KR20150072083A - Display device and driving method thereof - Google Patents

Abstract

The present invention provides a display panel which is formed by the intersection of data lines and gate lines; a scan driving part which supplies a scan signal to the gate lines; a data driving part which supplies a data voltage to the data lines; and a timing controller which determines whether image data of n bits is extended to image data of k bits which is greater than the n bits based on the value of the image data of n bits inputted from the outside, dithers the image data of k bits extended according to the determination result, and outputs the image data.

Description

DISPLAY DEVICE AND DRIVING METHOD THEREOF [0002]

The present invention relates to a display device and a driving method thereof.

2. Description of the Related Art [0002] As an information-oriented society develops, there has been a growing demand for display devices for displaying images. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various display devices such as an organic light emitting display (OLED) device are used.

In order to reproduce an actual image viewed by the user in such a display apparatus, the brightness must be expressed in various degrees. This is referred to as a gray level, and a step is divided into a range of values representing the darkest Lt; / RTI > For example, in the case of 4-bit data, the brightness is represented by dividing the gradation level into 16 levels and a range of values representing the darkest and brightest expressions on the display device. In the case of 8-bit data, 256 The luminance level is expressed by dividing the gradation level into the upper level.

If the luminance difference between the respective gauges is small, the luminance change perceived by the human eye is natural, but if the luminance difference is large, the difference in gradation between the gauges is visually perceived.

Since the number of gradation levels that can be expressed in the display device depends on the hardware processing capability of a driving IC or a circuit, if the number of bits of the image data is higher than that of the conventional one, Be able to process it.

However, when the driving IC for processing the data so that the video data is visually realized can not process the video data of a high bit number, it is necessary to replace the driving IC with a new driving IC capable of processing a high bit number of video data, Therefore, the time and cost burden will increase.

And to provide a display device and a driving method thereof that can improve the image quality without changing the existing design structure.

In another aspect, an object of the present invention is to provide a display device and a method of driving the same that can selectively perform image processing only on a portion where detailed image representation is required.

In order to achieve the above object, in one aspect, the present invention provides a display device comprising: a display panel in which data lines and gate lines are formed so as to cross each other; A gate driver for supplying a scan signal to the gate lines; A data driver for supplying a data voltage to the data lines; And decides whether to expand each n-bit image data to k-bit image data larger than n based on the values of the plurality of n-bit image data input from the outside, and to dither the expanded k- And outputs the timing controller.

In another aspect, the present invention provides a display device comprising: a display panel in which data lines and gate lines are formed so as to cross each other; A gate driver for supplying a scan signal to the gate lines; A data driver for supplying a data voltage to the data lines; And determines whether to extend each of the n-bit image data to k-bit image data larger than n based on the values of the plurality of n-bit image data input from the outside, For a value assigned to each bit up to the least significant bit based on the position of a bit having a value, the position is moved to the upper position, and a value is assigned to the remaining lower bit as the value assigned to each bit moves to the upper And a timing controller for dithering and outputting the dither signal.

According to another aspect of the present invention, there is provided a data input method comprising: inputting image data from outside; A threshold value determination step of determining whether a mask comparison value calculated based on image data of a plurality of pixels to which a mask is applied is less than or equal to a predetermined threshold value; A data expanding step of expanding the number of bits of the image data of each of the plurality of pixels to which the mask is applied by a predetermined number of bits according to the determination result of the threshold value determination step; A dithering step of performing dithering on image data of each pixel extended in the data expansion step; And a data output step of outputting the dithered image data.

As described above, according to the present invention, it is possible to selectively and finely represent an image in only a part of an image, thereby improving the efficiency of image processing.

Further, according to the present invention, it is possible to display a finer image than a conventional one without changing the existing design structure in a circuit, and thus it is possible to reduce the cost of providing a driving IC capable of processing a high data bit .

1 is a system configuration diagram of a display device to which embodiments are applied.
2 is a block diagram showing a configuration of a display device according to an embodiment.
3 is a diagram for explaining a method of determining a threshold value for a plurality of pixels to which a mask is applied in the bit extension determination unit in the embodiment.
4 is an exemplary diagram for explaining a bit extension determination unit according to an embodiment.
5 is an exemplary diagram showing another method of applying a mask in the bit extension determination unit in the embodiment.
6 is a diagram showing a method in the bit extension processing section in the embodiment.
7 is an exemplary diagram showing an example of a bit extension processing unit according to the embodiment.
8 is a diagram showing a method in the dithering processing section in the embodiment.
9 is an exemplary diagram showing an example of a dithering processing unit in the embodiment.
10 is an exemplary diagram illustrating an example of a space-time dither pattern according to an embodiment.
11 is an exemplary diagram showing another method in the bit extension processing section in the embodiment.
Fig. 12 is an exemplary diagram showing a method in the dithering processing unit in conjunction with Fig. 11. Fig.
13 and 14 are flowcharts illustrating a method of driving a display device according to an embodiment.
15 is a block diagram showing a configuration of a display device according to another embodiment.
16 is a flowchart showing a method of driving a display device according to another embodiment.
17 is a comparative diagram showing the gradation levels in the display device according to the related art and the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected." In the same context, when an element is described as being formed on an "upper" or "lower" side of another element, the element may be formed either directly or indirectly through another element As will be understood by those skilled in the art.

1 is a system configuration diagram of a display device to which embodiments are applied.

Referring to FIG. 1, a display device 100 may include a timing controller 110, a data driver 120, a gate driver 130, and a display panel 140.

The timing controller 110 controls the data driver 120 based on the vertical / horizontal synchronizing signals Vsync and Hsync input from the host system 150 and the external timing signals such as the video data RGB and the clock signal CLK. And a gate control signal GCS for controlling the gate driver 130. The gate control signal GCS for controlling the gate driver 130 is supplied to the gate driver 130. [ The timing controller 110 converts the video data RGB input from the host system 150 into a data signal format used by the data driver 120 and outputs the converted video data R'G'B ' To the data driver 120. For example, the timing controller 110 can supply the data driver 120 with the converted image data (R'G'B ') in accordance with the resolution or pixel structure of the display panel 140.

In the embodiment, the timing controller 110 determines whether to extend each n-bit image data to k-bit image data larger than n based on the values of the plurality of n-bit image data input from the outside, And dithers and outputs the expanded k-bit image data.

Further, the timing controller 110 determines whether to extend each n-bit video data to k-bit video data larger than n based on the values of the plurality of n-bit video data inputted from the outside, The position is shifted to the upper position with respect to the value assigned to each bit up to the least significant bit based on the position of the bit having the value of 1 as the first bit among the image data of the bit and when the value assigned to each bit moves upward, It is also possible to convert n-bit image data and dither the converted image data in a manner similar to the case where the values are assigned to the lower bits and expanded to k bits.

