JP6548412B2 - Correction value generation device and correction value generation method - Google Patents

Description

  The present invention relates to a correction value generation device and a correction value generation method.

  A display element (pixel circuit) of an active matrix organic EL display device includes an organic EL element and a thin film transistor (TFT). Then, by controlling the voltage applied to the display element, the current flowing to the organic EL element is controlled, and the light emission luminance of the organic EL element is controlled. FIG. 8 is a diagram showing an example of the relationship between the voltage (input voltage) input to the display element and the light emission luminance of the display element. FIG. 8 also shows a circuit diagram of the display element. The light emission amount of the organic EL element is approximately proportional to the current flowing through the organic EL element. Therefore, the relationship between the input voltage and the light emission luminance approximates to the V-I characteristic of the TFT. Specifically, as shown in FIG. 8, the light emission luminance of the display element rises from the vicinity of the threshold voltage Vth of the TFT. Therefore, when the electrical characteristics (threshold voltage Vth or the like) of the TFTs vary among the display elements, the relationship between the input voltage and the light emission luminance varies among the display elements, causing uneven brightness in the display image (image displayed on the screen). Variations in the characteristics of the display element, such as the electrical characteristics of the TFT, are caused by, for example, manufacturing problems of the display element. In addition, the characteristics of the display element change due to a change in temperature around the display element and aging deterioration of the display element. Therefore, the variation in the characteristics of the display element is also caused by the change in the temperature around the display element and the aged deterioration of the display element.

The prior art for solving the said subject is indicated by patent documents 1-3, for example.
Patent Document 1 discloses a technique of providing a display element (pixel circuit) with a bootstrap function and a Vth cancel function, and correcting the V-I characteristic of the TFT in a circuit before the light emission period of the display element.
Patent Document 2 prepares in advance a gain correction value and an offset correction value for reducing variations in the threshold voltage Vth of the TFT and variations in the inclination of the V-I characteristic of the TFT, and uses these correction values to calculate the luminance of the image data. A technique for correcting the
In Patent Document 3, a uniform image is displayed on the screen to measure the light output level at a plurality of positions on the screen, and the unevenness of the screen is reduced based on the measurement result and the input / output characteristics of the display device. A technique is disclosed for generating correction data for

  As shown in FIG. 8, the V-I characteristic of the TFT for supplying current to the organic EL element changes at the threshold voltage Vth. Then, in the VI characteristic in the range (subthreshold region) of the input voltage less than the threshold voltage Vth, the current changes exponentially with the input voltage. Therefore, in the range of the input voltage less than the threshold voltage Vth, it is difficult to control the current accurately, and uneven brightness occurs when displaying a very low luminance in which the input voltage is less than the threshold voltage Vth.

  However, the techniques of Patent Documents 1 and 2 described above can correct the V-I characteristic in the range of the input voltage higher than the threshold voltage Vth, but correct the V-I characteristic in the range of the input voltage lower than the threshold voltage Can not do it. That is, with the techniques of Patent Literatures 1 and 2, it is not possible to reduce the luminance unevenness that occurs when displaying very low luminance.

  Further, with the technique of Patent Document 3 described above, it is not possible to generate a highly accurate correction value (a correction value for reducing luminance unevenness with high accuracy) for very low luminance where the input voltage is less than the threshold voltage Vth. is there. For example, in the case where there is a display element having a large variation in emission luminance of the display element and not emitting light at all, the characteristic of the display element can not be estimated from the measured value of the display luminance (luminance on the screen). You can not generate a value.

JP 2005-345722 A JP, 2005-284172, A JP 2001-209358 A

  An object of the present invention is to provide a technology capable of more reliably generating a correction value that reduces luminance unevenness of a display image with high accuracy.

The first aspect of the present invention is
An image is an apparatus having a plurality of display elements that emit light when a voltage is applied, and an apparatus that displays an image on a screen by applying a voltage according to the gradation value of image data to each display element. as measure of the brightness on the screen of the display device approaches the target value, a correction value generation unit for generating a correction value for correcting the tone values of the image data,
Acquisition means for acquiring a measured value of luminance on the screen;
Generation means for generating a correction value using the measurement value acquired by the acquisition means;
Have
The generation means is
If the first measurement value that corresponds to the first gradation value is a gradation value corresponding to the reference value or less of the voltage of the threshold voltage of the display element is equal to or larger than the first threshold, the first gradation value a correction value for correcting generated using the previous SL first measurement,
When the first measured value is less than the first threshold , a second floor having a tone value corresponding to a voltage equal to or less than the reference value and a tone value greater than the first tone value and it has use a second measurement value that corresponds to the tone value is a correction value generation device and generates a correction value for correcting the first gradation value.

The second aspect of the present invention is
An image is an apparatus having a plurality of display elements that emit light when a voltage is applied, and an apparatus that displays an image on a screen by applying a voltage according to the gradation value of image data to each display element. as measure of the brightness on the screen of the display device approaches the target value, a correction value generation process of generating a correction value for correcting the tone values of the image data,
An acquisition step of acquiring a measured value of luminance on the screen;
Generating the correction value using the measurement value acquired in the acquisition step;
Have
In the generation step,
If the first measurement value that corresponds to the first gradation value is a gradation value corresponding to the reference value or less of the voltage of the threshold voltage of the display element is equal to or larger than the first threshold, the first gradation value Generating a correction value to be corrected using the first measurement value;
When the first measured value is less than the first threshold , a second floor having a tone value corresponding to a voltage equal to or less than the reference value and a tone value greater than the first tone value and it has use a second measurement value that corresponds to the tone value, a correction value generating method characterized by generating a correction value for correcting the first gradation value.

