JP2005037783A - Full color el display controller with monochromatic mode, full color el display loading it thereon, and method for suppressing color drift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full color EL display, capable of suppressing the color drift due to a difference in the deterioration of pixels among R, G and B by more degrading the luminance in a monochromatic mode with the colors with which the deterioration of pixels is more intensive. <P>SOLUTION: A signal selection section (31) selects video information (L) from the outside in a color mode with a video signal (M) from a light emission shield section (35) in the monochromatic mode, as a video signal (N) to a driving section (2). A management section (32) for turning on of electricity monitors the video signal (N) to the driving section (2) and memorizes the cumulative totals of the time for turning on of electricity or the electric quantity of turning on of electricity since the time of manufacturing over the entire part of each pixels of R, G and B on a display panel (1). A decision section (33) for deterioration information determines the deterioration information for each of the R, G and B from the cumulative totals of the time for turning on of electricity or the electric quantity of turning on of electricity. A selection section (34) for light emission discontinuation colors compares the deterioration information among the R, G and B and sets the colors intensively deteriorating the pixels as the light emission discontinuation colors when their differences exceed the prescribed threshold. The light emission shield section (35) converts the luminance of the pixels of the light emission discontinuation colors in the video information (L) from the outside to a zero. <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 suppressing color shift 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 superior to the liquid crystal display in terms of high brightness, high contrast, wide viewing angle, high response speed, extremely thin thickness, 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.

In general, displays are roughly classified into an area color type and a full color type. There are both types of EL displays.
An area color display is a display in which a plurality of relatively wide monochromatic light emitting areas are generally combined. Monochromatic pixels are arranged in each monochromatic light emitting area. The area color display is used for display of a relatively simple pattern such as an in-vehicle display or an in-vehicle guidance display.
A full-color display is a display in which pixels of the three primary colors red (R), green (G), and blue (B) are juxtaposed on the screen, similar to the screen of a color TV receiver, and is used for displaying fine color images. The

When the area color EL display is mounted on a mobile electronic device, it is used as a sub monitor for displaying a relatively simple pattern such as a destination / incoming telephone number, communication state, operation mode, remaining battery capacity, or error code. .
When mounted on a mobile electronic device, the full-color EL display is used as a main monitor for displaying a fine color image such as an Internet connection screen (homepage) or an image by a CCD. The full-color EL display generally has a monochrome display function (monochrome mode) in addition to the original color display function (color mode). The mobile electronic device instructs the color mode or the monochrome mode for the full-color EL display according to the application. For example, the mobile electronic device selects the monochrome mode when displaying the above-described relatively simple pattern, and displays the pattern in monochrome.

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 kinds 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 in the entire pixel by a material that emits white light. 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 material that emits blue light. 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 amount of electricity 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.
As a conventional full-color EL display, there is known one that compensates for deterioration of a pixel by an increase in driving voltage for the pixel as described below (see Patent Document 1).
FIG. 10 is a block diagram showing a pixel deterioration compensation system of the full color EL display.
The full color EL display drives an organic EL panel by an active matrix method. FIG. 10 shows an example P of an equivalent circuit per pixel on the display panel. This equivalent circuit P employs an active matrix system as a driving system. In the active matrix system, each pixel P includes TFTs (thin film transistors) T1 and T2. A drive unit (not shown) controls on / off of the TFTs T1 and T2 of the pixel P through the control signal lines S1 and S2.

When both the TFTs T1 and T2 of the pixel P are turned on, the drive voltage Vd is applied from the voltage adjusting unit 100 to the light emitting element El of the pixel P. Thereby, the light emitting element El emits light.
The voltage adjusting unit 100 adjusts the drive voltage Vd to be applied to the light emitting element El of the pixel P as follows. When both TFTs T1 and T2 are in the on state, the switch 101 switches the connection from the first contact a to the second contact b. Thereby, the first constant current I1 flows from the first constant current source 102 to the light emitting element El. At that time, the voltage measuring unit 103 measures the voltage V across the light emitting element El and notifies the voltage adjusting unit 100 of the measured value V. The voltage adjustment unit 100 calculates the equivalent resistance value of the light emitting element El based on the measured value V and the first constant current I1. Further, the drive voltage Vd is determined based on the equivalent resistance value and the drive current corresponding to the predetermined luminance. Since the light-emitting element El increases the equivalent resistance value due to deterioration, the luminance is lowered with respect to a constant drive voltage Vd. The voltage adjustment unit 100 calculates the amount of decrease in luminance from the increment of the equivalent resistance value, and increases the drive voltage Vd by a height necessary for compensating for the decrease. Thus, the deterioration of the pixel P is compensated by the increase of the drive voltage Vd.

The equivalent resistance value of the light emitting element El depends on the temperature of the light emitting element El, that is, the display panel. The temperature measurement unit 104 measures the temperature of the display panel as follows. A second constant current I2 is supplied from the second constant current source 105 to a light emitting element (hereinafter referred to as a temperature detection element) Ex disposed outside the image display area on the display panel. At that time, the temperature measurement unit 104 measures the voltage Vx across the temperature detection element Ex, and calculates the equivalent resistance value of the temperature detection element Ex based on the measurement value Vx and the second constant current I2. Further, the temperature detection element Ex, that is, the temperature T of the display panel is calculated from the resistance-temperature characteristics of the temperature detection element Ex.
The calculated temperature T of the display panel is notified to the voltage adjusting unit 100. The voltage adjusting unit 100 corrects the equivalent resistance value of the light emitting element El based on the temperature T. Thereby, the driving voltage Vd is appropriately adjusted according to the temperature T of the display panel.

FIG. 10 shows a pixel deterioration compensation system for driving in the active matrix system. On the other hand, the driving voltage to be applied to the light emitting element is determined based on the voltage across the light emitting element when the light emitting element conducts at a constant current, similarly to the driving in the passive matrix system (see Patent Document 1). 6). Thereby, the deterioration of the pixel is compensated by the increase of the driving voltage.
JP 2002-229513 A

  The pixel deterioration compensation system using the conventional full-color EL display as described above increases the drive voltage as the pixel is more deteriorated, and compensates for a decrease in luminance due to the deterioration. However, an increase in drive voltage promotes pixel degradation. As a result, it has been difficult to further extend the period during which white balance can be maintained satisfactorily, that is, the period during which color misregistration can be effectively suppressed.

  The present invention reduces the luminance of a color whose pixel degradation is more severe during the operation period in the monochrome mode, thereby effectively suppressing the color shift caused by the difference in pixel degradation among the three primary colors over a long period of time. The purpose is to provide a display.

A full-color EL display control device (hereinafter abbreviated as a control device) according to the present invention includes (a) a pixel of three primary colors having a light-emitting layer containing a light-emitting substance and an electrode sandwiching the light-emitting layer therebetween. A display panel; and (b) a drive unit for receiving a video signal from the outside, decoding a luminance of a pixel designated by the video signal, and supplying a driving current corresponding to the luminance to the pixel; It is mounted on a full color EL display. This full-color EL display control device is a display control device for converting video information input from the outside into a video signal to the drive unit;
(A) a deterioration evaluation unit for evaluating pixel deterioration for each of the three primary colors based on the video signal and determining the evaluation value as deterioration information for each of the three primary colors; and
(B) When a mode selection signal is received from the outside and the mode selection signal indicates a monochrome mode, the luminance of the pixel specified by the video information input from the outside is reduced based on the deterioration information for the color of the pixel. And a luminance adjusting unit for setting as a video signal to the driving unit.

  Here, the monochrome mode refers to a function of aligning the display on the display panel to a predetermined single color (for example, gray). A full color EL display generally has a monochrome mode in addition to a color mode. For example, a mobile electronic device equipped with a full-color EL display indicates a color mode or a monochrome mode for the full-color EL display in accordance with the application. The mobile electronic device selects the monochrome mode when displaying a relatively simple pattern such as a destination / incoming telephone number, a communication state, an operation mode, a remaining battery capacity, or an error code. Thereby, those simple patterns are displayed in monochrome.

