KR102078995B1 - Image Display Device And Method Of Displaying Image - Google Patents

Abstract

The present invention improves the contrast ratio using two LCD panels while correcting the color balance, and in particular, improves the color reproducibility of the dark portions.
An image display device configured by superimposing two front side LCD panels and two rear side LCD panels, and having backlight light transmitted through the rear side LCD panel and the front side LCD panel in order to perform image display. ) And a second controller 34. The second controller 34 generates a gray image signal W1 with respect to the input RGB image signals R1, G1, and B1, and then, the gray image signal ( An output gray image signal W3 is generated from the signal W2 based on W1, and the output gray image signal W3 is supplied to the rear LCD panel, and the first controller 33 RGB after color balance correction by performing color balance correction processing on the input RGB image signals R1, G1, B1 using the gray image signal W1 or the signal W2 based on the gray image signal Generates image signals R2, G2, and B2 And a color balance controller 332, wherein the first controller 33 performs a first bit expansion process on the luminance values of the respective sub-pixels of the RGB image signals R2, G2, and B2 after the color balance correction. A first bit expansion circuit 333 which performs an operation to generate an RGB image signal after bit expansion, and outputs a signal based on the RGB image signal after bit expansion as the output RGB image signals R3, G3, and B3. An image display device for supplying a side LCD panel is provided.

Description

Image Display Device And Method Of Displaying Image

The present invention relates to an image display apparatus and an image display method for performing color balance correction with contrast ratio improvement.

In the conventional image display apparatus using one LCD panel, gray scale linear characteristics in the naked eye are realized by correcting by input by a panel driver a broken line gamma on the input image.

However, in practice, since the illumination of the backlight transmits the luminance by passing through the liquid crystal panel, a so-called black floating phenomenon occurs, in which the gradation characteristics of the black region are poor and the luminance is observed in a bright direction compared to the ideal luminance. do.

This phenomenon occurs because when the LCD panel displays a dark area, the backlight of the backlight is leaked because the LCD panel is not completely shielded from light. A contrast ratio of about 10,000: 1 in conventional CRTs and about 1,000,000: 1 in organic EL panels is realized. However, according to the present phenomenon, in the conventional image display apparatus using one LCD panel, the contrast ratio is only realized at about 1,500: 1.

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

Patent Document 1: Japanese Patent Application Laid-Open No. 5-88197 Patent Document 2: International Publication No. 2007/108183

However, the prior art has the following problems.

As described above, there is a problem that a contrast ratio of only 1,500: 1 can be realized in an image display device using one LCD panel. Moreover, in one LCD, it is a big problem that the image cannot be faithfully reproduced due to the deterioration of color reproducibility in a dark image and the deterioration of black quality.

On the other hand, as shown in Patent Literatures 1 and 2, an image display device using two LCD panels has an effect of increasing contrast and preventing black floating. However, there is no mention of improving color reproducibility.

FIG. 15 is a diagram for explaining a problem of the conventional image display apparatus 100 using two LCD panels. The rear LCD panel on the backlight 103 side is referred to as an LV panel 102 (Light Valve Panel), and the front LCD panel on the side closer to a human viewing an image is called an RGB panel 101.

As shown in Fig. 15, the RGB panel 101 is composed of R, G, and B subpixels. On the other hand, the LV panel 102 combines the R, G, and B subpixels into one pixel. That is, one pixel of the LV panel 102 is common to one pixel in which the subpixels of the RGB panel 101 are combined, and has a 1: 1 correspondence.

Therefore, the luminance adjustment is performed by combining the RGB of an image that has passed through one pixel of the LV panel 102 and then passed through each sub-pixel of the RGB panel 101. Accordingly, the following first and second problems occur.

First problem: Whitening of colors due to light leakage occurs in the dark areas.

For example, in the case of a pure color that shines any one of RGB, when R only shines and GB does not shine, there is a problem that R becomes white (like white) to the light fountain of GB.

Second problem: color balance is broken.

For example, in the case of mixed colors that make all of the RGB shine, the luminance value of the LV pixel suitable for each luminance value of the original RGB, that is, the LV value which is common to all subpixels, is not the LV value. Therefore, there is a problem that the color balance is broken and discolored because the RGB luminance value after transmission as the product of the transmittances of the LV panel and the RGB panel differs from the original RGB.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. An image display device and an image display capable of improving color reproducibility, in particular, by improving the contrast ratio and correcting the color balance using two LCD panels. It aims to get a way.

An image display device according to the present invention is configured by superimposing two front side LCD panels and a rear side LCD panel, and an image for performing image display by allowing backlight light to pass through the rear side LCD panel and the front side LCD panel. A display device, comprising: a first controller and a second controller, wherein the second controller generates a gray image signal with respect to an input RGB image signal, and then generates an output gray image signal from the signal based on the gray image signal. And supply the output gray image signal to the rear LCD panel, and wherein the first controller uses the gray image signal or a signal based on the gray image signal to color balance the input RGB image signal. Color balance controller for generating RGB image signals after color balance correction by performing correction processing And the first controller includes a first bit expansion circuit for generating a RGB image signal after bit expansion by performing a first bit expansion process on a luminance value of each sub-pixel of the RGB image signal after the color balance correction. Then, a signal based on the RGB image signal after the bit expansion is supplied to the front side LCD panel as an output RGB image signal.

In addition, the image display method according to the present invention is constituted by superimposing two front side LCD panels and a rear side LCD panel, and performs image display by allowing backlight light to pass through the rear side LCD panel and the front side LCD panel. An image display method executed by an image display apparatus, comprising: generating a gray image signal with respect to an input RGB image signal, and then generating an output gray image signal from a signal based on the gray image signal, By using a signal based on the gray image signal, color balance correction processing is performed on the input RGB image signal to generate an RGB image signal after color balance correction, and each sub-pixel of the RGB image signal after color balance correction. RGB image signal after bit expansion by performing first bit extension processing on a luminance value of Generated, wherein the bits supplied to the signal based on the RGB image signal after the extension output as RGB image signals to the LCD panel and the front side, the supply for the output gray image signal to the LCD panel back side.

According to the present invention, an image display apparatus and an image display method capable of improving color reproducibility of dark portions can be obtained by improving contrast ratio while correcting the contrast ratio using two LCD panels.

