JP2010237528A - Image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display for easily and accurately suppressing luminance unevenness in a display screen with a simple configuration. <P>SOLUTION: The image display includes a plurality of light emitting elements and a storage part for storing relation data indicative of relations between a voltage applied to both ends of the light emitting element and a value related to the emission luminance of the light emitting element. The image display also includes a detection part for detecting a voltage applied to both ends of the light emitting element when a reference current flows through the light emitting element, and a derivation part for deriving a value related to a predicted emission luminance of each light emitting element based on the relation data and the voltage detected by the detection part. Furthermore, the image display also includes a setting part for setting a correction value to each light emitting element so that the difference between the maximum value and the minimum value in values related to a plurality of the predicted emission luminances derived by the derivation part is narrowed, and a correction part for correcting an image signal corresponding to each light emitting element based on the correction value set by the setting part to each light emitting element. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image display device.

  2. Description of the Related Art Conventionally, an image display device including an organic EL (Electroluminescence) element using current emission is known. In such an image display device, a self-luminous light emitting element such as an organic EL element and a driving transistor are connected in series, and the current flowing through each light emitting element is adjusted to adjust the light emission luminance of each light emitting element. Is done. In addition, in a self-luminous light emitting element such as an organic EL element, deterioration proceeds due to current emission, and light emission luminance with respect to the same voltage gradually decreases. Since the degree of progress of the deterioration of the light emitting element is different for each light emitting element, luminance unevenness due to so-called burn-in or the like is caused on the display screen.

  To solve such a problem, by obtaining an integral value related to the light emission time of the light emitting element and correcting the image signal according to the integral value and the deterioration characteristics of the light emitting element over time, the luminance of the light emitting element is obtained. A technique for compensating for deterioration has been proposed (for example, Patent Document 1). Further, a technique for correcting an image signal in consideration of lighting intensity of a light emitting element (for example, Patent Document 2) and a technique for correcting an image signal in consideration of a temperature characteristic of the light emitting element (for example, Patent Document 3) are proposed. Has been.

  In addition, a technique for compensating luminance degradation of a light emitting element by correcting an image signal according to the cumulative amount of energized electricity in the light emitting element (for example, Patent Document 4), corresponding to an integral value related to the display time of the light emitting element. Thus, a technique (for example, Patent Document 5) that compensates for luminance degradation of the light emitting element by changing the power supply voltage has been proposed. In addition, a technology that compensates for luminance deterioration of a light-emitting element by providing a photosensor in each pixel and generating a pixel control signal so that a parameter measured by the photosensor reaches a target value (for example, a patent) Documents 6 and 7) have been proposed. In addition, a technique for compensating for luminance deterioration of a light emitting element by correcting a difference between voltages applied to the driving transistor and the light emitting element based on the sum of currents flowing through the light emitting elements is proposed. (For example, patent document 8). In addition, a technique has been proposed that compensates for luminance degradation of a light emitting element by correcting an input image signal based on a correction signal corresponding to the total current consumed by the display (for example, Patent Document 9).

JP 2002-6796 A JP 2002-175041 A JP 2004-70349 A JP 2005-55800 A JP 2003-280583 A Special table 2007-535683 gazette Special table 2008-505366 JP-A-2005-300929 Special table 2008-523624

  However, for example, in Patent Document 1 described above, a mode in which the light emission luminance of the light emitting element decreases in proportion to an increase in the integral value of the light emission time of the light emitting element is employed. However, the decrease in light emission luminance due to the deterioration of the light emitting element is often not proportional to the increase in the integrated value of the light emission time. That is, the degree of decrease in the light emission luminance with respect to the increase in the integrated value of the light emission time varies greatly depending on the magnitude of the integrated value of the light emission time. In addition, there is a case where a decrease in light emission luminance due to deterioration of the light emitting element proceeds in an unstable manner so as to wave with the passage of time. Therefore, it is difficult to accurately predict a decrease in light emission luminance in the light emitting element from the integrated value related to the light emission time of the light emitting element, and luminance unevenness in the display screen cannot be accurately suppressed. Note that, in the techniques of Patent Documents 2 and 3, since the progress of the deterioration of the light emission luminance is expressed in multiple stages, the decrease in the light emission luminance in the light emitting element is accurately predicted from the integrated value related to the light emission time of the light emitting element. Difficult to do.

  In Patent Document 4, the light emitting element is unstable such that the light emission luminance does not decrease in proportion to the increase in the cumulative value of the energized electricity, or the light emission luminance undulates with respect to the increase in the cumulative value of the energized electricity. However, there is no mention of accurately predicting a decrease in light emission luminance in the light emitting element in a case where the light emission element decreases. In Patent Document 5, there is no mention of accurately predicting a decrease in light emission luminance in the light emitting element.

  In addition, as in the techniques of Patent Documents 6 and 7, it is difficult to design each pixel with a photosensor, and the process for suppressing the luminance unevenness is complicated. Can not do it. In addition, as in the technique of Patent Document 8 described above, when luminance degradation of a light emitting element is compensated by correcting the same voltage for all the light emitting elements at once, luminance unevenness on the display screen is accurately corrected. It cannot be suppressed. Further, in the technique of Patent Document 9 mentioned above, there is no mention of accurately suppressing luminance unevenness on the display screen in accordance with the degree of progress of deterioration of the light emitting element that differs for each light emitting element.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image display device capable of accurately suppressing luminance unevenness on a display screen.

  In order to solve the above-mentioned problem, an image display device according to a first aspect of the present invention includes a plurality of light emitting elements, a voltage applied to both ends of the light emitting elements, and a value related to light emission luminance of the light emitting elements. A storage unit that stores relationship data indicating the relationship. Further, the image display device is based on a detection unit that detects a voltage applied to both ends of the light emitting element when a reference current flows through the light emitting element, the relation data, and a voltage detected by the detection unit. And a deriving unit for deriving a value related to the predicted light emission luminance of each of the light emitting elements. Further, the image display device is configured to set a correction value for each light emitting element so that a difference between a maximum value and a minimum value among the plurality of values related to the predicted light emission luminance derived by the deriving unit is reduced. And a correction unit that corrects an image signal corresponding to each light emitting element based on the correction value set for each light emitting element by the setting unit.

  ADVANTAGE OF THE INVENTION According to this invention, the image display apparatus which can suppress the brightness nonuniformity in a display screen accurately can be provided.

It is a figure which shows the functional structure of the image display apparatus which concerns on 1st and 2nd embodiment. It is a figure which shows the structure of the pixel circuit which concerns on 1st and 2nd embodiment. It is a figure which shows the relationship between the drive time in a light emitting element, and normalization brightness | luminance. It is a figure which shows the relationship between the drive time and drive voltage in a light emitting element. It is a figure which shows the relationship between the drive voltage and current density in a light emitting element. It is a figure which shows the relationship between the drive voltage and light emission luminance in a light emitting element. It is a figure which shows the relationship between the drive time and current density in a light emitting element. It is a figure which shows the relationship between the drive time in a light emitting element, and light emission luminance. It is a figure which shows the structural structure which concerns on the control part of 1st Embodiment. It is a figure which shows approximately the relationship between the drive time in a light emitting element, and normalization brightness | luminance. It is a flowchart which shows the setting operation | movement flow of a correction coefficient. It is a flowchart which shows the setting operation | movement flow of a correction coefficient. It is a flowchart which shows the setting operation | movement flow of a correction coefficient. It is a flowchart which shows the setting operation | movement flow of a correction coefficient. It is a flowchart which shows the setting operation | movement flow of a correction coefficient. It is a figure which shows the relationship between the drive time in a light emitting element, and normalization brightness | luminance. It is a figure which shows the relationship between the drive time and drive voltage in a light emitting element. It is a figure which shows the structural structure which concerns on the control part of 2nd Embodiment. It is a figure which shows approximately the relationship between the drive time in a light emitting element, and normalization brightness | luminance. It is a flowchart which shows the setting operation | movement flow of a correction coefficient.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<(1) First Embodiment>
<(1-1) Schematic configuration of image display device>
As shown in FIG. 1, the image display device 1 according to the first embodiment of the present invention includes a control unit 2, a storage unit 3, a display unit 4, a power supply circuit 5, and a voltage detection unit 6.

  The control unit 2 controls the operation of the display unit 4 and processes image signals. The control unit 2 includes, for example, a CPU and a RAM, and implements various functions by executing a program stored in the storage unit 3 by the CPU. Various functions of the control unit 2 may be realized by a dedicated electronic circuit or the like.

  The storage unit 3 is configured by a non-volatile memory or the like, and stores various data and the like for realizing various functions in the control unit 2.

The display unit 4 has a substantially rectangular outline, and a plurality of pixel circuits 41 are arranged in a matrix. Each pixel circuit 41 includes, for example, an organic light-emitting diode OLED as a self-luminous light-emitting element that emits light by passing a current through the organic material. The plurality of pixel circuits 41 include a pixel circuit that emits red light, a pixel circuit that emits green light, and a pixel circuit that emits blue light. The display unit 4 is provided with a plurality of image signal lines L _DATA and a plurality of scanning signal lines L _SEL so as to be substantially orthogonal to each other. An image signal line L _DATA is provided for each line (vertical line) of the pixel circuits 41 arranged in the vertical direction, and a scanning signal line L _SEL is provided for each line (horizontal line) of the pixel circuits 41 arranged in the horizontal direction. Provided.

In the display unit 4, the output image signal S _OUT is transmitted to the pixel circuit 41 via the image signal line L _DATA by an X driver arranged along one side (long side or short side) of the display unit 4. Supplied as appropriate. In addition, a scanning signal is applied to the scanning signal line L _SEL by a Y driver arranged along another side (short side or long side) of the display unit 4. This scanning signal is a signal for controlling the timing of supplying the output image signal S _OUT to each pixel circuit 41 via each image signal line L _DATA . The display unit 4 is provided with power supply lines L _VDD and L _VSS and a compensation control signal line L _TH for each horizontal line.

The power supply circuit 5 supplies power supplied from a power supply (for example, a DC power supply such as a battery) to each pixel circuit 41 included in the display unit 4. Specifically, when a voltage is applied between the power supply line _LVDD and the power supply line _LVSS , the voltage is supplied to both ends of each organic light emitting diode OLED, and each organic light emitting diode OLED emits light. The voltage applied between the power supply line L _VDD and the power supply line L _VSS is adjusted by the Y driver. Note that the potential applied to the compensation control signal line L _TH is also adjusted by the Y driver. The power supply circuit 5 also functions as a circuit (constant current drive circuit) that supplies a constant current to each pixel circuit 41 in response to an instruction from the control unit 2.

The voltage detector 6 detects a voltage (drive voltage) applied to both ends of each organic light emitting diode OLED. The current flowing through the organic light emitting diode OLED can be obtained by detecting the voltage across the resistor R1 provided in each pixel circuit 41. For example, the driving voltage applied to both ends of the organic light emitting diode OLED is controlled by the control unit 2 so that a reference current (reference current) flows in the organic light emitting diode OLED, and the driving voltage V _REAL when the reference current flows. Is detected. Information indicating the drive voltage V _REAL is sent to the control unit 2. The control unit 2 appropriately sets a correction coefficient C _V corresponding to the drive voltage V _REAL detected by the voltage detection unit 6 so that luminance unevenness corresponding to the deterioration of the organic light emitting diode OLED does not occur in the display unit 4. Then, the input image signal is multiplied by the correction coefficient _CV . This luminance unevenness suppressing process will be further described later.

<(1-2) Pixel circuit configuration>
As shown in FIG. 2, the pixel circuit 41 includes an organic light emitting diode OLED, a first transistor T _DR , a second transistor T _TH , a third transistor T _SEL , a first capacitor C1, a second capacitor C2, and a resistor R1. Prepare. In FIG. 2, the direction of current flow when the organic light emitting diode OLED emits light is indicated by an arrow Ar1.

