 and 11, it is assumed that the input image data changes from black to a certain halftone value and remains halftone thereafter, so that the error in the output data is Although it has been absorbed in one field and has reached the target reaching luminance, for example, when data in which black → halftone → black → halftone is repeated is input, the error of the output data increases undesirably.

When this is replaced with a normal TV reception signal, as a result, the edge portion such as the contour of a face or the contour of a character is
There is a problem in that an unnatural image (so-called noise) is output and output, which causes image quality deterioration such as unnatural coloring, white spots, and flicker.

Considering the response speed of the liquid crystal panel itself, it is difficult to always output optimum emphasis data due to variations in cell gap, changes in viscosity of the liquid crystal material due to environmental temperature, and the like.

The present invention has been made in view of the above problems, and eliminates the adverse effect of acceleration drive by detecting the edge portion of an input image and controlling ON / OFF of acceleration drive for each pixel. A liquid crystal display device capable of

[0016]

The invention according to claim 1 of the present application is as follows.
A liquid crystal display device for displaying an image using a liquid crystal display panel, wherein enhanced data for compensating for optical response characteristics of the liquid crystal display panel is obtained according to a gradation transition of input image data at least before and after one vertical period. Means, edge detection means for detecting an edge portion included in the input image data, and based on a detection result of the edge portion, one of the emphasized data and the input image data is selectively selected on a pixel-by-pixel basis. Switching means for switching and supplying as display image data to the liquid crystal display panel is provided.

According to a second aspect of the present invention, a subtracter for subtracting the input image data from the emphasized data, and a weighting factor k variably controlled based on a detection result of the edge portion.
Is added to the output data of the subtractor, and an adder that determines the display image data by adding the output data of the multiplier to the input image data. To do.

The invention of claim 3 of the present application stores a conversion table memory storing an emphasis conversion parameter for converting the input image data into the emphasis data, and a non-conversion parameter for outputting the input image data as it is. The conversion table memory and the non-conversion table memory are selectively switched based on the detection result of the edge portion to determine the display image data. Characterize.

The invention of claim 4 of the present application is provided with a table memory which stores an emphasis conversion parameter for converting the input image data into the emphasis data and a non-conversion parameter for outputting the input image data as it is. , The display image data by selectively switching and referring to a reference table area in which the enhancement conversion parameter is stored and a reference table area in which the non-conversion parameter is stored based on the detection result of the edge portion. It is characterized by determining.

As described above, the liquid crystal display device of the present invention detects the edge portion of the input image, turns off the acceleration drive for the pixel determined to be the edge portion, and displays the unconverted input image data. Since the image data is output to the liquid crystal display panel, it is possible to suppress the image quality deterioration due to the adverse effect of the acceleration drive and realize a high quality image display.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a liquid crystal display device according to the present invention will be described in detail below with reference to FIGS. 1 and 2. The same parts as those of the conventional example described above are designated by the same reference numerals, and The description is omitted. Here, FIG. 1 is a block diagram showing a schematic configuration in the liquid crystal display device of the present embodiment, and FIG. 2 is a block diagram showing an edge detection circuit in the liquid crystal display device of the present embodiment.

In the liquid crystal display device of this embodiment, as shown in FIG. 1, in order to match the phase of the input image data with respect to the time axis to the phase of the emphasized data, the delay circuit 5 for compensating the calculation processing time by the calculator 2 is provided. An edge detection circuit 6 for detecting an edge portion included in the input image data, and based on the edge detection result by the edge detection circuit 6, the input image data of the current field and the emphasis data from the arithmetic unit 2 Selectively switch one of them in pixel units,
A selector 7 that outputs the display image data to the liquid crystal panel 4 is provided.

The arithmetic unit 2 compares the image data of the current field with the image data of one field before which is output from the FM3, reads out the emphasis conversion parameter corresponding to the combination of gradation transitions of both data from the ROM 1, By performing an operation such as linear complementation on the emphasis conversion parameter, emphasis data (corrected image data) to be output to the liquid crystal panel 4 for all gradation transitions is determined.

A configuration example of the edge detection circuit 6 will be described with reference to FIG. Although the input image data is described as 8-bit data of the R signal here, it is needless to say that it is not limited to this. The input image data is an 8-bit flip-flop (hereinafter, FF
11, and a flip-flop (hereinafter, F)
L is abbreviated as F). Here, FF
A shift register is composed of two blocks of 11 and FF12.

Therefore, the data held in the FF 11 and the data held in the FF 12 have a relation of adjacent pixel data. The data held in FF11 and FF12 is input to the subtractor 13, and the difference value between adjacent pixels is input to the comparator 14. The comparator 14 compares it with comparison reference data for verifying whether the output of the subtractor 13 is an edge, and outputs the comparison result to the selector 7 as an edge detection result.

