JP2011013470A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem, wherein upon storing input data for each of all the pixels for correcting the luminance, the capacity of a memory required for storing the data becomes large.SOLUTION: A display device is provided which includes a light-emitting element 1 disposed in each pixel, a drive unit 2, and a correcting unit 3, and is capable of displaying an image in a display mode according to an input data. The correcting unit 3 corrects the input data by each pixel, by using a cumulative time of the lighting time in each display mode and an assumed image data in each display mode.

Description

  The present invention relates to a display device including a light emitting element.

  In recent years, self-luminous devices compatible with flat panels such as organic EL elements have attracted attention, and it is known that the luminance of organic EL elements is reduced by emitting light.

  In a display in which a plurality of pixels are arranged in a matrix, for example, when a white fixed pattern is displayed on a black background, the black portion is not lit because it is not lit, but the white portion has lower luminance. At this time, the portion where the luminance is reduced is recognized as burn-in, and the image quality is significantly deteriorated. In particular, when used as a monitor of a digital camera, a fixed pattern such as an icon or text indicating shooting conditions is displayed, and burn-in is likely to occur. As a technique for compensating for the change in luminance of such an organic EL element, there is a technique disclosed in Patent Document 1.

Japanese Patent No. 3933485

  However, in Patent Document 1, input data for each pixel of an organic EL element is integrated at a constant period, and corresponding pixel data is obtained according to a value obtained by subtracting the integration time of each pixel from the maximum integration value of all pixels. With this correction, the decrease in luminance of each organic EL element is corrected in pixel units. For this reason, when the input data is stored for every pixel, the image data is accumulated for each pixel. Therefore, there is a problem that the larger the number of pixels, the larger the memory capacity necessary for storing data, and the higher the cost for correction.

  In order to solve the above problems, the present invention relates to a light emitting element arranged in a pixel, a driving unit that supplies current or voltage to the light emitting element, input data is corrected, and corrected data is supplied to the driving unit. A correction unit that supplies the correction unit, the correction unit using the accumulated time of the lighting time for each display mode and the image data assumed as the input data for each display mode A display device characterized by correcting input data for each pixel is provided.

  According to the present invention, since it is sufficient to hold the accumulated time of the lighting time for each display mode, the required memory capacity can be greatly reduced.

It is the schematic of the display apparatus of this invention. It is a figure which shows the time-dependent change of the brightness | luminance in a light emitting element. It is a figure explaining the weighted average of image data. It is a figure explaining a filter process. It is a figure explaining a filter process.

  FIG. 1 is a diagram showing a display device of the present invention.

  The display device of FIG. 1 includes a light emitting element 1, a driving unit 2 that supplies current or voltage to the light emitting element 1, and a correcting unit 3 that corrects input data and supplies corrected data to the driving unit 2. In the display device of the present invention, it is preferable to arrange one or more light emitting elements in one pixel and to arrange a plurality of pixels each including one or more light emitting elements in a matrix. At this time, a plurality of pixels arranged in a matrix form a display unit. The display device of the present invention can display an image in a display mode corresponding to input data. Here, the display mode will be described. When an image that the display device of the present invention has in advance is input as input data, an image that the display device of the present invention does not have in advance is input as input data. The display modes are different from each other. As an example of a display mode when an image that the display device of the present invention has in advance is input as input data, there is a menu screen mode for setting shooting conditions of a digital camera. On the other hand, as an example of a display mode when an image that the display device of the present invention does not have in advance is input as input data, there is a live view screen mode for displaying an image at the time of photographing with a digital camera. Note that the display mode in a case where an image that the display device of the present invention does not have in advance is input as input data can be set to another display mode depending on the type of input data. For example, both a case where a natural landscape image is used as input data and a case where a person image is used as input data may be displayed in one mode, or may be displayed in different display modes. Hereinafter, the case where there are two display modes will be described. However, in the display device of the present invention, the number of display modes may be two or more as long as it is two or more.

  The display device of the present invention corrects the luminance of the light emitting element 1 by correcting the input data for each pixel in the correction unit 3 and supplying the corrected data to the drive unit 2. The drive unit 2 is controlled so that a current or voltage corresponding to the corrected data is supplied to the light emitting element 1. In this control, a control unit may be provided. Correction of the luminance of the light emitting element 1 will be described with reference to FIG.

