KR20170026975A - Display device, method of detecting and compensating a mura thereof - Google Patents

Abstract

The present invention relates to a display device and a method of compensating mura thereof. The display device comprises: a memory for storing compressed compensation data; a post-processing module for removing blocking artifacts from the compressed compensation data after restoring the compressed compensation data; a data modulation part for modulating the data of an input image by using the compensation data restored by the post-processing module; and a display panel driving part for writing data modulated by the data modulation part to the pixels of the display panel. So, it is possible to reduce the memory capacity of a compensation circuit for compensating the mura.

Description

DISPLAY APPARATUS AND METHOD OF DETECTING AND COMPENSATING A MURA THEREOF

The present invention relates to a display device and a method of compensating for the smear.

The flat panel display may be an electroluminescence display (ELD) such as a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a field emission display Display, FED, plasma display panel (PDP), electrophoresis display (EPD), and the like.

The liquid crystal display controls an electric field applied to the liquid crystal layer to modulate light incident from the backlight unit to display an image. The active matrix type liquid crystal display device is advantageous in that the liquid crystal cell is driven by using a thin film transistor (hereinafter referred to as "TFT") to provide excellent image quality and low power consumption. And has rapidly developed into a larger size and higher resolution. Such liquid crystal display devices are widely used in applications such as portable computers such as notebook PCs, office automation devices, audio / video devices, indoor and outdoor advertisement display devices, and the like.

A TFT array substrate is manufactured by a semiconductor process including a photolithography process in a manufacturing process of a liquid crystal display device. The photolithography process will include a series of exposure, development, and etching processes.

Various types of speckles can be found in an inspection process for inspecting the display state of the completed substrate due to unevenness of the exposed areas in the photolithography process. The smear can be measured based on the result of measuring the brightness in the display panel of the display panel by displaying data of the same gray level on the display panel. This smear looks different in luminance or chromaticity compared to other normal pixels. The cause of the stains is that due to the difference in the amount of light in the photolithographic process, the area of overlap between the gate and the drain of the TFT, the height of the spacer, the parasitic capacitance between the signal lines and the parasitic capacitance between the signal line and the pixel electrode Gt; pixels < / RTI > in the other normal display plane at the location.

Improvement of process technology and repair process can improve the stain, but there is a limit. In recent years, a technique of reducing a defect level by applying a method of removing a stain on a display image by modulating data to be displayed on pixels at a stain position with a compensation value using a compensation circuit storing a preset compensation value for smear compensation .

However, since the compensation values are set for each pixel and are set for each gray level in each of the pixels, the memory capacity for storing the compensation values becomes large.

The present invention provides a display device capable of reducing a memory capacity of a compensation circuit for smear compensation and a smear compensation method therefor.

A display device of the present invention includes a memory for storing compressed compensation data; A post-processing module that removes the blocking artifacts from the compressed compensation data after restoring the compressed compensation data; A data modulator for modulating the data of the input image using the compensation data reconstructed by the post-processing module; And a display panel driver for writing the data modulated by the data modulator into the pixels of the display panel.

The smear compensation method of the display device detects the smear on the display panel through camera shooting and generates compensation data for compensating the luminance of the smear.

Wherein the smear compensation method of the display device converts zero data in the compensation data into an intermediate value of 8-bit data and converts + data into data larger than the intermediate value, - converts the data into data smaller than the intermediate value, Compressing and storing the compensation data in a memory; and removing the blocking artifact from the compressed compensation data after recovering the compressed compensation data. The smear compensation method of the display device modulates the data of the input image using the restored compensation data and displays the modulated data on the display panel.

The present invention removes compression loss and blocking artifacts in a high frequency region that may occur when compressing compensation data, and stores the compression loss and blocking artifact in a memory. The present invention can automatically compensate for the blur of the display device by modulating the data of the input image with the compressed compensation data. In particular, the present invention can minimize the memory capacity by compressing and storing the compensation data in the memory.

