KR20220161660A - Display device and method for driving the same - Google Patents

Abstract

The present specification relates to a display device capable of improving gradation expression of low luminance and a driving method thereof. According to an exemplary embodiment of the present invention, an image processing unit of a display device uses a grayscale reproduction mask pattern including a minimum value, a threshold value, and a detailed adjustment value, converts data in a low grayscale region below the threshold value into low grayscale reproduction data, and combines the threshold value, the minimum value, and the detailed adjustment value to implement the luminance of a low gradation area.

Description

Display device and its driving method {DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME}

The present specification relates to a display device capable of improving gradation expressiveness at low luminance and a method for driving the same.

The light emitting display device uses a self-emitting device that emits light through an organic light emitting layer by recombination of electrons and holes, and has advantages of high luminance, low driving voltage, ultra-thin film, and free shape.

In the light emitting display device, luminance deviation may occur between pixels with respect to the same data due to variation in characteristics of a light emitting element or driving thin film transistor (TFT), and thus non-uniformity in luminance may occur.

In the light emitting display device, a large luminance deviation between pixels is recognized in a low gradation region, and thus a stain phenomenon may occur due to low luminance non-uniformity. The light emitting display device cannot express grayscale steps discreetly due to low current driving and luminance deviation between pixels when expressing low grayscales, and thus low grayscale expressiveness may deteriorate.

The content of the background art described above is technical information that the inventor of the present specification possesses to derive examples of the present specification or acquired in the course of deriving examples of the present specification, and must be disclosed to the general public prior to filing the present specification. It cannot be said that it is a well-known technology.

The present specification provides a display device and a driving method capable of improving grayscale expressiveness at low luminance.

The problems to be solved according to the examples of the present specification are not limited to the above-mentioned problems, and other problems not mentioned are to those skilled in the art from the description below to which the technical spirit of the present specification belongs. will be clearly understood.

In the display device according to one aspect, the image processor uses a reproduction mask pattern including a minimum value and a threshold value and an adjustment value between the minimum value and the threshold value as reproduction data, and converts first data less than the threshold value from an input image into reproduction data. It may be converted and output, and the second data equal to or higher than the threshold value may be maintained and output.

In the display device according to one aspect, pixels displaying reproduction data include a first pixel displaying a first luminance corresponding to a threshold value, a second pixel displaying a second luminance lower than the first luminance corresponding to a minimum value, and A third pixel displaying a third luminance between the first luminance and the second luminance in response to the adjustment value may be included.

The threshold value may be determined as a minimum gradation value or a minimum luminance value among data for which uniformity performance is secured in measuring the uniformity of an output image for each gradation displayed on a panel.

The threshold value may include a threshold value of each color determined for each color of subpixels constituting the pixels.

The adjustment value may be determined according to the first data between the minimum value and the threshold value.

In a group of N×M pixels to which a reproduction mask pattern having a size of N×M (N, M is a natural number equal to or greater than 2) pixels is applied, the number and location of the first and second pixels may be varied according to the first data. .

Positions of the first pixel, the second pixel, and the third pixel may be varied within a group of NxM pixels according to the cumulative usage amount of the light emitting element included in each of the subpixels.

The size of the reproduction mask pattern and the number of third pixels may be determined in consideration of a panel PPI (Pixels Per Inch) and a user's viewing distance, or may be adjusted according to a user's request signal.

A group of N×M pixels may include one or two third pixels.

A method of driving a display device according to an embodiment uses a reproduction mask pattern including a minimum value and a threshold value and an adjustment value between the minimum value and the threshold value as reproduction data, and converts first data less than a threshold value from an input image into reproduction data. Converting to and outputting, and maintaining and outputting second data equal to or greater than the threshold value; A step of displaying the output data on a panel, wherein pixels displaying the reproduction data on the panel include a first pixel displaying a first luminance corresponding to a threshold value and a second luminance lower than the first luminance corresponding to a minimum value. and a third pixel displaying a third luminance between the first luminance and the second luminance corresponding to the adjustment value.

Specific details according to various examples of the present specification other than the means for solving the problems mentioned above are included in the description and drawings below.

In the display device according to an exemplary embodiment, data in a low grayscale/low luminance region where an expressiveness problem occurs is averaged by distributed arrangement of threshold values, minimum values, and detailed adjustment values whose uniformity performance is secured by using a reproduction mask pattern. By reproducing in combination, it is possible to improve the low gradation/low luminance expressiveness by securing the uniformity performance of low gradation/low luminance, and by reducing the size of the reproduction mask pattern, the pattern artifact in the form of the reproduction mask pattern is recognized in a display device with a low PPI. can prevent it from happening.

