JP2008175958A - Display apparatus, and display driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a satisfactory video display as against the deterioration of the light emission brightness of an organic EL element complying with the temperature and brightness of a display device using organic EL element. <P>SOLUTION: The brightness reduction control to forcibly lower a brightness level is performed for a prescribed time (for example, 2 hours) from a display driving start (F100 to F107). The brightness reduction control is ended upon lapse of the prescribed period and an adjustment value is calculated based on the brightness information and the temperature control, and a contrast adjustment to adjust the brightness level of a video signal, a white balance adjustment, and a brightness adjustment control as an image persistence prevention adjustment are continuously performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device having a display unit in which pixels using organic electroluminescence elements (hereinafter referred to as organic EL elements) as light emitters are arranged, and a display driving method thereof.

JP 2003-323152 A JP 2003-157050 A

Conventionally, display devices (displays) using self-luminous elements such as light-emitting diodes (LEDs), laser diodes (LD), and organic light-emitting elements have been developed.
In this type of display device, generally, a plurality of self-luminous elements are arranged in a matrix to form a screen portion (display panel), and each element is selectively made to emit light according to a video signal, thereby displaying a video. Done.
For example, these display devices are used in television receivers, computer monitor displays, portable information terminals, and the like, and with the development of information systems, the importance of display devices as user interfaces is increasing. In particular, there is a demand for a display that is easy on the eyes, easy to see on a high-definition screen, and has a high resolution and a high-speed response that allows a moving image to be clearly and clearly displayed without delay.

A display device using a self-luminous element does not require a backlight such as a liquid crystal display (LCD), and thus can be reduced in thickness and weight, and is also advantageous in terms of power consumption.
In particular, an organic EL display using an organic EL element using an organic compound as a light emitting material has a wide viewing angle, high contrast, and excellent visibility. In addition, it can be driven by a DC low voltage, has a high response speed, is resistant to vibration, and has a wide operating temperature range, and has attracted attention as a next-generation display element.

  The organic EL element has, for example, a structure in which a first electrode, an organic layer including a light emitting layer, and a second electrode are sequentially stacked on a driving substrate. In such an organic EL element, the light generated in the light emitting layer may be extracted from the driving substrate side depending on the type of display, but may be extracted from the second electrode side.

In the organic EL element, there is a problem of deterioration over time such that each organic layer is deteriorated due to heat generated by light emission, light emission luminance is lowered, and light emission itself becomes unstable.
In addition, the organic EL element exhibits a light emitting diode characteristic, and the current flowing through the device increases proportionally as the temperature rises. As a result, the light emission luminance and the deterioration are in a proportional relationship. Therefore, the light emission drive promotes the deterioration. It will also be. That is, temperature and luminance are factors that promote luminance degradation.

  As a countermeasure, Patent Document 1 describes a technique for solving luminance degradation due to temperature rise by suppressing the amount of flowing current using the proportional relationship between the amount of current and light emission luminance. There is a problem that the luminance of light emission is lowered to suppress current and a good display may not be provided.

Similarly, Patent Document 2 discloses a method for controlling display luminance in accordance with a change in ambient temperature. In this method, the data wiring is supplied at a constant current, and the driving voltage supplied to the scanning wiring is adjusted. Then, a temperature detecting means is installed in the vicinity of the display screen, and the voltage level supplied to the scanning wiring is controlled according to the change in the ambient temperature.
However, in this method, since it is necessary to install the temperature detection means, there is a limitation to secure an extra installation location, and it is necessary to suppress the display area and widen the peripheral frame.
In addition, in the center of the display area and the like, it is very difficult to secure a space for installing the temperature detection means, and it is unlikely that a high-resolution display device can be realized.
In addition, since there is no means for monitoring luminance control only by voltage control, it is difficult to provide a smooth gradation display as a correction result.

  In view of the above, an object of the present invention is to realize effective video display by performing effective display driving with respect to deterioration of light emission luminance of an organic EL element in a display device using the organic EL element.

A display device according to the present invention includes a display unit configured to display a video by driving each of the pixels based on an input video signal based on an array of pixels using an organic electroluminescence element as a light emitting element. A level adjusting unit for adjusting the luminance level of the video signal supplied to the display unit, and the luminance level of the video signal supplied to the display unit in a predetermined period from the start of display driving of the display unit The level adjustment unit includes a control calculation unit that performs luminance reduction control for gradually reducing the luminance level of the video signal.
The control calculation unit performs control for uniformly reducing the luminance level of the video signal for all the pixels of the display unit as the luminance reduction control.
The control calculation unit controls the luminance level of the video signal so that the luminance level of the video signal is reduced by 10% from the display driving start point when the predetermined period has elapsed as the luminance reduction control.
In addition, as the luminance reduction control, the control calculation unit is configured so that the luminance level of the video signal is decreased by a predetermined ratio from the display driving start time at the elapse of the predetermined period for each emission color of the pixels of the display unit. Control.
In addition, the time when the predetermined period has elapsed since the start of display driving is assumed to be the time when about 2 hours have elapsed since the start of display driving.

In addition, a luminance information detection unit that detects information on the light emission luminance of each pixel, and a temperature information detection unit that detects information on the temperature of each pixel. The control calculation unit ends the luminance reduction control after a predetermined period has elapsed from the start of the display driving, and uses the information from the luminance information detection unit and the information from the temperature information detection unit to adjust the adjustment value. And the luminance adjustment control for causing the level adjusting unit to execute the luminance level adjustment based on the adjustment value.
Further, the control calculation unit calculates a contrast adjustment value using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and determines the level based on the contrast adjustment value. The adjustment unit is caused to execute brightness level adjustment.
Further, the control calculation unit calculates a white balance adjustment value using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and based on the white balance adjustment value, The level adjustment unit is caused to execute brightness level adjustment.
The control calculation unit calculates an adjustment value for image sticking prevention using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and is based on the adjustment value for image sticking prevention. Thus, the level adjusting unit is caused to execute luminance level adjustment.

The luminance information detection unit includes a first memory unit that stores luminance information of each pixel of the video signal supplied to the display unit, a light receiving sensor that detects a light emission amount of each pixel of the display unit, and the light receiving unit. A second memory unit that stores the light amount of each pixel obtained by the sensor as luminance information of each pixel is provided. The control calculation unit detects the emission luminance change information of the pixel using the luminance information stored in the first memory unit and the luminance information stored in the second memory unit, and the emission luminance change The adjustment value is calculated using the information and the temperature information detected by the temperature detection unit.
The light receiving sensor detects the amount of light leaked from each pixel, and the second memory unit stores the amount of light leaked from each pixel obtained by the light receiving sensor as luminance information of each pixel. To do. In this case, the control calculation unit uses a value obtained by performing coefficient calculation on the luminance information stored in the first memory unit and the luminance information stored in the second memory unit, Light emission luminance change information is detected.
The light receiving sensor is disposed in a region between the light emitting elements of adjacent pixels when viewed in the plane direction of the display surface.
The temperature information detecting unit detects a temperature information of each pixel of the display unit, and stores a temperature of each pixel obtained by the temperature sensor as temperature information of each pixel. And a memory unit. The control calculation unit detects temperature change information of the pixel using the temperature information stored in the third memory unit, and uses the detected temperature change information and the emission luminance change information to adjust the adjustment value. Is calculated.
The temperature sensor is disposed on the substrate opposite to the light extraction direction of the light emitting element of each pixel.

  The display driving method of the present invention includes a display unit configured to display a video by driving each of the pixels based on an input video signal based on a plurality of pixels using an organic electroluminescence element as a light emitting element. This is a display driving method of the display device. Then, in a predetermined period from the start of display driving of the display unit, the step of gradually reducing the luminance level of the video signal supplied to the display unit, and after the predetermined period has elapsed from the start of display driving, Calculating an adjustment value using the luminance information of the pixel and the temperature information of the pixel of the display unit, and adjusting the luminance level of the video signal supplied to the display unit based on the adjustment value.

That is, in the present invention, first, luminance reduction control for forcibly reducing the luminance level is performed for a predetermined period (for example, 2 hours) from the start of display driving.
Then, when the predetermined period has elapsed, the luminance reduction control is terminated, the adjustment value is calculated based on the luminance information and the temperature information, and the luminance adjustment control for adjusting the luminance level of the video signal is performed.
In the organic EL element, at the initial stage from the start of driving, the deterioration of the light emission luminance proceeds very unstable, and after about 2 hours, for example, the luminance change stably proceeds. Therefore, in the present invention, first, the luminance deterioration is forcibly advanced at an initial stage where it proceeds in an unstable manner. Then, after the luminance is forcibly degraded to a predetermined ratio, luminance adjustment control using luminance information and temperature information is continuously performed during a period in which the luminance change stably proceeds.

