JP2005055800A - Deterioration compensation device of full color el display, full color el display on which the same is mounted, and deterioration compensation method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full color EL (electroluminescence)display, which can properly maintain white balance, regardless of the deterioration in pixels, and which can further improve brightness of the whole display panel. <P>SOLUTION: A brightness adjustment part (31A) amplifies the brightness of each of the R, G, and B designated by external picture information (L) by the reciprocal number of a threshold in the region where it is lower than each of the thresholds of R, G, and B, and fixes it at the upper limit value in the region where it is higher than the threshold. A picture signal (N) after the conversion is sent out to a driving part (2). A power supply management part (32) monitors the picture signal (N), and stores the sum total (C) of the power supply time or the accumulated amount of power supply, for each of the pixels of R, G, and B on the display panel (1). A deterioration information determination part (33) determines deterioration information (D) for each of the R, G, and B, from the total (C) of the power supply time or the accumulated amount of power supply of each of the pixels of R, G, and B. A threshold calculation (34A) interprets a preservation rate of the brightness of each of the R, G, and B, from the deterioration information (D), and sets the preservation rate, as the threshold, for each of the R, G, and B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inorganic EL (Electroluminescence) display or an organic EL display, and more particularly to a method for compensating for a decrease in luminance due to deterioration of the display panel.

EL refers to an image display technique using a light-emitting substance that “emits light when a voltage is applied”. In particular, a light-emitting substance that is inorganic is called inorganic EL, and an organic substance is called organic EL. The EL display is an image display device using EL. On the display panel, an element (light emitting element) having a light emitting substance layer (light emitting layer) sandwiched between electrodes is juxtaposed. A pixel of the display panel includes one or more light emitting elements. The EL display is a self-luminous type. In particular, the organic EL display is more advantageous than the liquid crystal display in terms of high brightness, high contrast, wide viewing angle, high response speed, ultrathinness, and low power consumption.
The EL display is mainly used as a small display to be mounted on a mobile electronic device such as a mobile phone. Further, it is expected to be used as a large display for lighting and TV.

  Among the EL displays, those capable of full color display are particularly called full color EL displays. A full-color EL display, like the screen of a color TV receiver, arranges pixels of the three primary colors of red (R), green (G), and blue (B) on the screen, and realizes a fine color image display.

Examples of the color display method in the full color EL display include a three-color light emission method, a filter method, and a color conversion method.
In the three-color light emission method, the light-emitting layers of the three primary color pixels are separately configured by three types of light-emitting substances of red light emission, green light emission, and blue light emission.
In the filter method, a common light-emitting layer is formed by the white light-emitting substance in the entire pixel. Further, the white light of the light emitting layer is colored by the color filters of the three primary colors, and the pixels of the three primary colors are configured.
In the color conversion method, a common light-emitting layer is formed in the entire pixel by a blue light-emitting material. Further, part of the blue light of the light emitting layer is converted into red light or green light by the red fluorescent film or the green fluorescent film. The converted primary light and the blue light from the light emitting layer itself constitute a primary color pixel.

In the three-color light emission method, unlike the other methods, light emitted from the pixels of the three primary colors is emitted to the outside without passing through a filter or the like. Therefore, the three-color light emission method is more advantageous than the other methods particularly in terms of luminance or light emission efficiency.
However, in EL, the tendency of the luminance to decrease due to deterioration of the light emitting layer differs greatly for each color (R, G, B) of light emitted by the light emitting layer. Therefore, in a full-color EL display using a three-color light emission method, the secular change in luminance differs greatly for each pixel color. Therefore, long-term use greatly deteriorates the white balance, that is, causes color shift.

  The deterioration of the light emitting layer mainly depends on the energization time, the energized electricity, and the temperature at the time of energization. The energization time and the energization electricity amount generally differ for each pixel color even in the filter method and the color conversion method. Therefore, even in a full color EL display using a filter method or a color conversion method, color shift may occur when used for a long period of time.

In the full color EL display, the decrease in the luminance of the pixel due to the deterioration of the light emitting layer is hereinafter referred to as the deterioration of the pixel.
A conventional full-color display is known in which the luminance of a pixel specified by video information is changed as follows to compensate for the deterioration of the pixel (see Patent Document 1). FIG. 16 is a block diagram showing a pixel deterioration compensation system of the full color display. This system inputs video information Ri, Gi, Bi of the three primary colors (RGB) from the outside in parallel. Further, the brightness designated by the video information Ri, Gi, Bi is changed based on the deterioration characteristics of the RGB pixels on the display panel P, and the white balance is adjusted. New video signals Ro, Go, and Bo obtained by changing the luminance are sent to the display panel P.

The pixel deterioration compensation system includes level monitoring units 101R, 101G, and 101B, a white balance adjustment unit 102, and a control unit 103.
The level monitoring units 101R, 101G, and 101B monitor RGB image information Ri, Gi, and Bi input from the outside, and detect the respective levels.
The white balance adjustment unit 102 changes the luminance indicated by the video information Ri, Gi, Bi for each of RGB by a predetermined ratio. Further, the video signals Ro, Go, and Bo whose luminance has been changed are sent to the display panel P in parallel.

  The control unit 103 controls level detection by the level monitoring units 101R, 101G, and 101B. In particular, every time a level higher than 0 is detected for video information Ri, Gi, Bi for each of the RGB pixels on the display panel P, the control unit 103 displays the product of a predetermined display rate and the frame period for that pixel. Add to the accumulated time.

Here, the cumulative display time of a pixel means a cumulative total of the light emission time (display time) of the pixel from the time when the display panel P is manufactured. The control unit 103 stores the total display time for each pixel on the display panel P.
The display rate (also referred to as duty ratio) refers to the ratio of the displayable time in one frame of one pixel to the frame period. The display rate is substantially determined by the driving method for the pixels on the display panel P. For example, the passive matrix method is substantially equal to 1 / (the number of horizontal scanning lines of the display panel), and the active matrix method is substantially equal to 1.

For the display panel P, the control unit 103 stores in advance a pixel degradation characteristic table and a minimum luminance maintenance rate. Here, the pixel deterioration characteristic table is a table showing the relationship between the luminance of the pixel and the total display time. The deterioration characteristic table is determined at the time of manufacturing the display panel P based on data obtained in advance by experiments. In the deterioration characteristic table, for example, the luminance when a constant driving voltage is applied is expressed as a relative value (hereinafter referred to as a maintenance factor) with respect to the luminance when the display panel P is manufactured.
Since the deterioration characteristics of the pixels are different for each RGB, the maintenance ratio of the luminance when the lifetime of the display panel P elapses is different for each RGB. Among those maintenance rates, the lowest maintenance rate is called the minimum maintenance rate. The minimum luminance maintenance rate is estimated based on a pixel deterioration characteristic table.

Based on the minimum luminance maintenance rate and the total display time of each pixel, the control unit 103 sets the change rate of the luminance of each RGB to the white balance adjustment unit 102 as follows. First, the control unit 103 reads a luminance maintenance rate corresponding to the total display time of each pixel from the pixel deterioration characteristic table. Next, a ratio of the minimum maintenance ratio to the read maintenance ratio is calculated, and the ratio is determined as a luminance change rate.
In this way, the actual display luminance maintenance rate of the display panel P is substantially equal to the minimum maintenance rate regardless of the deterioration of the pixels. As a result, collapse of the white balance due to pixel deterioration is suppressed.

JP 2002-6796 A

In the conventional full-color display, the pixel deterioration compensation system as described above aligns the actual luminance maintenance rate with the minimum maintenance rate at the time when the lifetime of the display panel has elapsed for each pixel on the display panel. Thereby, good white balance is maintained regardless of pixel degradation.
However, since the maintenance ratio of the luminance of the pixels is suppressed to the minimum maintenance ratio, it is difficult to further improve the luminance of the entire display panel.

  An object of the present invention is to provide a full-color EL display capable of maintaining a good white balance regardless of pixel deterioration and further improving the luminance of the entire display panel.

