Inspection device and display device

Abstract

An inspection apparatus and a display apparatus are provided. The inspection apparatus includes: a compensation coefficient calculator that calculates a main compensation coefficient relative to a main grayscale and a sub-compensation coefficient relative to a sub-grayscale based on a sensed image signal; a primary predictor that divides a display panel into multiple blocks, calculates a representative value for each of the multiple blocks based on the sensed image signal relative to each of the multiple blocks, and outputs a predicted compensation coefficient relative to the sub-grayscale based on the representative value corresponding to each of the multiple blocks and the main compensation coefficient; a secondary predictor that determines a flag bit based on the sub-compensation coefficient and the predicted compensation coefficient; a memory for storing the main compensation coefficient, the representative value, and the flag bit; and a control unit that outputs the main compensation coefficient, the representative value, and the flag bit stored in the memory as compensation data.

Description

Technical Field

[0001] This invention relates to a display device and an inspection apparatus for inspecting the display device. Background Technology

[0002] Multimedia electronic devices such as televisions, mobile phones, tablets, navigation devices, and game consoles have display devices for displaying images. A display device comprises multiple pixels that display the image. Even if multiple pixels are formed through the same process, each pixel may have different characteristics due to process variations. For example, even if the same grayscale image signal is provided to each pixel, each pixel may output light with different brightness levels. Summary of the Invention

[0003] The purpose of this invention is to provide an inspection device for checking characteristic deviations between pixels and a display device for performing stain compensation.

[0004] According to a feature of the present invention for achieving the aforementioned objective, the inspection apparatus includes: a compensation coefficient calculator that calculates a main compensation coefficient relative to a main grayscale and a sub-compensation coefficient relative to a sub-grayscale based on a perceived image signal; a primary predictor that divides a display panel into multiple blocks, calculates a representative value for each of the multiple blocks based on the perceived image signal relative to each of the multiple blocks, and outputs a predicted compensation coefficient relative to the sub-grayscale based on the representative value corresponding to each of the multiple blocks and the main compensation coefficient; a secondary predictor that determines a flag bit based on the sub-compensation coefficient and the predicted compensation coefficient; a memory for storing the main compensation coefficient, the representative value, and the flag bit; and a control unit that outputs the main compensation coefficient, the representative value, and the flag bit stored in the memory as compensation data.

[0005] In one embodiment, the representative value may include the average and standard deviation of each of the plurality of blocks corresponding to the main gray level and the average and standard deviation of each of the plurality of blocks corresponding to the sub-gray level.

[0006] In one embodiment, the control unit may calculate a compensation value corresponding to the flag bit based on the standard deviation corresponding to the sub-grayscale, and the compensation data may also include the compensation value.

[0007] In one embodiment, the compensation value may be determined to be a value that minimizes the mean square error relative to the predicted compensation coefficient.

[0008] In one embodiment, the compensation value may be: σ is the standard deviation relative to the sub-gray level.

[0009] In one embodiment, the flag bit may have a bit width of 1 bit, and if the prediction compensation coefficient is less than the sub-compensation coefficient, then the flag bit is 1, and the compensation value is a positive number.

[0010] In one embodiment, the flag bit may have a bit width of 1 bit, and if the prediction compensation coefficient is greater than the sub-compensation coefficient, then the flag bit is 0, and the compensation value is negative.

[0011] In one embodiment, the prediction compensation coefficient relative to the sub-gray level may be expressed by a mathematical formula. The calculation is performed so that x′ is the prediction compensation coefficient, x0, μ0 and σ0 are the main compensation coefficient, average and standard deviation of the predetermined pixel relative to the main gray level, μ1 and σ1 are the average and standard deviation of the sub-gray level, and the representative value includes the average and standard deviation relative to the main gray level and the average and standard deviation relative to the sub-gray level.

[0012] Other features of the present invention relate to a display device comprising: a display panel including a plurality of pixels respectively connected to a plurality of data lines and a plurality of scan lines; a data driving circuit for driving the plurality of data lines; a scan driving circuit for driving the plurality of scan lines; a memory for storing compensation data; and a drive controller for receiving control signals and input image signals, controlling the data driving circuit and the scan driving circuit to display an image on the display panel, and providing the data driving circuit with an image data signal that has been corrected according to the compensation data. The compensation data includes a main compensation coefficient relative to the main grayscale, a representative value relative to the main grayscale, a representative value relative to the sub-grayscale, a flag bit relative to the sub-grayscale, and a compensation value.

[0013] In one embodiment, the driving controller may output the image data signal according to the main compensation coefficient when the input image signal corresponds to the main grayscale.

[0014] In one embodiment, when the input image signal is not the main grayscale, the driving controller may calculate a prediction compensation coefficient based on the main compensation coefficient, a representative value relative to the main grayscale, a representative value relative to the sub-grayscale, the flag bit, and the compensation value, and output the image data signal based on the prediction compensation coefficient.

[0015] In one embodiment, the drive controller may, when the input image signal is the sub-grayscale, use a mathematical formula... The prediction compensation coefficient is calculated, where G′ is the prediction compensation coefficient, G0, μ0 and σ0 are the main compensation coefficient, average and standard deviation corresponding to the main gray level, and μ1 and σ1 are the average and standard deviation corresponding to the input image signal. The representative value relative to the main gray level includes the average and standard deviation corresponding to the main gray level, and the representative value relative to the sub-gray level includes the average and standard deviation corresponding to the sub-gray level.

[0016] In one embodiment, the drive controller may add the compensation value to the prediction compensation coefficient to output the image data signal.

