JP2010139837A - Image display device and driving method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably improve accuracy in prediction of luminance deterioration as compared with the conventional manner by using an active matrix image display device employing organic EL (Electro Luminescence) elements. <P>SOLUTION: Regarding a constitution to correct image data gradation and to correct the luminance, by using the light reception results obtained by a plurality of light receiving elements, the deterioration amount per unit time for every gradation, that is, the deterioration amount converted to a display time on a master degradation curve, is successively updated, and the deterioration amount per unit time is accumulated in accordance with the image data gradation, and then, the luminance is corrected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image display device and a driving method of the image display device, and can be applied to an active matrix image display device using a self-luminous element such as an organic EL (Electro Luminescence) element. The present invention sequentially updates the deterioration amount of each gradation unit time converted to the display time on the master deterioration curve by using the light reception results of a plurality of light receiving elements, and the unit time of the unit time according to the gradation of the image data. By accumulating the deterioration amount and correcting the light emission luminance, the prediction accuracy of the light emission luminance is remarkably improved as compared with the conventional case.

  In recent years, active matrix image display devices using organic EL elements have been actively developed. Here, the organic EL element is a current-driven self-luminous element in which light emission luminance is expressed by a multiplication value of light emission efficiency and drive current. An active matrix type image display device using an organic EL element has a pixel circuit formed by an organic EL element and a drive circuit that drives the organic EL element arranged in a matrix to form an image display unit that is an effective pixel region, A desired image is displayed on the image display unit.

  However, as the organic EL element is used for a long time, the light emission efficiency decreases. In addition, the organic EL element has gradation dependency on the rate of decrease in the luminous efficiency, and the higher the emission luminance, the faster the decrease in the luminous efficiency. Accordingly, in an image display device using an organic EL element, emission luminance decreases and chromaticity changes due to long-term use. In addition, when a still image having a high contrast is displayed for a long time, so-called burn-in occurs. Therefore, for example, Japanese Patent Application Laid-Open No. 2007-156044 discloses a configuration for preventing a decrease in light emission luminance.

  Here, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2007-156044, a monitor organic EL element (hereinafter referred to as a dummy organic EL element) and a light receiving element are provided in a portion other than the image display unit. In this method, a decrease in light emission luminance in the dummy organic EL element is detected using a light receiving element. Further, using this detection result, the deterioration amount when the organic EL element is driven at each gradation is predicted. Further, using this prediction result, the light emission luminance of the organic EL element provided in the image display unit is predicted based on the gradation of the organic EL element provided in the image display unit. Further, the luminance of the image data is corrected by correcting the gradation of the image data based on the prediction result.

  That is, as shown in FIG. 7, the light emission luminance y of the organic EL element when light is emitted at a predetermined gradation L can be expressed by the following equation. Here, t is the light emission time. G (L, Lo) is a function for obtaining a deterioration rate when light is emitted at gradation L from a decrease rate of light emission luminance when light is emitted at gradation Lo. It is a degradation rate conversion function shown. Accordingly, the deterioration rate conversion function g (L, Lo) increases in value as the gradation L increases. y = f (t, Lo) is a reference deterioration curve used for correcting the light emission luminance, and is hereinafter referred to as a master deterioration curve. Further, y = f (t, L) is referred to as a gradation curve of gradation L. In FIG. 7, the light emission luminance y is shown normalized.

The technique disclosed in Japanese Patent Application Laid-Open No. 2007-156044 is based on the relationship of the formula (1), and the amount of deterioration of the emission luminance (1-f (t, Lo)) detected by the dummy organic EL element is The deterioration rate conversion function g (L, Lo) is multiplied to predict the emission luminance deterioration amount (1-f (t, L)) when the organic EL element is driven at each gradation. Further, the prediction results are selected and accumulated according to the gradation of the organic EL element provided in the image display unit, and the light emission luminance in each pixel is predicted.
JP 2007-156044 A

  However, the method disclosed in Japanese Patent Application Laid-Open No. 2007-156044 has a problem that is still insufficient in practice in terms of prediction accuracy.

  In particular, when the deterioration of the light emission luminance at each gradation is predicted using the relationship of the expression (1), the master deterioration curve y = f (t, Lo) is vertical according to the deterioration rate conversion function g (L, Lo). The deterioration curve y = f (t, L) of the gradation L is obtained by expanding and contracting in the axial direction. Therefore, when the emission luminance y due to the master deterioration curve y = f (t, Lo) approaches the value 0 due to the increase in time t, the deterioration curve y = f (t, L) of the gradation L larger than the gradation Lo becomes There is a risk of falling below 0. Therefore, in the conventional method, a physical contradiction occurs.

  In the method disclosed in Japanese Patent Application Laid-Open No. 2007-156044, the deterioration amount is predicted by selecting a deterioration curve based on a change in gradation of the organic EL element provided in the image display unit. Accordingly, even when there are a plurality of organic EL elements having the same deterioration amount at a predetermined time and these organic EL elements are driven at the same gradation, the deterioration amount is reduced by the plurality of organic EL elements. There are cases where equality cannot be guaranteed. Also in this case, the conventional method causes a physical contradiction.

  The present invention has been made in consideration of the above points, and intends to propose an image display device and a driving method of the image display device that can significantly improve the accuracy of predicting the emission luminance as compared with the prior art. It is.