  A third aspect of the present invention is a program causing a computer to execute the steps of the correction value generation method described above.

  According to the present invention, it is possible to more reliably generate a correction value that reduces luminance unevenness of a display image with high accuracy.

A figure showing an example of composition of an image display system concerning Example 1 The figure which shows an example of the input-output characteristic of the display element which concerns on Example 1. FIG. 6 is a diagram showing an example of the processing flow of the correction value generation unit according to the first embodiment FIG. 6 is a diagram showing an example of a method of generating a correction value according to the first embodiment. FIG. 6 is a diagram showing an example of a method of interpolating correction values according to the first embodiment. The figure which shows an example of the processing flow of the image display system which concerns on Example 2. FIG. 7 is a diagram showing an example of a method of generating a correction value according to a second embodiment. A diagram showing an example of the relationship between the input voltage of the display element and the light emission luminance

Example 1
Hereinafter, a correction value generation device and a correction value generation method according to a first embodiment of the present invention will be described with reference to the drawings.

(Image display system)
First, the configuration of an image display system having the correction value generation device according to the present embodiment will be described. FIG. 1 is a block diagram showing an example of the configuration of an image display system according to the present embodiment. As shown in FIG. 1, the image display system according to the present embodiment includes an image display device 101, a measuring instrument 102, an image data output device 103, and a correction value generation device 104. Although FIG. 1 illustrates the image display device 101, the measuring instrument 102, the image data output device 103, and the correction value generation device 104 as devices independent of other devices, the present invention is not limited thereto. . Two or more of the image display device 101, the measuring instrument 102, the image data output device 103, and the correction value generation device 104 may be provided in one device.

  The image data output device 103 is a device that outputs image data. As the image data output device 103, for example, a personal computer (PC), a digital camera, a smartphone, various players (Blu-ray player etc.), various recorders (hard disk recorder, Blu-ray recorder etc.), etc. can be used.

  The image display device 101 displays an image based on the image data (input image data) input to the image display device 101 on the screen. In the present embodiment, the image data output from the image data output device 103 is input to the image display device 101. As the image display device 101, a self-luminous display device, a transmissive display device, or the like can be used. For example, as the image display device 101, various image display devices such as an organic EL display device, a plasma display device, a field emission display (FED) device, an active matrix liquid crystal display device, and the like can be used. In this embodiment, an example in which the image display device 101 is an active matrix organic EL display device will be described. In the active matrix organic EL display device, the display element includes an organic EL element and a thin film transistor (TFT).

  Within a very small gradation value range in which the input voltage applied to the display element is equal to or lower than the threshold voltage Vth of the TFT, the light emission luminance with respect to the input voltage changes exponentially, so the light emission luminance variation among the display elements increases. . FIG. 2 shows an example of input / output characteristics of a display element in a small range of gradation values (low gradation range). The horizontal axis in FIG. 2 indicates the gradation value that can be taken by the input image data, and the vertical axis in FIG. 2 indicates the light emission luminance of the display element. The broken line in FIG. 2 indicates the ideal input / output characteristics of the display element. In the present embodiment, the broken line in FIG. 2 is the input / output characteristic of the target display element. In FIG. 2, three solid lines sequentially indicate the input / output characteristics of a bright display element, the input / output characteristics of a dark display element, and the input / output characteristics of a very dark display element from the top. It can be understood from FIG. 2 that the smaller the gradation value of the input image data is, the larger the variation in emission luminance among the display elements is. Further, it can be understood from FIG. 2 that the smaller the gradation value of the input image data is, the larger the uneven brightness is in the display image (the image displayed on the screen).

  In FIG. 2, the gradation value D is a gradation value in which the variation of the light emission luminance is sufficiently small and the image quality deterioration (luminance unevenness) hardly occurs. The gradation value C is a gradation value in which the image quality is slightly deteriorated due to a slight variation in light emission luminance. The gradation value B is a gradation value (second gradation value) at which a large number of display elements emit light, although the variation in emission luminance is large. The gradation value A is a gradation value (first gradation value) in which there are display elements which do not emit light due to large variations in light emission luminance. The gradation value C and the gradation value D are larger than the gradation value corresponding to the voltage Vref, and the gradation value A and the gradation value B are smaller than the gradation value corresponding to the voltage Vref. The voltage Vref is a reference value of the threshold voltage Vth. The threshold voltage Vth varies among the display elements.

  Although the details will be described later, according to the present embodiment, it is possible to more reliably generate a correction value (correction data) that reduces luminance unevenness of a display image with high accuracy. Specifically, according to the conventional method, a correction value is generated that reduces uneven brightness of the display image with high accuracy with respect to the gradation value at which there is a display element that does not emit light, such as gradation value A in FIG. Can not do it. According to this embodiment, it is possible to generate a correction value that reduces luminance unevenness of a display image with high accuracy even for such a gradation value.

  In the present embodiment, although the gradation value A in FIG. 2 is the first gradation value and the gradation value B is the second gradation value, the present invention is not limited to this. The first tone value may be any value, and the second tone value may be any value as long as it is larger than the first tone value.

  The measuring device 102 measures the brightness on the screen of the image display device 101, and outputs the measured value of the brightness. In the present embodiment, the measuring instrument 102 measures the brightness in the measurement area for each of the plurality of measurement areas in the screen. Then, the measuring instrument 102 outputs the measured value of the luminance to the correction value generation device 104. By measuring the display luminance over the entire area of the screen, a measurement result representing the luminance unevenness of the display image can be obtained. As the measuring device 102, a still camera, a luminance meter, a video camera or the like can be used.