The control device according to the present invention evaluates the deterioration of the pixels on the display panel for each of the three primary colors based on video information input from the outside. When the monochrome mode is selected, the control device reduces the luminance of the pixel to be designated to the driving unit according to the deterioration of the pixel evaluated for the color of the pixel. Thereby, the luminance in the monochrome mode is lowered as the color of the pixel is more deteriorated, and the deterioration of the pixel of the color can be suppressed.
The difference in pixel degradation between the three primary colors is magnified in the color mode. However, it is reduced in the monochrome mode. In this way, the control device according to the present invention described above can suppress an increase in the difference in deterioration of the pixels among the three primary colors over a long period of time and maintain a good white balance. That is, color misregistration can be effectively suppressed over a long period of time.

In the control device 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) Store a table or approximate expression showing energization time-luminance characteristics or energized electricity quantity-luminance characteristics for each pixel color, and obtain a value corresponding to the cumulative energization time or energized electricity quantity from the table or approximate expression, A deterioration information determination unit for determining the value as deterioration information. 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 amount-luminance characteristic table for each of the three primary colors. These characteristic tables show, for example, the relationship between the increase in energization time or the amount of energized electricity and the attenuation of luminance under a constant drive voltage. Here, instead of these characteristic tables, an approximate expression indicating the above dependency may be stored.
The degradation evaluation unit obtains a value corresponding to the cumulative energization time or energized electricity amount for each pixel color from the characteristic table or approximate expression, and determines the value as degradation information for the color. Here, the deterioration information is represented by, for example, a rate (hereinafter referred to as an attenuation factor) in which luminance under a certain driving voltage is attenuated from luminance at the time of manufacture (hereinafter referred to as initial luminance). At that time, as the deterioration information, that is, the attenuation rate is larger, the deterioration of the pixel is more severe.
In this way, the deterioration evaluation unit can evaluate pixel deterioration for each of the three primary colors. The evaluation may be started when the difference in pixel degradation between the three primary colors is slight, especially when a full-color EL display is manufactured. As a result, the difference in deterioration of the pixels among the three primary colors can be kept small, so that the white balance is maintained well.

In the control device according to the present invention, the brightness adjustment unit is
(A) A light emission stop color selection unit for selecting one or two of the three primary colors as a light emission stop color based on the deterioration information;
(B) a light emission blocking unit for changing the luminance specified for the pixel of the emission stop color by the video information input from the outside to substantially zero and setting it as a video signal to the drive unit; and
(C) (a) When the mode selection signal indicates the color mode, the video information input from the outside is selected as the video signal to the drive unit. (B) When the mode selection signal indicates the monochrome mode, A signal selection unit for selecting a video signal sent from the blocking unit as a video signal to the drive unit.
At that time, in the monochrome mode, the pixels of the emission stop color do not substantially emit light, and the deterioration is suppressed. Therefore, by setting a color whose pixel degradation is severe as the emission stop color, the difference in pixel degradation among the three primary colors is reduced in the monochrome mode. In this way, the difference in pixel degradation among the three primary colors can be kept small, and color misregistration can be effectively suppressed.

Apart from the above, the brightness adjustment unit
(A) An attenuation amount determination unit for determining an attenuation amount of luminance for each pixel color based on deterioration information;
(B) An attenuation unit for reducing the luminance of a pixel designated by video information input from the outside by the above-mentioned attenuation amount for each color of the pixel and setting it in the video signal to the drive unit; and
(C) (a) When the mode selection signal indicates the color mode, the video information input from the outside is selected as the video signal to the drive unit. (B) When the mode selection signal indicates the monochrome mode, attenuation A signal selection unit for selecting a video signal transmitted from the unit as a video signal to the drive unit.
At this time, by setting the luminance attenuation amount to be larger for a color with more severe pixel degradation, the difference in pixel degradation between the three primary colors is reduced in the monochrome mode. In particular, the attenuation can be adjusted according to the difference in pixel degradation between the three primary colors. In this way, since the difference in pixel degradation among the three primary colors can be controlled with high accuracy and kept small, color misregistration can be effectively suppressed.

In addition to the above, the brightness adjustment unit
(A) This is an arithmetic unit for calculating the masking coefficient for multiplying the externally input video information and changing the color tone of the video indicated by the video information. In particular, the mode selection signal indicates the monochrome mode. A masking coefficient calculation unit for adjusting the masking coefficient based on the deterioration information; and
(B) a masking processing unit for multiplying the video information by a masking coefficient and setting the multiplication result as a video signal to the drive unit.
In addition, the brightness adjustment unit
(A) An arithmetic unit for calculating gamma correction parameters for video information input from the outside, especially when the mode selection signal indicates the monochrome mode, the gamma correction parameters are set for each pixel color based on the degradation information. A parameter calculation unit for changing to; and
(B) a gamma correction unit for executing gamma correction on the video information based on the gamma correction parameter calculated by the parameter calculation unit and setting the correction result as a video signal to the drive unit; May be.

In the monochrome mode, there are a case where monochrome video information is input from the outside to the control device and a case where color video information is input from the outside to the control device, and the control device converts the color video information into monochrome. In the latter case, the control device generally realizes monochromeization by masking processing or gamma correction.
In the control device according to the present invention, the luminance adjustment unit reflects pixel deterioration in monochrome by masking processing or gamma correction. Thereby, the luminance in the monochrome mode is lowered as the color of the pixel is severely deteriorated, and the deterioration of the pixel for the color can be suppressed.

Here, the masking processing for color video information means that the color tone of the color video information depends on the color characteristics of the display panel so that the original color tone of the video indicated by the color video information is reproduced well by the display panel. This is the process to correct. Specifically, for each set of pixels of the three primary colors, the luminance combination Li (i = R, G, B) specified by the color video information is a predetermined 3 × 3 matrix (masking coefficient) Mij (i, j = R, G, B) and converted to a new combination Ni: Ni = Σj Mij × Lj (i = R, G, B).
Monochrome by masking processing is realized, for example, by adjusting the masking coefficient Mij so that the luminance ratio NR: NG: NB after conversion is kept substantially constant for the entire set of pixels of the three primary colors.

  Gamma correction for video information refers to the relationship between the luminance indicated by the input signal in the video information creation system and the luminance indicated by the video information (hereinafter referred to as luminance characteristics of the video information creation system), and to the drive unit. Based on the relationship between the luminance indicated by the video signal and the actual luminance on the display panel (hereinafter referred to as the luminance characteristic of the display panel), the luminance indicated by the input signal in the video information creation system and the display panel Is a process for linearly correcting the relationship with the actual luminance. The luminance characteristics of video information creation systems are generally non-linear and are expressed by the following equation: L ≒ LI ^ γI. Here, it is assumed that the luminance indicated by the input signal in the video information creation system is LI, the luminance indicated by the video information is L, and the gamma coefficient of the video information creation system is γI. On the other hand, the luminance characteristic of the display panel is also generally non-linear and is expressed by the following formula: LO≈N ^ γO. Here, the luminance indicated by the video signal to the drive unit is N, the actual luminance on the display panel is LO, and the gamma coefficient of the display panel is γO. At that time, the above gamma correction unit converts the luminance L indicated by the video information into the luminance N indicated by the video signal to the driving unit based on the following equation: N≈L ^ (1 / (γI × γO)) . Thereby, the relationship between the luminance LI indicated by the input signal in the video information creation system and the actual luminance LO on the display panel is linearly corrected: LO≈LI.

  The gamma correction unit uses the function form of brightness conversion, that is, the function form of the relational expression N = f (L) between the brightness L indicated by the video information and the brightness N indicated by the video signal to the drive unit as a parameter for gamma correction. Determine based on. Particularly in the EL display, the luminance characteristics of the display panel are greatly different for each of the three primary colors. For example, the above gamma coefficient γO differs greatly for each of the three primary colors. The parameter calculation unit changes a gamma correction parameter for each of the three primary colors, and the gamma correction unit performs the above-described luminance conversion in a different function form for each of the three primary colors. Thereby, in the color mode, the accuracy of the above gamma correction is maintained high. On the other hand, in the monochrome mode, for example, with respect to the luminance Ni (i = R, G, B) of each of the three primary colors indicated by the video signal to the drive unit, the luminance ratio NR: NG: NB is substantially equal for the entire set of pixels of the three primary colors. Kept constant. That is, monochrome conversion by gamma correction is realized.