1 is a block diagram illustrating a configuration of a display device according to an exemplary embodiment.
2 is a circuit diagram illustrating a configuration of one subpixel according to an exemplary embodiment.
3 is a diagram illustrating an apparatus for measuring uniformity of a display device according to an exemplary embodiment.
4 is a diagram illustrating test images for measuring uniformity according to an exemplary embodiment.
5 is a diagram illustrating a reproduction mask according to an exemplary embodiment.
6 is a diagram illustrating a reproduction mask according to an exemplary embodiment.
7 is a diagram illustrating a reproduction mask according to an exemplary embodiment.
8 is a diagram illustrating an image processing method of a display device according to an exemplary embodiment.
9 is a diagram illustrating a low grayscale reproduction method using a reproduction mask according to an exemplary embodiment.
10 is an enlarged view of a part of an output image of an input image of a low grayscale region in a display device according to an exemplary embodiment.
11 is an enlarged view of a portion of low grayscale output images of a display device according to an exemplary embodiment.
12 is a diagram showing a low grayscale output image of a display device according to an embodiment of the present invention in comparison with a comparative example.

Advantages and features of this specification, and methods of achieving them, will become clear with reference to embodiments described below in detail in conjunction with the accompanying drawings. However, this specification is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only these embodiments make the disclosure of this specification complete, and common knowledge in the art to which this specification belongs. It is provided to completely inform the person who has the scope of the invention, and this specification is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of this specification are illustrative, so this specification is not limited to the matters shown. Like reference numbers designate like elements throughout the specification. In addition, in describing the present specification, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present specification, the detailed description will be omitted. When "comprises," "has," "consists of," etc. mentioned in this specification is used, other parts may be added unless "only" is used. In the case where a component is expressed in the singular, the case including the plural is included unless otherwise explicitly stated.

In interpreting the components, even if there is no separate explicit description of the error range, it is interpreted as including the error range.

In the case of a description of a positional relationship, for example, when the positional relationship of two parts is described as “on top,” “upper,” “lower,” “next to,” etc., for example, “right” Or, unless "directly" is used, one or more other parts may be located between the two parts.

In the case of a description of a temporal relationship, when a temporal precedence relationship is described with “after,” “next to,” “next to,” “before,” etc., unless “immediately” or “directly” is used, it is not continuous. cases may be included.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical spirit of the present specification.

In describing the components of the present specification, terms such as first, second, A, B, a, b, etc. may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, order, or number of the corresponding component is not limited by the term. When an element is described as being "connected," "coupled to," or "connected to" another element, that element is directly connected or capable of being connected to the other element, but indirectly unless specifically stated otherwise. It should be understood that other components may be “interposed” between each component that is or can be connected.

“At least one” should be understood to include all combinations of one or more of the associated elements. For example, "at least one of the first, second, and third elements" means not only the first, second, or third elements, but also two of the first, second, and third elements. It can be said to include a combination of all components of one or more.

Each feature of the various embodiments of the present specification can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each embodiment can be implemented independently of each other or can be implemented together in an association relationship. may be

Hereinafter, looking at the embodiments of the present specification through the accompanying drawings and embodiments are as follows. Since the scales of the components shown in the drawings have different scales from actual ones for convenience of explanation, they are not limited to the scales shown in the drawings.

1 is a block diagram illustrating a configuration of a display device according to an exemplary embodiment, and FIG. 2 is a circuit diagram illustrating a configuration of one pixel circuit according to an exemplary embodiment.

An electroluminescent display using a self-luminous element may be applied to the display device 1000 according to an embodiment. An organic light emitting diode (OLED) display device, a quantum-dot light emitting diode display device, or an inorganic light emitting diode display device may be applied to the electroluminescent display device. . A micro light emitting diode display device may be applied to the display device 1000 according to an embodiment.

1 and 2 , the display device 1000 includes a panel 100, a gate driver 200, a data driver 300, a timing controller 400 having an image processor 600, a gamma voltage generator ( 500) and the like. The gate driver 200 and the data driver 300 may be defined as panel drivers that drive the panel 100 . The gate driver 200, the data driver 300, the timing controller 400, the gamma voltage generator 500, and the like may be defined as a display driver.

The panel 100 displays an image through a display area DA corresponding to a pixel array area in which subpixels P are arranged in a matrix form. A basic pixel consists of three or four color subpixels among red subpixels emitting red light, green subpixels emitting green light, blue subpixels emitting blue light, and white subpixels emitting white light, or two-color subpixels. It can be made up of pixels. Meanwhile, the panel 100 may be a panel to which a touch sensor screen overlapping a pixel array is embedded or attached.

Each subpixel P includes a light emitting element and a pixel circuit independently driving the light emitting element. The light emitting device may be an organic light emitting diode, a quantum dot light emitting diode, an inorganic light emitting diode, or a micro light emitting diode. The pixel circuit is driven by storing a plurality of TFTs including a driving TFT for driving a light emitting element and a switching TFT for supplying a data signal to the driving TFT, and a driving voltage (Vgs) corresponding to the data signal supplied through the switching TFT. It includes a storage capacitor supplying the TFT. In addition, the pixel circuit further includes a plurality of TFTs for initializing the three electrodes (gate, source, and drain) of the driving TFT, connecting the driving TFT with a diode structure to compensate for the threshold voltage, or controlling the emission time of the light emitting element. can do. Various configurations such as 3T1C (3 TFTs, 1 capacitor) and 7T1C (7 TFTs, 1 capacitor) may be applied to the configuration of the pixel circuit.