A deterioration compensation device for a full-color EL display according to the present invention comprises: (a) a display panel in which three primary color pixels each having a light emitting layer containing a light emitting substance and an electrode sandwiching the light emitting layer are arranged; and (b) A full color EL display having a drive unit for receiving a video signal from the outside, decoding a luminance of a pixel specified by the video signal, and supplying a driving current corresponding to the luminance to the pixel; The This degradation compensation device
(A) a deterioration evaluation unit for estimating a maintenance ratio of luminance with respect to pixel degradation based on the video signal for each of the three primary colors and sending the estimated maintenance ratio as deterioration information for each of the three primary colors; and
(B) (a) For each of the three primary colors, a threshold is set based on the degradation information, (b) the luminance of the pixel specified by the video information input from the outside is compared with the threshold for the color of that pixel, (c) (D) a luminance adjusting unit for saturating the luminance specified by the video signal in an area exceeding the threshold, corresponding to the entire range of luminance that can be specified by the video signal; Have

  Here, “saturate the luminance specified by the video signal in the region where the luminance specified by the video information exceeds the threshold value” means that the latter luminance can be specified for the former luminance region This means that the upper limit is fixed.

  The luminance specified by the video information may be linearly associated with the entire range of luminance that can be specified by the video signal in a range lower than the threshold. In addition, it may be associated non-linearly according to the input luminance characteristics of the display panel. That is, the luminance conversion by the luminance adjusting unit may be performed together with the gamma correction for the above-described video information.

  The degradation compensator according to the present invention corresponds to the entire range of brightness that can be specified by the video signal to the drive unit for the brightness of each of the three primary colors specified by the video information input from the outside, below the threshold for each color. Let At that time, in particular, the threshold value is appropriately set according to the deterioration of the pixels on the display panel. Thereby, in the range lower than the threshold value, the luminance attenuation due to the deterioration of the pixels is canceled out, and the luminance gradation in the original image is reproduced well by the display panel. In particular, on the high luminance side within the range, the actual display luminance by the display panel is maintained high regardless of the deterioration of the pixels. For example, when reproducibility of luminance gradation in a range lower than the above threshold is particularly important, such as when the luminance specified by video information input from the outside does not include a very high value, The deterioration compensator according to the invention is effective.

In the deterioration compensator according to the present invention, the deterioration evaluation unit is
(A) Energization management for calculating the energization time or energization amount of each pixel based on the video signal to the drive unit and accumulating the energization time or energization amount for each pixel color from the time of manufacture of the full color EL display Part; and
(B) A table or approximate expression showing the energization time-luminance characteristic or energized electricity quantity-luminance characteristic of a pixel for each color of the pixel is stored, and maintenance corresponding to the cumulative energization time or energized electricity quantity is stored from the table or approximate expression A deterioration information determining unit for obtaining the rate.
At that time, the deterioration evaluation unit may further detect the temperature of the pixel or the display panel during the operation of the full-color EL display, or the environmental temperature, and correct the deterioration information based on those temperatures.

Deterioration of a pixel depends on the color of the pixel, energization time, energization electricity amount, and temperature. The dependence is preliminarily measured by experiment and is preferably stored by the deterioration evaluation unit as an energization time-luminance characteristic table or an energization electricity quantity-luminance characteristic table. These characteristic tables show, for example, the relationship between an increase in energization time or amount of energization under a constant driving voltage and a decrease in luminance maintenance rate. Here, instead of these characteristic tables, an approximate expression indicating the above dependency may be stored.
The deterioration evaluation unit determines a maintenance rate corresponding to the cumulative energization time or the amount of energized electricity of each of the three primary colors from the characteristic table or the approximate expression as deterioration information for the color. As the deterioration information, that is, the maintenance rate is smaller, the deterioration of the pixel is more severe. In this way, the deterioration evaluation unit can accurately evaluate the deterioration of the pixel.

  In the deterioration compensation device according to the present invention, a threshold value calculation unit for setting a product of an upper limit value of luminance that can be specified by video information input from the outside and a maintenance factor for each of the three primary colors as a threshold value for each of the three primary colors, May be included in the brightness adjustment unit. At that time, in a range lower than the threshold value, the correspondence relationship between the luminance gradation specified by the video information and the actual display luminance gradation by the display panel is maintained as it is at the time of manufacturing the EL display. That is, in the range lower than the threshold, the luminance gradation indicated by the video information is reproduced well by the display panel regardless of the deterioration of the pixels. Further, the white balance is maintained as it is when the EL display is manufactured regardless of the deterioration of the pixels. Therefore, the color tone reproducibility by the display panel is maintained well.

In addition to the above, the brightness adjustment unit
(A) Maximum luminance detection unit for detecting the maximum luminance of each of the three primary colors for each frame in video information input from the outside;
(B) For each of the three primary colors, (a) find the relative value of the maximum luminance with respect to the upper limit of luminance that can be specified by the above video information, and (b) determine the ratio of the relative value to the maintenance rate as the luminance saturation. A saturation calculator for performing; and
(C) (a) Choose the color with the highest saturation among the three primary colors greater than 1 as the first color, the remaining two colors as the second color, and (b) the highest of the first color Set the brightness as the threshold for the first color, and (c) multiply the product of the above upper limit value and the second color retention rate by the saturation of the first color and use the result of the multiplication as the second color. A threshold value calculation unit for setting as a threshold value for the color may be included.

  When the deterioration of the pixels proceeds, the maximum value of the actual luminance by one pixel on the display panel is lower than the maximum luminance in each frame in the video information input from the outside. The maximum value of the actual luminance is estimated to be equal to the maintenance factor when expressed as a relative value with respect to the upper limit value. Therefore, the saturation level is higher than 1 when the maximum value is lower than the maximum luminance in each frame. Especially in the display panel, since the deterioration characteristics are greatly different for each color of the pixel, a situation in which the saturation degree is higher than 1 is likely to occur for only one of the three primary colors.

For the first color, the luminance adjusting unit can specify a luminance range lower than the maximum luminance in each frame in the video information input from the outside by a video signal to the driving unit. It corresponds to the whole range. As a result, the entire luminance gradation in the original video is reproduced well using the entire actual gradation of display luminance by the display panel. In particular, a decrease in luminance at a high luminance portion can be suppressed to a small level.
The luminance adjusting unit adjusts the luminance specified by the video signal for the second primary color other than the first color, that is, the second color, as described above. Thereby, a good white balance is maintained. In this way, the color tone of the original image is reproduced well by the display panel.

The degradation compensation method for a full color EL display according to the present invention is as follows:
(A) Step of inputting video information from outside;
(B) A step of converting the video information into a video signal to the drive unit, and in particular, the luminance specified by the video information for the pixels of the three primary colors juxtaposed on the display panel, and a predetermined value for the color of the pixel A range lower than the threshold value is made to correspond to the entire range of luminance that can be specified by the video signal to the drive unit, and the luminance specified by the video signal is saturated in a region exceeding the threshold value;
(C) supplying a driving current corresponding to the luminance of the pixel specified by the video signal to the pixel by the driving unit;
(D) estimating a luminance maintenance rate against pixel degradation based on the video signal for each of the three primary colors, and determining the estimated maintenance rate as degradation information for each of the three primary colors; and
(E) setting a threshold value based on deterioration information for each of the three primary colors.

  The luminance specified by the video information may be linearly associated with the entire range of luminance that can be specified by the video signal in a range lower than the threshold. In addition, it may be associated non-linearly according to the input luminance characteristics of the display panel. That is, the step of converting the video information into the video signal may be performed together with gamma correction for the video information.

  In the deterioration compensation method according to the present invention described above, for the brightness of each of the three primary colors specified by the video information input from the outside, the entire range of brightness that can be specified by the video signal to the drive unit is lower than the threshold for each color. Corresponding to At that time, in particular, the threshold value is appropriately set according to the deterioration of the pixels on the display panel. Thereby, in the range lower than the threshold value, the luminance attenuation due to the deterioration of the pixels is canceled out, and the luminance gradation in the original image is reproduced well by the display panel. In particular, on the high luminance side within the range, the actual display luminance by the display panel is maintained high regardless of the deterioration of the pixels. For example, when reproducibility of luminance gradation in a range lower than the above threshold is particularly important, such as when the luminance specified by video information input from the outside does not include a very high value, The degradation compensation method according to the invention is effective.

In the above degradation compensation method according to the present invention, the step of determining degradation information includes:
(A) a sub-step of calculating each energization time or energization amount of each pixel based on a video signal to the drive unit, and accumulating the energization time or energization amount from the time of manufacturing a full-color EL display for each pixel color; and ,
(B) a sub-step of obtaining a maintenance ratio corresponding to the cumulative energization time or energized electricity from a table or approximate expression showing energization time-luminance characteristics or energized electricity quantity-luminance characteristics of each pixel by color; May be. Furthermore, a sub-step for detecting the temperature of the pixel or the display panel or the environmental temperature during the operation of the full-color EL display, and a sub-step for correcting the deterioration information based on those temperatures may be added.