1 is a signal processing block diagram of the image display device of Embodiment 1 of the present invention.
Fig. 2 is a more detailed signal processing block diagram by the RGB controller and the LV controller included in the image display device of the first embodiment.
3 is a detailed block diagram of the edge hold circuit of the first embodiment.
Fig. 4 is a flowchart of local edge hold processing by the edge hold circuit of the first embodiment.
Fig. 5 is a diagram showing waveforms of the results of the local edge hold processing by the edge hold circuit according to the first embodiment.
6 is an explanatory diagram of a color balance controller according to the first embodiment.
7 is an explanatory diagram of a correction coefficient of the color balance controller of the first embodiment.
8 is an explanatory diagram of bit expansion processing by the bit expansion circuit according to the first embodiment.
Fig. 9 is a diagram showing the gray scale conversion characteristics by the LUT (R) of the first embodiment.
Fig. 10 is a diagram showing the gray scale conversion characteristics by the LUT (W) of the first embodiment.
FIG. 11 is an explanatory diagram of improving color reproducibility of a dark portion by the LUT of the first embodiment. FIG.
12 is a schematic cross-sectional view of a display module using two LCD panels of the first embodiment.
13 is a signal processing block diagram of an image display device of a modification of the present invention.
14 is an explanatory diagram showing experimental results of the first embodiment and a modification.
FIG. 15 is a diagram for explaining a problem of a conventional image display apparatus using two LCD panels. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of the image display apparatus and image display method of this invention is described with drawing.

The image display device of Embodiment 1 is constituted by superimposing two front side LCD panels and a rear side LCD panel, and an image display device which performs image display by allowing backlight light to pass through the rear side LCD panel and the front side LCD panel. And a first controller and a second controller, wherein the second controller generates a gray image signal with respect to the input RGB image signal, and then generates an output gray image signal from a signal based on the gray image signal and output gray. RGB after the color balance correction by supplying an image signal to the rear LCD panel, and performing a color balance correction process on the input RGB image signal using the gray image signal or a signal based on the gray image signal. A color balance controller for generating an image signal, the first controller is RGB after color balance correction A first bit extension circuit for performing a first bit expansion process on the luminance value of each sub-pixel of the image signal to generate an RGB image signal after bit expansion, and outputting a signal based on the RGB image signal after bit expansion It is supplied to the front LCD panel as an RGB image signal.

1 is a signal processing block diagram of the image display device of the first embodiment. The image display device 10 of the first embodiment shown in FIG. 1 includes an image display device main body 20 and an LCD module 30.

The image display device main body 20 is configured to include an image processing engine 21. Meanwhile, the LCD module 30 includes an I / F (interface) 31, an RGB controller (first controller, 33), an LV (light valve) controller (second controller, 34), an RGB panel (front LCD panel, 35). And an LV panel (rear-side LCD panel 36).

The image processing engine 21 in the image display device main body 20 generates an RGB image and transmits it to the LCD module 30. The I / F 31 in the LCD module 30 receives the RGB image generated by the image processing engine 21, and inputs the luminance value of each of the subpixels R, G, and B of each pixel into an input RGB image signal. The data is transmitted to the RGB controller 33 and the LV controller 34 as an example.

FIG. 2 is a more detailed signal processing block diagram by the RGB controller 33 and the LV controller 34 included in the image display device of the first embodiment.

As shown in Fig. 2, the RGB controller 33 includes a delay circuit 331, a color balance controller 332, an RGB bit extension circuit (first bit extension circuit 333), and three LUTs (Look Up Table, 3341). And an RGB gray conversion circuit 334 having 3342, 3343.

Meanwhile, the LV controller 34 includes a gray converter 341, a horizontal edge hold circuit (edge hold circuit 342), a vertical edge hold circuit (edge hold circuit 343), and an LPF (low pass filter) circuit 344. And an LV gradation conversion circuit (gray gradation conversion circuit 346) having an LV bit extension circuit (second bit extension circuit 345) and one LUT 3541.

Subsequently, each component of the RGB controller 33 and the LV controller 34 will be described according to the signal flow order.

The gray converter 341 in the LV controller 34 generates a gray image signal W1 which is a gray scale image signal from the input RGB image signals R1, G1, B1. That is, the gray converter 341 receives the input RGB image signals R1, G1, and B1 from the I / F 31 shown in FIG. 1, and receives the input RGB image signals R1, G1, and B1. For each pixel, the luminance value of each RGB sub-pixel, that is, the maximum value among the input RGB image signals R1, G1, and B1 is selected, and this is converted into a gray image by making it the representative value W1.

In general, conversion to gray scale is often performed to obtain luminance by performing color matrix conversion using a multiplier and an adder. The gray converter 341 of the first embodiment uses the luminance values of R, G, and B in each pixel so that color balance correction of RGB can be easily performed by the color balance controller 332 in the RGB controller 33. Hardware is also simplified by detecting the maximum value and outputting it as a representative value.

It goes without saying that the color balance correction process can be executed without any problem even when the usual matrix conversion is adopted.

The gray converter 341 transmits the luminance value to the horizontal edge hold circuit 342 as the gray image signal W1 for each pixel of the generated gray image.

The LV controller 34 is an edge hold circuit that applies a local edge hold process to the gray image signal W1, and generates a gray image signal after the edge hold process, and applies a local edge hold process in the horizontal direction. The horizontal edge hold circuit 342 and the vertical edge hold circuit 343 apply local edge hold processing in the vertical direction. The gray image signal W1 transmitted by the gray converter 341 is received by the horizontal edge hold circuit 342.

The horizontal edge hold circuit 342 performs local enlargement processing of the edge area of the image. For two LCD panels, there is no problem when viewed from the front, but when viewed from the diagonal in the horizontal direction, the front and rear display image positions are shifted according to the angle, resulting in a double image and color shift. There is a visible problem. In order to solve this problem, the horizontal edge hold circuit 342 serves to correct the viewing angle in the horizontal direction with respect to the LV image.

3 is a detailed block diagram of the horizontal edge hold circuit 342 of the first embodiment. 4 is a flow chart related to the local edge hold processing by the horizontal edge hold circuit 342 of the first embodiment.

In the example of FIG. 3, FIG. 4, the local edge hold process of 5 horizontal taps is shown. The luminance values of the pixels of the LV image after the gray level conversion input in the horizontal line direction are sequentially stored in the registers X1 to X5.

When the horizontal edge hold circuit 342 detects that the luminance value of the X3 pixel which is the center is the rising edge, that is, the luminance value of the X3 pixel is larger than the luminance value of the left pixel of X3, the horizontal edge hold circuit 342 A process of replacing the luminance value with the luminance value of the X3 pixel is performed. Further, the horizontal edge hold circuit 342 detects the right pixel of X3 when the luminance value of the X3 pixel which is the center is a falling edge, that is, when the luminance value of the X3 pixel is larger than the luminance value of the right pixel of X3. The process of replacing the luminance value of with the luminance value of the X3 pixel is performed.

