Display device and signal processing method

Abstract

To obtain compensation data with less sensing operation and a smaller amount of memory use.SOLUTION: A display device in which each pixel includes a driving TFT connected to a current driving type display element and a switching TFT for controlling the amount of current flowing in the driving TFT includes a driving unit that applies measurement voltage, which varies depending on pixels, to a control electrode of each driving TFT of a plurality of pixels provided adjacent to each other, a sensing unit that samples and senses the amount of current flowing in each driving TFT of the pixels by applying the measurement voltage to the control electrode, a calculation unit that obtains the electric characteristic of the driving TFT of one pixel among the pixels by using the measurement voltage and the amount of current flowing in each driving TFT of the pixels, and a data compensation unit that converts the image data about the one pixel on the basis of the change in the electric characteristic of the driving TFT.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a display device and a signal processing method, and more particularly to an active matrix type display device in which current-driven display elements are arranged in a matrix, and a signal processing method for compensating for image quality thereof. [Background technology]

[0002] In recent years, active matrix organic EL display devices have been actively developed. The self-emitting organic EL elements used in organic EL display devices have the advantages of fast response speed, good contrast, and a wide viewing angle. In an active matrix organic EL display device, pixels each including an organic EL element are arranged in a matrix, and a voltage corresponding to a video signal level is applied to the pixels to adjust the brightness by controlling the drive current.

[0003] Each pixel contains a driving thin-film transistor (driving TFT) to control the driving current flowing through the organic EL element. There is a problem that the electrical characteristics of the driving TFT, such as threshold voltage and mobility, vary over time depending on the driving environment, etc. For this reason, even if the same data voltage is applied, the brightness becomes non-uniform due to the difference in the amount of current, and image quality degradation such as uneven brightness and burn-in becomes visible. To solve this problem, an image quality compensation technology is known that suppresses non-uniformity in brightness by sensing the amount of current in the TFT of each pixel and feeding back the sensing results to the input data (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-108828 A [Patent Document 2] International Publication No. 2015 / 093100 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional image quality compensation technology using sensing, the amount of change in the threshold voltage of the driving TFT and the amount of change in the mobility of the driving TFT are sensed, and compensation data is created based on the sensing results. This requires measuring multiple voltage-current relationships for one pixel and estimating the characteristic fluctuations of the driving TFT, which creates the problem of the long time required for feedback, making it difficult to achieve high-precision feedback in real time.

[0006] An object of the present invention is to provide a display device and a signal processing method capable of compensating image quality in real time while reducing the time required for sensing and the memory used. [Means for solving the problem]

[0007] (1) A display device according to the present invention includes a plurality of pixels for displaying an image, each pixel including a current-driven display element, a driving thin film transistor connected to the current-driven display element, and a switching thin film transistor for controlling an amount of current flowing through the driving thin film transistor, a driving section for applying a different measurement voltage for each pixel to a control electrode of each driving thin film transistor of a plurality of pixels arranged adjacent to each other via the switching thin film transistor; a sensing unit for sampling and sensing an amount of current flowing through each of the driving thin film transistors of the plurality of pixels by applying the measurement voltage to the control electrode; a calculation unit that calculates an electrical characteristic of a driving thin film transistor of one pixel included in the plurality of pixels by using the amount of current flowing through each driving thin film transistor of the plurality of pixels and the measured voltage; a data compensator for converting image data for the one pixel based on a change in an electrical characteristic of the driving thin film transistor; The display device is provided with:

[0008] (2) In the display device described in (1) above, the calculation unit determines the electrical characteristics using an approximation equation having a plurality of parameters, and calculates the parameters of the approximation equation using the amount of current flowing through each driving thin film transistor of the plurality of pixels and the measured voltage.

[0009] (3) The display device according to the above (2), wherein the calculation unit calculates a plurality of first parameters of the approximation equation that approximates an initial electrical characteristic of the driving thin film transistor of the one pixel, and calculates a plurality of second parameters of the approximation equation that approximates an electrical characteristic after a fluctuation of the driving thin film transistor of the one pixel; The data compensation unit can calculate a target current value using the approximation equation having the plurality of first parameters, and convert image data for the one pixel using the approximation equation having the plurality of second parameters.

[0010] (4) In the display device described in (2) above, the data compensation unit calculates the approximation equation having the calculated parameters for each pixel, calculates a target current value for the one pixel by smoothing a plurality of current values ​​calculated from a plurality of approximation equations calculated for a plurality of pixels, and converts image data for the one pixel using the calculated target current value.

[0011] (5) The display device according to any one of (1) to (4) above can perform sensing by the sensing unit while shifting the display position of the image for a certain period of time.