  The above-described luminance adjusting unit according to the present invention adjusts the luminance ratio NR: NG: NB after conversion, for example, for monochrome processing by masking processing or gamma correction, and lowers the ratio as the color of the pixel is severely deteriorated. Thereby, the luminance in the monochrome mode is lowered as the color of the pixel is severely deteriorated, and the deterioration of the pixel for the color can be suppressed.

The method of suppressing color misregistration of a full color EL display with a monochrome mode according to the present invention
(A) receiving a mode selection signal from the outside;
(B) Step of inputting video information from outside;
(C) The step of converting the video information into a video signal to the drive unit, particularly when the mode selection signal indicates the monochrome mode, the pixels of the three primary colors juxtaposed on the display panel are designated by the video information. Reducing the luminance based on the deterioration information for the color of the pixel and setting it as a video signal to the drive unit;
(D) supplying a driving current corresponding to the luminance of the pixel specified by the video signal to the pixel by the driving unit; and
(E) evaluating pixel degradation for each of the three primary colors based on the video signal, and determining the evaluation value as degradation information for the color.

In the above color misregistration suppression method according to the present invention, the deterioration of the pixels on the display panel is monitored for each of the three primary colors. When the monochrome mode is selected for a full-color EL display, the luminance of the pixel to be designated for the drive unit decreases with the degradation of the pixel evaluated for the color of that pixel. Thereby, the luminance in the monochrome mode decreases as the color of the pixel is severely deteriorated, so that the deterioration of the pixel for the color is suppressed.
The difference in pixel degradation between the three primary colors is magnified in the color mode. However, it is reduced in the monochrome mode. Thus, in the above-described color misregistration suppression method according to the present invention, an increase in the difference in deterioration of the pixels among the three primary colors can be suppressed over a long period of time, and a good white balance can be maintained. That is, color misregistration is effectively suppressed over a long period of time.

In the color misregistration suppression method according to the present invention described above, the step of determining the 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 value corresponding to the cumulative energization time or energized electricity is obtained from a table or an approximate expression showing energization time-luminance characteristics or energized electricity quantity-luminance characteristics for each pixel color, and the value is used as deterioration information for that color. Determining sub-steps. Further, 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 dependency of the deterioration of the pixel on the energization time, energized electricity amount, and temperature is measured in advance for each of the three primary colors, and is preferably stored as an energization time-luminance characteristic table or an energized electricity amount-luminance characteristic table similar to the above. The Instead of these characteristic tables, approximate expressions indicating the above dependencies may be stored.
From these characteristic tables or approximate expressions, a value corresponding to the cumulative energization time or energization amount of electricity for each pixel color is determined as deterioration information for that color. The deterioration information is represented by, for example, the attenuation rate of the luminance under a constant driving voltage with respect to the initial luminance, as described above. Thus, pixel degradation is evaluated for each of the three primary colors. The evaluation may be started when the difference in pixel degradation between the three primary colors is slight, especially when a full-color EL display is manufactured. As a result, the difference in pixel degradation among the three primary colors is kept small, so that the white balance is well maintained.

In the color misregistration suppressing method according to the present invention described above, the step of converting the video information into a video signal to the drive unit includes:
(A) A sub-step of selecting one or two of the three primary colors as the emission stop color based on the deterioration information for each of the three primary colors;
(B) a sub-step of changing the luminance designated by the video information to substantially zero for the pixel of the emission stop color and setting it as a video signal to the drive unit; and
(C) (a) When the mode selection signal indicates the color mode, video information input from the outside is selected as the video signal to the drive unit, and (b) when the mode selection signal indicates the monochrome mode, A sub-step of selecting a video signal obtained by converting the luminance of the pixel of the emission stop color from zero among the luminance of the pixel specified by the information as a video signal to the drive unit.
At that time, in the monochrome mode, the pixels of the emission stop color do not substantially emit light, and the deterioration is suppressed. Therefore, by setting a color whose pixel degradation is severe as the emission stop color, the difference in pixel degradation among the three primary colors is reduced in the monochrome mode. In this way, the difference in pixel degradation among the three primary colors can be kept small, and color misregistration can be effectively suppressed.

In the color misregistration suppression method according to the present invention described above, the step of converting the video information into a video signal to the driving unit is separate from the above.
(A) a sub-step for determining a luminance attenuation amount for each pixel color based on deterioration information for each of the three primary colors;
(B) a sub-step in which the luminance of the pixel specified by the video information is reduced by the attenuation amount for each pixel color and set as a video signal to the drive unit; and
(C) (a) When the mode selection signal indicates the color mode, the video information is selected as the video signal to the drive unit. (B) When the mode selection signal indicates the monochrome mode, it is specified by the video information. A sub-step of selecting a video signal in which the luminance of the pixel is reduced by the attenuation amount as a video signal to the drive unit.
At this time, by setting the luminance attenuation amount to be larger for a color with more severe pixel degradation, the difference in pixel degradation between the three primary colors is reduced in the monochrome mode. In particular, the attenuation can be adjusted according to the difference in pixel degradation between the three primary colors. In this way, since the difference in pixel degradation among the three primary colors can be controlled with high accuracy and kept small, color misregistration can be effectively suppressed.

In the color misregistration suppression method according to the present invention described above, the step of converting the video information into a video signal to the driving unit is further separate from the above.
(A) This is a sub-step for calculating a masking coefficient for multiplying the video information and changing the color tone of the video indicated by the video information, especially when the mode selection signal indicates the monochrome mode. A sub-step of adjusting the masking factor based on the degradation information; and
(B) a sub-step of multiplying the video information by a masking coefficient and setting the multiplication result as a video signal to the drive unit;
You may have. Other,
(A) This is a sub-step of calculating the gamma correction parameters for the above video information, especially when the mode selection signal indicates monochrome mode, and the gamma correction parameters are changed for each pixel color based on the degradation information for each of the three primary colors. Sub-steps; and
(B) a sub-step of executing gamma correction on the video information based on the calculated gamma correction parameter and setting the correction result as a video signal to the drive unit.

In the monochrome mode, there are a case where monochrome video information is input from the outside and a case where color video information is input from the outside and is converted into monochrome in the display. In the latter case, monochrome conversion is generally realized by masking processing or gamma correction. For example, the monochrome conversion is realized by setting the luminance ratio after conversion for the entire set of pixels of the three primary colors to be substantially constant.
In the above-described color misregistration suppression method according to the present invention, pixel deterioration is reflected in monochromeization by masking processing or gamma correction. For example, the luminance after the conversion is set to be lower as the color of the pixel is more deteriorated. Thereby, the luminance in the monochrome mode is lowered as the color of the pixel is severely deteriorated, and the deterioration of the pixel can be suppressed for the color.

In the full color EL display according to the present invention, the control device monitors the deterioration of each pixel on the display panel. When the monochrome mode is selected, the control device reduces the luminance of the pixel to be designated to the drive unit according to the deterioration of the pixel. Thereby, the luminance in the monochrome mode is lowered for a color with a more severe deterioration of the pixel, and the deterioration of the pixel of that color can be suppressed.
The difference in pixel degradation between the three primary colors is magnified in the color mode. However, it is reduced in the monochrome mode. Thus, the above-described control device according to the present invention can suppress an increase in the difference in deterioration of the pixels among the three primary colors over a long period of time and maintain a good white balance. That is, color misregistration can be effectively suppressed over a long period of time.

  In the control device according to the present invention, the deterioration evaluation unit may evaluate the deterioration of the pixel as follows. First, a table or an approximate expression indicating the energization time-luminance characteristic or energization electricity amount-luminance characteristic of the pixel is stored for each of the three primary colors. Next, the energization time or energized electricity amount of the entire pixels of the three primary colors is calculated based on the video signal to the drive unit, and the energized time or energized electricity amount is accumulated for each of the three primary colors from the time of manufacturing the full color EL display. Furthermore, a value corresponding to the cumulative energization time or energized electricity amount is obtained for each of the three primary colors from the above characteristic table or approximate expression, and the value is determined as deterioration information for each of the three primary colors. In this way, the deterioration evaluation unit can evaluate the deterioration of the pixel for each of the three primary colors. The evaluation may be started when the difference in pixel degradation between the three primary colors is slight, especially when a full-color EL display is manufactured. As a result, the difference in pixel degradation among the three primary colors can be kept small, so that the white balance is well maintained.