According to the present invention, a pseudo-stable luminance change on the display screen is achieved by forcibly reducing the luminance during a period in which the normal light emission luminance deterioration is very unstable as an initial period from the start of driving. To advance. In the period in which the subsequent deterioration of luminance progresses, contrast adjustment and white balance are performed by feedback control using luminance information and temperature information from the state where the luminance is reduced to, for example, a predetermined ratio by the above-mentioned forced luminance reduction. By performing the adjustment, the adjustment operation is stabilized. In particular, in an organic EL element, luminance deterioration proceeds according to temperature conditions and luminance conditions. Therefore, a favorable screen display can be realized by performing stable adjustment according to these conditions.
In the luminance information detection unit, the light receiving sensor is arranged in a region between the light emitting elements of adjacent pixels when viewed in the plane direction of the display surface so as to detect leakage light of each pixel, and temperature information detection The temperature sensor is arranged on the substrate opposite to the light extraction direction of the light emitting element of each pixel. Thereby, luminance information and temperature information about each pixel can be obtained, and it is not necessary to prepare an extra area for installing the light receiving sensor and the temperature sensor in the display area, and the display area can be used effectively. it can.

Hereinafter, embodiments of the present invention will be described in the following order.
[1. Example of display panel configuration using organic EL element]
[2. Pixel structure]
[3. Example of configuration of display device]
[4. Initial forced brightness reduction processing]
[5. Contrast adjustment process]
[6. White balance adjustment process]
[7. Burn-in prevention and white balance adjustment processing]

[1. Example of display panel configuration using organic EL element]

First, a configuration example of a display panel using an organic EL element that can be employed in the display device of this embodiment will be described with reference to FIGS.
As shown in FIG. 1, the display panel includes a pixel array unit 20 in which pixels (pixel circuits) 10 are arranged in a matrix of m rows × n columns, a horizontal selector 11, a drive scanner 12, a write scanner 13, and a first AZ scanner. 14. A second AZ scanner 15 is provided.
Further, signal lines DTL1, DTL2,..., Which are selected by the horizontal selector 11 and supply video signals corresponding to luminance information as input signals to the pixels 10, are arranged in the column direction with respect to the pixel array unit 20. The signal lines DTL1, DTL2,... Are arranged by the number of columns of the pixels 10 arranged in a matrix in the pixel array unit 20.
Further, the scanning lines WSL1, WSL2,..., The scanning lines DSL1, DSL2,..., The scanning lines AZL1-1, AZL1-2, and the scanning lines AZL2-1, AZL2 in the row direction with respect to the pixel array unit 20. -2 ... are arranged. Each of these scanning lines is arranged by the number of rows of the pixels 10 arranged in a matrix in the pixel array unit 20.
The scanning lines WSL (WSL1, WSL2,...) Are selectively driven by the write scanner 13.
The scanning lines DSL (DSL1, DSL2,...) Are selectively driven by the drive scanner 12.
The scanning lines AZL1 (AZL1-1, AZL1-2,...) Are selectively driven by the first AZ scanner 14.
The scanning lines AZL2 (AZL2-1, AZL2-2,...) Are selectively driven by the second AZ scanner 15.
The drive scanner 12, the write scanner 13, the first AZ scanner 14, and the second AZ scanner 15 give a selection pulse to each scanning line at a predetermined timing set based on the input start pulse sp and clock ck, respectively.

FIG. 2 shows a configuration example of the pixel 10. In FIG. 2, only one pixel circuit 10 arranged at a portion where the signal line DTL and the scanning lines WSL, DSL, AZL1, and AZL2 intersect is shown for simplification.
The pixel 10 includes an organic EL element 1 that is a light emitting element, one holding capacitor C1, a sampling transistor T1, a drive transistor T5, a switching transistor T3, a first detection transistor T4, and a second detection transistor T2. It is composed of five n-channel thin film transistors.

The storage capacitor C1 has one terminal connected to the source of the drive transistor T5 and the other terminal connected to the gate of the drive transistor T5. In the figure, the source node of the drive transistor T5 is shown as a node Nd1, and the gate node of the drive transistor T5 is shown as a node Nd2. Therefore, the storage capacitor C1 is connected between the node Nd1 and the node Nd2.
The light emitting element of the pixel 10 is, for example, the organic EL element 1 having a diode structure, and includes an anode and a cathode. The anode of the organic EL element 1 is connected to the source (node Nd1) of the drive transistor T5, and the cathode is connected to a predetermined cathode potential Vcat.

The source of the first detection transistor T4 is connected to the first fixed potential Vss, the drain is connected to the source (node Nd1) of the drive transistor T5, and the gate is connected to the scanning line AZL1.
The second detection transistor T2 has a source connected to the second fixed potential Vofs, a drain connected to the gate (node Nd2) of the drive transistor T5, and a gate connected to the scanning line AZL2.
The sampling transistor T1 has one end connected to the signal line DTL, the other end connected to the gate (node Nd2) of the drive transistor T5, and the gate connected to the scanning line WSL.
The switching transistor T3 has a drain connected to the power supply potential Vcc, a source connected to the drain of the drive transistor T5, and a gate connected to the scanning line DSL.

The sampling transistor T1 operates when selected by the scanning line WSL, samples the input signal Vsig from the signal line DTL, and holds it in the holding capacitor C1 via the node Nd2.
The drive transistor T5 drives the organic EL element 1 by current according to the signal potential held in the holding capacitor C1.
The switching transistor T3 becomes conductive when selected by the scanning line DSL, and supplies current from the power supply potential Vcc to the drive transistor T5.
The first and second detection transistors T4 and T2 are made conductive by being selected at a predetermined timing by the scanning lines AZL1 and AZL2, respectively. The first and second detection transistors T4 and T2 are turned on / off by detecting the threshold voltage Vth of the drive transistor T5 prior to current driving of the organic EL element 1, and detecting the threshold voltage Vth in advance. It is executed in association with an operation (threshold detection operation) for holding the threshold voltage in the holding capacitor C1.

As a condition for guaranteeing the normal operation of the pixel 10, the fixed potential Vss is set lower than a level obtained by subtracting the threshold voltage Vth of the drive transistor T5 from the fixed potential Vofs. That is, Vss <Vofs−Vth.
The fixed potential Vss is set smaller than the sum of the threshold voltage Vel of the organic EL element 1 and the cathode potential Vcat (Vss <Vthel + Vcat).
The fixed potential Vofs is set smaller than the sum of the threshold voltage Vth of the drive transistor T5, the threshold voltage Vthel of the organic EL element 1, and the cathode voltage Vcat (Vofs <Vth + Vthel + Vcat).
For example, the fixed potential Vofs is a ground potential, and the fixed potential Vss is a negative potential so as to satisfy the above conditions.

[2. Pixel structure]

In this example, in each of the pixels 10 configured as described above, a light receiving sensor that detects the light emission luminance of each pixel 10 and a temperature sensor that detects the temperature of each pixel 10 are arranged.
3 and 4 show the layer structure of the pixel 10 in a state in which the driving configuration (the transistors T1 to T5, the capacitor C1, and various scanning lines and interlayer wirings in FIG. 2) is omitted.
As shown in FIGS. 3 and 4, the layer structure of the pixel 10 includes a support substrate 35, an anode 34, a light emitting element 33, a cathode 32, a light transparent substrate 31, and a counter support substrate 30.

FIG. 3 shows a structure in the case of a top emission method in which display light is extracted from the counter support substrate 30 side.
As the support substrate 35, a transparent substrate such as quartz glass, a silicon substrate, or the like is appropriately selected and used. The support substrate 35 can be applied to both the active matrix system and the passive matrix system.
On the support substrate 35, a light emitting element 33 as an organic EL layer is provided so as to be sandwiched between the anode 34 and the cathode 32. The anode 34, the light emitting element 33, and the cathode 32 constitute the organic EL element 1 shown in FIG.
The light emitting element 33 emits light in each color of red (R), green (G), and blue (B). As shown in FIG. 1, the pixel 10 having the light emitting element 33 includes a display panel. Arranged above.
A light transparent substrate 31 is formed on the organic EL element 1 including the anode 34, the light emitting element 33, and the cathode 32, and the counter support substrate 30 is further formed thereon.

  In the case of FIG. 3, the display light ML from the light emitting element 33 is extracted from the direction indicated by the arrow. That is, the display light from the light emitting element 33 is taken out through the cathode 32, the light transparent substrate 31, and the counter support substrate 30. That is, the counter support substrate 30 side is the front side of the display panel. For this reason, the cathode 32, the light transparent substrate 31, and the counter support substrate 30 are made of a light transmitting material.