[0012] (6) A signal processing method according to the present invention is a signal processing method for a display device including a plurality of pixels for displaying an image, each pixel including a current-driven display element, a driving thin film transistor connected to the current-driven display element, and a switching thin film transistor for controlling an amount of current flowing through the driving thin film transistor, comprising: applying a different measurement voltage to a control electrode of each driving thin film transistor of a plurality of adjacently arranged pixels via the switching thin film transistor; applying the measurement voltage to the control electrode to sample and sense the amount of current flowing through each of the driving thin film transistors of the plurality of pixels; determining an electrical characteristic of a driving thin film transistor of one pixel included in the plurality of pixels using the amount of current flowing through each driving thin film transistor of the plurality of pixels and the measured voltage; The signal processing method converts image data for one pixel based on a change in the electrical characteristics of the driving thin film transistor. Effect of the Invention

[0013] According to the present invention, the electrical characteristics of the driving TFT can be obtained using sensing data obtained in real time, making it possible to compensate for image data with high precision in real time, and to obtain compensation data with fewer sensing operations and less memory usage. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a configuration of an organic EL display device according to a first embodiment of the display device of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an example of a configuration of a display panel unit. [Diagram 3] 2 is a diagram showing a pixel circuit of one pixel P of the display panel unit. FIG. [Figure 4] FIG. 13 is a characteristic diagram showing the variation from the initial characteristic of the IV characteristic of a driving thin film transistor. [Diagram 5] 4 is a block diagram showing components related to compensation of image data in a signal processing unit. FIG. [Figure 6] FIG. 13 is a diagram showing an example in which different measurement voltages are applied to nine pixels, including a pixel for which the IV characteristics of a driving thin-film transistor of a display panel section are to be determined and surrounding pixels. [Figure 7]FIG. 13 is a diagram showing the IV characteristics of an approximated driving thin film transistor. [Figure 8] 1 is a flowchart showing a signal processing method for compensating for image quality of an organic EL display device. [Figure 9] FIG. 11 is a diagram showing an example in which different measurement voltages are applied to four pixels of a display panel section in an organic EL display device according to a second embodiment of the display device of the present invention. [Figure 10] FIG. 13 is a diagram showing the IV characteristics of an approximated driving thin film transistor. [Figure 11] FIG. 13 is a diagram showing an example in which different measurement voltages are applied to four pixels of a display panel section. [Figure 12] FIG. 13 is a diagram showing an example in which different measurement voltages are applied to a specific pixel and three pixels in the vertical direction of a display panel unit. [Figure 13] FIG. 13 is a diagram showing the IV characteristics of an approximated driving thin film transistor. [Figure 14] FIG. 13 is a diagram showing an example of applying different measurement voltages to a pixel for determining the IV characteristics of a driving thin-film transistor in a display panel section and three pixels in the horizontal direction. [Figure 15] FIG. 13 is a block diagram showing a configuration of an organic EL display device including a wobbling control unit, which is a fourth embodiment of the display device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Hereinafter, as one embodiment of a display device, an example of image quality compensation will be described in an active matrix type organic EL display device in which organic EL display elements, which are current-driven display elements, are arranged in a matrix.

[0016] (First embodiment) Fig. 1 is a block diagram showing the configuration of an organic EL display device according to a first embodiment of the display device of the present invention. Fig. 2 is a diagram showing an example of the configuration of a display panel unit. Fig. 3 is a diagram showing a pixel circuit of one pixel P of the display panel unit. As shown in FIG. 1, the organic EL display device 1 includes a video input section 11, a signal processing section 12, a column driver section 13, a row driver section 14, and a display panel section 15. When a video signal is input, the video input unit 11 temporarily stores image data contained in the video signal in an input buffer and sequentially outputs the image data in accordance with the processing timing to the downstream signal processing unit 12. The signal processing unit 12 generates a panel control signal for controlling the panel drive timing and outputs the signal control signal to the row driver unit 14. The signal processing unit 12 also creates image data for compensating for luminance unevenness from driving TFT parameters calculated using the image data input from the video input unit 11 and the sensing data input from the column driver unit 13 and outputs the image data to the column driver unit 13.

[0017] The column driver unit 13 is connected to a plurality of data signal lines DL and a plurality of sensing signal lines SL arranged in the vertical direction. The data signal lines DL and the sensing signal lines SL are connected to each column of pixels P arranged in a matrix on the display panel unit 15. The column driver unit 13 supplies each of the plurality of data signal lines DL with an image data signal (voltage Vda) for each pixel P during a display operation, and supplies a measurement voltage Vdb during a sensing operation. Sensing data is input to the column driver unit 13 from each pixel P via the sensing signal lines SL.

[0018] A plurality of row selection signal lines RL1 and a plurality of row selection signal lines RL2 arranged in the horizontal direction are connected to the row driver unit 14. The row driver unit 14 sequentially supplies selection signals to the row selection signal lines RL1 for selecting pixel rows of the pixels P arranged in a matrix based on a panel control signal in order to supply image data signals to the pixels P. The row driver unit 14 also sequentially supplies selection signals to the row selection signal lines RL2 in order to select pixel rows of the pixels P arranged in a matrix in order to read out sensing data from the pixels P.

[0019] In the display panel unit 15, a plurality of data signal lines DL and a plurality of sensing signal lines SL are arranged in the vertical direction, a plurality of row selection signal lines RL1 and a plurality of row selection signal lines RL2 are arranged in the horizontal direction, and pixels P are arranged in a matrix at their intersections. An image is displayed by the plurality of pixels P. The data signal line DL, the sensing signal line SL, the row selection signal line RL1, and the row selection signal line RL2 are each connected to a pixel P. Although not shown in FIG. 2, the pixel P is supplied with a voltage Vdd (anode voltage) and a voltage Vss (cathode voltage) for power supply.