  The shape, size, and arrangement of the plurality of measurement areas are not particularly limited. For example, a plurality of areas respectively corresponding to a plurality of display elements may be used as a plurality of measurement areas, and the luminance on the screen may be measured for each of the plurality of display elements. As a measurement area, an area including two or more display elements may be used. A plurality of divided areas constituting an area of the screen may be used as a plurality of measurement areas. Multiple regions separated from one another may be used as multiple measurement regions. A plurality of areas arranged in a matrix may be used as a plurality of measurement areas. A plurality of areas arranged in a staggered manner may be used as a plurality of measurement areas. A triangular area, a square area, a pentagonal area, a circular area, etc. may be used as the measurement area.

  The correction value generation device 104 generates a correction value for correcting the tone value of the image data so that the measured value of the brightness on the screen of the image display device 101 approaches the target value. In the present embodiment, the target value of the measurement value is the light emission luminance indicated by the broken line in FIG. Then, the correction value generation device 104 outputs the generated correction value to the image display device 101.

(Correction value generation device)
Next, the configuration of the correction value generation device 104 will be described. As shown in FIG. 1, the correction value generation device 104 includes a control unit 121, a measurement value acquisition unit 122, and a correction value generation unit 123.

The control unit 121 controls the respective functional units of the correction value generation device 104, the image display device 101, the measuring instrument 102, and the image data output device 103. For example, the control unit 121 instructs the image data output device 103 to output image data having uniform gradation values in order to obtain a measurement result representing uneven brightness of a display image as a measurement result of the measuring instrument 102. Specifically, the output of image data of gradation value A, the output of image data of gradation value B, the output of image data of gradation value C, the output of image data of gradation value D, etc. in FIG. The image data output device 103 is instructed.

  The measurement value acquisition unit 122 acquires a measurement value of luminance on the screen of the image display device 101. In the present embodiment, the measurement value acquisition unit 122 acquires, for each of the plurality of measurement areas, the measurement value of the luminance in the measurement area from the measuring instrument 102. The measurement value acquisition unit 122 outputs the acquired measurement value to the correction value generation unit 123. In addition, the acquisition method of a measured value is not specifically limited. For example, the measuring device 102 may record the measured value on a recording medium (magnetic disk, optical disk, semiconductor memory, etc.), and the measured value acquisition unit 122 may read the measured value from the recording medium. The user of the correction value generation device 104 may input the measurement value to the correction value generation device 104.

  The correction value generation unit 123 generates a correction value using the measurement value acquired by the measurement value acquisition unit 122. Then, the correction value generation unit 123 outputs the generated correction value to the image display device 101. In this embodiment, the correction value generation unit 123 corrects, for each of the plurality of measurement areas, the gradation value of the image data to be displayed in the measurement area using the measurement value corresponding to the measurement area. Generate

(Correction value generator)
Next, the process of the correction value generation unit 123 will be described in detail. As described above, the variation in light emission luminance among the display elements is larger as the gradation value is smaller. Therefore, for the smallest possible tone value, it is desirable to generate a correction value that corrects the tone value with high accuracy. However, in the conventional method, it is difficult to generate a correction value that corrects small gradation values with high accuracy. For example, when the gradation value is small, not only the variation of the light emission luminance is large but also the light emission luminance is extremely lower than the target value or the display element does not emit light, so that the correction value with high correction accuracy is generated. It is difficult. Therefore, in the present embodiment, the correction value generation unit 123 not only measures the measurement value corresponding to the first gradation value (the gradation value A), but also the second gradation value (the gradation at which the majority of display elements emit light). The measured value corresponding to the value B) is further used to generate a correction value for correcting the first tone value. Hereinafter, the measurement value corresponding to the first gradation value is referred to as “first measurement value”, and the measurement value corresponding to the second gradation value is referred to as “second measurement value”.

  Hereinafter, an example of the process flow of the correction value generation unit 123 will be described using FIG. 3. FIG. 3 is a flowchart showing an example of the processing flow of the correction value generation unit 123.

  First, the correction value generation unit 123 compares the first measurement value with the first threshold (S101). If the first measurement value is equal to or greater than the first threshold value, it is considered that the measurement accuracy of the first measurement value is high, and a correction value having high correction accuracy can be generated using only the first measurement value. On the other hand, if the first measurement value is less than the first threshold, the measurement accuracy of the first measurement value is low, and if only the first measurement value is used, a correction value with high correction accuracy can not be generated. Conceivable. Therefore, when the first measurement value is equal to or greater than the first threshold value, the process proceeds to S102, and when the first measurement value is less than the first threshold value, the process proceeds to S103. Thereby, when the first measurement value is equal to or greater than the first threshold value, the correction value of the first tone value is generated using the first measurement value. Then, when the first measurement value is less than the first threshold value, the correction value of the first tone value is generated using at least the second measurement value. By using at least the second measurement value when the first measurement value is less than the first threshold value, it is possible to generate a correction value with high correction accuracy even in such a case.

Note that the first threshold may be a fixed value predetermined by the manufacturer or the like, or may be a value changeable by the user. The first threshold can be determined based on, for example, spatial resolution or level resolution of luminance unevenness measurement, a curve shape of input / output characteristics of a display element, or the like. It is preferable to use a value of 20 to 60% of the target value of the first measurement value as the first threshold. In the present embodiment, the target value of the first measurement value is the light emission luminance indicated by the broken line in FIG. 2 and is the light emission luminance corresponding to the first gradation value.

