JP2016110158A - Display device, display device control method, program, and processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of obtaining a display image with a wide dynamic range and a wide color region, by a reduced processing load.SOLUTION: A display device comprises: light emission means; display means which modulates light from the light emission means and thereby displays an image on a screen; acquisition means which acquires base image data and difference data to use for magnification processing of magnifying at least one of a dynamic range and a color region of image data; control means which controls light emission of the light emission means on the basis of the difference data: and generation means which generates display image data to use for display by the display means, on the basis of the base image data.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a display device, a display device control method, and a program.

  In recent years, HDR (High Dynamic Range) display has been performed in which multi-bit image data is used to obtain a display image close to the real thing (an image displayed on the screen).

  As one method of recording HDR image data (multi-bit image data) having a wide dynamic range or color gamut, there is a method of dividing the HDR image data into base image data and difference data, and recording the base image data and difference data. Yes (Patent Document 1). That is, as one of data formats of HDR image data, there is a format using base image data and difference data. The base image data is low-bit image data obtained by gradation-compressing HDR image data. The difference data is, for example, data representing a difference between luminance values (tone values) between the base image data and the HDR image data.

  By using such a data format, it is possible to perform image display on both a display device that can execute HDR display and a display device that cannot execute HDR display. Specifically, a display device capable of executing HDR display can restore HDR image data from base image data and difference data and display HDR image data. Further, the base image data can be displayed in a display device that cannot perform HDR display.

  If the data format described above is used, the signal band between the output device (device that outputs image data) and the display device can be reduced. Specifically, a technique has been proposed in which an output device outputs base image data and difference data, and a display device restores HDR image data from the base image data and difference data (Patent Document 2). By dividing the HDR image data into the base image and the difference information, the signal band can be reduced as compared with the case of outputting the HDR image data.

  However, in a conventional display device, multi-bit HDR image data is processed in order to obtain a display image with a wide dynamic range and color gamut. As a result, the processing load and circuit scale increase.

JP 2011-193511 A JP 2007-121375 A

  An object of the present invention is to provide a technique capable of obtaining a display image with a wide dynamic range and color gamut with a small processing load.

The first aspect of the present invention is:
Light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
Acquisition means for acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
Control means for controlling the light emission of the light emitting means based on the difference data;
Generating means for generating display image data to be used for display on the display means based on the base image data;
It is a display device characterized by having.

The second aspect of the present invention is:
Light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
Acquisition means for acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
Enlarging means for generating HDR image data by applying an enlargement process using the difference data to the base image data;
Reduction means for generating restricted HDR image data by reducing the dynamic range of the HDR image data so as to match the dynamic range that can be taken by the image displayed on the screen;
Control means for controlling light emission of the light emitting means based on the restricted HDR image data;
Correction for generating display image data used for display on the display unit by correcting the gradation value of the limited HDR image data based on the difference between the emission based on the limited HDR image data and the reference emission. Means,
It is a display device characterized by having.

The third aspect of the present invention is:
Light emitting means;
A display means for displaying an image on a screen by modulating light from the light emitting means, and a control method for a display device,
An acquisition step of acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
A control step of controlling light emission of the light emitting means based on the difference data;
Based on the base image data, a generating step for generating display image data used for display on the display means;
A control method for a display device, comprising:

The fourth aspect of the present invention is:
Light emitting means;
A display means for displaying an image on a screen by modulating light from the light emitting means, and a control method for a display device,
An acquisition step of acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
An enlargement step for generating HDR image data by applying an enlargement process using the difference data to the base image data;
A reduction step of generating restricted HDR image data by reducing the dynamic range of the HDR image data so as to match the dynamic range of the image displayed on the screen;
A control step of controlling light emission of the light emitting means based on the limited HDR image data;
Correction for generating display image data used for display on the display unit by correcting the gradation value of the limited HDR image data based on the difference between the emission based on the limited HDR image data and the reference emission. Steps,
A control method for a display device, comprising:

  According to a fifth aspect of the present invention, there is provided a program that causes a computer to execute each step of the above-described display device control method.

  According to the present invention, a display image having a wide dynamic range and color gamut can be obtained with a small processing load.

1 is a block diagram illustrating an example of a functional configuration of a display device according to Embodiment 1. FIG. 1 is a block diagram illustrating an example of a functional configuration of an HDR processing unit according to the first embodiment. The figure which shows an example of the table for correct | amending a luminance ratio The figure which shows an example of a process of a block MaxRatio detection part. The figure which shows an example of the table for determining a backlight control value The figure which shows an example of a process of Ratio correction part FIG. 9 is a block diagram illustrating an example of a functional configuration of an HDR processing unit according to the second embodiment. FIG. 9 is a block diagram illustrating an example of a functional configuration of an HDR processing unit according to a third embodiment. The figure which shows an example of the table for producing | generating a restriction | limiting HDR image The figure which shows an example of the table for determining a backlight control value FIG. 10 is a block diagram illustrating an example of a functional configuration of an HDR processing unit according to the fourth embodiment. Figure showing an example of reverse tone map FIG. 9 is a block diagram illustrating an example of a functional configuration of an HDR processing unit according to the fifth embodiment. The figure which shows an example of the table for correct | amending the output value of a reverse tone map Figure showing an example of a converted inverse tone map

<Example 1>
Hereinafter, a display device and a control method thereof according to Embodiment 1 of the present invention will be described.
In the following, an example in which the display device according to the present embodiment is a transmissive liquid crystal display device will be described, but the display device according to the present embodiment is not limited thereto. The display device according to the present embodiment may be a display device that displays an image on a screen by modulating light from the light emitting unit. For example, the display device according to the present embodiment may be a reflective liquid crystal display device. In addition, the display device according to the present embodiment may be a MEMS shutter type display using a MEMS (Micro Electro Mechanical System) shutter instead of the liquid crystal element.

FIG. 1 is a block diagram illustrating an example of a functional configuration of the display device according to the present embodiment.
Base image data 101 and difference data are input to the display device according to the present embodiment. Specifically, color difference data 1020 and luminance difference data 1021 are input as difference data.

  The base image data 101 (first base image data) is low-bit image data obtained by gradation-compressing HDR image data (multi-bit image data) having a wide dynamic range or color gamut by bit conversion processing. In this embodiment, the base image data is RGB image data in which each of the R value, the G value, and the B value is an 8-bit value. In the present embodiment, the HDR image data is RGB image data in which each of the R value, the G value, and the B value is a 32-bit value.

  The difference data is data used in an enlargement process for enlarging at least one of the dynamic range and the color gamut of the image data.

  Specifically, the color difference data 1020 is data used in a color gamut expansion process for expanding the color gamut of the image data, and is data representing a color difference between the HDR image data and the base image data. For example, the color difference data is a color difference value (Cb value, Cr value) of the base image data and a color difference value (Cb value, Cr value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). This is data representing a color difference value which is a difference value obtained by subtracting the other from one. However, the color difference data is a color difference value (Cb value, Cr value) of the base image data and a color difference value (Cb value, Cr value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). Color ratio data representing a color ratio that is a ratio of Further, the color difference value and the color ratio may be values calculated using R value, G value, and B value instead of the color difference value. Note that the color gamut expansion processing can be said to be processing for reproducing colors that cannot be expressed by the base image data. In this embodiment, the Cb difference value and the Cr difference value of each pixel are input as the color difference data 1020. In this embodiment, the Cb difference value and the Cr difference value are each expressed in an 8-bit floating point format. The Cb difference value is a value obtained by subtracting the other from one of the Cb value of the base image data 101 and the HDR image data. The Cr difference value is a Cr value of the base image data 101 and a Cr value of the HDR image data. Is the value obtained by subtracting the other from the other.

  The luminance difference data 1021 (first difference data) is data used in the luminance area expansion processing for expanding the dynamic range of the image data, and is data representing the difference between the luminance values of the HDR image data and the base image data. For example, the luminance difference data is a ratio between the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image data in pixel units (or in units of regions including a predetermined number of pixels). This is luminance ratio data representing the luminance ratio. That is, the luminance difference data is the ratio of the luminance value (gradation value) of the HDR image data to the luminance value (gradation value) of the base image data or the reciprocal thereof in pixel units (or an area unit composed of a predetermined number of pixels). Is luminance ratio data representing However, the luminance difference data is obtained by subtracting one from the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). Data representing a luminance difference value which is a subtracted difference value may be used. Further, the luminance difference data may be luminance conversion table data (for example, a reverse tone map described later) representing a correspondence relationship between the input luminance value and the output luminance value in the luminance range expansion process. Note that the luminance range expansion processing can also be said to be processing for reproducing luminance that cannot be expressed in the base image data. In the present embodiment, as the luminance difference data 1021, the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image in units of pixels (or a region unit composed of a predetermined number of pixels). Brightness ratio data representing the brightness ratio, which is a ratio, is input. In this embodiment, the luminance ratio is expressed in an 8-bit floating point format. The gradation value is a pixel value, a luminance value, or the like.

Note that the number of bits of the HDR image data, the base image data 101, the color difference data 1020, and the luminance difference data 1021 is not particularly limited.
Note that at least one of the color difference data 1020 and the luminance difference data 1021 may not be input. For example, when gradation compression is performed on HDR image data, the luminance value may change, but the color may not change. That is, the colors of the HDR image data and the base image data 101 may match. In such a case, the color difference data 1020 is not necessary. Further, when the base image data 101 is image data obtained by compressing the color gamut of the HDR image data, the brightness values of the HDR image data and the base image data 101 may match. In such a case, the luminance difference data 1021 is not necessary.