The anode electrode of the organic light emitting diode OLED is electrically connected to the power supply line _LVDD via the first transistor _TDR and the resistor R1 in order. Further, the cathode electrode of the organic light emitting diode OLED is electrically connected to the power supply line L _VSS . Specifically, the first electrode of the first transistor T _DR, is electrically connected to the power supply line L _VDD via a resistor R1, the other electrode of the first transistor T _DR, the organic light emitting diode OLED It is electrically connected to the anode electrode. Incidentally, when the light-emitting organic light emitting diode OLED, with higher than the potential of the potential applied to the power supply line L _VDD is applied to the power line L _VSS, the one electrode of the first transistor T _DR serves as a drain the other electrode of the first transistor T _DR acts as the source.

The driving voltage applied to both ends of the organic light emitting diode OLED is obtained by detecting the potential difference between the node T _A and the power supply line L _{VSS in} FIG. 2 by the voltage detection unit 6 configured by a sample hold circuit or the like. . In order to selectively connect the node T _A of each pixel circuit 41 to the voltage detector 6, a known switch circuit or scanner circuit may be used, or a plurality of switches are provided in the voltage detector 6. A sample hold circuit may be provided. Alternatively, the transistors of the purpose of selecting the node T _A may be further provided configured to each pixel circuit 41.

The second transistor _TTH is provided between the gate of the first transistor _TDR and the other electrode. More specifically, the the one electrode of the second transistor T _TH is electrically connected to the gate of the first transistor T _DR, the other electrode of the second transistor T _TH to the other electrode of the first transistor T _DR Are electrically connected to each other. The gate of the second transistor _TTH is electrically connected to the compensation control signal line _LTH .

The first electrode of the first capacitor C1, is electrically connected to the image signal line L _DATA via the third transistor T _SEL, the other electrode of the first capacitor C1, the gate of the first transistor T _DR Electrically connected. That is, the gate of the first transistor T _DR is, are electrically connected to the other electrode of the first capacitor C1, the image signal line L _DATA via the first capacitor C1 and the third transistor T _SEL Electrically connected. Specifically, one electrode of the third transistor T _SEL is electrically connected to the image signal line L _DATA , and the other electrode of the third transistor T _SEL is connected to one electrode of the first capacitor C1. Are electrically connected. The gate of the third transistor T _SEL is electrically connected to the scanning signal line L _SEL .

The second capacitor C2 is provided between one electrode of the first capacitor C1 and the other electrode of the first transistor _TDR . Specifically, one electrode of the second capacitor C2 is electrically connected to one electrode of the first capacitor C1 and the other electrode of the third transistor _TSEL , and the other electrode of the second capacitor C2 is Electrically connected to the other electrodes of the first transistor _TDR and the second transistor _TTH .

The first transistor T _DR, depending on the setting voltage (gate voltage) between a potential relative to the and said other electrode gate of the other electrode, to adjust the current flowing through the organic light emitting diode OLED.

Current flowing through the organic light emitting diode OLED is determined by detecting the voltage across the resistor R1 provided in each pixel circuit 41, more specifically, the node T _R and the power supply line L _VDD in FIG The potential difference is obtained by being detected by a voltage detector 6 configured by a sample hold circuit or the like. To selectively connected to the voltage detecting unit 6 nodes T _R of each pixel circuit 41 may be a known switching circuit or scanner circuits, in the voltage detection unit 6, comprising a plurality of switches A sample hold circuit may be provided. Alternatively, the transistors of the purpose of selecting the node T _R may be further provided configured to each pixel circuit 41.

The second transistor _TTH sets the gate voltage of the first transistor _TDR to a so-called threshold voltage immediately before applying the potential of the output image signal to the gate of the first transistor _TDR via the first capacitor C1. . The third transistor T _SEL sets a potential corresponding to the output image signal between one electrode of the first capacitor C1 and one electrode of the second capacitor C2 by applying a potential from the image signal line _LDATA . That is, when the light-emitting organic light emitting diode OLED, a gate voltage of the first transistor T _DR corresponds to the set threshold voltage between the other electrode of the gate and the first capacitor C1 of the first transistor T _DR The voltage corresponds to the potential obtained by adding the potential and the potential corresponding to the output image signal set between one electrode of the first capacitor C1 and one electrode of the second capacitor C2.

<(1-3) Aspect of deterioration of light emitting element>
As a specific example, the deterioration mode of the organic light emitting diode OLED that emits red light will be described.

Here, the organic light emitting diode OLED emitting red light has a first electrode layer as an anode electrode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a second electrode as a cathode electrode. Eight layers of layers and organic protective layers are laminated in this order. Specifically, the first electrode layer is a layer having a thickness of 70 nm formed by sputtering an aluminum alloy containing neodymium. The hole injection layer is a vapor deposition layer made of a triphenylene derivative having a thickness of 7 nm. The hole transport layer is a vapor deposition layer made of an aromatic amine derivative having a thickness of 45 nm. The light emitting layer is a co-deposited film having a thickness of 22 nm in which a host material contains a substance that emits red fluorescence as a dopant material. Note that the concentration of the dopant material in the light emitting layer is 1.1%. The electron transport layer is a vapor deposition layer made of tris (8-quinolinolato) aluminum (Alq3) having a thickness of 55 nm. The electron injection layer is a vapor deposition layer made of lithium fluoride having a thickness of 0.5 nm. The second electrode layer is a co-deposited layer made of magnesium and silver having a thickness of 20 nm. The organic protective layer is a vapor deposition layer made of an aromatic amine derivative having a thickness of 70 nm. In addition, the area of a light emission part is set to 0.36 cm < ² > by making the light emission part (light emission part) of the organic light emitting diode OLED into the substantially square shape whose one side is 6 mm.

  Here, conditions for observing the deterioration mode of the organic light emitting diode OLED will be described. The light emission luminance of the organic light emitting diode OLED was measured using a general luminance meter. Further, a voltage (drive voltage) V applied to the organic light emitting diode OLED was detected. Furthermore, the current density in the organic light emitting diode OLED was detected by detecting the current flowing through the resistor R1.

Then, the organic light emitting diode OLED was connected to a constant current driving circuit, and a constant current of 10.8 mA was set to flow so that the current density in the organic light emitting diode OLED was 30 mA / cm ² . The light emission luminance (initial light emission luminance) L ₀ when the organic light emitting diode OLED started to emit light (at the start of driving) was 3882 cd / m ² , but after 3132 hours from the start of light emission, the light emission luminance became the initial light emission luminance. It was reduced to a value of about 38% of the L _0. Regarding the temperature around the organic light emitting diode OLED at the time of measurement, as a result of automatic measurement, the average temperature during the measurement period was 28.2 ° C, the minimum temperature was 21.0 ° C, and the maximum temperature was 34.0 ° C. It was. The temperature of the first quartile located between the lowest temperature and the highest temperature was 25.0 ° C., and the temperature of the third quartile was 32.5 ° C. For this reason, half of the measured temperature values in the measurement period are included in the range of the first and third quartiles, so the observation was performed under conditions close to the standard indoor environment. Become.

Based on the measurement results under such measurement conditions, a value (L / L ₀ ) obtained by dividing the emission luminance L at each time point by the initial emission luminance L ₀ was calculated as the normalized luminance. As a result, the relationship between the elapsed time (drive time) t from the start of light emission and the normalized luminance L / L ₀ is as shown in FIG. Further, the relationship between the drive time t and the drive voltage V is as shown in FIG.

  Further, during the measurement, every time about 100 hours passed, the relationship between the driving voltage and the current density and the relationship between the driving voltage and the light emission luminance were measured. FIG. 5 shows the relationship between the drive voltage and current density, and FIG. 6 shows the relationship between the drive voltage and light emission luminance. In FIGS. 5 and 6, the measurement result at the start of driving is a black diamond plot, the measurement result after 600 hours from the start of driving is a black triangle plot, and the measurement after 1000 hours from the start of driving is measured. The result is a white diamond plot, the measurement result after 1665 hours from the start of driving is a black square plot, the measurement result after 2065 hours from the start of driving is a white triangular plot, and the time is 2665 hours from the start of driving. The measurement results after the passage are shown as white circle plots, and the measurement results after 3065 hours from the start of driving are shown as white square plots.

As shown in FIG. 5, the current density at a certain driving voltage gradually decreased as the driving time increased. And in the time slot | zone which passed 1800 hours or more from the measurement start which is the latter stage of measurement, the fall amount of the current density was remarkably large. Further, as shown in FIG. 6, the light emission luminance at a certain driving voltage gradually decreased as the driving time became longer. And in the time slot | zone which passed 1800 hours or more from the measurement start which is the latter stage of measurement, the fall amount of the light-emission brightness was remarkably large. 5 and FIG. 6, when the current density and the light emission luminance at the same driving voltage are compared, the decrease amount of the light emission luminance is relatively larger than the decrease amount of the current density. I understood. Incidentally, as shown in Figure 6, for example, in order to realize a light emission luminance of 2000 cd / m ² is necessary driving voltage of the driving start time (drive time t = 0h) at about 5V is drive time t It was found that a driving voltage of about 7V was required at the time of = 2665h (time), and a driving voltage of about 9.5V was required at the time of the driving time t = 3065h.

Further, the relationship between the drive time and the current density at a predetermined drive voltage is as shown in FIG. 7, and the relationship between the drive time and the light emission luminance at a predetermined drive voltage is as shown in FIG. It became. 7 and 8, the measurement result when the drive voltage is 5.5V is a white circle plot, the measurement result when the drive voltage is 6.5V is a white triangle plot, and The measurement results when the drive voltage is 7.5 V are respectively shown as white square plots. As shown in FIG. 7, the current density gradually decreased as the driving time increased with respect to a constant driving voltage. And in the time slot | zone which passed 1800 hours or more from the measurement start which is the latter stage of measurement, the fall amount of the current density was remarkably large. Further, as shown in FIG. 8, the light emission luminance gradually decreased as the driving time became longer with respect to a constant driving voltage. And in the time slot | zone which passed 1800 hours or more from the measurement start which is the latter stage of measurement, the fall amount of the light-emission brightness was remarkably large. As shown in FIG. 8, for example, in order to realize a light emission luminance of 3000 cd / m ² , a driving voltage of about 5.5 V is necessary at a time around driving time t = 750 h, and the driving time It was found that a driving voltage of about 6.5 V is necessary at a time around t = 2300 h, and a driving voltage of about 7.5 V is needed at a time around t = 2700 h.

<(1-4) Configuration related to luminance unevenness suppression processing>
As shown in FIG. 9, the control unit 2 includes a predicted light emission luminance deriving unit 21, a reference value determining unit 22, a correction value setting unit 23, a signal correction unit 24, as a functional configuration related to the luminance unevenness suppression process. And a gamma (γ) converter 25. In addition, the storage unit 3 stores first function data 31, second function data 32, and a correction value table 33 as data related to luminance unevenness suppression processing.

The first function data 31 is data of a function showing the relationship between the organic light emitting diode according to the OLED driving time t and the normalized luminance L / L ₀ as shown in FIG. 3 approximately. The second function data 32 is data describing the relationship between the drive time t and the drive voltage V related to the organic light emitting diode OLED as shown in FIG. Therefore, in the present embodiment, the first function data 31 and the second function data 32 are the voltage applied to both ends of the organic light emitting diode OLED (here, the driving voltage V) and the light emission luminance of the organic light emitting diode OLED. Is data (relation data) indicating the relationship with the value (here, normalized luminance L / L ₀ ). The correction value table 33 describes a correction coefficient C _V as a correction value set for each pixel circuit 41 by the correction value setting unit 23.

The predicted light emission luminance deriving unit 21 serving as a deriving unit is based on the driving voltage V _REAL when the reference current flows through the organic light emitting diode OLED, the first function data 31, and the second function data 32. A value related to the predicted light emission luminance (here, normalized luminance L / L ₀ ) is derived. Here, out of the standardized luminance L / L ₀ of each derived organic light emitting diode OLED, the standardized luminance (maximum value of standardized luminance) of the organic light emitting diode OLED at which the drive voltage V _REAL is minimized is represented by L _{In addition to max} , the normalized luminance (minimum value of normalized luminance) of the organic light emitting diode OLED that maximizes the drive voltage V _REAL is defined as L _min .

The reference value determination unit 22 determines the reference value TH _S based on at least one of the maximum normalized luminance value L _max and the minimum normalized luminance value L _min derived by the predicted emission luminance deriving unit 21. decide. The method for determining the reference value TH _S varies depending on the minimum value L _min of the normalized luminance.

