JP2798169B2 - Image display method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video signal processing and image display technology in a display system such as a television, and more particularly, to a PDP (Plasma Display Pan).
el) and LCD (Liquid Crystal Di)
The present invention relates to an image display method and an image display method for increasing the brightness of an image displayed on a display (spray).

[0002]

2. Description of the Related Art PDPs and LCDs are capable of full-color display and high-speed gradation display. In particular, PDPs are excellent in a large screen among flat displays, and are thin, large-screen color display devices (for example, wall-mounted televisions). LCDs are being used in projection televisions.

In the above display, for example, in the case of a television screen display (natural image display) or the like, it is possible to adjust each intensity (luminance level) of an input digital video signal (R, G, B signal) to obtain a so-called white balance. Very important.

For example, as shown in the display luminance characteristic diagram of FIG. 5, in a PDP, green (G) is strong and red (R) and blue (B) are weak, that is, the luminance level of the G signal is different from that of other R signals and Red (R) is weaker in a projection type LCD which is higher than the B signal and uses a metal halide lamp.

In this case, with respect to the dotted line portion in FIG. 5, the luminance levels of green (G) and red (R) are reduced in accordance with the weak color (B) to achieve white balance. That is, other G signals and B signals are adjusted in accordance with the G signal having a low luminance level.
This is because it is difficult to increase the luminance level of the signal.

[0006]

In the above-mentioned color PDP and projection type LCD, for example, it is not possible to obtain sufficient brightness for a color television display, and each of the primary colors (R, G, B) has a maximum brightness. , The white balance tends to shift to the green (G) color side. When the white balance is shifted to the green side, the primary color (G) having a large luminance is reduced to achieve the white balance. In particular, the green (G) color greatly contributes to the brightness of the display image. For this reason, there is a problem that the brightness of the display image becomes further insufficient, and for example, a dark image becomes darker. That is, it is difficult to balance brightness and white balance.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an image display method and an image display method capable of suppressing a decrease in luminance of a display image and achieving a beautiful white balance of flesh color. It is in.

[0008]

In order to attain the above object, an image display method and apparatus according to the present invention provide a method and apparatus for displaying an image based on an input video signal at least on a PDP or a liquid crystal display panel. Detecting the presence or absence of a flesh color portion of the display image, and detecting the brightness of the display image, taking a white balance of the display image according to the detected information on the presence or absence of the flesh color and the brightness, and adjusting the display image of the display panel. The gist of the present invention is to suppress the decrease in luminance.

[0009]

According to the above means, when the display image has a flesh color portion and the display image is bright or the display image is dark, the display image has no flesh color portion and the display image is bright or the display image is dark. In the dark case, the range of the input video signal level for white balance is changed.

When the average luminance level of the display image is low and there is no flesh-colored part, or when there is a flesh-colored part but it is dark, white balance is achieved below the level lower than the ratio of the input video signal. When the average luminance level of the display image is high and there is no flesh color portion, white balance is obtained at a relatively high level or less of the input video signal. Further, when the average brightness level of the display image is high (the display image is bright) and there is a flesh color portion, white balance is achieved below the brightness of the flesh color portion. Furthermore, when the average luminance level of the display image is low (the display image is dark) and there is a flesh color portion, white balance is achieved below the brightness of the flesh color portion.

Therefore, the brightness of the displayed image can be suppressed, and a beautiful white balance of skin color can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display method and apparatus according to the present invention
For color television images, etc., it is required to clearly display the skin color, which is a memory color, and the allowable value of the white balance shift, at which image quality is deteriorated for other colors, is much larger than the skin color. (R, G, B
Signal) to detect the presence or absence of a flesh color portion of the display image, detect the brightness of the display image, and change the range of the input digital video signal level that balances white below the flesh color portion according to the luminance of the flesh color portion. .

