JP2003189127A - Video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display device that display a video where a black decay, a pseudo color, and a pseudo contour caused by reduction of information amount at a low luminance by inverse gamma correction processing and occurring when a dark video image is displayed in particular, are hardly conspicuous. <P>SOLUTION: An inverse gamma correction circuit 3 corrects a video signal (RGB signal 1) subjected to gamma correction to obtain a video signal (RGB signal 2), a display rate arithmetic circuit 23 obtains a video display rate of the RGB signal 2, a coefficient setting circuit 24 obtains a low luminance signal correction coefficient of a low luminance signal correction circuit 21 on the basis of the video display rate, a comparison selection circuit 22 compares an output (RGB signal 3) of the low luminance signal correction circuit 21 receiving the RGB signal 1 with the RGB signal 2, and the signal 3 or signal 2 which is greater is outputted to a PDP module 5 via a video adjustment circuit 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in image quality of a low-luminance portion of a video (hereinafter, referred to as a dark video) having a low overall brightness when the video is displayed on a video display device.

[0002]

2. Description of the Related Art FIG. 11 is a system configuration diagram of a conventional video display device. In the figure, 1 is an analog-digital conversion circuit (hereinafter referred to as A / D conversion circuit), 2 is an inverse matrix conversion circuit, 3 is an inverse gamma correction circuit, 4 is an image adjustment circuit, and 5 is a PDP (Plasma Display Panel) module. .

Next, the operation will be described. In normal television broadcasting, the RGB signal to be transmitted has a gamma correction (γ = 0.4) as shown in FIG. 12 in consideration of the luminance characteristic of the CRT.
5) is performed, converted into component video signals Y, Cb, Cr by matrix conversion, further converted into composite color signals and transmitted (not shown). The horizontal axis and the vertical axis in FIG. 12 represent the video signal level, which is normalized by setting the black level to 0 and the white level to 1, and shows the video signal level on a linear scale display. Also, black level 0
And white level 1 are 0 and 25 respectively when expressed in 8 bit gradation.
Therefore, in the following description, the gradation is expressed as 0th gradation and 255th gradation.

A video signal before gamma correction is called an original video signal. FIG. 13 is a diagram for explaining the gamma correction using the original video signal as a ramp waveform signal. However, due to the gamma correction during transmission, the ramp waveform signal (original video signal) shown in FIG. The signal is gamma-corrected as shown in b) and converted into a signal in which the low-luminance side is expanded.

In FIG. 11, the received analog component video signals Y, Cb and Cr are A / D conversion circuits 1.
Is converted into a digital signal by the inverse matrix conversion circuit 2 and then converted into three primary color signals of R (red), G (green), and B (blue) by the inverse matrix conversion circuit 2. The RGB signal is a gamma-corrected signal. (Hereinafter, referred to as RGB signal 1.).

The RGB signal 1 has a gamma correction (γ
= 0.45), the amplitude-luminance characteristic is non-linear as shown in FIG. Therefore, the inverse gamma correction circuit 3 having the inverse gamma correction (γ = 2.2) characteristic shown in FIG. 14 performs the inverse gamma correction, and the amplitude-luminance characteristic linear RGB signal shown in FIG. Signal 2). It should be noted that the RGB signal 2 is basically the same as the original video signal except that the RGB signal 2 is a digital signal that has undergone inverse gamma correction by digital signal processing.

Next, the RGB signal 2 is adjusted in brightness, contrast, color temperature, etc. by the image adjusting circuit 4 according to the user's preference, the brightness of the image to be displayed, the installation environment of the display device, etc., and the PDP module 5 And is displayed as an image.

The RGB signal 1 input to the inverse gamma correction circuit 3 is a digital signal of 8 bits (256 gradations) for each color. The inverse gamma correction circuit 3 is, for example, an input / output 8-bit conversion table ROM having inverse gamma correction data shown in FIG.
(Hereinafter referred to as an inverse gamma correction ROM). The RGB signal 1 of 8 bits for each color is numerically converted by the inverse gamma correction ROM to obtain the RGB signal 2. The RGB signal 2 subjected to the inverse gamma correction processing is returned to the original video signal in principle, but the original video signal is an analog signal, whereas the RGB signal 2 is an 8-bit digital signal.

