JP6746464B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device.

Conventionally, as a technique for improving the contrast of a liquid crystal display device, a technique has been proposed in which two display panels are superposed and an image is displayed on each display panel based on an input video signal (for example, Patent Document 1). reference). Specifically, for example, a color image is displayed on the front (observer side) display panel of the two front and rear display panels, and a monochrome image is displayed on the rear (backlight side) display panel. As a result, the contrast is improved. Further, in the above liquid crystal display device, filter processing (expansion filter processing) for expanding the high-luminance region of a monochrome image is performed so that a desired image can be visually recognized without causing image shift even when the display screen is viewed from an oblique direction. Is going. For example, in the above-described extended filter process, a process of setting a 3×3 pixel area as a filter size and setting a maximum gradation value within the filter size as a gradation value of a pixel (pixel of interest) in the center of the pixel area is performed. This is done for all pixels in the frame.

WO2007/040139

However, in the above-described conventional liquid crystal display device, since the expanded filter processing is performed by a filter having a common size (3×3 pixel area in the above example) for all pixels in each frame, the brightness of the entire black and white image is high. Become. Therefore, for example, an image in which a black image is floated in a dark area of the display image is visually recognized, which may cause a problem that the display quality is deteriorated.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress deterioration of display quality in a dark region of a display image in a liquid crystal display device configured by stacking a plurality of display panels. is there.

In order to solve the above problems, the liquid crystal display device according to the present invention is a display device in which a plurality of display panels are overlapped with each other, and an image is displayed on each of the display panels, which is close to an observer. A first display panel arranged to display a color image; a second display panel arranged to be farther from the observer than the first display panel to display a monochrome image; and the color image based on an input video signal. And an image processing unit that generates second image data corresponding to the black-and-white image, wherein the image processing unit has a color image of each color representing color information included in the input video signal. With respect to the first black-and-white image data that is black-and-white using the maximum value of the values, the area consisting of the pixel of interest and the pixels around the pixel of interest is used as the filter size, and the maximum value of the luminance within the filter size is An extension filter processing unit that executes an extension filter process that sets the luminance of the pixel of interest, and a luminance difference in the second black-and-white image data that is black and white using the luminance signal calculated based on the value of each color representing the color information is determined. A black-and-white image corresponding to the second black-and-white image data has a first region having a first brightness difference and a second brightness difference smaller than the first brightness difference. In the case of including the second area, the extension filter processing unit performs the extension filter processing on the first black-and-white image data in the area corresponding to the first area with a filter size including a first number of pixels. And executing the extended filtering process in a region corresponding to the second region with a filter size having a second pixel number smaller than the first pixel number.

In the liquid crystal display device according to the present invention, the expansion filter processing unit may execute the expansion filter processing with a smaller filter size as the brightness difference is smaller.

The liquid crystal display device according to the present invention further includes a table that stores the brightness differences classified into a plurality of levels and the filter size corresponding to each level in association with each other, and the extension filter processing unit refers to the table. , The filter size corresponding to the brightness difference may be selected.

In the liquid crystal display device according to the present invention, the extended filter processing unit, when the target pixel corresponds to white, and the pixels around the target pixel correspond to red, the target pixel corresponds to white, In addition, the extended filter processing may be executed with a larger filter size than in the case where the pixels around the target pixel correspond to white.

In the liquid crystal display device according to the present invention, the image processing unit may execute a differential filter process that detects a boundary where the brightness changes in the second black-and-white image data, based on the brightness signal.

In the liquid crystal display device according to the present invention, the image processing unit has a filter size common to all pixels with respect to the second black-and-white image data subjected to the differential filter processing, and sets a maximum value of luminance to a target pixel. You may perform the common expansion filter process set to the brightness|luminance of.

In the liquid crystal display device according to the present invention, the brightness difference determination unit may determine a brightness difference in the second black-and-white image data that has been subjected to the common extension filter processing.

In the liquid crystal display device according to the present invention, the image processing unit performs smoothing processing on the first black-and-white image data that has been subjected to the extended filter processing with a filter size common to all pixels, The second image data may be generated.

The liquid crystal display device according to the present invention further includes a storage unit that stores a plurality of filter tables in which brightness differences classified into a plurality of levels and filter sizes corresponding to the respective levels are stored, and the extended filter processing unit is The gamma setting information may be acquired, the filter table may be selected from the storage unit based on the acquired gamma setting information, and the extended filter processing may be executed with reference to the selected filter table.

In the liquid crystal display device according to the present invention, the gamma setting information may be information on a gamma value set in a system provided outside the liquid crystal display device based on the input video signal.

In the liquid crystal display device according to the present invention, the storage unit includes a first filter table and a second filter table, and the first filter table has a plurality of pixels in a range in which the brightness difference is equal to or more than a first threshold value. Is set, and a filter size made up of one pixel is set in the range in which the brightness difference is less than the first threshold value. In the second filter table, the brightness difference is larger than the first threshold value. A filter size made up of a plurality of pixels is set in a range equal to or greater than a second threshold, and a filter size made up of one pixel is set in a range in which the brightness difference is less than the second threshold. May select the first filter table when the gamma setting information is information corresponding to SDR video, and may select the second filter table when the gamma setting information is information corresponding to HDR video. ..

In the liquid crystal display device according to the present invention, a storage unit that stores a plurality of filter tables in which the brightness difference and the filter size are associated with each other, and an analysis unit that analyzes characteristics of a brightness distribution of an image based on the input video signal. Further, the extended filter processing unit selects the filter table from the storage unit based on the analyzed luminance distribution, and executes the extended filter process by referring to the selected filter table. Good.

In the liquid crystal display device according to the present invention, the image processing unit is subjected to a differential filter process for detecting a boundary where brightness changes in the second black-and-white image data, and the differential filter process based on the brightness signal. For the second black-and-white image data, a common expansion filter process is executed to set the maximum value of brightness to the brightness of the pixel of interest with a filter size common to all pixels, and the image processing unit is configured to perform the common expansion. The analysis unit may further include a frame memory that stores the second black-and-white image data that has been subjected to the filtering process, and the analysis unit may determine a characteristic of the luminance distribution based on the image of the second black-and-white image data stored in the frame memory. May be analyzed.