[0020] 3, the pixel P includes an organic EL display element Del, a driving thin film transistor (driving TFT) Tr1 (hereinafter referred to as transistor Tr1), a first switching thin film transistor (first switching TFT) Tr2 (hereinafter referred to as transistor Tr2), a second switching thin film transistor (second switching TFT) Tr3 (hereinafter referred to as transistor Tr3), and a storage capacitor C1. The transistor Tr2 controls the amount of current flowing through the transistor Tr1.

[0021] The drain of transistor Tr2 is connected to a data signal line DL, the source is connected to the gate serving as the control electrode of transistor Tr1 and one terminal of storage capacitor C1, and the gate of transistor Tr2 is connected to a row selection signal line RL1. The drain of the transistor Tr1 is supplied with a voltage Vdd, and its source is connected to the other terminal of the storage capacitor C1, the drain of the transistor Tr3, and the anode of the organic EL display element Del. The cathode of the organic EL display element Del is supplied with a voltage Vss. The gate of the transistor Tr3 is connected to the row selection signal line RL2, and the source is connected to the sensing signal line SL.

[0022] The pixel circuit operation of pixel P will now be described. During display operation, a voltage Vscn serving as a selection signal is applied to the row selection signal line RL1, and while the transistor Tr2 is ON, a voltage Vda corresponding to image data is charged to the storage capacitor C1 via the data signal line DL. The current flowing through the transistor Tr1 is adjusted according to the voltage Vda charged to the storage capacitor C1, thereby controlling the current flowing through the organic EL display element Del.

[0023] During the sensing operation, a voltage Vscn serving as a selection signal is applied to the row selection signal line RL1, and a measurement voltage Vdb is charged to the storage capacitor C1 while the transistor Tr2 is ON. The measurement voltage Vdb will be described later. At this time, a voltage Vsen is applied to the row selection signal line RL2, and the transistor Tr3 is turned ON, so that the current flowing through the transistor Tr1 is read from the sensing signal line SL according to the measurement voltage Vdb charged in the storage capacitor C1. The sensing unit 121 of the signal processing unit 12, which will be described later, senses the current value Ids for the measurement voltage Vdb, and can obtain the electrical characteristics (IV characteristics) of the transistor Tr1. When the transistor Tr3 is turned ON, the potential of the anode of the organic EL display element Del drops, and no current flows through the organic EL display element Del. A switch transistor may be provided at the anode of the organic EL display element Del to prevent current from flowing through the organic EL display element Del during the sensing operation.

[0024] In Fig. 4, the dashed line indicates the initial log(Ids)-Vgs characteristic of the transistor Tr1, and the solid line indicates the log(Ids)-Vgs characteristic after the transistor Tr1 has changed. Here, the IV characteristic of the transistor Tr1, which serves as the driving TFT, changes over time due to heat caused by the driving current and light emitted from the organic EL display element Del, as shown in the log(Ids)-Vgs characteristic in Fig. 4. This causes the brightness of the screen to change, and this change in brightness leads to degradation of image quality, such as burn-in and uneven brightness.

[0025] Therefore, in this embodiment, the signal processor 12 acquires the driving TFT current Ids after the change by sensing, and obtains the electrical characteristics (IV characteristics) of the driving TFT of each pixel from the acquired sensing data (current Ids). By compensating the image data of the input video signal based on the change in the acquired electrical characteristics, it becomes possible to suppress the fluctuation in luminance.

[0026] FIG. 5 is a block diagram showing components related to video signal compensation in the signal processing section. 5, the signal processing unit 12 includes a sensing unit 121, a parameter calculation unit 122, a parameter storage unit 123, and a data compensation unit 124. The parameter calculation unit 122 serves as a calculation unit. During the sensing period, the sensing unit 121 outputs measurement data to the column driver unit 13. The column driver unit 13 outputs a measurement voltage Vdb corresponding to the measurement data to the pixel P, and the sensing unit 121 acquires the current value Ids of the transistor Tr1 with respect to the measurement voltage Vdb as sensing data from the pixel P through the sensing operation of the pixel circuit of the pixel P described above. The sensing period is set, for example, to a vertical blanking period during the video display period. The voltage value of the measurement voltage Vdb is set to a voltage value higher than the threshold voltage of the transistor Tr1.

[0027] The parameter calculation unit 122 obtains the gate-source voltage Vgs of the transistor Tr1 from the measurement voltage Vdb obtained based on the measurement data, and obtains the IV characteristics of the transistor Tr1 from this voltage Vgs and the current Ids flowing through the sensing signal line SL. Since it takes a sufficient amount of time to acquire the initial IV characteristics, the sensing unit 121 sequentially outputs multiple pieces of measurement data to the column driver unit 13 in order to set multiple measurement voltages in one pixel. Then, the sensing unit 121 acquires multiple currents Ids corresponding to the multiple measurement voltages Vdb from the pixel P. The parameter calculation unit 122 estimates the IV characteristics of the transistor Tr1 for one pixel using multiple current values ​​corresponding to the multiple measurement voltages Vdb. The initial IV characteristics of the transistor Tr1 are approximated by the following equation 1 (referred to as Equation 1), which is an approximation for each pixel.

number

[0028] Since the light emission intensity of an organic EL element is roughly proportional to the amount of current flowing through the element, it is possible to maintain the uniformity of the panel display by adjusting the voltage value V calculated by Equation 1 and keeping the current value constant. However, as shown in Figure 4, if the IV characteristics deviate from the parameters calculated initially due to driving stress or other factors, the amount of current flowing will change, which will result in a change in the light emission intensity, causing burn-in and uneven brightness. This creates the need to calculate new parameters a, b, and c.