[0017] Other features of the present invention relate to a stain compensation method for a display device that may include: receiving a perceived image signal relative to a primary grayscale and calculating a primary compensation coefficient relative to the primary grayscale; receiving a perceived image signal relative to a sub-grayscale and calculating a sub-compensation coefficient relative to the sub-grayscale; dividing a display panel into multiple blocks, calculating a representative value relative to each block, and calculating a predicted compensation coefficient relative to the sub-grayscale based on the representative value and the primary compensation coefficient; a secondary prediction step of calculating a flag bit based on the sub-compensation coefficient and the predicted compensation coefficient; outputting compensation data including the primary compensation coefficient, the representative value, and the flag bit; and compensating an input image signal based on the compensation data and displaying an image based on the compensated image signal.

[0018] In one embodiment, the representative value may include the average and standard deviation of each of the plurality of blocks corresponding to the main gray level and the average and standard deviation of each of the plurality of blocks corresponding to the sub-gray level.

[0019] In one embodiment, the step of outputting the compensation data may include calculating a compensation value corresponding to the flag bit based on the standard deviation corresponding to the sub-grayscale, and the compensation data may further include the compensation value.

[0020] In one embodiment, the compensation value may be determined to be a value that minimizes the mean square error relative to the predicted compensation coefficient.

[0021] In one embodiment, the compensation value may be: σ is the standard deviation relative to the sub-gray level.

[0022] In one embodiment, the flag bit may have a bit width of 1 bit, and the secondary prediction step of calculating the flag bit may include: if the prediction compensation coefficient is less than the sub-compensation coefficient, then the flag bit is set to 1; if the prediction compensation coefficient is greater than the sub-compensation coefficient, then the flag bit is set to 0.

[0023] In one embodiment, the prediction compensation coefficient relative to the sub-gray level may be expressed by a mathematical formula. The calculation is performed so that x′ is the prediction compensation coefficient, x0, μ0 and σ0 are the main compensation coefficient, average and standard deviation of the predetermined pixel relative to the main gray level, μ1 and σ1 are the average and standard deviation of the sub-gray level, and the representative value includes the average and standard deviation relative to the main gray level and the average and standard deviation relative to the sub-gray level.

[0024] (Invention Effects)

[0025] The inspection apparatus with the configuration described above can inspect characteristic deviations between pixels and generate compensation data corresponding to each pixel. In particular, after performing a primary prediction of the prediction compensation coefficients in a block-based manner, a secondary prediction is performed to generate flag bits for each pixel, thereby minimizing memory usage. Attached Figure Description

[0026] Figure 1 This is a diagram illustrating an inspection system for inspecting a display device according to an embodiment of the present invention.

[0027] Figure 2 This is a block diagram illustrating the configuration of an inspection device.

[0028] Figure 3 An illustrative representation of the compensation coefficients and predicted brightness involved in the brightness of a pixel perceived in the inspection device.

[0029] Figure 4 The illustrative representation shows the prediction compensation coefficient and sub-compensation coefficient predicted in the inspection device.

[0030] Figure 5 This represents an example of dividing the display panel into multiple blocks.

[0031] Figure 6 illustrative representation in Figure 2 The master compensation coefficients are stored in the memory shown.

[0032] Figure 7 illustrative representation in Figure 2 The representative value stored in the memory shown.

[0033] Figure 8 illustrative representation in Figure 2 The flag bits are stored in the memory shown.

[0034] Figure 9 It is an illustrative graph representing the probability density of the error relative to the prediction compensation coefficient and the sub-compensation coefficient.

[0035] Figure 10 It is an illustrative graph representing the probability density and compensation value of the error relative to the prediction compensation coefficient and the sub-compensation coefficient.

[0036] Figure 11 The illustration shows a display device according to an embodiment of the present invention.

[0037] Figure 12 This is a flowchart illustrating an illustrative method for stain compensation in a display device.

[0038] (Symbol Explanation)

[0039] DD: Display device; DP: Display panel; CAM: Camera; TD: Inspection device; 110: Compensation coefficient calculator; 120: Primary predictor; 130: Secondary predictor; 140: Memory; 150: Control unit; 210: Drive controller; 220: Data drive circuit; 230: Scan drive circuit; 250: Memory. Detailed Implementation

[0040] In this specification, when it is mentioned that a certain component (or region, layer, part, etc.) is located on, connected to or combined with other components, it means that it can be directly configured / connected / combined with other components, or a third component can be configured therein.

[0041] The same symbols refer to the same constituent elements. Furthermore, in the accompanying drawings, the thickness, proportions, and dimensions of the constituent elements are exaggerated for the purpose of effectively illustrating the technical content. "And / or" includes all combinations that can define the related constituent elements.

[0042] The terms "first," "second," etc., can be used to describe various constituent elements, but the constituent elements described should not be limited to these terms. These terms are used only to distinguish one constituent element from others. For example, without departing from the scope of this invention, a first constituent element can be named a second constituent element, and similarly, a second constituent element can be named a first constituent element. Singular expressions include plural expressions unless explicitly stated otherwise in the text.

[0043] Additionally, terms such as "below," "on the lower side," "above," and "on the upper side" are used to explain the connection relationships between the components in the diagram. These terms are relative concepts and are explained based on the direction shown in the diagram.

[0044] Terms such as “including” or “having” should be understood as referring to the presence of features, figures, steps, operations, constituent elements, components, or combinations thereof as recorded in the instruction manual, and do not preclude the existence or additional possibilities of one or more other features, figures, steps, operations, constituent elements, components, or combinations thereof.

[0045] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) shall have the same meaning as commonly understood by those skilled in the art. Furthermore, terms defined in commonly used dictionaries shall be interpreted as having a meaning consistent with the relevant technical context, and shall not be interpreted as having an idealized or overly formal meaning unless explicitly defined in this application.

[0046] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings.