In the liquid crystal display device according to the present invention, the storage unit includes a first filter table and a second filter table, and the first filter table has a plurality of pixel numbers in a range in which the brightness difference is equal to or more than the first brightness difference. Is set, and a filter size consisting of one pixel is set in the range where the brightness difference is less than the first brightness difference. In the second filter table, the brightness difference is greater than or equal to the second brightness difference. , A filter size made up of a plurality of pixels is set, and a filter size made up of one pixel is set in a range where the brightness difference is less than a second brightness difference. If the width of the brightness distribution is smaller than two brightness differences and the width of the brightness distribution is narrower than a threshold, the extended filter processing unit selects the first filter table, and if the width of the brightness distribution is wider than the threshold, the second filter table. May be selected.

In the liquid crystal display device according to the present invention, when the brightness difference is smaller than a threshold value, the expansion filter processing unit executes the expansion filter process with a filter size composed of one pixel, and the threshold value is the input image. It may be set based on the characteristics of the signal.

According to the liquid crystal display device of the present invention, it is possible to suppress deterioration of display quality in a dark region of a display image in a liquid crystal display device configured by stacking a plurality of display panels.

FIG. 1 is a plan view showing a schematic configuration of a liquid crystal display device according to this embodiment. It is a top view showing a schematic structure of the 1st display panel concerning this embodiment. It is a top view which shows schematic structure of the 2nd display panel which concerns on this embodiment. FIG. 4 is a cross-sectional view taken along the line AA′ of FIGS. 2 and 3. It is a top view which shows the other example of a pixel arrangement of a 1st display panel and a 2nd display panel. 3 is a block diagram showing a specific configuration of an image processing unit according to the first embodiment. FIG. It is a figure which shows an example of the image produced|generated by each process of an image processing part. It is an example of an operator used in a differential filter process. FIG. 6 is a diagram showing an example of a filter table according to the first embodiment. It is a figure which shows an example of the filter size selected based on 2nd monochrome image data. It is a figure which shows an example of the image before and behind the expansion filter process with respect to 1st monochrome image data. It is a figure which shows an example of the image produced|generated by the smoothing process of an image processing part. It is a figure which shows an example of the image displayed on a 1st display panel and a 2nd display panel in the conventional structure. FIG. 6 is a diagram showing an example of images displayed on a first display panel and a second display panel in the configuration according to the first embodiment. FIG. 7 is a diagram showing an example of data input to an image processing unit according to the second embodiment. 9 is a block diagram showing a specific configuration of an image processing unit according to the second embodiment. FIG. FIG. 9 is a diagram showing an example of a filter table according to the second embodiment. FIG. 9 is a block diagram showing a modified example 1 of the image processing unit according to the second embodiment. FIG. 9 is a block diagram showing a modified example 2 of the image processing unit according to the second embodiment. It is a figure which shows the histogram of the brightness difference in the image after a 1st extended filter process. FIG. 9 is a diagram showing another example of the filter table according to the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings. The liquid crystal display device according to the present embodiment controls a plurality of display panels that display an image, a plurality of drive circuits (a plurality of source drivers, a plurality of gate drivers) that drive each display panel, and each drive circuit. A plurality of timing controllers, an image processing unit that performs image processing on an input video signal input from the outside and outputs image data to each timing controller, and a plurality of display panels is irradiated with light from the back side. Including a backlight. The number of display panels is not limited and may be two or more. Further, the plurality of display panels are arranged so as to be overlapped with each other in the front-back direction when viewed from the viewer side, and each display an image. Hereinafter, the liquid crystal display device 10 including the two display panels will be described as an example.

FIG. 1 is a plan view showing a schematic configuration of a liquid crystal display device 10 according to this embodiment. As shown in FIG. 1, the liquid crystal display device 10 is disposed at a first display panel 100 arranged at a position close to the observer (front side) and at a position farther from the observer than the first display panel 100 (rear side). A second display panel 200, a first timing controller 140 for controlling a first source driver 120 and a first gate driver 130 provided on the first display panel 100, and a second source provided on the second display panel 200. It includes a second timing controller 240 that controls the driver 220 and the second gate driver 230, and an image processing unit 300 that outputs image data to the first timing controller 140 and the second timing controller 240. The first display panel 100 displays a color image according to the input video signal in the first image display area 110, and the second display panel 200 displays a monochrome image according to the input video signal in the second image display area 210. The image processing unit 300 receives the input video signal Data transmitted from an external system (not shown), performs image processing described below, and then outputs the first image data DAT1 to the first timing controller 140, The second image data DAT2 is output to the second timing controller 240. The image processing unit 300 also outputs a control signal (not shown in FIG. 1) such as a synchronization signal to the first timing controller 140 and the second timing controller 240. The first image data DAT1 is image data for displaying a color image, and the second image data DAT2 is image data for displaying a monochrome image. The backlight (omitted in FIG. 1) is arranged on the back side of the second display panel 200. The specific configuration of the image processing unit 300 will be described later.

FIG. 2 is a plan view showing a schematic configuration of the first display panel 100, and FIG. 3 is a plan view showing a schematic configuration of the second display panel 200. FIG. 4 is a sectional view taken along the line AA′ of FIGS. 2 and 3.

The configuration of the first display panel 100 will be described with reference to FIGS. 2 and 4. As shown in FIG. 4, the first display panel 100 includes a thin film transistor substrate 101 (hereinafter referred to as a TFT substrate) arranged on the backlight 400 side and a color filter arranged on the observer side and facing the TFT substrate 101. A substrate 102 (hereinafter referred to as a CF substrate) and a liquid crystal layer 103 arranged between the TFT substrate 101 and the CF substrate 102 are included. A polarizing plate 104 is arranged on the backlight 400 side of the first display panel 100, and a polarizing plate 105 is arranged on the observer side.