[0029] Therefore, new parameters a, b, and c are calculated by the following method. 6, the sensing unit 121 outputs measurement data to the column driver unit 13 so that the column driver unit 13 sequentially applies measurement voltages Vdb (=V1 to V9) to nine pixels P (which are adjacently arranged pixels) arranged in three rows and three columns as one set. At this time, the measurement data is set so that the measurement voltage Vdb for each pixel in one set of nine pixels is a different value from that of the surrounding pixels, that is, so that the voltages V1 to V9 are different values. 6, when the row driver section 14 selects the nth pixel row of the display panel section 15, the column driver section 13 applies measurement voltages V1, V2, and V3 to every three columns. When the row driver section 14 selects the (n+1)th pixel row, the column driver section 13 applies measurement voltages V4, V5, and V6 to every three columns. When the row driver section 14 selects the (n+2)th pixel row, the column driver section 13 applies measurement voltages V7, V8, and V9 to every three columns. The column driver section 13 similarly applies V1 to V9 as measurement voltages Vdb to the pixel columns before the nth pixel row and the pixel columns after the (n+2)th pixel row. Through the sensing operation of the pixel circuit described above, the sensing unit 121 acquires current values ​​corresponding to the voltage values ​​of the measurement voltages V1 to V9 from the pixels P of the display panel unit 15, with nine pixels P in 3 rows and 3 columns forming one set.

[0030] The parameter calculation unit 122 acquires measurement data from the sensing unit 121, calculates the Vgs of transistor Tr1 of nine pixels from measurement voltages V1 to V9 calculated based on this measurement data, and approximates the IV characteristics of transistor Tr1 of pixel P for each pixel P using the following equation 2 (referred to as equation 2) based on these nine Vgs and nine currents Ids (sensing data) flowing through the sensing signal line SL. The sensing data obtained in real time is measured with a different current-voltage combination for each pixel. Therefore, by using the voltage Vgs and current Ids of the nine neighboring pixels as shown in Fig. 6, the IV characteristics of the transistor Tr1 of the pixel P at the center of the nine pixels are approximated by the following approximate formula 2 (referred to as formula 2), and new parameter values ​​a, b, and c are obtained for the pixel P at the center of the nine pixels and stored in the parameter storage unit 123 such as a memory. The difference between formula 2 and formula 1 is that the parameter values ​​are different.

number

[0031] To explain more specifically, for example, the new parameter values ​​a, b, and c of Equation 2 that approximate the IV characteristics of the transistor Tr1 of the central pixel P33 of the nine pixels P22 to P44 shown in FIG. 6 are found from the relationship between the nine currents Ids output from the pixels P22 to P42, pixels P23 to P43, and pixels P24 to P44 (pixels within the squares indicated by thick solid lines) to which the measurement voltages V1 to V3, V4 to V6, and V7 to V9 are respectively applied, and the voltages Vgs of the transistors Tr1 of the pixels P22 to P42, pixels P23 to P43, and pixels P24 to P44, and are stored in a parameter storage unit 123 such as a memory.

[0032] FIG. 7 shows the IV characteristics (Vgs-Ids characteristics) of the transistor Tr1 of the pixel P33, which are approximated by Equation 2 having parameter values ​​a, b, and c calculated by the parameter calculation unit 122. 7 shows an IV curve (shown by a dashed line) of the transistor Tr1 of pixel P33 with initial characteristics, and an IV curve (shown by a solid line) of the transistor Tr1 of pixel P33 after the change. The IV curve of the transistor Tr1 of pixel P33 after the change is obtained from nine currents Ids output from pixels P22 to P45 (nine pixels surrounded by thick rectangular frames in FIG. 6) to which measurement voltages V1 to V9 are respectively applied, and the voltages Vgs of the transistors Tr1 of pixels P22 to P45. The white circles on the curve showing the IV characteristics of the transistor Tr1 of pixel P33 after the change indicate the relationship between the voltage Vgs and the current Ids obtained from the sensing data of pixels P22 to P45. In addition, when pixel P33 is arranged in the first row or the last row of the display panel unit 15, the parameter values ​​a, b, and c of Equation 2 can be obtained using sensing data of three pixels horizontally (three pixels in the row direction) centered on pixel P33, as described in the second embodiment described later.

[0033] Similarly, new parameter values ​​a, b, and c of Equation 2 that approximate the IV characteristics of transistor Tr1 of pixel P34 are calculated from nine currents Ids output from pixels P23 to P44 and pixels P25 to P45 (pixels within the square indicated by the thick dashed line) to which measurement voltages V4 to V9 and V1 to V3 are respectively applied, and the voltages Vgs of transistor Tr1 of pixels P22 to P44 and pixels P25 to P45, and are stored in a parameter storage unit 123 such as a memory. Similarly, for pixels of the display panel unit 15 other than the pixels P33 and P34, new parameter values ​​a, b, and c of Equation 2 that approximate the IV characteristics of the transistor Tr1 are found and stored in the parameter storage unit 123 such as a memory.

