KR100638912B1 - Image signal processing device and method - Google Patents

Abstract

An image processing method of an image display apparatus according to the present invention includes checking a characteristic of an input image signal and repositioning luminance of an image signal of a low luminance part according to the characteristic of the checked image signal. It is characterized by consisting of the processing step.

In addition, the image processing method of the image display apparatus according to the present invention includes the steps of checking the characteristics of the input image signal, and if the checked image signal is a mixture of low, medium and high luminance, the video signal And removing the low luminance part of the control unit and performing a HE (HISSTO EQUALIZATION) process of rearranging the luminance of the low luminance part of the image signal if the checked image signal is mainly composed of low luminance. .

The image processing apparatus of the video display device checks the characteristics of the DAC for converting the input video signal into the digital video signal, and the characteristics of the video signal outputted from the DAC. And a gamma processing unit for gamma processing the output of the video signal processing unit, and a video signal processing unit for HE (HISSTO EQUALIZATION) processing to rearrange luminance of the video signal.

Particularly, if the checked video signal is a mixed video of low, medium, and high luminance, the video signal processor removes a low luminance portion of the video signal, and the checked video signal is mainly composed of low luminance. In case of an image, HE processing is performed to rearrange luminance of a low luminance part of the video signal.

Video signal, HE

Description

Image signal processing device and method {METHOD AND APPARATUS OF PROCESSING VIDEO SIGNAL}

1 is a conceptual diagram of a conventional video signal processing method.

2 (a) to (c) is a conceptual diagram of a video signal processing method according to a preferred embodiment of the present invention.

3 is a block diagram of a video signal processing apparatus according to a preferred embodiment of the present invention.

4 is a flowchart of a video signal processing method according to a preferred embodiment of the present invention.

5 (a) and 5 (b) are diagrams showing examples of setting black levels according to a preferred embodiment of the present invention.

6 is a diagram illustrating a signal processing process according to a preferred embodiment of the present invention.

7 shows an example of processing according to a general HE.

Explanation of symbols on the main parts of the drawings

100: first DAC

102: second DAC

104: image signal processing unit

106: HE

108: DISP_CSC offset

110: LUT

112: gamma processing unit

The present invention relates to an image display device, and more particularly, to an image signal processing apparatus and method of an image display device.

With the development of technology, image display apparatuses capable of displaying high quality images are being developed one after another.

A conventional video signal processing method applied to the video display device will be described with reference to FIG. 1.

FIG. 1 is a diagram schematically illustrating a method of improving contrast ratio for a dark image.

Conventional image display apparatuses clip out the low light of the image signal to clearly display a dark image. For example, the portion of the video signal corresponding to the lower 16 gray scales of the 255 gray scales represented by 8 bits is removed.

As the dark portion of the image signal is removed as described above, the contrast ratio between the middle and low levels is adjusted as in Equation 1, and thus the sharpness of the image having a somewhat dark image mixed on an extremely dark background can be improved.

As described above, the conventional method of removing dark portions of a video signal has a problem in that it cannot be reproduced normally for an image having a large number of the removed dark portions.

In addition, there is a problem in that it is difficult to reproduce gradations for an image having luminance close to the removed dark portion.

Further, according to the conventional method, since the luminance of the image signal is lower than the original while the color of the image signal is the same as the original, the lower the luminance of the image signal is, the more the color concentration becomes, and thus an unnatural image is reproduced.

Accordingly, an object of the present invention is to provide a video signal processing method and apparatus which enables a video display device to display a high quality image.

Another object of the present invention is to provide an image signal processing method and apparatus which can improve the contrast ratio of a dark image, and also improve the reproduction of gradations and color concentrations.

An image processing method of an image display apparatus according to the present invention for achieving the above object, the step of checking the characteristics of the input image signal, the image of the low, medium and high luminance of the checked image signal is mixed Removing a low luminance portion from the input image signal; and performing a HE (HISSTO EQUALIZATION) process of rearranging the luminance of the low luminance portion of the image signal when the checked image signal is mainly composed of low luminance. It is composed of the features.