Correction value setting unit 23, based on the reference value TH _S, so that the difference between the maximum value L _max and the minimum value L _min of a plurality of normalized luminance L / L ₀ is derived in the prediction emission luminance deriving unit 21 is shortened In addition, a correction coefficient C _V as a correction value is set for each organic light emitting diode OLED. Specifically, the correction value setting unit 23 obtains correction for each organic light emitting diode OLED based on a value for matching the normalized luminance L / L ₀ derived by the predicted light emission luminance deriving unit 21 with the reference value TH _S. The coefficient C _V is set as a correction value.

The correction coefficient C _V set here is described in the correction value table 33 in a format associated with each corresponding organic light emitting diode OLED. In the present embodiment, the reference value determination unit 22 and the correction value setting unit 23 function as a setting unit that sets a correction coefficient C _V as a correction value for each organic light emitting diode OLED. Further, the correction coefficient C _V is a use start time of the image display apparatus 1 is set to 1 as an initial value, in accordance with the lapse of driving time t, the initial correction factor C _V by the correction value setting unit 23 Changed from value.

The signal correction unit 24 as a correction unit corrects the image signal corresponding to each organic light emitting diode OLED based on the correction coefficient C _V associated with each organic light emitting diode OLED in the correction value table 33. Specifically, correction is performed such that the gradation indicated by the image signal corresponding to each organic light emitting diode OLED is multiplied by the correction coefficient C _V. The corrected image signal is output to the γ conversion unit 25 as the image signal S _C.

The γ conversion unit 25 performs so-called gamma conversion on the image signal S _C output from the signal correction unit 24 to convert the image signal S _C into an output image signal S _OUT and then to the X driver of the display unit 4. Output image signal S _OUT is output.

<(1-5) Luminance unevenness suppression processing method>
<(1-5-1) Advance preparation of data>
Measurement results as shown in FIGS. 3 and 4 are obtained by measuring in advance the drive voltage and emission luminance when a reference current is passed through the organic light emitting diode OLED. Here, the curve indicating the relationship between the drive time t and the normalized luminance L / L ₀ as shown in FIG. 3 cannot be described with a simple exponential function. For this reason, a function that represents the normalized luminance L / L ₀ using the drive time t and the drive voltage V and a function that represents the relationship between the drive time t and the drive voltage V are obtained. Before the image display device 1 is shipped, the function data representing the normalized luminance L / L ₀ using the drive time t and the drive voltage V is stored in the storage unit 3 as the first function data 31 and is driven. Data of a function representing the relationship between the time t and the drive voltage V is stored in the storage unit 3 as the second function data 32. In addition, about the 1st and 2nd function data 31 and 32, it sets along the measurement result as shown in FIG. 3 and FIG. 4 about organic light emitting diode OLED of each color of red, green, and blue.

  Here, the first and second function data 31 and 32 for the red organic light emitting diode OLED will be described as an example.

For example, based on the actual measurement results shown in FIG. 3 and FIG. 4, it is assumed that the actual measurement result is expressed by a function expressed by an approximate mathematical expression. Here, when the driving voltage at the driving start time (driving time t = 0h) of the organic light emitting diode OLED is a constant V ₀ , the normalized luminance L / L ₀ is expressed by the following formula (1). It can be expressed approximately using V and drive time t. As a method for obtaining a function that approximately represents the actual measurement result from the actual measurement result, for example, using the actual measurement value, the slope of the portion where the normalized luminance L / L ₀ changes linearly and the normalized luminance L / L Various known methods for sequentially calculating the coefficient or the like of the exponential function indicating a change of ₀ may be employed.

The function expressed by the above equation (1) shows the relationship of the normalized luminance L / L ₀ with respect to the driving time t as shown in FIG. When the error between the value of the above formula (1) and the actual measurement value is calculated, the average of the errors is as extremely small as 0.000034. Here, the data indicating the function of the above equation (1) corresponds to the first function data 31. Further, the relationship between the driving voltage V and the driving time t is approximately expressed by the following expression (2) under the condition where the driving time t is longer than 1800 h, and is approximately when the driving time t is 1800 h or less. Is represented by the following formula (3). Here, the data indicating the functions of the following expressions (2) and (3) corresponds to the second function data 32.

  Here, a method for obtaining mathematical formulas represented by the above formulas (2) and (3) will be specifically described. In the actual measurement result as shown in FIG. 4, there is usually a flat portion that can be approximated using a straight line. About such a part, a mathematical formula can be calculated | required by a simple method by using well-known spreadsheet software or statistical analysis software.

  The actual measurement result shown in FIG. 4 is a flat portion that can be approximated using a straight line in the first range where the drive time t is 1800 h or less. For this reason, the driving time t is set as the variable x on the horizontal axis, the driving voltage V is set as the variable y on the vertical axis, the graph of that portion is drawn as a scatter diagram, and the regression line is obtained, thereby obtaining the following equation (4) Is calculated.

y = 2.9758 × 10 ⁻⁴ x + 5.4058 (4)

For the first range, 2.9758 × 10 ⁻⁴ that is the slope of the regression line may be obtained, and 5.4058 that is the intercept of the regression line may be obtained.

  Next, by rewriting the variable x on the horizontal axis to the drive time t and rewriting the variable y on the vertical axis to the drive voltage V, the above equation (3) is obtained. This is called a voltage function 1 (t).

  Among the actual measurement results shown in FIG. 4, in order to obtain the above equation (2) that represents the curved portion related to the second range in which the drive time t is 1800 h or more, the actual measurement result of the drive voltage V, A difference from the voltage function 1 (t) expressed by the expression (3) may be extracted and expressed by an expression. Here, a scatter diagram representing the difference {driving voltage-voltage function 1 (t)} is obtained.

  First, in order to simplify the handling of the voltage function 1 (t), the driving time t, which is an independent variable of the voltage function 1 (t), is converted into a variable u = t−1800 starting from 0 for the second range. Thus, the voltage function 1 (u) is obtained. Further, in order to simplify the handling of the voltage function 1 (t), the driving time t, which is an independent variable of the voltage function 1 (t), is set to a variable w = (t−1800) / By converting to 100, the voltage function 1 (w) is obtained.

Here, the natural logarithm log _e {(driving voltage-voltage function 1 (w)}) is obtained using the difference {driving voltage-voltage function 1 (w)} as an argument, and a regression curve thereof is obtained. ) Is calculated.

y = 2.3446 × log _e (x) −4.9491 (5)

  The regression equation of the above equation (5) represents the approximate relationship represented by the following equation (6).

log _e {drive voltage−voltage function 1 (w)} ≈2.3446 × log _e (w) −4.9491 (6)

Here, both sides of the above equation (6), the exponential function e ^x bottom is Napier number e, rewritten using a power function of w, the following equation is (7) is obtained.

{Driving voltage-Voltage function 1 (w)} ≈exp (−4.9491) × w ^2.3446 = 7.0898 × 10 ⁻³ × (w ^2.3446 ) (7)

  Hereinafter, the right side of the above equation (7) is referred to as a power function 1 (w) related to w.

  Here, the two coefficients of the above equation (7) are increased or decreased by a small amount, and the left side and the right side of the above equation (7) are adjusted with high accuracy as a whole. Specifically, if 2.3446 which is a coefficient of the power function of w is further increased, the value of the power function of w increases more rapidly as the variable w is increased. The accuracy of approximation at the right end of the curve indicating the result can be improved. However, since the value of the power function of w becomes too large with respect to the difference {drive voltage−voltage function 1 (w)} as it is, the exponential function coefficient (−4.9491) is gradually decreased. Thus, the left side and the right side of the above formula (7) are adjusted so as to match with high accuracy as a whole.

  As a result of such adjustment, the optimum value of the coefficient of the power function of w was 2.5, and the optimum value of the coefficient of the exponential function was (−5.203). By rewriting the above equation (7) using these coefficients, the following equation (8) is obtained.

{Driving voltage-Voltage function 1 (w)} ≈exp (−5.203) × w ^2.5 = 0.0055 × (w ^2.5 ) (8)

  Hereinafter, the right side of the above equation (8) is referred to as a power function 2 (w) of w.

  Here, when the variable w of the power function 2 (w) of the equation (8) is rewritten to the driving time t, the following equation (9) is obtained. This is called a voltage function 2 (t) of the driving time t.

{Driving voltage-voltage function 1 (w)} ≈0.0055 × {(t-1800) / 100} ^2.5 (9)

  When the voltage function 1 (w) is moved to the right side of the above equation (9), the following equation (10) is obtained.

Drive voltage≈Voltage function 1 (w) + 0.0055 × {(t−1800) / 100} ^2.5 (10)

  Here, when the above equation (3) representing the voltage function 1 (t) is substituted into the above equation (10), the above equation (2) is obtained.

  Next, a method for obtaining Formula (1) will be specifically described. The first range of the actual measurement results shown in FIG. 3 where the drive time t is 1800 h or less can be approximated using a function. The approximation using this function can be confirmed as follows.

First, the difference (1−normalized luminance L / L ₀ ) is determined so that the value indicated by the approximate curve increases as the driving time t increases. Next, a natural logarithm log _e (1−normalized luminance L / L ₀ ) is obtained using the difference (1−normalized luminance L / L ₀ ) as an argument. Then, the driving time t is a variable x on the horizontal axis, the natural logarithm is a variable y on the vertical axis, a graph for the first range is drawn as a scatter diagram, and a regression curve is obtained. An expression is calculated.

y = 0.65192 × log _e (x) −4.2155 (11)

  Note that the regression equation represented by the above equation (11) represents the approximate relationship represented by the following equation (12).

log _e (1−normalized luminance L / L ₀ ) ≈0.65192 × log _e (t) −4.2155 (12)

Here, both sides of the equation (12), and the exponential function e ^x bottom is Napier number e, rewritten using a power function of t, the following equation (13) is obtained.

1−Standardized luminance L / L ₀ ≈exp (−4.2155) × t ^0.65192 = 0.01476 × (t ^0.65192 ) (13)

The above equation (13) is an approximate equation for the first range. For this reason, in the vicinity of the right end of the actual measurement result shown in FIG. 3 and log _e (1−normalized luminance L / L ₀ ) ≈−0.5, another equation is used in order to further improve the accuracy of approximation. Perform the approximation used.

In the second range in which the drive time t of the actual measurement results shown in FIG. 3 is 1800 h or more, an increase in the absolute value of the slope of the drive voltage V shown in FIG. 4 and (1−normalized luminance L / It was found that the increase in the absolute value of the slope of L ₀ ) is responsive. Therefore, the approximate expression is obtained by expressing the contribution of the component corresponding to the drive voltage V by the following expression (14) using the coefficient m.

m × (V−V ₀ ) / V ₀ (14)

Here, the coefficient m is the right end of the definition area of the drive time t (near the maximum value of t in the definition area), and the value of the above equation (14) is the difference (1-normalized luminance L / L ₀ ). It is required within a range not exceeding.

Here, the inclination of the difference (1−normalized luminance L / L ₀ ) with respect to the change in the driving time t is compared with the inclination with respect to the change in the driving time t of the value represented by the above equation (14). At the left end of the definition area of the drive time t (near the minimum value of t within the definition area), the slope of the difference (1-normalized luminance L / L ₀ ) has a value represented by the above equation (14). Greater than the slope. In the time zone where the driving time t is in the vicinity of 1000 hours or more, the slope of the difference (1-normalized luminance L / L ₀ ) and the slope of the value represented by the above equation (14) are almost equal. Will be equal. At this time, a curve indicating the relationship between the drive time t and the difference (1-normalized luminance L / L ₀ ) and a curve indicating the relationship between the drive time t and the value represented by the above equation (14) are parallel. Will be in a state.

  Accordingly, considering a certain function d (t), when the drive time t increases within a range of less than 1000 hours, the value of d (t) increases so as to approach the value represented by the following equation (15). In addition, when the driving time t increases within a range of 1000 hours or more, the approximation accuracy can be improved by using a function that converges the value of d (t) to a constant value.