The deterioration characteristics of the pixels are stored as, for example, an energization time-luminance characteristic table or an energization electricity amount-luminance characteristic table. Instead of these characteristic tables, an approximate expression indicating deterioration characteristics may be stored.
In the step of determining the deterioration information, from the characteristic table or the approximate expression, the maintenance rate corresponding to the cumulative energization time or the amount of energized electricity of each of the three primary colors is determined as the deterioration information for the color. As the deterioration information, that is, the maintenance rate is smaller, the deterioration of the pixel is more severe. In this way, pixel degradation is accurately evaluated.

  In the step of setting the threshold value, the product of the upper limit value of luminance that can be specified by video information input from the outside and the maintenance ratio of each of the three primary colors may be set as the threshold value for each of the three primary colors. At that time, in a range lower than the threshold value, the correspondence relationship between the luminance gradation specified by the video information and the actual display luminance gradation by the display panel is maintained as it is at the time of manufacturing the EL display. That is, in a range lower than the threshold value, the luminance gradation indicated by the video information is reproduced well by the display panel regardless of pixel deterioration. Furthermore, the white balance is maintained as it is when the EL display is manufactured regardless of the deterioration of the pixels. Therefore, the color tone reproducibility by the display panel is maintained well.

Apart from the above, the step of setting the threshold value is
(A) A sub-step for detecting the maximum luminance of each of the three primary colors for each frame in video information input from the outside;
(B) For each of the three primary colors, a sub-step of calculating a relative value of the maximum luminance with respect to the upper limit value of luminance that can be specified by the video information, and calculating a ratio of the relative value to the maintenance ratio as luminance saturation;
(C) (a) Choose the highest saturation color among the three primary colors as the first color, and (b) set the maximum brightness of the first color as the threshold for the first color. Substeps; and
(D) Of the three primary colors, a color other than the first color is selected as the second color, the product of the above upper limit value and the maintenance ratio of the second color is multiplied by the saturation of the first color, and the multiplication result is obtained. A sub-step that is set as a threshold value for the second color.

When the deterioration of the pixels progresses, the maximum value of the actual luminance by one pixel on the display panel is lower than the maximum luminance in each frame in the video information input from the outside, and the above saturation exceeds 1. Especially in the display panel, since the deterioration characteristics are greatly different for each color of the pixel, a situation in which the saturation degree is higher than 1 is likely to occur for only one of the three primary colors.
In the step of determining the threshold value, a range of luminance lower than the maximum luminance in each frame in the video information input from the outside can be designated by the video signal to the driving unit for the first color. Corresponds to the full range of brightness. As a result, the entire gradation of luminance in the original image is reproduced well using the entire gradation of actual display luminance by the display panel. In particular, a decrease in luminance at a high luminance portion can be suppressed to a small level.
Further, for the colors other than the first color, that is, the second color among the three primary colors, the luminance specified by the video signal is adjusted as described above. Thereby, a good white balance is maintained. In this way, the color tone of the original image is reproduced well by the display panel.

  In the full color EL display according to the present invention, the deterioration compensator can specify a range lower than the threshold value for each of the three primary colors specified by the video information inputted from the outside by the video signal to the drive unit. Correspond to the entire range of brightness. At that time, in particular, the threshold value is appropriately set according to the deterioration of the pixels on the display panel. Thereby, in the range lower than the threshold value, the luminance attenuation due to the deterioration of the pixels is canceled out, and the luminance gradation in the original image is reproduced well by the display panel. In particular, on the high luminance side within the range, the actual display luminance by the display panel is maintained high regardless of the deterioration of the pixels. For example, when reproducibility of luminance gradation in a range lower than the above threshold is particularly important, such as when the luminance specified by video information input from the outside does not include a very high value, The deterioration compensator according to the invention is effective.

  In the above degradation compensator according to the present invention, the product of the upper limit value of luminance that can be specified by video information input from the outside and the maintenance ratio of each of the three primary colors may be set as a threshold for each of the three primary colors. At that time, in a range lower than the threshold value, the correspondence relationship between the luminance gradation specified by the video information and the actual display luminance gradation by the display panel is maintained as it is at the time of manufacturing the EL display. That is, in a range lower than the threshold, the luminance gradation indicated by the video information is reproduced well by the display panel regardless of the deterioration of the pixels. Further, the white balance is maintained as it is when the EL display is manufactured regardless of the deterioration of the pixels. Therefore, the color tone reproducibility by the display panel is maintained well.

  The degradation compensator according to the present invention may determine the threshold value for each frame in video information input from the outside as follows: the highest color (with a saturation level exceeding 1 in the frame) For the first color), the maximum luminance in the frame is set as a threshold value. On the other hand, for the other colors (second colors), the threshold value is set by multiplying the product of the upper limit value that can be specified by the video information and the maintenance rate by the saturation degree of the first color. Here, for the second color, the maximum luminance in the frame is lower than the threshold value. In this way, for each of RGB, the entire luminance gradation in each frame in the video information is reproduced well using the entire actual display luminance gradation by the display panel. In particular, a decrease in luminance at a high luminance portion can be suppressed to a small level. Furthermore, since the white balance is well maintained, the color tone reproducibility by the display panel is well maintained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings.
The following embodiments are all full-color organic EL displays. The present invention can also be implemented as a full-color inorganic EL display in the same manner as the following embodiments.

Embodiment 1
FIG. 1 is a block diagram showing a configuration of a full-color organic EL display according to Embodiment 1 of the present invention. This full-color organic EL display includes a display panel 1, a drive unit 2, and a deterioration compensation device 3A.

  The display panel 1 is an organic EL element, and is configured by stacking a plurality of layers on a glass substrate, for example. In particular, these layers include a light emitting layer and electrodes sandwiching the light emitting layer (not shown). Further, an electron injection layer, an electron transport layer, a hole injection layer, or a hole transport layer may be included between the light emitting layer and the electrode.

The light emitting layer includes, for example, a low molecular weight organic material such as an aluminum complex (Alq ₃ ) or a high molecular weight organic material such as polyphenylene vinylene (PPV) as a light emitting material. The color of light emitted from the light-emitting layer changes depending on the type of the light-emitting material or a dopant dye mixed with the light-emitting material in a very small amount.
The display panel 1 preferably follows a three-color light emission method. That is, the light emitting layer includes three types of light emitting materials, that is, a red light emitting material (R), a blue light emitting material (B), and a green light emitting material (G), and each constitutes a pixel. In addition, the display panel 1 may follow a filter method or a color conversion method. That is, the light emitting layer may constitute a pixel by a combination of a white light emitting material and three primary color filters, or a combination of a blue light emitting material and a red / green phosphor film.
Regardless of which method is used, on the display panel 1, pixels of the three primary colors are juxtaposed, for example, RGBRGB in the horizontal direction of the panel. As each pixel emits light with various luminances, the display panel 1 displays images of various colors (full colors).

The electrodes sandwiching the light emitting layer are preferably transparent electrodes made of ITO (Indium-Tin-Oxide), and the shape thereof differs depending on the driving method of the driving unit 2.
In the passive matrix system, the electrodes are a plurality of elongated plates. For example, anode plates are arranged in parallel with the vertical direction of the panel, and cathode plates are arranged in parallel with the horizontal direction of the panel. The light emitting layer is sandwiched between the anode and the cathode. In particular, when viewed from the front of the panel, the intersection of the anode and the cathode sandwiches one pixel in the light emitting layer. The drive unit 2 controls the potentials of the anode and cathode plates and applies individual drive voltages for each pixel.
In the active matrix method, for example, the anode is the same number of thin film pieces as the pixels in the light emitting layer, and the cathode is a thin film extending over the entire panel. One pixel in the light emitting layer is sandwiched between the anode piece and the cathode. That is, the anode is independent for each pixel, and the cathode is common to the entire pixel. Each pixel in the light emitting layer includes at least two thin film transistors (TFTs). These TFTs are connected to a piece of anode in contact with the pixel. The drive unit 2 controls on / off of the TFT in the pixel, and controls the potential of one piece of the anode in contact with the pixel. Thereby, an individual drive voltage is applied to each pixel.