  In order to solve the above problems, the invention of claim 1 is applied to an image display device, and an image display panel that displays image data by a self-luminous element, a light receiving element that receives light emitted from the image display panel, A luminance correction unit that processes a light reception result of the light receiving element and corrects a gradation of image data displayed on the image display panel; Here, the brightness correction unit, based on the light reception result, a master deterioration curve generation unit that generates a master deterioration curve indicating a temporal change in the light emission luminance of the self-light-emitting element, and for each predetermined gradation of the image data, Search the gradation / degradation amount conversion table in which the deterioration amount when the self-light-emitting element is driven for a unit time is recorded with the deterioration amount converted into the display time on the master deterioration curve, and the gradation / degradation amount conversion table. A deterioration amount calculation unit that detects a deterioration amount corresponding to the gradation of the image data, a cumulative deterioration amount calculation unit that calculates a cumulative deterioration amount by accumulating the deterioration amount detected by the deterioration amount calculation unit, A correction amount determination unit configured to detect a display time deterioration amount corresponding to the cumulative deterioration amount from the master deterioration curve and set a correction amount of the image data. Here, the light receiving element is a plurality of light receiving elements that respectively receive light emitted from self-light emitting elements having different light emission luminances, and the correction amount determination unit is configured to perform the gradation based on the light reception results of the plurality of light receiving elements. A conversion table update unit that updates the deterioration amount conversion table is provided.

  The invention of claim 7 is applied to a driving method of an image display device comprising an image display panel that displays image data by a self-light emitting element and a light receiving element that receives light emitted from the image display panel. Here, there is a luminance correction step of processing the light reception result of the light receiving element and correcting the gradation of the image data displayed on the image display panel. The brightness correction step includes a master deterioration curve generation step for generating a master deterioration curve indicating a temporal change in light emission luminance of the self-light-emitting element based on the light reception result, and the self-light-emitting element for each predetermined gradation of the image data. A gradation / degradation amount conversion table in which the degradation amount when the light emitting element is driven for a unit time is recorded with the degradation amount converted into the display time on the master degradation curve is searched, and the degradation corresponding to the gradation of the image data A deterioration amount calculating step for detecting an amount, a cumulative deterioration amount calculating step for calculating a cumulative deterioration amount by accumulating the deterioration amounts detected in the deterioration amount calculating step, and a display time deterioration corresponding to the cumulative deterioration amount A correction amount determining step of detecting the amount from the master deterioration curve and setting a correction amount of the image data. Here, the light receiving elements are a plurality of light receiving elements that respectively receive light emitted from the self-light emitting elements having different emission luminances, and the correction amount determining step is performed based on light reception results of the plurality of light receiving elements. / A conversion table update step for updating the deterioration amount conversion table.

  According to the configuration of claim 1 or claim 7, the deterioration amount converted into the display time on the master deterioration curve is accumulated, and the corresponding deterioration amount of the display time is detected from the master deterioration curve, whereby the master deterioration curve is obtained. It is possible to prevent the occurrence of a physical contradiction in which the light emission luminance due to becomes closer to the value 0 due to the increase in time, and the light emission luminance at a larger gradation becomes less than 0. In addition, regardless of the amount of deterioration of each pixel, the amount of deterioration is predicted on the master deterioration curve. Therefore, when the deterioration amounts become equal at a predetermined time and there are organic EL elements that are driven at the same gradation, it is possible to ensure that the deterioration amounts of these organic EL elements are equal. Therefore, a physical contradiction due to the conventional method can be effectively avoided, and the prediction accuracy of the degradation of the light emission luminance can be remarkably improved as compared with the conventional case. Under these assumptions, if the gradation / degradation amount conversion table is set to a fixed value, it cannot sufficiently cope with variations in the self-light-emitting elements and the like, and the prediction accuracy of the light emission luminance deteriorates. On the other hand, according to the configuration of claim 1 or claim 7, since the gradation / deterioration amount conversion table is updated based on a plurality of light reception results having different gradations, such variations in self-luminous elements, etc. The prediction accuracy can be improved by setting a gradation / degradation amount conversion table so as to be compatible with the above.

  According to the present invention, the prediction accuracy of the light emission luminance can be significantly improved as compared with the conventional case.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The description will be given in the following order.
1. First Embodiment 2. FIG. Second Embodiment 3. FIG. Third embodiment 4. Modification <First Embodiment>
[Configuration of the embodiment]
FIG. 2 is a diagram illustrating the image display apparatus according to the first embodiment of the present invention. The image display device 1 displays a desired image by driving the image display panel 3 with image data D1 input via the luminance correction unit 2.

  Here, in the image display panel 3, the pixel circuits 5 are arranged in a matrix to form the image display unit 4 that is an effective pixel region. The pixel circuit 5 is formed by an organic EL element 6 that is a self-luminous element and a drive circuit that drives the organic EL element 6. Further, the image display panel 3 is provided with a plurality of dummy pixel circuits 5DA and 5DB at portions other than the image display section 4, and the dummy pixel circuits 5DA and 5DB are provided with a plurality of dummy organic EL elements 6DA and 6DB, respectively. . In this embodiment, two organic EL elements 6DA and 6DB are applied to the plurality of dummy organic EL elements 6DA and 6DB.

  Here, as shown in FIG. 2B by taking a cross section along the line AA, the dummy organic EL elements 6DA and 6DB are formed so as to emit outgoing light to the back side of the image display panel 3. . More specifically, in this image display panel 3, the organic EL element 6 of the image display unit 4 is created by the top emission method, whereas the dummy organic EL elements 6DA and 6DB are created by the bottom emission method. The The dummy pixel circuits 5DA and 5DB and the organic EL elements 6DA and 6DB are created in the same way as the pixel circuit 5 of the image display unit 4 except that the bottom emission method is used. In FIG. 2, reference numerals L1, L1DA, and L1DB denote emitted lights from the organic EL elements 6, 6DA, and 6DB.

  In the image display panel 3, light receiving elements 7A and 7B that receive the emitted lights L1DA and L1DB of the dummy organic EL elements 6DA and 6DB, respectively, are arranged on the back side of the image display panel 3. The light receiving elements 7A and 7B are, for example, photodiodes, and are arranged by bonding using, for example, a transparent adhesive. The image display device 1 drives the dummy organic EL elements 6DA and 6DB by the luminance correction unit 2, and measures the light emission luminance of the organic EL elements 6DA and 6DB at a constant time interval based on the light reception results of the light receiving elements 7A and 7B. To do. Further, based on the measured light emission luminance, the luminance correction unit 2 corrects the gradation of the image data D1 and outputs it to the image display panel 3 to correct the decrease in the light emission luminance.