(1-normalized luminance L / L ₀ ) −m × (V−V ₀ ) / V ₀ (15)

  Therefore, the following expression (16) using coefficients j and k is considered as an expression representing the function d (t). The reciprocal of the coefficient k in the following equation (16) means a time constant that defines the time required for convergence of the function d (t). Here, if the reciprocal of the coefficient k is adjusted so as to correspond to about 300 hours, the above request for improving the accuracy of the approximation is satisfied.

    d (t) = j × {1-exp (−k × t)} (16)

Further, when the driving time t increases toward a positive infinity value, the function d (t) asymptotically approaches the coefficient j, so the coefficient j must be a value smaller than the maximum value of the above equation (15). There are constraints that must be met. Then, by adjusting the coefficients m, j, and k based on this constraint condition, the sum of the value of the above equation (14) and the value of the above equation (16), and the difference (1−normalized luminance L / L ₀ ) can be adjusted to be as small as possible. That is, the following expression (17) is obtained based on the above expression (14) and the above expression (16).

(1-normalized luminance L / L ₀ ) ≈m × (V−V ₀ ) / V ₀ + j × {1−exp (−k × t)} (17)

When the above equation (17) is solved for the normalized luminance L / L ₀ , the following equation (18) is obtained.

Normalized luminance L / L ₀ ≈1−m × (V−V ₀ ) / V ₀ −j × {1−exp (−k × t)} (18)

  Then, the above equation (1) is obtained by substituting the coefficients m, j, and k into the above equation (18). In this case, m = 0.658, j = 0.0856, k = 0.0035.

In this way, the first and second function data 31 and 32 are obtained for the organic light emitting diodes OLED of red, green, and blue, and are stored in the storage unit 3 before the image display device 1 is shipped. . Here, the first and second function data 31 and 32 are expressed by mathematical expressions, but it is only necessary to obtain a relationship in which only one value y corresponds to a certain value x. Accordingly, the first function data 31 representing the relationship of the normalized luminance L / L ₀ with respect to the driving time t and / or the second function data 32 representing the relationship between the driving voltage V and the driving time t are used as data such as an array. You may store in the memory | storage part 3 by the look-up table (Lookup table) system represented with a structure. As a method of expressing the first and second function data 31 and 32, as to which of the method represented by the formula and the lookup table method is selected, the load on the processor at the time of calculation according to the formula, It may be determined in consideration of the storage capacity required for the storage unit 3.

<(1-5-2) Correction method of light emission brightness when using>
In the image display device 1, as described above, the organic light-emitting diodes OLED of the respective colors deteriorate as the usage time elapses. Therefore, the correction coefficient C _V is set and updated using the first and second function data 31 and 32 in a timely manner. Thereby, the light emission luminance of the organic light emitting diode OLED is corrected, and luminance unevenness on the display screen is suppressed with high accuracy. Hereinafter, a method for correcting light emission luminance when the image display apparatus 1 is used will be described. In addition, here, it demonstrates, demonstrating the correction | amendment method of the light emission luminance about red organic light emitting diode OLED.

In certain timing such timing and the like of screen saver is displayed on the display unit 4, the control unit 2 by that the power supply circuit 5 is controlled, 30 mA / cm ² is the current density of the current density flowing through the organic light emitting diode OLED reference Set to At this time, the voltage detection unit 6 measures the drive voltage V _REAL of each pixel circuit 41.

Next, the predicted light emission luminance deriving unit 21 estimates the drive time t using the above equations (2) and (3) for an arbitrary drive voltage V _REAL measured by the voltage detection unit 6. Further, the normalized luminance L / L ₀ for each organic light emitting diode OLED is estimated by substituting the estimated driving time V _REAL and the estimated driving time t into V and t in the above equation (1). .

Here, it is assumed that the drive voltage V _REAL is measured by the voltage detector 6 for each of the nine pixel circuits 41a, 41b, 41c, 41d, 41e, 41f, 41g, 41h, and 41i when the reference current flows. . Here, the driving voltage Va for the pixel circuit 41a, the driving voltage Vb for the pixel circuit 41b, the driving voltage Vc for the pixel circuit 41c, the driving voltage Vd for the pixel circuit 41d, the driving voltage Ve for the pixel circuit 41e, and the driving voltage Vf for the pixel circuit 41f. The driving voltage Vg for the pixel circuit 41g, the driving voltage Vh for the pixel circuit 41h, and the driving voltage Vi for the pixel circuit 41i are measured.

For example, if the drive voltage Va is 5.598 V, the drive time t = 645h is estimated, and further the normalized luminance L / L ₀ = 0.9 is estimated. If the drive voltage Vb is 5.936 V, the drive time t = 17862h is estimated, and further the normalized luminance L / L ₀ = 0.85 is estimated. If the drive voltage Vc is 6.346 V, the drive time t = 2271h is estimated, and further the normalized luminance L / L ₀ = 0.80 is estimated. If the drive voltage Vd is 6.757 V, the drive time t = 2461h is estimated, and further the normalized luminance L / L ₀ = 0.75 is estimated. If the drive voltage Ve is 7.168 V, the drive time t = 2598h is estimated, and further the normalized luminance L / L ₀ = 0.70 is estimated. If the drive voltage Vf is 7.578 V, the drive time t = 2708h is estimated, and further the normalized luminance L / L ₀ = 0.65 is estimated. If the drive voltage Vg is 7.989V, the drive time t = 2802h is estimated and additionally estimated normalized luminance L / L ₀ = 0.60. When the drive voltage Vh is 8.399 V, the drive time t = 22885h is estimated, and the normalized luminance L / L ₀ = 0.55 is estimated. If the drive voltage Vi is 8.810 V, the drive time t = 2960h is estimated, and further the normalized luminance L / L ₀ = 0.50 is estimated.

Note that if the drive voltages V related to all the pixel circuits 41 are distributed in the range of the drive voltages Va to Vc, the light emission luminance is not corrected, and the maximum scale is simply applied to all the pixel circuits 41. When the tone output image signal is given, the normalized luminance L / L ₀ is distributed in the range of 0.80 to 0.90. That is, a deviation in light emission luminance of about 1.125 times (= 0.90 / 0.80) is observed between the light emission luminance of the pixel circuit 41a and the light emission luminance of the pixel circuit 41c.

Further, when the drive voltages V related to all the pixel circuits 41 are distributed in the range of the drive voltages Vd to Vf, the light emission luminance is not corrected, and the maximum scale is simply applied to all the pixel circuits 41. When the tone output image signal is given, the normalized luminance L / L ₀ is distributed in the range of 0.65 to 0.75. That is, a deviation in light emission luminance of about 1.154 times (= 0.75 / 0.65) is observed between the light emission luminance of the pixel circuit 41d and the light emission luminance of the pixel circuit 41f.

Further, when the drive voltages V related to all the pixel circuits 41 are distributed in the range of the drive voltages Vg to Vi, the light emission luminance is not corrected, and the maximum scale is simply applied to all the pixel circuits 41. When the tone output image signal is given, the normalized luminance L / L ₀ is distributed in the range of 0.50 to 0.60. That is, a deviation of the light emission luminance of about 1.2 times (= 0.60 / 0.50) is observed between the light emission luminance of the pixel circuit 41g and the light emission luminance of the pixel circuit 41i.

  With respect to the occurrence of such a deviation in light emission luminance, the image display apparatus 1 according to the present embodiment has one correction method among a plurality of light emission luminance correction methods according to the magnitude of the light emission luminance deviation. Performed selectively.

Specifically, first, the reference value determining unit 22 sets the standardized luminance (that is, the maximum value of standardized luminance) L _max corresponding to the pixel circuit 41 having the minimum driving voltage V _REAL and the maximum driving voltage V _REAL. normalized luminance corresponding to the pixel circuit 41 is (i.e., the minimum value of the normalized luminance) and L _min is obtained. Next, the reference value determining unit 22 recognizes the ratio (L _max / L _min ) between the maximum value L _max and the minimum value L _min as a deviation in light emission luminance. The next, the reference value determining unit 22 is a value of L _max / L _min judgment reference value R ₀ or less (the value of R ₀ is, for example, 1.03, etc.) whether it is determined. Then, when the relationship of L _max / L _min ≦ R ₀ is established by the reference value determination unit 22, it is recognized that the deviation of the emission luminance is slight, and the emission luminance is not corrected. On the other hand, when the relationship of L _max / L _min > R ₀ is established, one of the following first to third correction processes is performed according to the magnitude of the minimum value L _min of the normalized luminance. Correction processing is selectively executed.

Specifically, when the minimum value L _min of the normalized luminance is equal to or greater than the first threshold value S ₁ , the first correction process is executed. On the other hand, when the minimum value L _min of the normalized luminance is less than the first threshold value S ₁ and greater than or equal to the second threshold value S ₂ , the second correction process is executed. Furthermore, when the minimum value L _min of the normalized luminance is less than the second threshold value S ₂ , the third correction process is executed. The first threshold value S ₁ is, for example, 0.75, and the second threshold value S ₂ is, for example, 0.6. The first and second threshold values S ₁ and S ₂ may be appropriately set by the user according to the characteristics of the organic light emitting diode OLED, the purpose of use of the image display device 1, and the like.

<(1-5-2-1) First correction process>
When the value of the minimum value L _min of the normalized luminance is greater than or equal to the first threshold value S ₁ , since the deterioration of the organic light emitting diode OLED is slight as the entire display unit 4, the entire screen of the display unit 4 is high. A first correction process is performed with priority given to obtaining luminance. Hereinafter, specific contents of the first correction process will be described.

In the display unit 4, the organic light emitting diode OLED in which the drive voltage V _REAL is minimized when the reference current flows is the least deteriorated. Therefore, the standardized luminance value of the organic light emitting diode OLED, that is, the standardized luminance maximum value L _max is determined by the standard value determining unit 22 as the correction standard value TH _S. Then, the correction value setting unit 23, for each organic light emitting diode OLED, and a correction factor C _V which is obtained based on the value to match the normalized luminance L / L ₀ to the maximum value L _max is set as the correction value.

Here, if, for each organic light emitting diode OLED, and a setting the correction value for matching the normalized luminance L / L ₀ to the maximum value L _max simply as the correction factor C _V, the maximum value L _max of the normalized luminance And the minimum value L _min (L _max / L _min ) is the maximum value of the correction coefficient C _V. However, when the gradation (brightness level) indicated by the image signal corresponding to each pixel circuit 41 is represented by a predetermined number of bits, the emission luminance is set to the gradation indicated by the image signal corresponding to each pixel circuit 41. If the correction coefficient for correcting is simply multiplied, the gradation indicated by the image signal exceeds the upper limit. That is, the luminance level overflows. For example, when the gradation represented by the image signal is represented by 8 bits, the gradation is represented by 256 levels from 0 to 255, for example. Then, when the upper limit value 255 and a numerical value in the vicinity thereof are simply multiplied by the correction coefficient for correcting the light emission luminance, the value exceeds the upper limit value 255. If a large number of gradations exceeding 255 occur, a problem called overexposure that does not express high-brightness contrast occurs. Therefore, in order to maintain the image quality, it is necessary to avoid an overflow of the luminance level.

Therefore, the signal correction unit 24 performs a compression operation by multiplying the gradation Y indicated by the input image signal S _IN by the compression coefficient Z so that the brightness level does not overflow in the brightest pixel constituting the image. . Here, the compression coefficient Z is set to a value (L _min / L _max ) obtained by dividing the minimum value L _min of the normalized luminance by the maximum value L _max that is the correction reference value TH _S. For example, when the gradation indicated by the input image signal S _IN is represented by 8 bits, the gradation obtained by multiplying the maximum gradation 255 by the compression coefficient Z (255 × Z = 255 × L _min / L _max ) is the gradation after compression.

Note that the compression operation for multiplying the gradation indicated by the input image signal S _IN by the compression coefficient Z and the operation for multiplying the correction coefficient for correcting the light emission luminance may be performed separately. It may be an aspect that is included in the correction coefficient _CV . Here, the compression coefficient Z is included in the correction coefficient C _V , so that the gradation indicated by the input image signal S _IN is multiplied by the correction coefficient C _V , so that the compression calculation and the light emission luminance correction are performed simultaneously. Shall be. Here, if an arbitrary normalized luminance value is L _x , the correction coefficient C _V including the compression coefficient Z is calculated by the correction value setting unit 23 by calculation according to the following equation (19).