The timing controller 110 can control so that the number of bits to be expanded with respect to the video data of each pixel is different in accordance with the tone value of each of the plurality of pixels belonging to the partial area or the tone value of the central pixel among the plurality of pixels belonging to the partial area Specifically, for example, the gray level value of the pixel is compared with a predetermined reference gray level value. If the gray level value of the corresponding pixel is lower than the reference gray level value, the gray level value of the corresponding pixel is expanded .

A more detailed description of the timing controller 110 according to this embodiment will be given later with reference to the accompanying drawings.

The data driver 120 receives the data control signal DCS input from the timing controller 110 and the converted video signal R'G'B 'in response to the converted video signal R'G'B' (Data signal or analog pixel signal) which is a voltage value corresponding to the gray level value, and supplies the converted data voltage to the data line.

The gate driver 130 sequentially supplies a scan signal (a gate pulse, a scan pulse, and a gate-on signal) to the gate line in response to a gate control signal GCS input from the timing controller 110.

The display panel 140 defines a plurality of pixels at the intersections of the plurality of gate lines GL1 to GLm and the plurality of data lines DL1 to DLn. At least one organic electroluminescent device including a cathode, which is a first electrode, a cathode, a cathode, and a light emitting layer is connected to each pixel, or a liquid crystal between two substrates is switched by using a transistor And may include a liquid crystal cell for emitting light. In other words, the display panel 140 may be an organic light emitting display panel or a liquid crystal display panel, but the present invention is not limited thereto and any display panel may be used.

2 is a block diagram showing a configuration of a display device according to an embodiment.

Referring to FIG. 2, the display apparatus 100 includes a bit extension determination unit 210, a bit extension processing unit 220, and a dithering processing unit 230.

The bit extension determining unit 210 and the bit extension processing unit 220 and the dithering processing unit 230 are included in the timing controller 110. However, At least one of the bit extension processing unit 220 and the dithering processing unit 230 may be included in an image processing unit connected to an input terminal of the timing controller 110. [

The bit extension determination unit 210 determines whether or not bit expansion for fine gray scale representation is required for a part of an image implemented through the display panel 140. The bit extension determination unit 210 determines whether bit expansion (RGB), and determines whether the value calculated based on the image data of the plurality of pixels to which the mask is applied is less than or equal to a predetermined threshold value. As a result of the determination, if the calculated value is equal to or less than the threshold value, it can be regarded as an area requiring fine gradation representation, and image data of a plurality of pixels belonging to the area can be transmitted to the bit extension processing unit 220.

The bit extension processing unit 220 expands the number of bits for each image data received from the bit extension determination unit 210 and assigns a value to the extended bit positions. That is, when the value calculated according to the determination of the bit extension determination unit 210 is less than the threshold value, the bit extension processing unit 220 expands the bit number of the image data of each of the plurality of pixels to which the mask is applied by a predetermined number of bits .

The dithering processing unit 230 performs dithering on the expanded image data of each pixel, and outputs dithered image data.

The dithering processing unit 230 can derive the dither value based on the dither pattern stored in the memory 400 and apply the derived dither value to the expanded image data to perform dithering.

Hereinafter, operations of the bit extension determination unit 210, the bit extension processing unit 220, and the dithering processing unit 230 according to the embodiment will be described in detail with reference to the accompanying drawings.

3 is a diagram for explaining a method of determining a threshold value for a plurality of pixels to which a mask is applied in the bit extension determination unit 210 in the embodiment.

Referring to FIG. 3, the bit extension determination unit 210 according to the embodiment uses a mask as a method for selecting pixels to be bit extended. When a mask M of a predetermined size, for example, nXn size (n is a natural number) is applied to a plurality of pixels (area A) input to the timing controller 110, To the pixel corresponding to the position (n, n) may be designated as one pixel group for threshold value determination.

The bit extension determination unit 210 compares the image data of the pixels corresponding to each position of the mask M with a threshold value and outputs the image data of the pixels corresponding to the mask M to the bit extension processing unit 220 ). ≪ / RTI >

For convenience of explanation, a value calculated from image data of pixels corresponding to each position of the mask M for comparison with a threshold value is referred to as a mask comparison value.

The bit extension determination unit 210 may calculate the difference between the average value of the video data of the center pixel and the average value of the video data of the remaining pixels among the plurality of pixels to which the mask M is applied as a mask comparison value. The calculated mask comparison value is compared with a preset threshold value, and if the mask comparison value is equal to or greater than the threshold value, the image data of the corresponding pixels to which the mask M is applied can be directly output to the outside. When the calculated mask comparison value is compared with a preset threshold value, if the mask comparison value is less than or equal to the threshold value, the image data of the corresponding pixels to which the mask M is applied is transmitted to the bit extension processing unit 220, Let the number of bits expand.

The bit extension determination unit 210 may calculate the average value of the image data of the plurality of pixels to which the mask M is applied as a mask comparison value. If the calculated mask comparison value is equal to or less than the threshold value, the bit comparator 220 may transmit the image data of the corresponding pixels to which the mask M is applied.

The mask comparison value and the threshold value in the bit extension determination unit 210 according to the embodiment are set such that a plurality of pixels to which the mask M is applied are similar to each other Or a value for judging whether the pixel has the same gray level value, and accordingly, the threshold value may be set differently according to the method of calculating the mask comparison value.

FIG. 4 is an exemplary diagram for explaining the bit extension determination unit 210 according to the embodiment. The mask size is not limited to 3X3.

First, it is assumed that image data of a plurality of pixels to which masks are applied to the regions I1 and I2 in one image appear as I1a, I1b, and I2a.