The relationship among the pixel value of the HDR image data corresponding to the original image data, the pixel value of the base image data 101, the value of the color difference data 1020, and the value of the luminance difference data 1021 is expressed by the following Expression 1. In Equation 1, (Ro, Go, Bo) is the pixel value of the HDR image data, and (R, G, B) is the pixel value of the base image data 101. ResCb is a Cb difference value represented by the color difference data 1020, ResCr is a Cr difference value represented by the color difference data 1020, and Ra is a luminance ratio represented by the luminance difference data 1021. M is a conversion matrix for converting RGB values into YCbCr values, and M ⁻¹ (inverse matrix of matrix M) is a conversion matrix for converting YCbCr values into RGB values.

  The HDR processing unit 105 acquires the base image data 101, the color difference data 1020, and the luminance difference data 1021, and generates the display image data 106 based on the acquired information and the backlight control value 108. Or generate. Then, the HDR processing unit 105 outputs the display image data 106 to the liquid crystal panel 107 and outputs the backlight control value 108 to the backlight 109. The display image data is image data used for display on the liquid crystal panel 107. The backlight control value 108 corresponds to the light emission luminance of the backlight 109. Hereinafter, the luminance of the light emitted from the backlight 109 is referred to as “emission luminance”.

  The liquid crystal panel 107 includes a plurality of liquid crystal elements, a liquid crystal driver, a control board, and the like. The control board controls the liquid crystal driver, and the liquid crystal driver drives each liquid crystal element. In this embodiment, the transmittance of each liquid crystal element is controlled based on the display image data 106. Specifically, the control board outputs a control signal corresponding to the display image data 106 to the liquid crystal driver, and the liquid crystal driver drives each liquid crystal element according to the control signal from the control board. The light from the backlight 109 is transmitted through each liquid crystal element, whereby an image (display image) is displayed on the screen.

The backlight 109 is a light emitting unit that irradiates light to the back surface of the liquid crystal panel 107. The backlight 109 includes a light source, a drive circuit that drives the light source, an optical unit that diffuses light from the light source, and the like. In the present embodiment, the backlight 109 emits light with a light emission luminance corresponding to the backlight control value 108. Specifically, the drive circuit drives the light source so as to emit light with the light emission luminance corresponding to the backlight control value. Further, in the present embodiment, the backlight 109 is configured to be able to control the light emission luminance in units of light emission areas composed of a plurality of pixels. Specifically, the backlight 109 is configured to be able to individually control the light emission luminances of a plurality of light emission regions that constitute a screen region. For example, the backlight 109 has a light source for each light emitting region. The light source has one or more light emitting elements. As the light emitting element, a light emitting diode (LED), an organic EL element, a cold cathode tube, or the like can be used.
In this embodiment, an example in which a screen area is configured by a plurality of light emitting areas will be described. However, a screen area may be configured by one light emitting area.

  The control unit 110 controls the operation and timing of each functional unit through a control line (not shown).

In this embodiment, when the original image data (HDR image data) is still image data, base image data and difference data corresponding to one piece of still image data exist, and the original image data is moving image data. Includes base image data and difference data for each frame. In this embodiment, the base image data and the difference data are input to the display device for each frame regardless of whether the original image data is still image data or moving image data. In such a configuration, the internal processing (internal processing of the display device) when the original image data is still image data and the internal processing when the original image data is moving image data may be shared. it can.

  Here, when the original image data is moving image data, it is preferable to calculate the backlight control value 108 for each frame from the viewpoint of image quality. However, when the original image data is still image data, the backlight control value 108 is calculated only once instead of calculating the backlight control value 108 for each frame from the viewpoint of image quality and calculation amount. preferable. By limiting the number of times the backlight control value 108 is calculated to one, the amount of calculation can be reduced compared to the case where the backlight control value 108 is calculated for each frame. Further, it is possible to suppress the backlight control value 108 from fluctuating due to noise or the like even though the base image data and the difference data are not changed.

When the base image data 101, the color difference data 1020, and the luminance difference data 1021 are information on still image data, the control unit 110 calculates and outputs the backlight control value 108 only once. The unit 105 is controlled. Specifically, the HDR processing unit 105 is controlled so that the backlight control value 108 is calculated and output only for the first frame of still image data. Thereby, the process for controlling the light emission luminance is performed for the first frame of the still image data, and the process for controlling the light emission luminance is omitted for the second and subsequent frames of the still image data.
The control unit 110 also calculates the backlight control value 108 for each frame when the base image data 101, the color difference data 1020, and the luminance difference data 1021 are information on moving image data. 105 is controlled. Thereby, processing for controlling the light emission luminance is performed for each frame of the moving image data.
Note that, regardless of whether the original image data is still image data or moving image data, a process for controlling the light emission luminance may be performed for each frame.

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the HDR processing unit 105.

  The image processing unit 201 acquires base image data 101 and color difference data 1020. Then, the image processing unit 201 performs predetermined image processing on the base image data 101 to generate processing base image data 202 (second base image data). In this embodiment, the predetermined image processing includes color gamut expansion processing using the color difference data 1020. In the present embodiment, predetermined image processing is performed not on multi-bit HDR image data but on low-bit base image data. Thereby, the processing load and circuit scale of the image processing unit 201 can be reduced as compared with the case where predetermined image processing is performed on multi-bit HDR image data.

In this embodiment, the pixel value after the color gamut expansion processing is calculated using the following Expression 2. In Equation 2, (Rc, Gc, Bc) is a pixel value after color gamut expansion processing.

  A plurality of image processes may be executed as the predetermined image process. For example, the predetermined image processing may include brightness adjustment processing, contrast adjustment processing, chroma adjustment processing, sharpness adjustment processing, and the like. The predetermined image processing may not include the color gamut expansion processing.

The ratio range conversion unit 204 acquires luminance difference data 1021. And Ra
The thio range conversion unit 204 corrects the luminance difference data 1021 to generate conversion difference data 205 (second difference data) having a smaller dynamic range expansion degree than the luminance difference data 1021.
In order to obtain a display image close to the real thing (image displayed on the screen), it is preferable that display luminance (luminance on the screen) of about 10000 cd / m ² can be displayed. However, the maximum value of the dynamic range that can be taken by the display image is not necessarily wide, and it is not always possible to display a display luminance of about 10,000 cd / m ² . Specifically, the upper limit value of the luminance of the display image is the upper limit value of the light emission luminance of the backlight 109 (or a value slightly lower than the upper limit value of the light emission luminance of the backlight 109), but the backlight 109 is 10,000 cd / m ^2. It is not always possible to emit light with a light emission luminance of a certain degree.
Therefore, the ratio range conversion unit 204 corrects the luminance difference data 1021 so that the dynamic range of the image data after the luminance range expansion processing using the conversion difference data 205 matches the dynamic range that the display image can take. In this embodiment, the luminance difference data 1021 is corrected so that the dynamic range of the image data after the luminance range expansion processing using the conversion difference data 205 matches the maximum value of the dynamic range that can be taken by the display image.

  In this embodiment, the luminance difference data 1021 is converted into the conversion difference data 205 using the conversion lookup table. The conversion lookup table represents a correspondence relationship between a pre-conversion luminance ratio that is a luminance ratio before conversion (before correction) and a post-conversion luminance ratio that is a luminance ratio after conversion.

FIG. 3 shows an example of the conversion lookup table. In FIG. 3, the horizontal axis represents the pre-conversion luminance ratio, and the vertical axis represents the post-conversion luminance ratio. FIG. 3 shows an example where the upper limit value of the display brightness is 5000 cd / m ² .
In this embodiment, a backlight control value is generated based on the luminance ratio. Specifically, when the luminance ratio is high, a backlight control value corresponding to a higher light emission luminance is generated than when the luminance ratio is low. For example, the backlight control value is generated, the backlight control value corresponding to the light emission luminance = 5000 cd / ^{m 2} when the luminance ratio = 50 times that corresponds to the light emission luminance = 100 cd / ^{m 2} when the luminance ratio = 1 times Is generated.

As described above, the upper limit value of the display brightness is 5000 cd / m ² . Therefore, in the example of FIG. 3, the upper limit value of the converted luminance ratio is limited to 50.
In addition, the luminance difference data 1021 generally includes a large number of pre-conversion luminance ratios near 1 ×. Therefore, in the example of FIG. 3, the same value as the pre-conversion luminance ratio is set as the post-conversion luminance ratio in the vicinity of the pre-conversion luminance ratio = 1.
In a high luminance region, the difference in brightness is difficult to perceive. Therefore, in the example of FIG. 3, the range = 10 times the pre-conversion luminance ratio (1000cd ^/ m 2) ~100 fold (10000cd / ^{m 2),} is compressed in the range = 10 to 50 times of the converted luminance ratio Yes.
In the example of FIG. 3, the post-conversion luminance ratio is set so that the post-conversion luminance ratio does not become constant with respect to the increase of the pre-conversion luminance ratio in the range of the pre-conversion luminance ratio = 10 to 100 times. . Specifically, the post-conversion luminance ratio is set so that the post-conversion luminance ratio increases with respect to the pre-conversion luminance ratio in the pre-conversion luminance ratio range = 10 to 100 times. Thereby, it is possible to suppress white-out.