[0047] Figure 1 This is a diagram illustrating an inspection system for inspecting a display device according to an embodiment of the present invention.

[0048] Reference Figure 1 The inspection system includes a display device (DD), a camera (CAM), and an inspection device (TD). Figure 1 In this paper, a television set is shown as an example of a display device DD, but the present invention is not limited thereto. The display device DD can be used not only in large electronic equipment such as television sets or external billboards, but also in small and medium-sized electronic equipment such as personal computers, laptops, self-service machines, car navigation units, cameras, tablet PCs, smartphones, PDAs (Personal Digital Assistants), PMPs (Portable Multimedia Players), game consoles, and watch-type electronic devices.

[0049] like Figure 1 As shown, the camera (CAM) captures an image displayed on the display panel (DP) of the display device (DD) and provides the perceived image signal (IM) to the inspection device (TD). The inspection device (TD) senses the brightness of each pixel on the display device (DD) based on the perceived image signal (IM) provided by the camera (CAM) and generates compensation data (CP_DATA) relative to the sensed brightness. The compensation data (CP_DATA) can be provided to the display device (DD). The display device (DD) can correct the image signal based on the compensation data (CP_DATA) and display the corrected image signal.

[0050] exist Figure 1The diagram illustrates a scenario where the camera CAM and the inspection device TD are independent devices, but the camera CAM and the inspection device TD can also be a single device. That is, the camera CAM can be a component of the inspection device TD.

[0051] Figure 2 This is a block diagram illustrating the configuration of the inspection device TD.

[0052] Reference Figure 1 and Figure 2 The inspection device TD includes a compensation coefficient arithmetic unit 110, a primary predictor 120, a secondary predictor 130, a memory 140, and a control unit 150.

[0053] The compensation coefficient calculator 110 calculates the main compensation coefficient M_CV relative to the main gray level and the sub-compensation coefficient S_CV relative to the sub-gray level based on the perceived image signal IM.

[0054] The primary predictor 120 divides the display panel DP of the display device DD into multiple blocks, and calculates a representative value RV for each of the multiple blocks based on the perceived image signal IM relative to each of the multiple blocks. Furthermore, the primary predictor 120 outputs a prediction compensation coefficient P_CV relative to the sub-grayscale based on the representative value RV corresponding to each of the multiple blocks and the main compensation coefficient M_CV.

[0055] The secondary predictor 130 determines the flag FG based on the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV.

[0056] The memory 140 stores the main compensation coefficient M_CV from the compensation coefficient arithmetic unit 110, the representative value RV from the primary predictor 120, and the flag bit FG from the secondary predictor 130.

[0057] The control unit 150 outputs the main compensation coefficient M_CV, representative value RV, and flag bit FG stored in the memory 140 as compensation data CP_DATA. The control unit 150 can control the operation of the compensation coefficient calculator 110, the primary predictor 120, and the secondary predictor 130. Furthermore, the control unit 150 can control the operation of the camera CAM.

[0058] The following details the specific operation of each component of the inspection device TD.

[0059] Figure 3 The example illustrates the compensation coefficients and predicted brightness involved in the brightness of a pixel perceived in the inspection device TD.

[0060] Reference Figure 1 , Figure 2 and Figure 3, The illustrated display device DD includes a plurality of pixels. Even if the plurality of pixels are formed through the same process, each pixel may have different characteristics due to process variations or the like. For example, even when the same grayscale image signal is provided to each pixel, each pixel may output light of different brightnesses.

[0061] For example, when the display device DD provides image data signals corresponding to the main grayscale (e.g., a grayscale) to each pixel, the camera CAM can sense an image of different brightnesses in each pixel according to the characteristics of each pixel. The compensation coefficient calculator 110 in the inspection device TD can generate different compensation coefficients such as M1, M2, M3, and M4 based on the image signal IM from the camera CAM.

[0062] Generally, pixels have a certain tendency with respect to grayscale. For example, a pixel that outputs a brightness lower than the desired brightness at the M grayscale of the main grayscale (hereinafter referred to as M) may output a brightness lower than the desired brightness at the A grayscale (hereinafter referred to as A) of the sub-grayscale lower than the main grayscale M, and may also output a brightness lower than the desired brightness at the B grayscale (hereinafter referred to as B) of the sub-grayscale higher than the main grayscale M.

[0063] As another example, a pixel that outputs a brightness higher than the desired brightness at the main grayscale M may output a brightness higher than the desired brightness at the sub-grayscale A lower than the main grayscale M, and may also output a brightness higher than the desired brightness at the sub-grayscale B higher than the main grayscale M.

[0064] The compensation coefficient can be set to a low value when the brightness of the pixel is higher than the desired brightness, and can be set to a high value when the brightness of the pixel is lower than the desired brightness. In Figure 3 In the example shown, each grayscale is A < M < B, and the respective main compensation coefficients with respect to the main grayscale M are M1 < M2 < M3 < M4. The respective predicted compensation coefficients with respect to the sub-grayscale A are A1 < A2 < A3 < A4, and the respective predicted compensation coefficients with respect to the sub-grayscale B are B1 < B2 < B3 < B4.

[0065] That is, for a pixel with a compensation coefficient of M1 at the M grayscale, the compensation coefficient can be predicted to be A1 at the A grayscale and B1 at the B grayscale. For a pixel with a compensation coefficient of M2 at the M grayscale, the compensation coefficient can be predicted to be A2 at the A grayscale and B2 at the B grayscale. For a pixel with a compensation coefficient of M3 at the M grayscale, the compensation coefficient can be predicted to be A3 at the A grayscale and B3 at the B grayscale. For a pixel with a compensation coefficient of M4 at the M grayscale, the compensation coefficient can be predicted to be A4 at the A grayscale and B4 at the B grayscale.

