JP2018180443A - Display device and control method for display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of image quality by reducing leakage light caused by the response delay of a liquid crystal.SOLUTION: A display device includes a display panel which has a plurality of pixels, a display control part which controls the display panel according to inputted image data, illumination means which has a plurality of light-emitting means arranged on the rear side of the display panel, and light emission control means which controls light emission intensity for each control area included in the illumination means. The light emission control means executes processing for controlling a difference in the light emission intensity with respect to a surrounding control area according to the time change amount of the image data of a position corresponding to the control area.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control method of a display device.

There is a technique called local dimming in which the luminance of each divided area (hereinafter, BL control area) of a backlight capable of divided lighting control can be changed according to an input video signal. In the local dimming control, the liquid crystal display device controls the backlight in accordance with the input video signal, and changes the brightness of the backlight for each BL control area.
On the other hand, the liquid crystal display device controls the liquid crystal panel by changing the voltage applied to the liquid crystal panel according to the input video signal, and controls the light transmittance of the backlight. As a result, gradation expression according to the video signal is performed on the liquid crystal panel.

  Here, since the response speed of the liquid crystal panel is slower than that of the backlight, the time taken to control the liquid crystal panel is longer than the time taken to control the backlight. For this reason, when the backlight is turned on in the BL control area, the liquid crystal panel in the same BL control area does not have a predetermined transmittance, and light leaks from the liquid crystal panel, causing flicker, that is, flickering of the screen. May cause Therefore, there is a need for a technique for preventing image quality deterioration due to flicker. Leakage light refers to a phenomenon in which the light of the backlight leaks from the liquid crystal panel because the transmittance of the liquid crystal panel is lowered.

  According to Patent Document 1, the same space LPF is uniformly applied to each BL control area, and the brightness of the BL control area is smoothed to avoid that one BL control area blinks locally. , Making the flicker less likely to occur.

JP, 2010-039110, A

Here, it is assumed that a dark image is displayed with one bright area left after a bright image is displayed on the liquid crystal panel as a whole. In this case, the BL control area corresponding to the bright area lights up brightly, and the BL control area corresponding to the surrounding dark area lights up a little brightly by smoothing. However, since the transmittance of the region where the dark image of the liquid crystal panel is displayed is not lowered, leaked light is generated from the surrounding dark region, which causes a problem of causing flicker.
An object of the present invention is to provide a technology capable of reducing the leakage light due to the response delay of the display panel and improving the image quality deterioration in view of the above-mentioned problems.

  According to a first aspect of the present invention, there is provided a display panel having a plurality of pixels, a display control section for controlling the display panel according to input image data, and a plurality of light emitting means disposed on the back side of the display panel. And light emission control means for controlling the light emission intensity for each control area included in the lighting means, wherein the light emission control means controls the time change amount of the image data of the position corresponding to the control area. According to the present invention, there is provided a display device characterized in that processing for controlling the difference in light emission intensity with the surrounding control area is performed.

  According to a second aspect of the present invention, there is provided a display panel having a plurality of pixels, a display control unit for controlling the display panel according to input image data, and a plurality of light emitting means disposed on the back side of the display panel. And controlling the light emission intensity for each of the control areas included in the lighting means, and controlling the light emission intensity in response to the control area. According to another aspect of the present invention, there is provided a control method of a display device, which executes a process of controlling a difference in light emission intensity with a surrounding control area in accordance with a time change amount of image data of a position.

  According to the present invention, it is possible to reduce the leakage light due to the response delay of the display panel and to further improve the image quality deterioration.

FIG. 1 is a block diagram for explaining a configuration example of a display device according to a first embodiment. FIG. 7 is a diagram showing an example of a flowchart of processing of the first embodiment. FIG. 6 is a diagram for explaining local dimming of the first embodiment. It is a figure which shows the 1st example of the data structure of leakage light reduction table data. FIG. 6 is a diagram showing an example of a space LPF coefficient K. It is a figure which shows the local dimming of a prior art example. FIG. 7 is a diagram showing local dimming of the first embodiment. It is a figure which shows the example of the local dimming of a prior art example and Example 1. FIG. FIG. 13 is a diagram illustrating an example of a flowchart of processing of Example 2; FIG. 7 is a diagram showing local dimming of the first embodiment. FIG. 18 is a block diagram for explaining a configuration example of a display device according to a third embodiment. FIG. 18 is a diagram illustrating an example of a flowchart of processing of a third embodiment. It is a figure which shows the 2nd example of the data structure of leakage light reduction table data.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numeral is attached in principle to the same configuration, and the overlapping description is omitted. In addition, numerical values and the like exemplified to embody the description are not limited to these unless specifically mentioned.
Further, the present invention is not limited to the following embodiments, and can be appropriately modified without departing from the scope of the invention. For example, each configuration of the following embodiments may be appropriately modified or changed depending on the configuration of the apparatus to which the present invention is applied and various conditions.

