JP2017173668A - Image display device and manufacturing method for image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the contrast ratio and improve the gradation expression capability by using two LCD panels.SOLUTION: An image display device includes a front-side LCD panel (1) and a rear-side LCD panel (2) overlapped on each other. An image is displayed by transmission of backlight in the order of the rear-side LCD panel and the front-side LCD panel. Each pixel of the front-side LCD panel is formed of RGB subpixels disposed side by side. Each pixel of the rear-side LCD panel is formed of a plurality of LV subpixels disposed in a direction orthogonal to the RGB subpixels. The image display device includes an LV controller (20) that individually controls the gradation characteristic and the range of lighting gradation value to be supplied to the plurality of LV subpixels in accordance with the concentration value of one gray image signal generated based on the input RGB image signal.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image display device and a method for manufacturing an image display device that improve the gradation ratio as well as the contrast ratio.

  In a conventional image display device using a single LCD panel, the input image is corrected by a polygonal line gamma with a panel driver, thereby realizing a linearity characteristic of the visual gradation.

  However, in reality, the luminance is expressed by the backlight illumination passing through the liquid crystal panel, so the gradation characteristics in the black region are particularly bad, and the luminance is observed in the brighter direction than the ideal luminance. The so-called black floating phenomenon occurs.

  This phenomenon occurs because when the LCD panel displays a dark region, the light shielding of the LCD panel is not complete and the backlight illumination light leaks. A conventional CRT has a contrast ratio of about 10,000: 1, and an organic EL panel has a contrast ratio of about 1,000,000: 1. However, due to this phenomenon, in a conventional image display device using a single LCD panel, a contrast ratio of only about 1500: 1 can be realized.

  Thus, in order to improve the contrast ratio of such a single LCD image display device, an image display device using two LCDs has been proposed (see, for example, Patent Documents 1 and 2). Each of the image display devices is configured to use two LCDs, and the contrast ratio is improved by adjusting the backlight transmission amount on the rear LCD and performing RGB display on the front LCD.

JP-A-5-88197 International Publication No. 2007/108183

However, the prior art has the following problems.
As described above, an image display device using a single LCD panel has a problem that a contrast ratio of only about 1500: 1 can be realized. Furthermore, one LCD has a major problem that faithful reproduction of an image cannot be realized due to a decrease in color reproducibility in a dark image or a deterioration in black quality.

  On the other hand, an image display device using two LCD panels as in Patent Documents 1 and 2 has an effect of improving contrast and preventing black float. However, such an image display device using two LCD panels has a problem that there is a limit in gradation expression capability, and will be described below with reference to the drawings.

  FIG. 15 is a diagram for explaining a problem in a conventional image display device using two LCD panels. In FIG. 16, an LCD panel on the back side of the backlight is referred to as an LV panel (Light Valve Panel), and an LCD panel on the front side that is close to a person viewing an image is referred to as an RGB panel.

  As shown in FIG. 15, the RGB panel has an RGB color filter and a sub-pixel structure. On the other hand, the LV panel has a size corresponding to one pixel of the RGB panel and a pixel structure without a color filter.

  The light emitted from the backlight unit arranged on the lower side of the LV panel passes through the LV panel and the RGB panel, and an image corresponding to the gradation given to each panel is displayed. With respect to the input RGB image, the LV panel performs a light valve operation in units of pixels, thereby eliminating black float and improving contrast.

  FIG. 16 is a diagram showing the gradation characteristics of the RGB panel and the LV panel in a conventional image display device using two LCD panels. Further, FIG. 17 is a diagram showing the combined transmittance in a conventional image display device using two LCD panels. In the conventional image display device using two LCD panels, the gradation characteristics as shown in FIG. 16 are set, and as shown in FIG. It is supposed to be.

  FIG. 18 is a diagram showing the correlation between the pixel values of both panels in a conventional image display device using two LCD panels. Both the RGB panel and the LV panel are generated as 8 bits, and the pixel value of the LV panel is generated based on the pixel value of the RGB panel. For this reason, as shown in FIG. 18, the pixel values of the RGB panel and the LV panel have a high correlation, and a composite gradation value exists around the y = x line. The logarithm is less than the theoretical value.