Therefore, as shown in FIG. 1, the image display device of the present invention is, for example, a PDP (Plasma Display Panel) for displaying an image based on an input digital video signal.
1, a flesh-color detecting unit 2 for detecting the presence or absence of a flesh-color portion of the display image and a brightness detecting unit 3 for detecting the brightness (luminance level) of the display image, based on the digital video signal; Operation control means 4 for calculating data for gamma correction (γ correction) of the input digital video signal based on the information of the input digital video signal, reading of gamma correction data using the input digital video signal (for example, 8 bits) as an address, And rewritable γ-RAM
(Storage means) 5 and a multiplexer section 6 for switching input and output to output the calculated gamma correction data to the γ-RAM 5 and output the data read from the γ-RAM 5 to the PDP 1. ing.

Although not shown, the image display device according to the present invention uses the data output from the multiplexer unit 6 (data read from the γ-RAM 5) to generate
A controller for driving the DP1 and a control circuit for controlling each circuit of the device are provided. Further, in the image display device having the above configuration, the case of the PDP 1 has been described, but the same configuration may be applied to an LCD.

Next, the operation of the image display apparatus having the above configuration and the operation of the image display method will be described with reference to the display luminance characteristic diagrams of FIGS. It is assumed that the display luminance characteristics for the input digital video signal before white balance is obtained are as shown in FIG. 5 (assuming appropriate gamma correction). In FIGS. 2 to 4, it is assumed that a white balance is obtained when the relative values (on the drawings) of the vertical axis (luminance level) match.

First, according to the input digital video signal,
The skin color detecting unit 2 detects whether or not the display image of the PDP 1 has a skin color portion, and the brightness detecting unit 3 detects the brightness (luminance level) of the display image.

The arithmetic unit 4 having input the information on the presence or absence and the brightness of the flesh-color portion, the gamma correction data corresponding to the average brightness level of the display image and, if the flesh-color portion exists, the brightness level of the flesh-color portion. Is calculated.

For example, when the average luminance level of the display image is low and there is no flesh color portion, or when there is a flesh color portion but it is dark, as shown in FIG. Calculate gamma correction data for balancing. In other words, at 100% of the input digital video signal, the white balance is adjusted to a brighter one within a range where the deviation from the white balance is hardly perceived.

When the average luminance level of the display image is high (the display image is bright) and there is no flesh color portion, as shown in FIG. 3, a gamma for achieving a white balance below a relatively high level of the input digital video signal. Calculate the correction data. In this case, it is assumed that the skin color portion is not higher than the high level.

When the average brightness level of the display image is high (the display image is bright) and there is a flesh color portion, as shown by an arrow a in FIG. 4, a gamma is set such that a white balance is obtained below the brightness of the flesh color portion. Calculate the correction data.

When the average luminance level of the display image is low (the display image is dark) and there is a flesh color portion, as shown by an arrow b in FIG. 4, a gamma is obtained such that a white balance is obtained below the brightness of the flesh color portion. Calculate the correction data.

That is, in general, the brightness of the flesh color portion of the display image is 90% or less, and the example shown in FIGS. 2 to 4 can correspond to the input digital video signal.

By the way, since there are various kinds of display images by the input digital video signal, the calculation is extremely effective for calculating the gamma correction data. The calculated gamma correction data is written to the γ-RAM 5 via the multiplexer 6.

Then, data is read from the γ-RAM 5 by the input digital video signal, and this data is input to the PDP 1 through the multiplexer 6 and
Each light emitting element of DP1 is driven.

As a result, according to the display luminance characteristic of FIG. 2, a screen having a large contrast ratio can be obtained even for a dark display image. According to the display luminance characteristic of FIG.
Shading of a bright display image can be made finer, and according to the display luminance characteristics of FIG. 4, a bright flesh color portion of the display image can be made more clear.