Example 1
(Configuration of Display Device 100)
Hereinafter, the configuration of the first embodiment will be described with reference to the drawings.
FIG. 1 is a block diagram for explaining a configuration example of the display device 100 according to the first embodiment. The display device 100 includes a liquid crystal panel 101, a backlight 102, a BL (Back Light) control value calculation unit 103, a frame memory 104, a spatial LPF selection unit 105, and leakage light reduction table data 106. The display device 100 further includes LPF coefficient table data 107, an LPF coefficient reading unit 108, and a spatial LPF application unit 109. The BL control value calculation unit 103, the frame memory 104, the space LPF selection unit 105, the leakage light reduction table data 106, the LPF coefficient table data 107, the LPF coefficient reading unit 108, and the space LPF application unit 109 function as the light emission control unit 50. Do.

The light emission control means 50 controls the light emission intensity for each of the BL control areas included in the backlight 102, and emits light with the surrounding control area according to the time change amount of the image data at the position corresponding to the BL control area. A smoothing process for controlling the difference in intensity is executed for each control area. The light emission control means 50 reduces the degree of smoothing between the control areas as the time change amount of the image data at the position corresponding to the BL control area is larger.
Here, the difference between the image data of one frame before and the current frame may be used as the time change amount of the image data. Further, the difference between the average values of pixel values in the area of the liquid crystal panel 101 corresponding to the control area of one frame before and the current frame may be used as the time variation of the image data.
The smoothing process is a process of applying a spatial LPF to the light emission control amount of each control area.
Note that the processing by the light emission control unit 50 described later may be executed by a plurality of circuits (for example, ASICs), or one or more processors in the display device 100 may read and execute the program from the memory.

A liquid crystal panel 101 (LCD (Liquid Crystal Display)) is a display panel that has a plurality of pixels and transmits an light emitted from the backlight 102 with a predetermined transmittance to display an image on the screen.
The display control unit 101a has a function of controlling the liquid crystal panel 101 in accordance with the input video signal. The video signal is, for example, image data such as a pixel value (RGB value) of each pixel.
The backlight 102 has a plurality of BL control areas on the back side of the liquid crystal panel 101, and lighting is performed for each BL control area according to the brightness of the image displayed in the area of the liquid crystal panel corresponding to each BL control area. It is an illumination unit that controls the brightness (emission intensity). Such control is called "local dimming control" or the like. Further, the BL control area includes a plurality of LEDs (light emitting means). The specific control method will be described later.

The BL control value calculation unit 103 has a function of calculating a BL brightness control value (light emission control amount) bd for each BL control area of the backlight 102. The method of calculating the BL brightness control value bd will be described later.
The frame memory 104 has a function of storing the input video signal.
The spatial LPF selection unit 105 responds to the time change amount of the video signal at the position corresponding to the BL control area for each BL control area based on the video signal of the previous frame stored in the frame memory 104 and the current frame. It has a function of selecting the spatial LPF coefficient K. The space LPF coefficient K is used as a space LPF (low pass filter).
The leaked light reduction table data 106 is a table that associates the time variation of the video signal with the spatial LPF coefficient number L that uniquely identifies the spatial LPF coefficient K.
The LPF coefficient table data 107 (storage unit) is a table for storing a plurality of spatial LPF coefficients K. The light emission control unit 50 acquires, as smoothing processing, a space LPF corresponding to the time change amount of the image data from the LPF coefficient table data 107, and applies the space LPF to the light emission control amount of each control area.
The LPF coefficient reading unit 108 has a function of reading out the spatial LPF coefficient K corresponding to the spatial LPF coefficient number L from the LPF coefficient table data 107 for each BL control area.
The space LPF application unit 109 has a function of executing, for each BL control area, a process of controlling the difference in light emission intensity with the surrounding BL control area using the space LPF coefficient K read for each BL control area. .

(Process of Example 1)
FIG. 2 is a diagram illustrating an example of a flowchart of processing of the first embodiment. The process of the first embodiment will be described with reference to FIG.
In step S <b> 21, the BL control value calculation unit 103 acquires the RGB signal input to the display device 100 as a video signal. Here, the RGB signals are image data of red (R value), green (G value) and blue (B value) for each pixel of the liquid crystal panel 101. In the RGB signal, each color is shown, for example, in the range of 0-255. Hereinafter, the value of each color for each pixel indicated by the RGB signal is referred to as a pixel value.
In step S22, the BL control value calculation unit 103 converts pixel values (RGB) into color data luminance values Y (luminance information). Specifically, the BL control value calculation unit 103 converts the pixel value into the color data luminance value Y using the following equation (1).
Y = αR + βG + γB (1)
α, β, and γ are luminance conversion coefficients at the time of converting the RGB signal values into luminance.

  In step S23, the BL control value calculation unit 103 calculates an average value YAG of color data luminance values Y of one or more pixels for each pixel area. Here, as described above, the backlight 102 controls the brightness in BL control area units, but the pixel area is the area of the liquid crystal panel 101 at a position corresponding to the BL control area. Hereinafter, the relationship between the BL control area and the pixel area will be described.