[0066] The compensation coefficient calculator 110 of the inspection device TD calculates the main compensation coefficient M_CV relative to the main gray level M and the sub-compensation coefficient S_CV relative to the sub-gray level B based on the perceived image signal IM. Furthermore, the primary predictor 120 of the inspection device TD can calculate the prediction compensation coefficient P_CV relative to the B gray level based on the main compensation coefficient M_CV.

[0067] Figure 4 The example represents the prediction compensation coefficient and sub-compensation coefficient predicted in the inspection device TD.

[0068] Reference Figure 2 and Figure 4 The B1, B2, B3, B4 values ​​output from the primary predictor 120 of the inspection device TD as prediction compensation coefficients P_CV relative to the sub-grayscale B and the S1, S2, S3, S4 values ​​output from the compensation coefficient calculator 110 as sub-compensation coefficients S_CV may be inconsistent. The secondary predictor 130 may output a flag FG to reduce the error between the prediction compensation coefficients P_CV and the sub-compensation coefficients S_CV.

[0069] Figure 5 This represents an example of dividing the display panel into multiple blocks.

[0070] Reference Figure 5 The display panel (DP) can be divided into blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46. Figure 5 The illustration shows a display panel DP that is divided into six blocks in the first direction DR1 and four blocks in the second direction DR2, but the number of blocks dividing the display panel DP can be varied in various ways.

[0071] Reference Figure 2 , Figure 3 and Figure 5 The primary predictor 120 divides the display panel DP of the display device DD into multiple blocks and calculates a representative value RV for each of the multiple blocks based on the perceived image signal IM relative to each of the multiple blocks. In this embodiment, the representative value RV is the average and standard deviation of each of the blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46. The representative value RV is not limited to the average and can be the median or the mode.

[0072] Blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 can each include 180 pixels in the first direction DR1 and 100 pixels in the second direction DR2. The number of pixels included in a block (i.e., the size of each block) can be varied in various ways.

[0073] Figure 6 illustrative representation in Figure 2 The master compensation coefficient M_CV is stored in memory 140 shown.

[0074] exist Figure 6 Only those shown in the text are related to... Figure 5 The main compensation coefficient M_CV(BK11) corresponding to block BK11 shown is shown, but the main compensation coefficients corresponding to the remaining blocks BK12-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 can also be stored in memory 140.

[0075] Reference Figure 6 The main compensation coefficient M_CV(BK11) can include the compensation coefficients corresponding to 180 pixels in the first direction DR1 and 100 pixels in the second direction DR2 within block BK11. The compensation coefficient can be the difference value Δg between the main gray level M and the perceived brightness.

[0076] Figure 7 illustrative representation in Figure 2 The representative value RV is stored in the memory 140 shown.

[0077] exist Figure 7 Only those shown in the text are related to... Figure 5 The representative value RV(BK11) corresponding to block BK11 shown can also be stored in memory 140, but the representative values ​​corresponding to the remaining blocks BK12-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 can also be stored in memory 140.

[0078] The primary predictor 120 calculates a representative value corresponding to each of the plurality of blocks. The representative value RV(BK11) corresponding to block BK11 may include the average ME_M and standard deviation SD_M corresponding to the main gray level M, the average ME_A and standard deviation SD_A corresponding to the sub-gray level A, and the average ME_B and standard deviation SD_B corresponding to the sub-gray level B.

[0079] exist Figure 7 The diagram illustrates the storage of representative values ​​for two sub-grayscale values ​​corresponding to a block BK11, but it is not limited to this. The number of sub-grayscale values ​​corresponding to a block BK11 can be varied in various ways.

[0080] The primary predictor 120 outputs the prediction compensation coefficient P_CV corresponding to each pixel in the block, based on the main compensation coefficient M_CV and representative value RV corresponding to blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 respectively.

[0081] For example, the prediction compensation coefficient P_CV can be calculated using the following mathematical formula 1.

[0082] [Mathematical Expression 1]

[0083]

[0084] In mathematical formula 1, x0, μ0, and σ0 are the principal compensation coefficients M_CV, average, and standard deviation corresponding to the principal gray level of the predetermined pixel, and x′, μ1, and σ1 are the prediction compensation coefficients P_CV, average, and standard deviation corresponding to the sub-gray level of the predetermined pixel.

[0085] The secondary predictor 130 determines the flag FG based on the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV.

[0086] As before Figure 4 As explained in the document, the B1, B2, B3, and B4 output from the primary predictor 120 as prediction compensation coefficients P_CV relative to the sub-grayscale B and the S1, S2, S3, and S4 output from the compensation coefficient calculator 110 as sub-compensation coefficients S_CV may be inconsistent.

[0087] The secondary predictor 130 determines a flag bit FG corresponding to the difference between the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV. The flag bit FG output from the secondary predictor 130 can be stored in the memory 140.

[0088] like Figure 5 As shown, the primary predictor 120 performs block-wise prediction as follows: it divides the display panel DP into blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46, calculates the representative value relative to each block, and outputs the prediction compensation coefficient P_CV based on the representative value.

[0089] The secondary predictor 130 performs pixel-wise prediction as follows: it calculates the flag bit B corresponding to each pixel based on the prediction compensation coefficient P_CV from the primary predictor 120.

[0090] Figure 8 illustrative representation in Figure 2 The flag bit FG is stored in the memory 140 shown.

[0091] exist Figure 8 Only those shown in the text are related to... Figure 5 The flag bit FG(BK11) corresponding to block BK11 shown can also be stored in memory 140, but the flag bits corresponding to the remaining blocks BK12-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 can also be stored in memory 140.