However, the processing is limited to the case where X3 is greater than or equal to threshold 3 and the size of the edge ((X3-X2) or (X3-X4)) is greater than or equal to threshold 4. That is, the horizontal edge hold circuit 342 performs local edge hold processing when the luminance value is higher than a certain level.

The registers Y1 to Y5 and selections 1 to 5 shown at the bottom of FIG. 3 perform the above-described replacement operation, and further replace with X3 if the pixel once replaced in the entire operation period is smaller than X3. Is doing.

The control signal for the above substitution is S1 to S5 of FIG. 3, and the horizontal edge hold circuit 342 does not perform the substitution when the control signal is 0, but performs the substitution when the control signal is 1.

FIG. 5 is a view showing waveforms of the operation results of the local edge hold processing by the horizontal edge hold circuit 342 according to the first embodiment. FIG. 5A is an input waveform for the horizontal edge hold circuit 342, and FIG. 5B is an output waveform for the input waveform of FIG. Each white circle corresponds to each pixel luminance value of the output image from the gray converter 341 in FIG. On the other hand, the black circle of FIG. 5B corresponds to the luminance value of the edge-holded pixel.

As shown in Fig. 5, the local edge hold processing is performed, whereby the previous or next pixel is replaced by the value of the edge pixel. By performing the correction to improve the luminance of the adjacent pixels in this manner, it is possible to prevent the image from darkening when viewed from the diagonal in the horizontal direction.

The horizontal edge hold circuit 342 transmits the gray image signal after the horizontal edge hold process to the vertical edge hold circuit 343 shown in FIG. 2.

The vertical edge hold circuit 343 receives the gray image signal after the horizontal edge hold process from the horizontal edge hold circuit 342 and corrects the viewing angle in the vertical direction. The vertical edge hold circuit 343 can be realized by the same configuration as described above with respect to the horizontal edge hold circuit 342. The vertical edge hold circuit 343 transmits the gray image signal after the edge hold process to the LPF circuit 344.

The LPF circuit 344 receives the gray image signal after the edge hold process, applies a low pass filter to the gray image signal after the edge hold process, and applies a low pass filter applied gray image signal (a signal based on the gray image signal, W2). In the image where the viewing angle is corrected by performing the edge hold process, the luminance value of each pixel is adjusted as described above, but the change between adjacent luminance values is slowed by performing the LPF process so that the luminance value after adjustment is naturally seen as the whole image. I'm making it.

The LPF circuit 344 transmits the low pass filter applied gray image signal W2 to the color balance controller 332 of the RGB controller 33 and the LV bit expansion circuit 345.

On the other hand, in the RGB controller 33, the delay circuit 331 in the RGB controller 33 receives the input RGB image signals R1, G1, B1 from the I / F 31. The delay circuit 331 appropriately delays the received input RGB image signals R1, G1, and B1. An appropriate delay is used to compensate for processing delays by the gray converter 341, the horizontal edge hold circuit 342, the vertical edge hold circuit 343 and the LPF circuit 344 in the LV controller 34. Synchronizing the input RGB image signals R1, G1, B1 transmitted to the color balance controller 332 via the delay circuit 331 and the gray image signal W2 with the low pass filter transmitted from the LV controller 34 It is for.

The color balance controller 332 in the RGB controller 33 is a corresponding low pass filter transmitted from the LV controller 34 for each pixel with respect to the input RGB image signals R1, G1, and B1 delayed by the delay circuit 331. Based on the applied gray image signal W2, color balance correction is performed by adjusting the color balance using a correction coefficient.

The color balance controller 332 calculates the luminance ratio by dividing each of the input RGB image signals R1, G1, B1 by the low pass filter applied gray image signal W2, as shown in Equations (1) to (3) below. The RGB signals R2 ', G2', and B2 'are generated by multiplying each of the input RGB image signals R1, G1, and B1 by the luminance ratio.

R2 '= R1 × (R1 / W2) (1)

G2 '= G1 × (G1 / W2) (2)

B2 '= B1 × (B1 / W2) (3)

By displaying the RGB signals R2 ', G2', and B2 'with the RGB panel 35, it is possible to solve the problem that the above-described color balance is broken. However, the color balance controller 332 actually uses the RGB signals generated according to the following formulas (4) to (6), which are further adjusted with respect to the RGB signals R2 ', G2', and B2 '. It outputs to the rear stage as RGB image signal R2, G2, B2 after balance correction. Here, the problem solving that a color balance will fall first is demonstrated.

6 is an explanatory diagram of color balance adjustment by operation of the color balance controller 332. That is, it corresponds to the principle diagram of the cause and solution of a 2nd problem.

As shown in Fig. 6 (a), a case in which RGB displays pixels expressing mixed colors (R > G > B) other than zero will be described as an example. As described above, the gray converter 341 generates the gray image with respect to the input RGB image signals R1, G1, and B1 so as to be represented by the maximum value of each RGB subpixel luminance value of each pixel. Accordingly, the low pass filter applied gray image signal W2 having the luminance value W2 which is about the same as the subpixel R1 having the luminance value is generated.

When these input RGB image signals R1, G1, B1 and the low pass filter-applied gray image signal W2 are synthesized and transmitted, R1 after the combined transmission obtains a desired luminance, but G1 and B1 are G1 and B1. Since the low pass filter applied gray image signal W2 becomes larger than the luminance value of the gray image signal originally required for the expression, the color balance is broken.

The luminance values of the LV image which are originally required for the RGB image signal after the color balance correction to obtain the original RGB luminance will be luminance values of R1, G1, and B1, respectively. This is illustrated in FIG. 6 (b). That is, in order to obtain the original luminance of G and B, it is necessary to change the luminance value in the LV image for each color of RGB as shown in Fig. 6B. However, since one pixel of the LV panel 1 is the sum of three subpixels of the RGB panel, it is impossible to change each pixel of the LV image for each color of RGB. Therefore, the tone is adjusted on the RGB panel side, not on the LV panel side, to obtain the desired composite transmittance in all colors.

In other words, it is considered that the RGB panel side tone is adjusted so that the combined transmittances of the RGB panel and the LV panel before and after the adjustment are the same to derive the luminance value after the adjustment. To do this, R1 / W2, G1 / W2, and B1 / W2 are multiplied as luminance ratios for each of the input RGB image signals R1, G1, and B1, that is, R2 ', G2' in the above formulas (1) to (3). , B2 'can be derived. As a result, when R2 ', G2', and B2 'are displayed on the RGB panel 35 as shown in Fig. 6C, W2 is displayed on the LV panel 36, and color balance adjustment becomes possible.

Since the color balance controller 332 corrects and controls the color balance based on the same principle as described above, the color balance controller 332 can display the original color even in the mixed color portion, and the color reproducibility can be improved. Needless to say, this result is shown not only in dark areas but also in bright areas.