Note that the luminance difference data 1021 may be converted into the conversion difference data 205 using a function representing the correspondence between the pre-conversion luminance ratio and the post-conversion luminance ratio. That is, the luminance ratio represented by the conversion difference data 205 may be calculated using a function.
In this embodiment, the luminance difference data 1021 is corrected so that the dynamic range of the image data after the luminance range expansion processing using the conversion difference data 205 matches the maximum value of the dynamic range that can be taken by the display image. However, the present invention is not limited to this. The dynamic range of the image data after the luminance range expansion processing using the conversion difference data 205 only needs to match the dynamic range that the display image can take. The dynamic range of the image data after the luminance range expansion process using the conversion difference data 205 may coincide with a value lower than the maximum value of the dynamic range that can be taken by the display image.

  The block MaxRatio detection unit 206 and the backlight luminance determination unit 208 control the light emission luminance of the backlight 109 based on the conversion difference data 205.

The block MaxRatio detection unit 206 acquires the feature amount of the conversion difference data 205 in the light emitting region as the first feature amount. In this embodiment, a representative value of the converted luminance ratio in the light emitting area is acquired as the first feature amount. Specifically, the converted luminance ratio (block MaxRatio 207) having the largest value is detected as the first feature amount from the plurality of converted luminance ratios in the light emitting region. In this embodiment, since there are a plurality of light emitting areas, the first feature amount is acquired for each light emitting area.
Note that the first feature amount is not limited to the block MaxRatio 207. For example, the minimum value, mode value, intermediate value, average value, etc. of the converted luminance ratio may be acquired as the first feature amount.

  A specific example of the processing of the block MaxRatio detection unit 206 will be described with reference to FIG. In FIG. 4, a region surrounded by a solid line is a light emitting region. The converted luminance ratio Rbn (A) of the pixel A is 2.0 times, and the converted luminance ratio Rbn (B) of the pixel B is 1.5 times. Although the post-conversion luminance ratio of the pixels other than the pixels A and B is not shown, it is lower than 2.0 times. That is, in the example of FIG. 4, the converted luminance ratio Rbn (A) = 2.0 is the largest. In this case, the converted luminance ratio Rbn (A) = 2.0 is detected as Rmn which is the block MaxRatio.

The backlight luminance determining unit 208 controls the light emission luminance in the light emission region according to the block MaxRatio 207. Specifically, the backlight luminance determination unit 208 determines the backlight control value 108 according to the block MaxRatio 207, and outputs the determined backlight control value 108. Thereby, the emission luminance is controlled. In the present embodiment, the backlight luminance determining unit 208 acquires the light emission luminance corresponding to the block MaxRatio 207 from the lookup table representing the correspondence relationship between the luminance ratio and the light emission luminance, and the backlight control value 108 corresponding to the acquired light emission luminance. To decide. In this embodiment, since there are a plurality of light emitting areas, the backlight control value 108 is determined for each light emitting area. That is, the light emission luminance is controlled for each light emission region.
Note that the light emission luminance corresponding to the block MaxRatio 207 may be calculated using a function representing the correspondence relationship between the luminance ratio and the light emission luminance, and the backlight control value 108 corresponding to the calculated light emission luminance may be determined. The backlight control value 108 corresponding to the block MaxRatio 207 may be acquired using a table or a function representing the correspondence relationship between the luminance ratio and the backlight control value.

FIG. 5 shows an example of a lookup table used for determining the backlight control value 108. The horizontal axis in FIG. 5 indicates the luminance ratio, and the vertical axis indicates the light emission luminance.
In the example of FIG. 5, the backlight control value 108 indicating the higher light emission luminance is determined as the block MaxRatio 207 increases.

Based on the backlight control value 108, the luminance estimation unit 209 estimates the luminance (reach luminance 210) of the light emitted from the backlight 109 on the back surface of the liquid crystal panel 107. In this embodiment, it is assumed that the center position of the light emitting region is set as the position (estimated position) for estimating the reached luminance. In the present embodiment, since there are a plurality of light emitting areas, the reached luminance 210 is estimated for each light emitting area. The reached luminance 210 is estimated in consideration of attenuation of light emitted from the light source, leakage of light from other light emitting regions, and the like. In this embodiment, arrival rate information is prepared for each light emitting area. The arrival rate information represents the arrival rate of light emitted from the light source for each light source. Then, for each light emitting area, an estimation process (a process for estimating the arrival luminance 210) is performed using the arrival rate information and the backlight control value 108 of each light source. In the estimation process, the light emission luminance corresponding to the backlight control value is multiplied by the arrival rate for each light source. Then, the sum of the multiplication values of the respective light sources is calculated as the reached luminance 210. The arrival rate is a value that indicates how much light emitted from the light source reaches the estimated position, and an attenuation rate that indicates how much the luminance of the light emitted from the light source attenuates before reaching the estimated position. Is the reciprocal of
Note that the estimated position may not be the center position of the light emitting region. Moreover, the arrival brightness | luminance of several positions may be estimated about one light emission area | region. For example, the reached luminance may be estimated for each pixel.

The correction coefficient calculation unit 211 calculates a correction coefficient 212 for correcting image data based on the reached luminance 210. In this embodiment, since the reached luminance 210 is estimated for each light emitting area, the correction coefficient 212 is calculated for each light emitting area. The correction coefficient 212 is a coefficient that is multiplied by the pixel value in order to reduce a change in display luminance due to a difference between the emission luminance corresponding to the backlight control value 108 and the arrival luminance 210. In the present embodiment, the correction coefficient 212 is calculated using the following Expression 3. In Equation 3, Gpn is the correction coefficient 212, Lpn is the reached luminance 210, and Lt is the light emission luminance corresponding to the backlight control value 108.

Gpn = Lt / Lpn (Formula 3)

Note that a correction value to be added to the pixel value may be calculated instead of the correction coefficient.

  The ratio correction unit 213 and the pixel value correction unit 203 generate display image data 106 based on the processing base image data 202, the conversion difference data 205, and the block MaxRatio 207.

The Ratio correction unit 213 generates correction difference data 214 corresponding to the difference between the conversion difference data 205 and the block MaxRatio 207 based on the conversion difference data 205 and the block MaxRatio 207. In this embodiment, for each pixel, a corrected luminance whose luminance ratio corresponding to the difference between the converted luminance ratio of the pixel and the block MaxRatio 207 of the light emitting area to which the pixel belongs is the luminance ratio represented by the correction difference data 214. Calculated as a ratio. Specifically, the corrected luminance ratio is calculated for each pixel by dividing the converted luminance ratio by the block MaxRatio 207. That is, the corrected luminance ratio is calculated using the following equation 4. In Equation 4, Rbn is the converted luminance ratio, Rmn is the block MaxRatio 207, and Abn is the corrected luminance ratio. Thereby, the correction difference data 214 is generated. The post-conversion luminance ratio is the luminance ratio represented by the conversion difference data 205.

Abn = Rbn / Rmn (Formula 4)

A specific example of the processing of the ratio correction unit 213 will be described with reference to FIG. FIG. 6 shows the same light emitting area as FIG. As described above, the converted luminance ratio Rbn (A) of the pixel A is 2.0 times, and the converted luminance ratio Rbn (B) of the pixel B is 1.5 times. Then, Rmn which is the block MaxRatio is the post-conversion luminance ratio Rbn (A) = 2.0. Therefore, the corrected luminance ratio Abn (A) of the pixel A is calculated by the following formula 5, and the corrected luminance ratio Abn (B) of the pixel B is calculated by the following formula 6.

Abn (A) = Rbn (A) /Rmn=1.0 (Formula 5)
Abn (B) = Rbn (B) /Rmn=0.75 (Formula 6)

  The pixel value correction unit 203 generates display image data 106 by performing luminance region expansion processing using the correction difference data 214 on the processing base image data 202. In the present embodiment, the image data for display 106 is generated by applying the luminance range expansion process and the first correction process using the correction coefficient 212 to the process base image data 202. The luminance range expansion process is a process of correcting the gradation value of the image according to the correction luminance ratio represented by the correction difference data 214, and the first correction process is a process of multiplying the gradation value of the image data by the correction coefficient 212. It is. For the pixel at the estimated position of the reached luminance 210, the processing pixel value (the pixel value of the processing base image data 202) is multiplied by the correction luminance ratio and the correction coefficient 212 to obtain the display pixel value (the pixel of the display image data 106). Value) is calculated. For pixels at positions other than the estimated position, an interpolation correction coefficient is calculated by an interpolation process using the correction coefficient 212. Then, the display pixel value is calculated by multiplying the processing pixel value by the correction luminance ratio and the interpolation correction coefficient (correction coefficient calculated by the interpolation process). However, if the pixel value (multiplication value) after performing the luminance range expansion processing and the first correction processing is a value outside the range (input range) of pixel values that can be input to the liquid crystal panel 107, the multiplication value Is corrected to a value within the input range to calculate a display pixel value. For example, when the input range of the liquid crystal panel 107 is the same 8 bits as the base image data 101, the multiplication value is corrected so as to be a value of 8 bits or less. Further, when the input range of the liquid crystal panel 107 is 10 bits having a resolution higher than that of the base image data 101, the multiplication value is corrected so as to be a value of 10 bits or less. Display image data 106 is generated by calculating the display pixel value of each pixel.