[0092] Refer to Figure 2 and Figure 8 Figure 8 , the flag bit FG(BK11) may include flag bits B corresponding to 180 pixels in the first direction DR1 and 100 pixels in the second direction DR2 within the block BK11, respectively. The bit width of the flag bit B may be 1 bit or 2 bits or more.

[0093] When the bit width of the flag bit B corresponding to a predetermined pixel is 1 bit, the flag bit B may be 1 or 0 according to the difference between the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV.

[0094] For example, if the prediction compensation coefficient P_CV is 10 and the sub-compensation coefficient S_CV calculated by the compensation coefficient calculator 110 is 14, then the compensation value β is added to the prediction compensation coefficient P_CV, that is, 10 + β. As described above, if the prediction compensation coefficient P_CV is less than the sub-compensation coefficient S_CV (P_CV < S_CV) (i.e., the compensation value β is positive), the flag bit B may be 1.

[0095] On the contrary, if the prediction compensation coefficient P_CV is 10 and the sub-compensation coefficient S_CV calculated by the compensation coefficient calculator 110 is 5, then the compensation value β is subtracted from the prediction compensation coefficient P_CV, that is, 10 - β. As described above, if the prediction compensation coefficient P_CV is greater than the sub-compensation coefficient S_CV (P_CV > S_CV) (i.e., the compensation value β is negative), the flag bit B may be 0.

[0096] Figure 9 is an illustrative graph showing the probability density of the error between the prediction compensation coefficient P_CV and the sub-compensation coefficient S_CV.

[0097] Refer to Figure 2 and Figure 9 Figure 9 , if the sub-compensation coefficient S_CV with respect to the sub-gray scale B is set as Δg B and the prediction compensation coefficient P_CV is set as Δg′ B B , then the error N between the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV is as shown in the following mathematical formula 2.

[0098] [Mathematical formula 2]

[0099]

[0100] In Figure 9In the example shown, if the probability density function relative to the error N is obtained, the probability density function can have the characteristics of a Gaussian distribution. In this case, if the optimal compensation value (+β, -β) is found, the final compensation value relative to the sub-gray level can be calculated by adding the compensation value (+β, -β) corresponding to the flag bit B to the predicted compensation coefficient P_CV.

[0101] Final compensation value Δg″ B It can be determined according to the following mathematical formula 3.

[0102] [Mathematical Expression 3]

[0103]

[0104] To determine the optimal compensation value β, it should be obtained using the value that minimizes the mean squared error (MSE).

[0105] Equation 4 is the mean square error (MSE) used to calculate the optimal compensation value β.

[0106] In the following explanation, x is the prediction compensation coefficient P_CV relative to sub-grayscale B, and σ is the standard deviation relative to sub-grayscale B.

[0107] [Mathematical Expression 4]

[0108]

[0109] In mathematical formula 4, f G (x) is as shown in mathematical formula 5.

[0110] [Mathematical Expression 5]

[0111]

[0112] In mathematical formula 4, When M1 is defined, M1 is as shown in mathematical formula 6.

[0113] [Mathematical Expression 6]

[0114]

[0115] In mathematical formula 6, Let M be the name of the project. 1A And when y = x / σ is used instead, M 1A For example, mathematical formula 7.

[0116] [Mathematical Expression 7]

[0117]

[0118] In mathematical expression 7, if If it is 0, then it can be

[0119] In mathematical formula 6, Let M be the name of the project. 1B And when y = x / σ is used instead, M 1B For example, mathematical formula 8.

[0120] [Mathematical Expression 8]

[0121]

[0122] In mathematical formula 6, Let M be the name of the project. 1C And when y = x / σ is used instead, M 1C For example, mathematical formula 9.

[0123] [Mathematical Expression 9]

[0124]

[0125] In mathematical formula 4, When M2 is defined as M2, M2 is as shown in mathematical formula 10.

[0126] [Mathematical Expression 10]

[0127]

[0128] In mathematical formula 10, if... Let M be the name of the project. 2A Then M 2A For example, mathematical formula 11.

[0129] [Mathematical Expression 11]

[0130]

[0131] In mathematical formula 11, if If it is 0, then

[0132] In mathematical formula 10, if... Let M be the name of the project. 2B Then M 2B For example, mathematical formula 12.

[0133] [Mathematical Expression 12]

[0134]

[0135] In mathematical formula 10, if... Let M be the name of the project. 2C Then M 2C For example, mathematical formula 13.

[0136] [Mathematical Expression 13]

[0137]

[0138] If we apply M1 of mathematical formula 6, which is derived from mathematical formulas 7 to 9, and M2 of mathematical formula 10, which is derived from mathematical formulas 11 to 13, to mathematical formula 4, then the mean square error (MSE) can be sorted out as in mathematical formula 14.

[0139] [Mathematical Expression 14]

[0140]

[0141] According to mathematical formula 14, in When the mean square error (MSE) reaches its minimum value,

[0142] That is, the compensation value β is set to That is appropriate.

[0143] Figure 2 The control unit 150 shown outputs compensation data CP_DATA based on the main compensation coefficient M_CV, the representative value RV, and the flag bit FG stored in the memory 140. The control unit 150 can calculate the compensation value β based on the standard deviation σ1 (refer to mathematical formula 1) corresponding to the sub-gray level B included in the representative value RV, and include the compensation value β in the compensation data CP_DATA.

[0144] exist Figures 4 to 9 The text only describes the sub-compensation coefficient S_CV, prediction compensation coefficient P_CV, representative value RV, and flag bit FG corresponding to sub-gray level B. However, the sub-compensation coefficient, prediction compensation coefficient, representative value, and flag bit can also be obtained for sub-gray level A in the same way.