When the bit extension determining unit 210 calculates the mask comparison value between the average value of the remaining pixels excluding the center pixel and the image data of the central pixel among the plurality of pixels to which the mask is applied, I1a, the bit extension determination unit 210 may calculate the average value 15.5 of the remaining image data excluding the image data 19 of the central pixel. In this case, since the mask comparison value is 3.5, when the threshold value is set to 15, the bit extension determination unit 210 can transmit the image data of the pixels belonging to I1a to the bit extension processing unit 220. [

If the image data of the plurality of pixels to which the mask is applied have the same value as I1b, the bit extension determination unit 210 may calculate 351.25, which is the average value of the remaining image data excluding the image data 362 of the central pixel. At this time, since the mask comparison value is 10.75, when the threshold value is set to 15, the bit extension determination unit 210 can transmit the image data of the pixels belonging to I1b to the bit extension processing unit 220. [

However, if the image data of the plurality of pixels to which the mask is applied have the same value as I2a, the bit extension determination unit 210 according to the embodiment calculates 172.25, which is the average value of the remaining image data excluding the image data 95 of the central pixel . At this time, since the mask comparison value is 77.25, the bit extension determination unit 210 can output the image data belonging to I2a to the outside without delivering it to the bit extension processing unit 220. [

Meanwhile, when the bit extension determining unit 210 calculates the average value of the image data of all the pixels to which the mask is applied as a mask comparison value, if the image data of the plurality of pixels to which the mask is applied has the same value as I1a, 210) can calculate 15.89 as a mask comparison value. When the threshold value is set to 20, since the mask comparison value is less than the threshold value, the bit extension determination unit 210 can transfer the image data of I1a to the bit extension processing unit 220. [

When the image data of the plurality of pixels to which the mask is applied has the same value as I1b, the bit extension determination unit 210 may calculate 352.44 as the mask comparison value. Therefore, the bit extension determination unit 210 does not transmit the image data of I1b to the bit extension processing unit 220 because the mask comparison value is larger than the threshold value.

However, when the average value of the image data of all the pixels to which the mask is applied to the image data of I1b is calculated as the mask comparison value, the bit extension determination unit 210 sets the image data value of the center pixel as a threshold value of the mask Since the calculated mask comparison value 352.44 is smaller than the image data value 362 of the center pixel, the image data of I1b can be transmitted to the bit extension processing unit 220. [

When the image data of the plurality of pixels to which the mask is applied has the same value as I2a, the bit extension determination unit 210 may calculate 163.67 as the mask comparison value. At this time, the mask comparison value 163.67 is the image data of the center pixel It is not necessary to transfer the image data of I2a to the bit extension processing unit 220. This means that the difference between the average value of the remaining pixels excluding the center pixel among the plurality of pixels to which the mask is applied and the image data of the center pixel Is the same as the result in the case of calculating by the comparison value.

The bit extension determination unit 210 may repeat the operation of determining whether or not bit expansion is performed by applying a mask until all the pixels of the display panel 140 are applied. As described above, It can be set differently according to the image data value of the pixels applied to the mask.

Although the operation of the bit extension determination unit 210 has been described in this specification as an example, this is merely an exemplary method. It is also possible to use various methods for determining whether a plurality of pixels to which a mask is applied have similar or identical tone values Method can be applied.

As described above, the size of a mask applied to the pixels to determine bit expansion of a plurality of pixels in the bit extension determination unit 210 is determined in advance by 3X3, 5X5, nXn, 4X3, 4X6, May be repeatedly applied until it is determined whether or not the bit is to be extended.

The size of the mask may vary depending on the image data of the plurality of pixels to which the mask is applied.

5 is an exemplary diagram illustrating another method of applying a mask in the bit extension determination unit 210 in the embodiment.

The bit extension determination unit 210 may select any one of the pixels of the display panel for applying the mask as the center pixel in order to determine the size of the mask. The bit extension determination unit 210 calculates difference values between image data adjacent to the center pixel and the center pixel (surrounding the center pixel), and determines whether the calculated difference value is less than or equal to a predetermined reference value. When all of the image data of the pixels adjacent to the central pixel are less than the reference value, the bit extension determination unit 210 calculates the difference value between the image data of each of the adjacent pixels and adjacent pixels, and outputs the calculated difference value to a predetermined reference value Or less.

Referring to FIG. 5, for example, the bit extension determination unit 210 may set the reference value to 10 and select any pixel as the center pixel P0. The bit extension determining unit 210 calculates the difference value of the image data between the pixel P0 selected as the center pixel and the pixels P1 through P8 adjacent to the center pixel, The difference value of the image data between pixels adjacent to each other is also calculated. 5, the image data value of the center pixel P0 is 61 and the image data values of the pixels P1-P8 adjacent to the center pixel are 58, 60, 65, 63, 60, 57, 58, to be. The difference value between the neighboring pixels among the pixels P1 to P8 adjacent to the center pixel does not exceed the reference value of 10 and the difference value between the pixels P1 to P8 adjacent to the center pixel does not exceed the reference value 10, The extension determination unit 210 calculates the difference value between the image data of the adjacent pixels with respect to the image data of the next adjacent pixels P9-P24.

As a result of calculation, the next adjacent pixels have difference values of image data with neighboring pixels exceeding a reference value of 10, and some pixels are shifted between image data of P12-P13, P17-P18 and P19-P20 The difference is over 10. In this case, the bit extension determination unit 210 determines the size of the mask by applying the mask only up to the center pixel P0 and the neighboring pixels P1-P8 determined to be less than the reference value.

5, if the 3x3 mask having the center pixel P0 as the center is determined according to the difference value of the image data, it is determined whether the masked pixels are delivered to the bit extension processor 220 And determines the size of the mask based on the image data again for the remaining pixels for which the bit extension or non-expansion is not determined.

FIG. 6 is a diagram showing a method in the bit extension processing section 220 in the embodiment.

Referring to FIG. 6, the bit extension processing unit 220 may extend a data bit by adding a predetermined number of bits to the video data received from the bit extension determination unit 210. FIG.

That is, when n-bit image data is transmitted from the bit extension determination unit 210, the bit extension processing unit 220 adds m bits to the transmitted n-bit image data to generate (n + m) (Where n and m are natural numbers).

The bit extension processing unit 220 can generate image data of (n + m) bits by adding m bits to the least significant bit of the n-bit image data. In the added m bits, have. For example, 3 bits can be added to 8-bit image data of 10101100 to make 10101100_000.

The m-bit value added to the n-bit image data may be set such that a fixed value is applied to the image data of all the transmitted pixels.

In addition, the value of m bits added to the n-bit image data may be set differently according to the number of bits of the input image data so that (n + m) has a fixed value.

Further, the value of m bits added to the n-bit image data can be set differently according to the image data value of each received pixel. That is, when the video data of the received pixel is equal to or smaller than the preset reference tone value, the bit extension processing unit 220 adds m1 bits to expand it to (n + m1) bits, and when the video data exceeds a reference tone value, m2 < / RTI > bits to the (n + m2) bit. At this time, when a plurality of reference gradation values are set, the number of bits of different values may be added to each reference gradation value range to expand.

Here, it is assumed that the image data value of each pixel has the same value as the tone value of the corresponding pixel in this specification.

In general, the gradation step difference recognized by the human eye is recognized more clearly at a lower gradation than at a higher gradation. Thus, when the transmitted image data value is judged to be low in gradation Bit expansion may also be performed.