For example, as shown in FIG. 2 , each subpixel P includes a first power line PW1 supplying a high potential driving voltage (first driving voltage; EVDD) and a low potential driving voltage (second driving voltage). The light emitting element 10 connected between the second power supply line PW2 supplying a voltage; EVSS, and the first and second switching TFTs ST1 and ST2 and drive to independently drive the light emitting element 10 A pixel circuit including a TFT (DT) and a storage capacitor (Cst) may be provided.

The light emitting device 10 may include an anode connected to the source node N2 of the driving TFT DT, a cathode connected to the second power line PW2, and an organic light emitting layer between the anode and the cathode. The anode is independent for each subpixel, but the cathode may be a common electrode shared by all subpixels. In the light emitting element 10, when a driving current is supplied from the driving TFT (DT), electrons from the cathode are injected into the organic light emitting layer and holes from the anode are injected into the organic light emitting layer, and fluorescence or By emitting the phosphor, light of brightness proportional to the current value of the driving current can be generated.

The first switching TFT (ST1) is driven by the scan gate pulse (SCn) supplied from the gate driver 200 to one gate line (Gn1) and the data voltage supplied from the data driver 300 to the data line (Dm). (Vdata) is supplied to the gate node N1 of the driving TFT (DT).

The second switching TFT (ST2) is driven by the sense gate pulse (SEn) supplied from the gate driver 200 to the other gate line (Gn2) and has a reference voltage supplied from the data driver 300 to the reference line (Rm). (Vref) is supplied to the source node N2 of the driving TFT (DT). Meanwhile, in the sensing mode, the second switching TFT ST2 may provide a current reflecting the characteristics of the driving TFT DT or the characteristics of the light emitting device 10 to the reference line Rm.

The first and second switching TFTs ST1 and ST2 may be controlled by different gate lines Gn1 and Gn2 or the same gate line as shown in FIG. 2 .

The storage capacitor Cst connected between the gate node N1 and the source node N2 of the driving TFT DT connects the gate node N1 and the source node ( The difference between the data voltage (Vdata) and the reference voltage (Vref) supplied to N2) is charged as the driving voltage (Vgs) of the driving TFT (DT), and the first and second switching TFTs (ST1, ST2) are turned off. The driving voltage (Vgs) charged during the light emission period is held.

The driving TFT (DT) controls the current supplied from the first power line (PW1) according to the driving voltage (Vgs) supplied from the storage capacitor (Cst) to generate a driving current determined by the driving voltage (Vgs) in the light emitting element (10). ) to cause the light emitting element 10 to emit light.

The gate driver 200 is controlled according to a plurality of gate control signals supplied from the timing controller 400 and can individually drive the gate lines of the panel 100 . The gate driver 200 supplies the scan signal of the gate-on voltage to the corresponding gate line during the driving period of each gate line (Gn1, Gn2), and applies the gate-off voltage during the non-driving period of each gate line (Gn1, Gn2). supply to the gate line. The gate driver 200 may be formed together with the TFTs of the pixel array and embedded in the panel 100 in the form of a gate in panel (GIP).

The gamma voltage generator 500 generates a plurality of reference gamma voltages having different voltage levels and supplies them to the data driver 300 . The gamma voltage generator 500 may generate a plurality of reference gamma voltages corresponding to the gamma characteristics of the display device under the control of the timing controller 400 and supply them to the data driver 300 . The gamma voltage generator 500 may adjust the reference gamma voltage level according to the gamma data supplied from the timing controller 400 and output the adjusted reference gamma voltage level to the data driver 300 . The gamma voltage generator 500 may adjust the high-potential power supply voltage, which is the maximum gamma voltage, according to the peak luminance control from the timing controller 400, and adjust a plurality of standard reference gamma voltages according to the high-potential power supply voltage to drive the data driver. (300).

The data driver 300 is controlled according to the data control signal supplied from the timing controller 400, converts the digital data supplied from the timing controller 400 into an analog data signal through a digital-to-analog converter, and Each data signal may be supplied to each data line Dm. In this case, the data driver 300 may convert digital data into an analog data signal using grayscale voltages in which a plurality of reference gamma voltages supplied from the gamma voltage generator 500 are subdivided.

The data driver 300 supplies the reference voltage Vref to the reference line Rm of the panel 100 under the control of the timing controller 400 . The data driver 300 may separately supply the reference voltage Vref for display and sensing under the control of the timing controller 400 .

Under the control of the timing controller 400, the data driver 300 may sense a signal reflecting the driving characteristics of each subpixel through each reference line Rm using a sensing unit using a voltage sensing method or a current sensing method.

For example, when the data driver 300 is in the sensing mode under the control of the timing controller 400, the data for sensing received from the timing controller 400 is converted into the data voltage Vdata for sensing, and the data line Dm ), and the sensing reference voltage Vref may be supplied to the reference line Rm. In the subpixel selected by the scan gate pulse (SCn) and sense gate pulse (SEn) from the gate driver 200, the driving TFT (DT) receives the sensing data voltage (Vdata) supplied through the first switching TFT (ST1). And, it can be driven by the reference voltage (Vref) for sensing supplied through the second switching TFT (ST2) and can supply current to the light emitting element (10). A reference line (Rm) in which a current reflecting electrical characteristics (threshold voltage, mobility) of the driving TFT (DT) or deterioration characteristics (threshold voltage) of the light emitting element 10 is in a floating state through the second switching TFT (ST2) It may be charged as a voltage in the line capacitor of or converted into a voltage through a current integrator connected to the reference line (Rm). The data driver 300 may sample and hold a voltage reflecting characteristics of each subpixel, convert the voltage into sensing data through an analog-to-digital converter, and output the converted voltage to the timing controller 400 .