The drive unit 2 receives the video signal N sent from the deterioration compensation device 3A, and decodes the luminance of the pixel designated by the video signal N. Here, the video signal N is transmitted in parallel for each of the three primary colors (RGB). The video signal N is, for example, a digital signal, and the luminances NR, NG, and NB of RGB are expressed as, for example, digital information of 256 gradations from 0 to 255. In addition, the video signal N may be an analog signal. In that case, the luminances NR, NG, and NB of RGB are expressed by analog signal levels, for example. The drive unit 2 converts the luminances NR, NG, and NB of RGB into drive voltage values, for example, and applies the drive voltages of the values to the RGB pixels. Accordingly, drive currents corresponding to the luminances NR, NG, and NB are supplied to the RGB pixels.
In addition, the drive unit 2 may convert the luminances NR, NG, and NB of RGB into drive current values and supply the drive currents of the values to the RGB pixels.

  The degradation compensation device 3A receives video information L from a device (not shown) outside the full-color organic EL display, such as a tuner, a digital camera, or a DVD drive, and outputs the video information L to the drive unit 2 Convert to signal N. In the conversion, in particular, the luminance indicated by the video information L is converted. The deterioration compensator 3A compensates for the deterioration of the pixels on the display panel 1 as shown below by converting the luminance.

Here, the video information L input from the outside is transmitted in parallel for each of the RGB, like the video signal N to the drive unit 2. The video signal L is, for example, a digital signal, and the luminances LR, LG, and LB of RGB are expressed as, for example, digital information of 256 gradations from 0 to 255. In addition, the video signal L may be an analog signal. In this case, the luminances LR, LG, and LB of RGB are expressed by analog signal levels, for example.
The transmission source device of the video information L may be mounted on the same mobile electronic device together with the full-color organic EL display. In addition, the video information L may be provided outside the electronic device on which the full-color organic EL display is mounted, and the video information L may be transmitted to the electronic device directly or through a network, for example, by cable or wireless.

  The configuration of the degradation compensation device 3A is roughly divided into a degradation evaluation unit and a luminance adjustment unit 31A. The deterioration evaluation unit includes an energization management unit 32 and a deterioration information determination unit 33. The luminance adjustment unit 31A includes a threshold value calculation unit 34A.

  As described below, the deterioration evaluation unit evaluates the deterioration of each of the RGB pixels on the display panel 1 based on the video signal N to the driving unit 2 with the maintenance ratio of the luminance, and determines the maintenance ratio as deterioration information D for each of the RGB. Determine as.

The energization management unit 32 monitors the video signal N to the drive unit 2. As a result, the energization time and the energization electricity amount of each pixel of the display panel 1 are calculated for each color of the pixel, for example, for each frame of the video signal N.
The energization time of the R pixel in one frame is calculated as follows, for example. When the luminance specified by the video signal N of the frame is 0 for any of the R pixels, the energization time of the R pixel in the frame is set to 0. On the other hand, when the luminance specified for one of the R pixels is greater than 0, the energization time of the R pixel in the frame is calculated by (frame period) × (duty ratio of display panel 1). Here, the duty ratio refers to the ratio of the operation time of one pixel in one frame to one frame period. The duty ratio is substantially equal to 1 / (the number of horizontal scanning lines of the display panel 1) in the passive matrix method, and substantially equal to 1 in the active matrix method.
The energization time of G or B pixels in one frame is determined in the same manner.

The energized electricity amount of the R pixel in one frame is calculated as follows, for example. First, the highest luminance value of R is detected from the video signal N of the frame, and the drive current corresponding to the highest luminance value is calculated. Here, the relationship between the luminance and the drive current is determined in advance by experiment for each RGB pixel, and a table or an approximate expression indicating the relationship is stored by the energization management unit 32. The table or approximate expression may be further different for each energization time or energization amount of R pixels. Next, the product of the drive current and the energization time of the R pixel in the frame is calculated, and the product is determined as the energization electricity amount of the R pixel in the frame.
The amount of energized electricity of the G or B pixel in one frame is determined in the same manner.

  The energization management unit 32 further accumulates the energization time and the energization electricity amount of each pixel of the display panel 1 from the time of manufacturing the full-color organic EL display for each RGB, and stores the accumulated values. The energization management unit 32 updates the above cumulative value for each of RGB, for example, for each frame of the video signal N to the drive unit 2.

For example, every time the number of frames of the video signal N to the drive unit 2 exceeds a predetermined number, the deterioration information determination unit 33 receives from the energization management unit 32 the accumulated value C of the energization time and energized electricity. Further, the deterioration information corresponding to each of the received cumulative values C is determined as follows.
The deterioration information determination unit 33 stores in advance an energization time-luminance characteristic table or an energized electricity amount-luminance characteristic table. Here, instead of these characteristic tables, an approximate expression indicating the dependency of the deterioration of the pixel on the energization time or the energization amount of electricity may be stored. The deterioration information determination unit 33 determines the luminance maintenance rate corresponding to the cumulative value C of the energization time or energization amount of each RGB pixel as the deterioration information D for each RGB from the characteristic table or the approximate expression.

FIG. 2 is a graph showing an outline of the energization time-luminance characteristics as the deterioration characteristics of the pixels on the display panel 1. The horizontal axis of FIG. 2 indicates the cumulative energization time since the display panel 1 was manufactured. The vertical axis in FIG. 2 indicates the luminance maintenance ratio, that is, the ratio of the actual luminance to the luminance at the time of manufacturing the display panel 1 (hereinafter referred to as initial luminance).
Particularly in the display panel 1, the deterioration characteristics of the pixels are greatly different between RGB. In FIG. 2, the degradation characteristics of each of RGB are indicated by a solid line, a broken line, and an alternate long and short dash line. For example, when the cumulative value of energization time reaches a certain value T, the maintenance rates of RGB are 0.75, 0.80, and 0.65. Actually, the cumulative value of the energization time itself differs between RGB. Therefore, the maintenance rate generally differs greatly between RGB.

Based on the video signal N to the drive unit 2, the deterioration evaluation unit determines deterioration information D for each of RGB for the display panel 1, and sends the deterioration information D to the threshold value calculation unit 34A in parallel for each RGB.
The threshold calculation unit 34A decodes the maintenance rates of RGB from the deterioration information D. Further, the product of the upper limit value 255 of luminance that can be designated by the video information L inputted from the outside and the maintenance ratio of each of RGB is calculated. Then, the respective products are set for the luminance adjustment unit 31A as the luminance threshold values for the respective RGB.

The luminance adjustment unit 31A converts the video information L input from the outside into the video signal N to the drive unit 2 based on the threshold values for RGB set by the threshold value calculation unit 34A as follows.
When the luminances of RGB specified by the video information L belong to a range lower than the respective RGB thresholds, the luminance adjusting unit 31A amplifies the respective luminances by the reciprocal times of the respective thresholds. As a result, the luminance range lower than the threshold value is linearly converted to the entire luminance range that can be designated by the video signal N to the drive unit 2.
When the luminances of RGB specified by the video information L exceed the RGB thresholds, the luminance adjustment unit 31A saturates the luminance specified by the video signal N to the drive unit 2. That is, the upper limit value is fixed to 255.

  The luminance conversion by the luminance adjusting unit 31A compensates for pixel degradation on the display panel 1 as follows, for example. FIG. 3 is a graph showing input / output characteristics related to the luminance of the display panel 1. The horizontal axis of FIG. 3 indicates the luminance specified by the video signal N to the drive unit 2 as a relative value to the upper limit value 255. The vertical axis in FIG. 3 indicates the actual display luminance by the pixels on the display panel 1 as a relative value with respect to the upper limit of the initial luminance.

  When the display panel 1 is manufactured, input / output characteristics relating to luminance are common between RGB (see the thin solid line Γ shown in FIG. 3). In particular, the upper limit value 1.0 of the luminance that can be specified by the video signal N to the drive unit 2 corresponds to the common output value 1.00 for all of RGB (see point A shown in FIG. 3). A white balance is set based on the common input / output characteristics.