[Detailed configuration of brightness correction unit]
FIG. 1 is a block diagram showing a detailed configuration of the luminance correction unit 2. Note that the luminance correction unit 2 includes, for example, arithmetic processing means for executing a luminance correction program and peripheral circuits of the arithmetic processing means. Therefore, each block of the luminance correction unit 2 shown in FIG. 1 is a functional block configured by the arithmetic processing means and the peripheral configuration of the arithmetic processing means.

  The correction unit 11 multiplies the image data D1 by the correction amount for each pixel determined by the correction amount determination unit 12, and corrects the gradation of the image data D1 to generate image data D3. The correction unit 11 time-division multiplexes the image data D3 and the drive data D2A and D2B output from the dummy pixel control unit 13 and outputs them to the image display panel 3. Instead of the image data D3 and the drive data D2A and D2B being time-division multiplexed and input to the image display panel 3, the image data D3 and the drive data D2A and D2B may be individually input to the image display panel 3.

  The image display panel 3 drives the pixel circuit 5 of the image display unit 4 with the image data D3. The drive data D2A and D2B are input to the dummy pixel circuits 5DA and 5DB, respectively, and the dummy organic EL elements 6DA and 6DB are caused to emit light by the drive data D2A and D2B, respectively.

  The degradation amount calculation unit 14 searches the gradation / degradation amount table 15 with the image data D3 output from the correction unit 11, and detects and outputs the degradation amount corresponding to the gradation of the image data D3. Here, the gradation / deterioration amount table 15 is a table in which the deterioration amount when the organic EL element is driven in unit time for each gradation is converted into a display time on the master deterioration curve and recorded. In this embodiment, this unit time is set to a period of one frame which is a repetition cycle of the image data D1.

  The cumulative degradation amount calculation unit 16 adds the degradation amount per unit time detected by the degradation amount calculation unit 14 to the cumulative degradation amount of the corresponding pixel recorded in the cumulative degradation amount accumulation unit 17 and outputs the result. The cumulative deterioration amount accumulation unit 17 records and holds the deterioration amount calculated by the cumulative deterioration amount calculation unit 16 for each pixel.

  The correction amount determination unit 12 calculates the correction value of the corresponding image data D1 based on the deterioration amount for each pixel recorded in the cumulative deterioration amount accumulation unit 15.

  Accordingly, the luminance correction unit 2 detects the deterioration amount of each pixel by accumulating the corresponding gradation deterioration amount recorded in the gradation / degradation amount table 15 for each pixel of the image display unit 4. The gradation of each pixel is corrected based on the amount. The brightness correction unit 2 creates a master deterioration curve, which is a correction reference for each pixel, from the light reception result of the light receiving element 7A. Further, the luminance correction unit 2 updates the record of the gradation / degradation amount table 15 based on the light reception results of the light receiving elements 7A and 7B at a constant update cycle. Here, this update cycle is set to a period of a plurality of frames.

  That is, in the brightness correction unit 2, the deterioration amount measurement unit 18 processes the light reception results of the light receiving elements 7A and 7B, detects the light emission brightness of the dummy organic EL elements 6DA and 6DB, and outputs the detection result.

  The dummy pixel control unit 13 generates and outputs drive data D2A and D2B by feedback control based on the detection result of the deterioration amount actual measurement unit 18, and causes the organic EL elements 6DA and 6DB to emit light at a constant light emission luminance. In this embodiment, on the side of the organic EL element 6DA that creates the master deterioration curve, this constant light emission luminance is set to the light emission luminance corresponding to the maximum gradation of the image data D3. On the remaining organic EL element 6DB side, this constant light emission luminance is a gradation different from that of the organic EL element 6DA side on the side that creates the master deterioration curve, and is set to, for example, an intermediate gradation of the image data D3. . In addition, the dummy pixel control unit 13 stops the feedback control at the update period and outputs drive data D2A and D2B for light emission luminance measurement.

  The master deterioration curve generation unit 19 records and holds the light emission luminance of the organic EL element 6DA detected in this update cycle, and creates a master deterioration curve. Therefore, in this embodiment, the master deterioration curve is a characteristic curve showing the temporal change in the light emission luminance of the dummy organic EL element 6DA.

  Further, the conversion table update unit 20 updates the gradation / degradation amount table 15 based on the light emission luminance of the organic EL elements 6DA and 6DB in this update cycle.

[Prediction principle of deterioration amount]
Here, the deterioration amount when the organic EL element is driven at the gradations L and Lo is proportional to the deterioration rate conversion function g (L, Lo) as shown in the equation (1) and FIG. Therefore, if the inverse function related to the time t of the deterioration curve f (t, L) is set to f ⁻¹ (y, L) and the time required for deterioration of the unit deterioration amount is compared between the gradations Lo and L, the relationship of the following equation is obtained. The formula can be obtained.

  Here, the denominator on the left side of equation (2) indicates the time required for deterioration of the unit deterioration amount in the gradation L, and the denominator on the right side of equation (2) is required for deterioration of the unit deterioration amount in the gradation Lo. Will show the time. Therefore, equation (2) can be rewritten as shown in the following equation.

  The function g (L, Lo) described above is a function indicating the gradation dependence of the deterioration rate, whereas the function 1 / g (L, Lo) in the equation (3) is a unit deterioration amount. This is a function indicating the gradation dependency of the time required for deterioration. Therefore, the deterioration curve y = f (t, L) of the gradation L can be expressed by the following equation. As shown in FIG. 3, the master deterioration curve f (t, L) is equivalent to the function g (L, Lo). Lo) can be regarded as being expanded and contracted in the time axis direction.

  In this embodiment, by utilizing the relationship of the equation (4), the amount of deterioration when the organic EL element is driven at unit time for each gradation is converted into the display time on the master deterioration curve, and each organic EL element is converted. 6 is detected.