However, in the first embodiment as described above, however, not the RGB signals R2 ', G2', and B2 'obtained by the formulas (1) to (3), in reality, the RGB signals R2 and G2 that are further adjusted thereto are actually used. , B2 is output to the RGB bit extension circuit 333 at a later stage as an RGB image signal after color balance correction. This is difficult for the following reason.

In the above-described configuration, as described above, the viewing angle correction is performed by the horizontal and vertical edge hold circuits 342 and 343, and the edge, which is the portion with the large difference in luminance, is expanded in the dark direction, thereby widening the brightly displayed area. In the pixel corresponding to this widened edge portion, the low pass filter-applied gray image signal W2 is brightly adjusted, and based on this, the color balance is corrected by the color balance controller 332 and the RGB signals R2 'and G2' are adjusted. , B2 ') is generated. That is, since the RGB signals R2 ', G2', and B2 'are adjusted to be dark as opposed to the low pass filter-applied gray image signal W2 except for the subpixel whose luminance value is maximum, the RGB signals R2', G2 ' The RGB image displayed by ', B2') is corrected to be partially darkened.

When a human being viewed from the front, the RGB panel 35 and the LV panel 36 output the corresponding RGB signals R2 ', G2', B2 'and the low pass filter applied gray image signal W2. Since the light passing through these panels 35 and 36 is adjusted as described with reference to FIG. 6, an image having good color reproducibility is obtained. However, when viewed from the diagonal, the RGB signals (R2 ', G2', B2 ') are corrected to be partially dark, and the area that should be bright originally is partially darkened, so the double line is shown on the edge part. Side effects may occur.

In order to alleviate this side effect, in this Embodiment 1, instead of said Formula (1)-(3), the function F (RGB individual correction coefficient) which reduced the multiplication effect of a luminance ratio is predetermined, and this function F is input RGB. The RGB image signals R2, G2, after color balance correction, which are multiplied for each of the image signals R1, G1, B1 and output to the RGB bit expansion circuit 333 at the next stage as shown in the following equations (4) to (6). B2) is being generated.

R2 = R1 × F (R1, W2) (4)

G2 = G1 × F (G1, W2) (5)

B2 = B1 × F (B1, W2) (6)

In the first embodiment, the RGB individual correction coefficient, i.e., the function F, is multiplied by the adjustment function (1-TH) obtained by subtracting the predetermined value TH from 1 as shown in the following equations (7) to (9) for the luminance ratio. It is calculated by further adding the value TH.

F (R1, W2) = (R1 / W2) × (1-TH) + TH (7)

F (G1, W2) = (G1 / W2) × (1-TH) + TH (8)

F (B1, W2) = (B1 / W2) × (1-TH) + TH (9)

FIG. 7 is a graph showing the function F when the input is the luminance ratio in the formulas (7) to (9). As can be seen in FIG. 7, the function F 61 is the luminance ratio R1 / which has been multiplied with respect to the input RGB image signals R1, G1, B1 in equations (1) to (3) represented by 60 in FIG. Clipping is performed such that W2, G1 / W2, and B1 / W2) become a value equal to or greater than a predetermined value TH and equal to or less than one. In this case, when TH is 0, the luminance ratio itself is used as a function F without clipping the luminance ratio, and the RGB image signal after color balance correction is applied by applying Equations (1) to (3) as it is. This is the case when (R2, G2, B2) is generated.

As described above, in the first embodiment, the color balance controller 332 uses the low-pass filter-applied gray image signal based on the luminance value of each sub-pixel of the input RGB image signals R1, G1, and B1. By further multiplying a luminance function (R1 / W2, G1 / W2, B1 / W2) of each sub-pixel obtained by dividing by one signal, W2, the adjustment function (1-TH) having a range from 0 to 1 is obtained. RGB image signals R2, G2, B2 after color balance correction by calculating the RGB individual correction coefficients F and multiplying the RGB individual correction coefficients F by the luminance values of the respective subpixels of the input RGB image signals R1, G1, B1. ) Is being created. In this way, by suppressing the change range of the luminance ratio from equations (1) to (3), the luminance ratio is prevented from acting excessively, thereby improving color reproducibility and effectively suppressing side effects such as double lines.

The function F can be realized by a circuit of a relatively simple configuration.

The color balance controller 332 transmits the RGB image signals R2, G2, and B2 after the color balance correction generated as described above to the RGB bit extension circuit 333 shown in FIG.

The RGB bit extension circuit (first bit extension circuit 333) of the RGB controller 33 performs the first bit extension processing on the luminance values of the respective sub pixels of the RGB image signals R2, G2, and B2 after color balance correction. To generate the RGB image signal after bit extension. The RGB bit extension circuit 333 includes bit extension circuits 3331, 3332, and 3333 corresponding to each of the RGB image signals R2, G2, and B2 after color balance correction. Here, the bit extension circuit 3331 corresponding to the image signal R2 will be described. The bit extension circuits 3332 and 3333 corresponding to the image signals G2 and B2 are also configured in the same manner as the bit extension circuit 3331 corresponding to the image signal R2.

The bit extension circuit 3331 performs a bit extension process on 12 bits for the input 8-bit image of each RGB. In the bit extension process, the bit length is pre-expanded with high precision so as not to degrade the bit precision in the subsequent processing.

In the bit expansion circuit 3331 of the first embodiment, as shown in Fig. 8A, the 8-bit data 50, that is, the 8-bit image signal is extended to, for example, 12 bits, and the 12-bit data 52 is used. I assume that In the case of quantizing the original analog image signal with 8 bits, the change below the bit resolution has been rounded. However, since the image has a high correlation between adjacent pixels, it can be restored to some extent by introducing the following method.

Fig. 8B is an explanatory diagram of a pixel to be processed, that is, the pixel X5 of interest, and Fig. 8C is an example in which the bit extension processing procedure is expressed in a program format. The bit extension circuit 3331 is the pixel of interest for the eight pixels (X1 to X4, X6 to X9) adjacent to the pixel of interest X5 with respect to the variable dc initialized to zero as shown in FIG. When the luminance value of (X5) is smaller than the luminance value of each adjacent pixel, +1 is performed, and -1 operation is performed when the luminance value of the pixel X5 of interest is larger than the luminance value of each adjacent pixel.

Further, the bit expansion circuit 3331 adds the sum value, i.e., the value of dc divided by 8, to the pixel X5 of interest as the weight 51 below the decimal point, and performs 16 times rounding, thereby making the bit from 8 bits to 12 bits. Perform the extension.