As shown in FIG. 2, the TFT substrate 101 has a plurality of data lines 111 extending in a first direction (eg, column direction) and a second direction (eg, row direction) different from the first direction. A plurality of gate lines 112 are formed, and a thin film transistor 113 (hereinafter referred to as a TFT) is formed near each intersection of the plurality of data lines 111 and the plurality of gate lines 112. In a plan view of the first display panel 100, a region surrounded by two adjacent data lines 111 and two adjacent gate lines 112 is defined as one sub pixel 114, and the sub pixel 114 is a matrix. A plurality of cells are arranged in a row (row direction and column direction). The plurality of data lines 111 are arranged at equal intervals in the row direction, and the plurality of gate lines 112 are arranged at equal intervals in the column direction. On the TFT substrate 101, a pixel electrode 115 is formed for each sub pixel 114, and one common electrode (not shown) common to the plurality of sub pixels 114 is formed. The drain electrode of the TFT 113 is electrically connected to the data line 111, the source electrode is electrically connected to the pixel electrode 115, and the gate electrode is electrically connected to the gate line 112.

As shown in FIG. 4, a plurality of colored portions 102 a are formed on the CF substrate 102 so as to correspond to each sub-pixel 114. Each colored portion 102a is surrounded by a black matrix 102b that blocks transmission of light, and is formed in, for example, a rectangular shape. Further, the plurality of colored portions 102a are formed of a red (R color) material and transmit a red light, and a green portion formed of a green (G color) material and transmit a green light. , A blue portion formed of a blue (B) material and transmitting blue light. The red part, the green part, and the blue part are repeatedly arranged in this order in the row direction, the colored parts of the same color are arranged in the column direction, and the black matrix 102b is provided at the boundary part between the colored parts 102a adjacent in the row direction and the column direction. Are formed. As shown in FIG. 2, the plurality of sub-pixels 114 corresponding to each colored portion 102a correspond to a red sub-pixel 114R corresponding to a red portion, a green sub-pixel 114G corresponding to a green portion, and a blue portion. And a blue sub-pixel 114B. In the first display panel 100, one red sub-pixel 114R, one green sub-pixel 114G and one blue sub-pixel 114B constitute one pixel 124, and a plurality of pixels 124 are arranged in a matrix. ing.

The first timing controller 140 has a known configuration. For example, the first timing controller 140, based on the first image data DAT1 output from the image processing unit 300 and the first control signal CS1 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.), the first image data DA1. And various timing signals (data start pulse DSP1, data clock DCK1, gate start pulse GSP1, gate clock GCK1) for controlling the driving of the first source driver 120 and the first gate driver 130 (see FIG. 2). ). The first timing controller 140 outputs the first image data DA1, the data start pulse DSP1, and the data clock DCK1 to the first source driver 120, and outputs the gate start pulse GSP1 and the gate clock GCK1 to the first gate driver 130. Output.

The first source driver 120 outputs a data signal (data voltage) corresponding to the first image data DA1 to the data line 111 based on the data start pulse DSP1 and the data clock DCK1. The first gate driver 130 outputs a gate signal (gate voltage) to the gate line 112 based on the gate start pulse GSP1 and the gate clock GCK1.

A data voltage is supplied from the first source driver 120 to each data line 111, and a gate voltage is supplied from the first gate driver 130 to each gate line 112. The common voltage Vcom is supplied to the common electrode from a common driver (not shown). When the gate voltage (gate-on voltage) is supplied to the gate line 112, the TFT 113 connected to the gate line 112 is turned on, and the data voltage is supplied to the pixel electrode 115 via the data line 111 connected to the TFT 113. .. An electric field is generated by the difference between the data voltage supplied to the pixel electrode 115 and the common voltage Vcom supplied to the common electrode. An image is displayed by driving the liquid crystal by this electric field to control the light transmittance of the backlight 400. In the first display panel 100, color image display is performed by supplying a desired data voltage to the data line 111 connected to the pixel electrode 115 of each of the red sub-pixel 114R, the green sub-pixel 114G, and the blue sub-pixel 114B. Be seen. The first display panel 100 may have a known configuration.

Next, the configuration of the second display panel 200 will be described with reference to FIGS. 3 and 4. As shown in FIG. 4, the second display panel 200 includes a TFT substrate 201 disposed on the backlight 400 side, a CF substrate 202 disposed on the viewer side and facing the TFT substrate 201, the TFT substrate 201 and the CF substrate 201. And a liquid crystal layer 203 disposed between the substrates 202. A polarizing plate 204 is arranged on the backlight 400 side of the second display panel 200, and a polarizing plate 205 is arranged on the observer side. A diffusion sheet 301 is arranged between the polarizing plate 104 of the first display panel 100 and the polarizing plate 205 of the second display panel 200.

As shown in FIG. 3, a plurality of data lines 211 extending in the column direction and a plurality of gate lines 212 extending in the row direction are formed on the TFT substrate 201, and the plurality of data lines 211 and the plurality of data lines 211 are formed. A TFT 213 is formed near each intersection with the gate line 212. In a plan view of the second display panel 200, a region surrounded by two adjacent data lines 211 and two adjacent gate lines 212 is defined as one pixel 214, and the pixel 214 is arranged in a matrix ( Multiple rows are arranged in the row direction and the column direction. The plurality of data lines 211 are arranged at equal intervals in the row direction, and the plurality of gate lines 212 are arranged at equal intervals in the column direction. On the TFT substrate 201, a pixel electrode 215 is formed for each pixel 214, and one common electrode (not shown) common to the plurality of pixels 214 is formed. The drain electrode of the TFT 213 is electrically connected to the data line 211, the source electrode is electrically connected to the pixel electrode 215, and the gate electrode is electrically connected to the gate line 212. The sub-pixels 114 of the first display panel 100 and the pixels 214 of the second display panel 200 are arranged in a one-to-one relationship with each other and overlap each other in a plan view. For example, each of the red sub-pixel 114R, the green sub-pixel 114G, and the blue sub-pixel 114B included in the pixel 124 illustrated in FIG. 2 and each of the three pixels 214 illustrated in FIG. 3 overlap each other in a plan view. As shown in FIG. 5, the three sub-pixels 114 (red sub-pixel 114R, green sub-pixel 114G, blue sub-pixel 114B) of the first display panel 100 (see FIG. 5A) and the second display are shown. One pixel 214 of the panel 200 (see FIG. 5B) may overlap in a plan view.