[0034] Image data generally has a high correlation with neighboring pixels, so neighboring pixels are subject to similar driving stress, and it is expected that the characteristic fluctuations of the driving TFTs will be similar. Therefore, even if sensing data from neighboring pixels is used, it is possible to compensate with the same accuracy as electrical characteristics approximated at multiple measurement points at the same pixel. Image quality can be improved by converting image data using parameters a, b, and c and compensating for burn-in.

[0035] Next, the data compensation unit 124 compensates the image data using the parameters a, b, and c found for each pixel. As already explained, when a video signal is input to video input unit 11, image data contained in the video signal is stored in an input buffer. The data compensation unit 124 reads out the stored image data for each pixel in accordance with the driving timing of the panel, and calculates the target current value Itarget shown in the following formula 3 (referred to as formula 3) using initial parameters a0, b0, and c0 from the voltage value V corresponding to the signal level of the image data. This target current value Itarget may be corrected according to external conditions such as temperature. Using the current value Itarget and parameters a, b, and c stored in memory for each pixel, the voltage V' is calculated by the following formula 3. The formula for calculating the voltage V' in formula 3 is a modified version of the approximation formula in formula 2, and is a formula using formula 2.

number

[0036] Next, a signal processing method for compensating for image quality of an organic EL display device will be described with reference to the flow chart shown in FIG. In step S11, the sensing unit 121 outputs measurement data to the column driver unit 13 so that the column driver unit 13 sequentially applies measurement voltages Vdb (=V1 to V9) to nine pixels P of 3 rows x 3 columns as one set. The row driver unit 14 applies measurement voltages V1, V2, V3, measurement voltages V4, V5, V6, measurement voltages V7, V8, V9 to each of three rows of pixels. The sensing unit 121 performs current sensing to obtain current values ​​Ids corresponding to the voltage values ​​of measurement voltages V1 to V9 from the pixels of the display panel unit 15, with nine pixels P of 3 rows x 3 columns as one set. In this manner, the sensing unit 121 performs current sensing. In step S12, the parameter calculation section 122 calculates Vgs of the transistors Tr1 of the nine pixels from the measurement voltages V1 to V9 obtained based on the measurement data.

[0037] In step S13, the parameter calculation unit 122 approximates the IV characteristics of the transistor Tr1 of one pixel P using Equation 2 from the nine Vgs and the nine currents Ids flowing through the sensing signal line SL, determines new parameter values ​​a, b, and c for one pixel P, and stores them in the parameter storage unit 123, such as a memory.

[0038] In step S14, the parameter calculation unit 122 determines whether new parameter values ​​a, b, c have been calculated for all pixels of the display panel unit 15, and if new parameter values ​​a, b, c have not been calculated for all pixels, the process returns to step S13. If new parameter values ​​a, b, c have not been calculated for all pixels, the process proceeds to step S15.

[0039] In step S15, the data compensation unit 124 compensates the image data using the parameter values ​​a, b, and c thus determined for each pixel. The data compensation unit 124 reads out the stored image data from the input buffer for each pixel in accordance with the driving timing of the panel, and calculates the target current value Itarget of Equation 3 from the voltage value V corresponding to the signal level of the image data using initial parameters a0, b0, and c0. This current value may be corrected according to external conditions such as temperature. Using the current value Itarget and parameters a, b, and c stored in the memory for each pixel, V' is calculated according to Equation 3. Image data corresponding to this voltage value V' is output to the column driver unit 13.

[0040] With the above, it is possible to provide a method for compensating image quality for OLED displays that can perform compensation in real time. Here, an example is shown in which nine measurement voltages are allocated to the nine surrounding pixels. In this case, compared to measuring nine different voltages for each pixel, it is possible to reduce the time required for measurement and the memory required to store the measurement results to one-ninth. This effect has a significant advantage in high-resolution displays such as 8K.

[0041] Second embodiment In the first embodiment, the parameters of the equation approximating the IV characteristics of the driving TFT are obtained using sensing data of nine neighboring pixels, but since the IV characteristics are approximated by an equation expressed by three parameters, it is possible to obtain the parameters of the equation approximating the IV characteristics of the driving TFT using sensing data of at least three pixels. Therefore, in this embodiment, a case will be described in which the parameters of the equation approximating the IV characteristics of the driving TFT are obtained using sensing data of four neighboring pixels as shown in Figures 9 and 11, and a case will be described in which the parameters of the equation approximating the IV characteristics of the driving TFT are obtained using sensing data of three vertical pixels or three horizontal pixels as shown in Figures 12 and 13.

[0042] (Example of approximation using 4 nearby pixels) In this embodiment, the new parameters are obtained by the following method. 9, the sensing unit 121 outputs measurement data to the column driver unit 13 so that the column driver unit 13 sequentially applies measurement voltages Vdb (=V11 to V14) to four pixels P (which are adjacently arranged pixels) arranged in two rows and two columns as one set. At this time, the measurement data is set so that the measurement voltage Vdb for each pixel in one set has a different value from that of the surrounding pixels, that is, so that the voltages V11 to V14 have different values. The voltage values ​​of the measurement voltages Vdb (=V11 to V14) are set to voltage values ​​higher than the threshold voltage of the transistor Tr1. 9, when the nth pixel row of the display panel unit 15 is selected by the row driver unit 14, the column driver unit 13 applies measurement voltages V11, V12 to every two columns, and when the (n+1)th pixel row is selected, the column driver unit 13 applies measurement voltages V13, V14 to every two columns. Similarly, V11 to V14 are applied as measurement voltages Vdb to two pixel columns before the nth pixel row and after the (n+1)th pixel row. Through the sensing operation of the pixel circuit described above, the sensing unit 121 acquires current values ​​Ids corresponding to the voltage values ​​of measurement voltages V11 to V14 from the pixels of the display panel unit 15, with four pixels P in 2 rows and 2 columns forming one set.

