KR20060003610A - Liquid Crystal Display and Image Signal Correction Method - Google Patents

Abstract

The present invention, a liquid crystal display device includes a previous image signal (G _n-1) consisting of lower bits, the upper bits and y bits of the plurality of pixels, x bits and the current image signal on the liquid crystal display device and an image signal correction method ( current correcting the image signal based on the G _n) to a data driver for outputting the video signal correction unit, the corrected video signal to generate a corrected image signal (G _n ') is converted into a data voltage to the pixels. In this case, when the upper bits of the previous and current video signals are the same, the current video signal is corrected by a separate interpolation equation according to the magnitude of the previous and current video signals. According to the present invention, video signal correction can be made more accurate.

LCD, previous video signal, current video signal, corrected video signal, interpolation, lookup table

Description

Liquid Crystal Display and Image Signal Correction Method {LIQUID CRYSTAL DISPLAY AND METHOD OF MODIFYING GRAY SIGNALS}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a diagram illustrating an example of a lookup table of the liquid crystal display according to the exemplary embodiment of the present invention.

4A and 4B are diagrams for explaining image signal interpolation in a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a block diagram illustrating an image signal correcting unit of a liquid crystal display according to an exemplary embodiment of the present invention.

The present invention relates to a liquid crystal display and a video signal correction method.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image. In this case, in order to prevent degradation caused by an electric field applied to the liquid crystal layer for a long time, the polarity of the data voltage with respect to the common voltage is inverted frame by frame, row by pixel, or pixel by pixel.

As such TFT-LCDs are widely used not only as display devices of computers but also as display screens of televisions, there is an increasing need to implement moving images. However, the conventional TFT-LCD is difficult to implement a moving picture because the response speed of the liquid crystal is slow.

That is, since the response speed of the liquid crystal molecules is slow, it takes some time for the voltage charged in the liquid crystal capacitor to reach the target voltage, that is, the voltage at which the desired luminance can be obtained, and this time is previously charged in the liquid crystal capacitor. It depends on the difference between the voltages present. Therefore, for example, when the difference between the target voltage and the previous voltage is large, applying only the target voltage from the beginning may not reach the target voltage during the time that the switching element is turned on.                         

In order to improve the response speed of the liquid crystal in a driving manner without changing the properties of the liquid crystal, a DCC (dynamic capacitance compensation) method has been proposed. That is, the DCC method uses the fact that the higher the voltage across the liquid crystal capacitor is, the faster the charging speed is. The data voltage applied to the corresponding pixel (actually, the difference between the data voltage and the common voltage is assumed to be 0 for convenience). Higher than the target voltage shortens the time it takes for the voltage charged in the liquid crystal capacitor to reach the target voltage.

However, in some regions where the difference between the previous voltage and the target voltage is small, even if the video signal is not corrected or corrected, the implementation equation is not accurate, which makes it difficult to apply the method in practice.

Accordingly, an object of the present invention is to provide a liquid crystal display and an image signal correction method capable of accurately correcting an image signal even in a region where a difference between a previous voltage and a target voltage is small.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a previous image signal G _n-1 and a current image signal G including a plurality of pixels, upper bits of x bits, and lower bits of y bits. _n ) a video signal corrector configured to correct the current video signal to generate a corrected video signal G _n ', and a data driver converting the corrected video signal into a data voltage and outputting the data voltage to the pixel. When the lower bit is 0, the corrected video signal is predetermined as correction reference data f, and upper and lower bits of the current video signal are respectively G _n [x + y-1: y] and G _n [ y-1: 0], and the upper and lower bits of the previous video signal are G _n-1 [x + y-1: y] and G _n-1 [y-1: y], respectively. Data f is f (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = G _n '(G _n [x + y-1: y] × _{^{2 y, G n-1 [}} x + y-1: y] × 2 y) is , The upper bits and the upper bits are the same and the current when the video signal is greater than that of the first previous image signal, the corrected video signal of the current image signal of the previous image signal to the f (G _n [x + y- 1: y], G _n-1 [x + y-1: y]), f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]), Calculated by f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1), an upper bit of the previous video signal and an upper bit of the current video signal Is equal to and the current video signal is smaller than the previous video signal, the corrected video signal is f (G _n [x + y-1: y], G _n-1 [x + y-1: y] ), f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1), f (G _n [x + y-1: y] +1, G _{n- 1} [x + y-1: y] +1).