That is, when the received image data value exceeds the reference tone value, the bit extension processing unit 220 determines that the corresponding pixel is not a low tone and outputs the image data as it is without performing bit expansion, If it is lower than the gray level value, it is determined that the pixel is at a low gray level and the image data can be expanded by a predetermined number of bits.

In addition, the bit extension processing unit 220 according to the embodiment can change the number of bits to be expanded according to whether the received image data value is a low gray level or a high gray level.

That is, when the received image data value is less than or equal to the reference tone value, m1 bits are added to expand the image data. When the transmitted image data value exceeds the reference tone value, m2 bits (m1 & Natural number) can be added to expand the image data.

For example, when m = 5, the bit extension processing unit 220 adds 5 bits to all video data received from the bit extension determination unit 210 to obtain (n + 5) -bit image data can be extended.

The bit extension processing unit 220 may set the number of added bits to 8 (n = 8) if the image data received from the bit extension determination unit 210 is 8 bits (n = 8) when (n + m = 8). If the received image data is 10 bits (n = 10), the number of added bits can be set to 6 (m = 6).

When the video data of the received pixel is equal to or lower than the preset reference tone value, the bit extension processing unit 220 determines that the video data is a low tone and adds 5 bits to the (n + 5) It is possible to output the image data as it is without judging the high gradation.

When the video data of the received pixel is equal to or lower than the preset reference tone value, the bit extension processing unit 220 determines that the video data is a low tone and adds 5 bits to the (n + 5) It is possible to expand the bit to (n + 2) bits by adding 2 bits according to the determination of the high gray level.

The bit extension processing unit 220 according to the embodiment calculates the number of bits (n + m) to be added so that (n + m), which is the bit number of the expanded video data, has a value of at least 11, considering the change of the luminance value according to the number of bits of the video data. .

Table 1 below is a table in which the change in the luminance value in accordance with the increase in the gray level value of the low gray level is provided for each bit number of the image data in the state in which the contrast ratio is the same.

As shown in Table 1, in the 8-bit image data, as the gray level value increases by one, the brightness value increases by an average of about 0.04 nit. In the case of a display device capable of realizing a high-resolution image such as an organic light emitting display, in order to prevent the gradation level difference from being recognized in the low gradation region, the luminance change according to the gradation should be expressed as 0.001 nit or less.

In the case of 10-bit image data, as the gray level value increases by one, the average brightness value increases by about 0.002nit. In the case of 16-bit image data, the brightness value increases by about 0.0000002nit as the gray level value increases by one. The following image data can be expanded to image data having a bit higher than 10 bits so that detailed and natural gradation representation can be performed.

The bit extension processing unit 220 may assign a value to the added lower bits and output the value to the dithering processing unit 230 in each extended video data.

At this time, the bit extension processing unit 220 may assign a value to the lower bits based on the image data values of the plurality of pixels received from the bit extension determination unit 210. The bit extension determination unit 210 may determine a plurality of masked A value can be assigned according to the magnitude relation between the image data values of the adjacent pixels or the pixels adjacent to the next adjacent pixels based on the image data value of the central pixel among the pixels.

FIG. 7 is a diagram illustrating an example of the bit extension processing unit 220 according to the embodiment. The case of expanding 10-bit image data into 16 bits will be described as an example.

Referring to FIG. 7, the bit extension processing unit 220 may receive image data values of a plurality of pixels such as I1a from the bit extension determination unit 210. FIG.

When the video data input to the timing controller 110 is 10-bit video data, the video data of the pixels arranged on the left and right of the center pixel and the center pixel can be expressed as 0000010100, 0000010011, 0000010001. The bit extension processing unit 220 adds six bits to each of 0000010100, 0000010011, and 0000010001 so that the video data received from the bit extension determination unit 210 are allocated to the upper 10 bit positions of 16 bits to obtain 0000010100_xxxxxx, 0000010011_xxxxxx, 0000010001_xxxxxx.

The bit extension processing unit 220 assigns a value to the added 6 bits. The image data value of the left pixel is larger than the image data value of the center pixel with respect to the center pixel, and the image data value of the right pixel is the image data of the center pixel Value.

Accordingly, the bit extension processing unit 220 assigns 000001, which is the minimum value of 6 bits, to the lower bit added with the expanded image data of the right pixel, and adds the maximum value 111111 to the lower bit added with the expanded image data of the left pixel Can be assigned. Further, 011111, which is an intermediate value in the range between 000001 and 111111, can be allocated to the lower bits added to the expanded image data of the center pixel.

When 6 bits are added to the image data of 9 pixels of I1b and a value is assigned, since the image data of the pixel located on the upper left side with respect to the center pixel has the lowest value, the pixel has the minimum value of 6 bits 000001 is allocated to the lower bits and since the image data of the pixel located at the left side of the center pixel has the highest value, 111111 which is the maximum value of 6 bits can be assigned to the lower bit. For the remaining image data having an intermediate value, values such as 000111, 011111, and 111000 in the range between 000001 and 111111 can be assigned to the lower bits according to the magnitude of the image data value.

The (n + m) -bit image data expanded in the bit extension processing unit 220 is transferred to the dithering processing unit 230. [ The dithering processing unit 230 dithers the data received from the bit extension processing unit, that is, the extended image data, and outputs the data.

Dithering is a method for expressing more grayscale than the grayscale display capability that can be processed by the data driver 120 in a hardware manner. For example, in a display device for processing 8-bit video data, Which means that the gradation can be expressed to the extent that it is expressed in the display device that processes the data.

The enlarged image data in the bit extension processing unit 220 is used to more finely express the gradation than the gradation of the input image data. When the number of bits of the expanded image data exceeds the number of bits that can be processed by the data driver 120 The gradation of the extended image data can not be properly represented. Therefore, in the embodiment, the gradation of the expanded image data can be expressed as it is while outputting the image data of the number of bits that can be processed by the data driver 120 through dithering .

In other words, when the number of bits that can be processed by the data driver 120 is q, the dithering processor 230 according to the embodiment outputs video data of (n + m) bits as video data of q bits, m) bits of image data.

8 is a diagram showing a method in the dithering processing unit 230 in the embodiment.

8, the image data A transmitted to the dithering processing unit 230 in the bit extension processing unit 220 is a bit (the same value as the (n + m) bit, but is referred to as a bit for convenience) The dithering processing unit 230 converts the transmitted a-bit image data into the high-order bit A1 and the low-order bit A2 of r by q, when the number of data bits that can be processed by the data driver 120 is q bits, The value can be divided by.

If the value of the upper bit A corresponding to the number of data bits that can be processed by the data driver 120 is a first bit value and the value of the lower bit B by r is a second bit value, , The dithering processing unit 230 can output the new q-bit image data by determining the dither value based on the second bit value and reflecting it on the first bit value.