[0043] The parameter calculation unit 122 calculates four Vgs from the measurement voltages V11 to V14 calculated based on the measurement data and the four voltage values ​​of the sensing signal line SL, and approximates the IV characteristics of the transistor Tr1 of the pixel P for each pixel using Equation 2 based on these four Vgs and the four currents Ids flowing through the sensing signal line SL, thereby calculating the parameters of Equation 2. Specifically, a case will be described in which the parameter calculation unit 122 determines the parameters of Formula 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P22 shown in Fig. 9. When determining the parameters of Formula 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P22, the pixel P22 may be arranged at the upper left, upper right, lower left, or lower right of the four pixels including the pixel P22, as with the pixel P23 described later, but the following description will be given taking as an example a case in which the pixel P22 is arranged at the upper left of the four pixels.

[0044] The parameters of Equation 2 that approximate the IV characteristics of transistor Tr1 of pixel P22 are obtained from the four currents Ids output from pixels P22, P32, P23, and P33 (pixels within the bold squares) to which measurement voltages V11 to V14 are respectively applied, and the voltages Vgs of transistor Tr1 of pixels P22, P32, P23, and P33. The sensing data obtained in real time is measured with a different voltage-current combination for each pixel. Therefore, by using the sensing data of the four neighboring pixels (pixels P22, P32, P23, and P33) as shown in Fig. 9, the IV characteristics of the transistor Tr1 of the pixel P22 are approximated by Equation 2, and new parameter values ​​a, b, and c for the pixel P22 are obtained and stored in the parameter storage unit 123 such as a memory. 10 shows an IV curve (curve shown by a dashed line) of the transistor Tr1 of pixel P22 having initial characteristics, and an IV curve (curve shown by a solid line) of the transistor Tr1 of pixel P22 after the fluctuation, which is calculated from four currents Ids output from pixels P22 to P33 (four pixels surrounded by thick rectangular frames in FIG. 9) to which measurement voltages V11 to V14 are respectively applied, and the voltages Vgs of the transistors Tr1 of pixels P22 to P33. The white circles on the curve showing the IV characteristics of the transistor Tr1 of pixel P22 after the fluctuation indicate the relationship between the voltage Vgs and the current Ids calculated from the sensing data of pixels P22 to P33. In addition, when pixel P22 is arranged in the first row or the last row of the display panel unit 15, the parameter values ​​a, b, and c of Equation 2 can be obtained using sensing data of three pixels horizontally (three pixels in the row direction) centered on pixel P22.

[0045] In this embodiment, there are four methods (1) to (4) for finding the parameters of the formula 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P23. (1) The parameters of Equation 2 that approximate the IV characteristics of the transistor Tr1 of pixel P23 are calculated from the four currents Ids output from pixels P23, P33 to which measurement voltages V13, V14 are applied, respectively, and from pixels P24, P34 (pixels within the squares indicated by thick dashed lines) to which measurement voltages V11, V12 are applied, respectively, as shown in FIG. 9, and the voltages Vgs of the transistors Tr1 of pixels P22, P33, and pixels P24, P34. (2) The parameters of Equation 2 that approximate the IV characteristics of the transistor Tr1 of pixel P23 are calculated from the four currents Ids output from pixels P12, P22 to which measurement voltages V12, V11 are applied, respectively, and from pixels P13, P23 (pixels within the squares indicated by thick dotted lines) to which measurement voltages V14, V13 are applied, respectively, as shown in FIG. 11, and the voltages Vgs of the transistors Tr1 of pixels P12, P22, P24, and P23. (3) The parameters of Equation 2 that approximate the IV characteristics of transistor Tr1 of pixel P23 are calculated from four currents Ids output from pixels P13, P23 to which measurement voltages V14, V13 are applied, and from pixels P14, P24 (pixels within the squares indicated by dashed lines with small pitch) to which measurement voltages V12, V11 are applied, as shown in FIG. 11, and from voltages Vgs of transistors Tr1 of pixels P13, P23, P14, and P24. (4) As shown in Fig. 9, pixels P22 and P32 in the nth row and pixels P23 and P33 in the (n+1)th row (pixels in the thick-line squares) to which measurement voltages V11 to V14 are applied, respectively, are the same in that they each have three adjacent pixels, and therefore the parameters of Formula 2 that approximate the IV characteristics of the transistor Tr1 of pixel P22 are used. In this way, by using the parameters of Formula 2 that approximate the IV characteristics of the same transistor Tr1 of one pixel for four pixels P in 2 rows and 2 columns, the amount of calculation required to find the parameters of Formula 2 that approximate the IV characteristics of the transistors Tr1 of all pixels in the display panel unit 15 can be reduced. Any of the methods (1) to (4) described above may be used. However, since the fluctuation characteristics may differ even in the vicinity near the boundary of burn-in, it is possible to select one of the methods (1) to (4) that has similar fluctuation characteristics (such as the rate of fluctuation of the current value).