  In other words, the conventional image display device using two LCD panels can theoretically improve the contrast ratio, but it can fully exhibit the gradation expression capability because the panel driver is limited to only 8 bits. There was a problem that was not done.

  The present invention has been made to solve the above-described problems, and an image display device and an image that can improve contrast ratio and improve gradation expression capability using two LCD panels. An object is to obtain a method for manufacturing a display device.

  An image display device according to the present invention is configured by stacking two front side LCD panels and a rear side LCD panel, and displays an image by transmitting backlight in order of the rear side LCD panel and the front side LCD panel. Each pixel of the front side LCD panel is composed of RGB subpixels arranged in parallel, and each pixel of the rear side LCD panel is arranged in a direction orthogonal to the RGB subpixels The lighting gradation value to be supplied to the plurality of LV sub-pixels according to the gray value of one gray image signal generated from the input RGB image signal. An LV controller that individually controls the range and gradation characteristics is provided.

  In addition, the manufacturing method of the image display device according to the present invention is configured by stacking two front side LCD panels and two rear side LCD panels, and backlight is transmitted in the order of the rear side LCD panel and the front side LCD panel. A method of manufacturing an image display device that displays an image by configuring each pixel of the front side LCD panel with RGB sub-pixels arranged in parallel, according to the gradation value of each color of RGB The first step of manufacturing the front side LCD panel is provided with a circuit capable of individually controlling the liquid crystal transmittance of the corresponding RGB subpixel, and each pixel of the rear side LCD panel is orthogonal to the RGB subpixel. Liquid crystal transmittance of a plurality of LV sub-pixels corresponding to the gradation value of each color of RGB, which is composed of a plurality of LV sub-pixels arranged in the direction of The second step of manufacturing the rear LCD panel by providing a circuit that can be individually controlled, and the direction in which the RGB subpixels are arranged in parallel and the direction in which the plurality of LV subpixels are arranged in parallel are orthogonal to each other. And a third step of bonding the front side LCD panel manufactured in the first step and the rear side LCD panel manufactured in the second step.

  According to the present invention, an image display device using two LCD panels is realized by making the pixel configuration of the LV panel a sub-pixel structure similar to the RGB panel and making the sub-pixel structures of both panels orthogonal. doing. As a result, it is possible to obtain an image display apparatus and a method for manufacturing the image display apparatus that can improve contrast ratio and improve gradation expression capability using two LCD panels.

It is the figure which showed the pixel structure of the RGB panel in the conventional liquid crystal display device, and the pixel structure of the LV panel. FIG. 3 is a diagram illustrating a pixel structure of an RGB panel and a pixel structure of an LV panel in the liquid crystal display device according to the first embodiment. In the liquid crystal display device which concerns on Embodiment 1 of this invention, it is the figure which showed the gradation characteristic regarding each of the subpixels W1-W3 of an LV panel. It is a figure which shows the characteristic of the synthetic | combination transmittance | permeability of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a signal processing block diagram of the image display apparatus in Embodiment 1 of this invention. It is the figure which showed the internal structure of the edge detection circuit in Embodiment 1 of this invention. It is the figure which showed the internal structure of the subpixel controller in Embodiment 1 of this invention. It is the figure which showed the enlarged image of the 1st part by the simulation result of the image display apparatus in Embodiment 1 of this invention. It is the figure which showed the enlarged image of the 2nd part by the simulation result of the image display apparatus in Embodiment 1 of this invention. It is a signal processing block diagram of the image display apparatus in Embodiment 2 of this invention. It is the figure which showed the internal structure of the edge detection circuit in Embodiment 2 of this invention. It is the figure which showed the internal structure of the subpixel controller in Embodiment 2 of this invention. It is the figure which showed the enlarged image of the 1st part by the simulation result of the image display apparatus in Embodiment 2 of this invention. It is the figure which showed the enlarged image of the 2nd part by the simulation result of the image display apparatus in Embodiment 2 of this invention. It is a figure for demonstrating the problem in the conventional image display apparatus using two LCD panels. It is the figure which showed the gradation characteristic of the RGB panel and LV panel in the conventional image display apparatus using two LCD panels. It is the figure which showed the synthetic | combination transmittance | permeability in the conventional image display apparatus using two LCD panels. It is the figure which showed the correlation of the pixel value of both panels in the conventional image display apparatus using two LCD panels.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an image display device and an image display device manufacturing method according to the invention will be described with reference to the drawings.