The timing controller 400 may receive a source image and timing control signals from an external host system. The host system may be any one of a system of a portable terminal such as a computer, a TV system, a set-top box, a tablet or a mobile phone. The timing control signals may include a dot clock, a data enable signal, a vertical sync signal, a horizontal sync signal, and the like.

The timing controller 400 may control the gate driver 200 and the data driver 300 using timing control signals supplied from the host system and timing setting information stored therein. The timing controller 400 may generate a plurality of gate control signals for controlling driving timing of the gate driver 200 and supply them to the gate driver 400 . The timing controller 400 may generate and supply a plurality of data control signals for controlling driving timing of the data driver 300 to the data driver 300 .

The timing controller 400 may include an image processing unit 600 that performs various image processing on a source image. The image processing unit 600 may be positioned to be separated from the timing controller 400 and connected to an input terminal of the timing controller 400. In this case, the output of the image processing unit 600 is output to the data driver 300 through the timing controller 400. ) can be supplied.

The image processing unit 600 may determine data in a low grayscale region where a low grayscale expressiveness problem occurs with respect to the input image. The image processing unit 600 applies a reproduction mask pattern in which a threshold value, a minimum value, and a detailed adjustment value are set in advance as reproduction data to the determined data of the low grayscale region, and converts the data of the low grayscale region to a threshold value according to pixel positions in the reproduction mask pattern. It can be converted into reproduction data of any one of values, minimum values, and detailed adjustment values.

The threshold value for the image data may be a minimum value among grayscales or luminances for which uniformity performance is secured through a uniformity measurement process. The threshold value may vary depending on the type of display device. The threshold value may be an intermediate grayscale or intermediate luminance having excellent uniformity and expressiveness of grayscale. The threshold value may be a minimum value among gradation values or luminance values of each color having excellent uniformity and gradation expressiveness.

The minimum value may be a black gradation or black luminance, which is the minimum gradation (gradation 0) or the minimum luminance.

The detailed adjustment value may be determined so that the average luminance of the reproduction mask pattern composed of the threshold value, the minimum value, and the detailed adjustment value is equal to the luminance of a low gray level to be reproduced. Although various gradations (luminance) may be used as the detailed adjustment value, it may be determined according to an input low gradation by considering an average luminance of a reproduction mask pattern among gradations (luminances) between a minimum value and a threshold value. By increasing the number of expressible brightness values, the size of the reproduction mask pattern can be reduced compared to the reproduction mask pattern using only the threshold value and the minimum value.

The image processing unit 600 may vary the application position of the threshold value, the minimum value, and the detailed adjustment value within the reproduction mask pattern in consideration of the lifetime of each light emitting device according to the usage amount. The image processing unit 600 may cumulatively count the data of each subpixel to accumulate the usage amount of each light emitting element, and apply the threshold value, minimum value, and detailed adjustment value within the reproduction mask pattern according to the order of accumulated usage amount of each light emitting element. position can be changed. As a result, the image processing unit 600 may reduce a lifespan deviation between light emitting devices.

The image processing unit 600 may maintain and output image data equal to or higher than the threshold.

The image processing unit 600 may further perform a plurality of image processing including image quality correction, deterioration correction, luminance correction for reducing power consumption, and the like, prior to the above-described low grayscale reproduction processing.

The timing controller 400 may further correct the output of the image processor 600 by applying a compensation value for characteristic deviation of each subpixel stored in the memory before supplying the output of the image processor 600 to the data driver 300 . In the sensing mode, the timing controller 400 senses the characteristics of each subpixel P of the panel 100 through the data driver 300 and updates the compensation value of each subpixel stored in the memory using the sensing result. can do. The sensing mode of the display device may be performed according to an instruction of the host system, a user request through the host system, or a driving sequence of the timing controller 400 .

In this way, the display device 1000 including the image processing unit 600 according to an exemplary embodiment converts the data of the low grayscale region where the expressiveness problem occurs to the threshold value, the minimum value, and the detailed adjustment value for which uniformity performance is secured. By reproducing with an average combination by dispersive arrangement, it is possible to improve uniformity and low gradation expressiveness, and it is possible to relatively reduce the size of a reproduction mask pattern, so that pattern artifacts in the form of a reproduction mask pattern can be prevented from being recognized.

3 is a diagram illustrating an inspection system of a display device according to an exemplary embodiment, and FIG. 4 is a diagram illustrating test images for measuring uniformity according to an exemplary embodiment.

Referring to FIG. 3 , a display device inspection system includes a display device 1000 , an electronic device 2000 , and a measurement device 3000 .

The display device 1000 may receive a test image for measuring uniformity from the electronic device 2000 and display it on the panel 100 (see FIG. 1 ).