With this, it is possible to detect whether or not the current input pixel data is at the edge portion, and according to the detection result, the selector 7 causes the input image data of the current field from the delay circuit 5 and the arithmetic unit 2 to operate. It is possible to selectively switch one of the emphasized data and the emphasizing data and supply it to the liquid crystal panel 4. That is, when the data of “1” indicating the presence of the edge detection is input as the edge detection result, the selector 7 outputs the input image data of the current field which is not subjected to the emphasis conversion as the pixel data to the liquid crystal panel 4 as it is. To do.

As described above, according to the liquid crystal display device of the present embodiment, with respect to the pixel portion determined to be the edge image, the switching control is performed so that the acceleration drive is turned off and the normal drive is performed. It is possible to realize the high-quality image display by removing the adverse effects caused by the accelerated driving such as unnatural coloring, white spots, and flicker that occur in the part.

In the first embodiment, the ROM
1 and the arithmetic unit 2 constitute the writing gradation determining means,
Instead of providing the ROM 1, for example, corrected image data (enhancement data) for compensating the optical response characteristic of the liquid crystal panel 4 by a two-dimensional function f (pre, cur) having the gradation before transition and the gradation after transition as variables. ) The configuration may be such that a signal is obtained.

Next, a second embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. 3. The same parts as those of the first embodiment will be designated by the same reference numerals and the description thereof will be omitted. Here, FIG. 3 is a block diagram showing a schematic configuration of a main part of the liquid crystal display device of the present embodiment.

In the liquid crystal display device of this embodiment, instead of providing the selector 7 in the first embodiment, as shown in FIG. 3, input image data is obtained from the corrected image data (emphasized data) obtained by the calculator 2. By subtracting the subtracter 8 for subtraction, the multiplier 9 for multiplying the output data of the subtractor 8 by the weighting coefficient k (0 ≦ k ≦ 1), and adding the output data of the multiplier 21 to the input image data, An adder 10 for obtaining display image data is provided.

Here, the weighting coefficient k in the multiplier 9 is
It is changed based on the edge detection result by the edge detection circuit 6. That is, when the data of “0” indicating that the edge detection result indicates no edge detection is input, the weighting factor k =
The emphasis data is output to the liquid crystal panel 4 as 1. On the other hand, when the data “1” indicating the presence of the edge detection is input, the weighting coefficient k = 0 is set and the input image data is directly displayed on the liquid crystal panel 4 as the display image data without performing the emphasis conversion. Output.

As described above, also in the present embodiment, the pixel portion determined to be the edge image is switched and controlled so that the acceleration drive is turned off and the normal drive is performed. It is possible to realize the high-quality image display by removing the adverse effects of accelerated driving such as various coloring, whitening, and flicker. Also, by changing the value of the weighting factor k, it is possible to control the image display data more flexibly.

Next, a liquid crystal display device according to a third embodiment of the present invention will be described with reference to FIGS. 4 to 7. The same parts as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted. . Here, FIG. 4 is a block diagram showing a schematic configuration of the liquid crystal display device of the present embodiment, FIG. 5 is an explanatory view showing the contents of the ROM non-conversion table in the liquid crystal display device of the present embodiment, and FIG. FIG. 7 is a block diagram showing an edge detection circuit in the liquid crystal display device, and FIG. 7 is an explanatory diagram showing another ROM configuration in the liquid crystal display device of the present embodiment.

In the liquid crystal display device of this embodiment, as shown in FIG. 4, the RO in which the emphasis conversion parameter is stored is used.
In addition to M1 (conversion table memory), a ROM 21 (non-conversion table memory) storing non-conversion parameters (that is, the through table shown in FIG. 5) is provided, and the ROM is detected based on the edge detection result by the edge detection circuit 16.
By selectively referring to either 1 or the ROM 21, it is possible to control switching between acceleration drive and normal drive in pixel units.

Here, the edge detection circuit 16 of the present embodiment.
Is, as shown in FIG. 6, FF11 and FF12 for 8 bits that latch the input image data (8-bit data),
Subtractor 13 that subtracts the data held in FF11 and FF12 to obtain the difference value between adjacent pixels, and subtracter 1
In addition to the comparator 14 for comparing the difference value between the adjacent pixels obtained in 3 and the comparison reference data, the comparison result (1 bit) in the comparator 14 is added to the 8-bit pixel data from the FF 12 to obtain 9 bits. There is provided a flip-flop (FF) 15 which creates and outputs the data.

For example, from FF12, "00 ... 0011"
8 bits of data are input, and when the data of “1” indicating that edge detection is present is input from the comparator 14,
In the FF15, “1” + “00 ... 0011” is set as “10”.
9-bit data of 0 ... 0011 "is output to the arithmetic unit 2. On the other hand, when data of" 0 "indicating no edge detection is input," 0 "+" 00 ... 0011 "is set to" 0 ".
The 9-bit data "00 ... 0011" is output to the calculator 2.