[Prediction of deterioration amount by master deterioration curve]
Here, from equation (4), when the organic EL element is driven for a time t at a predetermined gradation L, the amount of deterioration of the organic EL element is the time t / g (L, Lo) at the gradation Lo of the master deterioration curve. It becomes equal to the amount of deterioration when driven.

  On the other hand, the organic EL element 6 provided in the image display unit 4 emits light at various light emission luminances for various times according to the image data D3. Here, it is assumed that the desired organic EL element emits light for the time t (i) at the gradation L (i). As shown by the following equation, the deterioration amount at this time is that the organic EL element emits light at the gradation of the master deterioration curve for the time obtained by dividing the light emission time t (i) by the function g (L (i), Lo). It becomes equal to the case.

  In this case, the emission luminance y is expressed by the following equation.

  Therefore, in this embodiment, the calculation processing of equation (5) is executed based on the recording of the gradation / degradation amount table 15 to detect the deterioration amount of each organic EL element.

[Deterioration function]
Here, the degradation rate of the organic EL element increases as the gradation increases. Therefore, in this embodiment, the function g (L, Lo) is defined by the following equation. Therefore, in this case, if the light emission luminance of the organic EL element is increased by n times, the deterioration rate is also increased by n times, and the time required for deterioration of the unit deterioration amount is reduced by 1 / n times. Therefore, in this case, the gradation / degradation amount conversion table 15 can be easily set.

  However, the deterioration rate of the organic EL element changes at an acceleration with respect to the change in luminance. Therefore, the function g (L, Lo) may be defined by the following equation by the power of the acceleration coefficient α with the ratio of the gradation L to the gradation Lo of the master deterioration curve set at the bottom. In this case, the deterioration amount can be obtained with a small amount of information by a relatively simple calculation.

  Instead of this, the function g (L, Lo) may be defined by the following equation. In this case, even if the time acceleration coefficient α has gradation dependency, the deterioration amount can be obtained with high accuracy. In this case, the time acceleration coefficient α (L) is set so that the value continuously changes with respect to the change in the gradation L, so that the change in the correction amount obtained from the master deterioration curve does not become discontinuous. To.

  Instead of this, as shown by the following equation, the time acceleration coefficient α may be changed by the luminance deterioration amount. Note that the luminance deterioration amount detected from the dummy organic EL element 6DA can be applied to the luminance deterioration amount which is a parameter of the acceleration coefficient. In this case, even if the time acceleration coefficient α is dependent on the luminance deterioration amount, the deterioration amount can be obtained with high accuracy. In this case as well, the time acceleration coefficient α (luminance deterioration amount) is set so that the value continuously changes with respect to the change in luminance deterioration amount so that the change in correction amount does not become discontinuous.

  Instead of these, as shown by the following equation, the acceleration coefficient α may be changed by the gradation L and the luminance deterioration amount.

[Specific prediction of deterioration amount]
Based on the above-described degradation amount prediction principle, in the luminance correction unit 2, the gradation / degradation amount conversion table 15 records and holds the value of the function 1 / g (L, Lo) for each gradation of the image data D3. To do. As shown in FIG. 4, the master deterioration curve generation unit 19 acquires and records the emission luminance y of the dummy organic EL element 6DA detected every update period, so that the master deterioration curve y = f (t, A sampling value of Lo) is acquired and a master deterioration curve is created.

  The deterioration amount calculation unit 14 searches the gradation / deterioration amount conversion table 15 to detect the right side of the equation (5), t (i) / g (L (i), Lo), and the accumulated deterioration amount calculation unit 16. Performs the arithmetic processing of equation (5). As shown in FIG. 4, the correction amount determination unit 12 determines the master deterioration based on the display time t (Σ {t (i) / g (L (i), Lo)}) obtained by the cumulative deterioration amount calculation unit 16. A deterioration amount Δy on the curve is detected, and a correction amount of the corresponding image data is determined.

[Updating gradation / degradation amount conversion table]
Here, if the value of the function 1 / g (L, Lo) set in the gradation / degradation amount conversion table 15 is a fixed value, it corresponds to the variation of the image display panel 3 and the time change of the function g (L, Lo). In the end, the prediction accuracy of the light emission luminance is lowered. Therefore, in the image display device 1, the gradation / deterioration amount conversion table 15 is updated by the conversion table update unit 20 for each update period based on the light emission luminance of the dummy organic EL elements 6DA and 6DB.

  That is, as shown in FIG. 5, when the emission luminances of the dummy organic EL elements 6DA and 6DB are y0 and y1 at a predetermined update time t1, the ratio of these emission luminances y0 and y1 is calculated to obtain the proportionality constant. calculate. The proportionality constant is applied to execute the calculation process of the equation (7), the value of the function 1 / g (L, Lo) at each gradation is calculated, and the gradation / degradation amount conversion table 15 is updated.

  As described above with respect to the equation (8), when the function 1 / g (L, Lo) is defined using the acceleration coefficient α, the acceleration coefficient α can be obtained by the arithmetic processing of the following equation. Therefore, in this case, the calculation processing of the equation (8) is executed using the acceleration coefficient α to calculate the value of the function 1 / g (L, Lo) at each gradation, and the gradation / degradation amount conversion table 15 is updated. To do.

  On the other hand, when the function 1 / g (L, Lo) is defined by the equation (9), the acceleration coefficient α (t) detected by the calculation process of the equation (12) is used for each update period in advance. A coefficient such as a linear function that defines the set acceleration coefficient α (L) is obtained. Further, the value of the function 1 / g (L, Lo) at each gradation is calculated using the obtained coefficient, and the gradation / degradation amount conversion table 15 is updated.