C _V = (L _max / L _x ) × (L _min / L _max ) = (L _min / L _x ) (19)

For example, when a value less than 0.80 is set as the first threshold value S ₁ and L _min = 0.80 and L _max = 0.90, the correction coefficient C for the pixel circuit 41c is set. Among _V, the numerical value (L _max / L _x ) relating to the correction of the light emission luminance is 1.125 (= 0.90 / 0.80). Under the condition that the value (gradation) obtained by multiplying the gradation of the input image signal S _{IN by} the numerical value (L _min / L _max ) related to the compression operation is 160, the signal correction unit 24 corrects the gradation. After that, the gradation of the image signal S _C is 180. Further, under the condition that the value (gradation) obtained by multiplying the gradation of the input image signal S _{IN by} the numerical value (L _min / L _max ) related to the compression operation is 200, the signal correction unit 24 corrects the gradation. After that, the gradation of the image signal S _C is 225.

For example, when L _max = 0.90, the numerical value (L _max / L _x ) relating to the correction of the light emission luminance is 1.059 (= 0.90) in the correction coefficient C _V for the pixel circuit 41b. /0.85). Under the condition that the value (gradation) obtained by multiplying the gradation of the input image signal S _{IN by} the numerical value (L _min / L _max ) related to the compression operation is 160, the signal correction unit 24 corrects the gradation. After that, the gradation of the image signal S _C is 169. Further, under the condition that the value (gradation) obtained by multiplying the gradation of the input image signal S _{IN by} the numerical value (L _min / L _max ) related to the compression operation is 200, the signal correction unit 24 corrects the gradation. gradation of the image signal S _C of the after becomes 212.

  As described above, in the first correction process executed when the degree of deterioration of the organic light emitting diode OLED is small, the light emission luminance is corrected in accordance with the organic light emitting diode OLED having the smallest degree of deterioration. As a result, it is possible to compensate for a decrease in light emission luminance caused by the organic light emitting diode OLED, and luminance unevenness on the display screen is suppressed. And the fall of the brightness by degradation of organic light emitting diode OLED is eliminated, and the improvement in picture quality is aimed at. In other words, luminance compensation is realized in which specific gravity is placed on improving image quality.

<(1-5-2-2) Second correction process>
When the minimum value L _min of the normalized luminance is less than the first threshold value S ₁ and greater than or equal to the second threshold value S ₂ , the organic light emitting diode OLED is moderately deteriorated as a whole of the display unit 4. For this reason, the second correction process is performed in order to achieve both a certain level of brightness on the display screen and an extension of the lifetime of the display unit 4. Hereinafter, specific contents of the second correction process will be described.

First, the reference value determining unit 22 calculates a geometric average value (√ (L _max × L _min )) of the maximum value L _max of the normalized luminance and the minimum value L _min of the normalized luminance, and this geometric average value (√ (L _max × L _min )) is determined as the correction reference value TH _S. Then, a correction coefficient C _V obtained by the correction value setting unit 23 based on a value for making the normalized luminance L / L ₀ coincide with the geometric mean value (√ (L _max × L _min )) for each organic light emitting diode OLED. Set as a correction value.

Here, for each organic light emitting diode OLED, a value for correcting the light emission luminance for making the normalized luminance L / L ₀ coincide with the geometric mean value (√ (L _max × L _min )) is simply a correction coefficient C. _{Assuming V} , the ratio (√ (L _max × L _min ) / L _min ) between the geometric mean value (√ (L _max × L _min )) and the minimum value L _min is the maximum value of the correction coefficient C _V. However, as described above, when the gradation (luminance level) indicated by the image signal corresponding to each pixel circuit 41 is represented by a predetermined number of bits, the level indicated by the image signal corresponding to each pixel circuit 41 is shown. If the correction coefficient for correcting the light emission luminance is simply multiplied, the gradation indicated by the image signal exceeds the upper limit value, resulting in an overflow of the luminance level. Therefore, in the second correction process, it is necessary to avoid the luminance level overflow in order to maintain the image quality.

Therefore, the brightest pixels constituting the image so as not to cause the luminance level of the overflow, the signal correction section 24, with respect to gradation Y indicated by the input image signal S _IN, the compression operation is performed by multiplying the compression factor Z . Here, the compression coefficient Z is a value (L _min / √ (L _min ) obtained by dividing the minimum value L _min of the normalized luminance by the geometric mean value (√ (L _max × L _min )) that is the correction reference value TH _{S. max} × L _min )). For example, when the gradation indicated by the input image signal S _IN is represented by 8 bits, the gradation obtained by multiplying the maximum gradation 255 by the compression coefficient Z (255 × Z = 255 × L _min / √ (L _max × L _min )) is the gradation after compression.

Note that the compression operation for multiplying the gradation indicated by the input image signal S _IN by the compression coefficient Z and the operation for multiplying the correction coefficient for correcting the light emission luminance may be performed separately. It may be an aspect that is included in the correction coefficient _CV . Here, the compression coefficient Z is included in the correction coefficient C _V , so that the gradation indicated by the input image signal S _IN is multiplied by the correction coefficient C _V , so that the compression calculation and the light emission luminance correction are performed simultaneously. Shall be. Here, if an arbitrary normalized luminance value is L _x , the correction coefficient C _V including the compression coefficient Z is calculated by the correction value setting unit 23 by calculation according to the following equation (20).

C _V = (√ (L _max × L _min ) / L _x ) × (L _min / √ (L _max × L _min ))
= (L _min / L _x ) (20)

For example, when a value exceeding 0.65 is set as the first threshold S ₁ and a value less than 0.65 is set as the second threshold S ₂ , L _min = 0.65, L _max = In the case of 0.75, the geometric average value (√ (L _max × L _min )) is 0.6982. Then, in the pixel circuit 41d, the numerical values according to the compression operation on the gradation of the input image signal _{S IN (L min / √ (} L max × L min)) obtained by multiplying by calculated values (gradation) is 160 Under such conditions, the gradation of the image signal S _C after being corrected by the signal correction unit 24 is 149 (≈160 × 0.6982 / 0.75). Further, in the pixel circuit 41e, the numerical values according to the compression operation on the gradation of the input image signal _{S IN (L min / √ (} L max × L min)) obtained by multiplying by calculated values (gradation) is 160 in such conditions, the gradation of the image signal S _C after being corrected by the signal correcting unit 24 is 160 (≒ 160 × 0.6982 / 0.70 ). Further, in the pixel circuit 41f, the numerical values according to the compression operation on the gradation of the input image signal _{S IN (L min / √ (} L max × L min)) obtained by multiplying by calculated values (gradation) is 160 Under such conditions, the gradation of the image signal S _C after being corrected by the signal correction unit 24 is 172 (≈160 × 0.6982 / 0.65).

In addition, in the reference value determination unit 22, the correction value setting unit 23, and the signal correction unit 24, when the calculation of the square root according to the geometric mean value (√ (L _max × L _min )) is performed, the calculation accuracy decreases. Instead of the geometric mean value (√ (L _max × L _min )), the arithmetic average value ((L _max + L _min ) / 2 of the maximum value L _max of the standardized luminance and the minimum value L _min of the standardized luminance ) May be used. However, as shown in the above equation (20), when the correction coefficient C _V is set in consideration of the compression coefficient Z, the calculation of the square root becomes unnecessary, so the geometric mean value and the arithmetic mean value No matter which of these is used, there is virtually no difference.

  As described above, in the second correction process executed when the deterioration of the organic light emitting diode OLED is moderate, the light emission luminance is corrected in accordance with the organic light emitting diode OLED having a moderate deterioration degree. As a result, it is possible to compensate for a decrease in light emission luminance caused by the organic light emitting diode OLED, and luminance unevenness on the display screen is suppressed.

<(1-5-2-3) Third correction process>
If the value of the minimum value L _min of the normalized luminance is smaller than the second threshold value S _2, as a whole of the display unit 4, because it is the degradation of the organic light emitting diode OLED is severe, reducing the luminance as a whole screen Thus, the third correction process is performed with priority given to extending the life of the display unit 4. Hereinafter, specific contents of the third correction process will be described.

In the display unit 4, the degree of deterioration of the organic light emitting diode OLED that maximizes the drive voltage V _REAL when the reference current flows is the largest. Therefore, the standardized luminance value of the organic light emitting diode OLED, that is, the standardized luminance minimum value L _min is determined by the standard value determining unit 22 as the correction standard value TH _S. Then, for each organic light emitting diode OLED, a correction coefficient C _V obtained based on a value for making the normalized luminance L / L ₀ coincide with the minimum value L _min of the normalized luminance is set as the correction value by the correction value setting unit 23. Is set.

Here, for each organic light emitting diode OLED, assuming that a value for correcting the light emission luminance so as to make the normalized luminance L / L ₀ coincide with the minimum value L _min of the normalized luminance is simply the correction coefficient C _V , the correction is performed. The maximum value of the coefficient C _V is 1. Therefore, the problem of luminance level overflow does not occur. For this reason, a compression operation is unnecessary in the third correction process. Accordingly, the correction value setting unit 23 sets a correction coefficient C _V that matches the normalized luminance L / L ₀ with the minimum value L _min of the normalized luminance as a correction value for each organic light emitting diode OLED. Specifically, when an arbitrary normalized luminance value is L _x , the correction coefficient C _V is calculated by the correction value setting unit 23 by calculation according to the following equation (21).

C _V = (L _min / L _x ) (21)

For example, in the case where a value exceeding 0.50 is set as the second threshold value S ₂ , when L _min = 0.50, the correction coefficient C _V is 0.8333 (= L _min / L _x = 0.50 / 0.60). If the gradation of the input image signal S _IN is 160, the gradation of the image signal S _C corrected by the signal correction unit 24 is 133. For the pixel circuit 41h, the correction coefficient C _V is 0.9090 (= L _min / L _x = 0.50 / 0.55). If the gradation of the input image signal S _IN is 200, the gradation of the image signal S _C after being corrected by the signal correction unit 24 is 182.

  As described above, in the third correction process executed when the degree of deterioration of the organic light emitting diode OLED is large, the light emission luminance is corrected in accordance with the organic light emitting diode OLED having the greatest degree of deterioration. Thereby, the brightness nonuniformity in the display screen can be accurately suppressed while suppressing the progress of the deterioration in the organic light emitting diode OLED. That is, when the degree of deterioration of the organic light emitting diode OLED is large, the emission luminance is compensated in consideration of suppression of the progress of the deterioration. Therefore, the life of the image display device 1 is extended and the luminance unevenness on the display screen is reduced. It is possible to achieve both suppression.

<(1-6) Correction coefficient setting operation flow>
11 to 15 are flowcharts showing a correction coefficient setting operation flow in the image display apparatus 1. This operation flow is controlled by the control unit 2 and executed at a specific timing such as a timing when a screen saver is displayed on the display unit 4.

In step S1 of FIG. 11, the drive voltage of the organic light emitting diode OLED is set by feedback control or the like so that the current flowing through the organic light emitting diode OLED of each pixel circuit 41 matches the reference current under the control of the control unit 2. The drive voltage V _REAL of each organic light emitting diode OLED in this state is detected by the voltage detector 6.

In step S <b _> 2, the predicted light emission luminance deriving unit 21 estimates the drive time t for each organic light emitting diode OLED based on the drive voltage V _REAL and the second function data 32. Here, the drive time t for each organic light-emitting diode OLED is estimated by an operation in which the drive voltage V _REAL is substituted for V in the above equations (2) and (3).

In step S3, the predicted emission luminance deriving unit 21 estimates the normalized luminance L / L ₀ when the reference current flows for each organic light emitting diode OLED. Here, the first function data 31 is used to calculate each organic voltage by calculating the drive voltage V _REAL and the drive time t estimated in step S2 into V and t in the above equation (1). normalized luminance L / L ₀ of light-emitting diode OLED is estimated.