The display device 1000 may sequentially display test images for each gray level and color supplied from the electronic device 2000 . For example, as shown in FIG. 4 , the test image may be a gray full pattern image in which the gray level increases by one step from 1 gray level.

The measuring device 3000 may capture a test image displayed on the panel 100 of the display device 1000 to measure luminance, chromaticity, and the like, and supply the measurement results to the electronic device 2000 . The measuring device 3000 measures the luminance of each of a plurality of sampling points located at different locations on the panel 100 whenever the display device 1000 displays the test image for each gradation shown in FIG. 4 on the panel 100. Thus, the measurement result may be supplied to the electronic device 2000.

The electronic device 2000 may calculate uniformity for each gray level, corresponding to a ratio of a minimum luminance value to a maximum luminance value among a plurality of sampled luminances of the test image for each gray level supplied from the measuring device 3000 . The electronic device 2000 compares the calculated uniformity for each gradation with a preset threshold uniformity Thu, and secures uniformity performance for gradations (K, K+1, ??) for which the calculated uniformity is greater than the threshold uniformity Thu. It can be judged by the gradation. The electronic device 2000 may determine the minimum grayscale (K) among the grayscales (K, K+1, ??) for which uniformity performance is secured as a grayscale threshold value applied to the reproduction mask pattern. The electronic device 2000 may supply the grayscale threshold value K having uniformity performance to the display device 1000 to be used as the threshold value of the reproduction mask pattern.

5 to 7 each show a reproduction mask pattern according to an exemplary embodiment.

Referring to FIG. 5 , a reproduction mask pattern M22 having a size of a 2×2 pixel group may be used to convert data of a low grayscale region into reproduction data having excellent uniformity and expressiveness. The reproduction mask pattern M22 may be set for each color. A reproduction mask pattern M22 for each color may be applied to data of a 2Х2 pixel group for low grayscale reproduction. Three mask values (P1, P2, P3) of the reproduction mask pattern (M22) are applied to three uniformity improvement pixels (UIP) among 2Х2 pixel groups, respectively, and one mask value (P4) is applied to one of the 2Х2 pixel groups. It may be applied to the detailed brightness control pixel (BCP). Positions of the mask values P1, P3, and P3 applied to the uniformity improvement pixel UIP and the position of the mask value P4 applied to the detail brightness control pixel BCP within the reproduction mask pattern M22 are variable. It can be. Among the mask values (P1, P3, P3) applied to the uniformity improvement pixel (UIP) of the reproduction mask pattern (M22), a threshold value and a minimum value for ensuring uniformity performance may be assigned according to the input grayscale. Depending on the value, the number and location of the threshold and minimum values may be varied. For the mask value P4 applied to the detailed brightness control pixel BCP of the reproduction mask pattern M22, a detailed adjustment value between a minimum value and a threshold value may be variably assigned according to the input grayscale. Mask values P1 to P4 of the reproduction mask pattern M22 may be defined as low grayscale reproduction data.

Referring to FIG. 6 , a reproduction mask pattern M33 having a size of 3Х3 pixel groups may be used to convert data of a low grayscale region into reproduction data having excellent uniformity and expressiveness. The reproduction mask pattern M33 may be set for each color. A reproduction mask pattern M33 for each color may be applied to data of a 3Х3 pixel group for low grayscale reproduction. Seven mask values (P2, P3 to P7, P9) of the reproduction mask pattern (M33) are applied to seven uniformity improvement pixels (UIP) among 3Х3 pixel groups, respectively, and two mask values (P1, P8) may be applied to each of the two detailed brightness control pixels (BCP) of the 3Х3 pixel group. Positions of the mask values (P2, P3 to P7, P9) applied to the uniformity improvement pixel (UIP) within the reproduction mask pattern (M33) and the mask values (P1, P8) applied to the detail brightness control pixel (BCP) ) The position of may be variable. Among the mask values (P2, P3 to P7, P9) applied to the uniformity improving pixel (UIP) of the reproduction mask pattern (M33), a threshold value and a minimum value for ensuring uniformity performance may be given according to the input grayscale. Depending on the gray level, the number and location of the threshold and minimum values may be varied. A detailed adjustment value between a minimum value and a threshold value may be variably assigned to the mask values P1 and P8 applied to the detailed brightness control pixel BCP of the reproduction mask pattern M33 according to the input grayscale. The mask values P1 to P9 of the reproduction mask pattern M33 may be defined as low grayscale reproduction data.