  Further, when the function 1 / g (L, Lo) is defined by the expressions (10) and (11), the acceleration coefficient α (t, L1) detected by the calculation process of the expression (12) for each update period, and the organic Using the degradation amounts of the EL elements 6DA and 6DB, a coefficient such as a linear function that defines a preset acceleration coefficient α (luminance degradation amount) and α (L, luminance degradation amount L) is obtained. Further, the value of the function 1 / g (L, Lo) at each gradation is calculated using the obtained coefficient, and the gradation / degradation amount conversion table 15 is updated.

  Instead of these, when the function 1 / g (L, Lo) is defined by the equations (9) to (11), the acceleration coefficient α (t used for updating the gradation / degradation amount conversion table 15 so far is used. −1, L) may be used to calculate the acceleration coefficient α (t, L) used to update the gradation / degradation amount conversion table 15.

  Specifically, as shown by the following expression, assuming that the ratio of the acceleration coefficients α (t, L) and α (t−1, L) is constant, the acceleration coefficient α ( From t, L1), the acceleration coefficient α (L) of each gradation may be obtained.

  Instead of this, as shown by the following equation, assuming that the difference between the acceleration factors α (t, L) and α (t−1, L) is constant, the acceleration factor obtained by the calculation processing of equation (12) The acceleration coefficient α (L) for each gradation may be obtained from α (t, L1).

[Operation of the embodiment]
In the above configuration, in the image display device 1 (FIG. 2), sequentially input image data D1 is input to the image display panel 3 via the luminance correction unit 2. In the image display panel 3, the light emission luminance of each organic EL element 6 constituting the image display unit 4 is set by the image data D3 input through the luminance correction unit 2, thereby displaying an image based on the image data D1. To do.

  However, the higher the emission luminance of the organic EL element 6 is, the lower the luminous efficiency is as it is used for a long time. As a result, in the image display device, a decrease in emission luminance, a change in chromaticity, and burn-in occur.

  Therefore, in the image display device 1, dummy organic EL elements 6 DA and light receiving elements 7 A are provided in parts other than the image display unit 4 of the image display panel 3, and the light emission luminance of the organic EL elements 6 provided in the image display panel 3. Is monitored by the luminance correction unit 2. Further, based on the monitor result, the luminance correction unit 2 corrects the gradation of the image data D1 used for driving each organic EL element 6, thereby preventing a decrease in light emission luminance, chromaticity variation, and burn-in.

  More specifically, in the image display device 1, the dummy organic EL element 6DA emits light with a constant light emission luminance, and the light emission luminance of the organic EL element 6DA at a predetermined gradation is detected at a constant update period. As a result, the image display apparatus 1 detects a master deterioration curve y = f (t, Lo) that is a reference for gradation correction. In the image display device 1, the deterioration amount of each organic EL element 6 is detected based on the master deterioration curve y = f (t, Lo). In the image display device 1, the gradation of the image data D1 is corrected so as to correct the deterioration amount of each organic EL element 6, and as a result, a decrease in light emission luminance, a change in chromaticity, and a burn-in are prevented.

  However, with the conventional method (the method disclosed in Japanese Patent Laid-Open No. 2007-156044), the deterioration amount of the master deterioration curve y = f (t, Lo) is simply multiplied by the deterioration rate conversion function g (L, Lo). Finding the amount of deterioration causes various inconveniences (see equation (1), FIG. 7).

  That is, when estimating the deterioration of the light emission luminance at each gradation using the relationship of the equation (1), the master deterioration curve y = f (t, Lo) is set to the vertical axis by the deterioration rate conversion function g (L, Lo). The deterioration curve y = f (t, L) of the gradation L is obtained by expanding and contracting in the direction. Therefore, when the emission luminance y due to the master deterioration curve y = f (t, Lo) approaches the value 0 due to the increase in time t, the deterioration curve y = f (t, L) at the gradation L larger than the gradation Lo becomes There is a risk of crossing the value 0. Therefore, in the conventional method, a physical contradiction occurs.

  In the case of the conventional method, the deterioration amount is predicted by selecting the deterioration curve based on the change in gradation of the organic EL element provided in the image display unit. Accordingly, even when there are a plurality of organic EL elements having the same deterioration amount at a predetermined time, and the plurality of organic EL elements are driven at the same gradation, the deterioration amounts are the same for these organic EL elements. There is a case where this cannot be guaranteed. Also in this case, the conventional method causes a physical contradiction.

  As a result, in the conventional method, there is a problem that is not practically sufficient in predicting the deterioration of the light emission luminance in each organic EL element 6, and the image quality deterioration cannot be corrected accurately.

  Therefore, in the image display device 1, the deterioration amount when the organic EL element is driven for each gradation for each unit time using the function 1 / g (L, Lo) indicating the gradation dependency of the time required for the deterioration of the unit deterioration amount. Is converted into a display time on the master deterioration curve, and the gradation / deterioration amount conversion table 15 is created. Further, at a certain time interval, the dummy organic EL element 6DA is driven by the maximum gradation with the fastest deterioration speed, and the master deterioration curve y = f (t, Lo) is obtained. Further, the gradation / deterioration amount table 15 is searched from the image data D3, the deterioration amounts are integrated for each pixel, and the deterioration amount of each pixel converted into the display time of the master deterioration curve y = f (t, Lo) is Accumulated for each pixel. Also, from this cumulative result, the amount of deterioration is obtained from the master deterioration curve (FIG. 4), and the gradation of each pixel is corrected so as to correct this amount of deterioration, thereby reducing the emission luminance, variation in chromaticity, Prevent seizure.

  In this case, in the image display apparatus 1, the master deterioration curve y = f (t, Lo) is expanded and contracted in the time axis direction to obtain the deterioration curve y = f (t, L) for each gradation. Therefore, even if the light emission luminance y approaches 0 as the time t increases, the light emission luminance y of the deterioration curve y = f (t, L) can be set so as not to cross the value 0. Therefore, the physical contradiction in the conventional method can be effectively avoided, and as a result, the deterioration amount can be predicted with high accuracy.