[0046] (Example of approximation using 3 vertical pixels) In this embodiment, the new parameters are obtained by the following method. As shown in FIG. 12, the sensing unit 121 outputs measurement data to the column driver unit 13 so that the column driver unit 13 sequentially applies different measurement voltages Vdb (=V21 to V23) to each set of three pixel rows. 12, when the row driver unit 14 selects the nth pixel row of the display panel unit 15, the column driver unit 13 applies a measurement voltage V21 to all pixels in the nth pixel matrix. When the row driver unit 14 selects the (n+1)th pixel row, the column driver unit 13 applies a measurement voltage V22 to all pixels in the (n+1)th pixel row, and when the row driver unit 14 selects the (n+2)th pixel row, the column driver unit 13 applies a measurement voltage V23 to all pixels in the (n+2)th pixel row. Through the sensing operation of the pixel circuit described above, the sensing unit 121 obtains current values ​​corresponding to the voltage values ​​of the voltages V21 to V23 from the pixels of the display panel unit 15, with three pixels P of 3 rows and 1 column forming one set.

[0047] The parameter calculation unit 122 calculates three Vgs from the voltages V21 to V23 calculated based on the measurement data and the three voltage values ​​of the sensing signal line SL, and calculates the parameters of Equation 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P from the three Vgs and the three currents Ids flowing through the sensing signal line SL. For example, the parameters of Equation 2 that the parameter calculation unit 122 uses to approximate the IV characteristics of the transistor Tr1 of the pixel P33 shown in FIG. 12 are calculated from the three currents Ids output from the pixels P32, P33, and P34 (pixels within the squares indicated by the bold lines) to which the measurement voltages V21 to V23 are respectively applied, and the voltages Vgs of the transistors Tr1 of the pixels P32, P33, and P34.

[0048] 13 shows an IV curve (curve shown by a dashed line) of the transistor Tr1 of pixel P22 having initial characteristics, and an IV curve (curve shown by a solid line) of the transistor Tr1 of pixel P33 after the change, which is calculated from three currents Ids output from pixels P32-P34 (three pixels surrounded by thick rectangular frames in FIG. 12) to which measurement voltages V21-V23 are respectively applied, and the voltages Vgs of the transistors Tr1 of pixels P32-P34. The white circles on the curve showing the IV characteristics of the transistor Tr1 of pixel P33 after the change indicate the relationship between the voltage Vgs and the current Ids calculated from the sensing data of pixels P32-P34.

[0049] (Example of approximation using 3 pixels horizontally) In this embodiment, the new parameters are obtained by the following method. As shown in FIG. 14, the sensing unit 121 outputs measurement data to the column driver unit 13 so that the column driver unit 13 sequentially applies different measurement voltages Vdb (=V31 to V33) to each set of three pixel columns. As shown in FIG. 14, when each pixel row of the display panel section 15 is selected by the row driver section 14, the column driver section 13 applies measurement voltages V31, V32, and V33 to every three columns. Through the sensing operation of the pixel circuit described above, the sensing unit 121 obtains current values ​​corresponding to the voltage values ​​of the voltages V31 to V33 from the pixels of the display panel unit 15, with three pixels P in one row and three columns forming one set.

[0050] The parameter calculation unit 122 calculates three Vgs from the voltages V31 to V33 calculated based on the measurement data and the three voltage values ​​of the sensing signal line SL, and calculates the parameters of Equation 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P from the three Vgs and the three currents Ids flowing through the sensing signal line SL. For example, when the parameter calculation unit 122 calculates the parameters of Equation 2 that approximate the IV characteristics of the transistor Tr1 of the pixel P33 shown in FIG. 14, the parameters are calculated from the three currents Ids output from the pixels P23, P33, and P43 (pixels within the squares indicated by the bold lines) to which the measurement voltages V31 to V33 are respectively applied, and the voltages Vgs of the transistors Tr1 of the pixels P32, P33, and P34.

[0051] In the first and second embodiments described above, when determining the initial parameter values ​​a0, b0, c0, the sensing unit 121 sequentially outputs multiple pieces of measurement data to the column driver unit 13 in order to set multiple measurement voltages in one pixel, and obtains multiple current values ​​corresponding to multiple voltage values ​​of measurement voltages Vdb corresponding to the multiple pieces of measurement data from the pixel P. However, even when determining the initial parameter values ​​a0, b0, c0, the initial parameter values ​​a0, b0, c0 may be determined by the method of determining new parameters a, b, c described in the first and second embodiments.

[0052] Third embodiment In the first and second embodiments, the initial parameter values ​​a0, b0, and c0 are stored in memory, and the target current value is calculated from the voltage value according to the signal level. However, in this case, it becomes necessary to store the initial parameters for each pixel, which requires a large amount of memory.