  The present invention is an image that improves the contrast ratio due to the effect of multiplying the light transmittance of the rear and front panels by attaching two LCD panels back and forth and illuminating the backlight from the back side. In the manufacturing method of the display device and the image display device, an LV panel having a sub-pixel structure is adopted, and the contrast ratio is improved by providing a configuration in which the sub-pixel structure of the RGB panel and the sub-pixel structure of the LV panel are orthogonal to each other. At the same time, the technical feature is to improve the gradation expression ability.

Embodiment 1 FIG.
First, an outline of the features of the present invention will be described.
FIG. 1 is a diagram illustrating a pixel structure of an RGB panel and a pixel structure of an LV panel in a conventional liquid crystal display device. On the other hand, FIG. 2 is a diagram showing the pixel structure of the RGB panel and the pixel structure of the LV panel in the liquid crystal display device according to the first embodiment.

  Conventionally, as shown in FIG. 1, the RGB panel has R, G, and B sub-pixel structures, whereas the LV panel is configured as one pixel. On the other hand, in the first embodiment, as shown in FIG. 2, the RGB panel has R, G, and B subpixel structures, whereas the LV panel has subpixels of the RGB panel. It has a sub-pixel structure that is orthogonal to the structure.

  The RGB panel performs basic color expression by changing the liquid crystal transmittance of the corresponding RGB sub-pixel according to the gradation value of each color. On the other hand, each of the sub-pixels W1 to W3 of the LV panel operates as a light valve that adds fine gradation expression by changing the transmittance of each sub-pixel according to the RGB gradation values. An 8-bit driver is connected to each subpixel of the LV panel.

  FIG. 3 is a diagram showing gradation characteristics regarding each of the sub-pixels W1 to W3 of the LV panel in the liquid crystal display device according to the first embodiment of the present invention. As shown in FIG. 3, for each of the sub-pixels W1, W2, and W3, the transmittance corresponding to the range of lighting gradation values and the gradation characteristics is set and controlled so as to be sequentially turned on. Compared to the case of the single pixel structure W as shown in FIG. 1, it is possible to provide three times the gradation expression capability (that is, the gradation level of 0 to 765).

  FIG. 4 is a diagram showing the composite transmittance characteristics of the liquid crystal display device according to Embodiment 1 of the present invention. As a result of controlling the lighting of the sub-pixels W1 to W3 as shown in FIG. 3, the three-fold gradation expression capability is obtained and, as in the case where the pixel W is configured as one pixel W, linear synthetic transmission is performed. Rate can be realized.

  Next, the overall configuration of the liquid crystal display device according to the first embodiment will be described, and a specific control method of the LV panel having a subpixel structure will be described with reference to the drawings. FIG. 5 is a signal processing block diagram of the image display apparatus according to Embodiment 1 of the present invention. The image display apparatus shown in FIG. 5 includes an RGB controller 10 and an LV controller 20.

  Here, the RGB controller 10 includes a bit expansion circuit 11, a delay circuit 12, a gradation conversion circuit 13, and a color balance controller 14, and an output from the color balance controller 14 is supplied to the RGB panel 1.

  The LV controller 20 includes a gray converter 21, a gradation conversion circuit 22 (1), an edge detection circuit 23 (1), and a subpixel controller 24 (1). Are supplied to the LV panel 2.