  In addition, regardless of the amount of deterioration of each pixel, the amount of deterioration is predicted on the master deterioration curve. Accordingly, it is possible to reliably ensure that the deterioration amounts are equal for the organic EL elements that are equal in deterioration amount at a predetermined time and are driven at the same gradation. Therefore, the physical contradiction in the conventional method can be effectively avoided also by this.

  As a result, in the image display device 1, the prediction accuracy of the light emission luminance in each organic EL element 6 can be improved as compared with the conventional case, and the decrease in the light emission luminance, the variation in chromaticity, and the burn-in can be surely prevented. Can do.

  However, if the deterioration amount when driving for unit time stored in the gradation / degradation amount conversion table 15 is a fixed value, the variation in the organic EL element 6 and the time change of the function g (L, Lo) cannot be handled. Eventually, the prediction accuracy will decrease.

  Therefore, in the image display apparatus 1, in addition to the dummy organic EL element 6DA and the light receiving element 7A used for generating the master deterioration curve, a dummy organic EL element 6DB and a light receiving element 7B are further provided. Further, in the image display device 1, the value of the function 1 / g (L, Lo) in each gradation is obtained for each update period based on the light emission luminance of these dummy organic EL elements 6DA and 6DB. The quantity conversion table 15 is updated.

  As a result, the image display apparatus 1 updates the deterioration amount when the unit time driving recorded in the gradation / deterioration amount conversion table 15 is performed in response to the variation of the organic EL element 6 and the time change of the function g (L, Lo). It is possible to detect the deterioration amount with higher accuracy.

[Effect of the embodiment]
According to the above configuration, by using the light reception results of the plurality of light receiving elements, the deterioration amount of the unit time of each gradation converted into the display time on the master deterioration curve is sequentially updated, and this amount is changed according to the gradation of the image data. By correcting the emission luminance by accumulating the amount of deterioration per unit time, the prediction accuracy of the emission luminance can be significantly improved as compared with the conventional case.

  A plurality of dummy self-luminous elements are arranged in areas other than the image display area, a master degradation curve is created based on the light reception results of the plurality of dummy self-luminous elements, and the amount of degradation per unit time of each gradation is updated sequentially. Thus, specifically, the prediction accuracy of the degradation of the light emission luminance can be significantly improved as compared with the conventional case.

  Also, by calculating the amount of deterioration converted to the display time on the master deterioration curve by the power of the acceleration coefficient with the gradation ratio to the gradation of the master deterioration curve set at the bottom, When the deterioration rate changes, the amount of deterioration can be obtained with a small amount of information by a relatively simple calculation.

  At this time, by calculating the acceleration coefficient used for updating the gradation / degradation amount conversion table by the arithmetic processing using the acceleration coefficient used for updating the gradation / degradation amount conversion table so far, a simple calculation can be performed. The gradation / degradation amount conversion table can be updated by arithmetic processing.

  In addition, since the self-luminous element is an organic EL element, it can be applied to a flat display device using the organic EL element to prevent luminance deterioration, chromaticity change, and burn-in.

  Further, by emitting emitted light from the self-light emitting element of the dummy pixel to the back side of the image display panel, the configuration of the housing that holds the image display panel can be simplified.

<Second Embodiment>
FIG. 6 is a block diagram showing an image display apparatus according to the second embodiment of the present invention. In this image display device 21, the same configuration as that of the image display device 1 of the first embodiment is denoted by the corresponding reference numeral, and redundant description is omitted.

  In the image display device 21 of this embodiment, the dummy organic EL element 6DA used to create the master deterioration curve is a predetermined gradation other than the highest gradation of the image data D3, and the dummy organic EL element 6DB Are driven with different gradations. The image display device 21 of this embodiment is configured in the same manner as in the first embodiment, except that the configuration relating to the driving of the dummy organic EL element 6DA is different.

  Here, this gradation may be a fixed gradation or may be variously changed together with the dummy organic EL element 6DB. In the case of a fixed gradation, for example, an intermediate gradation or the lowest gradation can be applied. If the dummy organic EL element is driven with a fixed gradation, the system configuration can be simplified.

  On the other hand, when changing the gradation, for example, the gradation may be periodically changed according to a certain pattern, or the gradation may be changed randomly, thereby changing the gradation regardless of the image data D3. . In this case, since the master deterioration curve can be measured in a state close to the actual image display state, the deterioration curve can be predicted with high accuracy. When the gradation is varied, the average gradation of the image data D3, the gradation of the specific pixel of the image display unit, etc. are set, and the gradations of the dummy organic EL elements 6DA and 6DB are varied according to the image data D3. May be. In this case, since the gradation of the dummy organic EL elements 6DA and 6DB can be set according to the image data to be actually displayed, the deterioration curve can be predicted with high accuracy.

  However, when the dummy organic EL elements 6DA and 6DB are driven at a gradation lower than the maximum gradation of the image data D3 in this way, the master deterioration curve is determined from the light reception results of these organic EL elements 6DA and 6DB for the future from the present time. Cannot be generated. As a result, depending on the method of the first embodiment, it is not possible to detect the amount of deterioration on the master deterioration curve for a pixel whose deterioration speed is faster than the master deterioration curve.

  Therefore, in this embodiment, the master deterioration curve generation unit 29 generates a master curve indicating a temporal change in emission luminance when the organic EL elements corresponding to the dummy organic EL elements 6DA and 6DB emit light at a constant gradation. Record and hold. In the case where the dummy organic EL elements 6DA and 6DB are displayed at a fixed gradation, it is desirable that the gradation of the master curve is equal to the fixed gradation, but these gradations are set to be different. May be. The master deterioration curve generation unit 29 generates a master deterioration curve up to the current time point based on the light emission luminance of the dummy organic EL elements 6DA and 6DB detected in the update period. The master deterioration curve generation unit 29 corrects the master curve and generates a master deterioration curve after the current time point.