As shown in FIG. 4, a black matrix 202b that blocks the transmission of light is formed on the CF substrate 202 at a position corresponding to the boundary portion of each pixel 214. In the area 202a surrounded by the black matrix 202b, no colored portion is formed, but an overcoat film is formed, for example.

The second timing controller 240 has a known configuration. For example, the second timing controller 240, based on the second image data DAT2 output from the image processing unit 300 and the second control signal CS2 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.), the second image data DA2. And various timing signals (data start pulse DSP2, data clock DCK2, gate start pulse GSP2, gate clock GCK2) for controlling the driving of the second source driver 220 and the second gate driver 230 (see FIG. 3). ). The second timing controller 240 outputs the second image data DA2, the data start pulse DSP2, and the data clock DCK2 to the second source driver 220, and outputs the gate start pulse GSP2 and the gate clock GCK2 to the second gate driver 230. Output.

The second source driver 220 outputs a data voltage corresponding to the second image data DA2 to the data line 211 based on the data start pulse DSP2 and the data clock DCK2. The second gate driver 230 outputs a gate voltage to the gate line 212 based on the gate start pulse GSP2 and the gate clock GCK2.

The data voltage is supplied from the second source driver 220 to each data line 211, and the gate voltage is supplied from the second gate driver 230 to each gate line 212. A common voltage Vcom is supplied to the common electrode from the common driver. When the gate voltage (gate-on voltage) is supplied to the gate line 212, the TFT 213 connected to the gate line 212 is turned on, and the data voltage is supplied to the pixel electrode 215 via the data line 211 connected to the TFT 213. .. An electric field is generated by the difference between the data voltage supplied to the pixel electrode 215 and the common voltage Vcom supplied to the common electrode. An image is displayed by driving the liquid crystal by this electric field to control the light transmittance of the backlight 400. On the second display panel 200, a monochrome image display is performed. The second display panel 200 may have a known configuration.

[Embodiment 1]
FIG. 6 is a block diagram showing a specific configuration of the image processing unit 300 according to the first embodiment. The image processing unit 300 includes a first delay unit 311, a gamma processing unit 312, a first image output unit 313, a first black and white image generation unit 331, a second delay unit 332, and a second black and white image generation unit 321. A differential filter processing unit 322, a first extended filter processing unit 323, a brightness difference determination unit 324, a second extended filter processing unit 325, a filter table 326, an average value filter processing unit 327, and a third delay. The unit 328 and the second image output unit 329 are included. The image processing unit 300 performs the following image processing based on the input video signal Data, and outputs the first image data DAT1 (color image data) for the first display panel 100 and the second image data for the second display panel 200. DAT2 (monochrome image data) is generated.

Upon receiving the input video signal Data transmitted from the external system, the image processing unit 300 transfers the input video signal Data to the first delay unit 311, the first monochrome image generation unit 331, and the second monochrome image generation unit 321. Forward. The input video signal Data includes, for example, brightness information (gradation information) and color information. The color information is information for specifying a color. For example, when the input video signal Data is 8 bits, each color of a plurality of colors including R color, G color, and B color is represented by a value of 0 to 255. You can The plurality of colors may include at least R color, G color and B color, and may further include W (white) color and/or Y (yellow) color. In the following, as an example, a case where the plurality of colors are R color, G color and B color will be described. Further, hereinafter, the color information of the input video signal Data is referred to as “RGB value” ([R value, G value, B value]). For example, when the color corresponding to the input video signal Data is “white”, the value of R color (R value) is represented by [255], the value of G color (G value) is represented by [255], and B The color value (B value) is represented by [255]. That is, the “RGB value” is represented by [255, 255, 255]. When the color corresponding to the input video signal Data is “red”, the “RGB value” is represented by [255,0,0], and when the color is “black”, the “RGB value” is [0,0]. , 0].

Image A in FIG. 7A shows an example of an image (input image) corresponding to the input video signal Data. When the first black-and-white image generation unit 331 acquires the input video signal Data, it is the maximum value among the values (here, RGB value: [R value, G value, B value]) of each color indicating the color information of the input video signal Data. The (R value, G value, or B value) is used to generate monochrome image data corresponding to a monochrome image (hereinafter referred to as first monochrome image data). Specifically, the first black-and-white image generation unit 331 generates the first black-and-white image data by setting the maximum value of the RGB values corresponding to each pixel 214 to the value of the pixel 214. .. The first black-and-white image generation unit 331 outputs the generated first black-and-white image data to the second delay unit 332.

When the second black-and-white image generation unit 321 acquires the input video signal Data, the second black-and-white image generation unit 321 uses the luminance signal Y of the input video signal Data to generate black-and-white image data corresponding to the black-and-white image (hereinafter referred to as second black-and-white image data). To do. Specifically, the second monochrome image generation unit 321 calculates the luminance signal Y from the RGB value ([R value, G value, B value]) of the input video signal Data, and based on the luminance signal Y, the second monochrome image. Generate image data. The luminance signal Y can be calculated, for example, by the well-known conversion formula (1) shown below.
Y=0.299×R value+0.587×G value+0.114×B value (1)

When the differential filter processing unit 322 acquires the second black-and-white image data from the second black-and-white image generation unit 321, the differential filter processing unit 322 detects (emphasizes) a boundary (edge) at which the luminance greatly changes with respect to the second black-and-white image data. Filter processing (edge detection processing) is executed. The differential filter processing unit 322 performs the differential filter processing using, for example, a Prewitt filter or a Sobel filter. For example, the differential filter processing unit 322 uses the Prewitt filter using the operator in the X-axis (horizontal) direction shown in FIG. 8A and the operator in the Y-axis (vertical) direction shown in FIG. Perform processing. According to the differential filtering process, the low-frequency component is deleted, so that an edge having a large luminance change can be emphasized. Image B in FIG. 7B shows an image generated by the differential filtering process. The operator used for the differential filter processing is not limited to the operators shown in FIGS. 8(a) and 8(b). A well-known method can be applied to the differential filter processing.