[0145] In addition, the inspection device TD can inspect Figure 3 Other sub-grayscales besides A and B are also calculated in the same way to obtain sub-compensation coefficients, prediction compensation coefficients, representative values, and flag bits. That is, the inspection device TD can calculate the main compensation coefficient relative to a main grayscale and store the flag bits and representative values ​​relative to more than one sub-grayscale in the memory 140.

[0146] On the other hand, the peak signal-to-noise ratio (PSNR) is as shown in equation 15.

[0147] [Mathematical Expression 15]

[0148]

[0149] If the compensation value β derived from mathematical formulas 4 to 14 is applied to the peak signal-to-noise ratio (PSNR), the calculated peak signal-to-noise ratio PSNR* is as shown in mathematical formula 16.

[0150] [Mathematical Expression 16]

[0151]

[0152] That is, it can be seen that the calculated peak signal-to-noise ratio (PSNR)* under the applicable compensation value β is theoretically about 4.4 dB higher than the peak signal-to-noise ratio (PSNR).

[0153] Figure 10 This is an illustrative graph representing the probability density and compensation value of the error relative to the prediction compensation coefficient P_CV and the sub-compensation coefficient S_CV.

[0154] Reference Figure 2 and Figure 10 The flag bit B included in the flag bit FG output from the secondary predictor 130 can have a bit width of 2 bits. In this case, the compensation value can be any one of the four compensation values: +α, +β, -α, and -β.

[0155] When the bit width of the flag bit B corresponding to the predetermined pixel is 2 bits, the flag bit B can be any one of 00, 01, 10 and 11 according to the difference between the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV.

[0156] For example, if the prediction compensation coefficient P_CV is 10, and the sub-compensation coefficient S_CV calculated by the compensation coefficient calculator 110 is 12, then the compensation value α is added to the prediction compensation coefficient P_CV, i.e., 10 + α. In this case, the flag bit B can be 10.

[0157] If the prediction compensation coefficient P_CV is 10 and the sub-compensation coefficient S_CV is 14, then the compensation value β is added to the prediction compensation coefficient P_CV, i.e., 10 + β. In this case, the flag B can be 11.

[0158] If the prediction compensation coefficient P_CV is 10 and the sub-compensation coefficient S_CV is 8, then the compensation value α is subtracted from the prediction compensation coefficient P_CV, i.e., 10-α. In this case, the flag bit B can be 0 or 1.

[0159] If the prediction compensation coefficient P_CV is 10 and the sub-compensation coefficient S_CV is 5, then the compensation value β is subtracted from the prediction compensation coefficient P_CV, i.e., 10-β. In this case, the flag B can be 00.

[0160] Similarly, the optimal values ​​of the compensation values ​​+α, +β, -α, and -β are obtained and added to the prediction compensation coefficient P_CV along with the compensation values ​​+α, +β, -α, and -β corresponding to the flag bit B, thereby calculating the final compensation value relative to the sub-gray level.

[0161] Figure 11 The illustration shows a display device according to an embodiment of the present invention.

[0162] Reference Figure 11 The display device DD includes a display panel DP, a drive controller 210, a data drive circuit 220, and a memory 250.

[0163] The display panel DP includes a scan drive circuit 240, multiple pixels PX, multiple data lines DL1-DLm, and multiple scan lines SL1-SLn. The multiple pixels PX are connected to the corresponding data lines in the multiple data lines DL1-DLm, and to the corresponding scan lines in the multiple scan lines SL1-SLn.

[0164] A display panel (DP) is a panel used to display images. It can be one of various types of display panels, such as LCD (Liquid Crystal Display Panel), Electrophoretic Display Panel, OLED (Organic Light Emitting Diode Panel), LED (Light Emitting Diode Panel), ElectroLuminescent Display Panel, FED (Field Emission Display Panel), SED (Surface-conduction Electron-emitter Display Panel), PDP (Plasma Display Panel), and CRT (Cathode Ray Tube) display panels.

[0165] The drive controller 210 receives an input image signal RGB from an external source and a control signal CTRL for controlling the display of the input image signal RGB. For example, the control signal CTRL may include at least one synchronization signal and at least one clock signal. The drive controller 210 provides the data drive circuit 220 with an image data signal DAS that processes the input image signal RGB into an image suitable for the operating conditions of the display panel DP. Based on the control signal CTRL, the drive controller 210 provides a first control signal DCS to the data drive circuit 220 and a second control signal SCS to the scan drive circuit 240. The first control signal DCS may include a horizontal synchronization start signal, a clock signal, and a line latch signal; the second control signal SCS may include a vertical synchronization start signal and an output strobe signal.

[0166] The data driving circuit 220 can respond to the first control signal DCS and the image data signal DAS from the drive controller 210, and output grayscale voltages for driving multiple data lines DL1-DLm. In an exemplary embodiment, the data driving circuit 220 can be implemented using an integrated circuit (IC) and can be directly mounted to a predetermined area of ​​the display panel DP or mounted to another printed circuit board via COF (chip on film) for electrical connection to the display panel DP. In other embodiments, the data driving circuit 220 can be formed on the display panel DP using the same processes as the driving circuit for the pixel PX.

[0167] The scan driving circuit 240 drives multiple scan lines SL1-SLn in response to a second control signal SCS from the drive controller 210. In an exemplary embodiment, the scan driving circuit 240 can be formed on the display panel DP using the same processes as the driving circuit for the pixel PX, but is not limited thereto. For example, the scan driving circuit 240 can be implemented using an integrated circuit (IC) and can be directly mounted to a predetermined area of ​​the display panel DP or mounted to another printed circuit board via COF (chipon film) for electrical connection to the display panel DP.