When the operation time of the display panel 1 elapses to some extent, the pixels on the display panel 1 are deteriorated, and the actual display brightness by the display panel 1 is reduced for all of RGB. The degree of the reduction further differs between RGB. As a result, the input / output characteristics relating to the luminance of the display panel 1 are shifted between RGB.
For example, in FIG. 3, the luminance maintenance ratios of RGB are reduced to 0.75, 0.80, and 0.65. In particular, when the video signal N to the drive unit 2 specifies the upper limit value 1.0 of the luminance, the actual luminances of RGB are equal to 0.75, 0.80, and 0.65, and are different from each other. As described above, the deterioration of the pixels lowers the actual luminance of the display panel 1 and further destroys the white balance.

For example, when the input / output characteristics related to the luminance of the display panel 1 are shown in FIG. 3, that is, when the maintenance ratios of the luminances of RGB are equal to 0.75, 0.80, and 0.65, the luminance adjusting unit 31A receives the video information L input from the outside. The luminance indicated by is converted as follows.
FIG. 4 is a graph showing luminance conversion by the luminance adjusting unit 31A. The horizontal axis in FIG. 4 indicates the luminance specified by the video information L inputted from the outside, as a relative value to the upper limit value 255. The vertical axis in FIG. 4 indicates the luminance specified by the video signal N to the drive unit 2 as a relative value to the upper limit value 255.

The threshold calculation unit 34A sets the luminance threshold values (relative values to the upper limit values) ThR, ThG, and ThB for each of RGB to the maintenance ratios of 0.75, 0.80, and 0.65, respectively.
When the luminance of R indicated by the video information L input from the outside is lower than the threshold ThR = 0.75, the luminance adjusting unit 31A amplifies the luminance by the reciprocal 1 / ThR = 1 / 0.75 = 1.33 of the threshold ThR. When the luminance of R indicated by the video information L input from the outside is higher than the threshold ThR = 0.75, the luminance adjusting unit 31A fixes the luminance of R indicated by the video signal N to the driving unit 2 to the upper limit value 1.00. (Refer to the solid line shown in FIG. 4).
Similarly for G and B, the luminance adjusting unit 31A converts the luminance as indicated by broken lines and broken lines shown in FIG. That is, in the range lower than the respective threshold values ThG = 0.80 and ThB = 0.65, the luminance is amplified by the reciprocals of the respective threshold values 1 / ThG = 1.25 and 1 / ThB = 1.54, and in the region higher than the respective threshold values, the luminance is increased to the upper limit value 1.00. Secure to.

  FIG. 5 is a graph showing input / output characteristics relating to the luminance of the display panel 1 obtained as a result of luminance conversion (see FIG. 4) by the luminance adjusting unit 31A. The horizontal axis in FIG. 5 indicates the luminance specified by the video information L input from the outside as a relative value with respect to the upper limit value 255. The vertical axis in FIG. 5 indicates the actual display luminance by the pixels on the display panel 1 as a relative value with respect to the upper limit of the initial luminance.

As shown in FIG. 5, the input / output characteristics related to the luminance of each of RGB are within the input value range lower than the respective RGB threshold values ThR, ThG, ThB, and the input / output characteristics at the time of manufacturing the display panel 1 (details shown in FIG. 5). It coincides with the solid line Γ). In particular, in the range of input values lower than the minimum threshold value ThB = 0.65 among the RGB threshold values ThR, ThG, ThB, the input / output characteristics are common between RGB. Therefore, in the input value range 0 to 0.65, the actual display luminance gradation by the display panel 1 is maintained substantially equal to the initial luminance gradation. Furthermore, the white balance is maintained well.
For example, when the luminance specified by the video information L input from the outside does not include many values higher than 0.65, especially when the reproducibility of the luminance gradation in the range 0 to 0.65 is particularly important, the luminance adjustment The luminance conversion by the unit 31A can maintain the image quality of the display panel 1 high.

FIG. 6 is a flowchart of the deterioration compensation method according to Embodiment 1 of the present invention.
<Step S1>
Video information L is input from the outside to the luminance adjustment unit 31A.
<Step S2>
The luminance adjustment unit 31A decodes the luminance of each of RGB indicated by the video information L.
<Step S3>
The luminance adjustment unit 31A converts the luminance of each RGB based on a luminance threshold value for each of RGB.

FIG. 7 is a flowchart of luminance conversion (step S3) by the luminance adjusting unit 31A.
Sub-step SS1: For each RGB, the decoded luminance is compared with a threshold value. When the luminance is lower than the threshold value, the process proceeds to sub-step SS2. When the brightness is higher than the threshold, the process branches to sub-step SS3.
Sub-step SS2: Calculate the product of the decoded luminance and the reciprocal of the threshold value, and set the product as a new luminance.
Substep SS3: The upper limit value 1.0 of luminance is set as a new luminance.
Sub-step SS4: It is checked whether or not the luminance conversion has been completed for each of RGB. When the luminance conversion is completed for all RGB, the process proceeds to step S4. Otherwise, the process is repeated from substep SS1.

<Step S4>
The luminance adjusting unit 31A sends the converted luminances of RGB to the driving unit 2 as the video signal N to the driving unit 2.
<Step S5>
The driving unit 2 decodes the luminance of each pixel on the display panel 1 from the video signal N from the deterioration compensation device 3A, and applies a driving voltage corresponding to the luminance to the pixel. Thereby, a driving current corresponding to the luminance is supplied to the pixel. Thus, the pixels on the display panel 1 emit light with the luminance specified by the video signal N.

<Step S6>
The deterioration evaluation unit evaluates the deterioration of the pixels on the display panel 1 for each RGB based on the video signal N to the drive unit 2. FIG. 8 is a flowchart of pixel deterioration evaluation for the display panel 1 by the deterioration evaluation unit.

Sub-step SS11: Based on the video signal N to the drive unit 2, the energization management unit 32 determines the energization time and drive current of each of the RGB pixels on the display panel 1 for each frame in the video signal N as follows: Calculate.
When the luminance specified by one frame in the video signal N is 0 for any of the R pixels, the energization time of the R pixel in that frame is set to 0. On the other hand, when the luminance specified for one of the R pixels is greater than 0, the energization time of the R pixel in the frame is calculated by (frame period) × (duty ratio of display panel 1). The energization time of the G or B pixel is calculated in the same manner.
The driving current of the R pixel in one frame is determined from the maximum value of the R luminance in the frame. The drive current of the G or B pixel is calculated in the same way.
Sub-step SS12: The energization management unit 32 calculates the product of the energization time of each RGB pixel and the drive current for each frame, and determines it as the energization electricity amount of each RGB pixel in that frame: (energization electricity amount) = (Drive current) x (energization time).
Sub-step SS13: The energization management unit 32 accumulates the energization time and energization amount of each RGB pixel from the time of manufacturing the full-color organic EL display, and stores the accumulated value for each of RGB. The energization management unit 32 updates the above cumulative value for each of RGB for each frame of the video signal N to the drive unit 2.

Substep SS14: The frame is counted from the start of transmission of the video signal N to the drive unit 2. The deterioration evaluation is finished as it is until the number of frames exceeds a predetermined number. When the number of frames exceeds the predetermined number, the process proceeds to substep SS15.
Sub-step SS15: The deterioration information determination unit 33 receives from the energization management unit 32 the energization time and energized electricity amount C of each of the RGB pixels. Further, the deterioration information determination unit 33 reads the maintenance ratio of the luminance corresponding to each of the received cumulative values C from the energization time-luminance characteristic table or the energized electricity amount-luminance characteristic table, and sets it as deterioration information D for each of RGB. In this way, the deterioration information D for RGB for the display panel 1 is sent in parallel to the threshold value calculation unit 34A.

<Step S7>
The threshold calculation unit 34A decodes the maintenance rates of RGB from the deterioration information D. Further, the product of the upper limit value of luminance that can be specified by the video information L inputted from the outside and the maintenance ratio of each of RGB is calculated. Then, the respective products are set for the luminance adjustment unit 31A as the luminance threshold values for the respective RGB. Thereafter, the process is repeated from step S1.