  Next, an outline of signal processing by the RGB controller 10 and the LV controller 20 will be described.

  As an example, the bit extension circuit 11 performs a bit extension process to 12 bits on the input 8-bit RGB image. In this bit extension process, the bit length is extended with high accuracy in advance so as not to lower the bit precision in subsequent processing. The bit extension circuit 11 transmits the RGB image after bit extension to each of the delay circuit 12 and the gray converter 21.

  In the configuration shown in FIG. 1, the bit extension circuit 11 is provided in the RGB controller 10. However, the bit extension circuit 11 is provided outside the RGB controller 10, and the RGB image after bit extension is connected to the RGB controller 10. It is also possible to supply to the LV controller 20.

  Further, in order to prevent the bit accuracy from being lowered in the subsequent processing, it is possible to employ a configuration in which the bit expansion circuit 11 is eliminated when processing for extending the bit length with high accuracy in advance is not necessary.

  The delay circuit 12 in the RGB controller 10 receives the RGB image after bit extension from the bit extension circuit 11 and applies an appropriate delay to the received RGB image after bit extension. This “appropriate delay” is to compensate for the delay of processing by the gray converter 21, the edge detection circuit 23 (1), and the sub-pixel controller 24 (1) in the LV controller 20.

  Next, the gradation conversion circuit 13 in the RGB controller 10 performs gradation conversion using an LUT (look-up table) for each delayed color.

  On the other hand, the gray converter 21 in the LV controller 20 receives the RGB image after bit extension from the bit extension circuit 11 and, for the received RGB image after bit extension, three values of RGB for each pixel. Is converted into a gray image with the maximum value in the image as a representative value.

  Usually, in the conversion to gray scale, luminance is often obtained by performing color matrix conversion using a multiplier and an adder. The gray converter 21 according to the first embodiment detects the maximum value of the R, G, and B values in each pixel so that the color balance controller 14 in the RGB controller 10 can easily perform RGB color balance correction. However, by outputting this as a representative value, the hardware is also simplified.

  Of course, it is needless to say that the color balance correction process can be executed without any problem even when the normal matrix conversion is adopted.

  Next, the gradation conversion circuit 22 (1) in the LV controller 20 performs gradation conversion on the gray image using the LUT. The gradation conversion circuit 22 (1) according to the first embodiment outputs 8-bit pixel values related to the three subpixels W1, W2, and W3 so as to have the gradation characteristics as described in FIG. Will be.

  Next, the edge detection circuit 23 (1) in the LV controller 20 performs edge detection processing on the gray image and outputs 2-bit signals S0 and S1. FIG. 6 is a diagram showing an internal configuration of the edge detection circuit 23 (1) in the first embodiment of the present invention. The edge detection circuit 23 (1) according to the first embodiment includes a line memory 231, a difference unit 232, an absolute value calculator 233, and two comparators 234 and 235.

  The differentiator 232 reads the image data of the target line from the terminal A for the gray image output from the gray converter 21. Further, the differentiator 232 reads the image data of the line one line higher than the target line from the terminal B via the line memory 231 for the gray image output from the gray converter 21. Then, the differentiator 232 calculates and outputs a value obtained by subtracting the data of the terminal B from the data of the terminal A as a difference value.

  The comparator 234 compares the difference value calculated by the differentiator 232 with 0 and outputs a signal S0. Specifically, when the difference value is positive, the comparator 234 determines that the pixel has changed from light to dark, and outputs S0 = 0. On the other hand, when the difference value is negative, the comparator 234 determines that the pixel has changed from dark to bright, and outputs S0 = 1. When the difference value is zero, it can be determined in advance to output either one of 0 or 1.

  The comparator 235 compares the absolute value of the difference value calculated by the differentiator 232 with a predetermined threshold value TH and outputs a signal S1. Specifically, when the absolute value is less than the threshold value TH, the comparator 235 determines that the edge is not an edge, and outputs S1 = 0. On the other hand, when the absolute value is equal to or greater than the threshold value TH, the comparator 235 determines that the edge is an edge and outputs S1 = 1.

