JP6108798B2 - Display device and control method thereof - Google Patents

Description

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

  In recent years, in a liquid crystal display device, a technology for controlling the light emission luminance of a backlight for each divided region obtained by dividing a screen has been developed. Such control is called local dimming (local dimming) control.

  In proportion to the decrease in the light emission luminance of the backlight, the leakage of the backlight light from the liquid crystal panel (light from the backlight) decreases. In particular, leakage of backlight light is reduced in an area where a dark part (for example, a black part) of an image is displayed. Therefore, the black level that can be expressed can be lowered as the light emission luminance of the backlight is lowered.

  In the local dimming control, in consideration of the above-described features, the luminance of the backlight in the divided area where the bright image is displayed is increased, or the luminance of the backlight in the divided area where the dark image is displayed is reduced. To do. Thereby, the contrast of the display image (image displayed on the screen) can be improved. Further, by performing local dimming control, the light emission amount of the backlight can be optimized, so that power consumption can be reduced.

  Specifically, for each divided region, the feature amount (for example, maximum gradation value) of the image displayed in the divided region is acquired. For each divided area, based on the maximum gradation value, the higher the maximum gradation value, the higher the light emission luminance is determined. As a result, a high value is set as the light emission luminance of the divided region where an image having a high gradation value (bright image) is displayed, and the light emission luminance of the divided region where an image having a low gradation value (dark image) is displayed. Value is set. Further, for each divided area, the image displayed in the divided area is corrected in accordance with the light emission luminance of the divided area. For example, the image (image data) is corrected so that the display brightness of the brightest part does not change. Such local dimming control is disclosed in Patent Document 1, for example.

JP 2005-258403 A

  By the way, in general, an image editing application or an image display application installed in a personal computer, a smartphone, or the like has a function of enlarging and displaying an original image.

  In the above-described prior art, images displayed in one divided region are different between when an original image is displayed and when an enlarged image obtained by enlarging the original image is displayed. For this reason, when displaying an original image and when displaying an enlarged image, the feature values (image feature values) for each divided region are different from each other, and the light emission luminance of the backlight for each divided region is different from each other. The contrast (representable black level) depends on the light emission luminance for each divided region. Therefore, the contrast is different between the case where the original image is displayed and the case where the enlarged image is displayed.

For example, as shown in FIG. 11, a sweep image in which a gradation value linearly changes from black (gradation value 0) to white (gradation value 255) from the left end to the right end is displayed at the same magnification. Consider a case where a dark area 1101 of an image is displayed at a magnification of 3 times. The maximum gradation value in the two divided areas 1102 in which a part (partial area) of the dark area 1101 is enlarged and displayed is lower than the maximum gradation value in the divided area 1103 in which the partial area is displayed at the same magnification. Therefore, the light emission luminance of the divided area 1102 is lower than the light emission luminance of the divided area 1103. As a result, in the enlarged display, the black reproducibility in the partial area is improved (contrast in the partial area is increased) as compared with the same magnification display.
Thus, the contrast is different between the case where the original image is displayed and the case where the enlarged image is displayed.

  Such a difference in contrast gives an uncomfortable feeling to the user, and is not preferable. In particular, when the displayed image is displayed with the enlargement ratio changed (when the same image is displayed with the enlargement ratio changed), the difference in contrast is easily perceived by the user, giving the user a sense of incongruity.

  The present invention can reduce a difference in contrast between when an original image is displayed on a display device that performs local dimming control based on an image to be displayed and when an enlarged image obtained by enlarging the original image is displayed. The purpose is to provide.

The display device of the present invention includes:
Display means for displaying an image on the screen;
A plurality of light-emitting means corresponding to a plurality of divided areas obtained by dividing the screen and capable of individually controlling the light emission luminance;
Control means for controlling the light emission luminance of each light emitting means;
With
When displaying an original image, a partial original image that is a part of the original image is displayed in each divided region,
When displaying an enlarged image obtained by enlarging the original image, a partial enlarged image that is a part of the enlarged image is displayed in each divided region,
The control means includes
To display the original image, a process of controlling the light emission luminance of the light emitting means corresponding to the divided region based on the partial original image displayed on the divided regions is performed for each divided area,
To display the enlarged image, is determined on the basis of the partial original image including a light emission luminance of the light emitting means corresponding to the divided region, the portion corresponding to the enlarged partial image displayed on the divided regions The difference between the emission luminance and the emission luminance determined based on the partial enlarged image displayed in the divided area and the partial enlarged image displayed in the divided area
Processing for controlling the light emission luminance of the light emitting means corresponding to the divided region is performed for each divided region so as to be reduced from the difference from the light emission luminance determined based on the partial original image including a part < It is characterized by the above.

The display device control method of the present invention includes:
A display device control method comprising: display means for displaying an image on a screen; and a plurality of light emitting means corresponding to a plurality of divided areas obtained by dividing the screen and capable of individually controlling light emission luminance.
A control step of controlling the light emission brightness of each light emitting means;
When displaying an original image, a partial original image that is a part of the original image is displayed in each divided region,
When displaying an enlarged image obtained by enlarging the original image, a partial enlarged image that is a part of the enlarged image is displayed in each divided region,
In the control step,
To display the original image, processing for controlling the light emission luminance of the light emitting means corresponding to the divided region based on the partial original image displayed on the divided areas is performed for each divided area,
To display the enlarged image, is determined on the basis of the partial original image including a light emission luminance of the light emitting means corresponding to the divided region, the portion corresponding to the enlarged partial image displayed on the divided regions The partial source including the portion corresponding to the light emission luminance determined based on the partial enlarged image displayed in the divided region and the partial enlarged image displayed in the divided region. Processing for controlling the light emission luminance of the light emitting means corresponding to the divided region is performed for each divided region so as to be reduced from the difference from the light emission luminance determined based on the image. Features.

  According to the present invention, it is possible to reduce a difference in contrast between when an original image is displayed on a display device that performs local dimming control based on an image to be displayed and when an enlarged image obtained by enlarging the original image is displayed. it can.