  When correcting the luminance of the light emitting element 1, the correction unit 3 uses the accumulated time data of the lighting time for each display mode and the image data assumed as input data for each display mode (hereinafter “assumed image data for each display mode”). The input data is corrected on a pixel-by-pixel basis.

  The accumulated lighting time for each display mode at a fixed time is calculated by an integrated time calculating means (not shown in FIG. 1). The integrated time calculating means is any means that can calculate the integrated time. May be. For example, an integration circuit may be used as a means for calculating the integration time. The means for supplying the accumulated time to the correction unit 3 (not shown in FIG. 1) may be in the display device or the apparatus in which the present display device is incorporated, and any means can be used as long as the accumulated time can be supplied to the correction unit 3. There may be. For example, the integration time may be supplied from the integration circuit to the correction unit 3.

  Display mode information required when calculating the accumulated time is provided in the display device by a display mode supply means (not shown in FIG. 1), a display mode analysis means (not shown in FIG. 1), and the like. You may acquire from any means. Further, it may be acquired from input data or may be acquired from means for controlling the display mode (not shown in FIG. 1).

  The assumed image data for each display mode is prepared in advance for each display mode in the display device or the device in which the display device is incorporated. Means for supplying assumed image data for each display mode to the correction unit 3 (not shown in FIG. 1) may be provided in the display device or a device in which the present display device is incorporated. Any means may be used as long as image data can be supplied. As the image data, it is preferable to use assumed image data in which the average of the integrated lighting luminance of each pixel is predicted for each display mode or data corresponding to the image. For example, in the menu screen mode of a digital camera, an average image of a plurality of menu screens may be used. In the live view screen mode of a digital camera, an average of integrated images of images of natural landscapes and people is taken. An image may be used. However, the present invention is not limited to these image data, and any assumed image data may be provided. In addition, a plurality of assumed image data may be prepared for one display mode, or the assumed image data used for correction may be selected from the plurality of assumed image data.

  For example, when the display device of the present invention is applied to a digital camera, the user of the digital camera may be able to select image data used for correction. Further, the image data to be used may be selected from a plurality of assumed image data according to the shooting mode of the digital camera. As a more specific example, when the digital camera is used in the portrait mode, the portrait image may be selected from a plurality of assumed image data including the portrait image.

  Further, the assumed image data for each display mode may be image data that has been subjected to image processing using a low-pass filter in advance. There is an effect of making it difficult to visually recognize erroneous correction when the accumulated image of the image actually displayed by the user is different from the assumed image.

  For example, if there is a region where a bright part and a dark part are close to each other in the assumed image, the bright part has a large deterioration, so the luminance correction amount is large, and the dark part has a small deterioration. The correction becomes smaller. When the accumulated image of the image actually displayed by the user is different from the assumed image and there is only a bright part and no dark part as in the white display on the whole, the dark part of the assumed image has a small amount of brightness correction and becomes dark. The burned image is displayed. At this time, if the boundary between the bright part and the dark part is blurred, the light and darkness after the correction becomes smooth, and the light and darkness becomes difficult to be visually recognized. As described above, by performing the processing by the low-pass filter and blurring the image, there is an effect of making it difficult to visually recognize the erroneous correction when the assumed image and the actually displayed image are different.

  Furthermore, low-pass filter processing may be performed on the correction data, and low-pass filter processing may be performed on the corrected data. The filter may be, for example, a 3 × 3 column two-dimensional moving average digital filter, or any other filter. Different filter processing may be performed for each display mode, or different filter processing may be performed on the assumed image data for each display mode.

  Here, the filtering process will be described. A case where certain image data is processed using a 3 × 3 two-dimensional moving average digital filter will be described with reference to FIG.

  Applying the coefficient matrix of the digital filter of FIG. 5B to the two-dimensional image data as shown in FIG. 5A, and multiplying each of the nine data by nine coefficients as shown in FIG. 5C. These sums are used as data after filtering. By calculating by moving the position where the matrix is multiplied, the unevenness of the two-dimensional image data becomes smooth as shown in FIG. 5D, and the image can be blurred.

  In the present invention, examples of a method for correcting input data for each pixel include the following methods. The method predicts the luminance deterioration amount (deterioration amount after a certain period of time) of the light emitting element 1 using the previously calculated integrated time data of the lighting time for each display mode and the assumed image data for each display mode. After that, the input data is corrected for each pixel based on the deterioration amount. The input data supply means (not shown in FIG. 1) to the correction unit 3 may be in the display device, and any means can be used as long as the input data can be supplied to the correction unit 3.