When the first extension filter processing unit 323 acquires the second black-and-white image data that has been subjected to the differential filter processing, the first extension filter processing unit 323 has a high brightness with respect to the second black-and-white image data with a filter size common to all pixels in each frame. Extended filter processing (first extended filter processing) for expanding the area is executed. For example, the first extension filter processing unit 323 sets, for each pixel 214 (pixel of interest), a 19×19 pixel region composed of nine pixels in the upper, lower, left, and right surroundings as a filter size, and sets the maximum value of the luminance within this filter size. The process of setting the brightness of the pixel (pixel of interest) is executed. The filter size is not limited to the 19×19 pixel area, but is set to a common filter size for all pixels 214 in each frame. Further, the filter shape is not limited to a square shape and may be a circular shape. An image C in FIG. 7C shows an image generated by the first extended filter processing. As shown in FIG. 7C, it can be seen that the high-brightness region of the image B in FIG. 7B extends with the same width. A well-known method can be applied to the first extended filter processing.

When the brightness difference determination unit 324 acquires the second black-and-white image data that has been subjected to the first extended filter processing, the brightness difference determination unit 324 determines the difference (brightness difference) at the boundary portion of the brightness in the second black-and-white image data. In the image C shown in FIG. 7C, the brightness difference increases as it approaches the upper side in the figure, and the brightness difference decreases as it approaches the lower side in the figure. The luminance difference determination unit 324 outputs the determination result (luminance difference) to the second extended filter processing unit 325. When the input video signal Data is 8 bits, the brightness difference is represented by 0 to 255 gradations.

The second delay unit 332 matches the first monochrome image data acquired from the first monochrome image generation unit 331 with the output timing of the determination result (luminance difference) in the luminance difference determination unit 324, and the second extended filter processing unit 325. Output to.

When the second expansion filter processing unit 325 acquires the first monochrome image data and the determination result (luminance difference) from the second delay unit 332 and the luminance difference determination unit 324, respectively, the second extension filter processing unit 325 determines the first monochrome image data based on the luminance difference. The extended filter processing (second extended filter processing) for expanding the high-luminance region is executed for.

Specifically, first, the second expansion filter processing unit 325 refers to the filter table 326 and selects a filter size corresponding to the above determination result (luminance difference). In the filter table 326, 0 to 255 gradations are classified into a plurality of levels as the brightness difference, and the filter size corresponding to each level is stored in association with each other. FIG. 9 is a diagram showing an example of the filter table 326 (LUT), in which 0 to 255 gradations are classified into 7 levels as a brightness difference, and a filter size is associated with each level. .. In the filter table 326, the smaller the brightness difference, the smaller the filter size, and the larger the brightness difference, the larger the filter size. In the example of the image C in FIG. 7C, as shown in FIG. 10, the filter size of 13×13 pixel area is selected in the uppermost area where the brightness difference is maximum, and the lower area where the brightness difference becomes smaller is selected. The closer it is, the smaller filter size is selected. In addition, the filter size of the 1×1 pixel region is selected in the vicinity of the lowermost portion (0 to 15 gradations) where the brightness difference is small.

Next, the second expansion filter processing unit 325 expands the high-luminance region by the selected filter size with respect to the first monochrome image data acquired from the second delay unit 332 (second expansion filter processing). ) Is executed. That is, the second extension filter processing unit 325 executes processing for each pixel 214 (pixel of interest) to set the maximum value of the brightness within the selected filter size to the brightness of that pixel (pixel of interest). FIG. 11A shows an image D corresponding to the first black-and-white image data and the selected filter size (see FIG. 10) for executing the second extended filter processing on the image D. , Image D in FIG. 11B shows an image generated by the second extended filter processing. According to the second expansion filter process, as shown in FIG. 11B, the high brightness area is expanded as a whole, and the higher the brightness area is, the closer the area is to the upper area in the drawing, which is the area where the brightness difference is large. Expands, and the high-brightness area shrinks as it approaches the area on the lower side in the drawing, which is the area where the brightness difference is small. Further, in the vicinity of the lowermost portion (0 to 15 gradations) where the brightness difference is small, the second expansion filter processing is performed with the filter size of the 1×1 pixel area, so that the image (high brightness area width) shown in FIG. Will be the same. In addition, when the filter size of the 1×1 pixel area is selected, the second expansion filter processing unit 325 may not execute the second expansion filter processing (turn off the second expansion filter processing).

When the average value filter processing unit 327 acquires the first black-and-white image data that has been subjected to the second extended filter processing, the average-value filter processing unit 327 performs an average-value filter common to all the pixels 214 in each frame on the first black-and-white image data. To perform the smoothing process. For example, the average value filter processing unit 327 sets, for each pixel 214 (pixel of interest), an average value of luminance within this filter size, with a 19×19 pixel region including nine pixels in the upper, lower, left, and right surroundings as a filter size. The process of setting the luminance of the pixel 214 (pixel of interest) is executed. The filter size is not limited to the 19×19 pixel area, but is set to a common filter size for all pixels 214 in each frame. Further, the filter shape is not limited to a square shape and may be a circular shape. According to the smoothing process, the high-frequency component is deleted, so that the change in brightness can be smoothed. The image F in FIG. 12 shows an image generated by the smoothing process. As shown in FIG. 12, it can be seen that the luminance boundary portion (outline) in the image E of FIG. 11 is blurred and the luminance change is smooth. The average value filter processing unit 327 outputs the first black-and-white image data that has been subjected to the smoothing process to the gamma processing unit 312 and the third delay unit 328.