Schematic diagram illustrating an example of a liquid crystal module according to the first embodiment. FIG. 1 is a block diagram illustrating an example of a configuration of a liquid crystal display device according to a first embodiment. 7 is a flowchart illustrating an example of a process flow of the liquid crystal display device according to the first embodiment. The figure which shows an example of the original image which concerns on Example 1, and an original image feature-value FIG. 10 is a diagram illustrating an example of an original image, a display image, and a display image feature amount according to the first embodiment. FIG. 10 is a diagram illustrating an example of a feature amount correction reference generation method according to the first embodiment. The flowchart which shows an example of the flow of a process of S306 of FIG. The figure which shows an example of the feature-value before and behind correction based on Example 1, and a feature-value correction reference | standard The figure which shows an example of the effect of Example 1 FIG. 6 is a block diagram illustrating an example of a configuration of a liquid crystal display device according to a second embodiment. The figure which shows an example of the subject of conventional technology

<Example 1>
Hereinafter, a display device and a control method thereof according to Embodiment 1 of the present invention will be described.
In this embodiment, an example of a liquid crystal display device having a function of directly decoding and displaying image format data representing JPEG will be described. In the present embodiment, an example will be described in which the display resolution of the liquid crystal display device is 1920 pixels in the horizontal direction × 1080 pixels in the vertical direction, and the gradation value range of the image data is 8 bit gradations (0 to 255).
The display device is not limited to a liquid crystal display device. The present invention can be applied to any display device having an independent light source. Further, the display device is not limited to a device having only a function for displaying an image. The display device may be a portable device (for example, a smartphone or a digital camera) having an image display function.

FIG. 1 is a schematic diagram illustrating an example of a liquid crystal module according to the present embodiment.
In the example of FIG. 1, the liquid crystal module 100 includes a backlight 101, a first light diffusing plate 102, a liquid crystal panel 103, a color filter 104, and a second light diffusing plate 105.

The backlight 101 (light emitting unit) has a configuration capable of controlling the light emission luminance (degree of brightness) for each divided region obtained by dividing the screen. That is, the backlight 101 has a configuration capable of local dimming control.
Specifically, the backlight 101 has a plurality of light emitting blocks 107 corresponding to a plurality of divided regions. One light emitting block 107 has a predetermined number of light sources 106 arranged in a matrix. In this embodiment, the light source 106 is a white LED. The plurality of light sources 106 included in the backlight 101 (the plurality of light sources 106 included in the plurality of light emission blocks 107) are arranged at equal intervals. The light emission luminance of the backlight 101 can be controlled for each light emission block 107.
In this embodiment, the backlight 101 has 15 light-emitting blocks 107 of 3 rows and 5 columns in order to easily explain the configuration. One light-emitting block 107 has a total of 25 light sources 106 in 5 rows and 5 columns.

Note that the configuration of the backlight 101 is not limited to the above configuration. The backlight 101 may have any configuration as long as local dimming control is possible.
The number of the light emitting blocks 107 may be more or less than 15.
One light-emitting block may have more or less than 25 light sources (one light-emitting block may have one light source 106).
The light source 106 may not be a white LED. For example, a plurality of colored LEDs (red LED, green LED, blue LED, yellow LED, etc.) may be used so that the light from one light emitting block 107 becomes white light. A cold cathode tube or the like may be used as the light source 106.

  The first light diffusion plate 102 diffuses light from the backlight 101 and reduces unevenness of light from the backlight 101.

  The liquid crystal panel 103 is a display panel that transmits light from the backlight 101 and displays an image on a screen. One pixel of the liquid crystal panel 103 includes three sub-pixels of an R sub-pixel, a G sub-pixel, and a B sub-pixel, and the light transmittance is controlled for each sub-pixel.

  The color filter 104 is a filter that transmits only light in a specific wavelength band among light transmitted through the liquid crystal panel 103. Specifically, the color filter 104 is provided for each subpixel. For the R sub-pixel, a color filter that transmits only red (R) light is provided. A color filter that transmits only green (G) light is provided for the G subpixel. A color filter that transmits only blue (B) light is provided for the B subpixel.

  The second light diffusion plate is a diffusion plate for widening the viewing angle of the display image (image displayed on the screen), and diffuses the light transmitted through the color filter 104.

FIG. 2 is a block diagram illustrating an example of the configuration of the display device (liquid crystal display device) according to the present embodiment. In FIG. 2, functional units mainly related to image display processing are illustrated, and other functional units are omitted.
In the example of FIG. 2, the liquid crystal display device 200 includes a decoding unit 201, an original image holding unit 202, an equal-size image generation unit 203, an original image feature amount acquisition unit 204, a display image generation unit 205, and a display image feature amount acquisition. A display unit 206, a display image correction unit 207, a feature amount holding unit 208, a control unit 209, a user operation reception unit 210, a backlight controller 211, a backlight 101, a liquid crystal controller 212, and a liquid crystal panel 103.

In response to an image file acquisition instruction from the control unit 209, the decoding unit 201 acquires an image file to be displayed (an image file of an original image of the image to be displayed), and decodes the acquired image file. Then, the image data obtained by decoding (original image of the image to be displayed) is output to the original image holding unit 202. In this embodiment, a JPEG file is acquired, and the acquired JPEG file is decoded into image data in YUV format.
Note that the image file may be acquired from the outside, or may be acquired from a storage unit (not shown) included in the liquid crystal display device 200.
The original image holding unit 202 holds the original image obtained by the decoding unit 201.

The same size image generation unit 203 reads the original image from the original image holding unit 202 and generates an equal size image that is equal to the display image when the original image is displayed. In this embodiment, when an original image is displayed, the original image is displayed on the entire screen of 1920 pix × 1080 pix. When the size of the original image is smaller than the size of the screen, the same size image is generated by enlarging the original image. When the size of the original image is larger than the size of the screen, the original image is generated by reducing the original image. The generated same size image is output to the original image feature amount acquisition unit 204. When the size of the original image matches the size of the screen, the original image is an equal-size image. If the aspect ratio of the screen and the aspect ratio of the original image are different, an additional image (for example, a black strip image) is added to the top and bottom or the left and right of the original image so that the aspect ratio of the original image matches the screen aspect. After that, the size may be adjusted.
When the size of the original image is smaller than the size of the screen, the same size image may be generated by adding the additional image to the original image so that the size matches the size of the screen. When the size of the original image is larger than the size of the screen, the same size image may be generated by extracting a part of the original image so that the size matches the size of the screen.