1 is a diagram showing an example of high frequency loss and blocking phenomenon in which image data is compressed by JPEG technology.
FIG. 2 is a flowchart illustrating a method of compensating a smear of a display device according to an exemplary embodiment of the present invention.
FIGS. 3 and 4 are views showing the preprocessing process shown in FIG. 2 step by step.
FIG. 5 is a diagram comparing an example in which a low frequency region is converted into a high frequency region when data is repaired and stored in a memory according to an existing method, and an example in which a low frequency region is maintained by converting data according to the present invention.
FIG. 6 is a view showing a post-process shown in FIG. 2 in a stepwise manner.
FIG. 7 is a diagram illustrating an example of the ROI selection method shown in FIG.
FIG. 8 is a diagram illustrating an example of a baseline-based detail data separation method shown in FIG.
9 is a diagram showing an example of a method of generating a new baseline using a moving average.
FIG. 10 is a diagram showing an example of generating a baseline by an average value in a block and an example of generating a baseline by moving average between blocks.
11 is a diagram illustrating a detail data restoration method using a gain.
FIG. 12 is a view illustrating a display panel stain compensation apparatus according to an embodiment of the present invention.
13 and 14 are views showing an example of compensation data generated by the interpolation method.
15 is a view showing a display device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, 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. The component name used in the following description may be selected in consideration of easiness of specification, and may be different from the actual product name.

The display device of the present invention can be applied to any display device such as a liquid crystal display (LCD), a field emission display (FED), an organic light emitting diode display (OLED) display, a plasma display panel (PDP), an electrophoresis display The present invention is also applicable to a flat panel display device.

A display device of the present invention includes a memory for detecting a blur of a display panel through camera shooting, compressing and storing compensation data for blur compensation, and a compensation circuit for restoring the compensation data to modulate the data. Since the present invention compresses the compensation data to be stored in the memory, the memory capacity can be minimized.

The compression method is exemplified by the Joint Photographic Experts Group (JPEG) technique in the embodiment, but is not limited thereto. JPEG technology converts data from a spatial domain into a discrete cosine transform (DCT) domain to compress data. Generally, a person feels sensitive to loss in the low frequency region rather than a high frequency region in an image. In consideration of this, JPEG technology compresses data in block units by increasing compression loss in a high frequency region than in a low frequency region.

When the compensation data is compressed by JPEG technology, as shown in FIG. 1, a loss occurs in a high frequency region and a blocking phenomenon occurs. Accordingly, when the compensation data is compressed by a general JPEG technology, artifacts due to artifacts and blocking phenomena due to compression loss in a high frequency range can be displayed on a display panel.

In the present invention, compensation data is converted to prevent high-frequency loss and blocking artifacts in a preprocessing process before compression, and a baseline is corrected for restoring compressed data stored in a memory in a post-process for restoring compressed data. The present invention prevents compensation data loss or distortion in JPEG compression through preprocessing and post-processing. Therefore, the present invention can apply JPEG compression to the camera compensation algorithm and compensate for the blurring of the display panel by utilizing compressed compensation data without artifact due to JPEG compression. The compensation data compression method of the present invention is not limited to the JPEG compression algorithm.

FIG. 2 is a flowchart illustrating a method of compensating a smear of a display device according to an exemplary embodiment of the present invention.

2, in the present invention, data of the same gradation level is written in all pixels of a display panel, the luminance at that time is photographed by a camera, and then the brightness of pixels is measured by analyzing the image of the camera (S1). In the camera shooting, the same process is repeated while changing the gradation of the pixels to measure the brightness of the pixels in each gradation, thereby detecting the unevenness in brightness at the same gradation. The camera shoots images of the entire screen and detects blurring, so that the blur detection time can be reduced.

Then, the present invention modulates the data to be displayed in the blur of the display panel and modulates the data of the input image into compensation values in order to remove the blur. The present invention calculates a compensation value having an inverse relationship with the luminance distribution characteristic of the pixels measured through the camera photographing. The compensation value can be expressed by Equation (1). The compensation value calculation process is repeated for each gradation. The compensation data indicating the calculated compensation value is generated (S2).