For example, when the image data received by the dithering processor 230 is 16 bits and the data driver 120 can process data bits of 10 bits, the dithering processor 230 converts the lower 6 bits of the 16 bits Bit dither value based on the dither value determined by the dither value calculator 226. The new dither value is reflected in the value of the upper 10 bits and is converted into a new 10-bit value that can be expressed or approximated to the grayscale value of the 16- It is possible to output the data A '.

When the number of bits of the image data input to the timing controller 110 and the number of data bits that can be processed by the data driver 120 are the same, the value of the bit added by the bit extension processor 220 is May be determined as a second bit value.

Referring to FIG. 6, the bit extension processing unit 220 adds a bit below the least significant bit of the input image data, and the dithering processing unit 230 uses the value of the lower bit to output the value of the upper bit The dithering processing unit 230 converts the value of the bit added by the bit extension processing unit 220 into a dither value and outputs the bit value to the dithering processing unit 220. [ And the like.

That is, the input image data is n bits, the number of data bits that can be processed by the data driver 120 is n bits, m bits are added in the bit extension processing unit 220 and (n + m) bits are supplied to the dithering processing unit 230, The dithering processing unit 230 determines the value of the lower m bits of the transmitted (n + m) bit image data as the second bit value, determines the dither value, and outputs the value corresponding to the upper n bits .

The dithering processor 230 receives the data bits received from the dithering processor 230 and the data bits that can be processed by the data driver 120 regardless of the number of bits of the video data input to the timing controller 110, The second bit value may be determined according to the number.

For example, when the number of data bits that can be processed by the data driver 120 according to the embodiment is 10 bits, 8-bit video data is input to the timing controller 110 and 8 bits are added to the bit extension processor 220 When the data extended by the 16-bit image data is transferred to the dithering processing unit 230, the dithering processing unit 230 determines the upper 10 bits of the 16 bits as the first bit and the lower 6 bits of the 16- Bit.

The dithering processing unit 230 receives the 10-bit image data from the timing controller 110 and the 6-bit extended image data from the bit expansion processing unit 220 to extend the 16-bit image data to the dithering unit 230 230 may determine the upper 10 bits of the 16 bits as the first bit and the lower 6 bits of the 16-bit image data as the second bit.

9 is an exemplary diagram showing an example of the dithering processing unit 230 in the embodiment.

Referring to FIG. 9, the dithering processing unit 230 according to the exemplary embodiment displays neighboring pixels as one group to represent gradations higher than the gradation display capability that can be processed by the data driver in hardware, The gradation can be subdivided into time or space. Accordingly, the dithering processing unit 230 can apply dithering masks of a predetermined size to the video data of the plurality of pixels transmitted from the bit extension processing unit 220, At this time, the dither mask may have the same size as the mask used in the bit extension determination unit 220, but the dither mask may have a different size.

The dithering processing unit 230 may classify four pixels in the horizontal direction and four pixels in the vertical direction among the plurality of pixels received from the bit extension processing unit 220 as one group. The dithering processing unit 230 determines a value corresponding to the upper q bits as the first bit value and a value corresponding to the lower r bits as the second bit value for all the pixels in the group. The dithering processing unit 230 generates a first bit group using first bit values of all pixels in the group and generates a second bit group using second bit values of all pixels in the group can do.

For convenience of explanation, it is assumed that the pixels belonging to one column among the pixels belonging to this group have image data values of A, B, C, and D, respectively, and the second bit is 3 bits.

The dithering processing unit 230 can determine A1, B1, C1, and D1 belonging to the first bit group and determine A2, B2, C2, and D2 belonging to the second bit group for each of A, B, have.

The dithering processing unit 230 can select one of the plurality of dither patterns stored in the memory 400 based on the second bit value and determine the dither value in the selected dither pattern.

9, the dithering processing unit 230 selects one of the plurality of dither patterns DP1 to DP8 using the values of A2, B2, C2, and D2. If 3 bits are assigned to the second bit, the second bit value can vary from 0 to 7 in decimal values, and eight values are possible. Therefore, eight dither patterns can be utilized when three bits are allocated to the second bit, and two ^q dither patterns can be utilized when q bits are allocated to the second bit.

For example, when A2 = "1", B2 = "3", C2 = "4", and D2 = "0", the dithering processing unit 230 outputs the second It is possible to select the dither pattern DP2 and to select the fourth dither pattern DP4 corresponding to B2 and to select the fifth dither pattern DP5 corresponding to C2, (DP1) can be selected. Thus, each value belonging to the second bit group can be utilized to select a dither pattern.

The dithering processing unit 230 can again select one of the values of the selected dither pattern using the values of A2, B2, C2, and D2. For this, the dithering processing unit 230 may select a value by matching the position of the second bit value in the second bit group with the position in the selected dither pattern.

9, the dithering processing unit 230 can select the second dither pattern DP2 based on the value of A2 and use the fact that A2 is located at (0,0) in the second bit group Can be determined as a dither value for reflecting A1, which is a value at the position (0, 0) in the second dither pattern DP2, to A1.

The dithering processing unit 230 can select the fifth dither pattern DP5 based on the value of C2 and use the fact that C2 is in the position of (0, 3) in the second bit group, Can be determined as a dither value for reflecting C1, which is a value at position (0, 3) in DP5, to C1.

Similarly, in the fourth dither pattern DP4 selected based on the value of B2, the dithering processing unit 230 can determine 0 as a dither value for reflecting B1, which is a value corresponding to (0, 2) And can be determined as a dither value for reflecting D1, which is a value corresponding to (0, 4) which is the position of D2, in D1 in the first dither pattern DP1 selected based on the value of D2. In this way, the dithering processing unit 230 can determine the dither value for each of the image data of 16 pixels belonging to one group.

Since the dithering processing unit 230 selects the dither value by matching the position in the second bit group with the position in the selected dither pattern, the size of the dither mask may coincide with the size of the dither pattern.

When the dither value 1 is determined for A, the dithering processing unit 230 can add 1 to A1 of the first bit group to output new q-bit image data.

Therefore, when A1 has a value of 17 as a decimal number, the output new image data has a value of 18. When B1 has a value of 51, the new image data output has a value of 51, and C1 has a value of 5 , The output new image data has a value of 6, and when D1 has a value of 60, the output new image data has a value of 60. [

The dithering processing unit 230 described above is a method of performing spatial dithering using image data of neighboring pixels, and can perform spatial dithering as well as temporal dithering.