  In S102, the correction value generation unit 123 compares the first measurement value with a second threshold that is larger than the first threshold. The second threshold is a threshold for determining whether the measurement area is a bright area. In the present embodiment, the target value of the first measurement value is used as the second threshold. If the first measurement value is equal to or greater than the second threshold value, the process proceeds to S104. If the first measurement value is less than the second threshold value, the process proceeds to S105. Specifically, if the first measured value is equal to or greater than the second threshold, the process of S104 is performed, and if the first measured value is equal to or greater than the first threshold and less than the second threshold, S105. Processing is performed. Note that the second threshold may be a fixed value predetermined by a manufacturer or the like, or may be a value changeable by the user. The second threshold may be larger or smaller than the target value of the first measurement value.

  When the first measurement value is equal to or greater than the first threshold value, a third gradation value that is a gradation value at which the target value of the first measurement value is obtained as the measurement value of the measuring device 102 using the first measurement value. Can be estimated. Here, it is assumed that a function representing the correspondence between the gradation value and the target value (the target value of the measured value) is determined in advance. In this case, the function may be changed so that the first measurement value is associated with the first tone value. As the change of the function, for example, rotation, extension, shift, etc. of the curve indicated by the function are performed. Then, the tone value corresponding to the target value of the first measurement value in the function after the change may be determined as the third tone value. A case will be considered where a first function (broken line in FIG. 2) which is a linear function representing the correspondence between tone values and target values is predetermined. In this case, a second function may be determined in which the slope or intercept of the first function is changed such that the first measurement value is associated with the first tone value. Then, the tone value corresponding to the target value of the first measurement value in the second function may be determined as the third tone value.

  FIG. 4A shows the process of S104. If the first measurement value is equal to or greater than the second threshold value, it is considered that the slope of the linear function that approximates the correspondence between the gradation value and the measurement value is larger than the slope of the first function. The linear function that approximates the correspondence between the gradation value and the measurement value is considered to be a function obtained by changing the slope of the first function. Therefore, in S104, the correction value generation unit 123 sets the first measurement value to be associated with the first gradation value based on the first function, the first gradation value, and the first measurement value. The third function is determined by changing the slope of the function. Then, the correction value generation unit 123 determines, as the third gradation value, the gradation value corresponding to the target value of the first measurement value in the third function. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

  FIG. 4B shows the process of S105. If the first measured value is equal to or greater than the first threshold and less than the second threshold, it is considered that the maximum value of the gradation values at which the display element does not emit light is shifted from the gradation value 0 to the high gradation side Be Therefore, a linear function that approximates the correspondence between the gradation value and the measurement value is considered to be a function obtained by changing the intercept of the first function. Therefore, in S104, the correction value generation unit 123 sets the first measurement value to be associated with the first gradation value based on the first function, the first gradation value, and the first measurement value. Determine the fourth function by changing the intercept of the function. Then, the correction value generation unit 123 determines, as the third gradation value, the gradation value corresponding to the target value of the first measurement value in the fourth function. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

In S103, the correction value generation unit 123 compares the second measurement value with the second threshold (the target value of the first measurement value). If the second measured value is equal to or greater than the second threshold, the process proceeds to S106. If the second measured value is less than the second threshold, the process proceeds to S107. Specifically, when the first measured value is less than the first threshold and the second measured value is greater than or equal to the second threshold, the process of S106 is performed. Then, when the first measured value is less than the first threshold and the second measured value is less than the second threshold, the process of S107 is performed.

  If the first measurement value is less than the first threshold value, at least the second measurement value can be used to estimate the third tone value as the measurement value of the measuring instrument 102. Here, it is assumed that a function representing the correspondence between the gradation value and the target value (the target value of the measured value) is determined in advance. In this case, the function may be changed so that the second measurement value is associated with the second tone value. Then, the tone value corresponding to the target value of the first measurement value in the function after the change may be determined as the third tone value.

  FIG. 4C shows the process of S106. If the first measurement value is less than the first threshold value and the second measurement value is greater than or equal to the second threshold value, it is considered that a third gradation value exists between the first gradation value and the second gradation value. Be Therefore, in S106, the correction value generation unit 123 represents the correspondence between the gradation value and the measurement value based on the first gradation value, the second gradation value, the first measurement value, and the second measurement value. Determine the fifth function. In the present embodiment, as the fifth function, a linear function is determined in which the first measurement value is associated with the first tone value and the second measurement value is associated with the second tone value. Then, the correction value generation unit 123 determines a tone value corresponding to the target value of the first measurement value in the fifth function as the third tone value. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

  FIG. 4D shows the process of S107. When the first measured value is less than the first threshold and the second measured value is less than the second threshold, the maximum value of the gradation values at which the display element does not emit light is shifted from the gradation value 0 to the high gradation side it seems to do. Therefore, in S107, the correction value generation unit 123 sets the first measurement value to be associated with the second gradation value based on the first function, the second gradation value, and the second measurement value. The sixth function is determined by changing the intercept of the function. Then, the correction value generation unit 123 determines, as the third gradation value, the gradation value corresponding to the target value of the first measurement value in the sixth function. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

  Note that the flowchart in FIG. 3 may be executed when determining correction values of gradation values (for example, gradation values A and B in FIG. 2) with large variations in light emission luminance. It is considered that there are almost no display elements that do not emit light at gradation values with small variations in emission luminance (for example, gradation values C and D in FIG. 2). Therefore, when generating a correction value of a gradation value having a small variation in light emission luminance, it is not necessary to use a plurality of measurement values corresponding to a plurality of gradation values. For example, the correction value of the gradation value with small variation in light emission luminance may be generated using the method of FIG. 4A, the method of FIG. 4B, or the like.

(Image display device)
Next, the configuration of the image display apparatus 101 will be described. As shown in FIG. 1, the image display device 101 includes a display panel 111, a correction value storage unit 112, a correction value interpolation unit 113, an image correction unit 114, and the like.