  As described above, the degradation compensation device 3A according to the first embodiment of the present invention has a video signal to be supplied to the drive unit 2 within a range lower than the above-described threshold value in the luminance gradation specified by the video information L input from the outside. It corresponds to the entire range of brightness that can be specified by N (see Fig. 4). At that time, the product of the upper limit value of the luminance that can be specified by the video information L and the respective RGB maintenance rates is set as a threshold value. Thereby, in the range lower than the threshold, the luminance attenuation due to the deterioration of the pixel is offset, and the correspondence between the luminance gradation specified by the video information L and the actual display luminance gradation by the display panel 1, It is maintained as it was when the organic EL display was manufactured (see FIG. 5). In particular, on the high luminance side within the range, the actual display luminance by the display panel 1 is kept high regardless of the deterioration of the pixels. Further, the white balance is maintained as it is when the organic EL display is manufactured regardless of the deterioration of the pixels. Therefore, the color tone reproducibility by the display panel 1 is maintained well. For example, when the luminance specified by the video information L does not frequently exceed the threshold value for any of RGB, when the reproducibility of the luminance gradation in a range lower than the threshold value is particularly important, the deterioration compensation device Degradation compensation by 3A is effective.

  As shown in FIG. 4, the luminance adjusting unit 31A amplifies the luminance by a certain factor for each RGB in a range lower than the threshold, that is, converts it into a linear form. In addition, the luminance belonging to the range may be converted nonlinearly. That is, gamma correction based on the input luminance characteristics of the display panel 1 may be performed simultaneously.

<< Embodiment 2 >>
FIG. 9 is a block diagram showing a configuration of a full-color organic EL display according to Embodiment 2 of the present invention. This full-color organic EL display differs from that according to the first embodiment in the configuration of the deterioration compensation device 3B, particularly the configuration of the brightness adjusting unit 31B. For other configurations, the first embodiment and the second embodiment are common. Accordingly, in FIG. 9, the same reference numerals as those in FIG. Furthermore, the description of those common components is the same as that in the first embodiment.

  The degradation compensation device 3B receives video information L from a device (not shown) outside the full-color organic EL display, such as a tuner, a digital camera, or a DVD drive, and outputs the video information L to the drive unit 2 Convert to signal N. In the conversion, in particular, the luminance indicated by the video information L is converted. The deterioration compensator 3B compensates for the deterioration of the pixels on the display panel 1 as shown below by converting the luminance.

  The configuration of the degradation compensation device 3B is roughly divided into a degradation evaluation unit and a luminance adjustment unit 31B. The degradation evaluation unit includes an energization management unit 32 and a degradation information determination unit 33 as in the first embodiment. The luminance adjustment unit 31B includes a maximum luminance detection unit 35, a saturation calculation unit 36, and a threshold calculation unit 34B.

The maximum luminance detection unit 35 monitors the video information L input from the outside to the luminance adjustment unit 31B, and detects the maximum luminance of each RGB for each frame in the video information L. Here, the maximum luminance detection unit 35 identifies each frame in the video information L based on, for example, a vertical synchronization signal (not shown) multiplexed on the video information L or input in parallel with the video information L.
Information M indicating the maximum luminance of each detected RGB or a relative value with respect to its upper limit 255 is transmitted to the saturation calculation unit 36 in parallel.

Based on the video signal N to the drive unit 2, the degradation evaluation unit determines degradation information D for each of RGB for the display panel 1, and sends the degradation information D to the saturation calculation unit 36 and the threshold calculation unit 34B in parallel for each RGB. To do.
First, the saturation calculation unit 36 obtains relative values MR, MG, and MB with respect to the upper limit value 255 of the maximum luminance of each RGB based on the information M received from the maximum luminance detection unit 35.
On the other hand, the RGB maintenance rates DR, DG, and DB are decoded from the deterioration information D. The saturation calculation unit 36 further determines the ratios MR / DR, MG / DG, and MB / DB of the relative values of the maximum luminance with respect to the maintenance ratio as luminance saturations SR, SG, and SB for each of RGB: SR = MR / DR, SG = MG / DG, SB = MB / DB. Information S indicating the degree of saturation of each of RGB is transmitted to the threshold value calculation unit 34B.

The threshold calculation unit 34B first decodes the maintenance rates DR, DG, and DB of RGB from the deterioration information D. On the other hand, based on the information S received from the saturation calculation unit 36, saturations SR, SG, and SB of RGB are obtained and compared with each other. Thereby, the color having the highest saturation and higher than 1 is selected as the first color, and the color other than the first color is set as the second color.
Further, the threshold value calculation unit 34B sets the first color for the luminance adjustment unit 31B with the highest luminance as a threshold value. On the other hand, for the second color, the product of the upper limit value and the maintenance factor multiplied by the saturation degree of the first color is set for the luminance adjustment unit 31B as a threshold value.

The luminance adjustment unit 31B converts the video information L input from the outside into a video signal N to the drive unit 2 based on the threshold set by the threshold calculation unit 34B as follows. Here, this luminance conversion is the same as in the first embodiment.
When the luminance specified by the video information L belongs to a range lower than the threshold, the luminance adjusting unit 31B amplifies the luminance by the inverse number of the threshold. As a result, the luminance range lower than the threshold value is linearly converted to the entire luminance range that can be designated by the video signal N to the drive unit 2.
When the luminance specified by the video information L exceeds the threshold, the luminance adjusting unit 31B saturates the luminance specified by the video signal N to the driving unit 2. That is, the upper limit value is fixed to 255.

When the deterioration of the pixels proceeds, the maximum value of the actual display brightness by the display panel 1 is lower than the maximum brightness in each frame in the video information L inputted from the outside, and the saturation is higher than 1. In the display panel 1, the deterioration characteristics are particularly different for each RGB, so that a situation in which the saturation degree is higher than 1 is likely to occur in only one of RGB colors.
The luminance conversion by the luminance adjusting unit 31B compensates for the deterioration of the pixels on the display panel 1 as follows, particularly under such a situation.

Here, as in the first embodiment, it is assumed that the display panel 1 exhibits the input / output characteristics shown in FIG. That is, due to the deterioration of the pixels on the display panel 1, the maintenance ratios of the respective luminances of RGB are reduced to DR = 0.75, DG = 0.80, DB = 0.65.
The degradation evaluation unit estimates the maintenance rates DR = 0.75, DG = 0.80, DB = 0.65 for each RGB based on the video signal N to the drive unit 2, and calculates the saturation calculation unit 36 and the threshold as degradation information D for each RGB. Notify unit 34B.

In general, the luminance specified by the video information L input from the outside shows a different distribution for each frame. Assume that when the display panel 1 shows the input / output characteristics shown in FIG. 3 with respect to luminance, the luminance specified by the video information L is distributed in one specific frame, for example, according to the graph shown in FIG.
The horizontal axis in FIG. 10 indicates the luminance specified by the video information L in 256 gradations from 0 to 255. The vertical axis in FIG. 10 indicates the appearance frequency in the frame for each luminance of RGB.
The luminances of RGB are distributed as indicated by solid lines, broken lines, and alternate long and short dash lines in FIG. In particular, the maximum luminance in each frame of RGB is 180, 210, 160.

The maximum luminance detection unit 35 detects the maximum luminances of RGB, 180, 210, and 160 for the frame indicating the luminance distribution shown in FIG.
The saturation calculation unit 36 calculates the relative values MR, MG, and MB of the maximum luminance with respect to the luminance upper limit value 255: MR = 180/255 = 0.71, MG = 210/255 = 0.82, MB = 160/255 = 0.63 . Further, the ratios of relative values of maximum brightness MR / DR, MG / DG, MB / DB with respect to the respective RGB maintenance factors DR = 0.75, DG = 0.80, DB = 0.65 are calculated, and brightness saturation SR, SG, SB SR = MR / DR = 0.71 / 0.75 = 0.94, SG = MG / DG = 0.82 / 0.80 = 1.03, SB = MB / DB = 0.63 / 0.65 = 0.97.

  In the assumptions of FIG. 3 and FIG. 10, only the saturation of G is higher than 1: SG = 1.03. That is, for G, the maximum value of the actual display brightness by the display panel 1 is lower than the maximum brightness in one frame in the video information L. Therefore, when the luminance specified by the video information L (relative value with respect to the upper limit value 255) exceeds the maintenance factor, the actual luminance by the display panel 1 can uniformly reach only the maintenance factor times the upper limit of the initial luminance.

The threshold calculation unit 34B compares the respective RGB saturation levels SR = 0.94, SG = 1.03, and SB = 0.97. Thereby, the color with the highest saturation and higher than 1, that is, G is selected as the first color. On the other hand, R and B are treated as the second color.
The threshold calculation unit 34B further sets the maximum luminance (relative to the upper limit 255) MG for the first color G as the threshold ThG for the luminance adjustment unit 31B: ThG = MG = 0.82. On the other hand, for the second colors R and B, the product of the maintenance ratio DR = 0.75, DB = 0.65 and the saturation degree SG = 1.03 of the first color G is the respective threshold value (relative to the upper limit 255) ThR, ThB is set for the luminance adjustment unit 31B: ThR = DR × SG = 0.75 × 1.03 = 0.77, ThB = DB × SG = 0.65 × 1.03 = 0.67.