In the first case, the corrected video signal is

Gn '= f + a x G _n-1 [y-1: 0] / 2 ^y + b x G _n [y-1: 0] / 2 ^y ,

a (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]),

b (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])

-N (G _n [x + y-1: y], G _n-1 [x + y-1: y]).

In the second case, the corrected video signal is

Gn '= f + c x G _n-1 [y-1: 0] / 2 ^y + d x G _n [y-1: 0] / 2 ^y ,

c (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y]),

d (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-N (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1).

When the upper bits of the previous video signal and the upper bits of the current video signal are different from each other, the corrected video signal is

G _n '= f + p × G _n-1 [y-1: 0] / 2 ^y + q × G _n [y-1: 0] / 2 ^y + r × G _n-1 [y-1: 0] × G _n [y-1: 0] / 2 ^2y

p (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y]),

q (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y])

r (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y])

+ F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1)

-N (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]).

When the previous video signal and the current video signal are the same, the corrected video signal may be the same as the current video signal.

The video signal correction unit outputs the stored previous video signal, stores a frame memory for receiving and storing the current video signal, and stores the correction reference data, the upper bits of the current video signal and the upper bits of the previous video signal. A calculator for calculating the corrected video signal based on a lookup table for outputting the corrected reference data, and based on the corrected reference data from the lookup table, a lower bit of the current video signal, and a lower bit of the previous video signal. It may include.

According to another exemplary embodiment of the present invention, an image signal correction method of a liquid crystal display device for correcting the current image signal according to a previous image signal and a current image signal including upper bits of x bits and lower bits of y bits is provided. And receiving the current video signal, extracting correction reference data according to upper bits of the previous and current video signals, and based on the correction reference data and the lower bits of the previous and current video signals. And correcting the upper and lower bits of the current video signal, respectively, G _n [x + y-1: y] and G _n [y-1: 0]. Bit and lower bit are G _n-1 [x + y-1: y] and G _n-1 [y-1: y], and the correction reference data f is f (G _n [x + y−). 1: y], G _n-1 [x + y-1: y]) = G _n '(G _n [x + y-1: y] × 2 ^y , G _n-1 [x + y-1: ^y] × 2 y) as Time, when the upper bits and the upper bits are the same and the current image signal of the current image signal of the previous image signal is larger than the previous image signal, the corrected video signal is

Gn '= f + a x G _n-1 [y-1: 0] / 2 ^y + b x G _n [y-1: 0] / 2 ^y ,

When the upper bit of the previous video signal and the upper bit of the current video signal are the same and the current video signal is smaller than the previous video signal, the corrected video signal is

Gn '= f + c × G n-1 [y-1: 0] / 2 y + d × G n [y-1: 0] is calculated as a / 2 ^y,

a (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]),

b (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y])

c (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y]),

d (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-N (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1).

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display and an image signal correction method according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver And a gray voltage generator 800 connected to the signal 500 and a signal controller 600 for controlling the gray voltage generator 800.

The liquid crystal panel assembly 300 includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected to the plurality of display signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. .

The display signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a data line D for transmitting a data signal. ₁ -D _m ). The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Each pixel includes a switching element Q connected to a display signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q, such as a thin film transistor, is provided in the lower panel 100, and the control terminal and the input terminal are three-terminal elements, respectively, with gate lines G ₁ -G _n and data lines D ₁ -D _m . The output terminal is connected to a liquid crystal capacitor (C _LC ) and a holding capacitor (C _ST ).

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 190 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270. It functions as a dielectric. The pixel electrode 190 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives a common voltage V _com . Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, at least one of the two electrodes 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST , which serves as an auxiliary part of the liquid crystal capacitor C _LC , is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage V _com is applied to this separate signal line. However, the storage capacitor C _ST may be formed such that the pixel electrode 190 overlaps the front end gate line directly above the insulator.

On the other hand, to implement color display, each pixel uniquely displays one of the three primary colors (spatial division) or each pixel alternately displays the three primary colors over time (time division) so that the desired color can be selected by the spatial and temporal sum of these three primary colors. To be recognized. 2 shows that each pixel includes a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190 as an example of spatial division. Unlike FIG. 2, the color filter 230 may be formed above or below the pixel electrode 190 of the lower panel 100.

A polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the two display panels 100 and 200 of the liquid crystal panel assembly 300.

The gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage (V _com ) and the other set has a negative value.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to receive a gate signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off from the outside. It is applied to the gate lines G ₁ -G _n and may be formed of a plurality of integrated circuits.

The data driver 500 is connected to the data lines D ₁ -Dm of the liquid crystal panel assembly 300 to select the gray voltage from the gray voltage generator 800 and apply the gray voltage to the pixel as a data signal. Can be done.

The plurality of gate driving integrated circuits or data driving integrated circuits may be mounted in a chip carrier package (TCP) (not shown) in the form of a chip to attach the TCP to the liquid crystal panel assembly 300, or may not use TCP. These integrated circuit chips may be directly attached onto a glass substrate (chip on glass, COG mounting method), and these integrated circuits may be directly formed on the liquid crystal panel assembly 300 together with the thin film transistors of the pixel.

The signal controller 600 controls operations of the gate driver 400 and the data driver 500.

Next, the display operation of the liquid crystal display will be described in more detail.

The signal controller 600 may control the input image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical sync signal V _sync and a horizontal sync signal. (H _sync ), a main clock (MCLK), a data enable signal (DE) is provided. The signal controller 600 properly processes the image signals R, G, and B according to the operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate control signal. After generating the CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver 500. Export to

The gate control signal (CONT1) includes a gate-on voltage vertical synchronization start signal (STV) for instructing the start of output of the (V _on), the gate-on voltage gated clock signal that controls the output timing of the (V _on) (CPV) and the gate-on An output enable signal OE or the like that defines the duration of the voltage V _on .

The data control signal CONT2 includes a horizontal synchronization start signal STH indicating the start of input of the image data DAT, a load signal LOAD for applying a corresponding data voltage to the data lines D ₁ -D _m , and a common voltage. The inversion signal RVS and the data clock signal HCLK for inverting the polarity of the data voltage with respect to (V _com ) (hereinafter referred to as the "polarity of the data voltage by reducing the polarity of the data voltage with respect to the common voltage"). Include.

The data driver 500 sequentially receives and shifts the image data DAT for one row of pixels according to the data control signal CONT2 from the signal controller 600, and the gray voltage from the gray voltage generator 800. By selecting the gray scale voltage corresponding to each of the image data DAT, the image data DAT is converted into the corresponding data voltage and then applied to the corresponding data line D ₁ -D _m .

The gate driver 400 applies the gate-on voltage V _on to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n. ) Turns on the switching element Q connected thereto, so that the data voltage applied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

The difference between the data voltage applied to the pixel and the common voltage V _com is shown as the charging voltage of the liquid crystal capacitor C _LC , that is, the pixel voltage. The arrangement of the liquid crystal molecules varies according to the magnitude of the pixel voltage, thereby changing the polarization of light passing through the liquid crystal layer 3. The change in polarization is represented by a change in transmittance of light by a polarizer (not shown) attached to the display panels 100 and 200.

After one horizontal period (or “1H”) (one period of the horizontal sync signal H _sync , the data enable signal DE, and the gate clock CPV), the data driver 500 and the gate driver 400 are next. The same operation is repeated for the pixels in the row. In this manner, the gate-on voltage V _on is sequentially applied to all the gate lines G ₁ -G _n during one frame to apply the data voltage to all the pixels. At the end of one frame, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each pixel is opposite to that of the previous frame ("frame inversion). "). In this case, the polarity of the data voltage flowing through one data line may be changed (“line inversion”) within one frame or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS ( "Dot reversal").

Next, an image signal correction method according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 to 4B.

3 is a diagram illustrating an example of a lookup table of a liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 4A and 4B illustrate interpolation of an image signal in a liquid crystal display according to an exemplary embodiment of the present invention. It is a figure shown for description.

In this embodiment, the video signal G _n-1 of the (n-1) th frame (hereinafter referred to as the "previous video signal") and the video signal G _n of the nth frame (hereinafter referred to as the "current video signal") After determining the correction reference data f necessary for the operation primarily by using the upper bit (MSB) value of), the lower bit (LSB) of the previous image signal (G _n-1 ) and the current image signal (G _n ) And the corrected image signal G _n ′ is generated using the determined correction reference data f.