Here, a light receiving sensor 36 is stacked on the counter support substrate 30 at positions opposite to various scanning lines wired on the support substrate 35. The light receiving sensor 36 is a high sensitivity light receiving sensor such as an amorphous silicon semiconductor and may be any one that can generate an electric signal in accordance with the amount of light received.
The light receiving sensor 36 receives the leakage light ML of the light emitted from the light emitting element 33 as indicated by the broken line arrow, and generates an electrical signal corresponding to the amount of incident light. That is, the light receiving sensor 36 is disposed in a region between the light emitting elements 33 of the adjacent pixels 10 when viewed in the plane direction of the display surface.
By being arranged at the position where the leakage light ML is detected in this way, the light receiving sensor 36 is prevented from blocking the display light ML, and the light emission amount of each pixel 10 can be detected.

  On the other hand, a temperature sensor 37 is disposed in a region corresponding to the light emitting element 33 on the support substrate 35 side. That is, the temperature sensor 37 is disposed on the substrate (in this case, the support substrate 35) opposite to the light extraction direction of the light emitting element 33 of each pixel 10. Each temperature sensor 37 generates an electrical signal corresponding to the temperature of the pixel 10.

FIG. 4 shows a structure in the case of a bottom emission method in which display light is extracted from the support substrate 35 side.
Also in this case, the light-emitting element 33 as an organic EL layer is provided on the support substrate 35 so as to be sandwiched between the anode 34 and the cathode 32, and the light transparent substrate 31 and the counter support substrate 30 are formed. is there.
However, in this case, the display light ML from the light emitting element 33 is extracted through the anode 34 and the support substrate 35 as indicated by arrows. That is, the support substrate 35 side is the front side of the display panel. For this reason, a light transmissive material is used for the anode 34 and the support substrate 35. In this case, the cathode 32 and the counter support substrate 30 do not need to be light transmissive materials.

  In this case, the light receiving sensor 36 is laminated on the same layer as the anode 34. The light receiving sensor 36 extracts an electrical signal corresponding to the amount of the leaked light SL. Also in this case, the light receiving sensor 36 is arranged in a region between the light emitting elements 33 of the adjacent pixels 10 when viewed in the plane direction of the display surface. In this manner, the light receiving sensor 36 is not shielded from the display light ML by being arranged at the position where the leaked light ML is detected, and the light emission amount of each pixel 10 can be detected.

  Further, a temperature sensor 37 is disposed in a region corresponding to the light emitting element 33 on the counter support substrate 30 side. That is, also in this case, the temperature sensor 37 is disposed on the substrate (in this case, the opposing support substrate 30) opposite to the light extraction direction of the light emitting element 33 of each pixel 10. Each temperature sensor 37 generates an electrical signal corresponding to the temperature of the pixel 10.

For example, by adopting the structure as shown in FIG. 3 or 4, the light receiving sensor 36 and the temperature sensor 37 can be arranged corresponding to each pixel 10, and they do not block the display light ML. Furthermore, if the light receiving sensor 36 and the temperature sensor 37 are arranged in this way, it is not necessary to prepare an extra area for installing the light receiving sensor 36 and the temperature sensor 37 in the display area, and the display area can be used effectively. Can do.
In addition, regarding the monitoring of the light amount of the leaked light SL by the light receiving sensor 36, other light scattering leakage light amount is monitored by providing a limit for detecting only the light leak amount of 20% or less of the original light emission intensity. To prevent.

FIG. 5 schematically shows the arrangement relationship between the pixels and the light receiving sensor 36 in the screen plane direction. 5 shows a part of the pixels 10 arranged in a matrix as shown in FIG. 1, for example, a configuration in which pixels of the same color are arranged in the scan direction (wiring direction of the signal line DTL in FIG. 1). It is said. That is, a row of R pixels as pixels 10R-1, 10R-2, 10R-3,... A row of G pixels as pixels 10G-1, 10G-2, 10G-3,. B pixel columns as 10B-2, 10B-3,... Are formed. Such a pixel row of each color is sequentially formed over the entire screen.
As shown by being surrounded by a broken line, one color pixel CG is formed by the adjacent R pixel, G pixel, and B pixel.

As shown in the figure, the light receiving sensor 36 is formed at a position between pixels of the same emission color. As described above, the light receiving sensor 36 detects the leakage light SL of the light emitting element of each pixel 10, but one light receiving sensor 36 receives the leakage light SL of the pixels 10 on both sides thereof.
For example, when attention is paid to the light receiving sensor 36A disposed between the pixel 10R-2 and the pixel 10R-3, the light receiving sensor 36A includes both the pixel 10R-2 and the pixel 10R-3 as indicated by broken lines. Leaked light SL is incident.
For example, when the light receiving sensor 36A is provided for the pixel 10R-2, information on the light emission luminance of the pixel 10R-2 can be obtained as follows.

First, each pixel 10 emits light with a luminance corresponding to the signal supplied by the signal DTL. The signal value for each pixel 10 is a known value, and can be extracted from, for example, the horizontal selector 11 in FIG. it can. Therefore, an electrical signal corresponding to the amount of light detected by the light receiving sensor 36 can be extracted as information on the light emission luminance of one pixel by calculating using the signal value for the adjacent pixel.
For example, when the signal value supplied to the pixel 10R-2 is “a”, the signal value supplied to the pixel 10R-3 is “b”, and the electrical signal value obtained by the light receiving sensor 36A is “c”,
c × (a / (a + b))
As a result of this calculation, information on the light emission luminance of the pixel 10R-2 can be obtained.

[3. Example of configuration of display device]

A configuration example of a main part of the display device of the embodiment is shown in FIG.
The display device of this example includes a panel module 40, a level adjustment unit 42, a memory unit 43, A / D converters 44 and 45, memory units 46 and 47, and a control calculation unit 50.

The panel module 40 includes the display panel having the configuration described with reference to FIGS. 1 to 5 and performs video display based on an input video signal.
The level adjustment unit 42 performs luminance level adjustment on the input video signal from the video input unit 41 according to the control of the control calculation unit 50. For example, the luminance level corresponding to a predetermined pixel is increased or decreased, or the luminance level is uniformly increased or decreased for all pixels.

The memory unit 43 stores video signals supplied to the panel module 40 via the level adjustment unit 42, that is, the luminance levels of all the pixels constituting the screen. The input video signal is temporarily stored in the memory unit 43 and then read out and supplied to the panel module 40.
This memory unit 43 has a storage area for several frames of the video signal, and stores the luminance levels for all the pixels of each frame from the current frame to several frames in the past.
As a process of the control calculation unit 50 to be described later, the amount of change in light emission luminance is detected. At that time, luminance information detected by the light receiving sensor 36 and luminance information in the luminance signal value when the luminance information is obtained. A comparison is made. That is, the luminance level in the input video signal is compared with the actually detected luminance level. For this purpose, when the luminance information obtained by the light receiving sensor 36 is read into the control calculation unit 50, the comparison is made. The luminance information of the input video signal must be retained. For this reason, the luminance level of several frame periods from the present is stored in the memory unit 43 in consideration of the time difference from the supply timing of the input video signal to the panel module 40 to the timing of the comparison process. The actual number of frame periods that can be stored may be set according to the time difference from the video signal input to the emission luminance change amount detection processing.

The A / D converter 44 converts the electrical signal obtained by each light receiving sensor 36 provided for each pixel 10 into a digital data value as described above.
The luminance information of each pixel 10 converted into digital data by the A / D converter 44 is stored in the memory unit 46. For example, the memory unit 46 stores luminance information of each pixel 10 for one frame. The luminance information stored in the memory unit 46 is read by the control calculation unit 50 and is used for the detection process of the emission luminance change amount described later.
As described above, the light receiving sensor 36 outputs an electrical signal corresponding to the light amount of the leaked light SL for each pixel 10, but the output of the light receiving sensor 36 itself includes a leaked light component from an adjacent pixel. . Therefore, the calculation for canceling the leaked light component from the adjacent pixel described in FIG. 5 is performed, and the electric signal value as the calculation result may be converted into digital data by the A / D converter 44.

The A / D converter 45 converts the temperature information signal obtained by each temperature sensor 37 provided for each pixel 10 as described above into a digital data value.
The temperature information of each pixel 10 converted into digital data by the A / D converter 45 is stored in the memory unit 46. For example, the memory unit 46 stores temperature information of each pixel 10 for two frames. The luminance information stored in the memory unit 46 is read by the control calculation unit 50 and used for a temperature change amount detection process described later. The reason why the temperature information of each pixel for two frames is stored is to determine a temporal temperature change. Therefore, the temperature information of each pixel 10 may be stored not only in two frames but also in a period of three frames or more.