3A and 3B are diagrams for explaining the local dimming of the first embodiment. FIG. 3A shows an example in which the backlight 102 is divided into four in the vertical direction and five in the horizontal direction. Each square in FIG. 3A is a BL control area, a plurality of LEDs are arranged on each square, and the brightness is controlled for each BL control area.
In the following, the position of each BL control area is represented by the number m of rows counted from the upper left of the backlight 102 and the number n of columns. For example, BL control area A is represented by m = 0, n = 0, BL control area B is represented by m = 3, n = 4, BL control area C is represented by m = 1, n = 3, BL control area D is represented by m = 3 and n = 2.

FIG. 3B shows an example in which the liquid crystal panel 101 is divided into four in the vertical direction and five in the horizontal direction as in the backlight 102. The position of each pixel area is represented by the number M of rows counted from the upper left of the liquid crystal panel 101 and the number N of columns.
In the first embodiment, the backlight 102 of FIG. 3A is disposed directly below the liquid crystal panel 101 of FIG. 3B, and the position (m, n) of each BL control area of the backlight 102 and the liquid crystal panel 101 The position (M, N) of the pixel area is associated.
For example, the pixel area a corresponding to the BL control area A (position is (m = 0, n = 0)) is at the position of M = 0 and N = 0, and the BL control area B (position is (m = 3, The pixel area b corresponding to n = 4) is at the position of M = 3, N = 4. Further, the pixel area c corresponding to the BL control area C (position is (m = 1, n = 3)) is at the position of M = 1, N = 3, and the BL control area D (position is (m = 3, The pixel area d corresponding to n = 2) is at the position of M = 3, N = 2.

  Steps S22 and S23 described above will be described using the example of FIG. 3B. In step S22, the BL control value calculation unit 103 calculates color data luminance values Y of all the pixels of the liquid crystal panel 101 according to the equation (1). Subsequently, in step S23, the BL control value calculation unit 103 calculates an average value YAG of color data luminance values Y of the pixels included in the pixel area for each pixel area in FIG. 3B. For example, the BL control value calculation unit 103 calculates an average value YAG of color data luminance values Y of a plurality of pixels included in the pixel area a. The BL control value calculation unit 103 similarly calculates the average value YAG of the color data luminance value Y for the pixel areas b, c, d and the other pixel areas.

  Return to FIG. In step S24, the BL control value calculation unit 103 calculates a BL brightness control value bd for each BL control area. The BL brightness control value bd is calculated for one BL control area, and is a value indicating the brightness in the BL control area. In the first embodiment, the BL brightness control value bd is an integer in the range of 0 to 255. The larger the BL brightness control value bd, the brighter the BL control area.

The BL control value calculation unit 103 calculates a BL brightness control value bdmn of the BL control area at the position of m rows and n columns using the following equation (2). In addition, an average value of color data luminance values Y of pixel areas in m rows and n columns is set as YAGmn, and a maximum luminance value in the same pixel area is set as Ymax.
bdmn = YAGmn ÷ Ymax (2)

  For example, according to FIG. 3A and FIG. 3B, the BL control value calculation unit 103 sets the BL brightness control value “bd00” of the BL control area A at the 0 row and 0 column position to the pixel area a at 0 row and 0 column position. Is calculated by substituting YAG00 and Ymax in equation (2). Further, the BL control value calculation unit 103 substitutes YAG 13 and Ymax of the pixel area c at the positions of three rows for the “bd13” of the BL control area C at the positions of one row and three columns into the equation (2) Calculate. The BL brightness control values of the other BL control areas are similarly calculated.

  Return to FIG. In step S25, the spatial LPF selection unit 105 acquires the pixel value (video signal) of one frame before from the frame memory 104. The video signal input to the display device 100 is sequentially stored in the frame memory 104, and a video signal (RGB signal) of one frame before is stored. The space LPF selection unit 105 has already acquired the video signal of the current frame.

In step S26, the spatial LPF selection unit 105 acquires spatial LPF coefficient numbers according to changes in color data luminance values of the current frame and the immediately preceding frame. Specifically, the spatial LPF selection unit 105 obtains an average value YAG (p) based on the color data luminance value Y of each pixel in the pixel area of the current frame. Furthermore, the spatial LPF selection unit 105 acquires video data in the pixel area of the immediately preceding frame from the frame memory 104, and calculates an average value YAG (p-1) based on the video data.
Subsequently, the spatial LPF selection unit 105 refers to the leakage light reduction table data 106 and selects the spatial LPF coefficient number L according to the change of the pixel value. Here, there are spatial LPF coefficient numbers L from 0 to 10, and one is assigned to 11 spatial LPF coefficients K described later. The spatial LPF selection unit 105 refers to the leakage light reduction table data 106 and determines one spatial LPF coefficient number by the average value YAG of the current frame (P) and the average value YAG of the previous frame (p-1). Identify L

FIG. 4 is a view showing a first example of the data structure of the leakage light reduction table data 106. As shown in FIG. Each row of the leaked light reduction table data 106 corresponds to the average value YAG (p−1) of the previous frame, and each column corresponds to the average value YAG (p) of the current frame. In the table of FIG. 4, the range of the average value YAG (p-1) of one frame before to 3 to 253 and the range of the average value YAG (p) of the current frame to 3 to 253 are omitted. There is.
For example, according to the table in FIG. 4, when the average value YAG (p-1) of one frame before is "0" and the average value YAG (p) of the current frame is "0", the spatial LPF coefficient number L is " It will be 10 ". When the average value YAG (p-1) of the previous frame is "2" and the average value YAG (p) of the current frame is "0", the spatial LPF coefficient number L is "9". When the average value YAG (p-1) of the previous frame is "254" and the average value YAG (p) of the current frame is "255", the spatial LPF coefficient number L is "10".