  The display panel 111 displays an image corresponding to the image data input to the display panel 111 on the screen. Specifically, the display panel 111 includes a plurality of display elements, and drives the respective display elements in accordance with the gradation value of the image data. Thereby, an image is displayed on the screen. In the present embodiment, the display image data output from the image correction unit 114 is output to the display panel 111.

The correction value storage unit 112 stores the correction value output from the correction value generation device 104. In this embodiment, the correction value corresponding to the gradation value A in FIG. 2 and the correction value corresponding to the gradation value C are output from the correction value generation device 104 and recorded in the correction value storage unit 112. Note that the correction value stored in the correction value storage unit 112, that is, the correction value generated by the correction value generation device 104 is not limited to the above two types of correction values. The correction value generation device 104 may generate two or more types of correction values corresponding to two or more tone values. For example, the correction value generation device 104 may generate three types of correction values corresponding to three tone values. The correction value generation device 104 may generate correction values for all possible gradation values of the input image data.

  The correction value interpolation unit 113 calculates a correction value corresponding to the gradation value of the input image data based on the correction value stored in the correction value storage unit 112 and the gradation value of the input image data. Then, the correction value interpolation unit 113 outputs the calculated correction value to the image correction unit 114. The correction value interpolation unit 113, for each of a plurality of correction areas in the screen, is applied to the correction area based on the gradation value of the input image data to be displayed in the correction area and the correction value corresponding to the correction area. A correction value for correcting the tone value of the input image data to be displayed is calculated.

  The shape, size, and arrangement of the plurality of correction areas are not particularly limited. When input image data to be displayed in the correction area has a plurality of pixels, the correction value can be calculated using a representative tone value representing the tone value of the plurality of pixels. The representative tone values are the maximum value, the minimum value, the average value, the median value, the mode value, etc. of the tone values.

  When the correction value storage unit 112 stores the correction value corresponding to the gradation value of the input image data, the correction value interpolation unit 113 stores the correction value corresponding to the gradation value of the input image data. The correction value read out from the unit 112 is output. When the correction value storage unit 112 does not store the correction value corresponding to the gradation value of the input image data, the correction value interpolation unit 113 performs interpolation using the correction value stored in the correction value storage unit 112. Thus, the correction value corresponding to the tone value of the input image data is calculated.

  FIG. 5 shows an example of a method of interpolating correction values when the correction value storage unit 112 stores the correction values of the gradation values A and C in FIG. In the example of FIG. 5, the correction value corresponding to the gradation value (for example, gradation value B) between gradation value A and gradation value C is the correction value of gradation value A and the correction value of gradation value C. It is calculated by linear interpolation using. The correction value corresponding to the gradation value smaller than the gradation value A is calculated using 0 as the correction value of the gradation value 0. Specifically, the correction value corresponding to the gradation value smaller than the gradation value A is calculated by linear interpolation using the correction value of the gradation value 0 and the correction value of the gradation value A. The correction value corresponding to the gradation value larger than the gradation value C is calculated using 0 as the correction value of a predetermined gradation value (for example, gradation value D) larger than the gradation value C. Specifically, the correction value corresponding to the gradation value larger than the gradation value C is calculated by linear interpolation using the correction value of the gradation value C and the correction value of the predetermined gradation value. Then, 0 is used as a correction value corresponding to a tone value equal to or higher than a predetermined tone value. The predetermined tone value may be any tone value as long as the variation of the light emission luminance is sufficiently small.

  The interpolation method of the correction value is not limited to the interpolation method of FIG. For example, the correction value may be calculated not by linear interpolation but by non-linear interpolation. 0 may be used as a correction value corresponding to a tone value larger than the tone value C.

  The image correction unit 114 generates display image data by correcting each gradation value of the input image data using the correction value output from the correction value interpolation unit 113. Then, the image correction unit 114 outputs the generated display image data to the display panel 111. By correcting the tone value of the input image data over the entire screen, it is possible to reduce the uneven brightness of the display image. Before the correction value is generated, the image correction unit 114 outputs the input image data as display image data.

Note that the image processing performed when generating display image data is not limited to the above processing (image processing for reducing luminance unevenness; luminance unevenness reduction processing). For example, display image data may be generated by performing a plurality of image processing including luminance unevenness reduction processing on input image data. The image processing other than the brightness non-uniformity reduction processing is, for example, blurring processing, edge enhancement processing, or the like.

  As described above, according to the present embodiment, not only the measured value corresponding to the first tone value but also the measured value corresponding to the second tone value is used to correct the first tone value. A correction value is generated. Thus, it is possible to more reliably generate a correction value that reduces the luminance unevenness of the display image with high accuracy. Specifically, when the first measurement value is equal to or greater than the first threshold value, the correction value of the first tone value is generated using the first measurement value. Then, when the first measurement value is less than the first threshold value, the correction value of the first tone value is generated using at least the second measurement value. Thus, even when the first measurement value is less than the first threshold value, it is possible to generate a correction value with high correction accuracy. That is, it is possible to generate a correction value with high correction accuracy not only for large variations in light emission luminance but also for gradation values at which the light emission luminance is extremely low or the display element does not emit light.