The gamma processing unit 312, based on the first black-and-white image data acquired from the average value filter processing unit 327, for the input video signal Data acquired from the first delay unit 311, a color image displayed on the first display panel 100. Gamma processing of. For example, the gamma processing unit 312 sets the gamma value of the color image so that the combined gamma value of the display image in which the monochrome image and the color image are combined is 2.2. The gamma processing unit 312 outputs the color image data subjected to the gamma processing to the first image output unit 313.

The third delay unit 328 outputs the first smoothed black-and-white image data to the second image output unit 329 at the output timing of the color image data in the gamma processing unit 312.

The first image output unit 313 outputs the color image data as the first image data DAT1 to the first timing controller 140, and the second image output unit 329 sets the first monochrome image data as the second image data DAT2 at the second timing. Output to the controller 240. Further, the image processing unit 300 outputs the first control signal CS1 to the first timing controller 140 and the second control signal CS2 to the second timing controller 240 (FIGS. 2 and 3).

As described above, in the image processing unit 300 according to the present embodiment, in particular, the second extended filter processing unit 325 changes the filter size according to the brightness difference of the image (black and white image) and performs the extended filter processing (second It has a configuration for executing (extended filter processing). FIG. 13 shows an image (color image) displayed on the first display panel and an image (black and white image) displayed on the second display panel in the conventional configuration. FIG. 14 shows an image (color image) displayed on the first display panel 100 and an image (black and white image) displayed on the second display panel 200 in the configuration according to the present embodiment. As shown in FIGS. 13 and 14, in the configuration according to the present embodiment, the expansion width of the high-brightness region of the low gradation region (lower region in the figure) in the black-and-white image is It can be seen that the brightness difference becomes gradually narrower as the brightness difference becomes smaller (t2<t1). Therefore, according to the configuration of the present embodiment, the expansion width of the high-luminance region can be narrowed particularly in the low gradation region, and thus the appearance of the black floating image in the dark region that can occur in the conventional configuration can be suppressed. .. In addition, by dynamically changing the size of the expansion filter in the intermediate region between the perceived luminance difference and the non-perceived luminance difference, it is possible to significantly reduce the flare generated in the bright spot image.

Here, although the brightness difference differs depending on the color, since the colors are not distinguished in the method of black and white using the maximum value of RGB values, for example, in the case of an image composed of white and red, the area corresponding to the red part is The expansion filter is relatively strong. As a result, black floating may occur in the red area. Particularly when viewed from an angle, the black floating may be noticeable. In this respect, in the present embodiment, the luminance signal Y is calculated from the RGB values, a black-and-white image (second black-and-white image data) is generated based on the luminance signal Y, and this black-and-white image is subjected to differential filter processing. .. As a result, the brightness difference in the area corresponding to the red portion becomes smaller, and the filter size selected by the second extended filter processing unit 325 for this peripheral area becomes smaller. That is, for example, when the target pixel corresponds to white (maximum brightness) and the pixels around the target pixel correspond to red (maximum brightness), the second expansion filter processing unit 325 determines that the target pixel is white (maximum brightness). ) And the pixels around the pixel of interest correspond to white (maximum brightness), the second extended filter processing is executed with a larger filter size. As a result, the brightness of the area corresponding to the red portion in the black-and-white image can be suppressed to a low level, and thus the black floating can be improved.

[Embodiment 2]
Embodiment 2 of the present invention will be described below with reference to the drawings. It should be noted that, for convenience of explanation, the same components as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Further, the terms defined in the first embodiment are used according to the definitions in the present embodiment unless otherwise specified.

In the liquid crystal display device 10 according to the second embodiment, the second expansion filter processing unit 325 expands the high-brightness area for the first black-and-white image data based on the characteristics such as the format of the video signal, the gamma value, and the brightness. The filter process (second extended filter process) is executed. Hereinafter, a specific configuration of the image processing unit 300 according to the second embodiment will be described.

FIG. 15 is a diagram illustrating an example of data input to the image processing unit 300 according to the second embodiment. The system 500 provided outside the liquid crystal display device 10 receives a video signal DA of a predetermined format from a signal source. The system 500 performs, for example, a process of converting the video signal DA into a video (input video signal Data) according to the characteristics of the display panel (first display panel 100, second display panel 200). A user such as a system administrator or an observer sets a desired gamma value on the setting screen of the system 500. For example, the user may set the gamma value according to the characteristic of the video signal DA on the setting screen of the system 500, or may set the gamma value according to the display characteristic of the first display panel 100 and the second display panel 200. The gamma value may be set, or the gamma value may be set according to other parameters. FIG. 15 shows an example of a gamma value setting screen. For example, the user selects any one of “γ2.2”, “γ2.4”, and “PQ (Perceptual Quantizer)” on the setting screen. The system 500 outputs the input video signal Data and the set information (gamma setting information) to the image processing unit 300.

FIG. 16 is a block diagram showing a specific configuration of the image processing unit 300 according to the second embodiment. The second extended filter processing unit 325 acquires the gamma setting information corresponding to the input video signal Data from the system 500. Upon acquiring the gamma setting information, the second extended filter processing unit 325 selects the filter table corresponding to the gamma setting information from the plurality of filter tables stored in the table storage unit 340. FIG. 17 shows two filter tables (first filter table and second filter table) stored in the table storage unit 340. For example, in the first filter table shown in FIG. 17A, the extension filter processing (second extension filter processing) is turned off when the determination result (luminance difference) in the luminance difference determination unit 324 is less than 16 gradations. 17B, the second filter table shown in FIG. 17B is set so that the extended filter processing (second extended filter processing) is turned off when the luminance difference is less than 48 gradations. .. That is, the gradation (threshold value) at which the second extended filter processing is switched on/off is set to 16 gradations in the first filter table and 48 gradations in the second filter table. In the first filter table and the second filter table, the filter size of 1×1 pixel area (one pixel) is set in the area where the second extended filter processing is turned off. Further, in the first filter table and the second filter table, the filter size of 13×13 pixel region is set in the area where the brightness difference is maximum in the area where the second expansion filter processing is turned on, and the brightness difference is The smaller the filter size, the smaller the filter size is set.