Referring to FIG. 7 , a reproduction mask pattern M23 having a size of 2Х3 pixel groups may be used to convert data of a low grayscale region into data having excellent uniformity and expressiveness. The reproduction mask pattern M23 may be set for each color. A reproduction mask pattern M23 for each color may be applied to data of a 2Х3 pixel group for low grayscale conversion. Five mask values (P1 to P4, P6) of the reproduction mask pattern (M23) are applied to five uniformity improvement pixels (UIP) among the 2Х3 pixel groups, respectively, and one mask value (P5) is applied to each of the 2Х3 pixel groups. It may be applied to one detail brightness control pixel (BCP). The position of the mask values (P1 to P4, P6) applied to the uniformity improvement pixel (UIP) and the position of the mask value (P5) applied to the detail brightness control pixel (BCP) within the reproduction mask pattern (M23) are variable. It can be. Among the mask values (P1 to P4, P6) applied to the uniformity improving pixel (UIP) of the reproduction mask pattern (M23), a threshold value and a minimum value for ensuring uniformity performance may be assigned according to the input grayscale. Depending on the value, the number and location of the threshold and minimum values may be varied. A detailed adjustment value between a minimum value and a threshold value may be variably assigned to the mask value P5 applied to the detailed brightness control pixel BCP of the reproduction mask pattern M23 according to the input grayscale. Mask values P1 to P6 of the reproduction mask pattern M23 may be defined as low grayscale reproduction data.

In order to convert the data of the low grayscale region into data with excellent uniformity and expressiveness, the reproduction mask patterns applied to the data of the low grayscale region are limited to the reproduction mask patterns M22, M33, and M23 shown in FIGS. 5 to 7 It does not, and may have various pixel sizes according to PPI (Pixels Per Inch) of the display device or user's needs.

The smaller the PPI of the display device, the smaller the reproduction mask pattern may be.

The size of the reproduction mask pattern may be determined in consideration of the PPI of the display device and the user's viewing distance. That is, the size of the reproduction mask pattern is within the range in which pattern artifacts due to the application of the reproduction mask pattern are not recognized in consideration of the limit PPI (Pixels Per Inch) corresponding to the resolution of the user's eyes according to the user's viewing distance. can be determined in The size of the reproduction mask pattern can be varied according to the user's needs (request signal).

For example, assuming that the viewing distance is 60 cm, the limit PPI of the display device is 150 PPI, and the specification of the target display device is 300 PPI, the reproduction mask pattern may be determined to have a size of 2 × 2 pixels shown in FIG. 5, Not limited to this.

In the reproduction mask patterns M22, M33, and M23, the number of detailed brightness control pixels BCP to which detailed adjustment values are assigned may be determined according to the size of the reproduction mask pattern or a user's need.

8 is a diagram illustrating an image processing method of a display device according to an exemplary embodiment, and FIG. 9 is a diagram illustrating a low grayscale reproduction method using a reproduction mask pattern according to an exemplary embodiment.

The image processing method shown in FIG. 8 is performed by the image processing unit 600 described in FIG. 1 .

Referring to FIG. 8 , the image processing unit 600 receives an input image (S802) and compares the data of the supplied input image with the threshold TH for which uniformity performance is secured. It is determined whether the data is in the gradation area (S802, S804). The image processing unit 600 may compare data for each color of the input image with the threshold value TH for each color to determine whether each color data is low grayscale data less than the threshold value TH for each color.

The image processor 600 maintains and outputs the input data when the input data is greater than the threshold value TH (NO) (S808).

The image processing unit 600 converts the input data into low grayscale reproduction data by applying a reproduction mask pattern to the input data when it is determined that the input data is lower than the threshold value TH (YES) (S806), and converts the converted data into low grayscale data. Outputs (S810).

If each color data is less than the threshold TH of each color, the image processing unit 600 may apply a reproduction mask pattern of each color to convert each color data into low-grayscale reproduction data and output the converted data.

For example, as shown in FIG. 9 , the image processing unit 600 converts the data of the low grayscale region below the threshold TH at which uniformity performance is secured to the reproduction mask pattern having a size of 2×2 pixels described in FIG. 5 . (M22) may be applied for each color to be converted into low grayscale reproduction data and output.

Referring to FIG. 9 , the low grayscale data of three uniformity improvement pixels (UIP) among the 2×2 pixel groups of the low grayscale image to which the reproduction mask pattern M22 is applied is the threshold value TH and The minimum value (0) may be converted into distributed mask values (P1, P2, P3) respectively. The low grayscale data of the detailed brightness control pixel (BCP) among the 2x2 pixel groups of the low grayscale image may be converted into detailed adjustment values (C, D, E, ??) that are mask values (P4). The detailed adjustment values (C, D, E, ??) of the detailed brightness control pixels (BCP) are set for each gradation (1, ??, A, B, ??) between the minimum value (0) and the threshold value (TH). can be determined according to

Additionally, the image processing unit 600 cumulatively counts the data of each subpixel to accumulate the usage amount of each light emitting element, and according to the order of the accumulated usage amount of each light emitting element, the threshold value (TH) and minimum value within the range of the reproduction mask pattern (M22) The application position of (0) and detailed adjustment values (C, D, E, ??) can be varied. As a result, the image processing unit 600 may reduce a lifespan deviation between light emitting elements according to the cumulative usage amount of each light emitting element.

As described above, the display device according to an exemplary embodiment uses a reproduction mask for data in a low grayscale or low luminance (low grayscale/low luminance) region having poor expressiveness and uniformity, and a threshold value and a minimum value , can be reproduced as an average combination by distributed arrangement of detailed adjustment values.