In general, adjacent pixels in an image have a property that the luminance values are similar. For example, when all luminance values of neighboring pixels are large with respect to the luminance value of the pixel X5 of interest, the luminance value of each pixel is rounded to 8 bits. The waveform at the analog value, which is the original value before the conversion, has a continuous concave shape, and the analog value, which is the original value of the luminance value of the pixel X5 of interest, is estimated to be larger than the data rounded to 8 bits.

On the other hand, when all the luminance values of the surrounding pixels are small with respect to the luminance value of the pixel X5 of interest, the waveform at the analog value which is the original value before the luminance value of each pixel is rounded to 8 bits becomes a continuous convex shape. The analog value, which is the original value of the luminance value of the pixel X5 of interest, is estimated to be smaller than the data rounded to 8 bits. Accordingly, the bit expansion circuit 3331 performs the bit expansion processing as shown in FIG. 8 based on such a basis.

For the bit extension method, a method other than the method described herein may be introduced.

On the other hand, in the LV controller 34, the LV bit expansion circuit (second bit expansion circuit 345) shown in Fig. 2 is second to the low pass filter applied gray image signal (signal based on the gray image signal, W2). A bit extension process is performed to generate a gray image signal after bit extension. The LV bit expansion circuit 345 includes one bit expansion circuit 3651 having the same configuration as the bit expansion circuit 3331, thereby low pass in the same order as described with respect to the bit expansion circuit 3331. Bit-extend the filter applied gray image signal W2.

The RGB bit extension circuit 333 transmits the RGB image signal after the bit extension to the RGB gray level conversion circuit 334. The LV bit expansion circuit 345 also transmits the gray image signal after the bit expansion to the LV gray scale conversion circuit 346.

Next, the RGB grayscale conversion circuit 334 of the RGB controller 33 and the LV grayscale conversion circuit 346 of the LV controller 34 will be described. The RGB gradation conversion circuit 334 stores the first LUTs 3331, 3342, and 3343 that perform the first gradation conversion on the RGB image signal separately for the luminance values of the respective RGB subpixels, and after bit expansion By performing the first gradation conversion by applying the first LUTs 3331, 3342, and 3343 to the RGB image signals, the output RGB image signals (signals based on the RGB image signals after bit expansion, R3, G3, B3) are obtained. Create In addition, the LV gray scale conversion circuit 346 stores a second LUT 3401 which performs second gray scale conversion on the gray scale image signal, and applies the second LUT 3401 to the gray image signal after bit expansion. By performing the second gradation conversion, an output gray image signal (signal based on the gray image signal after bit expansion, W3) is generated.

In the first embodiment, four types of LUTs, namely, LUT (R), which is a LUT for subpixel R, LUT (G), which is an LUT for subpixel G, LUT (B), which is an LUT for subpixel B, and LUT (W), which is a gray image LUT, is used. The RGB gray scale conversion circuit 334 in the RGB controller 33 is provided with one LUT (R) 3331, LUT (G) 3332, and LUT (B) 3333, respectively, as a first LUT. The LV gray scale conversion circuit 346 in the LV controller 34 includes a LUT (W) 3541 as the second LUT.

9 is a diagram showing the gray scale conversion characteristics by the LUT (R) 3331 according to the first embodiment. The LUT (G) 3332 and the LUT (B) 3333 basically have the same gray level conversion characteristics as the LUT (R) 3331, but the light of each subpixel of R, G, and B Due to the different transmission efficiencies, the characteristics are slightly different from each other. 10 is a diagram showing the gray scale conversion characteristics by the LUT (W) 3461 of the first embodiment.

As a result of the experiment, it was found that by adopting the gray scale conversion characteristics as shown in Figs. 9 and 10, the black representation of the dark portion and the color reproducibility of pure colors are improved, and the problem of whitening in pure colors is improved.

The gray scale conversion characteristic of the LUT (R) 3331 shown in FIG. 9 is realized by, for example, a gamma curve Y = X ^{γ with} γ = 0.5. In contrast, the gray conversion characteristics of the LUT (W) 3401 shown in FIG. The input / output characteristics of the LV were determined such that γ = 2.2.

11 is an explanatory diagram for improving color reproducibility of the dark portion by the operation of the RGB grayscale conversion circuit 334 and the LV grayscale conversion circuit 346 of the first embodiment. That is, it corresponds to the principle diagram of the cause and solution of a 1st problem.

As shown in Fig. 11 (a), a method of improving color reproducibility of the dark portion will be described as an example, in which a pixel expressing dark red color such as R value 16, G and B value 0 is displayed. . In the conventional method of improving the contrast ratio only by the LV image value, it is assumed that the luminance value of the corresponding pixel of the LV panel 36 needs to be set to, for example, 218.

In this case, as shown in Fig. 11A, the luminance value of the LV panel 36 is set so that R having the highest luminance among subpixels is appropriately displayed, so that the luminance of R after the composite transmission has a desired value. do. However, the luminance of G and B, which should be originally 0, has a large amount of light passing through the LV panel 36 from the backlight, and because of the light leakage of G and B in the RGB panel 35, the G and B emit light and are generally white. You will see red (grey).

On the other hand, for example, as shown in Fig. 11B, the amount of light passing through the LV panel with the luminance value of R being a larger value than the original (for example, 218) and the LV image value being a small value of 16. By lowering R, R after synthesized transmission shows a desired luminance, and G and B can cause light leakage to be extremely small, so that red color does not become dull and pure black red color.

By actively using this phenomenon, the LUT (R) 3331, the LUT (G) 3332, and the LUT (B) 3333 of the RGB grayscale conversion circuit 334 are drawn upward from the linear characteristics, especially in the dark portion. It is set to increase the voltage, and correspondingly, the LUT (W) 3611 for LV in the LV gray scale conversion circuit 346 is set to fall below the conventional one. Corresponds to

The RGB gradation conversion circuit 334 of the RGB controller 33 shown in Fig. 2 converts the RGB image signal after gradation conversion into an output RGB image signal (signal based on the RGB image signal after bit expansion, R3, G3, and B3). Is transmitted to the RGB panel 35 shown in FIG. In addition, the LV grayscale conversion circuit 346 of the LV controller 34 converts the gray image signal after the grayscale conversion into an LV panel 36 as an output gray image signal (a signal based on the gray image signal after bit expansion, W3). Send to

The RGB panel 35 receives and displays the output RGB image signals R3, G3, and B3. In addition, the LV panel 36 receives and displays the output gray image signal W3.

12 is a schematic cross-sectional view of a display module using two LCD panels of the first embodiment. The display module shown in FIG. 12 includes an RGB panel 35, an LV panel 36, a backlight unit 37, and a lamination 38 for bonding the RGB panel 35 and the LV panel 36 to each other. .