The control calculation unit 50 can be formed by, for example, a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), or a DSP (Digital Signal Processor).
The control calculation unit 50 performs a process for realizing an initial forced luminance reduction function, a contrast adjustment function, a white balance adjustment function, and a burn-in prevention adjustment function as a predetermined calculation process and a luminance level adjustment control process for the level adjustment unit 42. .

The initial forced luminance reduction function is a level adjusting unit 42 so that the luminance level of the video signal supplied to the panel module 40 decreases in a predetermined period (for example, 2 hours) after the display driving of the panel module 40 is started. This is a function for performing luminance reduction control for gradually reducing the luminance level of the video signal.
For example, as the luminance reduction control, the control calculation unit 50 uniformly reduces the luminance level of the video signal for all the pixels of the panel module 40 during the initial two hours. For example, the luminance level of the video signal is the initial two hours. Is controlled so that it is 10% lower than the display driving start time.
Alternatively, the control calculation unit 50 controls the luminance level of the video signal so that the luminance level of the video signal is reduced by a predetermined ratio from the display driving start time at the time when the initial two hours have elapsed for each light emission color of the panel module 40 as luminance reduction control. To do.

The contrast adjustment function is one of execution functions of brightness adjustment control that is executed after the brightness reduction control is performed in the initial two hours.
As the brightness adjustment control, the control calculation unit 50 calculates a contrast adjustment value using the brightness information and the temperature information, and causes the level adjustment unit 42 to execute the brightness level adjustment based on the contrast adjustment value.
The white balance adjustment function is also one of the functions for executing the brightness adjustment control executed after the brightness reduction control is performed in the initial two hours.
The control calculation unit 50 calculates the white balance adjustment value using the luminance information and the temperature information as the luminance adjustment control, and causes the level adjustment unit 42 to execute the luminance level adjustment based on the white balance adjustment value.
The burn-in prevention adjustment function is also one of the functions for executing the brightness adjustment control executed after the brightness reduction control is performed in the initial two hours.
As the brightness adjustment control, the control calculation unit 50 calculates the burn-in prevention white balance adjustment value using the brightness information, and causes the level adjustment unit 42 to execute the brightness level adjustment based on the burn-in prevention adjustment value. For example, brightness level adjustment control for preventing burn-in is performed together with the white balance adjustment.

  6 shows that the control calculation unit 50 is formed by a microcomputer or the like, for example, a one-dot chain line including a level adjustment unit 42, memory units 43, 46, and 47, and A / D converters 44 and 45. The range surrounded by can be configured by a single microcomputer or a video processing DSP.

  FIG. 7 shows a functional configuration for the control calculation unit 50 to realize the above functions. The configuration shown in the control calculation unit 50 in FIG. 7 may be realized by software. Of course, the control arithmetic unit 50 is formed by a microcomputer or the like, and a configuration in which the configuration of FIG. 7 is realized by hardware is also assumed.

  As shown in FIG. 7, the control calculation unit 50 includes a coefficient multiplication processing unit 51, a light emission luminance change detection unit 52, a temperature change detection calculation unit 53, a normalization processing unit 54, a reduced luminance calculation unit 55, a luminance control unit 56, A voltage calculation unit 57, an adjustment value calculation unit 58, and a relative luminance deterioration detection unit 59 are provided.

The coefficient multiplication processing unit 51 performs coefficient multiplication on the luminance level of each pixel of the input video signal stored in the memory unit 43 and supplies the result to the light emission luminance change detection unit 52.
The light emission luminance change detection unit 52 compares the luminance level of each pixel of the input video signal supplied via the coefficient multiplication processing unit 51 with the actual light emission luminance level of each pixel read from the memory unit 46, and emits light. The amount of change in luminance is detected.
The amount of change in light emission luminance is the difference (or ratio) between the signal value (brightness level) actually given to the pixel and the luminance level actually emitted from the pixel. In order to obtain the light emission luminance change amount by the light emission luminance change detection unit 52, the luminance level in the input video signal may be compared with the luminance level actually emitted. However, as described above, the amount of light emitted from each pixel 10 is detected by the light receiving sensor 36 receiving the leakage light SL. Therefore, it is not appropriate to directly compare the luminance level for each pixel 10 of the input video signal stored in the memory unit 43 with the luminance level detected in each pixel 10 stored in the memory unit 46.
Therefore, the coefficient multiplication processing unit 51 performs, for example, 20% multiplication on the luminance level read from the memory unit 43. This is because when the leakage light SL detected by the light receiving sensor 36 is about 20% with respect to the display light ML of the light emitting element 33, the luminance level value read from the memory unit 43 is set to the light amount level of the leakage light SL. It becomes processing to match. In this way, by multiplying the coefficient by the coefficient multiplication processing unit 51, the light emission luminance change detecting unit 52 can appropriately detect the light emission luminance change amount.

The temperature change detection calculation unit 53 reads the temperature information of each pixel read from the memory unit 47 and detects a temperature change.
In the memory unit 47, for example, temperature information for two frame periods is stored. In this case, the temperature information for two frame periods stored in the memory unit 47 is calculated for each pixel 10 by performing a difference calculation on each pixel 10. It is possible to detect temperature changes in units of frames. However, the temperature change does not necessarily need to be detected in units of frames. For example, the temperature change detection calculation unit 53 captures and stores the information in the memory unit 47 in units of a predetermined period such as a few seconds or a few minutes. The temperature change may be detected in units of a predetermined period of minutes.

The normalization processing unit 54 generates a standardized control parameter by using the light emission luminance change amount detected by the light emission luminance change detection unit 52 and the temperature change information obtained by the temperature change detection calculation unit 53.
FIG. 8 shows the temperature dependence of the relationship between the light emission luminance and the applied voltage to the organic EL element 1. The organic EL element 1 changes its emission luminance depending on the amount of current corresponding to the applied drive voltage, but itself has temperature dependence as shown in the figure. For example, when the driving voltage V1 is applied as an example, when the pixel temperature is 30 ° C., 45 ° C., and 60 ° C., the light emission luminances are different as L1, L2, and L3, respectively.
As described above, the light emission luminance of the organic EL element 1 is temperature-dependent. Then, only by the light emission luminance change amount obtained by the light emission luminance change detection unit 52, the deviation amount of the original light emission luminance (the video signal given to the pixel 10). There is a possibility that the luminance as a value and the actual emission luminance deviation accompanying deterioration of the organic EL element do not become an accurate value.
In view of this, the normalization processing unit 54 uses the temperature change information to calculate a control parameter that is standardized so that the light emission luminance change amount becomes the light emission luminance deviation amount to be corrected in the current temperature state.

The reduced luminance calculation unit 55 calculates a luminance level to be reduced step by step when executing the above-described initial forced luminance reduction function. For example, the stepwise luminance reduction control amount is calculated so that the luminance is reduced by 10% in a period of 2 hours.
In order to properly calculate the luminance reduction control amount, it is necessary to adjust the control amount calculated by monitoring information on the actual light emission luminance. Therefore, the light emission luminance change normalized by the normalization processing unit 54 is required. A quantity control parameter is entered.

When executing the above-described contrast adjustment function, white balance adjustment function, and burn-in prevention adjustment function, the voltage calculation unit 57 processes the numerical value supplied from the normalization processing unit 54 as a voltage value.
The voltage value processed by the voltage calculation unit 57, for example, the voltage value corresponding to the light emission luminance change amount is supplied to the adjustment value calculation unit.
The adjustment value calculation unit 58 performs a difference calculation, a division calculation, a comparison calculation with a predetermined conditional expression, and the like on the voltage supplied from the voltage calculation unit 57, and performs contrast adjustment, white balance adjustment, and burn-in prevention adjustment. An adjustment value is calculated.

The luminance control unit 56 outputs a control value for luminance adjustment to the level adjusting unit 42, for example, a coefficient given to the luminance level of each pixel of the input video signal, and the luminance level adjusting operation of the level adjusting unit 42 Is executed.
When executing the initial forced luminance reduction function, the luminance control unit 56 controls the level adjustment unit 42 based on a control value based on the luminance reduction control amount calculated by the reduced luminance calculation unit 55. Further, when executing contrast adjustment, white balance adjustment, and burn-in prevention adjustment, the level adjustment unit 42 is controlled based on the adjustment value calculated by the adjustment value calculation unit 58.