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The image processing apparatus of the video display device checks the characteristics of the DAC for converting the input video signal into the digital video signal, and the characteristics of the video signal output from the DAC, and the checked video signal has low / medium / high luminance. Is a mixed image, the low luminance portion of the image signal is removed, and if the checked image signal is mainly composed of low luminance image, the HE process image to relocate the luminance for the low luminance portion of the image signal And a gamma processor configured to gamma-process the output of the image signal processor.

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According to the present invention, the image display device can improve the contrast ratio of a dark image, and can also display a high quality image by improving the reproduction of the grayscale and the color density.

A method of adjusting the brightness of an image signal according to an exemplary embodiment of the present invention will be schematically described with reference to FIG. 2.

According to the present invention, an optimal image can be reproduced according to an image characteristic by processing an image signal differently according to an image characteristic.

Fig. 2A shows the luminance of the video signal which has not been subjected to any further processing.

The present invention checks whether an input image is an image in which low, medium, and high luminance components are evenly mixed, or an image mainly composed of low luminance components.

As a result, if the image is an image in which low, medium and high luminance components are evenly mixed, the low luminance component is removed and the remaining components are maintained as shown in FIG.

In contrast, if the image is mainly composed of low luminance components, HE (HISSTO EQUALIZATION) is performed on the low luminance components as shown in FIG.

The HE will be further described with reference to FIG. 7.

The HE is configured to reduce the expression range of the image when the input image level is unilaterally distributed to either low luminance, medium luminance, or high luminance, so that an image having a low contrast ratio is output. When inputted, rearrangement is performed by averaging over the entire area from a probabilistic point of view, thereby increasing the contrast ratio in a display device having the same brightness.

According to the HE, the image biased at low luminance as shown in (a) of FIG. 7 is rearranged such that the luminance difference of the low luminance portion is sharp and the luminance difference of the high luminance portion is flat as shown in FIG. As shown in (c) of FIG. 7, the image that is biased with high luminance is rearranged such that the luminance difference of the high luminance portion becomes sharp and the luminance difference of the low luminance portion becomes flat as shown in FIG. 7 (d).

As such, the contrast improvement effect of the HE processing on the image having the low luminance component may be expressed by Equation 2.

Such a configuration of an image signal processing apparatus according to an exemplary embodiment of the present invention will be described with reference to FIG.

The first ADC 100 of the image signal processing apparatus receives a PC or DTV signal and converts the same into a digital image signal. The second ADC 102 receives the CVBS signal and converts it into a digital video signal. The digital image signals output by the first and second ADCs 100 and 102 are input to the image signal processor 104.

The video signal processor 104 receives the digital video signal, detects the characteristics of the digital video signal, and adjusts and outputs the luminance according to the detected characteristics of the digital video signal.

The video signal whose luminance is adjusted is provided to the gamma processing unit 112, and the gamma processing unit 112 gamma-processes the video signal provided by the video signal processing unit 104 and outputs it.

In particular, the video signal adjusting unit 104 will be described in more detail.

The video signal processing unit 104 includes a HE 106 for HE processing, a DISP_CSC offset 108 for adjusting an offset of an input video signal, and a LUT (LOOK UP TABLE) 110 for adjusting a video signal. It is composed.

The value of the LUT 110 of the image signal processor 104 is as shown in Equation 3.

As described above, the value of the LUT 100 is adjusted to have a luminance value for HE processing at a low level.

The HE register value of the video signal processor 104 is as shown in Equation (4).

In addition, the register value of the gamma processing unit 112 has a value of 2.5 to 2.2 to improve the brightness of the middle and high luminance region.

On the other hand, in order to improve the black gradation by the HE 106, the image signal processing unit 104 sets an appropriate black level for each source, which will be described with reference to FIG.

Referring to (a) and (b) of FIG. 5, B1 higher than a clamping level of 7.5 [IRE] is set as a black level only for NTSC signals, and the remaining PAL / SECAM, COMPONENT, RGB-DTV, and RGB-PC are set. In this case, the clamping level B0 is set as the black level.

By performing this black level setting before the gamma adjustment, an image consistent with various signals is output.

Now, a video signal processing method according to a preferred embodiment of the present invention will be described with reference to FIG.