Assuming that the original image is displayed, the original image feature amount acquisition unit 204 acquires, for each divided region, a feature amount (original image feature amount; second feature amount) of the original image displayed in the divided region. Specifically, the same size image generated by the same size image generation unit 203 is divided into a plurality of divided images corresponding to a plurality of divided regions. Then, the original image feature amount is detected for each divided image, and the original image feature amount for each divided image (for each divided region) is output to the feature amount holding unit 208. In the present embodiment, it is assumed that a maximum luminance value (maximum value of Y value) is acquired (detected) as a feature amount.
Note that the feature amount is not limited to the maximum luminance value. Depending on the control algorithm that implements local dimming control, the feature amount may be an average value of brightness, a mode value, a histogram, or the like.

The display image generation unit 205 acquires an original image from the original image holding unit 202 in accordance with an instruction from the control unit 209, and generates a display image using the acquired original image. Specifically, the display image generation unit 205 has an instruction to display an original image (original image display instruction), an instruction to display an enlarged image obtained by enlarging the original image (enlarged image display instruction), and the like from the control unit 209. Entered. As an enlarged image display instruction, for example, information indicating an enlargement area (enlargement area) or an enlargement ratio in the original image is input. When an original image display instruction is input, the same image as the same size image is generated as a display image. When an enlarged image display instruction is input, an image of a region to be enlarged and displayed is extracted from the original image, and a 1920 pix × 1080 pix display image is generated by performing scaling processing on the extracted image. Note that scaling processing may be performed on the original image, and an image of 1920 pix × 1080 pix may be extracted as a display image from the image after the scaling processing. The generated display image is output to the display image feature amount acquisition unit 206 and the display image correction unit 207.
In the case of a configuration in which an additional image is added to the original image so that the size matches the screen size when the original image is displayed, the display image is generated when the enlarged image is displayed. The entire area of the original image may be designated as the display area.

The display image feature quantity acquisition unit 206 acquires the feature quantity (display image feature quantity) of the image displayed in each divided area for each divided area. When displaying an enlarged image obtained by enlarging the original image, the feature amount (first feature amount) of the enlarged image displayed in the divided region is acquired for each divided region. Specifically, the display image feature quantity acquisition unit 206 divides the display image generated by the display image generation unit 205 into a plurality of divided images corresponding to a plurality of divided regions. The display image feature amount acquisition unit 206 detects the feature amount of the display image (display image feature amount; maximum luminance value) for each divided region, and displays the display image feature for each divided image (for each divided region). The amount is output to the feature amount holding unit 208.

The feature amount holding unit 208 temporarily stores the original image feature amount acquired (detected) by the original image feature amount acquisition unit 204 and the display image feature amount acquired by the display image feature amount acquisition unit 206. Hold.
When displaying the original image (same size display), the display image generated by the display image generation unit 205 matches the same size image generated by the equal size image generation unit 203. Therefore, when displaying an original image, the original image feature amount matches the display image feature amount.

  The user operation receiving unit 210 receives a signal generated when the user operates the remote control or the main body operation panel. The user operation receiving unit 210 generates operation information representing the content of the operation of the display device by the user according to the received signal. Then, the user operation reception unit 210 outputs the generated operation information to the control unit 209. For example, the user operation reception unit 210 receives an operation for selecting an image file to be displayed, an operation for displaying an original image (equal size image), an operation for displaying an enlarged image, and the like, and outputs operation information to the control unit 209. The operation for displaying an enlarged image includes an operation for selecting an area to be enlarged and an operation for selecting an enlargement ratio.

The control unit 209 controls each function unit according to operation information from the user operation reception unit 210 (outputs an instruction to each function unit).
For example, when there is an operation for selecting an image file to be displayed, the control unit 209 outputs an image file acquisition instruction for acquiring and decoding the image file to be displayed to the decoding unit 201. Image size information representing the size of the original image obtained by decoding is added to the original image and can be acquired from the original image holding unit 202.
When there is an operation for displaying an original image (magnified image) or an operation for displaying an enlarged image, the control unit 209 displays an original image display instruction and an enlarged image display instruction for the display image feature quantity acquisition unit 206. Output to.
Further, the control unit 209 controls the emission luminance of the backlight 101 for each divided region based on the feature amount for each divided region. Specifically, the control unit 209 reads the original image feature amount and the display image feature amount for each divided region from the feature amount holding unit 208, and based on the original image feature amount and the display image feature amount for each divided region. The light emission luminance value for each divided region (for each light emission block 107) is determined. Then, the control unit 209 outputs light emission luminance information representing the light emission luminance value for each light emission block 107 to the display image correction unit 207 and the backlight controller 211. Details of the method of determining the light emission luminance value will be described in detail later.
In this embodiment, the display image feature quantity is corrected, and the display image feature quantity after the correction process is adopted as the light emission luminance. However, the present invention is not limited to this. A value different from the display image feature value after the correction process may be calculated as the light emission luminance using the display image feature value after the correction process.

The display image correction unit 207 corrects the display image based on the light emission luminance information (the light emission luminance value for each divided region) output from the control unit 209 so that an image with accurate luminance and color is displayed. To do.
Specifically, the luminance value is corrected using the following Expression 1 for each pixel of the display image (display image before correction) input to the display image correction unit 207. YinN is a luminance value (input luminance value) before correction of the pixel to be processed. Lmax is the light emission luminance value of the divided area where the pixel to be processed is displayed (belongs to). YoutN is a corrected luminance value (output luminance value) of the pixel to be processed.
YoutN = YinN × (255 / Lmax) (Formula 1)
That is, the histogram expansion of the input luminance value YinN is performed so that the maximum luminance value (the maximum value of the output luminance value YoutN) is 255 for each divided region.
In Expression 1, the input luminance value YinN and the output luminance value YoutN are in a proportional relationship, but the relationship between the input luminance value YinN and the output luminance value YoutN is not limited to this. The output luminance value YoutN may be calculated so that the output luminance value YoutN increases exponentially with respect to the increase in the input luminance value YinN. As a method of correction processing by the display image correction unit 207, a technique used in conventional local dimming control can be appropriately used.
The display image correction unit 207 performs color matrix conversion of the corrected display image format from the YUV format to the RGB format, and the display image after the color matrix conversion is input to the liquid crystal controller 212 as a corrected image (corrected image data). Output.