Here, C is a compensation value of n (n is a positive integer) pixel. Lpn is the luminance of the n-th pixel, and Lpc is the luminance of the center pixel (reference pixel) of the screen. gain _p is the gain reflecting the gamma deviation per pixel.

Steps S1 and S2 are described in detail in Korean patent application 10-2013-0139761 (2013/11/18) and Korean patent application 10-2013-0131798 (2013/10/31), all of which are filed by the present applicant.

The present invention converts a range of the compensation data before JPEG compression to prevent a high frequency loss occurring when compressing data with the JPEG algorithm (S3). Next, the present invention compresses the compensation data having the data range converted through the preprocessing by the JPEG algorithm and stores the compressed data in the memory (S4).

The present invention performs post-processing on the compensation data reconstructed with the JPEG algorithm to remove the blocking artifacts (S6 and S7).

In the present invention, when the input image is displayed on the display device, the compensation data reconstructed from the input image data is added to or subtracted from the input image data to modulate the pixel data in the smear region to compensate for the smear of the display panel (S8 and S9). The compensation data may generate compensation data for pixels spaced a predetermined distance to reduce the memory capacity, and may generate compensation data in a predetermined gray scale interval unit. In this case, the present invention generates compensation data of a different gradation from other pixels not obtained through actual measurement by interpolation using the restored compensation data (S8).

FIG. 3 and FIG. 4 are diagrams showing the preprocessing step S3 in a stepwise manner.

3 and 4, in the preprocessing step S32, when the compensation data D is inputted (S31), the zero data is converted and the plus data and the minus data other than the zero data, Data is converted (S33). It should be noted that S31 to S32 represent the algorithm in an understandable time series, but can be processed substantially concurrently in an actual arithmetic logic circuit. Hereinafter, steps S31 to S33 of the preprocessing process will be described in detail with practical examples. Zero data is converted to the intermediate value of 8 bit data + Data is converted to data larger than the intermediate value, and - Data is converted to data smaller than the intermediate value.

The compensation data may appear darker or lighter than normal pixels and may appear darker or lighter. The data to be written to darkly appearing pixels is added to the compensation, and the data to be written to brightly appearing pixels can be subtracted from the compensation value. Thus, the compensation data may include + data and - data.

In the example of FIG. 5, the compensation data D includes zero data "0", -data (-127 to -1), and + data (1 to 127). According to the conventional method, when such compensation data is stored in the memory, the data (-127 to -1) is converted into 255 to 128 and stored in the memory. This is because the subtraction process is performed by a method of adding using complement. Thus, when the data is stored in the memory as a complement value, the difference of the data value around the zero data can be converted into the high frequency data when stored in the memory compared to the actual compensation data range. The actual range of data is -2 to 1, but if you store the data in memory as maintenance data, the data range changes from 130 to 1. Since the spatial frequency of the data is increased in the portion where the difference between neighboring data increases, it is stored in the memory in the high frequency region. Therefore, if such data is compressed by the JPEG algorithm as it is, compression loss occurs in the high frequency region.

The present invention replaces the zero data &quot; 128 (0) &quot; in the compensation data (D) with the intermediate value &quot; 128 &quot; The present invention shifts the range of + data to 129 to 255 data by adding 128 to + data (0 <D? 127) stored in the memory, subtracts 128 from the data (128 <D? Is shifted from 0 to 127. 5, the difference between the actual compensation data -2 to 1 and the data 126 to 129 after the conversion is the same. Therefore, according to the present invention, since the compensation data in the low frequency range is preserved without being converted into the high frequency range due to the repair process, the compensation data D can be compressed without compression loss by converting the converted data into the JPEG algorithm.