[0168] Memory 250 stores compensation data CP_DATA. From Figure 2 The inspection device TD shown provides compensation data CP_DATA stored in memory 250. The compensation data CP_DATA may include the main compensation coefficient M_CV, the representative value RV, the flag bit FG, and the compensation value β.

[0169] The drive controller 210 can correct the input image signal RGB provided from the outside according to the compensation data CP_DATA stored in the memory 250, and provide the image data signal DAS to the data drive circuit 220.

[0170] If the input image signal RGB provided from the outside corresponds to the dominant gray level M (refer to...) Figure 3 If the input image signal RGB provided from the outside corresponds to the sub-grayscale B (refer to...), then the drive controller 210 can correct the input image signal RGB according to the main compensation coefficient M_CV corresponding to the main grayscale M. Figure 3 If the drive controller 210 can correct the input image signal RGB according to the representative value RV, the flag bit FG and the compensation value β, then the drive controller 210 can correct the input image signal RGB according to the representative value RV, the flag bit FG and the compensation value β.

[0171] First, the drive controller 210 calculates the prediction compensation coefficient G′ according to mathematical formula 17 using a method similar to mathematical formula 1.

[0172] [Mathematical Expression 17]

[0173]

[0174] In mathematical formula 17, G0, μ0, and σ0 are the principal compensation coefficients M_CV, average, and standard deviation corresponding to the principal grayscale of the predetermined pixel, and G′, μ1, and σ1 are the prediction compensation coefficients, average, and standard deviation corresponding to the input image signal RGB relative to the predetermined pixel.

[0175] In mathematical formula 17, the master compensation coefficient G0 and representative values ​​μ0, σ0, μ1, σ1 are provided from memory 250.

[0176] The drive controller 210 can add the compensation value β provided from the memory 250 to the calculated prediction compensation coefficient G′ as in mathematical formula 18, thereby generating the image data signal DAS.

[0177] [Mathematical Expression 18]

[0178] DAS=G′+β

[0179] If the input image signal RGB provided from the outside corresponds to the sub-grayscale A (refer to...) Figure 3 If the drive controller 210 can correct the input image signal RGB according to the representative value RV, the flag bit FG and the compensation value β, then the drive controller 210 can correct the input image signal RGB according to the representative value RV, the flag bit FG and the compensation value β.

[0180] If the input image signal RGB provided from the outside does not correspond to the main gray level M or the sub-gray level B, the drive controller 210 can calculate the representative value corresponding to the gray level of the input image signal RGB based on the representative values ​​ME_M and SD_M of the main gray level M and the representative values ​​ME_B and SD_B of the sub-gray level B. For example, the drive controller 210 can calculate the representative value corresponding to the gray level of the input image signal RGB using linear interpolation or spatial interpolation. Furthermore, the drive controller 210 can apply the calculated representative value to mathematical formulas 17 and 18 to generate the image data signal DAS.

[0181] The inspection device TD described above can provide the display device DD with the main compensation coefficient M_CV relative to the main gray level of each pixel, the representative value RV relative to each block, the flag bit FG, and the compensation value β as compensation data CP_DATA.

[0182] The display device DD can generate compensation coefficients for all gray levels relative to each of all pixels using the main compensation coefficient M_CV, the representative value RV relative to each block, the flag bit FG, and the compensation value β. Therefore, compared to storing the compensation coefficients for all gray levels relative to each of all pixels in the memory 250 of the display device DD, the size of the memory 250 can be minimized.

[0183] Figure 12 This is a flowchart illustrating an illustrative method for stain compensation in a display device.

[0184] Reference Figure 2 , Figure 11 and Figure 12 The camera CAM captures an image displayed on the display panel DP of the display device DD, and provides the perceived image signal IM to the inspection device TD.

[0185] The compensation coefficient calculator 110 of the inspection device TD receives the relative main grayscale M (reference) from the camera CAM. Figure 3 The perceived image signal IM (step S100).

[0186] The compensation coefficient calculator 110 calculates the main compensation coefficient M_CV relative to each pixel based on the perceived image signal IM (refer to...). Figure 6 (Step S110). The main compensation coefficient M_CV is stored in memory 140.

[0187] The compensation coefficient calculator 110 of the inspection device TD receives the value relative to the sub-grayscale B (reference) from the camera CAM. Figure 3 The perceived image signal IM (step S120).

[0188] The compensation coefficient calculator 110 calculates the sub-compensation coefficient S_CV based on the perceived image signal IM (step S130).

[0189] The primary predictor 120 divides the display panel DP into blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 (see reference). Figure 5 Based on the perceived image signal IM relative to each of the blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46, the representative value RV of each block BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 is calculated. Furthermore, the primary predictor 120 performs a primary prediction (step S140) based on the representative value RV corresponding to each of the multiple blocks BK11-BK16, BK21-BK26, BK31-BK36, and BK41-BK46 and the main compensation coefficient M_CV, calculating the prediction compensation coefficient P_CV relative to the sub-grayscale. The representative value RV may include the average ME_M and standard deviation SD_M corresponding to the main grayscale M and the average ME_B and standard deviation SD_B corresponding to the sub-grayscale B (refer to...). Figure 7 ).

[0190] The secondary predictor 130 performs the function of determining the flag bit B of each pixel based on the sub-compensation coefficient S_CV and the prediction compensation coefficient P_CV (see reference). Figure 8 The secondary prediction of ) (step S150). The flag bit FG, including the flag bit B, can be stored in the memory 140.

[0191] The control unit 150 outputs compensation data CP_DATA based on the main compensation coefficient M_CV, the representative value RV, and the flag bit FG stored in the memory 140 (step S160). The control unit 150 calculates the compensation value β based on the standard deviation σ1 corresponding to the sub-grayscale B included in the representative value RV (refer to mathematical formula 1), and can include the compensation value β in the compensation data CP_DATA.