  In the above, the example of calculating YAG (p-1) and YAG (p) from the color data luminance value in the pixel area has been described, but the present invention is not limited to this. YAG (p-1) and YAG (p) may be calculated from gradation data (gradation information, for example, R value, G value, B value) in the pixel area. For example, the spatial LPF selection unit 105 calculates (R value + G value + B value) / 3 of 1 frame before and current frame for each pixel, and average value of (R value + G value + B value) / 3 is YAG (p -1) and YAG (p).

Return to FIG. In step S27, the LPF coefficient reading unit 108 reads out and acquires the spatial LPF coefficient K corresponding to the spatial LPF coefficient number L from the LPF coefficient table data 107. Here, the LPF coefficient table data 107 is a table in which spatial LPF coefficients K corresponding to the respective spatial LPF coefficient numbers L are stored. In the case of the first embodiment, eleven space LPF coefficients K corresponding to space LPF coefficient numbers L from 0 to 10 are stored in the LPF coefficient table data 107.
Here, the spatial LPF coefficient K is a matrix of i rows and j columns having a plurality of coefficients for calculating the backlight control value T from the BL brightness control value bd of the BL control area. The number of components of the matrix of the spatial LPF coefficients K may be changed according to the processing capability of the display device 100.

FIG. 5 is a view showing an example of the spatial LPF coefficient K stored in the LPF coefficient table data 107. As shown in FIG. Space LPF coefficients K501 to K511 corresponding to space LPF coefficient numbers L of 0 to 10 are shown in FIG. In FIG. 5, the space LPF coefficients K503 to K510 are omitted.
The numerical values shown in the squares of the space LPF coefficients K501 to K511 indicate the components of the space LPF coefficient K matrix. In the example of FIG. 5, it is assumed that the spatial LPF coefficient K is a matrix of 3 rows (i = 3) and 3 columns (j = 3).

For example, when the LPF coefficient reading unit 108 acquires the spatial LPF coefficient K “501” corresponding to the spatial LPF coefficient number L “0”, the coefficient of the central BL control area becomes “1.00”, and the surrounding The coefficient of the BL control area is "0.00". Therefore, when the spatial LPF coefficient K “501” is applied, the self BL control area is lighted with brightness according to only the BL brightness control value of the central self BL control area (self control area).
Also, for example, when the LPF coefficient reading unit 108 acquires the spatial LPF coefficient K “511” corresponding to the spatial LPF coefficient number L “10”, the coefficient of the self-BL control area at the center becomes “0.20”, The coefficient of the surrounding BL control area is "0.10". Therefore, when the spatial LPF coefficient K “511” is applied, the central self-BL control area lights up with brightness relatively influenced by the BL luminance control value of the surrounding BL control area. As described above, as the spatial LPF coefficient number L increases, it becomes more susceptible to the BL brightness control value of the BL control area around the BL control area corresponding to the pixel area.

Therefore, a relatively large spatial LPF coefficient number L is selected for the BL control area corresponding to the pixel area where the change in luminance value of the video signal is gentle, and the influence of the luminance control value of the surrounding BL control area is large The spatial LPF coefficient is to be selected. As a result, the difference in brightness between the own BL control area and the surrounding BL control area is reduced, and the brightness of the BL control area is smoothed.
Also, for the BL control area corresponding to the pixel area where the change in luminance value of the video signal is large, a relatively small spatial LPF coefficient number L is selected, and the space LPF that is largely affected by the luminance control value of the own BL control area The coefficients will be selected. As a result, the effect of smoothing the brightness of the BL control area becomes small or zero. As a result, it is possible to reduce the leaked light due to the response delay of the liquid crystal panel, which has conventionally been a problem.
In the following, it is assumed that the spatial LPF coefficient of the BL control area located in m rows and n columns is denoted as “Kmn”.

  Return to FIG. In step S28, the space LPF application unit 109 calculates the backlight control value T of the BL control area using the space LPF coefficient K and the BL brightness control value bd, and sets the backlight control value T in the backlight 102. In the following, it is assumed that the backlight control value of the BL control area located in m rows and n columns is denoted as Tmn. Here, the backlight control value Tmn is a matrix indicating the light emission control amount of each BL control area.

The space LPF application unit 109 calculates the backlight control value Tmn of the BL control area at the position of m rows and n columns, substituting the space LPF coefficient K mn and the BL brightness control value b dmn into the following equation (3) Do. Kmn is assumed to be a matrix of 3 rows and 3 columns.