  Specifically, as shown by the following equation, the master deterioration curve generation unit 29 multiplies the master curve luminance value F (t, Lo) by a predetermined ratio to obtain a master deterioration curve f (t, Lo) after the current time point. ) Is generated. Here, this ratio is a ratio between the luminance value F (To, Lo) of the master curve and the luminance value f (To, Lo) of the master deterioration curve at the current time To.

  Alternatively, as shown by the following equation, the amount of deterioration of the master deterioration curve (1-f (To, Lo)) and the amount of deterioration of the master curve (1-F (To, Lo)) at the current time To The master deterioration curve f (t, Lo) after the current time point may be generated by multiplying the deterioration amount (1-F (t, Lo)) of the master curve by the ratio.

  Alternatively, as shown by the following equation, a master deterioration curve after the current time point may be generated by adding a predetermined value to the luminance value F (t, Lo) of the master curve. Here, the predetermined value is a difference value (f (To, Lo) −F (To, Lo)) of the luminance value at the current time To.

  Instead of this, as shown by the following equation, the difference value ((1-f (To, Lo))-(1-F (To, Lo))) of the deterioration amount at the current time To is added to obtain the master. A deterioration curve f (t, Lo) may be generated.

  When the dummy organic EL element 6DA used for creating the master deterioration curve emits light at the gradation Lo lower than the highest gradation of the image data D3 in this way, the acceleration coefficient α of the gradation L higher than the gradation Lo. Is calculated based on the light reception result of low gradation. Therefore, in this case, the acceleration coefficient α is calculated by applying the methods of formulas (12) to (13), and the prediction accuracy of the light emission luminance can be ensured by a simple calculation process.

  According to this embodiment, by generating the master deterioration curve by setting the gradation of the dummy pixels in various ways, it is possible to predict the light emission luminance deterioration amount with higher accuracy.

  In addition, by generating a master deterioration curve after the current time using the master curve, it is possible to maintain the continuity of the master deterioration curve and accurately predict the amount of deterioration of the light emission luminance even for pixels with a high deterioration rate. it can.

<Third Embodiment>
In the image display device of this embodiment, the light-emitting luminance of the organic EL element of the image display unit is detected instead of the organic EL element of the dummy pixel by the light receiving element arranged in the vicinity of the image display unit. The image display apparatus according to this embodiment is configured in the same manner as the first or second embodiment described above except that the configuration relating to the light receiving element is different.

  For this reason, the image display device switches the operation mode, for example, when the image display device is turned on, and displays a predetermined pattern for measuring the deterioration amount of the light emission luminance on the image display unit. A master deterioration curve is generated based on the light reception result of the predetermined pattern. At the same time, the gradation / degradation amount conversion table is updated. Therefore, in this case, a master deterioration curve is created at variable time intervals, and the gradation / deterioration amount conversion table is updated. In this case, the luminance can be detected stably at a specific gradation.

  Alternatively, a series of processes such as monitoring the gradation of the image data and detecting the emission luminance and generating a master deterioration curve when the image data has a specific gradation may be executed. Good.

  Alternatively, a series of data such as recording and holding data indicating the gradation dependence of the light emission luminance, correcting the light emission luminance detected via the light receiving element with this data, and generating a master deterioration curve, etc. Processing may be executed.

In this embodiment, instead of the dummy organic EL element, it is possible to predict the deterioration of the light emission luminance with higher accuracy by detecting the light emission luminance of the image display unit.
<Modification>
In the first and second embodiments described above, the case where the organic EL element of the image display unit and the organic EL element of the dummy pixel are formed by the top emission method and the bottom emission method has been described. However, the present invention is not limited to this, and the organic EL element of the image display unit and the organic EL element of the dummy pixel may be created by the bottom emission method and the top emission method.

  If the configuration of the housing in which the image display panel is arranged can be simplified practically, for the dummy pixel organic EL element, both the upper and lower electrodes sandwiching the organic EL layer are made of transparent electrodes, The emitted light may be emitted to both the emission surface and the back surface. Moreover, you may produce both the organic EL element of an image display part, and the organic EL element of a dummy pixel by a top emission system or a bottom emission system.

  Further, in the first and second embodiments described above, the case where the light receiving element is disposed on the back surface of the image display panel has been described. However, the present invention is not limited to this and may be disposed in the image display panel.

  In the first and second embodiments described above, the case has been described in which the deterioration amount is detected by searching the gradation / deterioration amount conversion table using the image data whose gradation has been corrected by the correction unit. However, the present invention is not limited to this, and the deterioration amount may be detected by searching the gradation / deterioration amount conversion table based on the image data before correcting the gradation by the correction unit. In this case, the emission luminance feedback control by the dummy pixel control unit 13 may be stopped so as to correspond to the detection of the deterioration amount by the image data before the gradation is corrected by the correction unit.

  In the above-described embodiment, the case where the correction value is set by accumulating the deterioration amount for each pixel has been described. However, the present invention is not limited to this, and may be widely applied to the case where the correction value is set by accumulating the deterioration amount for each of a plurality of pixels, or the case where the correction value is set in common for the entire screen of the image display panel. it can.

  Further, in the above-described embodiment, the case has been described in which the deterioration amount when the organic EL element is caused to emit light at all gradations is stored in the table. However, the present invention is not limited to this, and in the case where sufficient accuracy can be secured in practice, the deterioration amount is stored in a table for each of the plurality of gradations, and the deterioration amount of each pixel is used using the deterioration amount for each of the plurality of gradations. May be predicted.

  In the above-described embodiment, the case where the gradation / degradation amount conversion table is set in common for the pixels in the image display area has been described. However, the present invention is not limited to this, and the gradation / degradation amount conversion table may be set for each area set by dividing the image display area. Correspondingly, the function 1 / g is set for each area. (T, L) and the acceleration coefficient α may be calculated.

  In the above-described embodiment, the case where the correction amount is set for each frame has been described. However, the present invention is not limited to this. For example, the correction amount may be set in units of a plurality of frames by searching the gradation / degradation amount conversion table using the average luminance of a plurality of frames.