In the control device according to the present invention, the luminance adjustment unit may reduce the luminance of the pixel in the monochrome mode based on the deterioration information with respect to the color of the pixel as follows.
When the deterioration information, that is, the difference in attenuation rate among the three primary colors is larger than a predetermined threshold value, the light emission of the pixel of that color is substantially cut off in the monochrome mode for a color showing a large attenuation rate, that is, a color with severe pixel deterioration. In addition, the luminance in the monochrome mode may be greatly attenuated as the color of the pixel is more deteriorated. Thereby, in the monochrome mode, the difference in pixel degradation between the three primary colors is reduced. In this way, since the difference in pixel degradation among the three primary colors can be controlled and kept small, color shift can be effectively suppressed.

  In the control device according to the present invention, the luminance adjustment unit may convert the video information from the outside into a monochrome by masking processing or gamma correction. At that time, the luminance adjustment unit reflects the deterioration of the pixel in the monochrome conversion. Specifically, the luminance ratio after conversion may be adjusted so that the luminance of a color with severe pixel degradation is zero. In addition, the luminance ratio may be set to be smaller for a color with more severe pixel degradation according to the difference in degradation of the pixel among the three primary colors. In this way, it is possible to reduce the luminance in the monochrome mode as the color of the pixel is severely degraded, and to suppress the degradation of the pixel of that color. As a result, in the monochrome mode, the difference in pixel degradation between the three primary colors is reduced. In this way, the difference in pixel degradation among the three primary colors can be kept small, and color misregistration can be effectively suppressed.

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 control 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 (Alq3) 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 control 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 represented as, for example, 256-gradation digital information. 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. 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 control device 3A receives the 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 receives the video information N to the drive unit 2 as a video signal N. Convert to Here, 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 via a network, for example, via a cable or wirelessly.

  The video information L is transmitted in parallel for each of R, G, and B, like the video signal N to the drive unit 2. The video information L is, for example, a digital signal, and the luminances LR, LG, and LB of RGB are expressed as, for example, 256 gradation digital information. In addition, the video information 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 image indicated by the video information L may be color or monochrome. Here, when the video information L indicates a monochrome image, the ratio LR: LG: LB between the RGB luminances LR, LG, LB is maintained constant.
The transmission source device of the video information L sends a mode selection signal SEL to the control device 3A prior to transmission of the video information L or together with the video information L. When the video information L indicates a color image, the mode selection signal SEL instructs the control device 3A to select a color mode. When the video information L indicates a monochrome image, the mode selection signal SEL instructs the control device 3A to set the monochrome mode.

  The configuration of the control device 3A is roughly divided into a degradation evaluation unit and a luminance adjustment unit. The deterioration evaluation unit includes an energization management unit 32 and a deterioration information determination unit 33. The luminance adjustment unit includes a signal selection unit 31, a light emission stop color selection unit 34, and a light emission blocking unit 35.

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

  The energization management unit 32 monitors the video signal N to the drive unit 2. Thereby, the energization time and the energization amount of electricity for each of the RGB pixels of the display panel 1 are calculated for each frame of the video signal N, for example.

The energization time of the entire 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 entire R pixel in the frame is set to 0. On the other hand, when the luminance specified for any of the R pixels is greater than 0, the energization time of the entire 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 the entire G or B pixel in one frame is determined in the same manner.

The energized electricity amount of the entire R pixel in one frame is calculated as follows, for example. First, the maximum luminance value of R is detected from the video signal N of the frame, and the drive current corresponding to the maximum 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. Next, the product of the drive current and the energization time of the entire R pixel in the frame, that is, (frame period) × (duty ratio of the display panel 1) is calculated, and the product is calculated as R of the frame. It is determined as the energized electricity amount of the entire pixel.
The amount of electricity applied to the entire G or B pixel in one frame is determined in the same manner.

  Further, the energization management unit 32 accumulates the energization time and the energization amount of electricity for each of the R, G, and B pixels in one frame for all frames of the video signal N from the production of the full-color organic EL display. The energization management unit 32 updates the above cumulative value for each frame of the video signal N to the drive unit 2, for example.

For example, every time the number of frames of the video signal N to the drive unit 2 exceeds a predetermined number (for example, 2 million frames), the deterioration information determination unit 33 receives the energization time and the cumulative amount of energized electricity from the energization management unit 32. Further, deterioration information corresponding to each of the received cumulative values 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, approximate expressions indicating the dependence of deterioration on the energization time or the energized electricity may be stored. The deterioration information determination unit 33 determines a value corresponding to the energization time for each RGB or the cumulative value of the energized electricity amount as deterioration information for each RGB from the characteristic table or the approximate expression. Here, the deterioration information is represented, for example, as a ratio of luminance to initial luminance under a constant driving voltage (hereinafter referred to as attenuation factor).

The deterioration evaluation unit sends the deterioration information for each of RGB to the light emission stop color selection unit 34 in parallel.
The light emission stop color selection unit compares the deterioration information for each of RGB. For example, when the deterioration information is represented by the above-described attenuation rate, the light emission stop color selection unit 34 first obtains the difference between the minimum attenuation rate and the other two attenuation rates between RGB. When the difference exceeds a predetermined threshold (for example, 4%), the light emission stop color selecting unit 34 selects a color indicating the attenuation rate as the light emission stop color. In particular, when the difference between the second largest attenuation factor and the smallest attenuation factor exceeds the threshold, two colors, the color indicating the maximum attenuation factor and the color indicating the second largest attenuation factor, are selected as the emission stop colors. The

The light emission stop color selection unit 34 notifies the light emission cut-off unit 35 of the selected light emission stop color.
When notified of the light emission stop color, the light emission blocking unit 35 converts the luminance of the light emission stop color to substantially zero in the video information L input from the outside. In this way, when the difference in pixel degradation between RGB of the display panel 1 starts to lose the white balance, the luminance of one or two colors of RGB is changed to zero in the video signal M sent from the light emission blocking unit 35.

The light emission blocking unit 35 further sends the converted video signal M to the signal selection unit 31.
The signal selection unit 31 receives the video information L and the mode selection signal SEL from the outside, and receives the video signal M from the light emission blocking unit 35. When the mode selection signal SEL indicates the color mode, the signal selection unit 31 selects the video information L from the outside as the video signal N to the drive unit 2. When the mode selection signal SEL indicates the monochrome mode, the signal selection unit 31 selects the video signal M from the light emission blocking unit 35 as the video signal N to the drive unit 2.

FIG. 2 is a flowchart of the color misregistration suppression method according to Embodiment 1 of the present invention.
<Step S1>
Prior to receiving the video information L, the mode selection signal SEL is received.
<Step S2>
Subsequently, the video information L is received by the signal selection unit 31 and the light emission blocking unit 35.
<Step S3>
The light emission blocking unit 35 decodes the luminance of each pixel specified by the received video information L, and changes the luminance of the emission stop color to zero. The changed video signal M is sent to the signal selection unit 31.

<Step S4>
When the mode selection signal SEL indicates the color mode, the process proceeds to step S5. When the mode selection signal SEL indicates the monochrome mode, the process branches to step S6.
<Step S5>
In the color mode, the signal selection unit 31 selects the video information L directly input from the outside as the video signal N to the drive unit 2. Thereby, the video information L from the outside is sent to the drive unit 2 as it is.
<Step S6>
In the monochrome mode, the signal selection unit 31 selects the video signal M input from the light emission blocking unit 35 as the video signal N to the drive unit 2. Thereby, in the video signal N to the drive unit 2, the luminance of the emission stop color in the video information L from the outside is changed to zero.
<Step S7>
The driving unit 2 decodes the luminance of each pixel on the display panel 1 from the video signal N sent out by the control device 3A, and applies a driving voltage corresponding to the luminance to the pixel. As a result, the pixels on the display panel 1 emit light with the luminance specified by the video signal N.