For convenience of explanation, it is assumed that an image signal is composed of an upper bit of x bits and a lower bit of y bits.                     

In the case of an 8-bit video signal, the number of grayscales is 256, so the combination of the previous video signal G _n-1 and the current video signal G _n is 256 × 256 = 65,536. Determining the corrected video signal G _n ′ for each of such a large number of combinations is time- and spatial-dependent, and therefore, among the combinations of these signals, for example, 17 × 17 combinations (x) determined by the upper bits. The correction video signal G _n 'is determined by measurement only for the = 4) or 9x9 combination (x = 3) and stored in the lookup table as the correction reference data f. For the remaining signal combinations, the corrected video signal G _n ′ is calculated by interpolation using the correction reference data f and the lower bits.

A lookup table corresponding to a 17 × 17 combination is shown in FIG. 3. The horizontal and vertical axes of this lookup table represent the previous video signal G _n-1 and the current video signal G _n, respectively.

In the present exemplary embodiment, blocks are divided based on values of upper bits of the previous image signal G _n-1 and the current image signal G _n , and the blocks are square regions divided by solid lines in FIG. 3. Points existing at the boundary of the block are points _where the lower bit of the previous image signal G _n-1 or the current image signal G _n is zero. For both the previous image signal G _n-1 and the current image signal G _n , the upper bits of the points present in each block are the same, and the points located on the left side and the upper side also correspond to the points in the block. Have the same high bit. However, the upper bits of the points present on the right side and the lower side are different from the upper bits of the points in the block.

In order to calculate the corrected image signal G _n ′, a block including a diagonal line D, that is, a block and a previous image signal in which the upper bits of the previous image signal G _n-1 and the current image signal G _n are the same. Different interpolation equations are used for blocks in which (G _n-1 ) and higher bits of the current video signal G _n are different from each other. When the interpolation method is applied to a point of a block, the reference data (f) for correction of the four vertices defining the block are applied.

The upper and lower bits of the current video signal are referred to as G _n [x + y-1: y] and G _n [y-1: 0], and the upper and lower bits of the previous video signal are referred to as G _n-1 , respectively. [x + y-1: y], G _n-1 [y-1: y], and the correction reference data f is defined as f (G _n [x + y-1: y], G _n-1 [ Let x + y-1: y]) = G _n '(G _n [x + y-1: y] × 2 ^y , G _n-1 [x + y-1: y] × 2 ^y ).

First, as illustrated in FIGS. 3 and 4A, blocks in which upper bits of the previous video signal G _n-1 and the current video signal G _n are different from each other, for example, correction reference data f ₀₀ and f _{01 are used.} , f ₁₀ , f ₁₁ ) will be described. Here, α and β are values obtained by dividing the lower bits of the previous video signal G _n-1 and the current video signal G _n by the block interval 2 ^y (0 ≦ α <1, 0 ≦ β <1 ).

Then, the corrected video signal G _n 'can be obtained as shown in Equation 1 below.

= F ₀₀ + p × G _n-1 [y-1: 0] / 2 ^y + q × G _n [y-1: 0] / 2 ^y + r × G _n-1 [y-1: 0] × G _n [ y-1: 0] / 2 ^2y

Where p (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₀₁ -f ₀₀

= F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -f (G _n [x + y-1: y], G _n-1 [ x + y-1: y]),

q (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₁₀ -f ₀₀

= F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])-f (G _n [x + y-1: y], G _n-1 [ x + y-1: y])

r (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₀₀ + f ₁₁ -f ₀₁ -f ₁₀

= F (G _n [x + y-1: y], G _n-1 [x + y-1: y]) + f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1)

-F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])

Next, as shown in FIGS. 3 and 4B, the upper bits of the previous video signal G _n-1 and the current video signal G _n are the same block, for example, correction reference data f ₂₂ and f _23. , f ₃₂ , f ₃₃ ) will be described.

The following proportional formula holds for the portion below the diagonal D, i.e., α <β.                     

Solving [Equation 2] and [Equation 3] with respect to G _n ', the corrected image signal (G _n ') can be expressed as follows.