The operator 2 can determine whether or not the current pixel data is the edge portion by verifying the data of the 9th bit of the output data from the FF 15. Then, with respect to the pixel data to which the detection result with edge detection is added, the ROM 1 (conversion table memory) is selectively referenced to perform the emphasis conversion process, and the emphasis data is output to the liquid crystal panel 4. On the other hand, for the pixel data to which the detection result without edge detection is added, the ROM 21
Selects and refers to (non-conversion table memory) and directly outputs non-conversion (through).

As described above, also in the liquid crystal display device of this embodiment, the pixel portion determined to be the edge image is switched so that the acceleration drive is turned off and the normal drive is performed. It is possible to realize the high-quality image display by removing the adverse effects caused by the accelerated driving such as unnatural coloring, white spots, and flicker that occur in the part.

In the third embodiment, the ROM
The table contents of 1 and 21 may be stored in one table memory. That is, as shown in FIG. 7, the non-conversion parameter and the emphasis conversion parameter are stored in different table areas, respectively, and the table area to be referred to is switched and controlled based on the edge detection result of the 9th bit. The same effect as in the case where the ROMs 1 and 21 are individually provided can be obtained.

[0040]

Since the liquid crystal display device of the present invention is configured as described above, the edge portion of the input image is detected, and the acceleration drive is turned off for the pixel which is determined to be the edge portion. Since the input image data of the conversion is output to the liquid crystal display panel as the display image data, it is possible to suppress the image quality deterioration due to the adverse effect of the acceleration driving and realize the 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 block diagram showing an edge detection circuit in the first embodiment of the liquid crystal display device of the present invention.

FIG. 3 is an explanatory diagram showing 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. 4 is a block diagram showing a schematic configuration of a liquid crystal display device according to a third embodiment of the invention.

FIG. 5 is an explanatory diagram showing an example of table contents of a ROM 21 (non-conversion table memory) in the third embodiment of the liquid crystal display device of the present invention.

FIG. 6 is a block diagram showing an edge detection circuit in a third embodiment of the liquid crystal display device of the present invention.

FIG. 7 is an explanatory diagram showing another ROM configuration (table content example) in the third embodiment of the liquid crystal display device of the present invention.

FIG. 8 is a block diagram showing an acceleration drive circuit in a conventional liquid crystal display device.

FIG. 9 is a block diagram showing an example of table contents of a ROM 1 (conversion table memory) in a conventional liquid crystal display device.

FIG. 10 is an explanatory diagram showing a relationship between a liquid crystal transmittance and an applied voltage when acceleration driving is performed with optimum emphasis data in a conventional liquid crystal display device.

FIG. 11 is an explanatory diagram showing a relationship between a liquid crystal transmittance and an applied voltage at the time of acceleration driving in a case where optimum enhancement data cannot be obtained in the conventional liquid crystal display device.

[Explanation of symbols]

1, 21 ROM (table memory) 2 calculator 3 frame memory 4 LCD panel 5 delay circuit 6, 16 Edge detection circuit 7 selector 8 subtractor 9 multiplier 10 adder 11 8-bit flip-flop (FF) 12 8-bit flip-flop (FF) 13 Substructor (subtractor) 14 Comparator 15 9-bit flip-flop (FF)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI G09G 3/20 641 G09G 3/20 641P 660 660N (58) Fields investigated (Int.Cl. ⁷ , DB name) G09G 3/00 -3/38 G02F 1/133 H04N 5/66-5/74

Claims (4)

(57) [Claims] 1. A liquid crystal display device for displaying an image using a liquid crystal display panel, wherein optical response characteristics of the liquid crystal display panel are compensated in accordance with gradation transition of input image data before and after at least one vertical period. Means for obtaining emphasis data, edge detection means for detecting an edge portion included in the input image data, and based on a detection result of the edge portion, one of the emphasis data and the input image data is a pixel. A liquid crystal display device, comprising: switching means for selectively switching in units and supplying as display image data to the liquid crystal display panel. 2. The liquid crystal display device according to claim 1, wherein a subtractor that subtracts the input image data from the emphasis data, and a weighting coefficient k that is variably controlled based on a detection result of the edge portion, A liquid crystal comprising: a multiplier that integrates the output data of the subtractor; and an adder that determines the display image data by adding the output data of the multiplier to the input image data. Display device. 3. The liquid crystal display device according to claim 1, wherein a conversion table memory storing enhancement conversion parameters for converting the input image data into the enhancement data, and outputting the input image data as it is. A non-conversion table memory storing a non-conversion parameter of the display image by selectively switching and referring to the conversion table memory and the non-conversion table memory based on the detection result of the edge portion. A liquid crystal display device characterized by determining data. 4. The liquid crystal display device according to claim 1, wherein an emphasis conversion parameter for converting the input image data into the emphasis data and a non-conversion parameter for outputting the input image data as they are. A reference table area in which the enhancement conversion parameter is stored and a reference table area in which the non-conversion parameter is stored are selectively switched for reference based on a detection result of the edge portion. The liquid crystal display device, wherein the display image data is determined according to.