When the RGB signal 2 is displayed on a pixel-by-pixel basis and is displayed on a display device such as a PDP display device having a large screen size, contour contours appear especially in a dark portion of an entirely dark image. The "pseudo contour" may be noticeable. By digitizing this pseudo contour, the stepwise brightness change appears in the part where there is originally no stepwise brightness change,
This is a phenomenon that is recognized as an unnatural image.

Further, in the dark portion of the image, the color signal components (R, G, B) of the RGB signal 2 should be (2, 2, 2) (2, 1, 1), which is essentially an achromatic color. The place where it should be is slightly reddish, or (1, 1,
The place that should be 0) becomes (0, 1, 0), and the place that should originally have a yellowish tint may have a greenish tint. As described above, a color different from the original color may appear due to digitalization, but this phenomenon will be referred to as “pseudo color” hereinafter.

In general, in the case of a normal bright image, it is said that the pseudo contour and the pseudo color are 6-bit gradation expression for each color, but there is no practical problem, but conversely, a dark image such as a movie image is displayed. In many cases, 10-bit to 12-bit gradation expression is required.

This is because the difference of 1 gradation is only 1/200 in the bright portion such as the 200th gradation, but 1 gradation such as 1/2 in the dark portion such as the 2nd gradation. The difference is very large, and because the human eye has the property of adapting to the brightness of the target object, when the entire screen is dark, the sensitivity to the gradation of the low brightness part increases and the first floor This is due to the property that the change in brightness due to the key becomes recognizable.

The pseudo contour and the pseudo color are 8 bits.
In the case of the gradation display of No. 2, it is a phenomenon which becomes a serious problem mainly in the portion from the 0th gradation to the 5th gradation (luminance level 0 to 0.02).

[0014]

In the conventional image display device that performs the inverse gamma correction process by digital processing as described above, when displaying a dark image, contour-shaped pseudo lines are displayed in the low luminance portion of the dark image. There were problems such as the appearance of outlines and pseudo colors.

The present invention has been made in order to solve the above problems, and is particularly related to the display of a dark image, in which the pseudo contour is less noticeable in the low luminance portion of the dark image, and the pseudo color is further reduced. An object of the present invention is to obtain a video display device that can be improved and has less influence on parts other than the low brightness part.

[0016]

[Means for Solving the Problems] Claim 1 according to the present invention
The image display device of (1) includes an inverse gamma correction circuit for performing an inverse gamma correction on the gamma-corrected image signal, and a low-brightness signal correction circuit for attenuating the gamma-corrected signal with a predetermined attenuation coefficient and outputting a low-brightness correction signal. And a comparison / selection circuit for selecting and outputting a larger output of the inverse gamma correction circuit and the low luminance signal correction circuit.

According to a second aspect of the invention, in the image display apparatus according to the first aspect, the attenuation coefficient of the low luminance signal correction circuit is set based on the image display rate of the image signal. To do.

According to a third aspect of the present invention, in the image display apparatus according to the first aspect, the attenuation coefficient of the low luminance signal correction circuit is set based on the set value of the display luminance of the display device. Characterize.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. Embodiment 1. 1 is a system configuration diagram showing an image display device according to a first embodiment of the present invention. In the figure, 1 is an A / D conversion circuit, 2 is an inverse matrix conversion circuit, 3 is an inverse gamma correction circuit, 4 is an image adjustment circuit, and 5 is P.
DP module, 21 is a low-brightness signal correction circuit, 22 is a comparison / selection circuit for outputting the output of the inverse gamma correction circuit 5 and the output of the low-brightness signal correction circuit 21, which is larger, and 23 is a display rate calculation for calculating a video display rate. Circuit, 24 is a display ratio calculation circuit 2
3 is a coefficient setting circuit for setting a low brightness signal correction coefficient of the low brightness signal correction circuit 21 based on the output of FIG.

Next, the operation will be described. In FIG. 1, the same parts as those in FIG. 11 are designated by the same reference numerals. FIG. 2 is a diagram for explaining the operation of FIG. 1, in which the horizontal axis and the vertical axis are normalized by setting the black level to 0 and the white level to 1, and show the video signal level in a linear scale display, and the horizontal axis shows the original image. Signals are shown on the vertical axis, which are the RGB signal 1, the RGB signal 2, and the RGB signal 3, which will be described later, for the original video signal.

According to the present invention, in the case where the pseudo contour or pseudo color generated in the low luminance part of a dark image is a gradation display of 8 bits, the 0th gradation to the 5th gradation (brightness level 0 to 0.02).
Attention is paid to the fact that the phenomenon is a problem in a certain degree, and in order to reduce these, an attempt is made to utilize abundant data on the low luminance side generated by the gamma correction of the RGB signal 1.