<Step S8>
The deterioration evaluation unit evaluates the deterioration of each pixel on the display panel 1 based on the video signal N to the drive unit 2.
FIG. 3 is a flowchart of a deterioration evaluation method for each pixel on the display panel 1 by the deterioration evaluation unit.

Sub-step SS1: Based on the video signal N of one frame, the energization management unit 32 calculates the maximum value of the drive current for all the RGB pixels for that frame and the energization time for all of the RGB pixels in that frame. . Here, the drive current is obtained from the correspondence with the luminance specified by the video signal N.
The energization time of all the RGB pixels in the frame is calculated as follows. When the luminance specified by the video signal N of the frame is 0 for any pixel of the same color, the energization time of all the pixels of that color in that frame is set to 0. When the luminance specified for any of the pixels of the same color is greater than 0, the energization time of the entire pixel of that color in that frame is calculated by (frame period) × (duty ratio of display panel 1).

Sub-step SS2: The energization management unit 32 calculates the product of the maximum value of the drive current calculated in sub-step SS1 and the energization time as the energization electricity amount of each of the RGB pixels in the frame: (Energization electricity amount) ) = (Drive current) × (energization time).
Sub-step SS3: The energization management unit 32 accumulates the energization time calculated in sub-step SS1 and the energization electricity calculated in sub-step SS2 for each RGB from the time of manufacturing the full-color organic EL display, and the accumulated value for each of RGB Remember. The energization management unit 32 updates the above cumulative value for each frame of the video signal N to the drive unit 2.

Substep SS4: The frame is counted from the start of input of the video signal N to the drive unit 2. Until the number of frames exceeds a predetermined number (for example, 2 million frames), the process repeats the loop of sub-steps SS1 to SS3. When the number of frames exceeds the predetermined number, the process branches to substep SS5.
Substep SS5: The deterioration information determination unit 33 receives the energization time and the cumulative value of energized electricity from the energization management unit 32. Further, the deterioration information determination unit 33 determines deterioration information corresponding to each of the received cumulative values, that is, an attenuation rate, from the energization time-luminance characteristic table or the energized electricity amount-luminance characteristic table. In this way, deterioration information for each of RGB is sent in parallel to the light emission stop color selection unit.

<Step S9>
The light emission stop color selection unit compares the deterioration information, that is, the attenuation rate for each of RGB. When the difference between the minimum attenuation rate between RGB and the other two attenuation rates exceeds a predetermined threshold, the light emission stop color selection unit 34 selects a color indicating the attenuation rate as the light emission stop color.
Thereafter, the process returns to step S2.

  In Embodiment 1 of the present invention, as described above, when the deterioration information, that is, the difference in attenuation rate between RGB is larger than a predetermined threshold, the color of the pixel exhibiting a large attenuation rate, that is, the color with severe pixel deterioration becomes the emission stop color. Is set. Furthermore, the light emission of the pixel of the emission stop color is substantially blocked in the monochrome mode. Thereby, deterioration of the pixel is suppressed. As a result, in the monochrome mode, the difference in pixel degradation between the three primary colors is reduced. In this way, the difference in pixel degradation among the three primary colors can be kept small, and color misregistration can be effectively suppressed.

<< Embodiment 2 >>
FIG. 4 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 is different from that according to the first embodiment in the configuration of the control device 3B. For other configurations, the first embodiment and the second embodiment are common. Therefore, in FIG. 4, 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 control device 3B receives the 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 receives the video information N to the drive unit 2 as a video signal N. Convert to Here, 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 via a network, for example, via a cable or wirelessly.

  Video information L is transmitted in parallel for each RGB. The video information L is, for example, a digital signal, and the luminances LR, LG, and LB of RGB are expressed as, for example, 256 gradation digital information. In addition, the video information 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 image indicated by the video information L may be color or monochrome. Here, when the video information L indicates a monochrome image, the ratio LR: LG: LB between the RGB luminances LR, LG, LB is maintained constant.
The transmission source device of the video information L sends a mode selection signal SEL to the control device 3A prior to transmission of the video information L or together with the video information L. When the video information L indicates a color image, the mode selection signal SEL instructs the control device 3A to select a color mode. When the video information L indicates a monochrome image, the mode selection signal SEL instructs the control device 3A to set the monochrome mode.

  The configuration of the control device 3B is roughly divided into a degradation evaluation unit and a luminance adjustment unit. The deterioration evaluation unit includes an energization management unit 32 and a deterioration information determination unit 33. The luminance adjustment unit includes a signal selection unit 31, an attenuation amount determination unit 36, and three attenuators 37R, 37G, and 37B.

The deterioration evaluating unit evaluates the deterioration of the pixels of the display panel 1 for each RGB based on the video signal N to the driving unit 2, and sends the evaluation value to the attenuation determining unit 36 in parallel as deterioration information for each of RGB.
The attenuation amount determination unit 36 compares the deterioration information for each of RGB. For example, when the deterioration information is represented by the above-described attenuation rate, the attenuation amount determination unit 36 first obtains a difference between the minimum attenuation rate and the other two attenuation rates between RGB. Next, for two colors other than the color indicating the minimum attenuation rate, the luminance attenuation amount is determined according to the difference between the attenuation rate and the minimum attenuation rate. Here, the attenuation amount of the luminance is expressed by the same gradation as the luminance of the video information L, for example. Furthermore, the larger the difference in deterioration information, the larger the luminance attenuation amount is set. At that time, for example, when the difference in deterioration information reaches 10%, the difference in deterioration information and the attenuation amount in luminance are associated with each other so that the attenuation amount in luminance reaches 100%.

The attenuation amount determination unit 36 notifies the attenuation amounts determined for RGB respectively to the attenuators 37R, 37G, and 37B for RGB.
The attenuators 37R, 37G, and 37B reduce the luminance specified by the video information L input from the outside by the notified attenuation amount. Further, the video signal M thus converted is sent to the signal selection unit 31. Thus, when the difference in pixel degradation between RGB of the display panel 1 breaks the white balance, in the video signal M sent from the attenuators 37R, 37G, and 37B, two colors of RGB that have severe pixel degradation are included. The brightness is reduced. In particular, the attenuation amount of the luminance of the two colors is determined according to the difference in pixel degradation between the remaining one color.

FIG. 5 is a flowchart of the color misregistration suppressing method according to Embodiment 2 of the present invention. In FIG. 5, the same steps as those in the color misregistration suppression method according to the first embodiment are denoted by the same reference numerals as in FIG. Furthermore, the description of the similar steps is the same as that in the first embodiment.
<Step S31>
Each of the attenuators 37R, 37G, and 37B decodes the RGB luminances specified by the received video information L, and particularly reduces them by a predetermined attenuation amount. Thus, the changed video signal M is sent to the signal selection unit 31.

<Step S4>
When the mode selection signal SEL indicates the color mode, the process proceeds to step S5. When the mode selection signal SEL indicates the monochrome mode, the process branches to step S61.
<Step S61>
In the monochrome mode, the signal selection unit 31 selects the video signal M input from the attenuators 37R, 37G, and 37B as the video signal N to the drive unit 2. Thereby, the luminance specified by the video signal N to the drive unit 2 is reduced by a predetermined attenuation amount from the luminance specified by the video information L from the outside.

<Step S91>
First, the attenuation amount determination unit 36 compares the deterioration information, that is, attenuation rates of RGB, and obtains the difference between the minimum attenuation rate and the other two attenuation rates between RGB. Next, for two colors other than the color indicating the minimum attenuation rate, the luminance attenuation amount is determined according to the difference between the attenuation rate and the minimum attenuation rate. The determined luminance attenuation amounts for RGB are set in attenuators 37R, 37G, and 37B for RGB.
Thereafter, the process returns to step S2.

  In the second embodiment of the present invention, as described above, the luminance attenuation amount is set to be larger for the color where the pixel is more deteriorated between RGB. Thereby, in the monochrome mode, the difference in pixel degradation between RGB is reduced. In particular, the amount of attenuation is adjusted according to the difference in pixel degradation between RGB. In this way, the difference in pixel degradation between RGB can be controlled with high accuracy and kept small, so that color misregistration can be effectively suppressed.