  In both of S104 and S105 of FIG. 3, the correction value of the first tone value may be generated by the method of FIG. 4A. In both S104 and S105, the correction value of the first tone value may be generated by the method of FIG. 4 (B). In S104, the correction value of the first tone value may be generated by the method of FIG. 4B, and in S105, the correction value of the first tone value may be generated by the method of FIG. 4A. One of the method of FIG. 4A and the method of FIG. 4B is selected and used so that a correction value having a larger correction amount can be obtained in consideration of the curve shape of the input / output characteristics of the display element and the like. It may be done. One of the method of FIG. 4A and the method of FIG. 4B may be selected and used so as to obtain a correction value with a smaller correction amount. Further, the method of estimating the third tone value in S104 and S105 is not limited to the method of FIGS. 4 (A) and 4 (B). For example, the estimation method is appropriately changed according to the curve shape of the target input / output characteristic. Further, in S104 and S105, the correction value of the first tone value may be generated without estimating the third tone value. In S104 and S105, the correction value of the first tone value may be generated using the first measurement value. Thereby, a correction value with high correction accuracy can be generated.

  In both of S106 and S107 of FIG. 3, the correction value of the first tone value may be generated by the method of FIG. In both S106 and S107, the correction value of the first tone value may be generated by the method of FIG. In S106, the correction value of the first tone value may be generated by the method of FIG. 4D, and in S107, the correction value of the first tone value may be generated by the method of FIG. 4C. One of the method of FIG. 4C and the method of FIG. 4D is selected and used so that a correction value having a larger correction amount can be obtained in consideration of the curve shape of the input / output characteristics of the display element and the like. It may be done. Either the method of FIG. 4C or the method of FIG. 4D may be selected and used so that a correction value with a smaller correction amount can be obtained. Further, the method of estimating the third tone value in S106 and S107 is not limited to the methods shown in FIGS. 4 (C) and 4 (D). For example, the estimation method is appropriately changed according to the curve shape of the target input / output characteristic. In S106 and S107, the correction value of the first tone value may be generated without estimating the third tone value. In S106 and S107, the correction value of the first tone value may be generated using at least the second measurement value. Thereby, a correction value with high correction accuracy can be generated.

  In the present embodiment, an example is described in which input image data having uniform gradation values is used to obtain a measurement result representing unevenness in luminance of a display image, but the present invention is not limited to this. For example, a measurement value of luminance on the screen may be obtained. For example, image data having different gradation values among a plurality of measurement areas may be used as input image data.

The second measurement value is used only when the first measurement value is less than the first threshold. That is, the second measured value is not used when the first measured value is greater than or equal to the first threshold. Therefore, the luminance on the screen is measured in a state in which the display element in the measurement area whose first measurement value is less than the first threshold emits light (drives) at the second gradation value and the other display elements do not emit light. It is also good. Thereby,
Since the display element in the measurement area where the first measurement value is equal to or more than the first threshold does not emit light, it is possible to improve the measurement accuracy of luminance in the measurement area where the first measurement value is less than the first threshold. Specifically, by optimally adjusting the exposure time and the like of the measuring instrument 102, it is possible to measure the luminance in the measurement region where the first measurement value is less than the first threshold with very high measurement accuracy. As a result, for the measurement region in which the first measurement value is less than the first threshold value, the second measurement value measured with high measurement accuracy can be used, and a correction value with higher correction accuracy can be obtained.

Example 2
Hereinafter, a correction value generation device and a correction value generation method according to a second embodiment of the present invention will be described with reference to the drawings. In this embodiment, a configuration (method) capable of obtaining a correction value with higher correction accuracy will be described. In the following, configurations and processes different from the first embodiment will be described in detail, and descriptions of the same configurations and processes as the first embodiment will be omitted.

  The configuration of the image display system according to the present embodiment is the same as that of the first embodiment (FIG. 1). Hereinafter, an example of the processing flow of the image display system according to the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing an example of the process flow of the image display system according to the present embodiment.

  First, the control unit 121 instructs the image data output device 103 to output the image data of the first tone value (S201). By this processing, image data of the first tone value is output from the image data output device 103 to the image display device 101. At this time, in the image display apparatus 101, the brightness nonuniformity reduction processing is not performed. Therefore, the image data of the first tone value is used as display image data, and an image according to the first tone value is displayed on the screen of the image display device 101.

  Next, the measuring instrument 102 measures the luminance on the screen of the image display device 101, and outputs the measured value of the luminance to the measured value acquiring unit 122 (S202). By this processing, the measurement value acquisition unit 122 acquires a measurement value (first measurement value) corresponding to the first tone value.

  Then, the correction value generation unit 123 determines whether the first measurement value is equal to or more than the first threshold (S203). If the first measurement value is greater than or equal to the first threshold value, the process proceeds to S204. If the first measurement value is less than the first threshold value, the process proceeds to S205. In S204 and S205, a generation process of generating the correction value of the first tone value is performed. In the present embodiment, the correction value generated by the generation process (the process of S204 or S205) is referred to as a "provisional correction value". As described in the first embodiment, the first threshold may be a fixed value previously determined by the manufacturer or the like, or may be a value changeable by the user. The first threshold can be determined based on, for example, spatial resolution or level resolution of luminance unevenness measurement, a curve shape of input / output characteristics of a display element, or the like. In the present embodiment, it is preferable to use a value of 10 to 30% of the target value of the first measurement value as the first threshold.

  In S204, the correction value generation unit 123 generates a temporary correction value using the first measurement value. For example, the correction value is generated in the same manner as in the first embodiment. Specifically, when the first measurement value is equal to or greater than the second threshold value, the temporary correction value is generated by the method of FIG. 4A, and when the first measurement value is less than the second threshold value, A provisional correction value is generated by the method of FIG. 4 (B). Thereafter, the process proceeds to S206.

  In S205, the correction value generation unit 123 generates a correction value for correcting the first tone value to the second tone value as a temporary correction value. Thereafter, the process proceeds to S206.