Since the video signal is sent for each lighting frequency for driving the backlight 102 and the spatial LPF coefficient Kmn is obtained, the spatial LPF application unit 109 uses the equation (3) to calculate the backlight control value Tmn each time. calculate. Then, the backlight 102 controls each BL control area based on the backlight control value Tmn.
Although the example in which the spatial LPF is applied to all the BL control areas of the backlight 102 has been described in the first embodiment, the present invention is not limited to this. The spatial LPF may be applied to only a part of the BL control area of the backlight 102.

(Effect of Example 1 Compared to Conventional Example)
FIG. 6 is a diagram showing local dimming in the conventional example. The “frame number” indicates the frame number of the video signal, and it is assumed that the transition from frame 1 to frame 2 is made. "Video signal" indicates an image output in frame 1 and frame 2. An image in which all white is output in frame 1 and an image in which only the center is white and the periphery is black are output in frame 2 I assume.
“LCD transmittance” indicates the change of the transmittance of the liquid crystal panel 101, and further shows the frame 1 divided into three subframes t_1-1, t_1-2, and t_1-3. The transmittance of the liquid crystal panel 101 does not change at t_1-1, t_1-2, and t_1-3. On the other hand, frame 2 is further divided into three subframes t_2-1, t_2-2, and t_2-3. The transmittance around the center of the liquid crystal panel 101 gradually decreases at t_2−1, t_2−2, and t_2−3. The liquid crystal panel 101 has a desired transmittance for the first time at time t_2-3, and the transmittance of the liquid crystal panel 101 is not sufficiently lowered at t_2-1 and t_2-2. As described above, the liquid crystal panel 101 has a relatively slow response speed, and it takes a certain time to reach a desired transmittance.

  “BL lighting state” indicates the lighting state of each BL control area, and in the example of FIG. 6, it is assumed that the BL control area is divided into three rows and three columns. In frame 1, the lighting state of the BL control area does not change at t_1-1, t_1-2, t_1-3. On the other hand, in frame 2, the lighting state changes in order from the BL control area of the upper row at t_2-1, t_2-2, and t_2-3. Here, at t_2-1, t_2-2, and t_2-3, the surrounding BL control area corresponding to the position at which the black image is displayed is not turned off, and is slightly brightly lit. This is to compensate for the brightness by slightly lighting the surrounding BL control area since the brightness is not sufficient even if only the center BL control area is lighted to reproduce the white color at the center of the image.

  “Display screen” shows a screen actually displayed on the liquid crystal panel 101. In the frame 1, the display screen does not particularly change in t_1-1, t_1-2, and t_1-3. On the other hand, in frame 2, the portion corresponding to the upper row in which the BL lighting state is changed at t_2-1 is slightly bright, and the upper row in which the BL lighting state is changed in t_2-2 is middle The part corresponding to the line (except for the center) is slightly bright. This means that the BL control area in the surrounding area is lighted a little brightly in the "BL lighted state", and the liquid crystal panel at the time of t_2-1 and t_2-2 in the "LCD transmittance". Since the transmittance of 101 is not sufficiently lowered, leaked light is generated.

FIG. 7 is a diagram showing local dimming of the first embodiment. The differences from FIG. 6 will be mainly described. The “frame number”, “video signal” and “LCD transmittance” are the same as in FIG. On the other hand, it is different from the conventional example in that the BL control area in the upper row at t — 2−1, the middle row at t — 2-2 excluding the center, and the surrounding BL control area at t — 2-3 are not illuminated. For this reason, regarding the display screen, the line above the display screen at time t_2−1, the line above the display screen at time t_2-2 and the line inside the display screen (excluding the center) are displayed in black. It can be seen that no leaked light has occurred.
As described above, in the conventional example, the leaked light is generated until the liquid crystal panel 101 reaches a desired transmittance, which causes the flicker, whereas in the first embodiment, the leaked light can be suppressed. It can be suppressed.

Next, the comparison of the effects of the conventional example and the first embodiment will be described with reference to a specific example.
FIG. 8 is a diagram showing a specific example of local dimming in the conventional example and the first embodiment. In FIG. 8, the BL brightness control value bd, the spatial LPF coefficient K, and the backlight control value T of the conventional example are sequentially shown on the upper side. Further, the BL brightness control value bd, the spatial LPF coefficient K, and the backlight control value T of the first embodiment are sequentially shown on the lower side. That is, the brightness of the image largely changes in the pixel areas corresponding to the eight surrounding BL control areas.
It is assumed that the BL control area of the backlight 102 is divided into 9 in total of 3 rows and 3 columns. In the conventional example, the BL brightness control value bd in the first embodiment changes similarly, and in the previous frame, all the BL brightness control values bd are set to 255, and in the current frame, the BL brightness control value bd is set to 255 only at the center and the others are 0 Shall be
It is assumed that the space LPF coefficient K of the conventional example is a matrix of three rows and three columns, and the middle term is "0.20" and the other terms are "0.10". On the other hand, a matrix of three rows and three columns of spatial LPF coefficient number L “0” is selected as the spatial LPF coefficient K for the BL control area around Example 1, and the center term is “1.00” and other terms Is assumed to be "0.00". In addition, as the spatial LPF coefficient K for the central BL control area in the first embodiment, a matrix of three rows and three columns of spatial LPF coefficient number L of “10” is selected, and the central term is “0.20” and other terms are It shall be "0.10".
The backlight control value T of the conventional example and the first embodiment is calculated by substituting the equation (3) under the above conditions.
When the backlight control value T of the BL control area on the end side of the backlight 102 is calculated, there may be a place where there is no BL control area in the periphery. In this case, the backlight control value T may be calculated using the BL brightness control value bd of the BL control area adjacent to a place where there is no BL control area in the periphery.