The backlight controller 211 calculates the light emission amount for each divided region (for each light emission block 107) based on the light emission luminance information output from the control unit 209. Then, the backlight controller 211 turns on the light source 106 included in the light emission block 107 for each light emission block 107 with the calculated light emission amount.
Specifically, the light emission amount is calculated for each light emission block 107 using the following Equation 2. Lmax is the light emission luminance value of the light emission block 107 to be processed (the divided area corresponding to the light emission block 107 to be processed). Bmax is the maximum light emission amount (the maximum value of the light emission amount that can be set). B is a light emission amount to be set (that is, a calculation result).
B = Bmax × (Lmax / 255) (Expression 2)
In Expression 2, the light emission luminance value Lmax and the light emission amount B are in a proportional relationship, but the relationship between the light emission luminance value Lmax and the light emission amount B is not limited to this. The light emission amount B may be calculated so that the light emission amount B increases exponentially with respect to the increase in the light emission luminance value Lmax. As a lighting method of the backlight 101 by the backlight controller 211, a technique performed in the conventional local dimming control can be appropriately used.

  The liquid crystal controller 212 drives each subpixel of the liquid crystal panel 103 so that the transmittance becomes a transmittance according to the corrected image from the display image correcting unit 207.

A flow of processing of the liquid crystal display device according to the present embodiment (processing flow from detection of the source image feature amount and display image feature amount to determination of the light emission luminance value) will be described with reference to the flowchart of FIG.
In the following, an example in which an enlarged image is displayed will be described. However, the same processing as in the case of displaying an enlarged image may be performed when an original image (same size image) is displayed.
It is assumed that the decoding of the image file to be displayed and the recording of the original image in the original image holding unit 202 have already been completed.

  First, in S301, the equal-size image generation unit 203 reads the original image held in the original image holding unit 202, and generates an equal-size image equal to the display image when the read original image is displayed. The same size image is output to the original image feature amount acquisition unit 204.

  Next, in S <b> 302, the original image feature quantity acquisition unit 204 divides the equal-size image generated by the equal-size image generation unit 203 into a plurality of divided images corresponding to a plurality of divided regions. Then, the original image feature amount acquisition unit 204 detects the maximum luminance value as the original image feature amount for each divided image. The original image feature quantity for each divided image (each divided area) is held by the feature quantity holding unit 208.

A specific example of the process of S302 will be described with reference to FIG.
FIG. 4 is a diagram illustrating an example of an original image (same size image) and an original image feature amount.
In the example of FIG. 4, the screen is divided (divided) into 15 divided regions of 3 rows and 5 columns. In the figure, X1 to X5 indicate horizontal positions of the divided areas, and Y1 to Y3 indicate vertical positions of the divided areas. The aspect ratio of the original image shown in FIG. 4 is 16 in the horizontal direction: 9 in the vertical direction (the size of the original image is 1920 pix × 1080 pix). The original image shown in FIG. 4 is a sweep image in which the gradation value changes linearly from black (luminance value 0) to white (luminance value 255) from the upper left to the lower right. The numbers shown at the four corners of the divided area indicate the luminance values of the pixels at the four corners of the divided area. In the case of the original image shown in FIG. 4, the luminance value of the pixel at the lower right corner of the divided image is detected as the maximum luminance value (original image feature amount) for each divided image.

  Subsequent to S302, in S303, the display image generation unit 205 acquires an image of an area to be enlarged and displayed in the original image from the original image holding unit 202 in response to an enlarged image display instruction from the control unit 209. Then, the display image generation unit 205 generates a display image by performing a scaling process on the acquired image so that the size is 1920 pix × 1080 pix. The generated display image is output to the display image feature amount acquisition unit 206 and the display image correction unit 207.

  In step S304, the display image feature amount acquisition unit 206 divides the display image generated by the display image generation unit 205 into a plurality of divided images corresponding to a plurality of divided regions. Then, the display image feature amount acquisition unit 206 detects the maximum luminance value as the display image feature amount for each divided image. The display image feature amount for each divided image (each divided region) is held by the feature amount holding unit 208.

A specific example of the processing of S303 and S304 will be described with reference to FIG.
FIG. 5 is a diagram illustrating an example of an original image, a display image (enlarged image), and a display image feature amount. FIG. 5 shows an example in which a specific area (for example, an area designated by the user) in the original image is enlarged and displayed at a double magnification. In the example of FIG. 5, the divided areas and the original image are the same as those in FIG.
In the example of FIG. 5, in the process of S303, an image of the area 501 in the original image is acquired. Then, the scaling process is performed on the image in the region 501 so that the horizontal size and the vertical size are each doubled. Thereby, a display image is generated. At this time, as shown in FIG. 5, the display image is a sweep image in which the gradation value linearly changes from gray having a gradation value of 50 to gray having a gradation value of 176 from upper left to lower right. The numbers shown at the four corners of the divided area indicate the luminance values of the pixels at the four corners of the divided area.
In the example of FIG. 5, in the process of S304, for each divided image obtained by dividing the display image, the luminance value of the pixel in the lower right corner of the divided image is detected as the maximum luminance value (display image feature amount). The

  In step S <b> 305, the control unit 209 generates a feature amount correction reference from the original image feature amount and enlarged region information representing an enlarged display region (enlarged region) in the original image. The enlarged area information is generated according to a user operation for designating an enlarged area, or is generated when an enlarged image is generated as a display image. The feature amount correction reference is derived for each divided region from the original image feature amount of the divided region where at least a part of the original image corresponding to the enlarged image displayed in the divided region is displayed.