In an embodiment, the temporal dithering simply expresses the gradation by applying different dither values to each frame. To this end, the dithering processing unit 230 may change the value of each of the plurality of dither patterns stored in the memory 400 according to time.

FIG. 10 is an exemplary diagram illustrating an example of a space-time dither pattern according to an embodiment. FIG. 10 is a diagram illustrating a change in a dither pattern when time dithering is performed in four frames.

Referring to FIG. 10, in the first frame T0, the dithering processing unit 230 may perform dithering based on a dither pattern as shown in FIG. Next, in the second frame T1, the dithering processing unit 230 performs dithering based on the dither patterns in which the positions of the bit values of the dither patterns applied in the first frame T0 are shifted. In FIG. 10, each bit position of the dither patterns may be rotated and moved clockwise in time, wherein the dither patterns may be divided into an upper left quadrant, an upper right quadrant, a lower right quadrant and a lower left quadrant, . ≪ / RTI >

For example, in the first frame T0, the dither processing unit 230 may shift the bit values in the left upper quadrant of the second dither pattern DP2 (0, 0 is shifted from (0,1) in the second frame T1 to (1,1) in the third frame T2 and shifted to (1, 1) in the fourth frame T3, 0). Also, the value of the (0, 0) position of the second dither pattern changes from 1 to 0-0 from the first frame T0 to the fourth frame T3 in accordance with the positional shift. Therefore, when dithering A based on the second dither pattern, the dithering processing unit 230 adds 1 to A1 in the first frame T0, adds 0 to A1 in the second frame T1, 0 can be added to A1 in the second frame T2 and 0 can be added to A1 in the fourth frame T3 to output new video data.

Similarly, a value 1 located at (0,0) of the upper left quadrant of the fifth dither pattern DP5 in the first frame T0 is shifted from (0,1) in the second frame T1 to Is moved from the frame T2 to (1,1), and is moved from the fourth frame T3 to (1,0). Accordingly, the value of the (0, 0) position in the fifth dither pattern DP5 changes to 1-0-1-1 from the first frame T0 to the fourth frame T3. Therefore, when dithering C on the basis of the fifth dither pattern DP5, the dithering processing unit 230 adds 1 to C1 in the first frame T0, adds 0 to C1 in the second frame T1, 1 can be added to C1 in the third frame T2 and 1 can be added to C1 in the fourth frame T3 to output new image data.

In the above-described embodiment, the bit extension processing unit 220 has been described to generate extended video data by adding the number of bits to be expanded. Hereinafter, another method of obtaining an effect similar to that of expanding the data bit while minimizing the number of bits to be added is described.

When the image data value of 10 bits transmitted to the bit extension processing unit 220 is 21 or less or 53 or less as a decimal number, 0000011111 or 0000111111 is expressed by binary number. When the image data value is 21, the upper 5 bits have a value of 0. When the image data value is 53, the upper 4 bits have a value of 0. [ Another method in the embodiment is to use the higher order bits having a value of 0 to move 11111 of the lower 5 bits having a substantial value to an upper position and assign a value to the remaining lower 5 bits as the bit value moves, So that it is possible to obtain an effect similar to that of expanding the 10-bit image data transmitted to the extension processing unit 220 to 15 bits.

11 is an exemplary diagram showing another method in the bit extension processing unit 220 in the embodiment.

As shown in FIG. 11, when 0000010011, which is 10-bit image data having a value of 19 in decimal, is input to the bit extension processing unit 220, the image data is shifted upward by one bit until the value of the most significant bit becomes 1 . That is, the bit extension processing unit 220 can move 0000010011 to 0000100110 and move it to 0001001100 again, and repeats until the image data according to the bit movement has a value of 10011xxxxx. When the movement is completed, the bit extension processing unit 220 can calculate the number of upper bits having a value of 0 from the number of times the bit movement is repeated.

The bit extension processing unit 220 performs bit shifting five times with respect to the 10-bit image data, thereby assigning a value to the five lower bits so as to obtain the same effect as that of 15-bit data without generating 15-bit data .

In addition, as shown in FIG. 8, when six bits are added to expand to 16 bits, only one bit S is added to the lower five bits so that a value of 6 bits can be allocated, The same effect as that of generating 16-bit data with the data can be obtained.

When three bits are added to expand to 13 bits, the same effect as that of generating 13 bits of data can be obtained by assigning values as bits to be added to the rightmost 1 bit, which is the least significant bit of 10011.

11, the video data whose bits have been expanded in the manner as described above are converted into new data through the dithering processing unit 230. [

12 is an exemplary diagram showing a method in the dithering processing unit 230 with reference to FIG.

Referring to FIG. 12A, the dithering processing unit 230 performs dithering on the image data received from the bit extension processing unit 220 based on the lower 6-bit value.

12 (b) to 12 (d), when a new data value is allocated to the upper 5 bits among the 11 bits received from the bit extension processing unit 220 as a result of completing the dithering, Move the data value to the right by one bit. If the number of bits that can be processed by the data driver is 10, the least significant bit among the 11 bits can be deleted to make 10-bit data. The dithering processor 230 moves the data value allocated to the upper 5 bits by 10 bits to the right by one bit, and the value of the 5th bit, which is the least significant bit among the values of the upper 5 bits, moves to the 10th bit The bit shift is stopped.

Referring to (e) of FIG. 12, 10 bits of image data can be generated by assigning 0 to the upper 5 bits whose values are not defined as the upper 5 bits move downward.

The display device according to the above-described embodiment is driven as follows.

13 and 14 are flowcharts illustrating a method of driving a display device according to an embodiment.

Referring to FIG. 13, a method of driving a display device according to an embodiment of the present invention includes a data input step (S110) of inputting image data from the outside, a mask comparison step (S110) of applying a mask and calculating a mask based on image data of a plurality of pixels (S120) for determining whether a value of the image data of the plurality of pixels to which the mask is applied is less than or equal to a predetermined threshold value, A dithering step S140 for performing dithering on the image data of each pixel extended in the data expanding step, and a data outputting step S150 for outputting the dithered image data .

The threshold value determination step (S120) applies a mask of a predetermined size to a plurality of pixels adjacent to each other, and calculates a mask comparison value based on the image data of the plurality of pixels to which the mask is applied. If the calculated mask comparison value is equal to or less than the predetermined threshold value, the process proceeds to the data expansion step. If the calculated mask comparison value exceeds the threshold value, And outputs the image data as it is without expanding the number of bits (S160)

In the data expansion step S130, if it is determined that the calculated mask comparison value is less than or equal to the threshold value, a predetermined number of bits are added to the least significant bit side of each image data of the plurality of pixels applied to the mask, .

In the data expansion step (S130), the number of bits to be added may be changed according to the value of each image data of the plurality of pixels.