In S206, the correction value generation unit 123 outputs (sets) the temporary correction value generated in the generation process (the process of S204 or S205) to the image display device 101. As a result, in the image display apparatus 101, the first tone value is corrected with the temporary correction value, and the display image is updated to an image according to the tone value after the correction. By correcting the first tone value with the temporary correction value, the luminance unevenness of the display image is reduced. In the present embodiment, a tone value obtained by correcting the first tone value with a temporary correction value is referred to as a “corrected tone value”.

  Next, the measuring instrument 102 measures the luminance on the screen of the image display device 101, and outputs the measured value of the luminance to the measured value acquiring unit 122 (S207). By this processing, the measurement value acquisition unit 122 acquires a measurement value (corrected measurement value) corresponding to the correction tone value. When the provisional correction value is generated by the process of S205, the second gradation value is obtained as the correction gradation value, and the second measurement value is obtained as the correction measurement value.

  Then, the correction value generation unit 123 updates the temporary correction value using the correction measurement value obtained in S207 (S208; update processing). In the present embodiment, the updated correction value is referred to as a “final correction value”.

  Next, the correction value generation unit 123 outputs (sets) the final correction value generated in S208 to the image display device 101 (S209). As a result, in the image display device 101, the correction value used as the correction value of the first tone value is updated from the temporary correction value to the final correction value. By using the final correction value, the luminance unevenness of the display image is further reduced.

  An example of the process of S208 will be described. In S208, using the correction measurement value, a third gradation value which is a gradation value at which the target value of the first measurement value is obtained as the measurement value of the measuring device 102 is estimated. Specifically, a seventh function in which the slope or intercept of the first function is changed such that the correction measurement value is associated with the correction tone value is determined, and the seventh function corresponds to the target value of the first measurement value. The tone value is determined as the third tone value. Then, as a final correction value, a correction value is generated which brings the first tone value close to the third tone value.

  In this embodiment, the temporary correction value is a correction value that corrects the first gradation value to a gradation value smaller than the first gradation value, or the first correction value is a gradation value larger than the first gradation value. The estimation method of the third tone value is switched depending on whether the tone value is to be corrected or not. A specific example of the process of S208 will be described using FIGS. 7 (A) and 7 (B). FIGS. 7A and 7B illustrate the process of S208.

  FIG. 7A shows an example in the case where a temporary correction value for correcting the first tone value to a tone value smaller than the first tone value is obtained. In this case, the correction value generation unit 123 sets the slope of the first function so that the correction measurement value is associated with the correction gradation value based on the first function, the correction gradation value, and the correction measurement value. By changing, the eighth function is determined. Then, the correction value generation unit 123 determines, as the third tone value, the tone value corresponding to the target value of the first measurement value in the eighth function. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

  FIG. 7B shows an example in the case where a temporary correction value for correcting the first tone value to a tone value larger than the first tone value is obtained. In this case, the correction value generation unit 123 sets the intercept of the first function so that the correction measurement value is associated with the correction gradation value based on the first function, the correction gradation value, and the correction measurement value. By changing, the ninth function is determined. Then, the correction value generation unit 123 determines the tone value corresponding to the target value of the first measurement value in the ninth function as the third tone value. After that, the correction value generation unit 123 generates a correction value that brings the first tone value close to the third tone value as the correction value of the first tone value.

Note that the process of S208 is not limited to the above process. For example, regardless of the provisional correction value, the final correction value may be generated by the method of FIG. 7 (A). The final correction value may be generated by the method of FIG. 7B regardless of the temporary correction value. When a temporary correction value for correcting the first tone value to a tone value smaller than the first tone value is obtained, the final correction value may be generated by the method of FIG. 7 (B). Then, when a temporary correction value for correcting the first tone value to a tone value larger than the first tone value is obtained, the final correction value may be generated by the method of FIG. 7A. The method of estimating the third tone value in S208 is not limited to the methods shown in FIGS. 7 (A) and 7 (B). For example, the estimation method is appropriately changed according to the curve shape of the target input / output characteristic. Further, in S208, the final correction value may be generated without estimating the third tone value. In S208, a final correction value may be generated using the correction measurement value. Thereby, a correction value with high correction accuracy can be generated.

  According to this embodiment, when the first measurement value is less than the first threshold value, the first tone value is corrected to the second tone value, and the second measurement value is obtained. Then, the correction value of the first tone value is generated using the second measurement value. Thus, even when the first measurement value is less than the first threshold value, it is possible to generate a correction value with high correction accuracy.

  In addition, when the first measurement value is equal to or greater than the first threshold value, a correction value (temporary correction value) is generated by the same method as in the first embodiment, and the first tone value is corrected by the temporary correction value. The provisional correction value is updated based on the measured value obtained in As a result, it is possible to generate a correction value having a correction accuracy higher than that of the first embodiment as the correction value of the first tone value. In the first embodiment, in order to obtain the correction value of the first tone value, two measurements at the maximum (measurement for the first tone value and measurement for the second tone value) are performed. Also in the second embodiment, the number of measurements for obtaining the correction value of the first tone value is two. Thus, in the second embodiment, it is possible to generate a correction value having a higher correction accuracy than the first embodiment without increasing the number of measurements.