As can be seen from FIGS. 2 and 3, the gamma correction has a characteristic of extending the low luminance side extremely. In FIG. 3, the 0th gradation of the RGB signal 2 corresponds to the 0th to 20th gradations of the RGB signal 1. Similarly, the 21st to 28th tones for the first tones, the 29th to 33rd tones to the second tones, the 34th to 38th tones to the 3rd tones, and the 4th tones. The 39th to 42nd gradations correspond to the 5th gradation, and the 43rd to 46th gradations correspond to the 5th gradation. That is, the RGB signal 1 corresponds to the 0th to 5th gradations, and the RGB signal 1 corresponds to the 0th to 46th gradations. Therefore, the amount of data increases about 9 times by gamma correction, and more on the low brightness side. The data is concentrated.

As shown in FIG. 2, the amplitude is gamma-corrected and-
The RGB signal 1 having a non-linear luminance characteristic is the inverse gamma correction circuit 5
RG with inverse gamma correction and linear amplitude-luminance characteristics
Returned to B signal 2.

At the same time, the RBG signal 1 is also input to the low luminance signal correction circuit 21 and attenuated by a predetermined attenuation coefficient (hereinafter referred to as the low luminance signal correction coefficient) to correct the display characteristics on the low luminance side. Low-brightness correction signal (hereinafter RG
B signal 3) is generated.

Next, the operation of the low luminance signal correction circuit 21 will be described in detail. Input RGB signal 1 is X, output is R
The GB signal 3 is Y, the low luminance signal correction coefficient is C, the correction magnification is n, and the input value when the output of the inverse gamma correction data becomes 1 for the first time is A, and Y = CX = (n / A) X. -(1) (However, X and Y are 8-bit signals, and n is a numerical value of 1 or more). Here, from FIG. 15, A =
Since it is 21, it can be expressed as Y = (n / 21) X.

2 and 4 show the RGB signal 3 when the correction magnification n is set to 2, 3 and 4. At this time, the low-brightness signal correction coefficient C of the equation (1) is approximately 0.1, 0.15, and 0.2.

Further, in FIG. 3, inverse gamma correction data and n =
The data of the RGB signal 3 when set to 2, 3, and 4 is shown. When n = 2, RGB signal 3 up to input value 21 gradations
It can be seen that the output is doubled in terms of the number of gradations, tripled when n = 3, and quadrupled when n = 4. That is, the amount of information on the low-luminance side increases in proportion to the correction magnification n, and as a result, the interval of the pseudo-contours on the low-luminance side narrows, making it difficult to recognize the pseudo-contours.

The pseudo color is similarly improved, but since the number of incorrect RGB color values is reduced due to digitization, the pseudo contour is improved more than the effect.

FIG. 4 is a diagram for explaining the operation of the comparison / selection circuit 22, which is an enlarged view of the low luminance portion of FIG. In the comparison / selection circuit 22, the output RG of the low luminance signal correction circuit 21 is output.
The B signal 3 and the output RGB signal 2 of the inverse gamma correction circuit 5 are compared, and the one with the larger signal level is selected to select the image adjustment circuit 4.
Is output to the PDP module 5 via. The point where the RGB signal 2 and the RGB signal 3 switch is referred to as point S.

For example, when n = 3, the RGB signal 3 output of the low-luminance signal correction circuit 21 is used on the low-luminance side (the image side is dark) from point S in the figure, and the gradation display characteristics on the low-luminance side are Be improved. The points S in FIGS. 4 and 3 correspond to each other. Further, since the RGB signal 2 output of the conventional inverse gamma correction circuit 5 is used on the high luminance side from the point S, an image equivalent to the conventional one can be obtained on the high luminance side.

By the correction using the RGB signal 3 described above, there is an effect that it becomes possible to recognize an unrecognizable object such as grass in a dark forest. Further, in FIG. 4, the point S in the case of n = 3 is located at the signal level of the original video signal, which is 0.03 (sixth gradation), which is considerably low luminance.
Since this correction is limited to the low-brightness portion, it has little influence on the entire display image and does not give an unnatural impression.

FIG. 5 is an enlarged view of the low luminance part of the RGB signal 3 for n = 3 in FIG. When n = 3, low luminance signal correction coefficient C
Is about 0.15, which means that the RGB signal 1 has been compressed to about 1/7, but if attention is paid to the 0th to 2nd gradations of the original video signal, about 2 times gradation expression is realized. I understand.

