KR100652268B1 - Dynamic contrast adjustment method - Google Patents

Abstract

A dynamic contrast control method is provided to control black and white stretches according to the brightness level of an input image signal. When an image signal is inputted(S10), a brightness level calculating member calculates the brightness level of the image signal(S20). The calculated brightness level is inputted to a control member. The control member compares the brightness level with the set level(S30) and controls the brightness level through the black and white stretching processes according to the size of the brightness level. When the brightness level is above the set level, the white stretch is increased to the maximum white value according to the values changed by steps(S40).

Description

Dynamic contrast adjustment method

1 is a block diagram of a dynamic contrast adjusting device according to the present invention;

2 is a flowchart illustrating a dynamic contrast adjusting method according to the present invention.

3 illustrates the black / white stretch operating range of FIG.

<Explanation of symbols for main parts of the drawings>

10: contrast adjustment unit 20: LCD panel

30: luminance level calculator 40: control unit

50: dimming processing unit 60: inverter

70: backlight

The present invention relates to a method for setting a contrast ratio of an LCD, and more particularly, to a contrast adjustment method for adjusting contrast by adjusting black stretch and white stretch according to a level of brightness of an input video signal. .

In high information society, research on display device technology for displaying information is being actively conducted. Information transmission will be mainstream of a system that simultaneously sends and receives text, voice and video. The basic functions of the display device required by the system should have characteristics of human-centered, environmental-oriented, advanced, and highly functionalized. In this era, research on flat panel display devices is actively underway in Korea.

Display devices are classified into a cathode ray tube device and a flat panel display device. Currently, the liquid crystal display device (hereinafter referred to as 'LCD') of the flat panel display field has formed the most amazing results and plasma display panel (PDP) displays the ease of large screen and CRT level image quality Research is also actively underway.

Flat panel display devices have lower power consumption, higher resolution, thinner and lighter weight than CRT, and adopt digital driving method. The advantages of this digital processing method are noise, and as the number of bits increases, the range of numerical values that can be expressed increases, so that arithmetic processing or accumulation with less degradation can be achieved and high image quality can be realized. Therefore, it is necessary to study the digital signal processing technique for the image displayed on the flat panel display device. Among them, image processing methods for image quality improvement include contrast adjustment, noise reduction, edge restoration, edge enhancement, and gamma correction. Among them, the image quality can be improved without additional information by using the coat adjustment.

Contrast ratio is a value obtained by dividing a bright screen brightness by a dark screen brightness. Since a light screen is lighter than a dark screen, a dark screen is made darker.

That is, if the bright screen is "550cd / m ² ", the dark screen should be close to "0". Therefore, the backlight brightness is adjusted by adjusting the dimming value, but the dimming value is also limited.

In addition, in order to extend the contrast ratio, the same black stretch value was set on any screen, and the white stretch value was unconditionally set and stretched, which makes it difficult to reproduce the natural screen as a whole. There was a problem with the output.

Disclosure of Invention The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a contrast adjustment method that allows contrast adjustment by adjusting black stretch and white stretch according to levels of luminance of an input video signal. have.

Another object of the present invention is to output a natural screen as a whole by adjusting the contrast according to the brightness level.

The configuration of the present invention devised to achieve the above object is as follows. According to an aspect of the present invention, in the contrast adjustment method of an LCD panel, when an image signal is input, a first step of calculating a brightness level of the video signal, a second step of comparing the calculated brightness level with a preset setting level, and white stretch And setting the maximum value and the minimum value of the black stretch, and setting the gradient according to the step change value and the step change value between the maximum value and the minimum value, and the white maximum value and the minimum value according to whether the luminance level is above or below the set level, and And a third step of adjusting the contrast by extending the white stretch or the black stretch to the slope according to the step change value within the range of the black maximum value and the minimum value.

Here, the white maximum value and the minimum value, and the black maximum value and the minimum value are set differently according to the video signal.

On the other hand, when the luminance level is higher than or equal to the set level, the white stretch is increased to the white maximum value, and the black stretch is reduced to the black minimum value.

If the luminance level is less than the set level, the white stretch is reduced to the white minimum value according to the screen area, the black stretch is increased to the black maximum value, and if the luminance level is less than the set level, the dimming value is controlled to improve the backlight brightness. It further comprises reducing.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

1 is a block diagram of a dynamic contrast adjusting apparatus according to the present invention, FIG. 2 is a flowchart illustrating a dynamic contrast adjusting method according to the present invention, and FIG. 3 is a diagram illustrating a black / white stretch operation range of FIG. 2.