= F ₂₂ + a x G _n-1 [y-1: 0] / 2 ^y + b x G _n [y-1: 0] / 2 ^y

Where a (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₃₃ -f ₃₂

= F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -f (G _n [x + y-1: y] +1, G _{n- 1} [x + y-1: y]),

b (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₃₂ -f ₂₂

= F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y])-f (G _n [x + y-1: y], G _n-1 [ x + y-1: y])

In the same manner, the corrected image signal G _n ′ for the portion above the diagonal D, that is, α> β, can also be expressed as follows.

= F ₂₂ + c x G _n-1 [y-1: 0] / 2 ^y + d x G _n [y-1: 0] / 2 ^y

Where c (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₂₃ -f ₂₂

= F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -f (G _n [x + y-1: y], G _n-1 [ x + y-1: y]),

d (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f ₃₃ -f ₂₃

= F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -f (G _n [x + y-1: y], G _n-1 (x + y-1: y] +1)

As such, when the block including the diagonal line D is interpolated according to [Equation 4] and [Equation 5], accurate image signal correction can be performed. That is, earlier than the video signal (G _n-1), the current video signal (G _n) greater than the diagonal (D) the upper part (falling part) and the current image signal (G _n) prior to the image signal (G _n-1) Since the slopes of the lookup table of the large diagonal part D (rising part) are very different in terms of liquid crystal characteristics, accurate image signal correction can be performed by using different interpolation equations for the two regions.

Meanwhile, when the previous video signal G _n-1 and the current video signal G _n are the same, the corrected video signal G _n ′ is the same as the current video signal G _n .

Next, the image signal correction of the liquid crystal display according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 5.

5 is a block diagram illustrating an image signal correcting unit of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the image signal corrector 650 of the liquid crystal display according to the exemplary embodiment of the present invention may include a signal receiver 610 and a frame memory 620 connected to the signal receiver 610. The lookup table 630 is connected to the signal receiver 610 and the frame memory 620, and a calculator 640 is connected thereto. The image signal corrector 650 or a part thereof may be included in the signal controller 600.

The signal receiver 610 receives an image signal G _m from a signal source (not shown), converts the image signal into an image signal G _n which can be processed by the image signal correcting unit 650, and then converts the image signal G _n. ) Is supplied to the frame memory 620, the lookup table 630, and the calculator 640 as the current image signal G _n .

The frame memory 620 supplies the stored previous video signal G _n-1 to the lookup table 630 and the calculator 640, and stores the current video signal G _n transmitted from the signal receiver 610. do. The frame memory 620 stores an image signal displayed on the liquid crystal display on a frame basis and may be outside the image signal corrector 650.

The lookup table 630 may be represented by a matrix of 9 × 9 or 17 × 17 as described above. The rows and columns represent the previous video signal G _n-1 and the current video signal G _n , respectively, and the reference data f for these video signals are stored where these video signals intersect in the rows and columns. It is. The lookup table 630 receives the previous image signal G _n-1 and the current image signal G _n and supplies the reference data f for correction defined by the higher bits thereof to the calculator 640.

Computing unit 640 for correcting the reference data (f) and the previous image signal (G _n-1) and the current image signal (G _n) by the interpolation corrected video signal (G _n ') has from the look-up table (640) Create That is, the operator 640 extracts the upper bits and lower bits of the previous image signal G _n-1 and the current image signal G _n , and performs interpolation according to [Equation 1] when the upper bits are different from each other. If is equal, the interpolation is performed according to Equation 4 or 5 according to the size of the lower bit.

In the embodiment of the present invention, the reference data f for the equal intervals of the previous image signal G _n-1 and the current image signal G _n are interpolated by being stored in the lookup table, but the present invention is not limited thereto. If not, the same may be applied. In addition, although the correction image signal G _n ′ is calculated using the image signals of two frames, the same applies to the case of calculating the correction image signal G _n ′ using the image signals of three frames. can do.