The relative luminance deterioration detection unit 59 detects the value of the relative luminance deterioration used particularly for the burn-in prevention adjustment. Relative luminance deterioration is, for example, the amount of change in luminance deterioration between a certain frame and the previous frame, and can be taken as the amount of change in light emission luminance change amount, for example.
This relative luminance deterioration is normalized by the normalization processing unit 54 according to the temperature characteristics as described above, and is used as a control parameter for preventing burn-in.

[4. Initial forced brightness reduction processing]

As described above, in this example, the initial forced luminance reduction process is first executed in the initial two hours from the start of driving. This process will be described with reference to FIGS.
First, the meaning of executing the initial forced luminance reduction process will be described with reference to FIG. FIG. 10 shows the luminance deterioration characteristics of the organic EL element 1 with the progress of the display drive time. Here, assuming that the luminance level at the start of driving is 1.0, the deterioration of the luminance level after the start of driving is shown as the relative luminance with respect to the driving start point.

In the organic EL element 1, the luminance deterioration proceeds very unstable during the initial predetermined period Tx from the driving start time. The predetermined period Tx is usually a period of about 2 hours from the start of driving. The luminance deterioration in the predetermined period Tx is completely indefinite as shown as characteristics C1, C2, and C3 in the figure, and it is difficult to predict the deterioration characteristics (unstable luminance transition period).
On the other hand, when the predetermined period Tx has passed since the start of driving, as shown as the characteristic C4, the luminance deterioration proceeds stably over a long period of time (stable luminance change period).
For such deterioration characteristics, prevent contrast changes and white balance changes due to sudden and unstable brightness changes at the beginning of driving, and properly change contrast and white balance during the subsequent period of stable brightness deterioration. Responding to changes is required.
In particular, when the luminance deterioration is stably advanced in the predetermined period Tx in the initial stage of driving, appropriate adjustment is easily performed after the predetermined period Tx has elapsed.
Therefore, in this example, the luminance level is forcibly controlled to be reduced in a predetermined period Tx in which the luminance transition is unstable, so that stable deterioration proceeds to a predetermined relative luminance.
Then, after the predetermined period Tx has elapsed, contrast adjustment and white balance adjustment are executed using the predetermined relative luminance as a starting point, thereby realizing an appropriate screen display that is stable over the long term.

For example, the initial forced luminance reduction process is executed as shown in FIG.
The predetermined period Tx is 2 hours from the start of driving. Then, control is performed so that the relative luminance is reduced by 10% after 2 hours from the start of driving.
In this case, as shown in FIG. 11, 2 hours are divided into 6 times by time Ta (for example, 20 minutes), and control is performed so that predetermined relative luminances La, Lb, Lc, and Ld are obtained at intermediate times of the respective intervals. As a result, as shown in the figure, for example, linear luminance deterioration is forcibly executed, and luminance reduction of 10% is realized in two hours for all pixels.

FIG. 9 shows a process of the control calculation unit 50 for the initial forced luminance reduction process.
From the point of time when the input video signal is supplied to the panel module 40 and display driving is started, the control calculation unit 50 performs the processing of FIG.
First, in step F100, an initial luminance numerical value discrimination process is performed. In this case, the brightness levels of all the pixels of the input video signal are fetched from the memory unit 43. Information on the luminance level of each pixel read from the memory unit 43 is taken into the emission luminance change detection unit 52 via the coefficient multiplication processing unit 51. This luminance level information is processed as an initial luminance value in the normalization processing unit 54. The initial luminance value is used as a reference value for subsequent calculation of the reduced luminance amount in the reduced luminance calculation unit 55.
In step F101, the first luminance level control is performed. That is, the reduced luminance calculation unit 55 calculates the initial luminance reduction amount for the purpose of reducing the luminance after two hours by 10% from the initial luminance value. For example, the first luminance reduction amount is determined by dividing the luminance level reduction amount corresponding to 10% by the number of times of luminance control execution in a period of 2 hours. Then, the luminance reduction amount is given to the luminance control unit 56.
The luminance control unit 56 controls the level adjustment unit 42 so as to decrease the luminance level for all the pixels of the input video signal by the luminance reduction amount. Thereby, the first luminance reduction is performed.

After the initial luminance numerical value determination process and the initial luminance level control are performed in steps F100 and F101, the control calculation unit 50 repeatedly executes the processes of steps F102 to F107 for a period until, for example, 2 hours elapse.
First, in step F102, the luminance level as a signal value input to each pixel from the memory unit 43 is read, and the luminance emitted from each pixel based on the signal detected by the light receiving sensor 36 from the memory unit 46. Information is read out.
Luminance information from the memory unit 46 is taken into the emission luminance change detection unit 52. Also, in accordance with the timing (that is, frame matching), information on the luminance level given to each pixel from the memory unit 43 is taken into the emission luminance change detection unit 52 via the coefficient multiplication processing unit 51.
In step F103, the light emission luminance change detection unit 52 compares the luminance information of each pixel read from each of the memory units 43 and 46, and obtains the amount of change in the light emission luminance. This light emission luminance change amount is a difference between the luminance level given to each pixel 10 and the actual light emission luminance of each pixel 10. In this case, the luminance reduction amount given to the input video signal by the level adjustment unit 42. Since the luminance level is reduced, it is a difference between the luminance levels emitted by the pixels 10, and therefore, the deviation of the original emission luminance corresponding to the reduced luminance level is expressed. become. That is, it is not known whether the reduced luminance as the actual control purpose is realized due to the unstable luminance deterioration state, but here, the emission luminance change amount is the difference between the luminance as the control purpose and the actual luminance.

In step F104, the emission luminance change amount is normalized together with the temperature information by the normalization processing unit 54, and supplied to the reduced luminance calculation unit 55 as a control parameter.
Note that the temperature information of each pixel 10 is fetched from the memory unit 47 to the temperature change detection calculation unit 53 sequentially (for example, every frame period or every predetermined time interval), and the normalization processing unit 54 detects the temperature change. The control parameter is calculated using the temperature change information from the calculation unit 53.

In step F105, the reduced luminance calculation unit 55 calculates a luminance level to be reduced. That is, the amount of luminance level to be reduced is adjusted using the control parameter from the normalization processing unit 54 so that the display luminance is stably reduced. For example, in order to reduce the luminance by 10% in 2 hours, the luminance reduction amount in one control step is fixedly calculated. However, due to the unstable luminance deterioration in the initial stage, the input video is actually fixed. Even if the luminance level of the signal is reduced, the corresponding luminance reduction is not executed in the display image. Therefore, the luminance reduction amount is adjusted by the control parameter including the light emission luminance change amount and the elements of the temperature information as described above.
In Step F106, the luminance control unit 56 causes the level adjustment unit 42 to perform the luminance level reduction based on the luminance reduction amount calculated by the reduced luminance calculation unit 55.
In step F107, the end of the initial forced luminance reduction process is determined based on whether or not two hours as the predetermined period Tx have elapsed. Until 2 hours elapse, the processes of steps F102 to F106 are repeated, and the initial forced luminance reduction process is terminated when 2 hours elapse.

As a result of the above processing, the luminance is forcibly reduced as shown in FIG. 11. For example, when two hours have elapsed, display is performed with all the pixels 10 being 10% lower than the initial luminance level. Will be.
That is, the luminance is stably reduced during a period of two hours after the start of driving, in which the deterioration progress is unstable. In this way, a 10% decrease in luminance is stably advanced, and starting from this state, a suitable display is realized by executing various adjustments described below during a period in which the luminance deterioration is stable.

In the above processing, the luminance reduction is similarly advanced for all the pixels 10. However, the luminance reduction may be caused to be different for each of the R pixel, the G pixel, and the B pixel.
The situation of luminance deterioration of the organic EL element 1 varies depending on the emission color. For example, FIG. 12 shows a state in which the luminance degradation of the pixels of each color proceeds differently as characteristics τR, τG, and τB.
In the unstable luminance transition period as the initial predetermined period Tx, the luminance degradation proceeds for each pixel of each color, and as a result, when the period Tx elapses, the relative luminance becomes a different value for each color. .
When the predetermined period Tx elapses and the stable luminance change period is reached, the luminance deterioration of the pixels of each color changes in substantially the same manner.
Considering such a situation, particularly considering the white balance adjustment described later, it is also preferable to execute the initial forced luminance reduction at a different ratio for each pixel of each RGB color.