Accordingly, the display device according to an exemplary embodiment may secure low grayscale uniformity performance by using the uniformity improvement pixel to which the threshold value and the minimum value for which uniformity performance is secured are applied, thereby improving low grayscale expressiveness. In addition, the display device according to an embodiment can relatively reduce the size of the reproduction mask pattern by using the detailed brightness control pixels to which the detailed adjustment value is applied while improving the expressive power of low gradation, so that the reproduction mask pattern can be obtained in a display device with a low PPI. Recognition in the form of pattern artifacts can be prevented.

10 is an enlarged view of a part of an output image of an input image of a low grayscale region in a display device according to an embodiment, and FIG. 11 is an enlarged view of a part of low grayscale output images of a display device according to an embodiment. drawings shown.

The display device inspection system described in FIG. 3 may be used to check the output image for the input image shown in FIGS. 10 and 11 .

Referring to FIGS. 3 and 10 , the display device 1000 according to an exemplary embodiment receives a gray full pattern test image that increases by one step from 0 grayscale from the electronic device 2000 and displays a panel 100 , see FIG. 1).

Whenever the display device 1000 displays a low-grayscale test image for each gradation on the panel 100, the measurement device 3000 photographs the pixels of the display device 1000 using a microscope camera to determine the luminance and brightness of each pixel. The color may be measured and the measurement result may be supplied to the electronic device 2000 . For example, each pixel P of the display 1000 may include a plurality of sub-pixels SP1, SP2, and SP3 having different colors, and the measuring device 3000 may include sub-pixels constituting each pixel P. The luminance and color of each of the pixels SP1 , SP2 , and SP3 may be photographed and measured.

The electronic device 2000 periodically displays a pattern of the same size repeatedly from the grayscale output images (Output A, Output B, Output C, ??) of the display device 1000 supplied through the measuring device 3000. You can check whether the reproduction mask pattern is used by checking.

For example, the electronic device 2000 uses a reproduction mask pattern M22 in which a pattern of the same size is periodically repeated from the grayscale output images (Output A, Output B, Output C, ??) shown in FIG. 10. can check whether

In the display device 1000, in a 2×2 pixel group corresponding to the reproduction mask pattern M22, the uniformity improvement pixels UIP display mask values P1, P2, and P3 in which threshold values and minimum values are distributed and arranged, , the detailed brightness control pixel BCP may display a mask value P4 having a detailed control value according to gray levels.

The electronic device 2000 may receive measurement results of output images (Output A, Output B, Output C, ??) for each gray level of the display device 1000 through the measurement device 3000 . The electronic device 2000 determines, from the measurement results of output images (Output A, Output B, Output C, ??) for each gray level of the display device 1000, among the 2×2 pixel group corresponding to the reproduction mask pattern M22. , The uniformity improvement pixels UIP include a first pixel (white part) displaying a first luminance by a threshold value and a second pixel (black luminance) displaying a second luminance lower than the first luminance (black luminance) by a minimum value ( High-density dot portion), and the detailed brightness control pixel (BCP) displays a third luminance whose brightness varies minutely according to the gradation between the first luminance and the second luminance by the detailed control value. It can be confirmed that it operates as a third pixel (low density dot part).

Specifically, referring to FIG. 11 , the electronic device 2000 measures the output images (Output 1 to Output 6) of the display device 1000 for an input image in which low gray levels increase step by step. By detecting each pixel group in which the pattern is repeated, it is possible to check whether the reproduction mask pattern M22 is applied.

The electronic device 2000 includes a first pixel (on pixel) displaying a first luminance by a threshold value and a second pixel displaying a second luminance (black luminance) by a minimum value from the measured luminance of a 2×2 pixel group. (off pixels), and the presence or absence of uniformity improvement pixels (UIPs), the number and location of which are variable according to the gray level, of the first pixels (on pixels) and the second pixels (off pixels) may be checked. In addition, the electronic device 2000 is a detailed brightness control pixel (third pixel) displaying third luminance whose brightness minutely varies between the first luminance and the second luminance according to the gradation, from the measured luminance of the 2x2 pixel pattern. , the existence of BCP1 to BCP6) can be confirmed.

In this way, the electronic device 2000 measures the luminance and color of each pixel displaying the output image for the input test image (gray full pattern) of the display device 1000, and the pattern of the same size is repeated to improve the uniformity of the pixel. It can be checked whether a reproduction mask pattern including (UIP) and detailed brightness control pixels (BCP) is applied.

Furthermore, the electronic device 2000 measures and compares output images of the same low-gradation input image displayed on the display device 1000 before and after driving the display device 1000 for a long time, so that the According to the lapse of driving time, that is, according to the accumulated usage of each light emitting element, among the pixels to which the reproduction mask pattern is applied, the first pixel displaying the threshold value, the second pixel displaying the minimum value, and the third pixel displaying the detailed adjustment value. It can be further confirmed that the position is variable.

12 is a view showing a low grayscale output image of a display device according to an embodiment of the present invention in comparison with a comparative example.

Referring to FIG. 12, as a result of photographing 16 gray full pattern images displayed by the display device of the comparative example and the display device according to an embodiment of the present specification, the display device of the comparative example has relatively low luminance uniformity of the low grayscale output image. While image quality deterioration problems such as staining occur, the display device according to an exemplary embodiment not only shows that image quality is improved without staining because uniformity is improved in the low-grayscale output image, but also pattern artifacts in the form of a reproduction mask pattern are not recognized. Able to know.