In the conventional example, the backlight control value T at the center is "51.00", and the backlight control value T around it is "25.50". Thus, it can be seen that in the case of the conventional example, the BL control area around the central bright BL control area is also controlled to be slightly brighter.
On the other hand, in the first embodiment, the backlight control value T at the center is "51.00", and the backlight control value T around it is "0.00". As described above, in the first embodiment, the surrounding BL control area is controlled to be dark as compared with the conventional example. As described above, since the BL control area corresponding to the pixel area in which the image has changed from white to black becomes dark, leaked light is suppressed even if the liquid crystal response is delayed. Thereby, the effect of suppressing the flicker described above can be obtained.

Example 2
In the first embodiment, control is performed to switch the spatial LPF (spatial LPF coefficient K) for each frame according to the change of the color data luminance value Y of the previous frame and the current frame. On the other hand, in the second embodiment, the backlight 102 is controlled by switching to different space LPFs in the first half and the second half of the frame. That is, as the smoothing process, the light emission control means 50 performs a process of increasing the degree of smoothing after controlling the degree of smoothing according to the amount of temporal change of the image data at the position corresponding to the BL control area.
(Process of Example 2)
Also in the second embodiment, the configuration of the display device 100 is the same as that shown in FIG.
FIG. 9 is a diagram illustrating an example of a flowchart of processing of the second embodiment. The process of the second embodiment will be described with reference to FIG. The processes of steps S81 to S88 are the same as the processes of steps S21 to S28 of FIG. That is, the BL control value calculation unit 103 acquires the RGB signal (video signal) in step S81, and converts the pixel value (RGB) into the color data luminance value Y in step S102. Subsequently, the BL control value calculation unit 103 calculates the average value YAG of the color data luminance values Y for each pixel area in step S83, and calculates the BL luminance control value bd for each BL control area in step S84. Subsequently, the spatial LPF selection unit 105 acquires the pixel value of one frame before at step S85, and the spatial LPF coefficient number L1 according to the change of the color data luminance value of the current frame and the immediately preceding frame at step S86. get. Subsequently, the LPF coefficient reading unit 108 acquires the spatial LPF coefficient K1 corresponding to the spatial LPF coefficient number L1 in step S87, and the spatial LPF application unit 109 uses the spatial LPF coefficient K1 in step S88 to control each BL control area The backlight control value T1 of is set.

Subsequently, in step S89, the space LPF selection unit 105 selects, for each BL control area, the space LPF coefficient number L2 when the immediately preceding frame has the same color data luminance value as the current frame.
Specifically, the spatial LPF selection unit 105 determines that the average value YAG (p-1) of the color data luminance values of the immediately preceding frame is the same value as the average value YAG (p) of the color data luminance values of the current frame. As being In this case, the spatial LPF selection unit 105 refers to the leakage light reduction table data 106 to acquire the spatial LPF coefficient number L2.

  For example, in FIG. 4, when the YAG (p) is “2”, the spatial LPF selection unit 105 also regards YAG (p−1) as “2”, refers to the leak light reduction table data 106, and The LPF coefficient number L2 "10" is acquired. When the YAG (p) is "255", the space LPF selection unit 105 also regards YAG (p-1) as "255" and refers to the leakage light reduction table data 106, and the space LPF coefficient number L2 Get "10". Thus, the largest spatial LPF coefficient number L2 is selected in step S89.

  Return to FIG. In step S90, the LPF coefficient reading unit 108 reads out and acquires the spatial LPF coefficient K2 corresponding to the spatial LPF coefficient number L2 from the LPF coefficient table data 107. Subsequently, in step S91, the space LPF application unit 109 calculates the backlight control value T2 of the BL control area by multiplying the space LPF coefficient K2 by the BL brightness control value bd using the equation (3). .

  As described above, since the spatial LPF coefficient K2 related to the relatively large spatial LPF coefficient number L2 is selected in step S89, for example, the dark BL control area around the bright BL control area lights up a little brightly . This makes it possible to brighten the target BL control area by light coming from the surroundings. Furthermore, since the transmittance of the liquid crystal is sufficiently low at this time, light in the surrounding BL control area does not pass through the liquid crystal, and leakage light does not occur.