FIG. 13 shows an example in which the luminance is controlled so as to be different for each color. Curves LR, LG, and LB in the initial predetermined period Tx are brightness levels to be forcibly controlled.
For example, in the initial two hours, the luminance is reduced by 5% for the R pixel, 8% for the G pixel, and 12% for the B pixel.
Regarding the processing to be executed, the processing in FIG. 9 may be performed in parallel for each of the RGB pixels.
In this way, the display brightness is controlled to a certain target brightness when the initial two hours have elapsed for each pixel of each color. Thereafter, in the stable luminance change period, stable white balance adjustment can be realized by performing white balance adjustment starting from the light emission luminance that is forcibly controlled after the elapse of 2 hours.

[5. Contrast adjustment process]

Subsequently, the contrast adjustment processing will be described with reference to FIG. This process is executed after the initial forced luminance reduction process for the initial predetermined period Tx from the start of driving. The period during which this contrast adjustment is performed is a period during which the luminance deterioration of the organic EL element 1 stably changes.

The control calculation unit 50 continuously and repeatedly executes the processes of steps F201 to F206 in FIG.
In step F201, the control calculation unit 50 acquires the luminance information of the high luminance pixels and the low luminance pixels in one frame.
In this case, the light emission luminance change detection unit 52 takes in luminance information emitted from each pixel based on the signal detected by the light receiving sensor 36 from the memory unit 46, and is a processing target in accordance with the timing. For the frame, the luminance level as a signal value input to each pixel from the memory unit 43 is taken in via the coefficient multiplication processing unit 51.
Then, the light emission luminance change detection unit 52 extracts the luminance information of the high luminance pixel and the low luminance pixel from the luminance information of each pixel of one frame taken in from each of the memories 43 and 46. A high luminance pixel is a pixel having the highest luminance level in one frame to be processed. Moreover, it becomes a low-luminance pixel and a pixel having the lowest luminance level in one frame.
Here, in each of the R pixel, G pixel, and B pixel, a high luminance pixel and a low luminance pixel are extracted. That is, luminance information of six pixels in one frame is extracted as a processing target.

In step F202, the light emission luminance change detection unit 52 detects each of the extracted six pixels, that is, a high luminance pixel and a low luminance pixel of the R pixel, a high luminance pixel and a low luminance pixel of the G pixel, and a high luminance pixel of the B pixel. A light emission luminance change amount is calculated for each low luminance pixel. That is, for each of these pixels, the luminance level read from the memory unit 43 and the luminance level read from the memory unit 43 are compared and calculated to calculate the emission luminance change amount.
As a result, for each of the extracted six pixels, the difference in the actual light emission luminance level with respect to the luminance level given as the signal value, that is, the difference caused by the luminance deterioration of the organic EL element 1 is obtained as the light emission luminance change amount. It is done.

The amount of change in luminance of these six pixels is normalized together with the temperature information by the normalization processing unit 54 in step F203 and supplied to the voltage calculation unit 57 as a control parameter.
Note that the temperature information of each pixel 10 is taken from the memory unit 47 into the temperature change detection calculation unit 53 sequentially (for example, every frame period or every predetermined time interval). It is the same as the case of. That is, after the start of driving, the temperature change detection calculation unit 53 continuously performs a temperature change detection operation and provides the standardization processing unit 54 with information on the temperature change.

In step F <b> 204, the voltage calculation unit 57 generates a voltage value corresponding to the emission luminance change amount corrected by the temperature characteristic as a control parameter for each of the six pixels, and supplies the voltage value to the adjustment value calculation unit 58.
In step F205, the adjustment value calculation unit 58 calculates a luminance adjustment value by comparison calculation. In the comparison calculation, the voltage value Lh corresponding to the amount of change in light emission luminance of the high luminance pixel and the voltage value L1 corresponding to the amount of change in light emission luminance of the low luminance pixel are divided to obtain Lh / Ll = C. Then, the luminance adjustment value is obtained so that the C value becomes a predetermined constant value.
For example, assume that a constant value as the C value is set to “2”.
It is assumed that the amount of change in light emission luminance of the high luminance pixel is 110%, and the voltage value Lh = 4.0V for this. Further, it is assumed that the light emission luminance change amount of the low luminance pixel is 105%, and the voltage value Ll = 1.5V.
In this case, 4.0 / 1.5 = 2.66..., And the C value does not become the constant value “2”. Here, for example, if a luminance decrease corresponding to 1.0 V is reflected for a high luminance pixel, the comparison calculation result is 3.0 / 1.5 = 2, and the C value can be a constant value. In this case, the brightness level adjustment value is calculated so as to decrease the voltage value Lh of the high brightness pixel by 1.0V.
When the adjustment value is calculated for each of the R pixel, the G pixel, and the B pixel, in step F206, the luminance adjustment unit 56 sets the luminance level of the corresponding pixel in the input video signal to the adjustment value. The level adjustment unit 42 is controlled so as to be changed based on this.

  That is, for each of the R pixel, the G pixel, and the B pixel, control is performed so that the luminance ratio between the high luminance pixel and the low luminance pixel is kept constant. As a result, the luminance deterioration of the organic EL element 1 and the luminance change corresponding to the temperature condition are reflected in the input video signal, and the contrast control can be realized promptly and appropriately corresponding to the deterioration condition and the temperature condition. In particular, if the luminance ratio between high-luminance pixels and low-luminance pixels is constant, it is recognized in the content that the contrast changes in human vision, so the above control maintains a constant contrast on the display. As a result, a smooth and uniform display can be provided.

  Note that the value of the constant value C is “2” as an example. In addition to the C value being a fixed value, the C value may be adaptively changed according to the actual luminance level. For example, when there are no high-luminance pixels that are white and low-luminance pixels that are black on the display screen, the luminance ratio between the high-luminance pixels and the low-luminance pixels in a certain frame is assumed to be small. Is done. Therefore, it may be preferable to change the C value according to the luminance values of the high luminance pixels and the low luminance pixels in the frame.

  In addition, the luminance ratio between the high luminance pixel and the low luminance pixel is adjusted so as to have a C value. In this case, not only the luminance control of the high luminance pixel is performed as in the above example, but also the low luminance pixel is adjusted. The luminance ratio may be set to C value by performing luminance control, or the luminance ratio may be set to C value by controlling the luminance of both high luminance pixels and low luminance pixels.

By the way, the video displayed and output by the panel module 40 may be a moving image or a still image. For example, in the light emission luminance change detection unit 52, the voltage output value of a certain frame N is V1N, and the previous frame (N -1) is recognized as the voltage output value V1 (N-1), and the difference V1N-V1 (N-1) between the two voltage output values is determined as the voltage output value V1 (N-1) of the frame (N-1). -1) When the calculated value when divided by 70 is 70% or more, it can be identified as a moving image.
When it is determined that the image is a still image, the above processing is performed using a numerical value obtained by multiplying the detected luminance level by a factor of 100, so that a calculation based on a subtle amount of change in emission luminance in the previous and subsequent frames is performed. The contrast adjustment can be suitably performed even in a still image. This also applies to the white balance adjustment process described later.

[6. White balance adjustment process]

Next, the white balance adjustment process will be described with reference to FIG. This process is also executed after the initial forced luminance reduction process for an initial predetermined period Tx from the start of driving. That is, the control calculation unit 50 continuously and repeatedly executes the processes of steps F301 to F306 in FIG.
As the initial forced luminance reduction process performed prior to the white balance adjustment process, the luminance reduction control may be performed uniformly for all pixels as described with reference to FIG. 11, but as described with reference to FIG. It is also preferable to perform the luminance reduction processing to a predetermined ratio that differs for each color.

  In step F301, the control calculation unit 50 acquires luminance information of each pixel in one frame. That is, the light emission luminance change detection unit 52 captures luminance information emitted from each pixel based on the signal detected by the light receiving sensor 36 from the memory unit 46, and the frame to be processed in accordance with the timing. The luminance level as a signal value input to each pixel from the memory unit 43 is taken in via the coefficient multiplication processing unit 51.

In step F302, the light emission luminance change detection unit 52 calculates a light emission luminance change amount for each pixel. That is, for each pixel, the luminance level read from the memory unit 43 and the luminance level read from the memory unit 43 are compared and calculated to calculate the emission luminance change amount.
As a result, for each pixel, the difference between the actual light emission luminance level and the luminance level given as a signal value, that is, the difference caused by the luminance deterioration of the organic EL element 1 is obtained as the light emission luminance change amount.

The amount of change in light emission luminance of each pixel is normalized together with the temperature information by the normalization processing unit 54 in step F303 and supplied to the voltage calculation unit 57 as a control parameter.
In step F <b> 304, the voltage calculation unit 57 generates a voltage value corresponding to the light emission luminance change amount corrected by the temperature characteristic as a control parameter for each pixel, and supplies the voltage value to the adjustment value calculation unit 58.
In step F305, the adjustment value calculation unit 58 calculates each luminance level adjustment value for the R pixel, the G pixel, and the B pixel for maintaining the white balance ratio.