Note that the processing pixel value at a position other than the estimated position may be multiplied by the correction coefficient 212 of the light emitting area to which the pixel belongs without calculating the interpolation correction coefficient.
Note that when the display image 106 is generated, image processing other than the luminance range expansion processing and the first correction processing may be performed on the processing base image data 202. The first correction process is preferably performed from the viewpoint of image quality, but may be omitted. When the first correction process is not performed, the processes of the luminance estimation unit 209 and the correction coefficient calculation unit 211 are not necessary.
In addition, the execution order of processing performed on the processing base image data 202 when generating the display image data 106 is not particularly limited. For example, the first correction process may be executed after the luminance area expansion process, the luminance area expansion process may be executed after the first correction process, or the luminance area expansion process and the first correction process are executed simultaneously. Also good.

  As described above, according to the present embodiment, the backlight emission is controlled based on the difference data having a smaller number of bits than the HDR image data without restoring the HDR image data. Specifically, the light emission luminance of the backlight is controlled based on the luminance difference data. Thereby, light emission can be controlled with a smaller processing load than when HDR image data is used. That is, according to the present embodiment, the processing load and circuit scale of the display device can be reduced as compared with the case where HDR image data is used. Even if the input range of the liquid crystal panel is narrower than the dynamic range of the HDR image data, a display image having a wide dynamic range can be obtained. Specifically, luminance that cannot be displayed when the light emission of the backlight is constant can be displayed by controlling the light emission of the backlight, so that a display image with a wide dynamic range and color gamut can be obtained.

In addition, according to the present embodiment, since image processing is performed on image data having a smaller number of bits than HDR image data, processing of a functional unit that executes image processing as compared with the case where image processing is performed on HDR image data The load and circuit scale can be reduced. Specifically, since the image processing unit 201 performs predetermined image processing on the base image data 101, the processing load and circuit scale of the image processing unit 201 are reduced as compared with the case where image processing is performed on HDR image data. be able to. Since the pixel value correction unit 203 performs a luminance range expansion process on the processing base image data 202, the processing load and circuit scale of the pixel value correction unit 203 are reduced as compared with the case where image processing is performed on the HDR image data. can do.

  Further, according to the present embodiment, the luminance difference data 1021 is corrected so that the dynamic range of the image data after the luminance range expansion processing using the conversion difference data 205 matches the dynamic range that the display image can take. Accordingly, it is possible to prevent the light emission luminance based on the difference data from exceeding the maximum value of the light emission luminance that the backlight can take and the backlight from becoming uncontrollable. Then, the luminance difference data 1021 is corrected using the conversion lookup table in which the post-conversion luminance ratio is set such that the post-conversion luminance ratio increases without increasing with respect to the increase in the pre-conversion luminance ratio. Accordingly, it is possible to reduce whiteout of a display image in a region where the light emission luminance based on the luminance difference data 1021 exceeds the maximum value of the light emission luminance that the backlight can take.

  In this embodiment, the ratio of the gradation value after the luminance area expansion process to the gradation value before the luminance area expansion process is used as the luminance ratio, but the luminance ratio is the gradation value after the luminance area expansion process. It may be the ratio of the gradation value before the luminance range expansion process. In that case, in the luminance range expansion process, the gradation value before the luminance range expansion process may be divided by the luminance ratio. Further, when the luminance ratio is low, a backlight control value corresponding to a higher emission luminance than that when the luminance ratio is high may be generated.

Note that the display device may not include the image processing unit 201. In the pixel value correction unit 203, the base image data 101 may be used instead of the processing base image data 202.
Note that the display device may not have the ratio range conversion unit 204. In the block Max Ratio detection unit 206 and the Ratio correction unit 213, the luminance difference data 1021 may be used instead of the conversion difference data 205. When the dynamic range of the HDR image data that is the original image data is less than or equal to the maximum value of the dynamic range that the display image can take, there is no problem even if the luminance difference data 1021 is used without correction. Therefore, in such a case, the processing of the ratio range conversion unit 204 becomes unnecessary.

<Example 2>
Hereinafter, a display device and a control method thereof according to Embodiment 2 of the present invention will be described.
In Example 1, the example which controls light emission of a backlight based only on difference data was demonstrated. In this embodiment, an example in which the light emission of the backlight is controlled based on the base image data and the difference data will be described. By controlling the light emission in consideration of the base image data, the light emission luminance can be reduced as compared with the case where only the difference data is used, and the power consumption of the display device can be reduced.

Since the functional configuration of the display device according to the present embodiment is the same as that of the first embodiment (FIG. 1), description thereof is omitted.
FIG. 7 is a block diagram illustrating an example of a functional configuration of the HDR processing unit according to the present embodiment.
In FIG. 7, the same functional parts as those in the first embodiment (FIG. 2) are denoted by the same reference numerals, and the description thereof is omitted.

  The block MaxRGB detection unit 301 acquires the feature amount of the processing base image data 202 in the light emission region as the second feature amount. In this embodiment, the representative value of the processing gradation value (the gradation value of the processing base image data 202) in the light emitting area is acquired as the second feature amount. Specifically, the processing gradation value (block MaxRGB302) having the largest value among the plurality of processing gradation values in the light emitting area is detected as the second feature amount. In the present embodiment, a plurality of light emitting regions exist as in the first embodiment. Therefore, the second feature amount is acquired for each light emitting area.

Note that as the block MaxRGB302, the maximum R value that is the maximum value of the R value may be acquired, the maximum G value that is the maximum value of the G value may be acquired, or the maximum that is the maximum value of the B value. The B value may be acquired, or the maximum luminance value that is the maximum luminance value may be acquired. The maximum value among the maximum R value, the maximum G value, and the maximum B value may be acquired as the block MaxRGB302.
The second feature amount is not limited to the block MaxRGB302. For example, the minimum value, the mode value, the intermediate value, the average value, and the like of the processing gradation value may be acquired as the second feature amount.

  The block MaxRGB multiplication unit 303 and the backlight luminance determination unit 305 control the light emission luminance in the light emission region according to the combination of the block MaxRatio 207 and the block MaxRGB 302.

The block MaxRGB multiplication unit 303 calculates the correction block MaxRatio 304 by multiplying the block MaxRatio 207 by the ratio of the block MaxRGB 302 to the maximum value that the block MaxRGB 302 can take. That is, the correction block MaxRatio 304 is calculated using the following Expression 7. In Equation 7, PMAX is the maximum value that the block MaxRGB 302 can take, Rmn is the block MaxRatio 207, Pmn is the block MaxRGB302, and RPmn is the correction block MaxRatio304. In the present embodiment, as in the first embodiment, the processing base image data is 8-bit image data. Therefore, PMAX is 255. In this embodiment, since there are a plurality of light emitting areas, a correction block MaxRatio 304 is calculated for each light emitting area.

RPmn = Rmn × Pmn / PMAX (Expression 7)

The method for determining the correction block MaxRatio 304 is not limited to the above method. For example, the correction block MaxRatio 304 may be determined using information (function or table) indicating a correspondence relationship between the combination of the block MaxRatio and the block MaxRGB and the correction block MaxRatio.

  The backlight luminance determining unit 305 controls the light emission luminance in the light emission region according to the correction block MaxRatio 304. Specifically, the backlight luminance determination unit 305 determines the backlight control value 108 according to the correction block MaxRatio 304, and outputs the determined backlight control value 108. The method for determining the backlight control value 108 is the same as in the first embodiment. Since the correction block MaxRatio 304 changes depending on the block MaxRGB302, the backlight control value 108 also changes depending on the block MaxRGB302. Thereby, power consumption can be reduced. For example, when the block MaxRGB302 is 0, the value corresponding to the light emission luminance 0 is determined as the backlight control value, so that power consumption can be reduced.

  In the present embodiment, the ratio correction unit 213 and the pixel value correction unit 306 generate display image data 106 based on the processing base image data 202, the conversion difference data 205, the block MaxRatio 207, and the block MaxRGB 302. Specifically, the correction difference data 214 is generated by the same method as in the first embodiment, and the display image data 106 is generated based on the correction difference data 214, the block MaxRatio 207, and the block MaxRGB302.

The pixel value correction unit 306 performs a luminance range expansion process using the correction difference data 214, a first correction process using the correction coefficient 212, and a second correction process using the block MaxRGB302.
By applying to the processing base image data 202, display image data 106 is generated. The second correction process is a process of multiplying the gradation value of the image data by the reciprocal of the maximum pixel ratio. The maximum pixel ratio is the ratio of the block MaxRGB 302 to the maximum value that the block MaxRGB 302 can take. For the pixel at the estimated position, the display pixel value is calculated by multiplying the processing pixel value by the correction luminance ratio, the correction coefficient 212, and the inverse of the maximum pixel ratio. For pixels other than the estimated position, the maximum interpolation pixel ratio is calculated by interpolation processing using the maximum pixel ratio. Then, the display pixel value is calculated by multiplying the processing pixel value by the reciprocal of the corrected luminance ratio, the interpolation correction coefficient, and the maximum interpolation pixel ratio. However, when the pixel value (multiplication value) after the enlargement process, the first correction process, and the second correction process is a value outside the input range of the liquid crystal panel 107, the multiplication value is within the input range. The display pixel value is calculated by correcting so that the value becomes. Display image data 106 is generated by calculating the display pixel value of each pixel. By multiplying the pixel value by the reciprocal of the maximum pixel ratio (or the maximum interpolation pixel ratio), it is possible to suppress a decrease in display luminance due to a decrease in light emission luminance according to the maximum pixel ratio.