Next, a case where the low luminance signal correction coefficient C = n / A is determined based on the image display rate will be described. A is uniquely determined from the inverse gamma correction coefficient, whereas if the correction magnification n is determined by the coefficient setting circuit 24 based on the image display rate calculated by the display rate calculation circuit 23, it is suitable for each image. It is possible to correct the low luminance signal.

An example of display rate calculation in the display rate calculation circuit 23 will be described below. The display ratio calculation circuit 23 obtains the sum of each 8-bit RGB signal data in one vertical period, and sums the sum and the maximum value of all data (255).
× 3 × total number of pixels) is calculated as the image display rate, and the correction magnification n in the next one vertical period is determined. The image display rate corresponds to the average brightness level.

Generally, when the image display rate is about 10% or less, it is perceived as a dark image. Therefore, when the image display rate is 10% or less, the correction factor n is set to be large and the low brightness is set. Improve the image quality on the side. However, if the correction magnification n is too large, the dark part of the image may be too bright and may be perceived as unnatural, so the maximum value of the correction magnification n is about 4, that is, the signal level at point S is about 0.05. It is appropriate to set up to (13th gradation).

FIG. 6 shows an example of the relationship between the image display rate and the correction magnification n in the coefficient setting circuit 24.
If it is more than%, n = 1 (no correction) and the image display rate is 10
It shows the case where n = 1 to 4 changes as the percentage changes from 0% to 0%. Further, in order to prevent unnaturalness due to the correction, for example, as shown by a dotted line, the correction magnification n
The upper limit may be set to 2.5.

As described above, by determining the low-brightness signal correction coefficient of the low-brightness signal correction circuit 21 according to the image display rate,
Pseudo contours are reduced on the low luminance side of a dark image, and pseudo color is also improved.

In the above description, the video adjustment circuit 4 is installed between the comparison / selection circuit 22 and the PDP module 5, but it is installed after the inverse matrix conversion circuit 2 to adjust the RGB signal 1. However, the effects of the present invention can be obtained.

Further, in the above description, each video signal is explained as an 8-bit digital signal, but it is not always 8 bits.
Needless to say, 6 to 10 bits can be selected according to the type of video display device and the digital signal processing circuit.

Embodiment 2. Generally, when viewing an image in a dark environment, the user reduces the brightness of the entire screen. 1 / maximum brightness when the surrounding environment is dark
When the luminance is lowered by using the video adjusting circuit 4 when the luminance is lowered to 2, it becomes the same as converting the 8-bit video signal to the 7-bit video signal, so that the image quality deterioration such as the pseudo color and the pseudo contour is caused especially in the low brightness portion. Not only is it conspicuous, but it may cause "blackout" where the dark part of the image looks almost black. Hereinafter, a method of reducing the brightness of the entire screen by reducing the display brightness of the PDP module 5 will be described.

FIG. 7 is a system configuration diagram showing an image display device according to a second embodiment of the present invention. In the figure,
1 is an A / D conversion circuit, 2 is an inverse matrix conversion circuit, 3
Is an inverse gamma correction circuit, 4 is an image adjustment circuit, 5 is a PDP module, 21 is a low-brightness signal correction circuit, 22 is a comparison / selection circuit, 25 is a coefficient setting circuit for setting a low-brightness signal correction coefficient by a brightness mode signal, 26 Is a sustain pulse frequency setting circuit for setting the sustain pulse frequency by the brightness mode signal.

Next, the operation will be described. The configuration is the same as that of FIG. 1 except for the coefficient setting circuit 25 and the sustain pulse frequency setting circuit 26. Therefore, how to determine the correction magnification n in the coefficient setting circuit 25 and the operation of the sustain pulse frequency setting circuit 26 will be described.

The subfield method will be described below as an example of the gradation expression method of the PDP module 5. The subfield method is, for example, as shown in FIG.
8 subfields (SF1 to S
F8), and the number of sustain pulses in the display period is set so that the relative ratio of the luminance of the subfield becomes 1: 2: 4: 8: 16: 32: 64: 128, and the subfield of each subfield is set. By combining the presence or absence of light emission, it is possible to express 256 different gradations.