The RGB panel 35 includes a color filter substrate 35b, a TFT substrate 35c, a polarizing film 35a, and a driving IC 35d. The color filter substrate 35b is a substrate in which a black matrix, R, G, and B color filters are arranged, and a common electrode or the like is formed. The TFT substrate 35c is a substrate on which a TFT, an electrode, and the like are formed on the liquid crystal side.

The polarizing film 35a polarizes the light irradiated from the backlight unit 37. The driving IC 35d displays the RGB image processed by the RGB controller 33 on the RGB panel 35 by driving the TFT substrate 35c.

On the other hand, the LV panel 36 includes a glass substrate 36a, a TFT substrate 36b, a polarizing film 36c, and a driving IC 36d. Although the glass substrate 36a corresponds to the color filter substrate 35b of the RGB panel 35, unlike the color filter substrate 35b, it does not have a black matrix and a color filter. This is based on the LV panel 36 displaying an LV image, that is, a gray scale image expressed only in contrast from white to black.

The TFT substrate 36b and the polarizing film 36c are the same as the TFT substrate 35c and the polarizing film 35a of the RGB panel 35. The driver IC 36d displays the LV image processed by the LV controller 34 on the LV panel 36 by driving the TFT substrate 36b.

When viewed from the front, the RGB panel 35 and the LV panel 36 overlap each other so that the corresponding pixels are superimposed and displayed.

The backlight unit 37 includes a light guide panel 37a and a light source 37b. The light source 37b irradiates light to the light guide panel 37a. The light guide panel 37a refracts the light irradiated from the light source 37b to irradiate the LV panel 36. Light irradiated from the light guide panel 37a passes through the superimposed LV panel 36 and the RGB panel 35 in order to reach the human eye viewing the image display device.

The contrast ratio of each of the RGB panel 35 and the LV panel 36 is 1,500: 1 as in the conventional LCD panel. However, the contrast ratio is improved to 2,250,000: 1 by using two LCD panel structures as shown in FIG.

Furthermore, in Embodiment 1, the RGB controller 33 and the LV controller 34 cooperate to perform gradation conversion and color balance control, and in particular, the gradation characteristics of the black area are improved, thereby eliminating the so-called black floating phenomenon of the LCD panel, Clear black expression can be realized, and color reproducibility at low luminance (dark part) can be improved.

Next, an image display method using the image display device described as the first embodiment will be described with reference to FIGS. 1 to 12.

This image display method is constituted by superimposing two front side LCD panels and a rear side LCD panel, and executed by an image display apparatus which performs image display by transmitting backlight light in the order of the rear side LCD panel and the front side LCD panel. As an image display method, a gray image signal is generated for an input RGB image signal, an output gray image signal is generated from a signal based on a gray image signal, and a gray image signal or a signal based on a gray image signal is generated. By using the color balance correction process on the input RGB image signal to generate the RGB image signal after the color balance correction, and performing the first bit extension process on the luminance value of each sub-pixel of the RGB image signal after the color balance correction. To generate the RGB image signal after bit expansion, The signal is supplied as an output RGB image signal to the front LCD panel, and the output gray image signal is supplied to the rear LCD panel. Further, a second bit expansion process is performed on the signal based on the gray image signal to generate the gray image signal after the bit expansion, and the signal based on the gray image signal after the bit expansion is output as the gray image signal on the rear LCD panel. Supply for.

First, the gray converter 341 in the LV controller 34 receives the input RGB image signals R1, G1, and B1 from the I / F 31, and receives the input RGB image signals R1, G1, and B1. For each pixel, for each pixel, the luminance value of each RGB subpixel, that is, the maximum value is selected from the input RGB image signals R1, G1, and B1 and converted into a gray image by making it the representative value W1. The gray converter 341 transmits the luminance value as the gray image signal W1 to the horizontal edge hold circuit 342 for each pixel of the generated gray image.

The horizontal edge hold circuit 342 receives the gray image signal W1 and applies local edge hold processing in the horizontal direction to perform local enlargement processing of the edge area of the image. Furthermore, after the vertical edge hold circuit 343 applies the local edge hold processing in the vertical direction, the LPF circuit 344 applies a low pass filter to apply a low pass filter applied gray image signal (a signal based on a gray image signal). , W2). The LPF circuit 344 transmits the low pass filter applied gray image signal W2 to the color balance controller 332 of the RGB controller 33 and the LV bit expansion circuit 345 of the LV controller 34.

The LV bit expansion circuit (second bit expansion circuit 345) receives the low pass filter applied gray image signal W2, and performs a second bit expansion process thereon to generate a gray image signal after bit expansion. The LV bit expansion circuit 345 transmits the gray image signal after the bit expansion to the LV gray scale conversion circuit 346.

The LV gradation conversion circuit 346 receives the gray image signal after bit expansion, applies the second LUT 3541 to perform the second gray level conversion, and outputs the gray image signal after the gray level conversion to the output gray image signal (bit extension). The signal is transmitted to the LV panel 36 as the signal W3 based on the subsequent gray image signal.

The LV panel 36 receives and displays the output gray image signal W3.

On the other hand, in the RGB controller 33, the color balance controller 332 receives the input RGB image signals R1, G1, B1 through the delay circuit 331, and corresponds to the corresponding row transmitted from the LV controller 34 for each pixel. Based on the pass filter applied gray image signal W2, color balance correction is performed by adjusting the color balance using a correction coefficient. The color balance controller 332 transmits the RGB image signals R2, G2, and B2 after the color balance correction to the RGB bit extension circuit 333.

The RGB bit extension circuit 333 performs a first bit extension process on the luminance values of each sub-pixel of the RGB image signals R2, G2, and B2 after color balance correction to generate an RGB image signal after bit extension. The RGB bit extension circuit 333 transmits the RGB image signal after the bit extension to the RGB gray level conversion circuit 334.

The RGB gradation conversion circuit 334 receives the RGB image signal after bit extension, applies the first LUTs 3331, 3342, and 3343 to perform the first gradation conversion, and outputs the RGB image signal after the gradation conversion. It transmits to an RGB panel 35 as an RGB image signal (signal based on RGB image signal after bit expansion, R3, G3, B3).

The RGB panel 35 receives and displays the output RGB image signals R3, G3, and B3.

The output gray image signal W3 displayed on the LV panel 36 and the output RGB image signals R3, G3, B3 displayed on the RGB panel 35 are basically in the same relationship as described with Fig. 6 (c). Therefore, each RGB subpixel is represented by an appropriate luminance value.

Next, the effect of the said image display apparatus and the image display method is demonstrated.