  In this way, the edge detection circuit 23 (1) outputs the positive / negative information of the interline difference as the signal S0 based on the gray image output from the gray converter 21, and the presence / absence information of the edge as the signal S1. Can be output.

  Next, returning to the configuration of FIG. 5, the sub-pixel controller 24 (1) determines the 8-bit pixel values regarding the three sub-pixels W1, W2, and W3 output from the gradation conversion circuit 22 (1) and the edge. Based on the signals S0 and S1 output from the detection circuit 23 (1), three 8-bit signals W1 ′, W2 ′ and W3 ′ to be supplied to the LV panel 2 and the color balance controller 14 are generated.

  FIG. 7 is a diagram showing an internal configuration of the sub-pixel controller 24 (1) in the first embodiment of the present invention. The sub-pixel controller 24 (1) according to the first embodiment includes an average calculator 241 and three selectors 242-244.

  The average calculator 241 calculates an average value of 8-bit pixel values regarding the three sub-pixels W1, W2, and W3 output from the gradation conversion circuit 22 (1). This average value is input to terminals A and B of the three selectors 242 to 244, respectively.

  The selector 242 reads an 8-bit pixel value related to the sub-pixel W1 from the terminal C, and reads an 8-bit pixel value related to the sub-pixel W3 from the terminal D. The selector 243 reads the 8-bit pixel value related to the sub-pixel W2 from the terminal C and the end D. The selector 244 reads an 8-bit pixel value related to the sub-pixel W3 from the terminal C, and reads an 8-bit pixel value related to the sub-pixel W1 from the terminal D.

  Each of the selectors 242 to 244 selects one of the terminals A to D as W1 ′ to W3 ′ according to the combination of the signals S0 and S1 according to the table shown in the lower right of FIG. Output.

  In this way, the sub-pixel controller 24 (1) selects and outputs one of W1 to W3 or the average value (W1 + W2 + W3) / 3 according to the state of the edge represented by the signals S0 and S1. By doing so, it is possible to realize a three-fold gradation expression capability as shown in FIG.

  Next, improvement in the gradation expression capability (that is, vertical resolution) in the vertical direction by the image display apparatus according to the first embodiment will be described using simulation results. FIG. 8 is a diagram showing an enlarged image of the first portion based on the simulation result of the image display device according to Embodiment 1 of the present invention. Similarly, FIG. 9 is a diagram showing an enlarged image of the second portion based on the simulation result of the image display device according to Embodiment 1 of the present invention.

In FIG. 8, (a) to (d) show the following contents.
FIG. 8A shows an original input image, an image displayed on the RGB panel, an image displayed on the LV panel, and a composite image on the entire screen.
FIG. 8B is an enlarged view of the image displayed on the RGB panel with respect to the first part.
FIG. 8C: First, with respect to the portion, an image displayed on the LV panel that is not sub-pixelated, and an enlarged composite image obtained as a result.
FIG. 8D: First, with respect to the portion, an image displayed on the sub-pixelized LV panel and a resultant composite image are enlarged.

Similarly, in FIG. 9, (a) to (d) show the following contents.
FIG. 9A: An original input image, an image displayed on the RGB panel, an image displayed on the LV panel, and a composite image are shown on the entire screen.
FIG. 9B is an enlarged view of the image displayed on the RGB panel for the second part.
FIG. 9 (c): Secondly, with respect to the portion, an image displayed on the LV panel which is not sub-pixelated, and an enlarged composite image obtained as a result.
FIG. 9D: Second, regarding the portion, an image displayed on the sub-pixelized LV panel and a resultant composite image are enlarged.

  8 and 9, the vertical resolution of the resultant composite image is obtained by subdividing the gray level in one pixel by the sub-pixels of the LV panel with respect to the edge portion of the image that changes from dark to bright. Was confirmed to be improved.