As described above, the display device according to an embodiment uses a grayscale reproduction mask pattern for data in a low grayscale/low luminance region where a problem of expressiveness occurs, a threshold value, a minimum value, and a detailed adjustment value for which uniformity performance is secured. By reproducing the average combination by the distributed arrangement of , it is possible to secure low gradation/low luminance uniformity performance and improve low gradation/low luminance expressiveness, and reduce the size of the reproduction mask pattern to reproduce the mask pattern in a display device with a low PPI. It can prevent the pattern artifacts of the shape from being recognized.

A display device according to the present specification can be applied to all electronic devices. For example, the display device according to the present specification includes a mobile device, a video phone, a smart watch, a watch phone, a wearable device, a foldable device, and a rollable device ( rollable device), bendable device, flexible device, curved device, electronic notebook, e-book, portable multimedia player (PMP), personal digital assistant (PDA), MP3 player, Mobile medical device, desktop PC, laptop PC, netbook computer, workstation, navigation, vehicle navigation, vehicle display, television, wallpaper display, It can be applied to a shiny signage device, a game device, a laptop computer, a monitor, a camera, a camcorder, and home appliances.

Features, structures, effects, etc. described in various examples of the above-described specification are included in at least one example of the present specification, and are not necessarily limited to only one example. Furthermore, the features, structures, effects, etc. illustrated in at least one example in this specification can be combined or modified with respect to other examples by those skilled in the art to which the technical idea of this specification belongs. Therefore, contents related to these combinations and variations should be construed as being included in the technical scope or scope of rights of this specification.

The present specification described above is not limited to the foregoing embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes are possible within a range that does not deviate from the technical spirit of the present specification. It will be clear to those who have knowledge of Therefore, the scope of the present specification is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present specification.

100: panel 200: gate driver
300: data driver 400: timing controller
500: gamma voltage generator 600: image processor
1000: display device 2000: electronic device
3000: measuring device

Claims (14)

Using a reproduction mask pattern including a minimum value and a threshold value and an adjustment value between the minimum value and the threshold value as reproduction data, converting first data less than the threshold value in an input image into the reproduction data and outputting the converted data, an image processing unit that maintains and outputs second data equal to or greater than the value;
a panel including a plurality of pixels; and
A panel driver supplying an output of the image processing unit to the panel;
The pixels displaying the reproduction data include a first pixel displaying a first luminance corresponding to the threshold value, a second pixel displaying a second luminance lower than the first luminance corresponding to the minimum value, and the control value. and a third pixel displaying a third luminance between the first luminance and the second luminance corresponding to The method of claim 1,
The threshold value is determined as a minimum gradation value or a minimum luminance value among data for which uniformity performance is secured in the uniformity measurement of the output image for each gradation displayed on the panel. The method of claim 1,
The threshold value includes a threshold value of each color determined for each color of subpixels constituting the pixels. The method of claim 1,
The control value is determined according to the first data between the minimum value and the threshold value. The method of claim 1,
In a group of N×M pixels to which the reproduction mask pattern having a size of N×M (N, M is a natural number equal to or greater than 2) pixels is applied, the number and position of the first pixel and the second pixel are determined according to the first data. A variable display device. The method of claim 5,
A display device in which positions of the first pixel, the second pixel, and the third pixel are varied within the group of N×M pixels according to the cumulative usage amount of the light emitting element included in each of the subpixels. The method of claim 1,
The size of the reproduction mask pattern and the number of the third pixels are determined in consideration of pixels per inch (PPI) of the panel and a viewing distance of the user or are controlled by a user's request signal. The method of claim 5,
A display device according to claim 1 , wherein a group of N×M pixels includes one or two of the third pixels. Using a reproduction mask pattern including a minimum value and a threshold value and an adjustment value between the minimum value and the threshold value as reproduction data, converting first data less than the threshold value in an input image into the reproduction data and outputting the converted data, maintaining and outputting second data equal to or greater than the value;
Displaying the output data on a panel;
Pixels displaying the reproduction data in the panel include a first pixel displaying a first luminance corresponding to the threshold value and a second pixel displaying a second luminance lower than the first luminance corresponding to the minimum value; and a third pixel displaying a third luminance between the first luminance and the second luminance in response to the control value. The method of claim 9,
The threshold value is determined as a minimum gradation value or a minimum luminance value among data for which uniformity performance is secured in the uniformity measurement of the output image for each gradation displayed on the panel. The method of claim 9,
The threshold value includes a threshold value of each color determined for each color of subpixels constituting the pixels. The method of claim 9,
The control value is determined according to the first data between the minimum value and the threshold value. The method of claim 9,
In a group of N×M pixels to which the reproduction mask pattern having a size of N×M (N, M is a natural number equal to or greater than 2) pixels is applied, the number and position of the first pixel and the second pixel are determined according to the first data. Method of driving a variable display device. The method of claim 13,
A method of driving a display device in which positions of the first pixel, the second pixel, and the third pixel are varied within the group of N×M pixels according to the cumulative usage amount of the light emitting element included in each of the subpixels.

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