As shown in FIG. 1, the dynamic contrast adjusting device according to the present invention adjusts the contrast of an input video signal and outputs it to the LCD panel 20 to calculate the brightness level of the input video signal. The luminance level calculator 30, the dimming processor 50 for adjusting the dimming of the backlight, and the inverter 60 controlling the DC power supplied from the power supply source according to the dimming control signal from the dimming processor 50 to supply the backlight. And the brightness level of the video signal inputted from the brightness level calculating section 30, the brightness level is compared with the preset setting level, and the brightness is adjusted through the contrast adjusting unit 10 according to whether the brightness level is equal to or greater than the setting level. It consists of the control part 40 which adjusts a level.

For reference, the inverter 60 adopts a brightness adjusting method such as analog dimming, PWM dimming, or a hybrid method of analog dimming and PWM dimming.

In particular, in order to make the bright screen brighter and the dark screen darker, the control unit 40 according to the input video signal, as shown in FIG. 3, a black stretch coefficient value, for example, a black maximum value and a black minimum value, and In addition to setting the step change value from the black maximum value to the black minimum value and the slope according to the above step change value, the white stretch coefficient value, for example, the white maximum value and the white minimum value, and the white minimum value to the white maximum value Set the step change value and the slope of.

Accordingly, the controller 40 adjusts the black stretch and the white stretch according to the black stretch coefficient value and the white stretch coefficient value set according to the input video signal, and the luminance of the video signal input from the brightness level calculator 30 is obtained. When the level is calculated, this luminance level is compared with the set level, and if the luminance level for each screen area is equal to or greater than the set level, the white stretch is elongated for each screen area, that is, the white stretch step by step within the range of the white minimum value and the white maximum value. Stretch according to the change value.

On the other hand, when the luminance level for each screen area is less than the set level, the black stretch is elongated, i.e., increased according to the step change value within the range of the black maximum value and the black minimum value. In addition, the brightness of the backlight 70 is reduced by controlling the dimming processor 50.

Such a contrast adjustment method using the contrast adjustment device according to the present invention will be described in detail with reference to FIGS. 2 and 3.

In the contrast adjustment method according to the present invention, first, it is determined whether the video signal is input, and when the video signal is input (S10), the brightness level calculator 30 calculates the brightness level of the video signal (S20).

The calculated luminance level is input to the controller 40, and the controller 40 compares the luminance level with the setting level (S30) and adjusts the luminance level through black stretching and white stretching processes according to the magnitude of the luminance level. do.

Here, if the luminance level is greater than or equal to the set level for each screen area, the white stretch is increased to the white maximum value according to the step change value (S40). On the other hand, if the luminance level is less than the set level, the black stretch is gradually changed to the black maximum value. Increasing according to the value (S50), and also performs the dimming control to lower the brightness of the backlight 70 to enlarge the contrast ratio.

As such, when the contrast ratio is enlarged through the black stretch, the white stretch, and the dimming control, the screen is displayed by outputting it to the LCD panel 20.

The present invention is not limited to the above-described embodiments and can be carried out in various modifications within the scope of the technical idea of the present invention.

According to the present invention configured as described above, the contrast can be adjusted by adjusting the black stretch and the white stretch according to the level of the luminance of the input video signal, thereby increasing the contrast ratio and reproducing the natural screen as a whole. .

Claims (5)

In the contrast adjustment method of the LCD panel, Calculating a brightness level of the video signal when the video signal is input; A second step of comparing the calculated luminance level with a preset setting level; The maximum value and the minimum value of the white stretch and the black stretch are set, and the step change value between the maximum value and the minimum value and the slope according to the step change value are set so that the white light is changed according to whether the luminance level is above or below the set level. And a third step of adjusting the contrast by extending the white stretch or the black stretch to a slope according to the step change value within a range between the maximum value and the minimum value and the black maximum value and the minimum value. How to adjust the dynamic contrast. The method of claim 1, wherein the white maximum value and the minimum value and the black maximum value and the minimum value are set differently according to the video signal. The dynamic contrast of claim 2, wherein when the luminance level is equal to or greater than the set level, the white stretch is increased to the white maximum value according to the screen area, and the black stretch is reduced to the minimum black value. Adjustment method. The dynamic contrast adjustment according to claim 2, wherein when the luminance level is less than the set level, the white stretch is reduced to the white minimum value according to the screen area, and the black stretch is increased to the black maximum value. Way. 5. The method of claim 4, further comprising controlling a dimming value to lower backlight brightness if the brightness level is less than the set level.

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