[0053] Therefore, in this embodiment, the target current value is obtained as follows. Burn-in is easily noticeable when the amount of current changes due to fluctuations in the driving TFT, even with the same signal level, causing a locally large step in brightness. In order to prevent this from being noticeable, the current flowing for the same signal level can be spatially changed gradually. Therefore, as shown below, the target current value Itarget for one pixel is calculated by smoothing the current value after fluctuation when a voltage value according to the signal level of Equation 4 (hereinafter referred to as Equation 4) is applied over p×q pixels (for example, about 100×100 pixels) of one pixel and its surrounding pixels. s and t in Equation 4 are numbers (natural numbers) that indicate the range to be smoothed.

number

[0054] (Fourth embodiment) As a method for reducing the visibility of burn-in caused by fluctuations in the driving TFT, a method of wobbling (slightly moving the screen position) is used in PDPs and other self-luminous displays similar to organic EL display elements. By using wobbling, it is possible to smooth out the brightness step caused by burn-in, and in this embodiment, by shifting the display position of the image for a certain period of time, sensing is performed in real time, and by using this simultaneously with obtaining the electrical characteristics of nearby pixels, a synergistic effect can be achieved, making it possible to dramatically improve effectiveness.

[0055] Fig. 15 is a block diagram showing the configuration of an organic EL display device including a wobbling control unit, which is a fourth embodiment of the display device of the present invention. The configuration of an organic EL display device 1A shown in Fig. 15 is the same as the configuration of the organic EL display device 1 shown in Fig. 1, except for the wobbling control unit. Wobbling is described in, for example, Japanese Patent Application Laid-Open No. 2007-304318. The wobbling control unit 16 in FIG. 15 controls the display position of the image to move by a predetermined movement amount at a predetermined time interval in order to suppress the visual recognition of image burn-in. The wobbling control unit 16 can have the same configuration as the display screen control unit described in Japanese Patent Application Laid-Open No. 2007-304318. The display screen control unit includes a time interval setting unit for setting the time interval for moving the image, a movement distance setting unit for setting the movement interval for moving the image, and a movement direction switching unit for moving the image in the horizontal and vertical directions. Details of these operations are described in Japanese Patent Application Laid-Open No. 2007-304318.

[0056] The embodiments described above are preferred embodiments of the present invention, but the scope of the present invention is not limited to the above-described embodiments and examples, and the present invention can be implemented in various modified forms without departing from the gist of the present invention. [Explanation of symbols]

[0057] 1, 1A organic EL display device 11 Video input section 12 Signal Processing Section 13 Column driver section 14 Row driver section 15 Display panel section 121 Sensing section 122 Parameter Calculation Unit 123 Parameter memory section 124 Data Compensation Unit Del Organic EL display element Tr1 Driving thin film transistor Tr2 First switch thin film transistor Tr3 Second switch thin film transistor C1 Storage Capacitor

Claims

1. A display device including a plurality of pixels for displaying an image, each pixel including a current-driven display element, a driving thin film transistor connected to the current-driven display element, and a switching thin film transistor for controlling an amount of current flowing through the driving thin film transistor, a drive section that applies a measurement voltage, which differs for each pixel, to a control electrode of each driving thin film transistor of a set of a plurality of pixels arranged adjacent to each other, via each switching thin film transistor of the set of a plurality of pixels; a sensing unit for sampling and sensing an amount of current flowing through each of the driving thin film transistors of the set of pixels by applying the measurement voltage to the control electrode; a calculation unit that calculates an electrical characteristic of a driving thin film transistor of one pixel included in the set of the plurality of pixels by using the amount of current flowing through each driving thin film transistor of the set of the plurality of pixels and the measured voltage; a data compensator for converting image data for the one pixel based on a change in an electrical characteristic of the driving thin film transistor; A display device comprising:

2. 2. The display device according to claim 1, wherein the calculation unit determines the electrical characteristics using an approximation equation having a plurality of parameters, and calculates the parameters of the approximation equation using the amount of current flowing through each driving thin film transistor of the set of multiple pixels and the measured voltage.

3. the calculation unit calculates a plurality of first parameters of the approximation equation that approximates an initial electrical characteristic of the driving thin film transistor of the one pixel, and calculates a plurality of second parameters of the approximation equation that approximates an electrical characteristic after a fluctuation of the driving thin film transistor of the one pixel; 3. The display device according to claim 2, wherein the data compensation unit calculates a target current value using the approximation formula having the plurality of first parameters, and converts the image data for the one pixel using the approximation formula having the plurality of second parameters.

4. 3. The display device according to claim 2, wherein the data compensation unit obtains the approximation equation having the calculated parameters for each pixel of the set of pixels, obtains a target current value for the one pixel by smoothing a plurality of current values ​​obtained from the approximation equations obtained for the set of pixels, and converts image data for the one pixel using the obtained target current value.

5. The display device according to claim 1 , wherein sensing is performed by the sensing unit while shifting a display position of the image for a certain period of time.

6. A signal processing method for a display device including a plurality of pixels for displaying an image, each pixel including a current-driven display element, a driving thin film transistor connected to the current-driven display element, and a switching thin film transistor for controlling an amount of current flowing through the driving thin film transistor, comprising: applying a measurement voltage, which is different for each pixel, to a control electrode of each driving thin film transistor of a set of a plurality of pixels arranged adjacent to each other through each switching thin film transistor of the set of a plurality of pixels; applying the measurement voltage to the control electrode to sample and sense the amount of current flowing through each of the driving thin film transistors of the set of pixels; determining an electrical characteristic of the driving thin film transistor of one pixel included in the set of the plurality of pixels using the amount of current flowing through each driving thin film transistor of the set of the plurality of pixels and the measured voltage; A signal processing method for converting image data for the one pixel based on a change in an electrical characteristic of the driving thin film transistor.

Images