Note that the processing pixel value at a position other than the estimated position may be multiplied by the reciprocal of the maximum pixel ratio of the light emitting region to which the pixel belongs without calculating the maximum interpolation pixel ratio.
The second correction process is preferably executed from the viewpoint of image quality, but may be omitted.

As described above, according to the present embodiment, the backlight emission is controlled based on the difference data and the base image data having a smaller number of bits than the HDR image data without restoring the HDR image data. Thereby, light emission can be controlled with a smaller processing load than when HDR image data is used. Even if the input range of the liquid crystal panel is narrower than the dynamic range of the HDR image data, a display image having a wide dynamic range and color gamut can be obtained.
Further, according to the present embodiment, since the backlight emission is controlled in consideration of the base image data, the backlight emission luminance can be reduced compared to the case where the base image data is not considered, and the display The power consumption of the apparatus can be reduced.

<Example 3>
Hereinafter, a display device and a control method thereof according to Embodiment 1 of the present invention will be described.
In the first and second embodiments, an example in which HDR image data is not restored has been described. In the present embodiment, an example of restoring HDR image data will be described.

Since the functional configuration of the display device according to the present embodiment is the same as that of the first embodiment (FIG. 1), description thereof is omitted.
FIG. 8 is a block diagram illustrating an example of a functional configuration of the HDR processing unit according to the present embodiment.
In FIG. 8, the same reference numerals are given to the same functional units as those in the first and second embodiments (FIGS. 2 and 7), and the description thereof is omitted.

  The HDR decoding unit 401 generates HDR image data 402 by performing luminance region expansion processing using the luminance difference data 1021 on the processing base image data 202. Specifically, the luminance difference data 1021 is luminance ratio data. Then, for each pixel, the HDR pixel value (the pixel value of the HDR image data 402) is calculated by multiplying the gradation value of the processing base image data 202 by the luminance ratio represented by the luminance difference data 1021. Thereby, HDR image data 402 is generated. In this embodiment, 32-bit HDR image data 402 is generated.

The RGB range conversion unit 403 generates restricted HDR image data 404 by reducing the dynamic range of the HDR image data 402 so as to match the dynamic range that can be taken by the image displayed on the screen. In this embodiment, the gradation value of the HDR image data 402 is converted into the gradation value of the limited HDR image data 404 using a lookup table that represents the correspondence between the gradation value before reduction and the gradation value after reduction. By doing so, restricted HDR image data 404 is generated.
FIG. 9 shows an example of a lookup table used in the reduction process for generating the restricted HDR image data 404. The horizontal axis in FIG. 9 indicates the gradation value before reduction, and the vertical axis indicates the gradation value after reduction.
It should be noted that the restriction HDR image data 404 is calculated by calculating the gradation value of the restricted HDR image data 404 from the gradation value of the HDR image data 402 using a function representing the correspondence between the gradation value before reduction and the gradation value after reduction. HDR image data 404 may be generated.

  The block MaxRGB detection unit 405 and the backlight luminance determination unit 406 control the light emission luminance of the backlight 109 based on the limited HDR image data 404.

  The block MaxRGB detection unit 405 acquires the feature amount of the restricted HDR image data 404. In the present embodiment, as in the second embodiment, the block MaxRGB302 is acquired as the feature amount. In the present embodiment, a plurality of light emitting regions exist as in the second embodiment. Therefore, a feature amount is acquired for each light emitting area.

The backlight luminance determining unit 406 controls the light emission luminance in the light emission region according to the block MaxRGB302. Specifically, the backlight luminance determination unit 406 determines the backlight control value 108 according to the block MaxRGB302, and outputs the determined backlight control value 108. Thereby, the emission luminance is controlled. In the present embodiment, the backlight luminance determination unit 406 acquires the light emission luminance corresponding to the block MaxRGB 302 from the look-up table representing the correspondence relationship between the gradation value and the light emission luminance, and the backlight control value corresponding to the acquired light emission luminance. 108 is determined. In this embodiment, since there are a plurality of light emitting areas, the backlight control value 108 is determined for each light emitting area. That is, the light emission luminance is controlled for each light emission region.
FIG. 10 shows an example of a lookup table used for determining the backlight control value 108. The horizontal axis in FIG. 10 indicates the gradation value, and the vertical axis indicates the light emission luminance.
Note that the light emission luminance corresponding to the block MaxRGB 302 may be calculated using a function representing the correspondence relationship between the gradation value and the light emission luminance, and the backlight control value 108 corresponding to the calculated light emission luminance may be determined. The backlight control value 108 corresponding to the block MaxRGB 302 may be acquired using a table or function representing the correspondence relationship between the gradation value and the backlight control value.

The correction coefficient calculation unit 407 calculates the ratio of the light emission based on the restricted HDR image data and the reference light emission as the correction coefficient 408. Specifically, the ratio between the reached luminance 210 estimated by the luminance estimation unit 209 and the reference light emission luminance is calculated as the correction coefficient 408. That is, the correction coefficient 408 is calculated using the following equation 8. In Equation 8, Lpn is the reached luminance 210, Lm is the reference emission luminance, and Gpn is the correction coefficient 408. In the present embodiment, the upper limit value of the light emission luminance is used as the reference light emission luminance. Specifically, 5000 cd / m ² is used as the reference light emission luminance. Unlike the correction coefficient 212 of the first and second embodiments, the correction coefficient 408 is a coefficient that is multiplied by the pixel value in order to reduce the change in display luminance due to the change in the emission luminance from the reference value. In this embodiment, since the reached luminance 210 is estimated for each light emitting area, the correction coefficient 408 is calculated for each light emitting area.

Gpn = Lm / Lpn (Equation 8)

Note that the reference light emission luminance is not limited to the upper limit value of the light emission luminance. The reference light emission luminance may be lower than the upper limit value of the light emission luminance.
Note that the light emission luminance corresponding to the backlight control value 108 may be used as Lm without estimating the reached luminance 210. Further, as Lpn, the reached luminance when all the light sources emit light with the reference emission luminance may be used.
Instead of the correction coefficient 408, a value obtained by subtracting the other from one of the emission luminance based on the restricted HDR image and the reference emission luminance may be calculated. Any value may be calculated as long as the value represents the difference between the light emission based on the restricted HDR image and the reference light emission.

  The pixel value correction unit 409 generates display image data 106 by correcting the gradation value of the restricted HDR image data 404 based on the correction coefficient 408. Specifically, for the pixel at the estimated position of the reached luminance 210, the pixel value for display is calculated by multiplying the limited pixel value (the pixel value of the limited HDR image data 404) by the correction coefficient 408. For pixels at positions other than the estimated position, an interpolation correction coefficient is calculated by interpolation processing using the correction coefficient 408. Then, the pixel value for display is calculated by multiplying the limited pixel value by the interpolation correction coefficient. However, when the pixel value (multiplication value) after performing the correction processing based on the correction coefficient 408 is a value outside the input range of the liquid crystal panel 107, the multiplication value is corrected to be a value within the input range. Thus, the display pixel value is calculated. For example, when the input range of the liquid crystal panel 107 is 8 bits, the multiplication value is converted to a 32-bit value, and then the lower 24 bits of the converted value are discarded, so that the multiplication value becomes an 8-bit value. It is corrected. When the input range of the liquid crystal panel 107 is 10 bits, the multiplication value is corrected to an 8-bit value by converting the multiplication value to a 32-bit value and then truncating the lower 22 bits of the converted value. The Display image data 106 is generated by calculating the display pixel value of each pixel.

  As described above, according to the present embodiment, after restoring the HDR image data, the limited HDR image data is generated by reducing the dynamic range (number of bits) of the HDR image data. Then, the light emission of the backlight is controlled based on the limited HDR image data. Thereby, light emission can be controlled with a smaller processing load than when HDR image data is used. That is, according to the present embodiment, the processing load and circuit scale of the display device can be reduced as compared with the case where HDR image data is used. Even if the input range of the liquid crystal panel is narrower than the dynamic range of the HDR image data, a display image having a wide dynamic range and color gamut can be obtained.

  Further, by using the limited HDR image data, it is possible to prevent the light emission luminance based on the HDR image data from exceeding the maximum value of the light emission luminance that the backlight can take and the backlight from becoming uncontrollable. Then, using the lookup table in which the gradation value after the reduction is set so that the gradation value after the reduction increases without being constant with respect to the increase in the gradation value before the reduction, the limited HDR image data Is generated. Accordingly, it is possible to reduce whiteout of the display image in a region where the light emission luminance based on the HDR image data exceeds the maximum value of the light emission luminance that the backlight can take.

  Further, by using the limited HDR image data, it is possible to reduce the light emission luminance of the backlight and to reduce the power consumption of the display device, compared to the case where only the difference data is used.

<Example 4>
Hereinafter, a display device and a control method thereof according to Embodiment 4 of the present invention will be described.
In this embodiment, another example of restoring HDR image data will be described.