FIG. 6 is a diagram showing a post-process 33 in a stepwise manner. FIG. 7 is a diagram illustrating an example of the ROI selection method shown in FIG. FIG. 8 is a diagram illustrating an example of a baseline-based detail data separation method shown in FIG. 9 is a diagram showing an example of a method of generating a new baseline using a moving average.

Referring to FIG. 6, the present invention performs post-processing on the compressed compensation data compressed by the JPEG algorithm to restore blocking data and restore detail data in blocks (S71 to S74). It should be noted that S71 to S72 represent the algorithm in an understandable time series, but can be processed substantially concurrently in actual operation logic circuits. Hereinafter, steps S71 to S74 of the post-process will be described in detail with practical examples.

The post-processing step S7 calculates the difference between the blocks by calculating the difference between the blocks and comparing the difference with the predetermined threshold value. If the difference between the blocks is larger than the threshold value, the post-process determines that the block is a location where the blocking phenomenon appears, and determines the blocks as ROI (Region Of Interest) (S71)

The post-process S7 calculates a base line, separates the detail data in the block (S72), and generates a new baseline using the moving average (S73). The post-processing step S74 reconstructs the detail data from the compressed compensation data using the gain (S74).

Referring to FIG. 7, a ROI selection method extracts a block in which a blocking phenomenon is expected based on a difference between neighboring blocks Blok (n) and Blok (n + 1). The blocking difference (Block Diff.) Can be calculated as follows.

Block Diff. = a1 * | a-a '| +? 2 * | b - b ' + ... + αn * | n - n '|

(α1> α2> ...> αn, α1 + α2 + ... + αn = 1) where a, b, ... n is the detail data in the block. n is a positive integer. (A-a ', b-b', ... n-n ') between the data located at the same distance from the boundary between the blocks Blok (n) and Blok (n + , ..., n). In order to increase the blocking difference at the boundary between the blocks Blok (n) and Blok (n + 1), the weights (? 1,? 2, ...? Value, while it can be set to a value that becomes smaller as the boundary between blocks becomes closer.

Then, the ROI selection method compares the blocking difference (Block Diff.) With a predetermined threshold value (Th.) And determines a block having a blocking difference (Block Diff.) Larger than the threshold value Th. Is determined as the position at which the blocking artifact occurs in JPEG compression. A logical value indicating the blocking artifact location, for example &quot; 1 &quot;, may be encoded at the block-to-block boundary.

Referring to FIG. 8, the present invention separates detail data from the baseline of compressed data to restore detailed information in the blocks Blok (n) and Blok (n + 1), generates a new baseline, Restore the data.

The baseline can be generated by a linear interpolation method between the detail data (n, n ') farthest from the boundary between blocks Blok (n) and Blok (n + 1).

The detail data is the difference between the baseline data in the original profile profile of the compressed compensation data and the blocks (Block (n), Block (n + 1)). The block profile includes data values within the block.

Referring to FIG. 9, the present invention generates a new baseline and calculates a new baseline between the blocks Block (n) and Block (n + 1) with average data of the blocks Block (n) and Block Reduce the boundary difference. In this method, neighboring data at the boundary between the blocks (Block (n) and Block (n + 1)) are smoothed to remove the blocking phenomenon.

The new baseline can be calculated as the moving average of neighboring blocks Blok (n), Blok (n + 1) as follows.

New base line = moving average data

Moving average current data =

Here, n is the number of data in the moving average section.

Since the compensation data obtained through camera shooting is smooth as a whole, a blocking phenomenon can be removed from JPEG compressed data by generating a new baseline with a moving average.

On the other hand, if the baseline is generated by simply averaging the values in the blocks Block (n) and Block (n + 1), the block profile of the previous block (Block (n- 1)) profile, it may show a blocking phenomenon.

The present invention generates a gain as a scale factor in order to restore the detail data derived from the existing baseline to a new baseline. Gain is the moving average divided by the baseline as shown below.

Gain = Moving average / Base line

11 is a diagram illustrating a detail data restoration method using a gain.