<< Embodiment 3 >>
FIG. 6 is a block diagram showing a configuration of a full-color organic EL display according to Embodiment 3 of the present invention. This full-color organic EL display differs from that according to the first embodiment in the configuration of the control device 3C. For other configurations, the first embodiment and the third embodiment are common. Therefore, in FIG. 6, 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 control device 3C receives the 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 receives the video information N as a video signal N to the drive unit 2. Convert to In particular, when the monochrome mode is instructed from the transmission source device of the video information L, the control device 3C converts the video information L into monochrome.
Here, 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 via a network, for example, via a cable or wirelessly.

  Video information L is transmitted in parallel for each RGB. The video information L is, for example, a digital signal, and the luminances LR, LG, and LB of RGB are expressed as, for example, 256 gradation digital information. In addition, the video information 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.

  In the third embodiment of the present invention, unlike the first and second embodiments, only the case where the video information L indicates a color image is assumed. The device that is the transmission source of the video information L sends the mode selection signal SEL to the control device 3C prior to the transmission of the video information L or together with the video information L. When the video information L is displayed in full color on the display panel 1, the mode selection signal SEL instructs the control device 3C to set the color mode. When the video information L is displayed in monochrome on the display panel 1, the mode selection signal SEL instructs the control device 3C to set the monochrome mode.

  The configuration of the control device 3C is roughly divided into a deterioration evaluation unit and a luminance adjustment unit. The deterioration evaluation unit includes an energization management unit 32 and a deterioration information determination unit 33. The brightness adjustment unit includes a gamma correction unit 38A, a masking processing unit 39A, and a masking coefficient calculation unit 40A.

  The gamma correction unit 38A performs gamma correction on the video information L. In other words, the RGB luminances (represented by the same symbol L) designated by the video information L are converted into new luminance K. Thereby, the relationship between the luminance indicated by the input signal in the generation system of the video information L and the actual luminance on the display panel 1 is linearly corrected. Here, the gamma correction parameters are preferably set for each of RGB in accordance with the luminance characteristics of the generation system of the video information L and the luminance characteristics of the display panel 1.

  The masking processing unit 39A performs a masking process on the video signal K input from the gamma correction unit 38A. Specifically, for each set of RGB, the luminance combination Ki (i = R, G, B) is multiplied by a masking coefficient Mij (i, j = R, G, B), and converted to a new combination Ni. : Ni = Σj Mij × Kj (i = R, G, B). The luminance combination Ni (i = R, G, B) after conversion is sent to the drive unit 2 as a video signal N.

The masking coefficient calculation unit 40A receives the mode selection signal SEL from the transmission source device of the video information L.
When the mode selection signal SEL indicates the color mode, the masking coefficient calculation unit 40A calculates a full-color display masking coefficient and sets the masking processing unit 39A. Accordingly, the color tone of the video signal K after the gamma correction is corrected according to the color characteristics of the display panel 1 so that the original color tone of the color image indicated by the video information L is reproduced well on the display panel 1.

When the mode selection signal SEL indicates the monochrome mode, the masking coefficient calculation unit 40A calculates a monochrome display masking coefficient and sets the masking processing unit 39A. Thereby, the luminance ratio NR: NG: NB after conversion is kept substantially constant in the entire RGB group. That is, the video signal N to the drive unit 2 is converted to monochrome.
At that time, the masking coefficient calculation unit 40A particularly adjusts the luminance ratio NR: NG: NB after conversion in accordance with deterioration information for each of RGB, that is, the attenuation rate, and lowers the ratio as the color of the pixel is severely deteriorated.

  Specifically, the attenuation rates are first compared between RGB, and the difference between the minimum attenuation rate and the other two attenuation rates is obtained. When the difference exceeds a predetermined threshold (for example, 4%), the masking coefficient calculation unit 40A sets the luminance after conversion to 0 for the color indicating the attenuation rate. In particular, when the difference between the second largest attenuation factor and the smallest attenuation factor exceeds the threshold, the luminance after conversion for two colors, the color representing the largest attenuation factor and the color representing the second largest attenuation factor, is Set to 0. As a result, in the monochrome mode, the pixel of the RGB whose color is severely deteriorated does not emit light, and the deterioration of the pixel is suppressed. As a result, the difference in pixel degradation between RGB in the monochrome mode is reduced. In this way, since the difference in pixel degradation between RGB can be kept small, color shift can be effectively suppressed.

  In addition, the masking coefficient calculating unit 40A may determine the luminance after conversion for two colors other than the color indicating the minimum attenuation rate according to the difference between the attenuation rate and the minimum attenuation rate. In particular, the greater the difference from the minimum attenuation rate, the smaller the luminance after conversion of that color. Thereby, in the monochrome mode, the difference in pixel degradation between RGB is reduced. In this way, the difference in pixel degradation between RGB can be controlled with high accuracy and kept small, so that color misregistration can be effectively suppressed.

FIG. 7 is a flowchart of the color misregistration suppressing method according to Embodiment 3 of the present invention. In FIG. 7, the same steps as those in the color misregistration suppression method according to the first embodiment are denoted by the same reference numerals as in FIG. Furthermore, the description of the similar steps is the same as that in the first embodiment.
<Step S11>
Gamma correction is performed on the video information L.

<Step S12>
When the mode selection signal SEL indicates the color mode, the process proceeds to step S13. When the mode selection signal SEL indicates the monochrome mode, the process branches to step S14.
<Step S13>
In the color mode, the masking coefficient calculation unit 40A calculates a masking coefficient for full color display.
<Step S14>
In the monochrome mode, the masking coefficient calculation unit 40A first adjusts the converted luminance ratio NR: NG: NB based on the deterioration information for each of RGB. Next, the masking coefficient for monochrome display is calculated so that the luminance ratio after the conversion is kept constant for the entire RGB group.
<Step S15>
Using the masking coefficient calculated by the masking coefficient calculation unit 40A, the masking processing unit 39A performs a masking process on the video signal K after the gamma correction. The video signal N after the masking process is sent to the drive unit 2.

  In the third embodiment of the present invention, as described above, when the deterioration information, that is, the difference in attenuation rate between RGB is larger than a predetermined threshold value, light in the monochrome mode is emitted for a color that exhibits a large attenuation rate, that is, a color in which pixel deterioration is severe. Substantially blocked. In addition, the luminance in the monochrome mode may be set small according to the difference in pixel degradation between RGB. Thereby, in the monochrome mode, the deterioration of the pixel of the color is suppressed in the monochrome mode. As a result, the difference in pixel degradation between RGB in the monochrome mode is reduced. In this way, since the difference in pixel degradation between RGB can be kept small, color shift can be effectively suppressed.

<< Embodiment 4 >>
FIG. 8 is a block diagram showing a configuration of a full-color organic EL display according to Embodiment 4 of the present invention. This full-color organic EL display differs from that according to the third embodiment in the configuration of the control device 3D. For other configurations, the third embodiment and the fourth embodiment are common. Therefore, in FIG. 8, the same reference numerals as those in FIG. Furthermore, the description of these common components is the same as that in Embodiment 1 or Embodiment 3.

The control device 3D 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, for example, and sends the video information to the drive unit 2 as a video signal N. Convert to In particular, when the monochrome mode is instructed from the transmission source device of the video information L, the control device 3D converts the video information L into monochrome.
Here, 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 via a network, for example, via a cable or wirelessly.

  Video information L is transmitted in parallel for each RGB. Furthermore, the video information L is a digital signal, and the luminances LR, LG, and LB of RGB are expressed as, for example, 256 gradation digital information. In addition, the video information 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.

  In the fourth embodiment of the present invention, as in the third embodiment, only the case where the video information L indicates a color image is assumed. The device that is the transmission source of the video information L sends the mode selection signal SEL to the control device 3D prior to the transmission of the video information L or together with the video information L. When the video information L is displayed in full color on the display panel 1, the mode selection signal SEL instructs the control device 3D to select the color mode. When the video information L is displayed in monochrome, the mode selection signal SEL instructs the control device 3D to perform monochrome mode.