  As described above, according to the first embodiment, the pixels of the LV panel have a subpixel structure, and the subpixel structures of the RGB panel and the LV panel are orthogonal to each other. As a result, it is possible to realize a higher gradation expression capability than the gradation realized by the conventional 8-bit liquid crystal driver.

  Also, in the sub-pixel structure of two liquid crystal panels, the vertical resolution is improved by controlling the lighting of the sub-pixels in the LV panel according to the position of the edge of the input image, and the video is sharper. Can be

Embodiment 2. FIG.
The liquid crystal display device according to the second embodiment is the same as the first embodiment in terms of the subpixel structure of the LV panel 2, but the specific control content by the LV controller 20 is the same as in the first embodiment. Is different. Therefore, the liquid crystal display device according to the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

  FIG. 10 is a signal processing block diagram of the image display apparatus according to Embodiment 2 of the present invention. The image display apparatus shown in FIG. 10 includes an RGB controller 10 and an LV controller 20.

  Here, the RGB controller 10 includes a bit expansion circuit 11, a delay circuit 12, a gradation conversion circuit 13, and a color balance controller 14, and an output from the color balance controller 14 is supplied to the RGB panel 1. The configuration and function of the RGB controller 10 are the same as those in the first embodiment, and a description thereof will be omitted.

  On the other hand, the LV controller 20 includes a gray converter 21, a gradation conversion circuit 22 (2), an edge detection circuit 23 (2), and a subpixel controller 24 (2). Are supplied to the LV panel 2. Compared to the first embodiment, the gray converter 21 has the same function, but the gradation conversion circuit 22 (2), the edge detection circuit 23 (2), and the subpixel controller 24 (2) are more specific. The signal processing is different from that of the first embodiment, and the difference will be mainly described below.

  The gradation conversion circuit 22 (2) in the LV controller 20 performs gradation conversion on the gray image using the LUT. The gradation conversion circuit 22 (2) in the second embodiment outputs a common 8-bit pixel value for the three subpixels W1, W2, and W3.

  Next, the edge detection circuit 23 (2) in the LV controller 20 performs edge detection processing on the gray image and outputs 2-bit signals SL and SU. FIG. 11 is a diagram showing an internal configuration of the edge detection circuit 23 (2) in the second embodiment of the present invention. The edge detection circuit 23 (2) in the second embodiment includes two line memories 236a and 236b, two difference units 237a and 237b, two absolute value calculators 238a and 238b, and two comparators 239a and 239b. It is prepared for.

  The differentiator 237a reads, from the terminal A, image data that is one line lower than the target line for the gray image output from the gray converter 21. Further, the differentiator 237a reads the image data of the target line from the terminal B via the line memory 236a for the gray image output from the gray converter 21. Then, the differentiator 237a calculates and outputs a value obtained by subtracting the data of the terminal B from the data of the terminal A as a difference value.

  The absolute value calculator 238a calculates the absolute value of the difference value calculated by the difference unit 237a. Then, the comparator 239a compares the absolute value of the difference value calculated by the absolute value calculator 238a with a predetermined threshold TH and outputs a signal SL. Specifically, when the absolute value is less than the threshold value TH, the comparator 239a determines that no edge exists from the target line toward the lower line, and outputs SL = 0. On the other hand, when the absolute value is greater than or equal to the threshold value TH, the comparator 239a determines that an edge exists from the target line toward the lower line, and outputs SL = 1.

  Similarly, the differentiator 237b reads the image data of the target line output from the line memory 236a from the terminal A. Further, the differentiator 237b reads the image data of the line immediately above the image data of the target line output from the line memory 236a from the terminal B via the line memory 236b. Then, the differentiator 237b calculates and outputs a value obtained by subtracting the data of the terminal B from the data of the terminal A as a difference value.

  The absolute value calculator 238b calculates the absolute value of the difference value calculated by the difference unit 237b. Then, the comparator 239b compares the absolute value of the difference value calculated by the absolute value calculator 238b with a predetermined threshold value TH and outputs a signal SU. Specifically, when the absolute value is less than the threshold value TH, the comparator 239b determines that no edge exists from the line above the target line toward the target line, and outputs SU = 0. On the other hand, when the absolute value is greater than or equal to the threshold value TH, the comparator 239b determines that an edge exists from the line above the target line toward the target line, and outputs SU = 1.