  In the following, a description will be given of prediction of the luminance deterioration amount of the light emitting element 1 and correction of input data based on the deterioration amount. For the sake of explanation, the two display modes will be referred to as “first display mode” and “second display mode”.

When predicting the amount of luminance deterioration of the light emitting element 1, first, an average image for predicting burn-in (hereinafter, also referred to as “burn-in expected average image”) is created. The means for creating the predicted burn-in average image (not shown in FIG. 1) may be in the display device, and any means can be used as long as the average image can be created. For example, a circuit that generates a weighted average image may be used as a means for creating a burn-in expected average image. For example, when the integrated lighting time of each display mode is the integrated lighting time of the first display mode = t ₁ hour and the integrated lighting time of the second display mode = t ₂ hours, the assumed image data for each display mode Are respectively weighted and averaged at a ratio of t ₁ : t ₂ . This image becomes an average image indicating the luminance of each pixel in order to predict burn-in, but is not limited to this. Arbitrary coefficients may be provided for weighting, such as increasing the ratio of any display mode.

  For example, when the display device of the present invention is applied to a digital camera, a user of the digital camera may be able to set a weighting coefficient.

Next, the luminance deterioration amount of the light emitting element 1 is calculated using the burn-in expected average image created earlier. The means for predicting the luminance deterioration amount of the light emitting element 1 (not shown in FIG. 1) may be in the display device, and any means can be used as long as the luminance deterioration amount of the light emitting element 1 can be calculated. Here, a case where an organic EL element is used as the light emitting element 1 will be described. According to the known technique described in Japanese Patent No. 3250561, it is known that in a sufficiently aged organic EL element, Equation 1 is established when the initial luminance L ₀ is 400 cd / m ² .

[Formula 1] L / L ₀ = exp (−7.54 × 10 ⁻⁵ × T)

In Equation 1, T is time, L is luminance at time T, and “7.54 × 10 ⁻⁵ ” is a constant (deterioration rate constant) k _i indicating the degree of luminance deterioration with time. Moreover, according to a known technique, it is known that the lifetime of the organic EL element is inversely proportional to the initial luminance. Using these relationships, the amount of luminance degradation in a sufficiently aged organic EL element can be predicted by Equation 2.

[Formula 2] L = L ₀ ′ × exp {−7.54 × 10 ⁻⁵ × (L ₀ ′ / 400) T}

In Equation 2, L ₀ ′ is the initial luminance. For example, in the case of initial luminance = 1000 cd / m ² and lighting time = 150 hours, the luminance after degradation becomes 972 cd / m ² and deteriorates by 2.8% as shown in the following formula. That is, the deterioration amount of the luminance of the organic EL element is 2.8%.
L ₁ = 1000 × exp (−7.54 × 10 ⁻⁵ × 1000/400 × 150) = 972

FIG. 2 shows the relationship between the time (x axis) at this time and the change in luminance L (y axis) with respect to the initial luminance L ₀ .

In a display device including a plurality of organic EL elements having different structures, a different deterioration rate constant k _i may be provided for each structure. For example, in a display device composed of organic EL elements having different colors such as red, green, and blue, the deterioration rate constant k _i may be different for each color.

  In the above description, the amount of deterioration in luminance is predicted for a sufficiently aged organic EL element, but it is not always necessary to perform aging.

  In the above description, the relationship between the luminance deterioration amount and the time is simulated by the deterioration model represented by Equation 1, but the light-emitting element 1 used in the display device of the present invention needs to conform to the deterioration model. Absent. In that case, when calculating the luminance deterioration amount of the light emitting element 1, the deterioration characteristic data of the light emitting element 1 to be used may be formulated into a mathematical formula. Further, the amount of deterioration may be predicted from a table of deterioration characteristic data of the light emitting element 1 to be used, or a plurality of tables may be prepared as tables of deterioration characteristic data of the light emitting element 1 to be used. At this time, the luminance deterioration amount of the light emitting element 1 is calculated based on the deterioration characteristic data of the light emitting element 1 to be used.