In this example, the following X, Y, and Z are used as white balance ratio ratios in order to calculate an adjustment value for white balance adjustment.
X = VLR / (VLR + VLG + VLB)
Y = VLG / (VLR + VLG + VLB)
Z = VLB / (VLR + VLG + VLB)
It is. VLR is a voltage value corresponding to the light emission luminance change amount for the R pixel, VLG is a voltage value corresponding to the light emission luminance change amount for the G pixel, and VLB is a voltage value corresponding to the light emission luminance change amount for the B pixel.
As the white balance ratio ratio, for example, the numerical values of X, Y, and Z are set to 1/4, 5/8, and 1/8, respectively.

The voltage calculation unit 57 outputs voltage values reflecting the white balance ratio ratios of 1/4, 5/8, and 1/8 for the emission luminance change amounts LR, LG, and LB of the RGB pixels.
For example, it is assumed that the light emission luminance change amount LR for the R pixel is 2.5% and the voltage value VLR is supplied to the adjustment value calculation unit 58 as 2.5V. Further, the emission luminance change amount LG of the G pixel is 3%, and the voltage value VLG is supplied to the adjustment value calculation unit 58 as 3.0 V. Further, the emission luminance change amount LB for the B pixel is 4%, and the voltage value It is assumed that VLB is supplied to the adjustment value calculator 58 as 4.0V.
The adjustment value calculator 58 compares the voltage values VLR, VLG, and VLB. Then, an adjustment value is obtained based on the comparison result.
In this case, when X: Y: Z = 1/4: 5/8: 1/8 is satisfied, the voltage calculation unit 57 generates each voltage value so that the voltage value VLR = VLG = VLB. Yes.

  For example, when the voltage value VLR = 2.5V, the voltage value VLG = 3.0V, and the voltage value VLB = 4.0V as described above, the smallest emission luminance change amount is the R pixel emission luminance change amount. It can be recognized as LR. In this case, in order to maintain the white balance ratio, the voltage value VLG = 3.0V is set to 2.5V for the G pixel, and the voltage value VLB = 4.0V is set to 2.5V for the B pixel. Therefore, an adjustment value for reducing the luminance of the G pixel by 0.5 V may be calculated, and an adjustment value for reducing the luminance of the B pixel by 1.5 V may be obtained.

  When the adjustment value is calculated in this way, in step F306, the luminance adjustment unit 56 controls the level adjustment unit 42 so that the luminance level of each color pixel in the input video signal is changed based on each adjustment value.

By repeating the processes of steps F301 to F306 described above, white balance adjustment can be performed quickly and appropriately in accordance with the temperature state and the luminance deterioration state of the organic EL element 1.
Note that the luminance deterioration characteristic varies depending on the temperature, as illustrated in FIGS. The control parameter is generated using the information on the temperature change detected by the temperature change detection calculation unit 53, so that the adjustment based on the actual situation of the luminance deterioration is performed.

[7. Burn-in prevention and white balance adjustment processing]

Next, an example of processing when the adjustment for preventing burn-in and the white balance adjustment are performed simultaneously will be described with reference to FIGS. This process is also executed after the initial forced luminance reduction process for an initial predetermined period Tx from the start of driving. That is, the control calculation unit 50 continuously and repeatedly executes the processes in steps F401 to F409 in FIG.
In addition, as the initial forced luminance reduction processing performed prior to this processing, luminance reduction control that is uniform for all pixels may be performed as described in FIG. 11, but as described in FIG. It is also preferable to perform the luminance reduction processing to different predetermined ratios.

  In step F401, the control calculation unit 50 acquires luminance information of each pixel in one frame. That is, the light emission luminance change detection unit 52 captures luminance information emitted from each pixel based on the signal detected by the light receiving sensor 36 from the memory unit 46, and the frame to be processed in accordance with the timing. The luminance level as a signal value input to each pixel from the memory unit 43 is taken in via the coefficient multiplication processing unit 51.

In step F402, the light emission luminance change detection unit 52 calculates a light emission luminance change amount for each pixel. That is, for each pixel, the luminance level read from the memory unit 43 and the luminance level read from the memory unit 43 are compared and calculated to calculate the emission luminance change amount.
As a result, for each pixel, the difference between the actual light emission luminance level and the luminance level given as a signal value, that is, the difference caused by the luminance deterioration of the organic EL element 1 is obtained as the light emission luminance change amount.

The amount of change in light emission luminance of each pixel is normalized together with the temperature information by the normalization processing unit 54 in step F403 and supplied to the voltage calculation unit 57 as a control parameter.
In step F <b> 404, the voltage calculation unit 57 generates a voltage value corresponding to the light emission luminance change amount corrected by the temperature characteristic as a control parameter for each pixel, and supplies the voltage value to the adjustment value calculation unit 58.

In step F408, the adjustment value calculation unit 58 calculates the luminance level adjustment values for the R pixel, G pixel, and B pixel for maintaining the white balance ratio.
In step F408, a final adjustment value is generated by reflecting an adjustment element for preventing burn-in in an adjustment value for white balance adjustment. First, generation of a white balance adjustment value will be described here.

Also in this case, the following X, Y, and Z are used as white balance ratio ratios in order to calculate an adjustment value for white balance adjustment.
X = VLR / (VLR + VLG + VLB)
Y = VLG / (VLR + VLG + VLB)
Z = VLB / (VLR + VLG + VLB)
It is. VLR is a voltage value corresponding to the light emission luminance change amount for the R pixel, VLG is a voltage value corresponding to the light emission luminance change amount for the G pixel, and VLB is a voltage value corresponding to the light emission luminance change amount for the B pixel.
As the white balance ratio ratio, for example, the numerical values of X, Y, and Z are set to 1/4, 5/8, and 1/8, respectively.
The adjustment value calculation unit 58 compares each of the voltage values VLR, VLG, and VLB with the white balance ratio ratio so that the luminance level of each color is the white balance ratio ratio X: Y: Z = 1/4: 5 / An adjustment value such that 8: 1/8 is obtained.

The voltage calculation unit 57 outputs the light emission luminance change amounts LR, LG, LB of the RGB pixels and the voltage values VLR, VLG, VLB based on the temperature change. For example, the light emission luminance change amount LR for the R pixel is 110%. It is assumed that the voltage value VLR is supplied to the adjustment value calculator 58 as 4.4V. Further, the emission luminance change amount LG of the G pixel is 105%, the voltage value VLG is supplied to the adjustment value calculation unit 58 as 10.5 V, and there is no emission luminance change for the B pixel, and the voltage value VLB is 2.0 V. Is supplied to the adjustment value calculation unit 58.
The adjustment value calculator 58 compares these voltage values VLR, VLG, and VLB with the set X, Y, and Z values.
In this case, adjustment values are obtained so that the voltage values VLR, VLG, and VLB of 4.4V, 10.5V, and 2.0V are ratios of 1/4, 5/8, and 1/8. Therefore, it is only necessary to obtain adjustment values such that the voltage values VLR, VLG, and VLB are 4.0V, 10.0V, and 2.0V.
Therefore, a luminance adjustment value that reduces the voltage value VLR by 0.4 V is obtained for the R pixel, and a luminance adjustment value that reduces the voltage value VLG by 0.5 V may be obtained for the G pixel. .
The adjustment value obtained in this way is an adjustment value for realizing white balance adjustment.

On the other hand, the processes of steps F405, F406, and F407 are also performed.
In step F405, the relative luminance deterioration detecting unit 59 obtains the relative luminance deterioration ΔL as the change amount of the light emission luminance change amount. That is, it is a change amount of the light emission luminance change amount in the preceding and following frames, and is a value indicating the degree of the light emission luminance deterioration.
The relative luminance deterioration ΔL is normalized by the normalization processing unit 54 according to the temperature change in step F406.
In step F407, a voltage value corresponding to the relative luminance degradation ΔL normalized by the voltage calculation unit 57 is generated and supplied to the adjustment value calculation unit 58.

  The adjustment value calculation unit 58 calculates the relative luminance deterioration division coefficient by dividing the relative luminance deterioration ΔL for the two pixels, and calculates an adjustment value for preventing burn-in according to the calculation result.