The video signal processor 104 checks the characteristics of the input video signal (step 200). In other words, it is checked whether the inputted output signal is an image in which low, medium, and high luminance are mixed, or an image mainly composed of low luminance.

If the video signal is a mixture of low, medium, and high luminance, the video signal processor 104 removes only the low luminance portion of the video signal and changes the remaining video signal as shown in FIG. Do not give. This improves the contrast ratio between low and medium brightness.

If the video signal is an image mainly composed of low luminance, the video signal processing unit 104 processes only the low luminance portion of the video signal as shown in FIG. This HE processing consists of changing the curve of the LUT table and adjusting the HE register and gamma register.

In this manner, the HE processing of the low luminance part of the video signal can improve the black gradation.

Now, the improved state according to the present invention described above will be described with reference to FIG.

In Figure 6, the signal of the first method is for the entire signal of the old Korean model RN-52SZ10H, the signal of the second method is for the entire signal of the new Korean model RN-52SZ30H, and the signal of the third method is This is due to the improved RT-52SZ30RP for Australia.

The ADC Y-Offset shown in the first item indicates the level for clamping. The signals of the first and second methods are all 16, but are 0 or 3 levels of the signals of the third method. Since the level of clamping is small in this way, black gradation is sufficiently displayed.

The HE-Lmin shown in the second item indicates the minimum level of the video signal to be cut off. The signals of the first and second methods are both -16, but are 0, -8 and -3 in the third method. Since the level to be cut off is small in this way, a sufficient black gradation is displayed.

In the Disp-CSC offset shown in the third item, -16 is selected in the first and second schemes and 0 is selected in the third scheme.

The LUT shown in item 4 is the brightness offset based on OSD 50. The signal of the first method is 0 (Y = aX), the signal of the second method is 31/4 (Y = aX-31). The three-way signal is 0 (Y = aX).

The Y Total Offset shown in the fifth item is the total Y Offset from the ADC to before gamma, the signal of the first method is -16, the signal of the second method is -24, and the signal of the third method is 0, -8,0. to be.

The gamma shown in the sixth item is 2.5, which displays an image of which the signal of the first method is relatively indistinct, 2.2 of which displays an image of the image that is relatively floating, and that of the second method, which is relatively dissipative. It is 2.5 to display.

As described above, the first and second methods can be set to a black level suitable for 7.5 IRE, but low level 16 gradations are removed for the remaining sources. The removal of the low level 16 gradations reduces the color density balance between the low and high levels, making the color concentration darker, and when the dark color concentration is adjusted to an appropriate level, the high level color density becomes lighter.

In particular, in the first method, since the black level is more removed, the darkest image of the lowest level is buried even if the gamma coefficient is increased to 2.5.

However, according to the present invention, since the black level is set by mapping the clamping level to 0, the black gradation is good on the basis of the gamma 2.5 setting criterion, and the black level is also good.

As described above, the present invention has the advantage that the image display device can improve the contrast ratio of the dark image and can also display a high quality image by improving the expression performance of the gray scale and the color density.

Claims (5)

In the image processing method of a video display device, Checking a characteristic of an input video signal; Removing the low luminance part from the input image signal when the checked image signal is a mixture of low, medium, and high luminances; And, And if the checked video signal is mainly composed of low luminance, performing a HE (HISSTO EQUALIZATION) process to rearrange the luminance of the low luminance portion of the image signal. delete In the image processing apparatus of the image display device, A DAC converting an input video signal into a digital video signal; Check the characteristics of the video signal output from the DAC, and if the checked video signal is a mixture of low, medium and high luminance, the low luminance portion is removed, and if the image is mainly composed of low luminance, the input image An image signal processor for processing HE (HISSTO EQUALIZATION) for rearranging the luminance of the low luminance part of the signal; And, And a gamma processing unit configured to gamma-process the output of the image signal processing unit. delete The image signal processing unit of claim 3, wherein the image signal processing unit An HE unit for HE-processing the video signal; An offset adjusting unit for adjusting an offset of the video signal; And a LUT having a table for HE processing of the video signal.

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