  The configuration of the control device 3D is roughly divided into a degradation evaluation unit and a luminance adjustment unit. The deterioration evaluation unit includes an energization management unit 32 and a deterioration information determination unit 33. The brightness adjustment unit includes a gamma correction unit 38B, a masking processing unit 39B, and a parameter calculation unit 40B.

The gamma correction unit 38B performs gamma correction on the video information L. That is, the luminance L of each of RGB designated by the video information L is converted into a new luminance K. The conversion formula is determined by the parameter γ of gamma correction. Here, the parameter γ for gamma correction is set for each RGB by the parameter calculation unit 40B in accordance with the luminance characteristics of the creation system of the video information L and the luminance characteristics of the display panel 1.
Here, the setting differs depending on the mode indicated by the mode selection signal SEL. In the color mode, the relationship between the luminance indicated by the input signal in the video information L creation system and the actual luminance on the display panel 1 is linearly corrected. On the other hand, in the monochrome mode, for example, with respect to the luminance Ki (i = R, G, B) for each of RGB after conversion, the luminance ratio KR: KG: KB is maintained substantially constant for the entire RGB pixel group. That is, monochrome conversion by gamma correction is realized.

Masking processor 39B operates as follows in accordance with control signal CTL from parameter calculator 40B.
When the control signal CTL instructs execution of masking processing, the masking processing unit 39B performs masking processing on the video signal K input from the gamma correction unit 38B. Specifically, for each set of RGB, the luminance combination Ki (i = R, G, B) is multiplied by a masking coefficient Mij (i, j = R, G, B), and converted to a new combination Ni. : Ni = Σj Mij × Lj (i = R, G, B). The luminance combination Ni (i = R, G, B) after conversion is sent to the drive unit 2 as a video signal N.

  When the control signal CTL instructs to stop the masking process, the masking processing unit 39B sends the video signal K input from the gamma correction unit 38B to the driving unit 2 as it is. In addition, the unit matrix δij (= 1 (i = j), = 0 (i) is used as the masking coefficient Mij (i, j = R, G, B) to the RGB luminance combination Ki (i = R, G, B). ≠ j)) and may be converted into substantially the same combination Ni: Ni = Σj δij × Kj = Ki (i = R, G, B). The luminance combination Ni (i = R, G, B) after conversion is sent to the drive unit 2 as a video signal N.

The parameter calculation unit 40B receives the mode selection signal SEL from the transmission source device of the video information L.
When the mode selection signal SEL indicates the color mode, the parameter calculation unit 40B calculates a gamma correction parameter γ for full color display and sets it for the gamma correction unit 38B. As a result, in the video signal K after gamma correction, the luminance gradation is changed from the luminance gradation in the video information L, and the luminance indicated by the input signal in the generation system of the video information L and the actual luminance on the display panel 1 are changed. The relationship with luminance is corrected linearly. As a result, the original luminance gradation indicated by the input signal in the video information L creation system is reproduced well on the display panel 1.
The parameter calculation unit 40B further instructs the masking processing unit 39B to execute the masking process by the control signal CTL. As a result, the color tone indicated by the video signal K after gamma correction is corrected according to the color characteristics of the display panel 1, and the original color tone of the color image indicated by the input signal in the video information L creation system is displayed on the display panel 1. Is reproduced well.

When the mode selection signal SEL indicates the monochrome mode, the parameter calculation unit 40B calculates the gamma correction parameter γ for monochrome display and sets it for the gamma correction unit 38B. Thereby, the luminance ratio KR: KG: KB after conversion is maintained substantially constant in the entire RGB pixel set.
The parameter calculation unit 40B further instructs the masking processing unit 39B to stop the masking process by the control signal CTL. Thereby, the video signal K after the gamma correction is sent to the drive unit 2 as it is. In this way, the video signal N to the drive unit 2 is monochromeized.

  The parameter calculation unit 40B adjusts the converted luminance ratio KR: KG: KB according to the deterioration information, that is, the attenuation rate for each of RGB, and reduces the ratio of the color with more severe pixel deterioration during monochrome processing.

Specific processing is the same as that of the third embodiment.
The parameter calculation unit 40B compares the attenuation rates between RGB and obtains the difference between the minimum attenuation rate and the other two attenuation rates. When the difference exceeds a predetermined threshold (for example, 4%), the parameter calculation unit 40B sets the luminance after conversion to 0 for the color indicating the attenuation rate. In particular, when the difference between the second largest attenuation factor and the smallest attenuation factor exceeds the threshold, the luminance after conversion is zero for two colors, the color representing the largest attenuation factor and the color representing the second largest attenuation factor. Set to As a result, in the monochrome mode, a pixel of a pixel whose RGB is severely degraded does not emit light, and the degradation of the pixel is suppressed. As a result, the difference in pixel degradation between RGB in the monochrome mode is reduced. In this way, since the difference in pixel degradation between RGB can be kept small, color shift can be effectively suppressed.

  In addition, the parameter calculation unit 40B may determine the luminance after conversion for two colors other than the color indicating the minimum attenuation rate according to the difference between the attenuation rate and the minimum attenuation rate. In particular, the greater the difference from the minimum attenuation rate, the smaller the luminance after the color conversion. Thereby, in the monochrome mode, the difference in pixel degradation between RGB is reduced. In this way, the difference in pixel degradation between RGB can be controlled with high accuracy and kept small, so that color misregistration can be effectively suppressed.

FIG. 9 is a flowchart of the color misregistration suppressing method according to Embodiment 4 of the present invention. In FIG. 9, the same steps as those in the color misregistration suppression method according to the third embodiment are denoted by the same reference numerals as in FIG. Further, the description of the similar steps is the same as that in Embodiment 3.
<Step S21>
When the mode selection signal SEL indicates the color mode, the process proceeds to step S22. When the mode selection signal SEL indicates the monochrome mode, the process branches to step S24.

<Step S22>
In the color mode, the parameter calculation unit 40B calculates a gamma correction parameter γ for full-color display and sets it for the gamma correction unit 38B.
<Step S23>
The parameter calculation unit 40B further instructs the masking processing unit 39B to execute the masking process by the control signal CTL.

<Step S24>
In the monochrome mode, the parameter calculation unit 40B calculates a gamma correction parameter γ for monochrome display and sets it for the gamma correction unit 38B. In particular, the luminance ratio KR: KG: KB after conversion is adjusted according to the deterioration information for each of RGB, that is, the attenuation rate, and the ratio is lowered for a color with a severe pixel deterioration.
<Step S25>
The parameter calculation unit 40B further instructs the masking processing unit 39B to stop the masking process by the control signal CTL.

<Step S26>
The gamma correction unit 38B performs gamma correction on the video information L. Here, the gamma correction parameter γ set by the parameter calculation unit 40B is used.

<Step S27>
When the control signal CTL instructs execution of masking processing, the masking processing unit 39B performs masking processing on the video signal K input from the gamma correction unit 38B. Specifically, for each RGB group, the luminance combination Ki (i = R, G, B) is multiplied by a masking coefficient Mij (i, j = R, G, B), and the multiplication result Ni = Σj Mij × Lj (i = R, G, B) is sent to the drive unit 2 as a video signal N.
When the control signal CTL instructs to stop the masking process, the masking processing unit 39B sends the video signal K input from the gamma correction unit 38B as it is or multiplied by the unit matrix as a masking coefficient to the driving unit 2 as a video signal. Send as N.

  In Embodiment 4 of the present invention, as described above, when the deterioration information, that is, the difference in attenuation rate between RGB is larger than a predetermined threshold, a color showing a large attenuation rate, that is, a color with severe pixel deterioration, is displayed in the monochrome mode. The light emission of the pixel is substantially blocked. In addition, the luminance in the monochrome mode may be set small according to the difference in pixel degradation between RGB. Thereby, in the monochrome mode, the deterioration of the pixel of the color is suppressed in the monochrome mode. As a result, the difference in pixel degradation between RGB in the monochrome mode is reduced. In this way, since the difference in pixel degradation between RGB can be kept small, color shift can be effectively suppressed.