The second expansion filter processing unit 325 refers to the selected filter table (for example, the first filter table or the second filter table), selects the filter size corresponding to the brightness difference, and selects the filter size according to the selected filter size. 2 Execute extended filter processing. The subsequent process is the same as the process of the image processing unit 300 according to the first embodiment.

According to the above configuration of the second embodiment, for example, when the characteristic of the video signal DA is an SDR (Standard Dynamic Range) video with a gamma value of 2.2, the second extended filter processing unit 325 causes the first filter table And executes the second extended filter processing. When the characteristic of the video signal DA has a gamma curve characteristic of a PQ curve (Perceptual Quantizer Curve) in HDR (High Dynamic Range) video, the second extended filter processing unit 325 refers to the second filter table, The second extended filter process is executed. Here, since the HDR video has a wider luminance range (dynamic range) than the SDR video, when the second extended filter processing is performed on the HDR video with reference to the first filter table, the brightness of the dark region becomes high and the black floating appears. The image and the noise image are easily visible. In this regard, according to the above configuration, for example, in the SDR video and the HDR video with the same original image, the second extended filter process is executed on the region of 16 to 47 gradations in the SDR video (see FIG. (a)), the second extended filter processing is not executed for the region of 0 to 47 gradations in the HDR video (see FIG. 17B). As a result, it is possible to suppress the appearance of a black floating image or a noise image that may be visually recognized in the HDR video. As described above, according to the above configuration, it is possible to appropriately suppress the appearance of an image that is blackened according to the characteristics of the video signal DA.

Here, in the above configuration, the second extended filter processing unit 325 of the image processing unit 300 is configured to acquire the gamma setting information output from the system 500 and select the filter table based on the gamma setting information. The processing unit 300 is not limited to the above configuration. FIG. 18 is a block diagram showing a specific configuration of the image processing unit 300 according to the first modification. The image processing unit 300 according to the first modification further includes a video characteristic analysis unit 341 in addition to the units of the image processing unit 300 according to the first embodiment. The image characteristic analysis unit 341 may receive the input image signal Data output from the system 500, analyze the characteristic of the input image signal Data, and acquire the gamma setting information. In this case, the second extended filter processing unit 325 acquires the gamma setting information from the video characteristic analysis unit 341.

FIG. 19 is a block diagram showing a specific configuration of the image processing unit 300 according to Modification 2. The image processing unit 300 according to the modified example 2 includes a frame memory 351 and a luminance distribution analysis unit 352 in addition to the units of the image processing unit 300 according to the first embodiment. The frame memory 351 stores the image (see FIG. 7C) generated by the first expansion filter processing by the first expansion filter processing unit 323 for each frame. The brightness distribution analysis unit 352 generates a brightness distribution (histogram) of the image in the frame memory 351, and detects the characteristics of the brightness distribution. For example, the brightness distribution analysis unit 352 detects the distribution width of the brightness distribution. FIG. 20A shows the luminance distribution in the image after the first extended filter processing based on the SDR video, and FIG. 20B shows the luminance distribution in the image after the first extended filter processing based on the HDR video. There is. 20A and 20B show the case where the original images are the same. When the brightness distribution analysis unit 352 detects the distribution width of the brightness distribution, the brightness distribution analysis unit 352 outputs the detection result to the second extended filter processing unit 325.

Upon acquiring the detection result (distribution width information), the second extended filter processing unit 325 selects a filter table corresponding to the distribution width from a plurality of filter tables (see FIG. 17) stored in the table storage unit 340. To do. The second expansion filter processing unit 325 refers to the selected filter table (first filter table or second filter table), selects the filter size corresponding to the brightness difference, and performs the second expansion according to the selected filter size. Perform filtering. For example, when the distribution width is narrower than the threshold value, the second extended filter processing unit 325 selects the first filter table and refers to the first filter table to execute the second extended filter process. When the distribution width is wider than the threshold value, the second extended filter processing unit 325 selects the second filter table and refers to the second filter table to execute the second extended filter processing.

The brightness distribution analysis unit 352 may detect a frequency peak value in the brightness distribution or a mean value of the brightness distribution as a feature of the brightness distribution. In this case, the second extended filter processing unit 325 may select the filter table based on the frequency peak value or the average value.

The liquid crystal display device 10 according to the second embodiment is not limited to the above configuration. For example, in the liquid crystal display device 10 according to the modified example 3, a plurality of threshold values for switching on/off of the second extended filter processing may be set in one filter table. For example, a first threshold and a second threshold are set in the filter table shown in FIG. In this case, for example, when the characteristic of the video signal DA is the SDR video and the gamma value is 2.2, the second extended filter processing unit 325 adopts the first threshold value (16 gradations) and refers to the filter table. , Second expanded filter processing is executed. That is, when the brightness difference is less than 16 gradations, the second expansion filter processing unit 325 turns off the second expansion filter processing. On the other hand, when the characteristic of the video signal DA has the gamma curve characteristic of the PQ curve in HDR video, the second extension filter processing unit 325 adopts the second threshold value (32 gradations) and refers to the filter table. , Second expanded filter processing is executed. That is, when the brightness difference is less than 32 gradations, the second expansion filter processing unit 325 turns off the second expansion filter processing. When the brightness difference is 16 gradations or more in the SDR video and when the brightness difference is 32 gradations or more in the HDR video, the second extended filter processing is executed with the filter size of the same filter table (see FIG. 21). ..

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and embodiments appropriately modified by those skilled in the art from the above-described embodiments without departing from the spirit of the present invention. Needless to say, it is included in the technical scope of the present invention.

10 liquid crystal display device, 100 first display panel, 120 first source driver, 130 first gate driver, 140 first timing controller, 200 second display panel, 220 second source driver, 230 second gate driver, 240 second Timing controller, 300 image processing unit, 311 first delay unit, 312 gamma processing unit, 313 first image output unit, 331 first black and white image generation unit, 332 second delay unit, 321 second black and white image generation unit, 322 differentiation Filter processing unit, 323 first expansion filter processing unit, 324 brightness difference determination unit, 325 second expansion filter processing unit, 326 filter table, 327 average value filter processing unit, 328 third delay unit, 329 second image output unit, 340 table storage unit, 341 video characteristic analysis unit, 351 frame memory, 352 luminance distribution analysis unit, 500 system.