Since the functional configuration of the display device according to the present embodiment is the same as that of the first embodiment (FIG. 1), description thereof is omitted.
FIG. 11 is a block diagram illustrating an example of a functional configuration of the HDR processing unit according to the present embodiment.
In FIG. 11, the same reference numerals are given to the same functional units as in the first to third embodiments (FIGS. 2, 7, and 8), and the description thereof is omitted.

The HDR decoding unit 501 generates restricted HDR image data 404 (enlarged image data) by performing luminance region expansion processing using the conversion difference data 205 on the processing base image data 202. The method of the luminance area expansion process is the same as that in the third embodiment.
Similar to the HDR decoding unit 401 according to the third embodiment, the HDR image data 402 may be generated as an enlarged image by performing a luminance area expansion process using the luminance difference data 1021.

The pixel value correction unit 502 generates display image data 106 based on the block MaxRatio 207 and the restricted HDR image data 404. Specifically, reduced image data obtained by reducing the dynamic range of the limited HDR image data 404 by an amount corresponding to the block MaxRatio 207 is generated as the display image data 106. In the present embodiment, display image data 106 is generated by performing reduction processing for reducing the dynamic range of the image data based on the block MaxRatio 207 and first correction processing on the limited HDR image data 404. In the present embodiment, the reduction process is a process of multiplying the gradation value of the image data by the inverse of the block MaxRatio 207.
When the pixel value (multiplication value) after the reduction process and the first correction process is a value outside the input range of the liquid crystal panel 107, the multiplication value is corrected to be a value within the input range. Thus, the display pixel value is calculated.

  As described above, according to the present embodiment, as in the first to third embodiments, the light emission of the backlight is controlled without using the HDR image data. Thereby, light emission can be controlled with a smaller processing load than when HDR image data is used. That is, according to the present embodiment, the processing load and circuit scale of the display device can be reduced as compared with the case where HDR image data is used. Even if the input range of the liquid crystal panel is narrower than the dynamic range of the HDR image data, a display image having a wide dynamic range and color gamut can be obtained.

<Example 5>
Hereinafter, a display device and a control method thereof according to Embodiment 5 of the present invention will be described.
In the first to fourth embodiments, an example in which the luminance difference data is luminance ratio data has been described. In this embodiment, an example in which the luminance difference data is a tone map will be described. The tone map is information (table or function) indicating the correspondence between the gradation value before the luminance range expansion process and the gradation value after the luminance range expansion process. The tone map that is the luminance difference data is obtained by switching the input value and the output value of the tone map used in the conversion process for converting the HDR image data into the base image data, and can also be called a reverse tone map.

なお、式９は、逆トーンマップがベース画像データのダイナミックレンジを拡大するためのデータである場合の式であるが、逆トーンマップは、色域拡大処理後の画像データのダイナミックレンジを拡大するためのデータであってもよい。 The relationship between the pixel value of the HDR image data corresponding to the original image data, the pixel value of the base image data, the value of the color difference data, and the inverse tone map is expressed by Equation 9 below. In Equation 9, (Ro, Go, Bo) is a pixel value of HDR image data, and (R, G, B) is a pixel value of base image data. T- ¹ is an inverse tone map, and (ResR, ResG, ResB) is a value of color difference data. In a method using an inverse tone map as luminance difference data, generally, residual data representing a residual value in the same format as a pixel value is used as color difference data. ResR is an R value (residual R value) represented by the color difference data, ResG is a G value (residual G value) represented by the color difference data, and ResB is a B value (residual B value) represented by the color difference data. ). Usually, one reverse tone map T ⁻¹ and residual values (RseR, ResG, ResB) for each pixel are prepared for one piece of image data.

Expression 9 is an expression when the inverse tone map is data for expanding the dynamic range of the base image data, but the inverse tone map expands the dynamic range of the image data after the color gamut expansion processing. It may be data for.

  In this embodiment, it is assumed that the R value, the G value, and the B value of the HDR image data that is the original image data are each expressed in a 32-bit floating point format. Further, the R value, G value, and B value of the base image data are each expressed in an 8-bit floating point format, and the residual R value, residual G value, and residual B value of the color difference data. Are each expressed in an 8-bit floating point format. The inverse tone map is a lookup table that inputs an 8-bit value and outputs a 32-bit value. The input value and output value of the reverse tone map have a correspondence relationship as shown in FIG. 12, for example.

Since the functional configuration of the display device according to the present embodiment is the same as that of the first embodiment (FIG. 1), description thereof is omitted.
FIG. 13 is a block diagram illustrating an example of a functional configuration of the HDR processing unit according to the present embodiment.
In FIG. 13, the same reference numerals are given to the same functional units as those in the first to fourth embodiments (FIGS. 2, 7, 8, and 11), and description thereof is omitted.

The reverse tone map 1023 is input as luminance difference data to the HDR processing unit according to the present embodiment.
Note that one reverse tone map 1023 common to the pixels may be input, or the reverse tone map 1023 for each pixel may be input. An inverse tone map 1023 for each region may be input.

  The reverse tone map range conversion unit 601 acquires the reverse tone map 1023 (first difference data). Then, the reverse tone map range conversion unit 601 corrects the reverse tone map 1023. As a result, a converted reverse tone map 602 (second difference data) having a smaller dynamic range expansion degree than the reverse tone map 1023 is generated. Specifically, the inverse tone map range conversion unit 601 reverses the tone map so that the dynamic range of the image data after the luminance range expansion processing using the converted inverse tone map 602 matches the dynamic range that the display image can take. 1023 is corrected. In this embodiment, the inverse tone map 1023 is corrected so that the dynamic range of the image data after the luminance range expansion processing using the converted inverse tone map 602 matches the maximum value of the dynamic range that can be taken by the display image.

  In this embodiment, the converted inverse tone map 602 is generated by correcting the output value represented by the inverse tone map 1023. Specifically, the output value represented by the inverse tone map 1023 is converted into the output value represented by the conversion inverse tone map 602 using the conversion lookup table. The conversion lookup table represents a correspondence relationship between an output value before conversion that is an output value before conversion (before correction) and an output value after conversion that is an output value after conversion.

  FIG. 14 shows an example of the conversion lookup table. The horizontal axis of FIG. 14 shows the output value before conversion, and the vertical axis shows the output value after conversion. When the output value represented by the reverse tone map shown in FIG. 12 is converted using the conversion lookup table shown in FIG. 14, the reverse tone map shown in FIG.

Note that the output value represented by the inverse tone map 1023 may be converted into the output value represented by the converted inverse tone map 602 using a function representing the correspondence between the output value before conversion and the output value after conversion. That is, the output value represented by the converted inverse tone map 602 may be calculated using a function.
In this embodiment, the inverse tone map 1023 is corrected so that the dynamic range of the image data after the luminance range expansion processing using the converted inverse tone map 602 matches the maximum value of the dynamic range that can be taken by the display image. Although an example has been described, the present invention is not limited to this. The dynamic range of the image data after the luminance range expansion processing using the converted inverse tone map 602 only needs to match the dynamic range that the display image can take. The dynamic range of the image data after the luminance range expansion processing using the converted inverse tone map 602 may coincide with a value lower than the maximum value of the dynamic range that can be taken by the display image.

  The block MaxRGB decoding unit 603 acquires a third feature amount based on the converted inverse tone map 602 and the block MaxRGB302. The third feature amount is a feature amount of the image data in the light emitting region, and is a feature amount after the luminance region expansion process using the converted inverse tone map 602. The block MaxRGB decoding unit 603 acquires a limited output value corresponding to the block MaxRGB302 from the converted inverse tone map 602 as a decoding block MaxRGB604 that is the third feature amount. In the present embodiment, a plurality of light emitting regions exist as in the first embodiment. Therefore, the third feature amount is acquired for each light emitting area.

  The backlight luminance determination unit 605 controls the light emission luminance in the light emission region according to the decoded block MaxRGB 604. Specifically, the backlight luminance determining unit 605 determines the backlight control value 108 according to the decoded block MaxRGB 604, and outputs the determined backlight control value 108. The method for determining the backlight control value 108 is the same as in the third embodiment.

The gradation conversion unit 606 and the residual correction unit 608 generate display image data 106 based on the base image data 101, the converted inverse tone map 602, and the correction coefficient 408.
Instead of the correction coefficient 408, a value obtained by subtracting the other from one of the light emission corresponding to the decoding block MaxRGB 604 and the reference light emission may be calculated. Any value may be used as long as it represents a difference between the light emission corresponding to the decoding block MaxRGB 604 and the reference light emission.

  The gradation conversion unit 606 generates the processing base image data 607 by performing the luminance range expansion processing using the conversion inverse tone map 602 and the correction processing based on the correction coefficient 408 on the base image data 101. The luminance range expansion process is a process for converting the gradation value of the image data in accordance with the conversion characteristics of the conversion inverse tone map 602. The correction processing method based on the correction coefficient 408 is the same as that in the third embodiment. In this embodiment, the correction process is performed after the enlargement process is performed.

Note that the pixel value after performing the luminance range expansion process and the correction process may be a value outside the input range of the liquid crystal panel 107. In that case, the pixel value of the processing base image data 607 may be calculated by correcting the pixel value after performing the luminance range expansion processing and the correction processing so as to become a value within the input range.
Note that the luminance range expansion process may be performed after the correction process.
Note that the tone conversion unit 606 may execute image processing other than the luminance range expansion processing and correction processing. For example, brightness adjustment processing, contrast adjustment processing, chroma adjustment processing, sharpness adjustment processing, and the like may be executed. The image data after the luminance range expansion process is considered to have a wider dynamic range than the image data before the luminance range expansion process. Therefore, from the viewpoint of processing load, it is preferable that the brightness adjustment process, the contrast adjustment process, the chroma adjustment process, the sharpness adjustment process, and the like are executed before the luminance range expansion process.