  In the first and second embodiments described above, the case where the light emission luminance of all the pixels provided in the image display panel is corrected based on the light reception results of the two dummy pixels has been described. However, the present invention is not limited to this, and the present invention can be widely applied to a case where the image display panel is divided into predetermined regions and dummy pixels are provided for each region to correct the light emission luminance. Alternatively, the present invention can be widely applied to a case where dummy pixels are provided for each color and the light emission luminance of each color is corrected with the corresponding light reception result.

  In the above-described embodiment, the case where the light emission luminance of the corresponding region is corrected by the light reception results of the two light receiving elements has been described. However, the present invention is not limited to this, and the light emission luminance of the corresponding region may be corrected by the light reception results of three or more light receiving elements.

  Further, in the above-described embodiment, the case where the image display panel is configured by the self-luminous element by the organic EL element has been described. However, the present invention is not limited to this, and the case where the image display panel is configured by various self-luminous elements. Can be widely applied.

  In the above-described embodiments, the configuration of each suitable image display device has been described. However, the present invention is not limited to these configurations, and the above-described configuration may be combined as necessary to configure the image display device. .

  The present invention can be applied to an active matrix image display device using a self-luminous element such as an organic EL (Electro Luminescence) element.

It is a block diagram which shows the detailed structure of the image display apparatus of the 1st Embodiment of this invention. It is a figure which shows the image display apparatus of the 1st Embodiment of this invention. It is a characteristic curve figure which shows the relationship between a master deterioration curve and a deterioration curve. It is a characteristic curve figure with which it uses for description of the detection of deterioration amount. It is a characteristic curve figure with which it uses for description of calculation of an acceleration coefficient. It is a block diagram which shows the image display apparatus of the 2nd Embodiment of this invention. It is a characteristic curve figure with which it uses for description of the detection of the deterioration amount by a conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 ... Image display apparatus, 2 ... Luminance correction part, 3 ... Image display panel, 6, 6DA and 6DB ... Organic EL element, 7A and 7B ... Light receiving element, 12 ... Correction amount determination part, 15... Gradation / degradation amount conversion table, 16... Cumulative deterioration amount calculation unit, 19.

Claims (7)

An image display panel for displaying image data by a self-luminous element;
A light receiving element for receiving light emitted from the image display panel;
A brightness correction unit that processes a light reception result of the light receiving element and corrects a gradation of the image data displayed on the image display panel;
The brightness correction unit
A master deterioration curve generation unit that generates a master deterioration curve indicating a temporal change in light emission luminance of the self-light-emitting element based on the light reception result;
A gradation / degradation amount conversion table in which a deterioration amount when the self-light-emitting element is driven for a unit time for each predetermined gradation of the image data is recorded with a deterioration amount converted into a display time on the master deterioration curve;
A deterioration amount calculation unit that searches the gradation / degradation amount conversion table and detects a deterioration amount corresponding to the gradation of the image data;
A cumulative deterioration amount calculation unit that calculates the cumulative deterioration amount by accumulating the deterioration amount detected by the deterioration amount calculation unit;
A correction amount determination unit configured to detect a display time deterioration amount corresponding to the cumulative deterioration amount from the master deterioration curve and set a correction amount of the image data;
The light receiving elements are a plurality of light receiving elements that respectively receive light emitted from self-light emitting elements having different emission luminances,
The correction amount determination unit
An image display apparatus comprising: a conversion table update unit that updates the gradation / degradation amount conversion table based on light reception results of the plurality of light receiving elements. The image display panel is
The self-light-emitting elements are arranged in a matrix to form an image display unit, and a plurality of dummy self-light-emitting elements are arranged in a portion other than the image display unit,
The plurality of light receiving elements are:
The image display device according to claim 1, wherein each of the dummy light-emitting elements is a light-receiving element that receives light emitted from the dummy self-light-emitting element. The conversion table update unit
Degradation in which the amount of degradation when the self-luminous element is driven per unit time is converted into display time on the master degradation curve by the power of the acceleration coefficient set at the bottom of the ratio of the gradation to the gradation of the master degradation curve The image display device according to claim 1, wherein an amount is calculated and the gradation / degradation amount conversion table is updated. The conversion table update unit
Intermittently updating the gradation / degradation amount conversion table,
The acceleration coefficient used for updating the gradation / deterioration amount conversion table is calculated by arithmetic processing using the acceleration coefficient used for updating the gradation / deterioration amount conversion table until then. Image display device. The image display device according to claim 3, wherein the self-luminous element is an organic EL element. The dummy self-luminous element is
Emission light is emitted to the back side of the image display panel,
The image display device according to claim 3, wherein the light receiving element is disposed on a back side of the image display panel. An image display panel for displaying image data by a self-luminous element;
In a method for driving an image display device comprising a light receiving element that receives light emitted from the image display panel,
A luminance correction step of processing a light reception result of the light receiving element and correcting a gradation of image data displayed on the image display panel;
The brightness correction step includes
Based on the light reception result, a master deterioration curve generation step for generating a master deterioration curve indicating a temporal change in light emission luminance of the self-light-emitting element;
Search the gradation / degradation amount conversion table in which the degradation amount when the self-luminous element is driven for a unit time for each predetermined gradation of the image data is recorded with the degradation amount converted into the display time on the master degradation curve. A deterioration amount calculating step for detecting a deterioration amount corresponding to the gradation of the image data;
A cumulative deterioration amount calculating step of calculating the cumulative deterioration amount by accumulating the deterioration amount detected in the deterioration amount calculating step;
A correction amount determining step of detecting a deterioration amount of display time corresponding to the cumulative deterioration amount from the master deterioration curve and setting a correction amount of the image data,
The light receiving elements are a plurality of light receiving elements that respectively receive light emitted from self-light emitting elements having different light emission luminances,
The correction amount determining step includes:
A method for driving an image display apparatus, comprising: a conversion table updating step for updating the gradation / degradation amount conversion table based on light reception results of the plurality of light receiving elements.

Images