14, the data expansion step (S130) compares the image data value with the reference tone value (S210). As a result of the comparison, for the image data determined to be lower than the reference tone value, And the number of bits of the video data is increased (S230)

In addition, for the image data whose image data value is judged to have exceeded the reference tone value, the number of bits of the image data is increased by adding a bit as many as the second number of bits set differently from the first number of bits (S240)

Next, in step S230 and S240, a value is assigned to the bit added to the image data in accordance with the magnitude relation between the image data values of the adjacent pixels to generate the expanded image data (S250)

On the other hand, dithering is performed on the image data expanded by the predetermined number of bits in step S140. Thereafter, the dithered image data is output to the outside in step S150.

In the dithering step S140, one of the plurality of dither patterns stored in the memory 400 is selected based on the value of the lower bits of the expanded image data, and the dither value determined based on the selected dither pattern is stored in the upper bit In the case of the present invention.

On the other hand, in the display device according to the above-described embodiment, dithering is performed after the number of bits is extended for fine gradation representation only for image data whose mask comparison value is less than or equal to a threshold value, It is also possible to display more gradations of the data than the input image data.

15 is a block diagram showing a configuration of a display device according to another embodiment.

Referring to FIG. 15, a display apparatus according to another embodiment includes a first image data conversion unit 200, a second image data conversion unit 300, and a memory 400. The first image data conversion unit 200 includes a bit extension determination unit 210 and a bit extension processing unit 220. The second image data conversion unit 300 includes a smooth region determination unit 310 and a dithering processing unit 320 ). In the display apparatus according to another embodiment, since the bit expansion plate end 210 and the bit extension processing unit 220 of the first image data conversion unit 200 can operate in the same manner as in the above-described embodiment, The description is omitted, and only the case where it operates differently from the embodiment will be described in detail.

The smoothing region determining unit 310 determines whether pixels having the same image data value are adjacent to each other or whether there is a region in which the difference of image data values between neighboring pixels is small.

The bit extension determination unit 210 determines whether neighboring pixels have similar image data values as a method for selecting pixels to be expanded in the number of bits. As the size of the mask is smaller, it is determined whether the image data values are similar to a small number of pixels. Therefore, it is possible to accurately determine the image data values. However, a series of processes of applying the mask and calculating the mask comparison value and comparing with the threshold value Therefore, it may take a relatively long time to complete the above-described process for all the pixels of the display panel.

Since the bit extension determination unit 210 determines whether the image data values are similar to a larger number of pixels as the size of the mask increases, it takes a relatively short time to complete the process for all the pixels of the display panel . However, the image data values may have similar values and neighboring pixels may exist in a region smaller than the size of the mask.

Accordingly, the smoothing region determining unit 310 receives the image data of the plurality of pixels whose mask comparison value is determined to exceed the threshold value by the bit extension determining unit 210, A difference value between the image data value of the pixels near the pixel and the image data value of the center pixel is calculated.

If the difference value exceeds a predetermined smoothing reference value, the smoothing area determining unit 310 determines that the corresponding pixels are pixels that should be displayed such that the gradation is clearly displayed, for example, pixels at a position where the boundary should be displayed And outputs the video data as it is.

If the difference value is less than or equal to the smoothening reference value, the smoothing area determining unit 310 repeats the same process for other pixels close to the corresponding pixels. The smoothing area determining unit 310 is located at a distance from the center pixel, The difference between the image data value of the other pixels located at a distance from the second center pixel and the image data value of the central pixel is calculated.

If the difference value is less than or equal to the smoothening reference value, the smoothing area determining unit 310 determines at least one pixel that is located at a distance from the second center pixel and is different from the image data value of the center pixel by less than the smoothening reference value, , The difference value between the image data value of the other pixels near the third center pixel and the image data value of the center pixel can be calculated and compared with the smoothed reference value.

The smoothing area determination unit 310 may repeat this operation to select a plurality of pixels (smooth areas) having the same or similar value as the image data of the central pixel, and the image data of the selected pixels may be processed by a dithering processing unit 230 < / RTI >

The smoothing region determining unit 310 may determine that a plurality of pixels determined to have the same or similar value as the center pixel data are small enough to be perceived as being seen when viewed with the naked eye (for example, ten (For example, when the pixels are arranged in a line), the image data of the pixels may be outputted without being transmitted to the dithering processing unit 230. [

The dithering processing unit 320 performs dithering on the image data received from the smooth region determining unit 310 and outputs dithered image data. Since the image data input to the dithering processing unit 320 is not the image data having the increased number of bits, the dither pattern is selected based on the lower bit value of the input image data, the dither value is selected from the selected dither pattern, Dithering can be performed in such a manner as to reflect the value of the least significant bit of < RTI ID = 0.0 >

16 is a flowchart showing a method of driving a display device according to another embodiment.

Referring to FIG. 16, a method of driving a display device according to another embodiment includes a data input step (S310) of inputting image data from the outside, a step (S310) of applying a mask and a mask A threshold value determination step (S320) of determining whether a comparison value is less than a predetermined threshold value; and a threshold value determination step (S320) of determining whether a bit number of image data of each of a plurality of pixels to which a mask is applied is determined in advance A smoothing region determining step S340 for determining whether a plurality of pixels to which a mask is applied are a smooth area when the mask comparison value exceeds a threshold value, , The image data of the extended pixels in the data expansion step (S330), or the pixels determined to be in the smoothing region in the smoothing region determination step And a data outputting step (S370) of outputting a dithering step (S350), the dithered video data for performing dithering on the image data.

In each step, steps other than the smoothing region determination step S340 and the dithering step S350 are performed in the same manner as in the above-described embodiment, so a detailed description thereof will be omitted.

The smoothing region determining step S340 receives the image data of the plurality of pixels whose mask comparison value is determined to exceed the threshold value in the threshold value determining step S320, And calculates the difference value between the image data value of the pixels at a close distance and the image data value of the center pixel.

In the case of the pixels whose difference value exceeds a predetermined smoothing reference value, the image data of the pixels are directly output (S360), and each image data of the pixels whose difference value is judged to be equal to or lower than the smoothed reference value is output to the dithering step S350 I go over.

The dithering step S350 performs dithering on the pixels of the area determined to be the smooth area in the smooth area determination step S340. The dithering step S350 selects dither patterns based on the values of the lower bits for the respective image data of the pixels Dither can be performed by selecting a dither value from the selected dither pattern and reflecting it on the value of the least significant bit of the corresponding image data.

17A is a diagram showing a gradation pattern in a conventional organic light emitting display device, and FIG. 17B is a diagram showing the gradation level in the display device according to (b Is a diagram showing a gradation pattern in an organic light emitting display according to an embodiment of the present invention.