For example, when the initial temperature is 30 ° C., the temperature of a certain first pixel becomes 60 ° C. after a certain period, and the normalized relative luminance degradation ΔL1 taking into account the degradation characteristics due to temperature change is 6%. Suppose that Further, it is assumed that the temperature of other second pixels is 45 ° C., and the normalized relative luminance degradation ΔL2 is 4% in consideration of the degradation characteristic due to the temperature change.
The voltage calculation unit 57 outputs a voltage value of 4.8 V when the relative luminance deterioration ΔL1 of the first pixel is 6%, and when the relative luminance deterioration ΔL2 of the second pixel is 4%, 3. Assume that a voltage value of 2V is output.
The adjustment value calculator 58 divides the relative luminance degradation ΔL2 of the second pixel from the relative luminance degradation ΔL1 of the first pixel. Specifically, voltage value 3.2V is divided from voltage value 4.8V. As a result, a relative luminance deterioration division coefficient of 1.5 is obtained.
Here, it is assumed that the adjustment value calculation unit 58 sets information as shown in FIG. 18 for the relative luminance deterioration division coefficient. That is, it is determination information for occurrence of burn-in according to the relative luminance deterioration division coefficient. For example, when the relative luminance deterioration division coefficient is in the range of 1.0 to 1.4, no burn-in recognition is detected, and when the relative luminance deterioration division coefficient is 1.5. It is assumed that burn-in recognition is recognized and burn-in recognition is recognized when the relative luminance deterioration division coefficient is 1.6 or more.

  When the relative luminance deterioration division coefficient is calculated as 1.5 as described above, it is necessary to control the relative luminance deterioration division coefficient to be 1.4 from FIG. That is, an adjustment value for reducing the relative luminance deterioration division coefficient by 0.10 is obtained. For example, the luminance may be adjusted so that the voltage value of the second pixel is higher than 0.23 V.

The adjustment value calculation unit 58 calculates the white balance adjustment value and the adjustment value for preventing burn-in, and generates an actual adjustment value by combining them.
The above is the process of step F408.
In step F409, based on the adjustment value generated by the adjustment value calculation unit 58, the luminance adjustment unit 56 sets the level so that the luminance level of each color pixel in the input video signal is changed based on each adjustment value. The adjustment unit 42 is controlled.

  By repeating the processes in steps F401 to F409, the burn-in prevention and the white balance adjustment can be performed quickly and appropriately in accordance with the temperature state and the luminance deterioration state of the organic EL element 1.

It is explanatory drawing of a structure of the organic electroluminescence display panel of embodiment of this invention. It is explanatory drawing of the pixel circuit of embodiment. It is explanatory drawing of the layer structure of the pixel of embodiment. It is explanatory drawing of the layer structure of the pixel of embodiment. It is explanatory drawing of arrangement | positioning of the light receiving sensor of embodiment. It is a block diagram of the principal part of the display apparatus of embodiment. It is a block diagram of a functional structure of the control calculating part of the display apparatus of embodiment. It is explanatory drawing of the temperature dependence of the relationship between light-emitting luminance and an applied voltage. It is a flowchart of the initial forced luminance reduction process of an embodiment. It is explanatory drawing of the luminance degradation characteristic of an organic EL element. It is explanatory drawing of the initial forced luminance reduction process of embodiment. It is explanatory drawing of the luminance degradation characteristic for every luminescent color of an organic EL element. It is explanatory drawing of the initial forced luminance reduction process for every luminescent color of embodiment. It is a flowchart of a contrast adjustment process of an embodiment. It is a flowchart of the white balance adjustment process of an embodiment. It is explanatory drawing of the luminance degradation characteristic according to temperature. 5 is a flowchart of burn-in prevention and white balance adjustment processing according to the embodiment. It is explanatory drawing of the relative-luminance degradation division coefficient of embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Organic EL element, 10 pixels 36 Light receiving sensor, 37 Temperature sensor, 40 Panel module, 42 Level adjustment part, 43, 46, 47 Memory part, 50 Control calculating part, 51 Coefficient multiplication process part, 52 Light emission luminance change detection part, 53 Temperature change detection calculation unit, 54 Normalization processing unit, 55 Reduced luminance calculation unit, 56 Brightness control unit, 57 Voltage calculation unit, 58 Adjustment value calculation unit, 59 Relative luminance deterioration detection unit

Claims (15)

A plurality of pixels using an organic electroluminescence element as a light emitting element, and a display unit configured to display an image by driving the pixels based on an input video signal;
A level adjusting unit for adjusting the luminance level of the video signal supplied to the display unit;
Luminance reduction control in which the level adjustment unit gradually decreases the luminance level of the video signal so that the luminance level of the video signal supplied to the display unit decreases in a predetermined period from the start of display driving of the display unit. A control operation unit for performing
A display device comprising:   The display device according to claim 1, wherein the control calculation unit performs control for uniformly reducing a luminance level of a video signal for all pixels of the display unit as the luminance reduction control.   2. The display according to claim 1, wherein the control calculation unit controls the luminance level of the video signal so that the luminance level of the video signal is decreased by 10% from the display driving start time when the predetermined period has elapsed as the luminance reduction control. apparatus.   The control calculation unit controls the luminance level of the video signal so that the luminance level of the video signal is decreased by a predetermined ratio from the display driving start point when the predetermined period has elapsed for each emission color of the pixel of the display unit as the luminance reduction control. The display device according to claim 1.   The display device according to claim 1, wherein the elapse of a predetermined period from the start of display driving is a time point of about 2 hours from the start of display driving. A luminance information detection unit for detecting information on the emission luminance of each of the pixels;
A temperature information detection unit for detecting information on the temperature of each of the pixels;
Further comprising
The control calculation unit ends the luminance reduction control after a predetermined period has elapsed from the start of the display drive, and sets an adjustment value using information from the luminance information detection unit and information from the temperature information detection unit. The display device according to claim 1, wherein brightness adjustment control is performed to cause the level adjustment unit to perform brightness level adjustment based on the adjustment value.   The control calculation unit calculates a contrast adjustment value using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and performs the level adjustment based on the contrast adjustment value. The display device according to claim 6, wherein the brightness level adjustment is executed by the unit.   The control calculation unit calculates a white balance adjustment value using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and based on the white balance adjustment value, The display device according to claim 6, wherein the level adjustment unit is configured to execute luminance level adjustment.   The control calculation unit calculates an adjustment value for preventing burn-in using the information from the luminance information detection unit and the information from the temperature information detection unit as the luminance adjustment control, and based on the adjustment value for burn-in prevention The display device according to claim 6, wherein the level adjustment unit is configured to execute luminance level adjustment. The luminance information detection unit
A first memory unit for storing luminance information of each pixel of the video signal supplied to the display unit;
A light receiving sensor for detecting a light emission amount of each pixel of the display unit;
A second memory unit that stores the light quantity of each pixel obtained by the light receiving sensor as luminance information of each pixel;
The control calculation unit detects the luminance change information of the pixel using the luminance information stored in the first memory unit and the luminance information stored in the second memory unit, and the emission luminance change information The display device according to claim 6, wherein the adjustment value is calculated using temperature information detected by the temperature detection unit. The light receiving sensor is configured to detect the amount of leaked light of each pixel, and the second memory unit stores the amount of leaked light of each pixel obtained by the light receiving sensor as luminance information of each pixel. With
The control calculation unit uses the value obtained by performing coefficient calculation on the luminance information stored in the first memory unit and the luminance information stored in the second memory unit to change the emission luminance of the pixel. The display device according to claim 10, wherein information is detected. The temperature information detector is
A temperature sensor for detecting temperature information of each pixel of the display unit;
And a third memory unit that stores the temperature of each pixel obtained by the temperature sensor as temperature information of each pixel. The control calculation unit uses the temperature information stored in the third memory unit. The display device according to claim 10, wherein temperature change information of a pixel is detected, and the adjustment value is calculated using the detected temperature change information and the light emission luminance change information.   The display device according to claim 10, wherein the light receiving sensor is arranged in a region between the light emitting elements of adjacent pixels when viewed in the plane direction of the display surface.   The display device according to claim 12, wherein the temperature sensor is disposed on a substrate opposite to a light extraction direction of a light emitting element of each pixel. As a display driving method of a display device having a display unit configured to display a video by driving each pixel based on an input video signal, which is formed by arranging a plurality of pixels using an organic electroluminescence element as a light emitting element,
Reducing the luminance level of the video signal supplied to the display unit stepwise in a predetermined period from the start of display driving of the display unit;
After a predetermined period from the start of the display drive, an adjustment value is calculated using the luminance information of the pixel of the display unit and the temperature information of the pixel of the display unit, and supplied to the display unit based on the adjustment value Adjusting the luminance level of the video signal to be
A display driving method characterized by comprising:

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