なお、残差補正処理を施した後の画素値が、液晶パネル１０７の入力レンジ外の値である場合には、残差補正処理を施した後の画素値を入力レンジ内の値になるように補正することにより、表示用画素値が算出されることが好ましい。 The residual correction unit 608 applies a residual correction process, which is a color gamut expansion process based on the color difference data 1022 (residual data), and a correction process based on the correction coefficient 408 to the processing base image data 607. Display image data 106 is generated. In this embodiment, the display pixel value is calculated using the following Expression 10. In Expression 10, (R607, G607, B607) is a pixel value of the processing base image data 607, and (ResR, ResG, ResB) is a value of the residual data 1022. Gpn is a correction coefficient 408, and (R106, G106, B106) are display pixel values.

If the pixel value after the residual correction processing is a value outside the input range of the liquid crystal panel 107, the pixel value after the residual correction processing is set to a value within the input range. It is preferable that the display pixel value is calculated by correcting to.

As described above, according to the present embodiment, the inverse tone map is used as the luminance difference data, but the difference data and the base image data having a smaller number of bits than the HDR image data without restoring the HDR image data. The light emission of the backlight is controlled based on the above. Thereby, light emission can be controlled with a smaller processing load than when HDR image data is used. Even if the input range of the liquid crystal panel is narrower than the dynamic range of the HDR image data, a display image having a wide dynamic range and color gamut can be obtained.
Further, according to the present embodiment, since the backlight emission is controlled in consideration of the base image data, the backlight emission luminance can be reduced compared to the case where the base image data is not considered, and the display The power consumption of the apparatus can be reduced.

  Note that the display device may not include the inverse tone map range conversion unit 601. In the block MaxRGB decoding unit 603 and the gradation conversion unit 606, the inverse tone map 1023 may be used instead of the conversion inverse tone map 602. When the dynamic range of the HDR image data that is the original image data is equal to or less than the maximum value of the dynamic range that can be taken by the display image, there is no problem even if the reverse tone map 1023 is used without correction. Therefore, in such a case, the processing of the inverse tone map range conversion unit 601 is unnecessary.

In the first to fourth embodiments, an example in which the luminance difference data is luminance ratio data has been described. However, difference data different from the luminance ratio data may be used in the configurations of the first to fourth embodiments. For example, as the luminance difference data, gradation difference data representing a difference value to be added to or subtracted from the gradation value for each pixel may be used, or a tone map may be used.
In the fifth embodiment, an example in which the luminance difference data is a tone map has been described. However, luminance difference data different from the tone map may be used in the configuration of the fifth embodiment. For example, tone difference data or brightness ratio data may be used as the brightness difference data.
In the first to fifth embodiments, the example in which the light emission luminance of the backlight is controlled using the luminance difference data is not limited to this. For example, the light emission color of the backlight may be controlled using the color difference data. Further, the light emission luminance and the light emission color of the backlight may be controlled using the luminance difference data and the color difference data.

<Other examples>
The present invention can also be implemented by a system (or a device such as a CPU or MPU) of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. The present invention can also be implemented by a method comprising steps executed by a computer of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device, for example. . For this purpose, the program is stored in the computer from, for example, various types of recording media that can serve as the storage device (ie, computer-readable recording media that holds data non-temporarily). Provided to. Therefore, the computer (including devices such as CPU and MPU), the method, the program (including program code and program product), and the computer-readable recording medium that holds the program non-temporarily are all present. It is included in the category of the invention.

105 HDR Processing Unit 107 Liquid Crystal Panel 109 Backlight 201 Image Processing Unit 204 Ratio Range Conversion Unit 206 Block MaxRatio Detection Unit 208, 305, 406, 605 Backlight Brightness Determination Unit 301, 405 Block MaxRGB Detection Unit 303 Block MaxRGB Multiplication Unit 401 HDR Decoding unit 403 RGB range conversion unit 601 Inverse tone map range conversion unit 603 Block MaxRGB decoding unit

The present invention is a control method of a display device, a display device, program, and a processor.

As one method of recording HDR image data (multi-bit image data) having a wide dynamic range or color gamut, there is a method of dividing the HDR image data into base image data and difference data, and recording the base image data and difference data. Yes (Patent Document 1). That is, as one of data formats of HDR image data, there is a format using base image data and difference data. The base image data is low-bit image data obtained by gradation-compressing HDR image data. The difference data is, for example, data representing a difference between the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image data.

The first aspect of the present invention is:
Light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
Display image data used for display on the display means is generated based on at least first data which is image data obtained by gradation-compressing original image data, and the display image data is displayed on the display means. Generating means for outputting to
Based on the second data to be used in enlargement processing for enlarging at least one of the dynamic range and color gamut of the first data, and a control means for controlling light emission of said light emitting means,
It is a display device characterized by having.

The second aspect of the present invention is:
A light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
A display device control method comprising:
Display image data used for display on the display means is generated based on at least first data which is image data obtained by gradation-compressing original image data, and the display image data is displayed on the display means. A generation step to output to
A control step of controlling light emission of the light emitting means based on second data used in an enlargement process for enlarging at least one of the dynamic range and color gamut of the first data;
A control method for a display device, comprising:

The third aspect of the present invention is:
A processing device connectable to a light emitting means, and a display means for displaying an image on a screen by modulating light from the light emitting means,
Display image data used for display on the display means is generated based on at least first data which is image data obtained by gradation-compressing original image data, and the display image data is displayed on the display means. First output means for outputting to
Second output means for outputting control information for controlling light emission of the light emitting means based on second data used in enlargement processing for enlarging at least one of the dynamic range and color gamut of the first data;
It is a processing device characterized by having.

A fourth aspect of the present invention is a program that causes a computer to execute each step of the above-described display device control method.

The difference data is data used in an enlargement process for enlarging at least one of the dynamic range and the color gamut of the image data.

Specifically, the color difference data 1020 is data used in the color gamut expansion process for expanding the color gamut of the image data , and is data representing the difference between the colors of the HDR image data and the base image data. For example, the color difference data is a color difference value (Cb value, Cr value) of the base image data and a color difference value (Cb value, Cr value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). This is data representing a color difference value which is a difference value obtained by subtracting the other from one. However, the color difference data is a color difference value (Cb value, Cr value) of the base image data and a color difference value (Cb value, Cr value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). Color ratio data representing a color ratio that is a ratio of Further, the color difference value and the color ratio may be values calculated using R value, G value, and B value instead of the color difference value. Note that the color gamut expansion processing can be said to be processing for reproducing colors that cannot be expressed by the base image data. In this embodiment, the Cb difference value and the Cr difference value of each pixel are input as the color difference data 1020. In this embodiment, the Cb difference value and the Cr difference value are each expressed in an 8-bit floating point format. The Cb difference value is a value obtained by subtracting the other from one of the Cb value of the base image data 101 and the HDR image data. The Cr difference value is a Cr value of the base image data 101 and a Cr value of the HDR image data. Is the value obtained by subtracting the other from the other.

The luminance difference data 1021 (first difference data) is data used in luminance region expansion processing for expanding the dynamic range of the image data, and represents data indicating the difference between the luminance value of the HDR image data and the luminance value of the base image data. It is. For example, the luminance difference data is a ratio between the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image data in pixel units (or in units of regions including a predetermined number of pixels). This is luminance ratio data representing the luminance ratio. That is, the luminance difference data is the ratio of the luminance value (gradation value) of the HDR image data to the luminance value (gradation value) of the base image data or the reciprocal thereof in pixel units (or an area unit composed of a predetermined number of pixels). Is luminance ratio data representing However, the luminance difference data is obtained by subtracting one from the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image data in units of pixels (or an area unit composed of a predetermined number of pixels). Data representing a luminance difference value which is a subtracted difference value may be used. Further, the luminance difference data may be luminance conversion table data (for example, a reverse tone map described later) representing a correspondence relationship between the input luminance value and the output luminance value in the luminance range expansion process. Note that the luminance range expansion processing can also be said to be processing for reproducing luminance that cannot be expressed in the base image data. In the present embodiment, as the luminance difference data 1021, the luminance value (gradation value) of the base image data and the luminance value (gradation value) of the HDR image in units of pixels (or a region unit composed of a predetermined number of pixels). Brightness ratio data representing the brightness ratio, which is a ratio, is input. In this embodiment, the luminance ratio is expressed in an 8-bit floating point format. The gradation value is a pixel value, a luminance value, or the like.

Note that the number of bits of the HDR image data, the base image data 101, the color difference data 1020, and the luminance difference data 1021 is not particularly limited.
Note that at least one of the color difference data 1020 and the luminance difference data 1021 may not be input. For example, when gradation compression is performed on HDR image data, the luminance value may change, but the color may not change. That is, the color of the HDR image data may match the color of the base image data 101. In such a case, the color difference data 1020 is not necessary. Further, when the base image data 101 is image data obtained by compressing the color gamut of the HDR image data , the brightness value of the HDR image data and the brightness value of the base image data 101 may match. In such a case, the luminance difference data 1021 is not necessary.