  In this way, the edge detection circuit 23 (2) outputs, as the signal SL, information on the presence / absence of an edge from the target line to the lower line based on the gray image output from the gray converter 21. In addition, information on the presence or absence of an edge from the upper line to the target line can be output as a signal SU.

  Next, returning to the configuration of FIG. 10, the sub-pixel controller 24 (2) sets the 8-bit pixel value common to the three sub-pixels W 1, W 2, and W 3 output from the gradation conversion circuit 22 (2). Based on the signals SU and SL output from the edge detection circuit 23 (2), three 8-bit signals W1, W2 and W3 to be supplied to the LV panel 2 and the color balance controller 14 are generated.

  FIG. 12 is a diagram showing an internal configuration of the subpixel controller 24 (2) in the second embodiment of the present invention. The sub-pixel controller 24 (2) in the second embodiment includes two line memories 245a and 245b, two weighted average calculators 246a and 246b, and two selectors 247a and 247b.

  The sub-pixel controller 24 (2) sequentially reads the 8-bit pixel values output from the gradation conversion circuit 22 (2). Further, the line memory 245a receives the image data of the line WL below the target line and outputs the pixel data of the target line WC. Further, the line memory 245b receives the image data of the target line WC and outputs pixel data of the line WU above the target line.

  The weighted average calculator 246a calculates a weighted average value of (WL + 2 × WC) / 3 from WL and WC. On the other hand, the weighted average calculator 246b calculates a weighted average value of (WU + 2 × WC) / 3 from WC and WU.

  The selector 247a reads the pixel value of the target line WC from the terminal A, and reads the value calculated by the weighted average calculator 246a from the terminal B. On the other hand, the selector 247b reads the pixel value of the target line WC from the terminal A, and reads the value calculated by the weighted average calculator 246b from the terminal B.

  Then, each selector 247a, 247b selects either terminal A or terminal B according to the signals SL, SU according to the table shown in the lower right of FIG. 12, and outputs them as W1 to W3.

  In this way, the sub-pixel controller 24 (2) selectively outputs W1 to W3 according to the presence / absence of an edge between the target line and the upper and lower lines expressed by the signals SL and SU. As shown in FIG. 3, it is possible to realize a three-fold gradation expression capability.

  Next, improvement in the vertical gradation expression capability (that is, vertical resolution) by the image display apparatus according to the second embodiment will be described using simulation results. FIG. 13 is a diagram showing an enlarged image of the first portion based on the simulation result of the image display device according to the second embodiment of the present invention. Similarly, FIG. 14 is a diagram showing an enlarged image of the second portion based on the simulation result of the image display device in the second embodiment of the present invention.

In FIG. 13, (a) to (d) show the following contents.
FIG. 13A shows an original input image, an image displayed on the RGB panel, an image displayed on the LV panel, and a composite image on the entire screen.
FIG. 13B is an enlarged view of the image displayed on the RGB panel for the first part.
FIG. 13 (c): First, regarding the portion, an image displayed on the LV panel that is not sub-pixelated and the resultant composite image are enlarged.
FIG. 13 (d): First, regarding the portion, an image displayed on the sub-pixelized LV panel and a resultant synthesized image are enlarged.

Similarly, in FIG. 14, (a) to (d) show the following contents.
FIG. 14A shows an original input image, an image displayed on the RGB panel, an image displayed on the LV panel, and a composite image on the entire screen.
FIG. 14B is an enlarged view of the image displayed on the RGB panel for the second part.
FIG. 14C: Second, regarding the portion, an image displayed on the LV panel that is not sub-pixelated and the resultant composite image are enlarged.
FIG. 14 (d): Secondly, with respect to the portion, an image displayed on the sub-pixelized LV panel and a resultant composite image are enlarged.