Consider a case where SF1 displaying the minimum luminance includes four sustain pulses. When the sustain pulse frequency is reduced to 3/4 and 1/2 of the frequency (Fmax) that gives the maximum brightness, the number of sustain pulses included in SF1 is 3 and 2 respectively.
The total display brightness is 3/4,
It drops to 1/2.

As described above, since the number of sustain pulses included in the display period of each sub-field can be changed by changing the frequency of the sustain pulse, the luminance is changed while maintaining 256 gradation representations. It is possible.

Actually, the relative ratio of the subfield luminance is 1: 2: 4: 8: 16: 32: 64: 128.
However, even if the luminance ratio is slightly deviated, the linearity of the image is slightly impaired, but the influence on the image is relatively small. Therefore, by setting the sustain pulse frequency by the brightness mode signal, it is possible to adjust the brightness without impairing the gradation characteristics.

There are two methods for lowering the brightness of the entire screen: a method of lowering the level of the video signal by the video adjusting circuit 4 and a method of lowering the sustain pulse frequency by the sustain pulse frequency setting circuit 26. The brightness mode is set according to the type of video displayed, and the sustain pulse frequency corresponding to the brightness mode is set by the sustain pulse frequency setting circuit 26 to set the brightness of the entire screen. It is better to use as a supplement.

The setting of the correction magnification n will be described below.
For example, when viewing with a high brightness because the surrounding environment is bright, that is, when a display with a high brightness is instructed, n = 1 is set as in the conventional case. When n = 1, the output of the low-brightness signal correction circuit 21 becomes equal to or lower than the output of the gamma correction circuit 5, so that the comparison / selection circuit 22 always selects the output of the gamma correction circuit 5. This is because when the surrounding environment is bright, the deterioration of image quality on the low luminance side is not noticeable, and it is not necessary to correct the low luminance portion.

On the other hand, when viewing an image in a dark environment, the user generally lowers the brightness of the entire screen.
For example, when the brightness setting value is decreased to 1/2 of the maximum brightness setting value by decreasing the sustain pulse frequency to 1/2 based on the brightness mode signal, the whole brightness is reduced to 1/256 while the 256 gradation display is maintained. Can be lowered to 2. In this case, since the brightness for one gradation is halved, pseudo contours and pseudo colors are reduced, but since the surroundings are dark, the sensitivity of the eyes to the low brightness part of a dark image is increased, and the low brightness is reduced. It becomes easier to recognize pseudo contours and colors in parts.

Therefore, the brightness setting value is the maximum brightness setting value 3
Even when it is lowered to / 4 and 1/2, for example, n = 2 and n =
The value of the correction magnification n is set as shown in No. 3, the correction of the low-luminance portion is performed, and the pseudo contour and the pseudo color are reduced to improve the image degradation on the low-luminance side. Generally, it is sufficient that the brightness mode (brightness setting value) corresponding to the environmental condition is 2 to 3 ways (up to about 4 ways at most).

As described above, the sustaining pulse frequency setting output of the sustaining pulse frequency setting circuit 26 is controlled by the luminance mode signal, and the correction magnification n of the coefficient setting circuit 25 is controlled to correct the low luminance signal of the low luminance signal correcting circuit 21. Since the coefficient C is set, the pseudo contour is reduced and the pseudo color is also improved on the low luminance side of the dark image, particularly when the image is viewed in a dark environment with the screen luminance lowered. Further, since the sustain pulse frequency is lowered, the change in luminance per gradation is small, so that the pseudo contour and the pseudo color are more inconspicuous.

Embodiment 3. 9 is a system configuration diagram showing a video display device according to a third embodiment of the present invention.
In the figure, 1 is an A / D conversion circuit, 2 is an inverse matrix conversion circuit, 3 is an inverse gamma correction circuit, 4 is an image adjustment circuit, 5 is a PDP module, 21 is a low luminance signal correction circuit, and 22 is a comparison / selection circuit. , 23 are display rate calculation circuits, 26
Is a sustain pulse frequency setting circuit, and 27 is a coefficient setting circuit for setting a low luminance signal correction coefficient according to the image display rate and the luminance mode signal.

Next, the operation will be described. 1 and 7 except for the coefficient setting circuit 27, the setting of the value of the correction magnification n in the coefficient setting circuit 27 will be described below with reference to the drawings.