Claims (15)

A display device in which a plurality of display panels are arranged in an overlapping manner and which displays an image on each of the display panels,
A first display panel which is arranged at a position close to an observer and displays a color image;
A second display panel arranged at a position farther from the observer than the first display panel and displaying a monochrome image;
An image processing unit for generating first image data corresponding to the color image and second image data corresponding to the monochrome image based on an input video signal;
Including,
The image processing unit, with respect to the first black-and-white image data black-and-white using the maximum value among the values of each color representing the color information included in the input video signal, the pixel of interest and the pixels around the pixel of interest. Is calculated based on a value of each color representing the color information, and an extension filter processing unit that executes an extension filter process that sets the maximum value of the luminance within the filter size to the luminance of the pixel of interest, using a region consisting of A brightness difference determination unit that determines a brightness difference calculated by a differential operation in each pixel of the second black-and-white image data that has been black and white using the brightness signal.
In the case where the monochrome image corresponding to the second monochrome image data includes a first area having a first brightness difference and a second area having a second brightness difference smaller than the first brightness difference,
The extension filter processing unit performs the extension filter processing on the first black-and-white image data in a region corresponding to the first region with a filter size including a first number of pixels, and in the second region. In the corresponding region, the extended filter processing is executed with a filter size including a second pixel number smaller than the first pixel number,
A liquid crystal display device characterized by the above. The expansion filter processing unit executes the expansion filter processing with a smaller filter size as the luminance difference is smaller,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The table further includes a table that stores the brightness differences classified into a plurality of levels and the filter size corresponding to each level in association with each other,
The extended filter processing unit refers to the table and selects the filter size corresponding to the luminance difference,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. When the pixel of interest corresponds to white and the pixels around the pixel of interest correspond to red, the extended filter processing unit corresponds to white and the pixels around the pixel of interest correspond to red. Compared to the case corresponding to white, the extended filter processing is executed with a larger filter size,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The image processing unit executes a differential filter process for detecting a boundary where the brightness changes in the second black-and-white image data, based on the brightness signal.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The image processing unit, for the second black-and-white image data that has been subjected to the differential filter processing, has a filter size common to all pixels and sets a maximum value of brightness to the brightness of the pixel of interest. To run the
The liquid crystal display device according to claim 5, wherein. The brightness difference determination unit determines a brightness difference in the second monochrome image data that has been subjected to the common expansion filter processing,
The liquid crystal display device according to claim 6, wherein the liquid crystal display device is a liquid crystal display device. The image processing unit generates the second image data by performing a smoothing process on the first black-and-white image data that has been subjected to the extended filter process with a filter size common to all pixels.
The liquid crystal display device according to claim 7, wherein the liquid crystal display device is a liquid crystal display device. Further comprising a storage unit that stores a plurality of filter tables in which brightness differences classified into a plurality of levels and filter sizes corresponding to the respective levels are associated with each other,
The extended filter processing unit acquires gamma setting information, selects the filter table from the storage unit based on the acquired gamma setting information, and executes the extended filter process by referring to the selected filter table. ,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The gamma setting information is information on a gamma value set in a system provided outside the liquid crystal display device based on the input video signal.
The liquid crystal display device according to claim 9, wherein. The storage unit includes a first filter table and a second filter table,
In the first filter table, a filter size including a plurality of pixels is set in a range in which the brightness difference is equal to or more than a first threshold, and a filter size including one pixel in a range in which the brightness difference is less than the first threshold. Is set,
In the second filter table, a filter size including a plurality of pixels is set in a range in which the brightness difference is larger than the first threshold and is equal to or larger than a second threshold, and one filter size is set in the range in which the brightness difference is less than the second threshold. The filter size consisting of pixels is set,
The extended filter processing unit selects the first filter table when the gamma setting information is information corresponding to SDR video, and selects the second filter table when the gamma setting information is information corresponding to HDR video. select,
The liquid crystal display device according to claim 9, wherein. A storage unit that stores a plurality of filter tables in which the brightness difference and the filter size are associated with each other, and an analysis unit that analyzes characteristics of a brightness distribution of an image based on the input video signal,
The extended filter processing unit selects the filter table from the storage unit based on the analyzed luminance distribution, and executes the extended filter process by referring to the selected filter table,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. The image processing unit detects, based on the brightness signal, a differential filter process for detecting a boundary where brightness changes in the second black-and-white image data, and the differential filter process for the second black-and-white image data. Then, with a filter size common to all pixels, a common extended filter process is performed to set the maximum value of brightness to the brightness of the pixel of interest,
The image processing unit further includes a frame memory that stores the second black-and-white image data that has been subjected to the common extended filter processing,
The analysis unit analyzes the characteristic of the luminance distribution based on the image of the second monochrome image data stored in the frame memory,
The liquid crystal display device according to claim 12, wherein. The storage unit includes a first filter table and a second filter table,
In the first filter table, a filter size including a plurality of pixels is set in the range where the brightness difference is equal to or larger than the first brightness difference, and a filter including one pixel is set in the range where the brightness difference is less than the first brightness difference. The size is set,
In the second filter table, a filter size including a plurality of pixels is set in the range in which the brightness difference is equal to or larger than the second brightness difference, and a filter including one pixel in the range in which the brightness difference is less than the second brightness difference. The size is set,
The first brightness difference is smaller than the second brightness difference,
The extended filter processing unit selects the first filter table when the width of the brightness distribution is narrower than a threshold value, and selects the second filter table when the width of the brightness distribution is wider than the threshold value.
The liquid crystal display device according to claim 12, wherein. When the brightness difference is smaller than a threshold value, the expansion filter processing unit executes the expansion filter processing with a filter size composed of one pixel,
The threshold value is set based on the characteristics of the input video signal,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.