[0192] The drive controller 210 of the display device DD can correct the input image signal RGB provided from the outside according to the compensation data CP_DATA stored in the memory 250, and provide the image data signal DAS to the data drive circuit 220 (S170).

[0193] Multiple pixels may have different characteristics due to process variations, etc. Even if an image signal of the same grayscale is provided to each pixel, each pixel may output light with different brightness. The display device DD of the present invention can output an image data signal DAS that corrects the RGB values ​​of the input image signal according to the compensation data CP_DATA stored in the memory 250. Therefore, it is possible to prevent the user from recognizing stains caused by the characteristics of the pixels.

[0194] The above description refers to the embodiments. However, those skilled in the art should understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention as set forth in the claims. Furthermore, the embodiments disclosed in this invention are not intended to limit the technical concept of the invention; rather, it should be understood that all technical concepts falling within the scope of the claims and their equivalents are included within the scope of the claims.

Claims

1. An inspection apparatus comprising: a compensation coefficient calculator that calculates a main compensation coefficient with respect to a main gray scale and a sub compensation coefficient with respect to a sub gray scale from a perceived image signal; a primary predictor that divides a display panel into a plurality of blocks, calculates a representative value of each of the plurality of blocks from the perceived image signal with respect to each of the plurality of blocks, and outputs a predicted compensation coefficient with respect to the sub gray scale from the representative value corresponding to each of the plurality of blocks and the main compensation coefficient; a secondary predictor that determines a flag from the sub compensation coefficient and the predicted compensation coefficient; a memory that stores the main compensation coefficient, the representative value, and the flag; and a control section that outputs the main compensation coefficient, the representative value, the flag, and a compensation value stored in the memory as compensation data, wherein the control section calculates the compensation value corresponding to the flag from a standard deviation corresponding to the sub gray scale.

2. The inspection apparatus according to claim 1, wherein the representative value includes an average and a standard deviation corresponding to the main gray scale of each of the plurality of blocks and an average and a standard deviation corresponding to the sub gray scale of each of the plurality of blocks.

3. The inspection apparatus according to claim 1, wherein the compensation value is determined as a value that can minimize a mean square error with respect to the predicted compensation coefficient.

4. The inspection apparatus according to claim 3, wherein The compensation value is σ is the standard deviation with respect to the sub-gray scale.

5. The inspection apparatus according to claim 1, wherein a bit width of the flag is 1 bit, the flag is 1 and the compensation value is a positive number if the predicted compensation coefficient is smaller than the sub compensation coefficient.

6. The inspection apparatus according to claim 1, wherein a bit width of the flag is 1 bit, the flag is 0 and the compensation value is a negative number if the predicted compensation coefficient is larger than the sub compensation coefficient.

7. The inspection apparatus according to claim 1, wherein The prediction compensation coefficient with respect to the sub-gray scale is calculated by a mathematical expression , x' is the predicted compensation coefficient, x0, μ0, and σ0 are the main compensation coefficient, an average, and a standard deviation with respect to the main gray scale of a predetermined pixel, μ1 and σ1 are an average and a standard deviation with respect to the sub gray scale, the representative value includes an average and a standard deviation with respect to the main gray scale and an average and a standard deviation with respect to the sub gray scale.

8. The inspection apparatus according to claim 1, wherein the representative value of the perceived image signal can be calculated by a linear interpolation method or a spatial interpolation method if the image signal does not correspond to the main gray scale or the sub gray scale.

9. A display apparatus comprising: a display panel including a plurality of pixels connected to a plurality of data lines and a plurality of scan lines, respectively; a data drive circuit that drives the plurality of data lines; a scan drive circuit that drives the plurality of scan lines; a memory that stores compensation data; and a control section that outputs the compensation data. a drive controller receiving a control signal and an input image signal, controlling the data drive circuit and the scan drive circuit so that an image is displayed on the display panel, and supplying an image data signal, in which the input image signal is corrected according to the compensation data, to the data drive circuit, the compensation data including a main compensation coefficient with respect to a main gray scale, a representative value with respect to the main gray scale, a representative value with respect to a sub gray scale, a flag with respect to the sub gray scale, and a compensation value, the drive controller calculating the compensation value corresponding to the flag according to a standard deviation corresponding to the sub gray scale.

10. The display device according to claim 9, wherein the drive controller outputs the image data signal according to the main compensation coefficient when the input image signal corresponds to the main gray scale.

11. The display device according to claim 9, wherein the drive controller calculates a predicted compensation coefficient according to the main compensation coefficient, the representative value with respect to the main gray scale, the representative value with respect to the sub gray scale, the flag, and the compensation value when the input image signal is not the main gray scale, and outputs the image data signal according to the predicted compensation coefficient.

12. The display device according to claim 11, wherein The drive controller calculates the prediction compensation coefficient by mathematical expression when the input image signal is the sub-gray scale. G' is the predicted compensation coefficient, G0, μ0, and σ0 are the main compensation coefficient, the mean, and the standard deviation corresponding to the main gray scale, μ1 and σ1 are the mean and the standard deviation corresponding to the input image signal, the representative value with respect to the main gray scale includes the mean and the standard deviation corresponding to the main gray scale, and the representative value with respect to the sub gray scale includes the mean and the standard deviation corresponding to the sub gray scale.

13. The display device according to claim 12, wherein the drive controller adds the compensation value to the predicted compensation coefficient to output the image data signal.

14. The inspection device according to claim 9, wherein the drive controller can calculate a representative value of a perceived image signal by a linear interpolation method or a spatial interpolation method when the image signal does not correspond to the main gray scale or the sub gray scale.

Images