With the above configuration, since the color balance controller 332 of the RGB controller 33 corrects and controls the color balance as described with reference to FIG. 6, the original color can be displayed even in the mixed color part, and the color balance collapses. It is possible to eliminate the defect and to improve the color reproducibility. In addition, since the RGB grayscale conversion circuit 334 and the LV grayscale conversion circuit 346 have grayscale conversion characteristics as shown in Figs. 9 and 10, the black expression and the color reproduction of pure color are improved as described above, and the pure color The problem of whitening is improved.

In particular, in the first embodiment, after performing color balance correction by the color balance controller 332, the gray scale conversion circuit 334 performs the gray scale conversion processing necessary for display output to the RGB panel 35. . That is, since the color balance correction can be performed in the linear state before the gradation conversion as shown in Figs. 9 and 10, the characteristic of the color can be maintained well regardless of the luminance, and the color reproducibility can be effectively improved.

Further, the RGB gradation conversion circuit 334 and the LV gradation conversion circuit 346 are positioned to be subjected to the final step processing of the RGB controller 33 and the LV controller 34, and the RGB gradation conversion circuit 334 is thus accompanied. The RGB bit extension circuit 333 and the LV bit extension circuit 345 which perform bit extension processing for improving the gradation conversion accuracy in the LV gradation conversion circuit 346 are located immediately before that. That is, all the main processes including the color balance correction before the bit extension processing are processed with 8 bits, which are the same bit width as the input RGB image signals R1, G1, and B1, and bit extension is performed as far as possible after the color balance correction processing. Doing. As a result, for example, the memory capacity required for the delay circuit 331, the color balance processing, and the edge hold processing are compared with the case where the bit expansion processing is performed immediately after receiving the input RGB image signals R1, G1, and B1. For example, the circuit scale required for each operation can be greatly reduced.

In addition, since the circuit scale can be reduced as described above, it is possible to reduce power consumption.

According to the above configuration, the color balance controller 332 calculates the RGB individual correction coefficient F by multiplying the luminance ratio by the adjustment function of 0 to 1, and uses the correction coefficient F to correct the color balance. The following RGB image signal is generated. By suppressing the luminance ratio change range by the adjustment function in this manner, the luminance ratio is prevented from acting excessively, thereby improving color reproducibility and effectively suppressing side effects such as double lines.

<Variation example>

Next, a modification of the image display device and the image display method shown as the first embodiment will be described. 13 shows the configurations of the RGB controller 73 and the LV controller 74 of the present modification. The present modified example is different from the RGB controller 33 and the LV controller 34 shown as the first embodiment (1), and the signal transmitted by the LV controller 74 to the color balance controller 732 of the RGB controller 73. The processing contents of the color balance controller 732 and the processing sequence of the delay circuit 731 and the color balance controller 732 in the RGB controller 73 are different.

First, the LV controller 74 is not the low pass filter applied gray image signal W2 output from the LPF circuit 344 to the color balance controller 732 of the RGB controller 73, but the gray converter 341. Transmits the gray image signal W1 to be output. The color balance controller 732 receives the gray image signal W1 and uses it to perform color balance correction processing on the input RGB image signals R1, G1, and B1, thereby performing RGB image signals R2 and G2 after color balance correction. , B2) is being generated.

In addition, in the color balance controller 332 described in the first embodiment, the adjustment function (1-TH) obtained by subtracting the predetermined value TH from 1 as shown in equations (4) to (6) is converted into the luminance ratio. The function F calculated by multiplying and multiplying the predetermined value TH further is multiplied by each of the input RGB image signals R1, G1, and B1 as RGB individual correction coefficients, but in the color balance controller 732, Do not multiply the adjustment function F. That is, in the color balance controller 732, the RGB signal represented by the equations (10) to (12) in which W2 is replaced by W1 with respect to equations (1) to (3) is an RGB image signal (R2) after color balance correction. , G2, B2).

R2 = R1 × (R1 / W1) (10)

G2 = G1 × (G1 / W1) (11)

B2 = B1 × (B1 / W1) (12)

The delay circuit 731 of the RGB controller 73 receives the RGB image signals R2, G2, and B2 after color balance correction output by the color balance controller 732, and delays them appropriately. In the present modification, the term “appropriate delay” refers to the total processing time by the horizontal edge hold circuit 342, the vertical edge hold circuit 343, and the LPF circuit 344 in the LV controller 74, and RGB. The RGB image signals R2 and G2 after color balance correction, which correspond to the processing time difference of the color balance controller 732 in the controller 73, are transmitted to the RGB bit expansion circuit 333 through the delay circuit 731. , B2 and the low pass filter applied gray image signal W2 transmitted from the LPF circuit 344 to the LV bit expansion circuit 345.

It goes without saying that the image display device and the image display method shown as this modification obtain the same effects as the image display device and the image display method shown as the first embodiment.

Particularly, in the image display device and the image display method shown as the present modification, the signal W1 received by the color balance controller 732 from the LV controller 74 is the horizontal edge hold circuit 342 and the vertical edge hold. It is before the viewing angle correction is performed by the circuit 343. That is, for the gray image signal W1 output from the gray converter 343, the color balance correction processing is performed in the RGB controller 73 and the viewing angle correction processing is independently performed in the LV controller 74. This reduces side effects such as double lines that appear on the edge.

Therefore, in the color balance correction processing in the color balance controller 732 as described above, the multiplication of the adjustment function F with respect to the luminance ratio may be unnecessary. Therefore, compared with the case of the first embodiment, it is possible to further reduce the circuit scale.

Next, the experimental effect which concerns on the said Embodiment 1 and a modification is demonstrated. Fig. 14 is a photograph of the result of displaying on the actual machine an image of a bright grid drawn on a dark background. FIG. 14 (a) is a photograph when the actual machine is viewed from the front when TH is 0 in the first embodiment, that is, the image is displayed with the correction effect by the luminance ratio as 100% without operating the adjustment function. . FIG. 14 (b) is a photograph when the actual machine is viewed from the front when the image is displayed by suppressing the TH by 0.75, that is, the correction effect by the luminance ratio to 25% in the first embodiment. Fig. 14C is a photograph of the actual machine viewed from the front in the above modification. (D), (e), (f) is a photograph in the case where a real machine is seen from the diagonal in the horizontal direction in each of FIGS. 14 (a), (b), (c).

In the case of the front view, all of them have no problem.

When viewed from the diagonal direction, in particular, double lines are markedly visible in Fig. 14 (d). In Fig. 14E, the double line is relaxed and displayed. In Fig. 14 (f), the double line is more inconspicuous.

As described above, in the first embodiment, the double line that was remarkable when the adjustment function is not operated is alleviated and displayed by operating the adjustment function. In the above modification, the image quality better than that in the first embodiment is realized even though the multiplication by the adjustment function is not performed.

The image display device and the image display method of the present invention are not limited to the above-described embodiments and modifications described with reference to the drawings, and various modifications are possible within the technical scope.