In step S4, the ratio (L _max / L _min ) between the maximum value L _max and the minimum value L _min of the normalized luminance L / L ₀ estimated in step S3 is calculated by the reference value determining unit 22 as the deviation of the emission luminance. Is calculated as

In step S5, the reference value determination unit 22, the value of L _max / L _min is equal to or less than the determination reference value R ₀ is determined. Here, when the relationship of L _max / L _min ≦ R ₀ is established, it is recognized that the deviation of the light emission luminance is slight, and there is no need for correction of the light emission luminance, so this operation flow is ended. The On the other hand, if the relationship of L _max / L _min ≦ R ₀ is not established, it is recognized that the deviation of the light emission luminance is more than a certain level, and the light emission luminance needs to be corrected. move on.

In step S11, the reference value determination unit 22, the minimum value L _min of the normalized luminance is determined whether or not the first threshold value S ₁ or more. Here, if the minimum value L _min of the normalized luminance is the first threshold value S ₁ or more, the first correction processing line shown proceeds to step S12, the reference value determining unit 22 and the correction value setting unit 23 in FIG. 13 Is called. On the other hand, if the minimum value L _min of the normalized luminance is not the first threshold value S ₁ or more, the process proceeds to step S13.

In step S13, the reference value determination unit 22 determines whether or not the minimum value L _min of the normalized luminance is less than the first threshold value S ₁ and greater than or equal to the second threshold value S ₂ . Here, if the minimum value L _min of the normalized luminance is less than the first threshold value S ₁ and greater than or equal to the second threshold value S ₂ , the process proceeds to step S 14, and the reference value determination unit 22 and the correction value setting unit 23 perform FIG. The second correction process indicated by is performed. On the other hand, if the minimum value L _min of the normalized luminance is less than the first threshold value S ₁ and not greater than or equal to the second threshold value S ₂ , the process proceeds to step S15. In the case where the process proceeds to step S15, the minimum value L _min of the normalized luminance becomes the case of the second below the threshold S _2.

  In step S15, the reference value determination unit 22 and the correction value setting unit 23 perform the third correction process shown in FIG.

In step S121 of FIG. 13, the reference value determination unit 22 determines the reference value TH _S. Here, the maximum value L _max of the normalized luminance estimated in step S3 is determined as the reference value TH _S.

In step S122, the correction value setting unit 23 specifies a target for setting the correction coefficient C _V , that is, the pixel circuit 41 to be corrected. When step S122 is performed for the first time, the pixel circuit 41 having the reference address is designated. In step S122, every time the process returns from step S124, the pixel circuit 41 of the next address is sequentially specified.

At step S123, the correction value setting unit 23, for each organic light emitting diode OLED, and a correction factor C _V is set. Here, as shown in the above equation (19), for each organic light emitting diode OLED, a coefficient (L _max / L _x ) and compression that make the normalized luminance L _x coincide with the maximum value L _max of the normalized luminance A correction coefficient C _V obtained by multiplying the calculation coefficient Z (L _min / L _max ) is set.

In step S124, the correction value setting unit 23 determines whether or not the correction coefficient C _V has been set for all the pixel circuits 41. If the correction coefficient C _V is not set for all the pixel circuits 41, the process returns to step S122, and the processes of steps S122 to S124 are repeated until the correction coefficient C _V is set for all the pixel circuits 41. . When the correction coefficient C _V is set for all the pixel circuits 41, the operation flow is finished.

In step S141 of FIG. 14, the reference value determination unit 22, the reference value TH _S is determined. Here, the geometric average value (√ (L _max × L _min )) of the maximum value L _max and the minimum value L _min of the normalized luminance estimated in step S3 is determined as the reference value TH _S.

In step S142, the correction value setting unit 23 specifies the target for setting the correction coefficient C _V , that is, the pixel circuit 41 to be corrected. When step S142 is the first time, the pixel circuit 41 having the reference address is designated. In step S142, every time the process returns from step S144, the pixel circuit 41 of the next address is sequentially specified.

In step S143, the correction value setting unit 23 sets a correction coefficient C _V for each organic light emitting diode OLED. Here, as shown by the above equation (20), for each organic light emitting diode OLED, a coefficient that makes the normalized luminance L _x coincide with the geometric average value (√ (L _max × L _min )) of the normalized luminance. A correction coefficient C _V obtained by multiplying (√ (L _max × L _min ) / L _x ) by a compression calculation coefficient Z (L _min / √ (L _max × L _min )) is set.

In step S144, the correction value setting unit 23 determines whether or not the correction coefficient C _V has been set for all the pixel circuits 41. If the correction coefficient C _V is not set for all the pixel circuits 41, the process returns to step S142, and the processes of steps S142 to S144 are repeated until the correction coefficient C _V is set for all the pixel circuits 41. . When the correction coefficient C _V is set for all the pixel circuits 41, the operation flow is finished.

In step S151 in FIG. 15, the reference value determination unit 22 determines the reference value TH _S. Here, the minimum value L _{min of the} normalized luminance estimated in step S3 is determined as the reference value TH _S.

In step S152, the correction value setting unit 23 specifies a target for setting the correction coefficient C _V , that is, the pixel circuit 41 to be corrected. When step S152 is the first time, the pixel circuit 41 having the reference address is designated. In step S152, every time the process returns from step S154, the pixel circuit 41 of the next address is sequentially specified.

In step S153, the correction value setting unit 23 sets a correction coefficient C _V for each organic light emitting diode OLED. Here, as shown in the above equation (21), for each organic light emitting diode OLED, a coefficient (L _min / L _x ) that makes the normalized luminance L _x coincide with the minimum value L _min of the normalized luminance is corrected. Set as coefficient _CV .

In step S154, the correction value setting unit 23 determines whether or not the correction coefficient C _V has been set for all the pixel circuits 41. Here, if the correction coefficient C _V is not set for all the pixel circuits 41, the process returns to step S152, and the processes of steps S152 to S154 are repeated until the correction coefficient C _V is set for all the pixel circuits 41. . When the correction coefficient C _V is set for all the pixel circuits 41, the operation flow is finished.

As described above, in the image display device 1 according to the first embodiment, the drive voltage V applied to both ends of the organic light emitting diode OLED obtained from the actual measurement result when the reference current flows and the standardization of the organic light emitting diode OLED. First and second function data 31 and 32 indicating the relationship with the luminance L / L ₀ are stored in the storage unit 3 in advance. Thereafter, the specific timing of use of the image display apparatus 1, the driving voltage V _REAL reference current to each organic light emitting diode OLED is applied to the respective organic light emitting diode OLED when a flow is detected. Then, a correction coefficient C _V for each organic light emitting diode OLED is set based on the drive voltage V _REAL and the first and second function data 31 and 32 according to the state of deterioration. As a result, it is possible to easily and accurately compensate for a decrease in light emission luminance caused by deterioration of the light emitting element. Accordingly, it is possible to easily and accurately suppress luminance unevenness on the display screen with a simple configuration that does not include a special configuration such as a luminance meter.

Further, the drive time t of each organic light emitting diode OLED is estimated based on the drive voltage V _REAL and the second function data 32. For this reason, a special configuration such as a counter for measuring the driving time of each organic light emitting diode OLED, a gradation integrating unit, and the like is unnecessary.

In the first to third correction processes, the reference value TH _S is determined based on at least one of the maximum value L _max and the minimum value L _min of the normalized luminance. Then, the correction coefficient C _V is set based on a value for matching the normalized luminance L _x estimated for each organic light emitting diode OLED with the reference value TH _S. That is, the reference value TH _S is set as a unified reference for all the pixel circuits 41, and the correction coefficient C _V is set for all the pixel circuits 41 in accordance with the unified reference. By such setting of the correction coefficient _CV , luminance unevenness on the display screen is accurately suppressed.

Further, the operation of setting the correction coefficient _CV is executed at a specific timing such as the timing when the screen saver is displayed on the display unit 4. For this reason, when the user visually recognizes the image being displayed on the display unit 4, there is no problem that the reference current flows to each organic light emitting diode OLED in order to set the correction coefficient _CV . Therefore, the user cannot visually recognize the image, and the luminance unevenness on the display screen is accurately suppressed.

<(2) Second Embodiment>
In the image display device 1 according to the first embodiment, the relationship between the drive voltage V and the drive time t when a reference current is passed through the organic light emitting diode OLED is a function as expressed by the above equations (2) and (3). An example that can be approximated with high accuracy has been described. However, depending on the configuration of the organic light emitting diode OLED, the relationship between the driving voltage V and the driving time t when a reference current is passed through the organic light emitting diode OLED may not be approximated with high accuracy by a function. Even when such an organic light emitting diode OLED is adopted, the image display device 1A according to the second embodiment can easily suppress the luminance unevenness on the display screen with a simple configuration. It is configured.

  Note that, in the image display device 1A according to the second embodiment, the display unit 4 is changed to the display unit 4A and the control unit 2 is realized as compared with the image display device 1 according to the first embodiment. The control unit 2A has a different function. Specifically, for the display unit 4A according to the second embodiment, the pixel circuit 41 is changed to a pixel circuit 41A in which the configuration of the organic light emitting diode OLED is different from that of the display unit 4 according to the first embodiment. It has been made. The control unit 2A according to the second embodiment is changed to a predicted light emission luminance deriving unit 21A in which the predicted light emission luminance deriving unit 21 performs a different calculation process compared to the control unit 2 according to the first embodiment, A gradation integration unit 26A is added. In addition, the storage unit 3 according to the second embodiment differs from the storage unit 3 according to the first embodiment in the stored data content. Specifically, the storage unit 3 according to the second embodiment stores gradation reference integrated data 34A and third function data 35A instead of the first and second function data 31 and 32, and the gradation. Integration data 36A is further stored.

  As described above, the image display device 1A according to the second embodiment corresponds to a configuration obtained by changing a part of the configuration of the image display device 1 according to the first embodiment. For this reason, in the configuration of the image display apparatus 1A according to the second embodiment, the same portions as those of the image display apparatus 1 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted. Hereinafter, differences of the image display device 1A according to the second embodiment from the image display device 1 according to the first embodiment will be described.

<(2-1) Aspect of deterioration of light emitting element>
As a specific example of the pixel circuit 41A according to the second embodiment, a deterioration mode of the organic light emitting diode OLED that emits red light will be described.

  Here, among the configurations of the organic light emitting diode OLED that emits red light, a configuration different from the organic light emitting diode OLED according to the first embodiment will be described. Here, the hole transport layer is a vapor deposition layer having a thickness of 54 nm, the light emitting layer is a co-deposition film having a thickness of 25 nm, and the concentration of the dopant material in the light emitting layer is 2.0%. The In addition, the electron transport layer is a deposited layer having a thickness of 45 nm, and the second electrode layer is a co-deposited layer made of magnesium and silver having a thickness of 25 nm. The organic protective layer is a vapor deposition layer made of an aromatic amine derivative having a thickness of 70 nm. Further, an inorganic protective layer made of silicon nitride and having a thickness of 1.0 μm is formed on the organic protective layer by CVD.

In addition, about the conditions which observe the aspect of deterioration of organic light emitting diode OLED, the method similar to 1st Embodiment is employ | adopted. The organic light emitting diode OLED was connected to a constant current driving circuit, and a constant current of 3.6 mA was set to flow so that the current density flowing through the organic light emitting diode OLED was 10 mA / cm ² . The light emission luminance (initial light emission luminance) L ₀ when the organic light emitting diode OLED started to emit light (at the start of driving) was 1012 cd / m ² , but after 2838 hours from the start of light emission, the light emission luminance was the initial light emission luminance. It was reduced to a value of about 89.1% of L _0. Regarding the temperature around the organic light emitting diode OLED at the time of measurement, as a result of automatic measurement, the average temperature during the measurement period was 24.0 ° C, the minimum temperature was 23.5 ° C, and the maximum temperature was 26.0 ° C. It was. And the temperature of the 1st quartile located between the lowest temperature and the highest temperature was 24.0 degreeC, and the temperature of the 3rd quartile was 24.0 degreeC. For this reason, the measured values of more than half of the temperature in the measurement period are included in the range of the first quartile and the third quartile. become.

Based on the measurement results under such measurement conditions, a value (L / L ₀ ) obtained by dividing the emission luminance L at each time point by the initial emission luminance L ₀ was calculated as the normalized luminance. The relationship between the elapsed time (drive time) t from the start of light emission and the normalized luminance L / L ₀ is as shown in FIG. Further, the relationship between the drive time t and the drive voltage V is as shown in FIG. As shown in FIG. 16, the normalized luminance L / L ₀ fluctuated in small increments with the lapse of the driving time t. In addition, as shown in FIG. 17, the driving voltage V fluctuated violently as the driving time t passed.