  Table 1 is a table showing the maintenance ratio, the maximum luminance in a specific frame, the saturation, and the threshold value for each of RGB.

The luminance adjustment unit 31B converts the luminance indicated by the video information L input from the outside based on the above threshold values (relative values to the upper limit value 255) ThR, ThG, ThB as follows. This luminance conversion is the same as in the first embodiment.
FIG. 11 is a graph showing the conversion of luminance by the luminance adjusting unit 31B. The horizontal axis of FIG. 11 indicates the luminance specified by the video information L input from the outside as a relative value with respect to the upper limit value 255. The vertical axis in FIG. 11 indicates the luminance specified by the video signal N to the drive unit 2 as a relative value to the upper limit value 255.

When the luminance of R indicated by the video information L input from the outside is lower than the threshold value ThR = 0.77, the luminance adjustment unit 31B amplifies the luminance by the reciprocal 1 / ThR = 1 / 0.77 = 1.29 of the threshold value ThR. When the luminance of R indicated by the video information L input from the outside is higher than the threshold value ThR = 0.77, the luminance adjustment unit 31B fixes the luminance of R indicated by the video signal N to the driving unit 2 to the upper limit value 1.00. (Refer to the solid line shown in FIG. 11).
Similarly for G and B, the luminance adjusting unit 31B converts the luminance as indicated by broken lines and broken lines shown in FIG. That is, in the ranges lower than the respective threshold values ThG = 0.82 and ThB = 0.67, the luminance is amplified by the reciprocals of the respective threshold values 1 / ThG = 1.22 and 1 / ThB = 1.49, and in the region higher than the respective threshold values, the luminance is increased to the upper limit value 1.00. To fix.

  FIG. 12 is a graph showing input / output characteristics related to the luminance of the display panel 1 obtained as a result of luminance conversion (see FIG. 11) by the luminance adjusting unit 31B. The horizontal axis of FIG. 12 indicates the luminance specified by the video information L input from the outside as a relative value with respect to the upper limit value 255. The vertical axis in FIG. 12 indicates the actual display luminance by the pixels on the display panel 1 as a relative value with respect to the upper limit of the initial luminance.

  As shown in FIG. 12, for the first color G, the entire luminance range 0 to MG = ThG in a specific frame in the video information L is the entire actual display luminance range 0 to DG by the display panel 1. Corresponding to In particular, the luminance gradation is reproduced well by the display panel 1 near the maximum luminance MG = ThG in the frame. Furthermore, the actual display brightness drop by the display panel 1 can be minimized.

On the other hand, for the second colors R and B, the ranges 0 to ThR and 0 to ThB lower than the respective threshold values ThR and ThB correspond to the entire ranges 0 to DR and 0 to DB of the actual display brightness by the display panel 1, respectively. To do. In particular, the slopes of the straight lines indicating the respective correspondences coincide with the straight line slope 1 / SG = 0.97 indicating the input / output characteristics relating to the luminance of the first color G. Here, the threshold values ThR and ThB for R and B are higher than the respective maximum luminances MR and MG in the above frame. Therefore, since the input / output characteristics relating to luminance are common between RGB in the frame, the white balance on the display panel 1 is maintained well.
In particular, when the maximum luminance in each frame in the video information L input from the outside is maintained substantially constant between frames, the luminance conversion by the luminance adjustment unit 31B maintains the image quality of the display panel 1 high. it can.

FIG. 13 is a flowchart of a deterioration compensation method according to Embodiment 2 of the present invention. In FIG. 13, the same steps as those in FIG. 6 are assigned to the steps common to the degradation compensation method according to the first embodiment. Further, those common steps are the same as those in the first embodiment.
<Step S8>
The maximum luminance detection unit 35 monitors the video information L input from the outside to the luminance adjustment unit 31B, and detects the maximum luminance of each RGB for each frame in the video information L.
FIG. 14 is a flowchart of detection of the maximum luminance (step S8) by the maximum luminance detector 35.

Substep SS20: When the input of the video information L to the brightness adjusting unit 31B is started, the maximum brightness detecting unit 35 initializes the maximum brightness of each of RGB to 0.
Sub-step SS21: Every time the video information L input to the brightness adjusting unit 31B specifies new brightness for each of RGB, the maximum brightness detecting unit 35 compares the new brightness of each of RGB with the maximum brightness so far. When the new brightness is higher than the previous maximum brightness, the process proceeds to sub-step SS22. When the new luminance is lower than the previous maximum luminance, the process branches to substep SS23.
Substep SS22: Set a new brightness as the maximum brightness.
Sub-step SS23: It is checked whether or not the comparison between the new luminance and the maximum luminance is completed for each of RGB. When the comparison is completed for all RGB, the process proceeds to sub-step SS24. Otherwise, the process is repeated from substep SS21.
Sub-step SS24: The maximum luminance detection unit 35 checks the vertical synchronization signal multiplexed with the video information L or input in parallel with the video information L, and detects the switching of frames in the video information L. When a frame change is detected, the process proceeds to substep SS25. In other cases, the detection of the maximum luminance ends, and the process branches to step S3.
Sub-step SS25: The maximum luminance detection unit 35 sends the maximum luminance of each RGB at that time to the saturation calculation unit 36.

<Step S9>
A luminance threshold is set based on the maximum luminance and the degradation information.
FIG. 15 is a flowchart of threshold value setting (step S9).
Substep SS31: The saturation calculation unit 36 obtains relative values MR, MG, and MB with respect to the upper limit 255 of the maximum luminance of each RGB. Further, for each of RGB, the ratio MR / DR, MG / DG, MB / DB of the relative value of the maximum luminance to the maintenance ratio is determined as the luminance saturation SR, SG, SB: SR = MR / DR, SG = MG / DG, SB = MB / DB. Information S indicating the degree of saturation of each of RGB is transmitted to the threshold value calculation unit 34B.
Sub-step SS32: The threshold calculation unit 34B compares the saturation levels SR, SG, and SB of RGB with each other. Thereby, the color with the highest saturation is selected as the first color, and the color other than the first color is set as the second color. Further, the highest saturation is set as the highest saturation.

Sub-step SS33: Compare maximum saturation with 1. When the maximum saturation is higher than 1, the process proceeds to substep SS34. When the maximum saturation is lower than 1, the process branches to substep SS36.
Sub-step SS34: The threshold calculation unit 34B sets the first color for the luminance adjustment unit 31B with the highest luminance as a threshold.
Sub-step SS35: The threshold value calculation unit 34B sets, for the second color, the luminance adjustment unit 31B with a threshold value obtained by multiplying the product of the upper limit value and the maintenance ratio by the saturation degree of the first color.
Sub-step SS36: As in step S7 (see FIG. 6) according to the first embodiment, the threshold value calculation unit 34B sets the product of the upper limit value and the maintenance rate as the respective RGB threshold values in the luminance adjustment unit 31B.
After sub-step SS35 and sub-step SS36, the process is repeated from step S1.

  As described above, the degradation compensator 3B according to the second embodiment of the present invention has all the luminances that can be specified by the video signal N to the drive unit 2 in a range lower than the luminance threshold value specified by the video information L input from the outside. It corresponds to the range (see FIG. 11). At that time, the threshold value is determined for each frame in the video information L as follows: For the highest color (first color) with the saturation degree exceeding 1 in the frame, the maximum luminance in the frame is set as the threshold value. Set as. On the other hand, for the other colors (second colors), the threshold value is set by multiplying the product of the upper limit value that can be specified by the video information L and the maintenance ratio by the saturation degree of the first color. Here, for the second color, the maximum luminance in the frame is lower than the threshold value. Thus, for each of RGB, the entire gradation of luminance in each frame in the video information L is reproduced well using the entire gradation of actual display luminance by the display panel 1. In particular, a decrease in luminance at a high luminance portion can be suppressed to a small level (see FIG. 12). Furthermore, since the white balance is maintained well, the color tone reproducibility by the display panel 1 is maintained well.