(Effect of Example 2)
FIG. 10 is a diagram illustrating local dimming of the first embodiment. The “frame number” and the “video signal” are the same as in FIG.
“LCD transmittance” indicates a change in transmittance of the liquid crystal panel 101, and the frame 1 is further divided into six sub-frames t_1-1, t_1-2, t_1-3, t_1-4, t_1-5, t_1, Divided into six. The transmittance of the liquid crystal panel 101 does not change at t_1-1, t_1-2, t_1-3, t_1-4, t_1-5, and t_1-6. On the other hand, frame 2 is further divided into six subframes t_2-1, t_2-2, t_2-3, t_2-4, t_2-5, and t_2-6. The transmittance around the center of the liquid crystal panel 101 gradually decreases at t_2−1, t_2−2, t_2−3, and t_2−4. The liquid crystal panel 101 has a predetermined transmittance for the first time at time t_2-4, and the transmittance of the liquid crystal panel 101 is not sufficiently lowered at t_2-1, t_2-2, and t_2-3.

“BL lighting state” indicates the lighting state of each BL control area, and it is assumed that the BL control area is divided into three rows and three columns. In frame 1, the lighting state of the BL control area does not change at t_1-1, t_1-2, t_1-3, t_1-4, t_1-5, t_1-6. On the other hand, in frame 2, the lighting state changes in order from the BL control area of the upper row at t_2-1, t_2-2, and t_2-3. At t_2-3, the BL control area in the surrounding part is in the off state.
Subsequently, at t_ 2-4, t_ 2-5, t_ 2-6 again, the lighting state changes in order from the BL control area of the upper row one by one. At t_2-6, the BL control area in the surrounding area is lightened a little brightly. In the second embodiment, the driving frequency of the backlight 102 is twice that of the liquid crystal panel 101, and the lighting state of the BL control area can be changed twice in one frame.

“Display screen” shows a screen actually displayed on the liquid crystal panel 101. In the frame 1, the display screen does not particularly change at t_1-1, t_1-2, t_1-3, t_1-4, t_1-5, t_1-6. On the other hand, in frame 2, the line above the display screen at time t_2-1 and the line above the display screen at time t_2-2 and the line in the middle except for the central part are displayed in black, and leakage light is displayed. It turns out that it has not occurred. At time t_2-3, the lower line of the display screen is further displayed black. At this time, the central portion of the display screen is slightly dark due to lack of luminance. Then, the surrounding BL control area is slightly brightened at t_2-4, t_2-5, and t_2-6, so that the central portion of the display screen gradually changes to a bright state.
As described above, in the second embodiment, not only the effect of preventing leak light but also the effect of enhancing the brightness in the BL control area is exhibited.

Example 3
In the first embodiment and the second embodiment, the average value YAG of the color data luminance value Y is calculated from the video signal corresponding to the previous frame and the current frame, and the spatial LPF coefficient K corresponding to the change of the color data luminance value YAG is acquired Be done. On the other hand, in the third embodiment, the BL luminance control value bd corresponding to the previous frame and the current frame is acquired from the BL control value calculator 103, and the spatial LPF coefficient K corresponding to the change of the BL luminance control value bd is It is acquired. That is, the light emission control means 55 calculates the light emission control amount calculated on the basis of the image data of the position corresponding to the BL control area for the one frame previous and the current frame respectively, The difference between the amounts is taken as the time change amount of the image data.
(Configuration of Example 3)
The configuration of the third embodiment will be described below with reference to the drawings. The same components as in the first embodiment are given the same reference numerals, and the description thereof will be omitted as appropriate.
FIG. 11 is a block diagram for explaining a configuration example of the display device 300 according to the third embodiment. The same components as in the first embodiment are given the same reference numerals, and the description thereof will be omitted as appropriate.
The frame memory 304 has a function of storing the BL brightness control value bd output from the BL control value calculation unit 103.
The spatial LPF selection unit 305 temporally changes the BL brightness control value bd of the BL control area based on the BL brightness control value bd of the previous frame stored in the frame memory 104 and the BL brightness control value bd of the current frame. It has a function of selecting a spatial LPF coefficient according to the amount.
The leakage light reduction table data 306 is a table that associates the time variation of the BL brightness control value bd with the spatial LPF coefficient number L for identifying the spatial LPF coefficient K.
Note that the BL control value calculation unit 103, the frame memory 304, the space LPF selection unit 305, the leakage light reduction table data 306, the LPF coefficient table data 107, the LPF coefficient reading unit 108 and the space LPF application unit 109 function as the light emission control unit 55. Do.

(Process of Example 3)
FIG. 12 is a diagram illustrating an example of a flowchart of processing of the third embodiment. The process of the third embodiment will be described with reference to FIG. The processes of steps S101 to S104 are the same as the processes of steps S21 to S24 of FIG. That is, the BL control value calculation unit 103 acquires an RGB signal (video signal) in step S101, and converts a pixel value (RGB) into a color data luminance value Y in step S102. Subsequently, the BL control value calculation unit 103 calculates the average value YAG of the color data luminance values Y for each pixel area in step S103, and calculates the BL luminance control value bd for each BL control area in step S104.

  In step S105, the spatial LPF selection unit 305 acquires the BL brightness control value bd of the previous frame from the frame memory 304. The video signal input from the BL control value calculation unit 103 is sequentially stored in the frame memory 304, and the BL brightness control value bd one frame before is stored. Note that the space LPF selection unit 105 has already acquired the BL luminance control value bd of the current frame.