A method for generating the feature amount correction reference will be described in detail with reference to FIG.
As indicated by reference numeral 601, the control unit 209 determines an area to be enlarged and displayed from the original image in accordance with the enlarged area information, and displays a plurality of areas having the same number and the same arrangement as the divided areas. Into a plurality of corresponding enlarged display divided regions). In FIG. 6, a region obtained by dividing a solid line (thick line) by a broken line is a divided region, and a region obtained by dividing a solid line 601 (thin line) by a one-dot chain line is an enlarged display divided region.
Then, for each enlarged display divided region, the control unit 209 divides the feature amount range defined by the original image feature amount of the divided region including at least a part of the enlarged display divided region corresponding to the enlarged display divided region. It is generated as a feature amount correction reference for the region.
Specifically, when one divided region includes all of the one enlarged display divided region, the original image feature amount of the divided region is used as a feature amount correction reference for the divided region corresponding to the enlarged display divided region. The When there are a plurality of divided regions including a part of one enlarged display divided region, the feature amount range from the minimum value to the maximum value of the original image feature amount of the plurality of divided regions is the enlarged display divided region. Is used as a feature amount correction reference for the divided region corresponding to.
For example, the enlarged display areas corresponding to the divided areas (X1 (horizontal position), Y1 (vertical position)) are divided areas (X1, Y1), (X2, Y1), (X1, Y2), (X2, Y2). The original image feature amounts of the divided areas (X1, Y1), (X2, Y1), (X1, Y2), (X2, Y2) are 66, 92, 108, and 134. Therefore, the feature amount correction reference for the divided region (X1, Y1) is the minimum value 66 to the maximum value 134.
The enlarged display area corresponding to the divided area (X2, Y1) overlaps with the divided areas (X1, Y2), (X2, Y2). The original image feature amounts of the divided areas (X1, Y2) and (X2, Y2) are 108 and 134. Therefore, the feature amount correction reference for the divided regions (X1, Y2) is the minimum value 108 to the maximum value 134.
The enlarged display area corresponding to the divided area (X2, Y2) is included only in the divided area (X2, Y2). The original image feature amount of the divided area (X2, Y2) is 134. Therefore, the feature amount correction reference for the divided region (X2, Y2) is 134.
The feature amount correction reference is similarly determined for other divided regions. As a result, as shown in FIG. 6, a feature amount correction reference for each divided region is obtained.

  Next to S305, in S306, the control unit 209 corrects the display image feature amount for each divided region based on the feature amount correction reference. In this embodiment, for each divided area, the difference from the original image feature amount of the divided area where at least a part of the original image corresponding to the enlarged image (display image) displayed in the divided area is displayed. Correction processing for correcting the display image feature value is performed so as to be reduced. Then, the control unit 209 controls the light emission luminance of the backlight 101 for each divided region based on the corrected feature value for each divided region (the display image feature value after the correction process). That is, the light emission luminance value for each light emission block 107 is determined based on the corrected feature value for each divided region.

  The process of S306 will be described in more detail using the flowchart of FIG. 7 and the relationship diagram of FIG. FIG. 7 is a flowchart illustrating an example of a process flow for one divided region, and the process illustrated in FIG. 7 is performed for each divided region.

First, in step S <b> 701, a display image feature amount (pre-correction feature amount) before correction of a processing target divided region (target divided region) is compared with a feature amount correction reference. If the pre-correction feature value is a value within the feature value range represented by the feature value correction reference, the process proceeds to S702. If the pre-correction feature value is a value outside the feature value range represented by the feature value correction reference, the process proceeds to S703.
As described above, when all of the enlarged display areas corresponding to the target divided area are included in one divided area, one original image feature value is used as a feature quantity correction reference. In such a case, when the pre-correction feature value matches the value represented by the feature value correction reference, the pre-correction feature value is a value within the feature value range represented by the feature value correction reference. Equivalent to. The case where the pre-correction feature value does not match the value represented by the feature value correction reference corresponds to the case where the pre-correction feature value is outside the feature value range represented by the feature value correction reference.

  When the pre-correction feature amount is a value within the feature amount range represented by the feature amount correction reference, the light emission luminance value determined based on the pre-correction feature amount includes an enlarged display divided region corresponding to the target divided region. The value is close to the light emission luminance value determined based on the original image feature amount of the divided area (specific divided area).

  Specifically, when all of the enlarged display areas corresponding to the target divided area are included in one specific divided area, the emission luminance value determined based on the pre-correction feature value is the original image of the specific divided area. It matches the light emission luminance value determined based on the feature amount. Therefore, even if the light emission luminance value is determined based on the pre-correction feature value, the contrast (black reproducibility) of the enlarged image (display image) in the target divided region matches the contrast when displaying the original image.

Further, when the enlarged display area corresponding to the target divided area is included in the plurality of specific divided areas, the light emission luminance value determined based on the pre-correction feature quantity is the original image feature quantity of the plurality of specific divided areas. It becomes a value within the range of the light emission luminance value defined by the plurality of light emission luminance values determined based on it. In other words, the light emission luminance value determined based on the pre-correction feature value exceeds the maximum value of the plurality of light emission luminance values determined based on the original image feature values of the plurality of specific divided regions, or the minimum value. Never fall below. Therefore, even if the light emission luminance value is determined based on the pre-correction feature value, the contrast of the enlarged image (display image) is a value close to the contrast of the original image.
For example, as shown in FIGS. 5 and 6, the pre-correction feature quantity 82 of the divided area (X1, Y1) includes a part (area A) of the enlarged display divided area corresponding to the divided area (X1, Y1). It is larger than the original image feature quantity 66 of the region (X1, Y1). Therefore, in the display image, the contrast (black reproducibility) is lower than that of the original image at a portion where the region A is enlarged. On the other hand, the pre-correction feature quantity 82 of the divided area (X1, Y1) is a divided area (X2, Y1) including a part (area B, C, D) of the enlarged display divided area corresponding to the divided area (X1, Y1). ), (X1, Y2), (X2, Y2) are smaller than the original image feature quantities 92, 108, 134. Therefore, in the display image, the contrast (black reproducibility) is higher than that in the original image in the portion where the regions B, C, and D are enlarged. As described above, when a portion where the contrast is reduced and a portion where the contrast is increased are mixed in the divided area (when the contrast does not change in one direction in the entire divided area), it is difficult for the user to perceive the contrast change in the entire divided area. .
Therefore, in this embodiment, in S702, the pre-correction feature value is used as it is as the post-correction feature value, and the light emission luminance value of the target divided region is determined. The divided areas indicated by the circle marks in FIG. 8 are divided areas whose light emission luminance values are determined by the processing of S702, and the numerical values described in the divided areas are the feature amounts used when the light emission luminance values are determined. Value.

In S703, it is determined whether or not the pre-correction feature value of the target divided region is smaller than the minimum value of the feature value range represented by the feature value correction reference. If the pre-correction feature value of the target divided region is smaller than the minimum value of the feature value range represented by the feature value correction reference, the process proceeds to S704. When the feature amount before correction of the target divided region is not smaller than the minimum value of the feature amount range represented by the feature amount correction reference, that is, the feature amount range represented by the feature amount correction reference of the target divided region If it is larger than the maximum value, the process proceeds to S705.
As described above, when all of the enlarged display areas corresponding to the target divided area are included in one divided area, one original image feature value is used as a feature quantity correction reference. In such a case, the value represented by the feature amount correction reference is the maximum value and the minimum value of the feature amount range represented by the feature amount correction reference.