Referring to FIG. 11, in order to apply the detail data (diff data) to the new baseline, the detail data is restored by adding the baseline to the detail data and multiplying the gain by the following.

Reconstruct data = base line + diff data * gain = M.A + (Cur data - Base) * (M.A / Base)

M.A: moving average

Cur data: current block profile

Base: interpolation data (base line)

FIG. 12 is a view illustrating a display panel stain compensation apparatus according to an embodiment of the present invention.

Referring to FIG. 12, the smear compensation apparatus of the present invention includes a pre-processing module 10 for compressing data with a JPEG algorithm and a post-processing module 20 for restoring compressed compensation data.

The preprocessing module 10 converts the compensation data obtained through the camera image and compresses the compensation data using the JPE algorithm. The preprocessing module 10 includes a preprocessing unit 17 and an encoder 18. The preprocessing unit 17 prevents the high frequency loss generated when the compensation data is compressed by the JPEG algorithm through the compensation data conversion by converting the compensation data as shown in FIG. The encoder 18 compresses the compensation data input from the preprocessing unit 17 by the JPEG algorithm. The compensation data compressed by the preprocessing module 10 is stored in the ROM memory 12. [ The present invention can reduce the capacity of the ROM memory 12 because the compensation data is compressed.

The post-processing module 20 may be embedded in the data modulation module 200.

The ROM memory 12 and the data modulation module 200 are mounted on a drive circuit board of a display device. The data modulation module 200 may be embedded in a timing controller as shown in FIG. Compensation data stored in the ROM memory 10 is transmitted to the data modulation module 200 when power is supplied to the display device and the display device starts to be driven.

The data modulation module 200 modulates the data by adding or subtracting the compensation data to the data of the input image to be written in the pixels at the speckle position so that the display panel is not visible. The data modulation module 200 includes a memory controller 14, a RAM memory 16, a postprocessing module 20, an interpolation section 24, an image input section 28 and an adder 30.

The memory controller 14 reads the compensation data from the ROM memory 12 and stores the compensation data in the RAM memory 16 when the display device starts to be driven. The post-processing module 20 restores the compensation data from the RAM memory 16 with the JPEG algorithm, and performs post-processing such as shown in FIGS. 6 to 11 on the restored compensation data to remove blocking artifacts. The post-processing module 20 includes a decoder 22 for restoring the compensation data with the JPEG algorithm and a post-processing section 21 for removing blocking artifacts from the compensation data from the decoder 22.

The interpolation section (24) generates compensation data other than those reconstructed by the interpolation method. The interpolator 24 includes a first data generator 25 and a second data generator 26. The first data generating unit 25 generates compensation data to be written to pixels other than the pixel where the restored compensating data is written as shown in FIG. The second data generating unit 26 generates compensation data of gradation other than the gradation of the restored compensating data as shown in FIG. The adder 30 modulates the data by adding or subtracting the compensation data from the interpolator 24 to or from the data of the input image received through the image input unit 28. [

13 and 14 are views showing an example of compensation data generated by the interpolation method.

13 and 14, the compensation data is not obtained for all the pixels in order to reduce the capacity of the memories 12 and 16, but is obtained for some pixels at a predetermined position on the screen. The compensation data obtained through the camera photographing is obtained by vertically dividing the screen into blocks (B1, B2, ..., Bn-1, Bn) P1, P2, P3, and P4). The first data generating unit 25 interpolates neighboring compensation data to generate compensation data to be applied to the remaining pixels P5 other than the pixels P1 to P4.

The second data generator may not generate the compensation data in all the gradations in order to reduce the capacities of the memories 12 and 16 but may be generated in some gradations (G1 to G4 in FIG. 14). The second data generator 26 interpolates the compensation data of the nearest gradation from the compensation data stored in the memory 16 as shown in FIG. 14, and generates compensation data at gradations other than the predetermined gradation. Therefore, the present invention can minimize the capacity of the memories 12 and 16 by reducing the number of required compensation data and compressing the compensation data.