  As described above, light emission is performed using the previously calculated integration time of the lighting time for each display mode, the assumed image data for each display mode, the deterioration model represented by Equation 1, the deterioration characteristic data of the light emitting element 1, and the like. The amount of deterioration in luminance of the element 1 can be predicted. For example, the deterioration amount of the luminance of the light emitting element 1 when it is lit for a predetermined time in the burn-in expected average image is calculated.

  Subsequently, when correcting the input data based on the deterioration amount, the input data is corrected for each pixel based on the previously calculated luminance deterioration amount of the light emitting element 1. To be precise, based on the previously calculated luminance deterioration amount, the input data is corrected for each pixel so as to compensate for the deterioration amount, and correction data is created. The means for correcting the input data for each pixel based on the amount of deterioration (not shown in FIG. 1) may be in the display device, and any means that can correct the input data for each pixel based on the amount of deterioration. It may be. For example, a circuit that generates correction data may be used as means for correcting input data for each pixel.

  For example, considering how much the amount of current required to display a certain luminance can be corrected compared to the initial value to correct the luminance degradation, determine a correction coefficient and use the correction coefficient to determine the input data. to correct. Table 1 is a table of correction coefficients corresponding to the deterioration rate (deterioration amount) in a certain organic EL element. This table is stored in advance in the display device as data, and the luminance deterioration amount and correction of the light-emitting element 1 are corrected. The correction data may be created with reference to the coefficient data. The correction coefficient shown in Table 1 is an increase rate of the current amount.

  The present invention may be applied to a method of modulating the luminance of the light emitting element 1 by modulating the voltage. In that case, a table representing the required rate of increase of the voltage value corresponding to each deterioration amount and display luminance may be held as data.

  Further, the correction coefficient may be expressed not by an increase rate of the current value but by an increase amount, and the current required current amount may be calculated by adding to the initial value of the current and output to the light emitting element 1 may be controlled.

  Furthermore, instead of a correction coefficient composed of an increase amount of current, a display device in which a current increase amount added to the initial current, that is, a table of necessary currents corresponding to the deterioration amount of the light emitting element 1 and display luminance is previously displayed as data. The output current value may be determined according to the deterioration amount and the display luminance.

  Further, in a display device including a plurality of light emitting elements 1 having different structures, the correction coefficient may be changed for each structure. For example, in a display device including the light emitting elements 1 having different colors such as red, green, and blue, the correction amount determined by the deterioration amount and the luminance to be displayed may be different for each color.

  For example, when the display device of the present invention is applied to a digital camera, the correction coefficient may be changed at any time, or when the camera is started or stopped, or when the display mode is switched.

  In the above description, the case of correcting the deterioration amount of each pixel has been described. However, in the display device of the present invention, a difference in deterioration amount between pixels may be corrected, a reference pixel is set, and the reference pixel is compared with the reference pixel. The difference may be corrected.

  As described above, the correction data can be created by using the previously calculated luminance deterioration amount of the light emitting element 1, the correction coefficient, and the like.

  After the correction data is created, the correction data is supplied to the driving unit 2, and the driving unit 2 supplies a current or voltage corresponding to the correction data to the light emitting element 1 (in the case of supplying current, the light emitting element 1 is supplied). The product of the initial amount of current flowing and the correction coefficient is supplied to the light emitting element 1).

  The required memory capacity can be reduced by correcting the luminance of the light emitting element 1 by the above method.

  Examples of the display device of the present invention are shown below. Embodiments 1 and 2 are examples in which the display device of the present invention is applied to a digital camera.

[Example 1]
FIG. 1 shows a display device of this embodiment.

In the display device of this example, an organic EL element was used as the light emitting element 1. In addition, images were displayed in the following two display modes as display modes of the digital camera.
(1) Live view / review screen mode (2) Menu screen mode

  Here, the live view screen mode is a mode for displaying an image at the time of photographing, and the review screen mode is a mode for confirming a photographed image. On the other hand, the menu screen mode is a mode for displaying shooting condition settings.

  The correction of the luminance of the organic EL element will be described with reference to FIG.

  First, the integrated time of the lighting time in the display mode (the display mode (1) or (2) described above) corresponding to the input data was calculated.