For example, the gray scale conversion characteristics of each LUT are not limited to the characteristics as shown in Figs. 9 and 10, and needless to say, they may have other characteristics.

The input RGB image signals R1, G1, and B1 are 8 bits, but may be other bit widths such as 10 bits.

In addition to the above, it is possible to select or change the configurations exemplified in the above embodiments and modifications to other configurations as appropriate without departing from the spirit of the present invention.

R1, G1, B1: input RGB picture signal
R2, G2, B2: RGB image signal after color balance correction
R3, G3, B3: Output RGB image signal (signal based on RGB image signal after bit expansion)
W1: gray image signal
W2: Gray image signal with low pass filter (signal based on gray image signal)
W3: output gray image signal (signal based on gray image signal after bit expansion)
33, 73: RGB controller (first controller)
331, 731: delay circuit
332, 732: color balance controller
333: RGB bit extension circuit (first bit extension circuit)
334: RGB grayscale conversion circuit
34, 74: LV controller (second controller)
341: gray converter
342: horizontal edge hold circuit (edge hold circuit)
343: vertical edge hold circuit (edge hold circuit)
344: LPF circuit
345: LV bit expansion circuit (second bit expansion circuit)
346: LV gradation conversion circuit (gray gradation conversion circuit)
35: RGB panel (front LCD panel)
36: LV panel (back LCD panel)

Claims (14)

An image display apparatus configured by superimposing two front side LCD panels and a rear side LCD panel, and performing backlight for displaying images by transmitting backlight light in the order of the rear side LCD panel and the front side LCD panel.
Having a first controller and a second controller,
The second controller generates a gray image signal with respect to an input RGB image signal, and then generates an output gray image signal from a signal based on the gray image signal, and transmits the output gray image signal to the rear LCD panel. About the supply,
The first controller performs color balance correction processing on the input RGB image signal by using the gray image signal or a signal based on the gray image signal transmitted from the second controller, thereby performing RGB after color balance correction. A color balance controller for generating an image signal,
The first controller includes a first bit expansion circuit for performing a first bit expansion process on a luminance value of each sub pixel of the RGB image signal after the color balance correction to generate an RGB image signal after bit expansion. A signal based on the RGB image signal after bit expansion is supplied to the front LCD panel as an output RGB image signal,
The second controller sets the maximum value of the luminance value of each RGB sub-pixel of the front LCD panel with respect to each pixel of the rear LCD panel with respect to the input RGB image signal, thereby representing the gray image. An image display device for generating a signal.
The method of claim 1,
The first controller stores the first lookup table for performing the first gray level conversion on the RGB image signal separately for the luminance value of each RGB subpixel, and the first lookup table for the RGB image signal after the bit expansion. And an RGB gradation conversion circuit for generating the output RGB image signal by performing the first gradation conversion by applying a lookup table.
The method according to claim 1 or 2,
The second controller includes a second bit expansion circuit that performs a second bit expansion process on a signal based on the gray image signal to generate a gray image signal after bit expansion, and the gray image signal after bit expansion. An image display device which supplies a signal based on a signal to the rear LCD panel as the output gray image signal.
The method of claim 3, wherein
The second controller stores a second lookup table that performs a second grayscale conversion on the gray scale image signal, and applies the second lookup table to the gray image signal after the bit expansion to perform the second grayscale conversion. And a gray scale conversion circuit for generating the output gray image signal.
The method of claim 1,
And the second controller is provided with a gray converter which generates the gray image signal which is a gray scale image signal from the input RGB image signal.


delete The method of claim 1,
The second controller comprises an edge hold circuit for applying a local edge hold process to the gray image signal to generate a gray image signal after an edge hold process;
And a low pass filter circuit for generating a signal based on the gray image signal by applying a low pass filter to the gray image signal after the edge hold processing.
The method of claim 7, wherein
And the edge hold circuit comprises a horizontal edge hold circuit for applying a local edge hold process in a horizontal direction and a vertical edge hold circuit for applying a local edge hold process in a vertical direction.
An image display method which is constituted by superimposing two front side LCD panels and two rear side LCD panels, and which is executed by an image display apparatus which performs image display by transmitting backlight light in the order of the rear side LCD panel and the front side LCD panel. As
With respect to an input RGB image signal, a gray image signal is generated by generating a gray image signal by setting the maximum value of the luminance value of each RGB sub-pixel of the front LCD panel with respect to each pixel of the rear LCD panel. Generate an output gray image signal from a signal based on the image signal,
An RGB image signal after color balance correction is generated by performing a color balance correction process on the input RGB image signal using the gray image signal or a signal based on the gray image signal,
Performing a first bit expansion process on the luminance values of each sub-pixel of the RGB image signal after the color balance correction to generate an RGB image signal after bit expansion,
Supplying a signal based on the RGB image signal after the bit expansion as an output RGB image signal to the front side LCD panel,
And an image display method for supplying the output gray image signal to the rear LCD panel.
The method of claim 9,
Performing a second bit expansion process on the signal based on the gray image signal to generate a gray image signal after bit expansion, and converting the signal based on the gray image signal after the bit expansion as the output gray image signal to the rear surface; An image display method to supply the side LCD panel. The method of claim 9,
Generating the RGB image signal after the color balance correction is performed on the luminance ratio of each subpixel obtained by dividing the luminance value of each subpixel of the input RGB image signal by a signal based on the gray image signal. Calculate the RGB individual correction coefficient F by further multiplying the adjustment function (1-TH) of 0 to 1, and multiplying the RGB individual correction coefficient F by the luminance value of each sub-pixel of the input RGB image signal. An image display method comprising generating an RGB image signal after color balance correction.
The method of claim 9,
Generating the RGB image signal after the color balance correction calculates a luminance ratio by dividing the luminance value of each sub-pixel of the input RGB image signal by the gray image signal, and the luminance ratio for each of the input RGB image signals. Generating an RGB image signal after the color balance correction by multiplying by;
The method of claim 1,
The color balance controller is an adjustment function having a range from 0 to 1 for the luminance ratio of each subpixel obtained by dividing the luminance value of each subpixel of the input RGB image signal by a signal based on the gray image signal. The RGB individual correction coefficient F is calculated by further multiplying (1-TH), and the RGB image signal after the color balance correction is multiplied by multiplying the RGB individual correction coefficient F by the luminance value of each sub-pixel of the input RGB image signal. An image display device to generate.
The method of claim 1,
The color balance controller calculates a luminance ratio by dividing the luminance value of each sub-pixel of the input RGB image signal by the gray image signal, and multiplies the luminance ratio with respect to each of the input RGB image signals by the color balance correction. An image display device for generating an RGB image signal.

Images