  The full color EL display according to the present invention reduces the luminance in the monochrome mode as the color of the pixel is more deteriorated, and suppresses the deterioration of the pixel of that color. As a result, it is possible to suppress an increase in the difference in deterioration of the pixels between the three primary colors over a long period of time and maintain a good white balance. That is, color misregistration can be effectively suppressed over a long period of time. Therefore, the full color EL display according to the present invention has high industrial applicability.

It is a block diagram which shows the structure of the full color organic electroluminescent display by Embodiment 1 of this invention. It is a flowchart of the color shift suppression method by Embodiment 1 of this invention. 4 is a flowchart of a deterioration evaluation method for each pixel on the display panel 1 according to the 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 flowchart of the color misregistration suppression method by Embodiment 2 of this invention. It is a block diagram which shows the structure of the full-color organic EL display by Embodiment 3 of this invention. It is a flowchart of the color misregistration suppression method by Embodiment 3 of this invention. It is a block diagram which shows the structure of the full color organic EL display by Embodiment 4 of this invention. It is a flowchart of the color misregistration suppression method by Embodiment 4 of this invention. It is a block diagram which shows the pixel deterioration compensation system of the conventional full color EL display.

Explanation of symbols

L Video information input from outside
M Video signal input from the light blocking unit 35
N Video signal to drive unit 2
SEL mode selection signal

Claims (13)

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 display controller for converting video information input from the outside into the video signal, which is mounted on a full-color EL display comprising:
A degradation evaluation unit for evaluating degradation of the pixel for each of the three primary colors based on the video signal and determining the evaluation value as degradation information for each of the three primary colors; and
When the mode selection signal is received from the outside and the mode selection signal indicates the monochrome mode, the luminance of the pixel specified by the video information is reduced based on the deterioration information for the color of the pixel, and the video signal is Brightness adjustment unit for setting;
A full-color EL display control device with a monochrome mode. 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 ,
Stores a table or approximate expression indicating energization time-luminance characteristics or energized electricity amount-luminance characteristics for each color of the pixel, and obtains a value corresponding to the energization time or the cumulative amount of energized electricity from the table or approximate expression, A deterioration information determining unit for determining the value as the deterioration information;
The full-color EL display control device with monochrome mode according to claim 1, comprising: The brightness adjusting unit is
A light emission stop color selection unit for selecting one or two of the three primary colors as a light emission stop color based on the deterioration information;
A light emission blocking unit for changing the luminance specified by the video information to substantially zero for the pixel of the emission stop color and setting it as a video signal to the drive unit; and
When the mode selection signal indicates a color mode, the video information is selected as a video signal to the driving unit, and when the mode selection signal indicates a monochrome mode, a video signal transmitted from the light emission blocking unit is selected. A signal selection unit for selecting as a video signal to the drive unit;
The full-color EL display control device with monochrome mode according to claim 1, comprising: The brightness adjusting unit is
An attenuation amount determining unit for determining an attenuation amount of luminance for each color of the pixel based on the deterioration information;
An attenuation unit for reducing the luminance specified for the pixel by the video information by the attenuation amount for each color of the pixel and setting as a video signal to the driving unit; and
When the mode selection signal indicates a color mode, the video information is selected as a video signal to the driving unit, and when the mode selection signal indicates a monochrome mode, the video signal sent from the attenuation unit is A signal selection unit for selecting as a video signal to the drive unit;
The full-color EL display control device with monochrome mode according to claim 1, comprising: The brightness adjusting unit is
A calculation unit for calculating a masking coefficient for multiplying the video information and changing a color tone of the video indicated by the video information, and particularly when the mode selection signal indicates a monochrome mode; A masking coefficient calculating unit for adjusting the masking coefficient based on:
A masking processing unit for multiplying the video information by the masking coefficient and setting the multiplication result as a video signal to the drive unit;
The full-color EL display control device with monochrome mode according to claim 1, comprising: The brightness adjusting unit is
A calculation unit for calculating a gamma correction parameter for the video information, and in particular, a parameter for changing the parameter for each color of the pixel based on the deterioration information when the mode selection signal indicates a monochrome mode. A calculation unit; and
A gamma correction unit for performing gamma correction on the video information based on the parameter calculated by the parameter calculation unit and setting the correction result as a video signal to the drive unit;
The full-color EL display control device with monochrome mode 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 a luminance of the pixel designated by the video signal, and supplying a driving current corresponding to the luminance to the pixel; and
A display control device for converting video information input from the outside into the video signal; evaluating degradation of the pixel for each of the three primary colors based on the video signal, and using the evaluation value as degradation information for each of the three primary colors A deterioration evaluation unit for determining; when the mode selection signal is received from the outside and the mode selection signal indicates a monochrome mode, the luminance information of the pixel specified by the video information is the deterioration information for the color of the pixel; A full-color EL display control device with a monochrome mode, which includes:
A full-color EL display. Receiving a mode selection signal from the outside;
Inputting video information from outside;
A step of converting the video information into a video signal to the driving unit, and in particular, when the mode selection signal indicates a monochrome mode, luminance specified by the video information for pixels of three primary colors juxtaposed on a display panel , Based on deterioration information for the color of the pixel, and setting as the video signal;
Supplying a driving current corresponding to the luminance of the pixel specified by the video signal to the pixel by the driving unit; and
Evaluating the deterioration of the pixel for each of the three primary colors based on the video signal, and determining the evaluation value as the deterioration information for the color;
A method for suppressing color misregistration of a full color EL display with a monochrome mode. Determining the degradation information comprises:
A 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 the full-color EL display for each color of the pixel; and
A value corresponding to the total of the energization time or the energized electricity amount is obtained from a table or an approximate expression showing energization time-luminance characteristics or energized electricity amount-luminance characteristics for each color of the pixel, and the value is determined as the deterioration information. Substeps;
The color misregistration suppression method of the full color EL display with a monochrome mode of Claim 8 which has these. Converting the video information into a video signal to the drive unit;
A sub-step of selecting any one or two of the three primary colors as a light emission stop color based on the deterioration information;
A sub-step of changing the luminance specified by the video information to substantially zero for the pixel of the emission stop color and setting it as a video signal to the drive unit; and
When the mode selection signal indicates a color mode, the video information is selected as the video signal, and when the mode selection signal indicates a monochrome mode, the luminance of the pixel specified by the video information is A sub-step of selecting a video signal obtained by converting the luminance of a pixel of a light emission stop color to zero as a video signal to the drive unit;
The color misregistration suppression method of the full color EL display with a monochrome mode of Claim 8 which has these. Converting the video information into a video signal to the drive unit;
A sub-step of determining a luminance attenuation amount for each color of the pixel based on the deterioration information;
A sub-step of reducing the luminance of the pixel specified by the video information by the attenuation amount for each color of the pixel and setting as a video signal to the driving unit; and
When the mode selection signal indicates a color mode, the video information is selected as the video signal, and when the mode selection signal indicates a monochrome mode, the luminance of the pixel specified by the video information is the attenuation amount. A sub-step of selecting a video signal reduced by only a video signal to the driving unit;
The color misregistration suppression method of the full color EL display with a monochrome mode of Claim 8 which has these. Converting the video information into a video signal to the drive unit;
A sub-step of calculating a masking coefficient for multiplying the video information and changing a color tone of the video indicated by the video information, and based on the deterioration information, particularly when the mode selection signal indicates a monochrome mode. A sub-step of adjusting the masking factor; and
A sub-step of multiplying the video information by the masking coefficient and setting the multiplication result as a video signal to the driving unit;
The color misregistration suppression method of the full color EL display with a monochrome mode of Claim 8 which has these. Converting the video information into a video signal to the drive unit;
A sub-step of calculating a parameter of gamma correction for the video information, and in particular when the mode selection signal indicates a monochrome mode, the sub-step of changing the parameter for each color of the pixel based on the deterioration information; and
Performing a gamma correction on the video information based on the calculated parameter, and setting the correction result as a video signal to the driving unit;
The color misregistration suppression method of the full color EL display with a monochrome mode of Claim 8 which has these.

Images