  Next, using the accumulated lighting time data for each display mode and the assumed image data for each display mode, the amount of luminance degradation of the organic EL element after a lapse of a predetermined time was predicted. As an assumed image for each display mode prepared in advance, the image data of FIG. 3A is used for the display mode of (1), and the image data of FIG. 3B is used for the display mode of (2). did. The image data in FIG. 3A is an image obtained by averaging the accumulated images of 4000 images taken of natural scenery and people as the expected image for accumulated use in the display mode of (1). On the other hand, the image data in FIG. 3B is an average image of a plurality of menu screens as an expected image for cumulative use in the display mode of (2).

  When the previously calculated integrated lighting time for each display mode is (1) display mode integrated lighting time = 100 hours, (2) display mode integrated lighting time = 50 hours, the burn-in expected average image It was created. Specifically, an image (FIG. 3C) obtained by weighted averaging the image data of FIGS. 3A and 3B at a ratio of 100: 50 was created. The image data in FIG. 3C was an average image indicating the luminance of each pixel in order to predict burn-in. The average light emission luminance for each pixel is calculated from the image data of the average image and the gamma curve of the luminance of the light emitting element with respect to the image data, and the average light emission luminance for each pixel and the total integrated lighting time (sum of the total lighting time in both display modes) From Equation 2, the amount of luminance deterioration for each pixel was calculated.

Subsequently, a current amount correction coefficient is derived from the relationship between the previously calculated luminance deterioration amount of the organic EL element and the correction coefficient with respect to the deterioration amount of [Table 1], and the current amount correction coefficient and the gamma curve are used. The input data was corrected for each pixel. For example, when an image has an image data of 49, a correction coefficient of 1.05, and a luminance gamma curve of the light emitting element of 2.2, the correction data is 49 × (1.05) ^{(1 / 2.2)} = 50. Thereafter, correction data was supplied to the drive unit 2, and a current or voltage corresponding to the correction data was supplied from the drive unit 2 to the organic EL element.

  By implementing as described above, the required memory capacity could be reduced.

[Example 2]
The display device of the present embodiment is the same as that shown in FIG. 1 except that a filter is used when creating a burn-in expected average image.

  The correction of the luminance of the organic EL element will be described with reference to FIG.

  First, in the same manner as in Example 1, the integrated time of the lighting time in the display mode (the display mode (1) or (2) described above) corresponding to the input data was calculated.

  Next, each of the image data for each display mode (FIG. 3A and FIG. 3B) was filtered with a two-dimensional moving average digital filter of 5 rows × 5 columns shown in FIG. 4A. Similarly to Example 1, an image obtained by weighted averaging the image data at a ratio of 100: 50 was created. The image is the image shown in FIG. The filter processing using the 5 × 5 2D moving average digital filter was performed in the same manner as the filtering using the 3 × 3 2D moving average digital filter shown in FIG. In FIG. 5C, processing is performed using nine data, but in the present embodiment, processing was performed in the same manner as FIG. 5C using 25 data. The image data in FIG. 4B was an average image indicating the luminance of each pixel in order to predict burn-in.

  Next, in the same manner as in Example 1, the luminance deterioration amount was calculated, and the input data was corrected for each pixel.

  Subsequently, similarly to Example 1, correction data was supplied to the drive unit 2, and a current or voltage corresponding to the correction data was supplied from the drive unit 2 to the organic EL element.

  By carrying out as described above, the required memory capacity could be reduced as in the first embodiment.

  1: Light emitting element, 2: Drive unit, 3: Correction unit

Claims (7)

A light emitting element disposed in the pixel;
A drive unit for supplying current or voltage to the light emitting element;
A correction unit that corrects input data and supplies corrected data to the drive unit,
The correction unit corrects the input data for each pixel using an accumulated time of lighting time for each display mode and image data assumed as the input data for each display mode. apparatus.   The correction unit predicts a luminance deterioration amount of the light emitting element using the integration time and the image data, and corrects the input data based on the deterioration amount. Display device.   The display device according to claim 2, wherein the luminance deterioration amount of the light emitting element is a value based on deterioration characteristic data of the light emitting element.   The display device according to claim 2 or 3, wherein the corrected data corrected based on the deterioration amount is a value based on a correction coefficient corresponding to the deterioration amount.   The display device according to claim 1, wherein the image data is data obtained by filtering image data assumed as the input data for each display mode.   The display device according to claim 1, wherein the light emitting element is an organic EL element.   A digital camera in which the display device according to claim 1 is incorporated.

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