When the pre-correction feature quantity of the target divided area is smaller than the minimum value of the feature quantity range represented by the feature quantity correction reference, if the emission luminance value is determined based on the pre-correction feature quantity, the emission luminance is changed to the target divided area. The value is lower than the light emission luminance of any divided area including the corresponding enlarged display area. As a result, contrast (black reproducibility) increases in the entire target divided region. When the contrast changes in one direction in the entire divided area, the contrast change in the entire divided area is easily perceived by the user.
Therefore, in this embodiment, in S704, the pre-correction feature value of the target divided region is corrected so that the change in contrast is hardly perceived by the user, and the post-correction feature value is obtained. Then, the light emission luminance value of the target divided region is determined using the corrected feature amount.

Specifically, when the entire enlarged display area corresponding to the target divided area is included in one divided area, the pre-correction feature quantity of the target divided area is a value (original image) represented by the feature quantity correction reference. (Feature). In other words, the pre-correction feature amount of the target divided region is the original image feature amount of the divided region where the entire original image corresponding to the display image (enlarged image) displayed in the target divided region is displayed. Replaced (first process). Thereby, a corrected feature amount is obtained. By performing the first process, the change in contrast of the target divided region can be made zero. That is, the contrast at the time of enlarged display can be completely matched with the contrast at the same magnification display.
For example, as shown in FIG. 8, the pre-correction feature quantity 116 of the divided area (X2, Y2) is smaller than the feature quantity correction reference 134 of the divided area (X2, Y2). Therefore, the corrected feature amount of the divided area (X2, Y2) is 134. The divided area indicated by the triangular mark in FIG. 8 is a divided area in which the light emission luminance value is determined by the first processing.

In addition, when an enlarged display region corresponding to the target divided region is included in the plurality of divided regions, the feature amount before correction of the target divided region is corrected to a value within the feature amount range represented by the feature amount correction reference. The In other words, the original image of a plurality of divided regions in which the part of the original image corresponding to the display image (enlarged image) displayed in the target divided region is displayed as the pre-correction feature amount of the target divided region. It is corrected to a value within the feature amount range from the minimum value to the maximum value of the feature amount (second processing). Thereby, a corrected feature amount is obtained. By performing the second process, it is possible to reduce the change in contrast of the target divided region. In the present embodiment, in the second process, the pre-correction feature quantity of the target divided region is replaced with the minimum value of the feature quantity range.
For example, as shown in FIG. 8, the pre-correction feature quantity 129 of the divided area (X3, Y2) is smaller than the minimum value 134 of the feature quantity correction standards 134 to 160 of the divided area (X3, Y2). Therefore, the corrected feature amount of the divided area (X3, Y2) is 134. The divided areas indicated by the square marks in FIG. 8 are divided areas whose light emission luminance values have been determined by the second process.

When the pre-correction feature amount of the target divided region is larger than the maximum value of the feature amount range represented by the feature amount correction reference, if the emission luminance value is determined based on the pre-correction feature amount, The value is higher than the light emission luminance of any divided area including the corresponding enlarged display area. As a result, the contrast (black reproducibility) decreases in the entire target divided region. When the contrast changes in one direction in the entire divided area, the contrast change in the entire divided area is easily perceived by the user.
Therefore, in this embodiment, in S705, the feature amount before correction of the target divided region is corrected so that the change in contrast is not easily perceived by the user, and the corrected feature amount is obtained. Then, the light emission luminance value of the target divided region is determined using the corrected feature amount.

  Specifically, when all of the enlarged display areas corresponding to the target divided area are included in one divided area, a third process similar to the first process of S704 is performed. By performing the third process, the contrast change of the target divided region can be made zero.

  In addition, when the enlarged display area corresponding to the target divided area is included in the plurality of divided areas, the fourth process similar to the second process of S704 is performed. By performing the fourth process, it is possible to reduce the change in contrast of the target divided region. In the present embodiment, in the fourth process, the pre-correction feature value of the target divided region is replaced with the maximum value of the feature value range represented by the feature value correction reference.

  By performing the above processing for each divided region, as shown in FIG. 8, a corrected feature amount for each divided region (for each light emission block 107) is obtained. For each divided area, the light emission luminance is controlled based on the corrected feature amount for each divided area.

FIG. 9A shows an example of the difference between the light emission luminance at the enlarged display and the light emission luminance at the same magnification display when the conventional local dimming control is performed. Specifically, FIG. 9A shows an example of a value obtained by subtracting the original image feature amount of the divided region including the enlarged display divided region corresponding to the divided region from the pre-correction feature amount of the divided region.
FIG. 9B shows the light emission luminance at the enlarged display and the light emission at the same magnification display when the local dimming control according to the present embodiment (local dimming control for correcting the display feature amount described above) is performed. An example of a difference with luminance is shown. Specifically, FIG. 9A shows an example of a value obtained by subtracting the original image feature amount of the divided region including the enlarged display divided region corresponding to the divided region from the corrected feature amount of the divided region.
9A and 9B, the value of the original image feature value is the value shown in FIG. 4, the enlarged display divided region is the region shown in FIG. 6, and the pre-correction feature value is the value shown in FIG. In this example, the corrected feature value is the value shown in FIG.
By comparing FIG. 9A and FIG. 9B, by performing the processing of this embodiment, the difference in light emission luminance (difference in feature amount) is reduced compared to the conventional case, and in the case of enlarged display, etc. It can be seen that the contrast difference at the time of double display can be reduced.

As described above, according to the present embodiment, when displaying an enlarged image obtained by enlarging the original image, for each divided area, the first feature quantity that is the feature quantity of the enlarged image displayed in the divided area is To be acquired. Assuming that the original image is displayed, a second feature amount that is a feature amount of the original image displayed in the divided region is acquired for each divided region. For each divided region, the first feature amount is reduced so that a difference from the second feature amount of the divided region in which at least a part of the original image corresponding to the enlarged image displayed in the divided region is displayed is reduced. Correction processing is performed to correct. For each divided area, the light emission luminance of the backlight is controlled based on the first feature value after the correction process for each divided area.
Accordingly, it is possible to reduce a difference in contrast between when the original image is displayed on the display device that performs local dimming control based on the image to be displayed and when the enlarged image obtained by enlarging the original image is displayed.