  In step S106, the spatial LPF selection unit 305 responds to changes in the BL light intensity control value bd from the leakage light reduction table data 306 based on the current frame in each BL control area and the BL brightness control value bd of the immediately preceding frame. The spatial LPF coefficient number L is selected.

FIG. 13 is a view showing a second example of the data structure of the leakage light reduction table data 306. As shown in FIG. Each row of the leakage light reduction table data 306 corresponds to the BL brightness control value bd of the previous frame, and each column corresponds to the BL brightness control value bd of the current frame. In the table of FIG. 13, the range of the BL brightness control value bd of one frame before to 3 to 253 and the range of the BL brightness control value bd of the current frame to 3 to 253 are omitted.
For example, according to the table of FIG. 13, when the BL brightness control value bd of one frame before is “1” and the BL brightness control value bd of the current frame is “2”, the spatial LPF coefficient number L is “9”. . When the BL brightness control value bd of one frame before is “2” and the BL brightness control value bd of the current frame is “0”, the spatial LPF coefficient number L is “9”. When the BL brightness control value bd of one frame before is “255” and the BL brightness control value bd of the current frame is “255”, the spatial LPF coefficient number L is “10”.

In step S107, the LPF coefficient reading unit 108 reads out and acquires the spatial LPF coefficient K corresponding to the spatial LPF coefficient number L from the LPF coefficient table data 107. In the LPF coefficient table data 107, for example, spatial LPF coefficients K of L = 0 to 10 are stored as in FIG.
In step S108, the spatial LPF application unit 109 calculates the backlight control value T of the BL control area by multiplying the spatial LPF coefficient K by the BL luminance control value bd using the equation (3). The processes in steps S107 and S108 are similar to the processes in steps S27 and S28 in FIG.
As described above, according to the third embodiment, since the spatial LPF coefficient K is selected based on the BL brightness control value bd calculated by the BL control value calculation unit 103, there is no need to acquire a video signal, and efficiency Processing can be performed. In addition, since the BL brightness control value bd is calculated using a video signal and has a relationship substantially proportional to the color data brightness value, substantially the same control as that of the first embodiment can be performed.

Although the liquid crystal panel 101 is used as the display panel in the above embodiment, a display panel of a method of modulating light with a device other than a liquid crystal element may be used. For example, the present invention may be applied to a MEMS shutter type display panel using a MEMS (Micro Electro Mechanical System) shutter.

100: display device, 101: liquid crystal panel, 102: backlight, 103: BL control value calculation unit, 104: frame memory, 105: space LPF selection unit, 106: leakage light reduction table data, 107: LPF coefficient table data, 108: LPF coefficient reading unit, 109: space LPF application unit

Claims (10)

A display panel having a plurality of pixels,
A display control unit that controls the display panel according to the input image data;
Illumination means having a plurality of light emission means disposed on the back side of the display panel;
Light emission control means for controlling the light emission intensity for each control area included in the illumination means;
The display device, wherein the light emission control means executes a process of controlling a difference in light emission intensity with a surrounding control area in accordance with a time change amount of image data at a position corresponding to the control area.   The light emission control means performs a smoothing process to reduce the difference in light emission intensity between control areas as a process of controlling the difference in light emission intensity, and the time change amount of the image data of the position corresponding to the control area is large The display device according to claim 1, wherein the degree of smoothing is reduced as much as possible.   The light emission control means is characterized in that, as the smoothing process, the degree of smoothing is increased after controlling the degree of smoothing according to the amount of time change of the image data of the position corresponding to the control area. The display device according to 2.   4. The display device according to claim 2, wherein the smoothing process is a process of applying a spatial LPF to the light emission control amount of each control area. It further comprises a storage unit for storing a plurality of spatial LPFs including different coefficients,
The light emission control means is characterized in that, as smoothing processing, a space LPF corresponding to a time change amount of the image data is acquired from the storage unit, and the space LPF is applied to the light emission control amount of each control area. The display device according to claim 4.   The display apparatus according to any one of claims 1 to 5, wherein the light emission control unit sets a difference between image data of one frame before and a current frame as a time change amount of the image data.   7. The light emission control means according to claim 6, wherein a difference between average values of pixel values of the area of the display panel corresponding to a control area of one frame before and the current frame is a time change amount of the image data. The display device as described in.   The light emission control means calculates the luminance value from the pixel values of the area of the display panel corresponding to the control area of one frame before and the current frame, and the difference of the average value of the luminance value is the time variation of the image data The display device according to claim 6, wherein:   The light emission control means calculates the light emission control amount calculated on the basis of the image data of the position corresponding to the control area for one frame previous and the current frame, and the difference between the light emission control amount between one frame previous and the current frame The display device according to any one of claims 1 to 5, wherein is a time change amount of the image data. A display panel having a plurality of pixels,
A display control unit that controls the display panel according to the input image data;
And a lighting unit having a plurality of light emitting units disposed on the back side of the display panel.
Controlling the light emission intensity for each control area included in the illumination means;
A display apparatus characterized in that, in the step of controlling the light emission intensity, a process of controlling a difference in light emission intensity with a surrounding control area according to a time change amount of image data of a position corresponding to the control area. Control method.

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