As described above, the presence or absence of a flesh color portion, which is a memory color of a display image, is detected based on the input digital video signals (R, G, B signals), and the brightness of the display image is detected. The range of the input digital video signal level for white balance is the luminance of the skin color part (or the luminance of the entire display image when there is no skin color part; average luminance)
In other words, the data of the gamma correction is changed, and the colors (for example, R and B) having a low luminance level are raised without lowering the color (G) having a high luminance level so that a white balance below a flesh color portion is obtained. I have.

Therefore, for example, when the display image is dark, a screen having a large contrast ratio can be obtained. In addition, the deviation from the white balance in the bright portion of the display image is small on the screen, which causes no problem. Can be refined. In addition, when the display image has a flesh color portion, the flesh color can be made clear, and even if the flesh color portion does not exist, a decrease in luminance due to white balance can be suppressed when the display image is extremely bright. That is, colors with low luminance levels (for example, R and B) are raised without lowering colors (G) with high luminance levels.

[0028]

As described above, according to the image display method and apparatus of the present invention, the presence or absence of a skin color portion, which is a memory color of a display image, is detected by an input digital video signal (R, G, B signals). At the same time, the brightness of the display image is detected, and the white balance of the display image on the display panel is adjusted according to the information on the presence / absence of the detected skin color and the brightness. Can achieve a beautiful white balance, specifically, when the display image is dark, a screen with a large contrast ratio can be obtained, and the deviation from the white balance in the bright part of the display image can be reduced on the screen. On a bright screen, the shadows can be finely detailed, and if the displayed image has a flesh-colored part, the flesh-color can also be made clearer. Without the parts, it is possible to suppress the reduction in luminance due if the white balance is displayed images extremely bright.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an image display device showing one embodiment of the present invention.

FIG. 2 is a schematic display luminance characteristic diagram for explaining the operation of the image display device shown in FIG. 1 and the operation of the image display method.

FIG. 3 is a schematic display luminance characteristic diagram for explaining the operation of the image display device shown in FIG. 1 and the operation of the image display method.

FIG. 4 is a schematic display luminance characteristic diagram for explaining the operation of the image display device shown in FIG. 1 and the operation of the image display method.

FIG. 5 is a schematic display luminance characteristic diagram for explaining a conventional image display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PDP (plasma display panel) 2 Skin color detection part 3 Brightness detection part 4 Operation part 5 γ-RAM (storage means) 6 Multiplexer part

Claims (3)

(57) [Claims] 1. An image display method for obtaining a white balance of a display image when displaying an image based on an input video signal on at least a PDP or a liquid crystal display panel, wherein the presence or absence of a flesh color portion of the display image is detected by the input video signal. And an image display method for detecting the brightness of the display image and suppressing a decrease in the brightness of the display image on the display panel according to the information on the presence or absence of the detected skin color and the brightness. 2. An image display method for obtaining a white balance of a display image when displaying an image based on an input video signal on at least a PDP or a liquid crystal display panel, comprising: detecting an average video level based on the input video signal; Detecting the presence or absence of a flesh-color part, detecting the brightness of the flesh-color part, changing the range of the input video signal level that balances the white according to the detected average video level and the flesh-color brightness, An image display method, wherein a white balance is obtained. 3. An image display device which gamma-corrects an input digital video signal when displaying an image based on the input digital video signal on at least a PDP or a liquid crystal display panel, and drives the display panel based on the gamma-corrected signal. A storage unit that enables rewriting of the gamma correction data; a skin color detection unit that detects presence or absence of a skin color portion of a display image based on the input digital video signal; and a brightness of a display image based on the input video signal. Brightness detection means, and inputs the presence / absence signal of the skin color portion and the brightness signal, calculates the gamma correction data according to the brightness of the display image and the brightness of the skin color portion, and calculates the calculated data. And an arithmetic control means for making the storage means rewritable by the input digital video signal. The image display apparatus the gamma corrected by the step data, based on the gamma correction signal to drive the display panel, is characterized in that so as to suppress the reduction in luminance of the display image of the display panel.