Note that some of the first to fourth processes may be omitted. Specifically, some of the first to fourth processes may be omitted, and the pre-correction feature value may be used as it is as the post-correction feature value. Even in such a configuration, it is possible to reduce a change in contrast from the time of displaying the original image in the divided region where the first to fourth processes other than the part of the processes are performed. .
For example, in the present embodiment, a process (first process) for replacing a pre-correction feature quantity smaller than the original image feature quantity with the original image feature quantity, and a pre-correction feature quantity larger than the original image feature quantity is the original image feature quantity. It is assumed that both the process to replace (the third process) is performed, but this is not restrictive. Either the first process or the third process may not be performed.
In the present embodiment, a process (second process) for replacing a feature value before correction that is smaller than the minimum value of the feature value range with the minimum value, and a feature value before correction that is greater than the maximum value of the feature value range are set to the maximum value. However, the present invention is not limited to this. Either the second process or the fourth process may not be performed.
Further, when the light emission luminance value is reduced, the color expression of the high luminance region is impaired as a bad effect and color collapse occurs. Therefore, the third and fourth processes may be omitted in order to suppress the occurrence of such harmful effects.
Only one of the first to fourth processes may be performed.

In the present embodiment, in the second process, the pre-correction feature value is replaced with the minimum value of the feature value range represented by the feature value correction reference. However, the present invention is not limited to this. If the pre-correction feature value is corrected to a value within the feature value range represented by the feature value correction reference, it is possible to reduce the change in contrast from when the original image is displayed. However, the smaller the difference between the corrected feature value and the minimum value, the higher the contrast within a range in which the change in contrast from the original image display does not give the user a sense of incongruity.

  In the present embodiment, the pre-correction feature value is replaced with the maximum value of the feature value range represented by the feature value correction reference in the fourth process, but the present invention is not limited to this. If the pre-correction feature value is corrected to a value within the feature value range represented by the feature value correction reference, it is possible to reduce the change in contrast from when the original image is displayed. However, the smaller the difference between the corrected feature value and the maximum value, the higher the contrast within a range in which the change in contrast from when the original image is displayed does not give the user a sense of incongruity.

  When displaying the original image (same size image), the light emission luminance may be determined by the same process as when displaying the enlarged image, or not. For example, when displaying an original image, the processing of S301, S302, and S305 in FIG. 3 may be omitted. In S306, the light emission luminance may be determined based on the display image feature amount acquired in S304.

<Example 2>
Hereinafter, a display device and a control method thereof according to Embodiment 2 of the present invention will be described. In the first embodiment, an equal-magnification image is generated by the equal-magnification image generation unit 203, and an original image feature amount is acquired by the original image feature amount acquisition unit 204. In the present embodiment, a configuration that enables the same processing as in the first embodiment without using the equal-size image generation unit 203 and the original image feature amount acquisition unit 204 will be described.

FIG. 10 is a block diagram illustrating an example of the configuration of the display device (liquid crystal display device) according to the present embodiment. In FIG. 10, functional units mainly related to the image display processing are illustrated, and other functional units are omitted.
In the example of FIG. 10, the liquid crystal display device 1000 includes a decoding unit 201, an original image holding unit 202, a display image generating unit 1001, a feature amount acquiring unit 1002, a display image correcting unit 207, a feature amount holding unit 208, and a control unit. 209, a user operation receiving unit 210, a backlight controller 211, a backlight 101, a liquid crystal controller 212, and a liquid crystal panel 103.
Note that the functions of the functional units having the same reference numerals as those in the first embodiment (FIG. 2) are the same as those in the first embodiment, and thus the description thereof is omitted.

The display image generation unit 1001 generates an equal-size image and a display image and outputs them to the feature amount acquisition unit 1002. For example, when displaying the enlarged image, the display image generating unit 1001 generates an equal-sized image and also generates an enlarged image as a display image.
The feature amount acquisition unit 1002 receives the same size image and the display image from the display image generation unit 1001. The feature amount acquisition unit 1002 acquires the original image feature amount from the input equal-size image and records it in the feature amount holding unit 208. The feature amount acquisition unit 1002 acquires a display image feature amount (pre-correction feature amount) from the input display image, and records it in the feature amount holding unit 208.
In the present embodiment, the generation of the display image and the acquisition of the display image feature amount are performed after the generation of the equal-size image and the acquisition of the original image feature amount are performed. Not limited to this. The display image may be generated before the equal-size image. The generation of the same size image and the generation of the display image may be performed in parallel. The display image feature amount may be acquired before the normal-size image. The acquisition of the original image feature value and the acquisition of the display image feature value may be performed in parallel. Further, before displaying the display image, the same size image (original image) may be displayed or may not be displayed. The same-size image may be generated only for acquiring the original image feature amount, not for displaying.

  A processing flow of the liquid crystal display device according to the present embodiment will be described with reference to the flowchart of FIG.

  First, in step S <b> 301, the display image generation unit 1001 generates an equal-size image from an original image in response to an equal-size image generation instruction from the control unit 209. The same size image is generated by the same method as that of the same size image generating unit 203 of the first embodiment.

Next, in S302, the feature amount acquisition unit 1002 divides the equal-size image generated by the display image generation unit 1001 into a plurality of divided images corresponding to a plurality of divided regions. Then, the feature amount acquisition unit 1002 detects the maximum luminance value as the original image feature amount for each divided image. The original image feature quantity for each divided image (each divided area) is held by the feature quantity holding unit 208.
Note that the control unit 209 may manage the feature amount acquisition status. In that case, the feature quantity acquisition unit 1002 may output the acquired feature quantity to the control unit 209. Then, the control unit 209 determines whether the input feature amount (feature amount for each divided region) is the original image feature amount or the display image feature amount from the current feature amount acquisition state, and the input feature amount is determined. It may be recorded in the feature amount holding unit 208 in association with the determination result.

  In step S303, the display image generation unit 1001 generates a display image. The display image is generated by the same method as the display image generation unit 205 of the first embodiment.

  In step S <b> 304, the feature amount acquisition unit 1002 divides the display image generated by the display image generation unit 1001 into a plurality of divided images corresponding to a plurality of divided regions. Then, the feature amount acquisition unit 1002 detects the maximum luminance value as the display image feature amount for each divided image. The display image feature amount for each divided image (each divided region) is held by the feature amount holding unit 208.