<(2-2) Configuration related to luminance unevenness suppression processing>
As shown in FIG. 18, unlike the control unit 2 according to the first embodiment, the control unit 2A has a predicted emission luminance deriving unit 21A and a gradation integration unit as a functional configuration related to the luminance unevenness suppressing process. 26A. Further, unlike the first embodiment, the storage unit 3 stores the gradation reference integrated data 34A, the third function data 35A, and the gradation integrated data 36A as data related to the luminance unevenness suppressing process.

The gradation reference integrated data 34A is a value obtained by integrating luminance data (reference gradation) serving as a reference of an image signal corresponding to the organic light emitting diode OLED according to a light emission mode serving as a reference of the organic light emitting diode OLED. (Reference integrated value) _Contains data indicating _IST . Here, the light emission mode that is a reference of the organic light emitting diode OLED is light emission at the reference time (here, 1 hour), and the reference gradation is integrated for the number of times of light emission at the reference time (here, 1 hour). in the reference accumulated value I _ST is obtained. For example, 60 frames per second are displayed on the image display apparatus 1A, the gradation indicated by the input image signal is represented by 8 bits, and the gradation is indicated in 256 levels from 0 to 255, and the reference gradation is 255. If it is assumed, the reference integrated value I _ST is obtained by the following equation (22).

I _ST = 3600 × 60 × 255 = 550800000 (22)

The third function data 35A is data of a function that approximately shows the relationship between the drive time t and the normalized luminance L / L ₀ as shown in FIG. That is, in the present embodiment, the third function data 35A includes the driving voltage V applied to both ends of the organic light emitting diode OLED when the reference current flows through the organic light emitting diode OLED, and the driving time t of the organic light emitting diode OLED. And the reference relationship data indicating the relationship between the value and the value related to the emission luminance of the organic light emitting diode OLED (in this case, the normalized luminance L / L ₀ ).

The gradation accumulated data 36A is a value (gradation actual accumulated value) I obtained by integrating the gradation indicated by the image signal S _C output from the signal correction unit 24 according to the light emission mode of the organic light emitting diode OLED. Data indicating _LT is stored for each pixel circuit 41A. Here, the light emission mode of the organic light emitting diode OLED is light emission at an arbitrary time, and the gradation indicated by the image signal S _C output from the signal correction unit 24 is integrated by the number of times of light emission of the organic light emitting diode OLED. Thus, the gradation actual integrated value I _LT is obtained.

The gradation integrating unit 26A as an integrating unit integrates the gradation indicated by the image signal S _C output from the signal correcting unit 24 for each organic light emitting diode OLED according to the light emission mode of the organic light emitting diode OLED. Then, the gradation actual integrated value I _LT is derived. Here, the gradation indicated by the image signal S _C output from the signal correction unit 24 is integrated by the number of times the organic light emitting diode OLED emits light (the number of times of light emission) according to the gradation, thereby obtaining the actual gradation. An integrated value I _LT is derived. The gradation actual integrated value I _LT derived here is stored for each organic light emitting diode OLED in the storage unit 3.

The predicted light emission luminance deriving unit 21A is based on the third function data 35A, the gradation actual integrated value I _LT , the reference integrated value I _ST, and the drive voltage V _REAL when the reference current flows through the organic light emitting diode OLED. Then, a value (here, normalized luminance L / L ₀ ) related to the predicted light emission luminance in each organic light emitting diode OLED is derived.

<(2-3) Luminance unevenness suppression processing method>
<(2-3-1) Data preparation>
Measurement results as shown in FIGS. 16 and 17 are obtained by measuring in advance the drive voltage and emission luminance when a reference current is passed through the organic light emitting diode OLED. Here, the curve indicating the relationship between the drive time t and the normalized luminance L / L ₀ as shown in FIG. 16 cannot be approximately expressed by a function having only the drive time t as a variable. Therefore, a function that represents the normalized luminance L / L ₀ using the drive time t and the drive voltage V is obtained. Then, before shipping the image display device 1A, function data representing the normalized luminance L / L ₀ using the drive time t and the drive voltage V is stored in the storage unit 3 as the third function data 35A.

For example, based on the actual measurement results shown in FIGS. 16 and 17, it is assumed that the actual measurement results are expressed by a function expressed by an approximate mathematical expression. Here, assuming that the driving voltage at the driving start time (driving time t = 0h) of the organic light emitting diode OLED is a constant V ₀ , the normalized luminance L / L ₀ is the driving voltage as shown by the following equation (23). It can be expressed using V and drive time t. As a method for obtaining a function that approximately indicates the actual measurement result from the actual measurement result, for example, using the actual measurement value, the slope of the portion where the normalized luminance L / L ₀ changes linearly and the normalized luminance L / L Various known methods for sequentially calculating the coefficient of the exponential function indicating a change of ₀ may be employed. The following equation (23) can be obtained in the same manner as the procedure for obtaining the above equation (1).

The function expressed by the above equation (23) shows the relationship of the normalized luminance L / L ₀ with respect to the driving time t as shown in FIG. When the error between the value of the above equation (23) and the actual measurement value is calculated, the average of the errors is as extremely small as −0.00098. Here, the data indicating the function of the above equation (23) corresponds to the third function data 35A.

On the other hand, the relationship between the drive voltage V and the drive time t shown in FIG. 17 shows such a fluctuation that the drive voltage V undulates with the lapse of the drive time t. For this reason, it is difficult to represent the drive voltage V approximately accurately with a function having the drive time t as a variable. For this reason, for the purpose of estimating the drive time t using the gradation actual integrated value I _LT , the reference integrated value I _ST is calculated in advance and stored in the storage unit 3 as the gradation reference integrated data 34A. .

<(2-3-2) Driving time estimation method>
Here, the description will be made assuming that the gradation of the image signal is represented by 256 levels of 0 to 255. First, when the organic light emitting diode OLED is driven with the gradation of the image signal set to the maximum value of 255, a reference current flows through the organic light emitting diode OLED, and the organic light emitting diode OLED emits light. It is assumed that an actual measurement value indicated by 17 is obtained.

Here, for example, it is assumed that the organic light emitting diode OLED emits light for one hour based on the image signal S _C having an average gradation value of 127. At this time, the product (60 × 3600 × 127 = 274432000) of the average value 127 of the gradation and the number of times of light emission (60 × 3600) is the actual gradation integrated value I _LT . Then, as indicated by the above equation (22), the reference integrated value I _ST for one hour is 55800000. Therefore, the value obtained by dividing the actual gradation integrated value I _LT by the reference integrated value I _ST (0.49804≈27432000 / 550800000) is the light emission time converted when the organic light emitting diode OLED emits light according to the maximum gradation 255. Equivalent to. Therefore, in the present embodiment, by dividing the reference integrated value I _ST gradation actual integrated value I _LT, drive time t emitted by the reference current flows in the organic light emitting diode OLED is estimated.

For example, it is assumed that the organic light emitting diode OLED emits light for 1000 hours based on the image signal S _C having an average gradation value of 64. At this time, the product (60 × 3600 × 1000 × 64 = 138400000) of the average value 64 of the gradation and the number of times of light emission (60 × 3600 × 1000) is the actual gradation integrated value I _LT . Then, a value obtained by dividing the gradation actual integrated value I _LT by the reference integrated value I _ST (250.980≈1384200000 / 550800000) is calculated as the drive time t.

Here, the gradation of the image signal S _C output from the signal correction unit 24 has been described as an average value, but in reality, the gradation value is integrated for each organic light emitting diode OLED, so that the gradation value is integrated. The actual integrated value I _LT may be calculated.

<(2-3-3) Luminance correction method when using>
In the image display device 1A, as described above, the organic light-emitting diodes OLED of the respective colors deteriorate as the usage time elapses. Therefore, setting and updating of the correction coefficient C _V using the gradation reference integration data 34A, the third function data 35A, and the gradation integration data 36A are performed in a timely manner. Thereby, the light emission luminance of the organic light emitting diode OLED is corrected, and luminance unevenness on the display screen is suppressed with high accuracy. Hereinafter, a method for correcting light emission luminance when the image display apparatus 1A is used will be described. In addition, here, it demonstrates, demonstrating the correction | amendment method of the light emission luminance about red organic light emitting diode OLED.

The gradation integrating unit 26A sequentially integrates the gradations of the image signal S _C output from the signal correcting unit 24 to calculate the actual gradation integrated value I _LT . This gradation actual integrated value I _LT is stored for each organic light emitting diode OLED in the gradation integrated data 36 A of the storage unit 3. That is, the actual gradation integrated value I _{LT for} each organic light emitting diode OLED included in the gradation integrated data 36A is updated each time one frame of the input image signal S _IN is input.

In parallel with this, at a specific timing such as when the screen saver is displayed on the display unit 4A, the power supply circuit 5 is controlled by the control unit 2A, so that the current density flowing through the organic light emitting diode OLED becomes the reference current density. Is set to 10 mA / cm ² . Then, the voltage detection unit 6 measures the drive voltage V _REAL of each pixel circuit 41A. At this time, in the predicted light emission luminance deriving unit 21A, the grayscale actual integrated value _ILT is divided by the reference integrated value _IST , whereby the driving time t of the organic light emitting diode OLED is estimated. Then, in the predicted light emission luminance deriving unit 21A, the drive voltage V _REAL and the estimated drive time t are respectively substituted for V and t in the above equation (23), thereby normalizing each organic light emitting diode OLED. Luminance L / L ₀ is estimated. Since the subsequent processing is the same as that of the first embodiment, description thereof is omitted here.

<(2-4) Correction coefficient setting operation flow>
FIG. 20 is a flowchart showing a correction coefficient setting operation flow in the image display apparatus 1A. This operation flow is controlled by the control unit 2A, and is executed at a specific timing such as a timing when a screen saver is displayed on the display unit 4.

In step S21 of FIG. 20, as in step S1 of FIG. 11, each pixel circuit 41A is set in a state where the reference current is flowing in the organic light emitting diode OLED, under the control of the control unit 2A. The drive voltage V _REAL of the diode OLED is detected by the voltage detector 6.

In step S22, the estimated light emission luminance deriving unit 21A refers to the gradation reference integrated data 34A and the gradation integrated data 36A, so that the reference integrated value I _ST and the gradation actual integrated value of each organic light emitting diode OLED are obtained. _ILT is recognized.

In step S23, the predicted light emission luminance deriving unit 21A divides the gradation actual integrated value I _LT by the reference integrated value I _ST to estimate the drive time t of each organic light emitting diode OLED.

In step S24, the predicted light emission luminance deriving unit 21A uses the third function data 35A, the drive voltage V _REAL detected in step S21, and the drive time t estimated in step S23 for each organic light emitting diode OLED. Thus, the normalized luminance L / L ₀ when the reference current is flowing is estimated. Here, the third function data 35A is used, and the drive voltage V _REAL detected in step S21 and the drive time t estimated in step S23 are substituted into V and t in the above equation (23). By such calculation, the normalized luminance L / L ₀ for each organic light emitting diode OLED is estimated.

In step S25, as in step S4 of FIG. 11, the ratio (L _max / L) between the maximum value L _max and the minimum value L _min of the normalized luminance L / L ₀ estimated in step S24 by the reference value determination unit 22. L _min ) is calculated as the deviation of the light emission luminance.

In step S26, as in step S5 of FIG. 11, the reference value determination unit 22 determines whether or not the value of L _max / L _min is equal to or less than the determination reference value R ₀ . Here, when the relationship of L _max / L _min ≦ R ₀ is established, it is recognized that the deviation of the light emission luminance is slight, and there is no need for correction of the light emission luminance, so this operation flow is ended. The On the other hand, if the relationship of L _max / L _min ≦ R ₀ is not established, it is recognized that the deviation of the light emission luminance is more than a certain level, and the light emission luminance needs to be corrected. move on.

  Note that the operation after step S11 in FIG. 12 is the same as the operation of the first embodiment described above, and thus the description thereof is omitted here.