  As shown in FIG. 11, the luminance adjusting unit 31B amplifies the luminance by a certain factor for each RGB in a range lower than the threshold, that is, converts it into a linear form. In addition, the luminance belonging to the range may be converted nonlinearly. That is, gamma correction based on the input luminance characteristics of the display panel 1 may be performed simultaneously.

  The present invention relates to a degradation compensator for a full color EL display and a degradation compensation method thereof. According to the present invention, the luminance of the video information is converted as described above, and the luminance attenuation due to pixel deterioration is offset. Thereby, the display panel maintains a good white balance regardless of the deterioration of the pixels, and improves the overall luminance. Therefore, the present invention can be utilized industrially.

It is a block diagram which shows the structure of the full color organic electroluminescent display by Embodiment 1 of this invention. 4 is a graph showing an outline of energization time-luminance characteristics as the deterioration characteristics of the pixels on the display panel 1 in Embodiment 1 of the present invention. 4 is a graph showing input / output characteristics related to luminance of the display panel 1 in Embodiment 1 of the present invention. It is a graph which shows the conversion of the brightness | luminance by 31 A of brightness | luminance adjustment parts about Embodiment 1 of this invention. 5 is a graph showing the input / output characteristics relating to the luminance of the display panel 1 obtained as a result of luminance conversion by the luminance adjusting unit 31A in the first embodiment of the present invention. It is a flowchart of the deterioration compensation method by Embodiment 1 of this invention. 6 is a flowchart of luminance conversion by a luminance adjustment unit 31A according to the first embodiment of the present invention. 6 is a flowchart of pixel deterioration evaluation on the display panel 1 by a deterioration evaluation unit according to the first embodiment of the present invention. It is a block diagram which shows the structure of the full color organic EL display by Embodiment 2 of this invention. It is a graph which shows distribution in the specific one flame | frame of the brightness | luminance designated by the video information L input from the outside about Embodiment 2 of this invention. It is a graph which shows the conversion of the brightness | luminance by the brightness | luminance adjustment part 31B about Embodiment 2 of this invention. It is a graph which shows the input / output characteristic regarding the brightness | luminance of the display panel 1 obtained as a result of the brightness | luminance conversion by the brightness | luminance adjustment part 31B about Embodiment 2 of this invention. It is a flowchart of the deterioration compensation method by Embodiment 2 of this invention. 10 is a flowchart of detection of the maximum luminance by the maximum luminance detection unit 35 in the second embodiment of the present invention. It is a flowchart of the setting of a threshold value about Embodiment 2 of this invention. It is a block diagram which shows the pixel deterioration compensation system of the conventional full color display.

Explanation of symbols

L Video information input from outside
N Video signal to drive unit 2
C Cumulative value of energization time and energization of pixels on display panel 1
D Degradation information for each RGB

Claims (9)

A display panel in which three primary color pixels having a light-emitting layer containing a light-emitting substance and electrodes sandwiching the light-emitting layer are juxtaposed; and
A driving unit for receiving a video signal from the outside, decoding the luminance of the pixel specified by the video signal, and supplying a driving current corresponding to the luminance to the pixel;
A device mounted on a full color EL display comprising:
A deterioration evaluation unit for estimating a maintenance ratio of luminance with respect to deterioration of the pixel based on the video signal for each of the three primary colors, and sending the estimated maintenance ratio as deterioration information for each of the three primary colors; and
A threshold value is determined for each of the three primary colors based on the deterioration information, the luminance of the pixel specified by the video information input from the outside is compared with the threshold value for the color of the pixel, and a range lower than the threshold value is compared with the video signal. A luminance adjusting unit for corresponding to the entire range of luminance that can be specified by the method and saturating the luminance specified by the video signal in a region exceeding the threshold;
A deterioration compensator having The deterioration evaluation unit is
An energization management unit for calculating each energization time or energized electricity amount of the pixel based on the video signal, and accumulating the energization time or energized electricity amount from the time of manufacturing the full-color EL display for each pixel color; and ,
A table or an approximate expression indicating the energization time-luminance characteristic or the energization electricity amount-luminance characteristic of the pixel for each color of the pixel is stored, and the energization time or the accumulated energization amount corresponding to the energization time is calculated from the table or the approximate expression. Deterioration information determination unit for obtaining the maintenance rate;
The deterioration compensator according to claim 1, comprising:   The brightness adjustment unit includes: a threshold value calculation unit configured to set a product of an upper limit value of luminance that can be specified by the video information and the maintenance ratio of each of the three primary colors as the threshold value for each of the three primary colors. Deterioration compensation device. The brightness adjusting unit is
A maximum luminance detector for detecting the maximum luminance of each of the three primary colors for each frame in the video information;
For each of the three primary colors, a saturation calculation unit for obtaining a relative value of the highest luminance with respect to an upper limit value of luminance that can be specified by the video information, and determining a ratio of the relative value to the maintenance ratio as a luminance saturation. ;as well as,
Among the three primary colors, the color with the highest degree of saturation higher than 1 is selected as the first color, the remaining two colors are selected as the second color, and the highest brightness of the first color is selected as the first color. And the product of the upper limit value and the maintenance ratio of the second color is multiplied by the saturation degree of the first color, and the multiplication result is set as the threshold value for the second color. Threshold calculation unit for
The deterioration compensator according to claim 1, comprising: A display panel in which three primary color pixels having a light-emitting layer containing a light-emitting substance and electrodes sandwiching the light-emitting layer are juxtaposed;
A driving unit for receiving a video signal from the outside, decoding the luminance of the pixel specified by the video signal, and supplying a driving current corresponding to the luminance to the pixel;
And
A deterioration evaluation unit for estimating a maintenance ratio of luminance with respect to deterioration of the pixel for each of the three primary colors based on the video signal and sending the estimated maintenance ratio as deterioration information for each of the three primary colors; and for each of the three primary colors; On the other hand, a threshold value is determined based on the deterioration information, the luminance of the pixel specified by the video information input from the outside is compared with the threshold value for the color of the pixel, and a range lower than the threshold value can be specified by the video signal A degradation compensation device comprising: a luminance adjustment unit that corresponds to the entire range of luminance and saturates luminance specified by the video signal in a region exceeding the threshold value;
A full-color EL display. Inputting video information from outside;
The step of converting the video information into a video signal to the drive unit, and in particular, the luminance specified by the video information for the pixels of the three primary colors juxtaposed on the display panel, and a predetermined threshold for the color of the pixel Comparing, and matching a range lower than the threshold to the entire range of luminance that can be specified by the video signal, and saturating the luminance specified by the video signal in a region exceeding the threshold;
Supplying a driving current corresponding to the luminance of the pixel designated by the video signal to the pixel by the driving unit;
Estimating a maintenance ratio of luminance against deterioration of the pixel based on the video signal for each of the three primary colors, and determining the estimated maintenance ratio as deterioration information for each of the three primary colors; and
Setting the threshold based on the degradation information for each of the three primary colors;
A deterioration compensation method for a full color EL display. Determining the degradation information comprises:
Sub-step of calculating each energizing time or energized electricity amount of the pixel based on the video signal, and accumulating the energizing time or energized electricity amount from the time of manufacturing a full color EL display for each color of the pixel; and
A sub-step of obtaining the maintenance rate corresponding to the total of the energization time or the energized electricity amount from a table or an approximate expression showing the energization time-luminance characteristic or the energized electricity amount-luminance characteristic of the pixel by color;
The deterioration compensation method for a full-color EL display according to claim 6, comprising:   The full color EL display according to claim 6, wherein in the step of setting the threshold value, a product of an upper limit value of luminance that can be specified by the video information and the maintenance ratio of each of the three primary colors is set as the threshold value for each of the three primary colors. Degradation compensation method. Setting the threshold comprises:
A sub-step of detecting the highest luminance of each of the three primary colors for each frame in the video information;
A sub-step of obtaining a relative value of the maximum luminance with respect to an upper limit value of luminance that can be specified by the video information for each of the three primary colors, and calculating a ratio of the relative value to the maintenance ratio as a luminance saturation;
Selecting the highest saturation color among the three primary colors as the first color and setting the highest luminance of the first color as the threshold for the first color; and
Of the three primary colors, a color other than the first color is selected as the second color, the product of the upper limit value and the maintenance ratio of the second color is multiplied by the saturation degree of the first color, and the multiplication result is obtained. Setting a sub-step as the threshold for the second color;
The deterioration compensation method for a full-color EL display according to claim 6, comprising:

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