14 is a view showing a display device according to an embodiment of the present invention.

Referring to FIG. 14, the display device of the present invention includes a display panel 100, a display panel driver, and a data modulation module 200.

The display panel 100 includes a pixel array in which an input image is displayed. The pixel array includes data lines DL to which a data voltage is supplied, gate lines (or scan lines, GL) that are orthogonal to the data lines DL and supplied with gate pulses (or scan pulses) And pixels arranged in a matrix form defined by the intersection of the gate lines GL and the drain line DL. Each of the pixels may include one or more TFTs and a capacitor.

The data modulation module 200 receives the compressed compensation data from the ROM memory 120 when power is supplied to the display device. The data modulation module 200 removes the blocking artifacts through the post-processing described above to recover the compensation data and modulate the data of the input image with the compensation data.

The display panel driving unit writes data (RGB ') modulated by the data modulation module 200 to the pixels PIX of the display panel 100. The driving unit 110 includes a data driver 101, a gate driver (or a scan driver) 102, and a timing controller 103. The data modulation module 200 may be embedded in the timing controller 103.

The data driver 101 converts the digital video data RGB 'of the input image input from the timing controller 103 into an analog gamma compensation voltage to generate a data voltage and supplies the data voltage to the data lines DL do. The gate driver 102 generates a gate pulse synchronized with the data voltage and sequentially supplies the gate pulse to the gate lines GL while shifting the gate pulse.

The timing controller 103 receives digital video data RGB of an input image from a host system not shown and also receives vertical and horizontal synchronizing signals Vsync and Hsync and a data enable signal DE and a main clock DCLK, And the like. The timing controller 103 transmits the digital video data RGB 'compensated by the data modulation module 200 to the data driver 101. The timing controller 103 generates timing control signals DDC and GDC for controlling the operation timings of the data driver 101 and the gate driver using the timing signals Vsync, Hsync, DE and CLK.

The host system can be any one of a television system, a set-top box, a navigation system, a DVD player, a Blu-ray player, a personal computer (PC), a home theater system, and a phone system.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the present invention should not be limited to the details described in the detailed description, but should be defined by the claims.

10: preprocessing module 12: ROM
14: memory controller 16: RAM
20: post-processing module 24:
28: video input unit 30: adder
100: display panel 101: data driver
102: Gate driver 103: Timing controller
200: Data modulation module

Claims (5)

A memory for storing compressed compensation data;
A post-processing module that removes the blocking artifacts from the compressed compensation data after restoring the compressed compensation data;
A data modulator for modulating the data of the input image using the compensation data reconstructed by the post-processing module; And
And a display panel driver that writes data modulated by the data modulator to pixels of the display panel. The method according to claim 1,
And the compressed compensation data is JPEG compressed data. The method according to claim 1,
The post-processing module
Detecting a region of interest in which the blocking artifact is expected by comparing a difference between the blocks of the reconstructed compensation data with a preset threshold value,
Calculating a baseline of the compensation data in the region of interest, generating a new baseline with a moving average, calculating a gain from the moving average divided by the baseline,
And restores the compensation data using the gain and the moving average. Detecting blur in the display panel through camera shooting;
Generating compensation data for compensating for the luminance of the smear;
Converting the zero data in the compensation data into an intermediate value of 8-bit data and converting + data into data larger than the intermediate value, - converting the data into data smaller than the intermediate value, compressing the compensation data, ;
Removing the blocking artifact from the compressed compensation data after recovering the compressed compensation data;
And modulating the data of the input image using the restored compensation data and displaying the modulated data on the display panel. 5. The method of claim 4,
The step of removing the blocking artifact
Detecting a region of interest in which the blocking artifact is expected by comparing a difference between blocks of the reconstructed compensation data with a preset threshold value;
Calculating a baseline of the compensation data in the region of interest, generating a new baseline with a moving average, and calculating a gain with the moving average divided by the baseline; And
And restoring the compensation data using the gain and the moving average.

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