As described above, in the image display device 1A according to the second embodiment, the reference integrated value I _ST obtained by integrating the reference gradation for the number of times of light emission in the reference time (here, 1 hour) is prepared. . Thereafter, when the image display device 1A is used, the gradation indicated by the image signal S _C output from the signal correction unit 24 is sequentially integrated for each organic light emitting diode OLED to calculate the actual gradation integrated value I _LT. Is done. In parallel with this calculation, the drive voltage V _REAL related to each organic light emitting diode OLED when the reference current flows is detected at a specific timing, and the gradation actual integrated value I _LT is divided by the reference integrated value I _ST . Thus, the driving time t of each organic light emitting diode OLED is estimated. Based on the third function data 35A prepared in advance, the detected drive voltage V _REAL, and the estimated drive time t, the normalized luminance L / L ₀ related to each organic light emitting diode OLED is estimated. A correction coefficient C _V corresponding to the normalized luminance L / L ₀ is set for each organic light emitting diode OLED. With such a configuration, even when the decrease in light emission luminance due to the deterioration of the organic light emitting diode OLED proceeds in an unstable manner so as to wave with the passage of time, the luminance unevenness on the display screen is more accurately suppressed. can do.

<(3) Modification>
It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the first and second embodiments, the correction of the light emission luminance is performed by comparing the value of L _max / L _min as an index indicating the deviation of the light emission luminance with the determination reference value R _0. Whether or not it is determined is not limited to this. For example, a value of L _max −L _min is adopted as an index indicating the deviation in light emission luminance, and the value of L _max −L _min is compared with a determination reference value R ₀ (for example, R ₀ = 0.03). Thus, it may be determined whether or not to correct the light emission luminance.

In the first and second embodiments, the correction coefficient C _V is set at the timing when the screen saver is displayed. However, the present invention is not limited to this. For example, the correction coefficient C _V may be set at a specific timing such as every time the accumulated light emission time of the organic light emitting diode OLED reaches a certain time (for example, 20 hours). Further, the correction coefficient C _V may be set at the timing when the absence of the user is detected using a human sensor or the like. Further, the correction coefficient C _V may be set at a timing when the screen saver is first displayed after the accumulated light emission time of the organic light emitting diode OLED reaches a certain time. In any of these configurations, image quality can be improved and maintained.

In the first and second embodiments, the first and second threshold values S ₁ and S ₂ used as a reference for selectively executing the first to third correction processes are 0.7 and 0, respectively. .6, but is not limited to this. For example, the values of the first and second threshold values S ₁ and S ₂ may be set in accordance with points where the degree of change in the normalized luminance L / L ₀ with respect to the elapse of the driving time t changes greatly.

In the first and second embodiments, in the first to third correction processes, the normalized luminance L / L ₀ derived by the predicted emission luminance deriving units 21 and 21A is set to a value that matches the reference value TH _S. The correction coefficient C _V is set based on a value that allows the normalized luminance L / L ₀ to fall within a predetermined range (for example, a range within ± 1.5%) centered on the reference value TH _S. The case where the correction coefficient C _V is set based on this is also included. That is, the correction coefficient C _V may be set for each organic light emitting diode OLED so that the difference between the maximum value L _max and the minimum value L _min of the normalized luminance L / L _{0 is} reduced.

  In the first and second embodiments, the organic light emitting diode OLED is set in a state in which the reference current flows by causing the power supply circuit 5 to function as a constant current drive circuit. However, the present invention is not limited to this. For example, the drive voltage is gradually changed while detecting the drive voltage applied to both ends of the organic light emitting diode OLED and the current flowing through the resistor R1, and the drive when the current flowing through the resistor R1 matches the reference current. The voltage may be detected.

  In the second embodiment, the duty ratio indicating the ratio of the light emitting period of the organic light emitting diode OLED occupying the period (frame period) from the start of display of one frame to the start of display of the next one frame is constant. However, the present invention is not limited to this. For example, a mode in which the duty ratio is changed according to the temperature change of the display unit 4A is also conceivable. Specifically, when the temperature of the display unit 4A is in the standard temperature range, the duty ratio is set to 127/255 which is a standard value. Further, the duty ratio is reduced from the standard value under the condition that the light emission luminance of the organic light emitting diode OLED is increased with the temperature rise of the display unit 4A. On the other hand, the duty ratio is increased from the standard value under the condition that the light emission luminance of the organic light emitting diode OLED is decreased with the temperature decrease of the display unit 4A. By controlling the duty ratio, the brightness of the image displayed on the display unit 4A is in accordance with the input image signal.

However, if the control of such a duty ratio is performed, in the calculation of the reference integrated value I _ST and tone the actual accumulated value I _LT described above, it is necessary to reflect the effect caused by increasing or decreasing the duty ratio. For example, when the duty ratio is set to 127/255 which is a standard value, the reference integrated value I _ST is calculated by the following equation (24). This reference integrated value I _ST corresponds to the integrated value of gradation when the drive time t is 1 hour.

I _ST = 127/255 × 3600 × 60 × 255 = 27432000 (24)

Here, for example, a case is assumed in which the organic light emitting diode OLED emits light for 1000 hours based on the image signal S _C having an average gradation value of 127. At this time, if the duty ratio is 170/255 on average, the product (170/255 *) of the average value (170/255) of the duty ratio, the average value 127 of the gradation, and the number of times of light emission (60 × 3600 × 1000). 60 × 3600 × 1000 × 127 = 1828288000000) is the gray scale actual integrated value I _LT . Then, a value obtained by dividing the gradation actual integrated value I _LT by the reference integrated value I _ST (666.667≈18288000000000 / 274432000) is calculated as the drive time t.

In the second embodiment, the actual gradation integrated value I _LT calculated by integrating the gradation of the image signal S _C output from the signal correction unit 24 is divided by the reference integrated value I _ST . Thus, the driving time t of the organic light emitting diode OLED has been estimated, but is not limited thereto. For example, the drive time t may be estimated by counting the number of times the organic light emitting diode OLED emits light. For example, when the organic light emitting diode OLED emits light, a method of integrating the number of pulses (frame pulses) corresponding to the vertical synchronization signal using a counter is conceivable. Specifically, when the gradation of the image signal S _C output from the signal correction unit 24 is a value equal to or higher than a predetermined threshold, the number of frame pulses is counted, and the frame period and the duty ratio are added to the counted number. By appropriately multiplying, the drive time t is estimated. For example, by setting the predetermined threshold value to a gradation value of 50% or more of the maximum gradation, the time during which the organic light emitting diode OLED emits light according to the image signal of the intermediate gradation or higher is obtained.

  In the first and second embodiments, the first to third correction processes are selectively performed according to the degree of deterioration, but the present invention is not limited to this. For example, any one of the first to third correction processes may be performed regardless of the degree of deterioration.

In the first and second embodiments, the normalized luminance L / L ₀ is adopted as the value related to the light emission luminance and the predicted light emission luminance of the organic light emitting diode OLED, but is not limited thereto. For example, the light emission luminance L is not divided by the initial light emission luminance L ₀ and normalized, and the light emission luminance L is used as it is and various calculations are performed, so that the correction coefficient C _V is set. good.

◎ In the first and second embodiment, in the pixel circuit 41, 41A, from the side of a high potential side during light emission, the first transistor T _DR and the organic light emitting diode OLED, arranged in this order, It is not limited to this. For example, the organic light emitting diode OLED and the first transistor _TDR may be arranged in this order from the higher potential side during light emission.

  In the first and second embodiments, in the plurality of pixel circuits 41, the organic light emitting diode OLED that emits red light, the organic light emitting diode OLED that emits green light, and the organic light emitting diode OLED that emits blue light. However, it is not limited to this. For example, a combination of an organic light emitting diode OLED that emits white light and a color filter that transmits light of a predetermined color may be employed for all the pixel circuits 41. As a first example of such a combination, it is conceivable to provide three color filters that transmit red, green, and blue light. As a second example, there are provided four types of red, green, blue, and white light, and three types of color filters that transmit red, green, and blue light, and four types of parts that transmit all light. It is conceivable to form an image with color pixels. Among the embodiments using the organic light emitting diode OLED that emits white light in this way, in the modified example of the first embodiment, the first and second function data 31 and 32 stored in the storage unit 3 are represented by red, green. For the blue organic light-emitting diodes OLED, instead of setting along the actual measurement results as shown in FIGS. 3 and 4, only the function data for the white organic light-emitting diodes OLED need be stored. A simple configuration can be obtained. Further, in the modified example of the second embodiment, instead of storing the third function data 35A corresponding to each color, it is only necessary to store function data for the white organic light emitting diode OLED, so that the configuration is simplified. be able to. In addition, it is not necessary to create multiple types of organic light emitting diodes OLED that emit light of different colors using manufacturing means that require extremely high accuracy, such as vapor deposition masks, which simplifies the manufacturing process and reduces costs. There are advantages you can do.

  In the first and second embodiments, the organic light emitting diode OLED is employed as the light emitting element. However, the present invention is not limited to this. For example, a light emitting element composed of an inorganic material may be employed.

  It should be noted that a part of the configurations constituting the first and second embodiments and the modified examples may be appropriately combined within a consistent range.

DESCRIPTION OF SYMBOLS 1,1A Image display apparatus 2,2A Control part 3 Memory | storage part 4,4A Display part 5 Power supply circuit 6 Voltage detection part 21,21A Predicted light emission luminance deriving part 22 Reference value determination part 23 Correction value setting part 24 Signal correction part 26A Floor Adjustment integration unit 31 First function data 32 Second function data 33 Correction value table 34A Gradation reference integration data 35A Third function data 36A Gradation integration data 41, 41A Pixel circuit OLED Organic light emitting diode R1 Resistance

Claims (10)

A plurality of light emitting elements;
A storage unit that stores relationship data indicating a relationship between a voltage applied to both ends of the light emitting element and a value related to light emission luminance of the light emitting element;
A detection unit for detecting a voltage applied to both ends of the light emitting element when a reference current flows through the light emitting element;
A derivation unit for deriving a value related to the predicted light emission luminance of each of the light emitting elements based on the relationship data and the voltage detected by the detection unit;
A setting unit that sets a correction value for each of the light emitting elements so that a difference between a maximum value and a minimum value among the values related to the predicted light emission luminances derived by the deriving unit is reduced;
A correction unit that corrects an image signal corresponding to each light emitting element based on the correction value set for each light emitting element by the setting unit;
An image display device comprising: The image display device according to claim 1,
The setting unit
A reference value is determined based on at least one of a maximum value and a minimum value of the value related to the predicted light emission luminance, and the value related to the predicted light emission luminance is matched with the reference value for each of the light emitting elements. An image display device that sets the correction value based on a value. The image display device according to claim 2,
The reference value is
An image display device having the maximum value. The image display device according to claim 2 or 3, wherein
The setting unit
An image display device, wherein the maximum value is determined as the reference value when the minimum value is equal to or greater than a first threshold value. The image display device according to claim 2,
The reference value is
An image display device having the minimum value. The image display device according to claim 2 or 5, wherein
The setting unit
When the minimum value is less than a second threshold value, the minimum value is determined as the reference value. The image display device according to any one of claims 1 to 6,
An integration unit that integrates the gradation indicated by the image signal output from the correction unit according to the light emission mode of the light emitting element;
The relationship data is
Including reference relationship data indicating a relationship between a voltage applied to both ends of the light emitting element when a reference current flows through the light emitting element, a light emission time of the light emitting element, and a value related to light emission luminance of the light emitting element;
The storage unit
Stores data indicating a reference integrated value obtained by integrating reference gradations according to a light emission mode serving as a reference of the light emitting element,
The derivation unit is
Based on the reference relationship data, the integrated value calculated by the integrating unit, the reference integrated value, and the voltage detected by the detecting unit, a value related to the predicted light emission luminance of each light emitting element is derived. An image display device characterized by that. The image display device according to any one of claims 1 to 7,
The setting unit
An image display device, wherein the correction value is set at a specific timing. The image display device according to claim 8,
The specific timing is
An image display device comprising a timing at which a screen saver is displayed. The image display device according to claim 8,
The setting unit
The image display device, wherein the correction value is set every time the accumulated light emission time of the light emitting element reaches a certain time.

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