The coefficient setting circuit 27 determines the brightness setting value based on the brightness mode signal and the image display rate. When the brightness setting value is the maximum brightness (the sustain pulse frequency is the maximum), n = 1 is set, and the correction on the low brightness side is not performed. On the other hand, when the brightness setting value is lowered to 3/4 or 1/2 of the maximum brightness, the upper limit value of the correction magnification n is set to, for example, 2 or 3 based on the brightness setting value. The low-luminance side is corrected based on the video display rate output of the display rate calculation circuit as in the first embodiment. At this time, the relationship between the brightness setting value and the maximum value of the correction magnification n is not particularly specified, but the correction magnification n is set to increase as the brightness setting value decreases.

As described above, since the correction magnification n is controlled on the basis of the brightness setting value and the image display rate, it is possible to adaptively improve the image quality on the low brightness side for more images. it can.

Although the embodiment of the present invention has been described with respect to the plasma display device, it goes without saying that the present invention is also effective for other types of image display devices such as a liquid crystal display device.

[0057]

Since the present invention is constructed as described above, it has the following effects.

Since the image display apparatus according to the present invention corrects only the signal of the low luminance part by the gamma correction signal attenuated by the predetermined attenuation coefficient, it has no effect on the high luminance part. In addition, it is possible to make the pseudo contour generated in the low luminance portion inconspicuous when a dark image is displayed and to improve the pseudo color.

Further, since the signal of the low luminance part of the dark image (the image having a low image display rate) is corrected by the gamma correction signal attenuated by the attenuation coefficient set by the image display rate, the high luminance part is corrected. However, the pseudo contour generated in the low-luminance portion when a dark image is displayed can be made inconspicuous, and the pseudo color can be improved.

Further, when displaying with reduced brightness in a dark environment, by setting the attenuation coefficient based on the set value of the display brightness of the display device, the signal of the low brightness part of the dark image can be obtained. Only the gamma correction signal that has been attenuated by the low attenuation coefficient set by the brightness setting value is used for correction, so there is no effect on the high-brightness part, and when the dark image is displayed, the low-brightness The pseudo contour generated in the part can be made inconspicuous and the pseudo color can be improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a video display device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the low luminance signal correction circuit according to the present invention.

FIG. 3 is a diagram showing an example of correction data on the low luminance side in the present invention.

FIG. 4 is a diagram illustrating an operation of a comparison / selection circuit according to the present invention.

FIG. 5 is a diagram for explaining the operation of the comparison / selection circuit according to the present invention.

FIG. 6 is a diagram showing a relationship between a video display rate and a correction magnification n in the first embodiment.

FIG. 7 is a system configuration diagram of a video display device according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a gradation expression method by a subfield method.

FIG. 9 is a system configuration diagram of an image display device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between a video display rate and a correction magnification n in the third embodiment.

FIG. 11 is a system configuration diagram of a conventional image display device.

FIG. 12 is a diagram illustrating gamma correction characteristics of a video signal.

FIG. 13 is a diagram showing gamma correction of a ramp waveform signal.

FIG. 14 is a diagram illustrating an inverse gamma correction characteristic of a video signal.

FIG. 15 is a diagram showing inverse gamma correction data.

[Explanation of symbols]

1 A / D converter, 2 inverse matrix conversion circuit, 3 inverse gamma correction circuit, 4 image adjustment circuit, 5 PDP module, 21 low luminance signal correction circuit, 22 comparison and selection circuit, 23 display ratio calculation circuit, 24 coefficient setting circuit .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/28 H04N 9/69 // H04N 9/69 G09G 3/28 K F term (reference) 5C021 PA52 PA80 PA85 RB03 XA34 YA01 5C066 AA03 CA27 EA03 EC05 EC12 GA01 KE01 KE07 5C080 AA05 BB05 CC03 DD05 DD06 EE29 HH01 JJ02 JJ04 JJ05

Claims (3)

[Claims] 1. A video display apparatus for converting a gamma-corrected video signal into a digital signal and then displaying it on a pixel-by-pixel basis in a display device, comprising an inverse gamma correction circuit for inverse gamma-correcting the gamma-corrected video signal. A low-brightness signal correction circuit that attenuates the gamma-corrected video signal and outputs a low-brightness correction signal, compares the outputs of the gamma correction circuit and the low-brightness signal correction circuit, and outputs the larger one. Video display device comprising a comparison and selection circuit for 2. The video display device according to claim 1, wherein the attenuation coefficient of the low luminance signal correction circuit is set based on the video display rate of the video signal. 3. The video display device according to claim 1, wherein the attenuation coefficient of the low-brightness signal correction circuit is set based on a set value of display brightness of the display device.