According to the present invention, when the upper bits of the previous video signal and the current video signal are the same, a separate interpolation equation may be applied to correct the video signal more accurately.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (7)

A plurality of pixels, The as made up of the x-bit higher-order bits and y bits of the lower bit previous image signal (G _n-1) and based on the current image signal (G _n) current correcting the image signal to generate a corrected image signal (G _n ') Video signal correction unit, A data driver converting the corrected image signal into a data voltage and outputting the converted data to the pixel Including; The corrected video signal when the lower bit is 0 is predetermined as correction reference data f, The upper and lower bits of the current video signal are G _n [x + y-1: y] and G _n [y-1: 0], respectively, and the upper and lower bits of the previous video signal are respectively G _{n−. 1} [x + y-1: y], G _n-1 [y-1: y], and the correction reference data f is f (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = G _n '(G _n [x + y-1: y] × 2 ^y , G _n-1 [x + y-1: y] × 2 ^y ) , When the upper bit of the previous video signal and the upper bit of the current video signal are the same and the current video signal is larger than the previous video signal, the corrected video signal is f (G _n [x + y-1: y ], G _n-1 [x + y-1: y]), f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]), f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1), When the higher bit of the previous video signal and the higher bit of the current video signal are the same and the current video signal is smaller than the previous video signal, the corrected video signal is f (G _n [x + y-1: y ], G _n-1 [x + y-1: y]), f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1), f (G _n [x + y-1: y] +1, calculated by G _n-1 [x + y-1: y] +1) Liquid crystal display. In claim 1, In the first case, the corrected video signal is Gn '= f + a x G _n-1 [y-1: 0] / 2 ^y + b x G _n [y-1: 0] / 2 ^y Is, a (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]), b (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]) Liquid crystal display device. In claim 1, In the second case, the corrected video signal is Gn '= f + c x G _n-1 [y-1: 0] / 2 ^y + d x G _n [y-1: 0] / 2 ^y Is, c (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]), d (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) Liquid crystal display device. In claim 1, When the upper bits of the previous video signal and the upper bits of the current video signal are different from each other, the corrected video signal is G _n '= f + p × G _n-1 [y-1: 0] / 2 ^y + q × G _n [y-1: 0] / 2 ^y + r × G _n-1 [y-1: 0] × G _n [y-1: 0] / 2 ^2y Is, p (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]), q (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]) r (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y]) + F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]) Liquid crystal display device. In claim 1, And the corrected video signal is the same as the current video signal when the previous video signal and the current video signal are the same. The method of claim 1, wherein The image signal correction unit, A frame memory which outputs the stored previous video signal and receives and stores the current video signal; A look-up table storing the correction reference data and outputting the correction reference data according to an upper bit of the current video signal and an upper bit of the previous video signal, and A calculator for calculating the corrected video signal based on the correction reference data from the lookup table, the lower bits of the current video signal, and the lower bits of the previous video signal Liquid crystal display comprising a. A video signal correction method of a liquid crystal display device which corrects the current video signal according to a previous video signal and a current video signal including upper bits of x bits and lower bits of y bits. Receiving the previous video signal and the current video signal, Extracting reference data for correction according to upper bits of the previous and current video signals, and Correcting the current video signal based on the correction reference data and the lower bits of the previous and current video signals. Including; The upper and lower bits of the current video signal are G _n [x + y-1: y] and G _n [y-1: 0], respectively, and the upper and lower bits of the previous video signal are respectively G _{n−. 1} [x + y-1: y], G _n-1 [y-1: y], and the correction reference data f is f (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = G _n '(G _n [x + y-1: y] × 2 ^y , G _n-1 [x + y-1: y] × 2 ^y ) , When the upper bit of the previous video signal and the upper bit of the current video signal are the same and the current video signal is larger than the previous video signal, the corrected video signal is Gn '= f + a x G _n-1 [y-1: 0] / 2 ^y + b x G _n [y-1: 0] / 2 ^y Is calculated as When the upper bit of the previous video signal and the upper bit of the current video signal are the same and the current video signal is smaller than the previous video signal, the corrected video signal is Gn '= f + c x G _n-1 [y-1: 0] / 2 ^y + d x G _n [y-1: 0] / 2 ^y Is calculated as a (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]), b (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y]) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]) c (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y]), d (G _n [x + y-1: y], G _n-1 [x + y-1: y]) = f (G _n [x + y-1: y] +1, G _n-1 [x + y-1: y] +1) -F (G _n [x + y-1: y], G _n-1 [x + y-1: y] +1) The video signal correction method of the liquid crystal display device.

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