<Other Embodiments>
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

  104: correction value generation device 122: measurement value acquisition unit 123: correction value generation unit

Claims (13)

An image is an apparatus having a plurality of display elements that emit light when a voltage is applied, and an apparatus that displays an image on a screen by applying a voltage according to the gradation value of image data to each display element. as measure of the brightness on the screen of the display device approaches the target value, a correction value generation unit for generating a correction value for correcting the tone values of the image data,
Acquisition means for acquiring a measured value of luminance on the screen;
Generation means for generating a correction value using the measurement value acquired by the acquisition means;
Have
The generation means is
If the first measurement value that corresponds to the first gradation value is a gradation value corresponding to the reference value or less of the voltage of the threshold voltage of the display element is equal to or larger than the first threshold, the first gradation value a correction value for correcting generated using the previous SL first measurement,
When the first measured value is less than the first threshold , a second floor having a tone value corresponding to a voltage equal to or less than the reference value and a tone value greater than the first tone value and have use a second measurement value that corresponds to the tone value, the correction value generation device and generates a correction value for correcting the first gradation value. The acquisition means acquires, for each of a plurality of measurement areas in the screen, measurement values of luminance in the measurement area;
The generation means is characterized by generating, for each of the plurality of measurement areas, a correction value for correcting a gradation value of image data to be displayed in the measurement area, using a measurement value corresponding to the measurement area. The correction value generation device according to claim 1. When the first measurement value is greater than or equal to the first threshold value, the generation means may
Estimating a third tone value, which is a tone value at which a target value of the first measurement value is obtained as the measurement value, using the first measurement value;
The correction value generation device according to claim 1 or 2, wherein a correction value that brings the first gradation value close to the third gradation value is generated as the correction value for correcting the first gradation value. . A first function, which is a linear function representing a correspondence between the gradation value and the target value, is predetermined.
When the first measurement value is greater than or equal to the first threshold value, the generation means may
Determining a second function in which a slope or an intercept of the first function is changed such that the first measurement value is associated with the first tone value;
4. The correction value generation device according to claim 3, wherein a gradation value corresponding to a target value of the first measurement value in the second function is determined as the third gradation value. The generation means is
When the first measurement value is equal to or greater than a second threshold value larger than the first threshold value,
Determining a third function in which the slope of the first function is changed such that the first measurement value is associated with the first tone value;
A tone value corresponding to a target value of the first measurement value in the third function is determined as the third tone value,
If the first measured value is greater than or equal to the first threshold and less than the second threshold,
Determining a fourth function in which an intercept of the first function is changed such that the first measurement value is associated with the first tone value;
5. The correction value generation device according to claim 4, wherein a gradation value corresponding to a target value of the first measurement value in the fourth function is determined as the third gradation value. The correction value generation device according to claim 5, wherein the second threshold is a target value of the first measurement value. When the first measurement value is less than the first threshold value, the generation means may
Estimating at least a third gradation value, which is a gradation value at which a target value of the first measurement value is obtained, as the measurement value using at least the second measurement value;
The correction value which brings the first tone value close to the third tone value is generated as the correction value for correcting the first tone value. Correction value generator for. When the first measurement value is less than the first threshold value, the generation means may
The correspondence between the gradation value and the measurement value is indicated, the first measurement value is associated with the first gradation value, and the second measurement value is associated with the second gradation value. Determine the fifth function, which is a linear function,
8. The correction value generation device according to claim 7, wherein a tone value corresponding to a target value of the first measurement value in the fifth function is determined as the third tone value. A first function, which is a linear function representing a correspondence between the gradation value and the target value, is predetermined.
When the first measurement value is less than the first threshold value, the generation means may
A sixth function is determined in which the intercept of the first function is changed such that the second measurement value is associated with the second tone value,
8. The correction value generation device according to claim 7, wherein a tone value corresponding to a target value of the first measurement value in the sixth function is determined as the third tone value. A first function, which is a linear function representing a correspondence between the gradation value and the target value, is predetermined.
The generation means is
If the first measured value is less than the first threshold and the second measured value is equal to or greater than a second threshold greater than the first threshold,
The correspondence between the gradation value and the measurement value is indicated, the first measurement value is associated with the first gradation value, and the second measurement value is associated with the second gradation value. Determine the fifth function, which is a linear function,
A tone value corresponding to a target value of the first measurement value in the fifth function is determined as the third tone value,
If the first measured value is less than the first threshold and the second measured value is less than the second threshold,
A sixth function is determined in which the intercept of the first function is changed such that the second measurement value is associated with the second tone value,
8. The correction value generation device according to claim 7, wherein a tone value corresponding to a target value of the first measurement value in the sixth function is determined as the third tone value. The generation means is
If the first measurement value is equal to or greater than the first threshold value, the correction value generated using the previous SL first measurement value for correcting the first gradation value and said first measured value is the first If it is less than the first threshold value, a correction value for correcting the first gradation value to the second gradation value, performs generate process that generates a correction value for correcting the first gradation value,
An update process is performed to update the correction value generated by the generation process using a measured value corresponding to the gradation value obtained by correcting the first gradation value with the correction value generated by the generation process. The correction value generation device according to claim 1 or 2. An image is an apparatus having a plurality of display elements that emit light when a voltage is applied, and an apparatus that displays an image on a screen by applying a voltage according to the gradation value of image data to each display element. as measure of the brightness on the screen of the display device approaches the target value, a correction value generation process of generating a correction value for correcting the tone values of the image data,
An acquisition step of acquiring a measured value of luminance on the screen;
Generating the correction value using the measurement value acquired in the acquisition step;
Have
In the generation step,
If the first measurement value that corresponds to the first gradation value is a gradation value corresponding to the reference value or less of the voltage of the threshold voltage of the display element is equal to or larger than the first threshold, the first gradation value Generating a correction value to be corrected using the first measurement value;
When the first measured value is less than the first threshold , a second floor having a tone value corresponding to a voltage equal to or less than the reference value and a tone value greater than the first tone value and it has use a second measurement value that corresponds to the tone value, the correction value generation method characterized by generating a correction value for correcting the first gradation value.   A program causing a computer to execute each step of the correction value generation method according to claim 12.

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