The backlight 109 is a light emitting unit that irradiates light to the back surface of the liquid crystal panel 107. The backlight 109 includes a light source, a drive circuit that drives the light source, an optical unit that diffuses light from the light source, and the like. In the present embodiment, the backlight 109 emits light with a light emission luminance corresponding to the backlight control value 108. Specifically, the drive circuit drives the light source so as to emit light with the light emission luminance corresponding to the backlight control value. Further, in the present embodiment, the backlight 109 is configured to be able to control the light emission luminance in units of light emission areas composed of a plurality of pixels. Specifically, the backlight 109 is a light emission luminance of the light emitting region of the multiple is configured to be individually controlled. For example, the backlight 109 has a light source for each light emitting region. The light source has one or more light emitting elements. As the light emitting element, a light emitting diode (LED), an organic EL element, a cold cathode tube, or the like can be used.
In this embodiment, an example in which a screen area is configured by a plurality of light emitting areas will be described. However, a screen area may be configured by one light emitting area.

Claims (24)

Light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
Acquisition means for acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
Control means for controlling the light emission of the light emitting means based on the difference data;
Generating means for generating display image data to be used for display on the display means based on the base image data;
A display device comprising: The difference data includes luminance difference data used in a luminance range expansion process for expanding a dynamic range of image data,
The display device according to claim 1, wherein the control unit controls the light emission luminance of the light emitting unit based on the luminance difference data. The difference data includes color difference data used in a color gamut expansion process for expanding the color gamut of image data,
The display device according to claim 1, wherein the control unit controls a light emission color of the light emission unit based on the color difference data. The light emitting means is configured to be capable of controlling light emission in a light emitting area unit composed of a plurality of pixels.
The control means includes
Obtaining the feature amount of the difference data in the light emitting region as a first feature amount;
Controlling light emission in the light emitting region according to the first feature amount;
The said production | generation means produces | generates the said display image data based on the said base image data, the said difference data, and the said 1st feature-value, The any one of Claims 1-3 characterized by the above-mentioned. Display device. The generating means includes
Based on the difference data and the first feature value, generate corrected difference data corresponding to the difference between the difference data and the first feature value,
The display device according to claim 4, wherein the display image data is generated by performing an enlargement process using the correction difference data on the base image data. The difference data includes luminance ratio data representing a luminance ratio for each pixel, which is a ratio between a gradation value before the enlargement process and a gradation value after the enlargement process,
The first feature amount is a representative value of a luminance ratio represented by the luminance ratio data in the light emitting region,
The display device according to claim 5, wherein the generation unit generates the correction difference data by dividing a luminance ratio represented by the luminance ratio data by the first feature amount. The generating means includes
By performing enlargement processing using the difference data on the base image data, generating enlarged image data,
Based on the first feature amount and the enlarged image data, reduced image data obtained by reducing at least one of the dynamic range and the color gamut of the enlarged image data by an amount corresponding to the first feature amount is used as the display image data. The display device according to claim 4, wherein the display device is generated as follows. The difference data includes luminance ratio data representing a luminance ratio for each pixel, which is a ratio between a gradation value before the enlargement process and a gradation value after the enlargement process,
The first feature amount is a representative value of a luminance ratio represented by the luminance ratio data in the light emitting region,
The display device according to claim 7, wherein the generation unit generates the reduced image data by multiplying a gradation value of the enlarged image data by an inverse of the first feature amount. The light emitting means is configured to be capable of controlling light emission in a light emitting area unit composed of a plurality of pixels.
The control means includes
Obtaining the feature amount of the difference data in the light emitting region as a first feature amount;
Acquiring the feature amount of the base image data in the light emitting region as a second feature amount;
Controlling light emission in the light emitting region according to a combination of the first feature value and the second feature value,
The said production | generation means produces | generates the said display image data based on the said base image data, the said difference data, the said 1st feature-value, and the said 2nd feature-value. The display device according to any one of the above. The generating means includes
Based on the difference data and the first feature value, generate corrected difference data corresponding to the difference between the difference data and the first feature value,
The display device according to claim 9, wherein the display image data is generated based on the base image data, the correction difference data, and the second feature amount. The difference data includes luminance ratio data representing a luminance ratio for each pixel, which is a ratio between a gradation value before the enlargement process and a gradation value after the enlargement process,
The first feature amount is a representative value of a luminance ratio represented by the luminance ratio data in the light emitting region,
The second feature amount is a representative value of gradation values of the base image data in the light emitting region,
The generating means includes
By dividing the luminance ratio represented by the luminance ratio data by the first feature amount, the correction difference data is generated,
A process of correcting the gradation value of the image data in accordance with the luminance ratio represented by the correction difference data, and the reciprocal of the ratio of the second feature quantity with respect to the maximum value of the second feature quantity can be calculated. The display device according to claim 10, wherein the display image data is generated by performing a process of multiplying a tone value on the base image data. The difference data includes luminance ratio data representing a luminance ratio for each pixel, which is a ratio between a gradation value before the enlargement process and a gradation value after the enlargement process,
The first feature amount is a representative value of a luminance ratio represented by the luminance ratio data in the light emitting region,
The second feature amount is a representative value of gradation values of the base image data in the light emitting region,
The control means controls light emission luminance in the light emitting region according to a value obtained by multiplying the first feature amount by a ratio of the second feature amount to a maximum value that the second feature amount can take. The display device according to any one of claims 9 to 11. The light emitting means is configured to be capable of controlling light emission in a light emitting area unit composed of a plurality of pixels.
The control means includes
Acquiring the feature amount of the base image data in the light emitting region as a second feature amount;
Based on the difference data and the second feature amount, obtain a third feature amount that is the feature amount of the image data in the light emitting region and is the feature amount after the enlargement process using the difference data;
Controlling light emission in the light emitting region according to the third feature amount;
The generation unit generates the display image data based on the base image data, the difference data, and a difference between light emission corresponding to the third feature amount and reference light emission. Item 4. The display device according to any one of Items 1 to 3. The generation means includes: an enlargement process using the difference data; and a process of correcting a gradation value of image data based on a difference between light emission corresponding to the third feature amount and reference light emission. The display device according to claim 13, wherein the display image data is generated by applying the data. The difference data includes a tone map representing a correspondence relationship between a gradation value before the enlargement process and a gradation value after the enlargement process,
The second feature amount is a representative value of gradation values of the base image data in the light emitting region,
The display device according to claim 13 or 14, wherein the control unit acquires, from the difference data, a gradation value after enlargement processing corresponding to the second feature amount as the third feature amount. . The acquisition unit corrects the first difference data input to the display device, thereby generating second difference data having a smaller degree of enlargement of the enlargement process than the first difference data as the difference data. The display device according to claim 1, wherein: The enlargement process includes a luminance range expansion process for expanding a dynamic range of image data,
The acquisition unit corrects the first difference data so that a dynamic range of the image data after the enlargement process using the second difference data matches a dynamic range that can be taken by the image displayed on the screen. The display device according to claim 16. Light emitting means;
Display means for displaying an image on a screen by modulating light from the light emitting means;
Acquisition means for acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
Enlarging means for generating HDR image data by applying an enlargement process using the difference data to the base image data;
Reduction means for generating restricted HDR image data by reducing the dynamic range of the HDR image data so as to match the dynamic range that can be taken by the image displayed on the screen;
Control means for controlling light emission of the light emitting means based on the restricted HDR image data;
The restricted HD based on the difference between the light emission based on the restricted HDR image data and the reference light emission.
Correcting means for generating display image data used for display on the display means by correcting the gradation value of the R image data;
A display device comprising: The light emitting means is configured to be capable of individually controlling light emission of a plurality of light emitting areas constituting the area of the screen,
The display device according to claim 1, wherein the control unit controls light emission for each light emitting region. The acquisition unit generates second base image data as the base image data by performing predetermined image processing on the first base image data input to the display device. The display device according to any one of the above. The acquisition means acquires base image data and difference data for each frame,
The control means includes
Performing a process of controlling the light emission of the light emitting means for the first frame of still image data and each frame of moving image data;
The display device according to any one of claims 1 to 20, wherein processing for controlling light emission of the light emitting unit is omitted for the second and subsequent frames of still image data. Light emitting means;
A display means for displaying an image on a screen by modulating light from the light emitting means, and a control method for a display device,
An acquisition step of acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
A control step of controlling light emission of the light emitting means based on the difference data;
Based on the base image data, a generating step for generating display image data used for display on the display means;
A control method for a display device, comprising: Light emitting means;
A display means for displaying an image on a screen by modulating light from the light emitting means, and a control method for a display device,
An acquisition step of acquiring base image data and difference data used in an enlargement process for enlarging at least one of a dynamic range and a color gamut of the image data;
An enlargement step for generating HDR image data by applying an enlargement process using the difference data to the base image data;
A reduction step of generating restricted HDR image data by reducing the dynamic range of the HDR image data so as to match the dynamic range of the image displayed on the screen;
A control step of controlling light emission of the light emitting means based on the limited HDR image data;
Correction for generating display image data used for display on the display unit by correcting the gradation value of the limited HDR image data based on the difference between the emission based on the limited HDR image data and the reference emission. Steps,
A control method for a display device, comprising:   24. A program for causing a computer to execute each step of the method for controlling a display device according to claim 22 or 23.

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