  13 and 14, the vertical resolution of the resultant composite image is improved by subdividing the gray level in one pixel by the sub-pixel of the LV panel with respect to the edge portion of the image. Was confirmed. Compared with the simulation result according to the first embodiment, the degree of edge enhancement is relaxed, but the vertical resolution is similarly improved.

  As described above, according to the second embodiment, the pixels of the LV panel have a subpixel structure, and the subpixel structures of the RGB panel and the LV panel are orthogonal to each other. As a result, it is possible to realize a higher gradation expression capability than the gradation realized by the conventional 8-bit liquid crystal driver.

  Also, in the sub-pixel structure of two liquid crystal panels, the vertical resolution is improved by controlling the lighting of the sub-pixels in the LV panel according to the position of the edge of the input image, and the video is sharper. Can be

  In the first and second embodiments described above, the case where one pixel on the LV panel side is configured by three subpixels has been described. However, it is also possible to configure the pixel by four or more subpixels, and the number of rust pixels As the value increases, higher gradation expression becomes possible.

  1 RGB panel, 2 LV panel, 10 RGB controller, 11 bit extension circuit, 12 delay circuit, 13 gradation conversion circuit, 14 color balance controller, 20 LV controller, 21 gray converter, 22 (1), 22 (2) floor Key conversion circuit, 23 (1), 23 (2) edge detection circuit, 231 line memory, 232 differencer, 233 absolute value calculator, 234, 235 comparator, 236a, 236b line memory, 237a, 237b differencer, 238a 238b Absolute value calculator, 239a, 239b Comparator, 24 (1), 24 (2) Subpixel controller, 241 Average calculator, 242, 243, 244 Selector, 245a, 245b Line memory, 246a, 246b Weighted average Calculators, 247a, 247b selectors.

Claims (4)

The image display device is configured by stacking two front side LCD panels and two rear side LCD panels, and performs image display by transmitting backlight light in the order of the rear side LCD panel and the front side LCD panel. And
Each pixel of the front side LCD panel is composed of RGB sub-pixels arranged in parallel,
Each pixel of the rear side LCD panel is composed of a plurality of LV subpixels arranged in a direction orthogonal to the RGB subpixels,
LV that individually controls the range of gradation values and gradation characteristics supplied to the plurality of LV subpixels according to the gray value of one gray image signal generated based on the input RGB image signal An image display device comprising a controller. When the longitudinal direction of the plurality of LV subpixels arranged in parallel is a horizontal direction, the LV controller is configured to change the plurality of LV controllers according to a luminance change state in a vertical direction of an edge extending in the horizontal direction. The image display device according to claim 1, wherein the transmittance of each subpixel is individually controlled. The plurality of LV sub-pixels is composed of N that is an integer of 3 or more,
The LV controller individually controls the transmittance, so that the gradation expression when the pixels of the rear LCD panel are not sub-pixels is set to 1 times, and the gradation expression is N times. The image display device according to claim 2. Manufacture of an image display device that is configured by stacking two front side LCD panels and two rear side LCD panels, and that displays images by transmitting backlight light in the order of the rear side LCD panel and the front side LCD panel. A method,
Each pixel of the front side LCD panel is composed of RGB subpixels arranged in parallel, and the liquid crystal transmittance of the corresponding RGB subpixel is individually controlled according to the gradation value of each RGB color A first step of manufacturing the front side LCD panel so as to include a circuit capable of:
Each pixel of the rear LCD panel is composed of a plurality of LV subpixels arranged in a direction orthogonal to the RGB subpixels, and the plurality of pixels corresponding to the gradation values of the respective RGB colors A second step of manufacturing the rear LCD panel by providing a circuit capable of individually controlling the liquid crystal transmittance of the LV subpixel;
The front-side LCD panel manufactured in the first step so that the direction in which the RGB sub-pixels are arranged in parallel and the direction in which the plurality of LV sub-pixels are arranged in parallel are orthogonal to each other; And a third step of bonding the rear LCD panel manufactured in the step to the image display device.

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