  Since the processes in S305 and S306 are the same as those in the first embodiment, the description thereof is omitted.

  According to the present embodiment, the same effects as those of the first embodiment can be obtained with fewer functional units than those of the first embodiment.

DESCRIPTION OF SYMBOLS 101 Backlight 103 Liquid crystal panel 200,1000 Liquid crystal display device 203 Same size image generation part 204 Original image feature-value acquisition part 205,1001 Display image generation part 206 Display image feature-value acquisition part 209 Control part 1002 Feature-value acquisition part

Claims (12)

Display means for displaying an image on the screen;
A plurality of light-emitting means corresponding to a plurality of divided areas obtained by dividing the screen and capable of individually controlling the light emission luminance;
Control means for controlling the light emission luminance of each light emitting means;
With
When displaying an original image, a partial original image that is a part of the original image is displayed in each divided region,
When displaying an enlarged image obtained by enlarging the original image, a partial enlarged image that is a part of the enlarged image is displayed in each divided region,
The control means includes
To display the original image, a process of controlling the light emission luminance of the light emitting means corresponding to the divided region based on the partial original image displayed on the divided regions is performed for each divided area,
To display the enlarged image, is determined on the basis of the partial original image including a light emission luminance of the light emitting means corresponding to the divided region, the portion corresponding to the enlarged partial image displayed on the divided regions The partial source including the portion corresponding to the light emission luminance determined based on the partial enlarged image displayed in the divided region and the partial enlarged image displayed in the divided region. The process of controlling the light emission luminance of the light emitting means corresponding to the divided region is performed for each divided region so as to be reduced from the difference from the light emission luminance determined based on the image. A display device. The first feature quantity is a feature quantity of the partially enlarged image displayed in the divided region obtained for each divided region, the second feature quantity is a feature quantity of the partial original image displayed on the divided regions each It further has an acquisition means for acquiring the divided area ,
The control means includes
For each of the divided regions, the first feature amount and the second feature amount of the divided region in which the partial original image including the portion corresponding to the partial enlarged image displayed in the divided region is displayed. A correction process for correcting the first feature amount is performed so that the difference is reduced,
2. The display device according to claim 1, wherein, for each of the divided regions, the light emission luminance of the light emitting unit is controlled based on the first feature amount after the correction processing for each of the divided regions. The correction process, the dividing said first feature value of the region, the divided said displayed in the area partially enlarged the partial original said second divided area image is displayed including all of the portions corresponding to the image The display device according to claim 2, further comprising a process of replacing with a feature amount. Wherein said processing the first feature amount replaced with the second feature amounts, the second feature quantity is smaller than the first feature value to replace to the second feature quantity processing, the second feature quantity is larger than the first feature The display device according to claim 3, wherein the process is a process of replacing the quantity with the second feature quantity, or both. The correction process, the first feature quantity of the divided regions, a plurality of divided regions which the partial original image including a part of the portion corresponding to the enlarged partial image displayed on the divided area is displayed 5. The display device according to claim 2, further comprising a process of correcting to a value within a feature amount range from a minimum value to a maximum value of a plurality of second feature amounts. The treatment, processing for replacing the minimum value is smaller than the first feature quantity of the feature quantity range to the minimum value, the maximum of the feature amount range for correcting the first feature quantity to the value of the said characteristic quantity range The display device according to claim 5, wherein the first feature amount larger than the value is a process for replacing the first feature amount with the maximum value, or both. A display device control method comprising: display means for displaying an image on a screen; and a plurality of light emitting means corresponding to a plurality of divided areas obtained by dividing the screen and capable of individually controlling light emission luminance.
A control step of controlling the light emission brightness of each light emitting means;
When displaying an original image, a partial original image that is a part of the original image is displayed in each divided region,
When displaying an enlarged image obtained by enlarging the original image, a partial enlarged image that is a part of the enlarged image is displayed in each divided region,
In the control step,
To display the original image, processing for controlling the light emission luminance of the light emitting means corresponding to the divided region based on the partial original image displayed on the divided areas is performed for each divided area,
To display the enlarged image, is determined on the basis of the partial original image including a light emission luminance of the light emitting means corresponding to the divided region, the portion corresponding to the enlarged partial image displayed on the divided regions The partial source including the portion corresponding to the light emission luminance determined based on the partial enlarged image displayed in the divided region and the partial enlarged image displayed in the divided region. Processing for controlling the light emission luminance of the light emitting means corresponding to the divided region is performed for each divided region so as to be reduced from the difference from the light emission luminance determined based on the image. A control method for a display device. The first feature quantity is a feature quantity of the partially enlarged image displayed in the divided region obtained for each divided region, the second feature quantity is a feature quantity of the partial original image displayed on the divided regions each The method further comprises an acquisition step of acquiring the divided area .
In the control step,
For each of the divided regions, the first feature amount and the second feature amount of the divided region in which the partial original image including the portion corresponding to the partial enlarged image displayed in the divided region is displayed. Correction processing for correcting the first feature amount is performed so that the difference is reduced,
The display device control method according to claim 7, wherein the light emission luminance of the light emitting unit is controlled for each of the divided regions based on the first feature amount after the correction processing for each of the divided regions. . The correction process, the dividing said first feature value of the region, the divided said displayed in the area partially enlarged the partial original said second divided area image is displayed including all of the portions corresponding to the image The method for controlling a display device according to claim 8, further comprising a process of replacing with a feature amount. Wherein said processing the first feature amount replaced with the second feature amounts, the second feature quantity is smaller than the first feature value to replace to the second feature quantity processing, the second feature quantity is larger than the first feature The display device control method according to claim 9, wherein the process is a process of replacing the quantity with the second feature quantity, or both. The correction process, the first feature quantity of the divided regions, a plurality of divided regions which the partial original image including a part of the portion corresponding to the enlarged partial image displayed on the divided area is displayed The method for controlling a display device according to any one of claims 8 to 10, including a process of correcting to a value within a feature amount range from a minimum value to a maximum value of a plurality of second feature amounts. The treatment, processing for replacing the minimum value is smaller than the first feature quantity of the feature quantity range to the minimum value, the maximum of the feature amount range for correcting the first feature quantity to the value of the said characteristic quantity range 12. The method for controlling a display device according to claim 11, wherein the first feature amount larger than the value is replaced with the maximum value, or both.

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