17 (a) and 17 (b), the gradation pattern in the conventional display device shows the same interval between the gradation levels, and at a low gradation level, the change in luminance as the gradation level increases is visually recognized appear.

On the contrary, the gradation pattern in the display device according to the embodiment exhibits a narrow interval between the gradation levels and a narrow range at the high gradation, and a larger number of gradation levels is expressed at the lower gradation than at the high gradation, The luminance change due to the increase in the gradation level is not recognized as much as in the prior art, so that it is possible to express a finer gradation at a lower gradation than in the past.

It is to be understood that the terms "comprises", "comprising", or "having" as used in the foregoing description mean that the constituent element can be implanted unless specifically stated to the contrary, But should be construed as further including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

110: Timing controller
210: bit extension determination unit
220: bit extension processing unit
230, and 320: a dithering processing unit
310: smoothing area judgment unit
400: memory

Claims (16)

A display panel in which data lines and gate lines are formed so as to cross each other;
A gate driver for supplying a scan signal to the gate lines;
A data driver for supplying a data voltage to the data lines; And
Bit image data that is larger than n based on a value of a plurality of n-bit image data input from the outside, and determines whether to expand the k-bit image data according to a determination result Timing controller for dithering and outputting
. A display panel in which data lines and gate lines are formed so as to cross each other;
A gate driver for supplying a scan signal to the gate lines;
A data driver for supplying a data voltage to the data lines; And
And determines whether to expand the n-bit image data into k-bit image data larger than n based on the values of the plurality of n-bit image data input from the outside. The position is shifted to the upper position with respect to the value assigned to each bit up to the least significant bit based on the position of the bit having the value of " 1 ", and a value is assigned to the remaining lower bits as the value assigned to each bit moves upward Next, a timing controller
. 3. The method of claim 2,
The timing controller includes:
The value assigned to each bit is shifted to an upper position until the bit having the value of 1 is shifted to the most significant bit, and as the value assigned to each bit moves to the upper bit, A bit extension processing unit for assigning a value calculated according to the magnitude relationship with the bits; And
A dithering processing unit for performing dithering on the video data received from the bit extension processing unit,
. The method of claim 3,
Wherein the dithering processing unit includes:
The position is shifted downward with respect to the value assigned to each bit up to the most significant digit based on the position of the bit to which the dither value is applied, and 0 is assigned to the remaining upper bits as the value assigned to each bit moves down . The method according to claim 1,
The timing controller includes:
A mask is applied to the n-bit image data input corresponding to the plurality of pixels, and it is determined whether or not the mask comparison value calculated based on the n-bit image data of the plurality of pixels to which the mask is applied is less than or equal to a predetermined threshold value A bit extension determination unit;
When the mask comparison value is less than or equal to the threshold according to the determination of the bit extension determination unit, the number of bits of the image data of each of the plurality of pixels to which the mask is applied is expanded by a predetermined number of bits to generate k-bit image data A bit extension processing unit; And
A dithering processing unit for performing dithering on the k-bit image data,
. 6. The method of claim 5,
The bit extension determination unit determines,
Calculates an average value of n-bit image data of the plurality of pixels to which the mask is applied as the mask comparison value, and determines whether the calculated mask comparison value is less than or equal to the threshold value. 6. The method of claim 5,
Wherein the size of the mask has a predetermined fixed value or is determined based on image data of pixels to which the mask is applied. 6. The method of claim 5,
The bit extension processing unit,
Wherein a value is assigned to the lower-order bits of the k-bit image data based on a magnitude relation of image data values between adjacent pixels among the plurality of pixels. 6. The method of claim 5,
Wherein the dithering processing unit includes:
And performs dithering on the expanded image data based on a value assigned to some lower bits of the k-bit image data and a plurality of dither patterns previously stored in the memory. 6. The method of claim 5,
Wherein the dithering processing unit includes:
And dithering is performed on the k-bit image data based on a value assigned to the lower-order bits of the k-bit image data extended by the bit extension processing unit and a plurality of dither patterns previously stored in the memory. Device. The method according to claim 1,
The timing controller includes:
Wherein the number of bits to be expanded with respect to the video data of each pixel is controlled to be different according to the grayscale value of each of the plurality of pixels belonging to the partial area or the grayscale value of the central pixel among the plurality of pixels belonging to the partial area. 12. The method of claim 11,
The timing controller includes:
The control unit compares the gray level value of the pixel with a predetermined reference gray level value and controls so that the gray level value of the corresponding pixel is larger than the reference gray level value by a larger number of bits than the expanded gray level value. Device. The method according to claim 1,
The timing controller includes:
A mask is applied to the n-bit image data input corresponding to the plurality of pixels, and it is determined whether the mask comparison value calculated based on the n-bit image data of the plurality of pixels to which the mask is applied is less than or equal to a predetermined threshold value A bit extension determination unit;
When the mask comparison value is less than or equal to the threshold according to the determination of the bit extension determination unit, the number of bits of the image data of each of the plurality of pixels to which the mask is applied is expanded by a predetermined number of bits to generate k-bit image data A bit extension processing unit;
A smoothing region determining unit for determining whether at least a part of the plurality of pixels to which the mask is applied is a smooth area when the mask comparison value exceeds the threshold according to the determination of the bit extension determining unit; And
A dithering processing unit for performing dithering on k-bit image data of each pixel or image data of pixels belonging to a smoothing area determined by the smoothing area determination unit,
. 14. The method of claim 13,
The smoothing region determining unit may determine,
The difference value between the image data of the central pixel and the image data of the pixels adjacent to the center pixel among the plurality of pixels to which the mask is applied is calculated and when the difference is equal to or less than a predetermined smoothening reference value, And judges to belong to the smoothing area. A data input step of receiving image data from outside;
A threshold value determination step of determining whether a mask comparison value calculated based on image data of a plurality of pixels to which a mask is applied is less than or equal to a predetermined threshold value;
A data expanding step of expanding the number of bits of the image data of each of the plurality of pixels to which the mask is applied by a predetermined number of bits according to the determination result of the threshold value determination step;
A dithering step of performing dithering on image data of each pixel extended in the data expansion step; And
A data output step of outputting dithered image data
And a driving method of the display device. 16. The method of claim 15,
After the threshold value determination step,
And a smoothing region determining step of determining whether at least a part of the plurality of pixels to which the mask is applied is a smooth area when the mask comparison value exceeds the threshold value,
Wherein the dithering step performs dithering on image data of a plurality of pixels determined to be a smooth region in the smoothing area determination step.

Images