JPH0678178A - Image quality adjustment circuit - Google Patents

Abstract

(57) [Summary] [Purpose] The optimum image quality is obtained by faithfully adjusting the image quality of the TV screen according to the image content and automatically in accordance with the human viewpoint. [Structure] A high-frequency component is extracted from a video signal output from an edge enhancement (image quality adjustment) circuit 1 by a filter 3, and a weighting circuit 11 weights the high-frequency component from the center of the screen. The weighted high frequency component is converted into a DC voltage by the detector 4, and the average luminance level detecting means 15
Between the average brightness level obtained by
6 is used to perform an operation to obtain the image quality control voltage as the operation result, and this is applied to the control terminal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image quality adjustment of a television receiver screen, and more specifically, to automatically adjust the degree of contour enhancement of a picture on the screen according to the content of the video signal (picture). The present invention relates to an image quality adjustment circuit for improving image quality.

[0002]

2. Description of the Related Art Generally, the image quality of a television screen can be manually adjusted, and an appropriate image quality can be obtained by adjusting the image quality each time according to the image content (picture). However, it is actually difficult to manually adjust the image quality according to the changing image content, and the image quality adjustment is rarely performed in a general use state.

Therefore, a method of automatically adjusting the image quality according to the image content can be considered. As described in Japanese Patent Laid-Open No. 60-153268, a high frequency component in an input image signal is detected as a signal representing the image content. There is known a method of automatically adjusting the image quality by applying a control voltage according to the detected voltage to an image quality control terminal of an image quality adjustment circuit (specifically, an edge enhancement circuit).

FIG. 9 is a block diagram showing an example of such a conventional image quality adjusting circuit. In the figure, 1 is an edge enhancement circuit, 2 is an image quality control terminal, and 6 is a high frequency component detection circuit. That is, the high frequency component in the input video signal of the contour emphasizing circuit 1 is detected by the high frequency component detecting circuit 6 as an image content, and a control voltage corresponding to the detected voltage is applied to the image quality control terminal 2 of the contour emphasizing circuit 1. The image quality is automatically adjusted by adding it.

[0005]

However, the above-mentioned prior art has some problems as follows. First, the high-frequency component is detected not as from the output side of the contour emphasizing circuit but from the video signal on the input side as a representation of the video content. In some cases, the frequency band of the image actually displayed on the screen may not be correlated, and in such a case, the optimum image quality cannot be obtained.

That is, there is a difference between the image signal on the input side and the image signal on the output side of the contour emphasizing circuit, whether the image quality adjustment (contour emphasizing) is performed or not, and the image signal on the input side is Compared to the video signal on the output side, the image quality is not adjusted, so that the correlation with the image actually displayed on the screen is weak, so there are cases where the correlation cannot be obtained.

Secondly, the high frequency component is detected uniformly over the entire screen of the television screen and the image quality is controlled according to the detection level. For example, the example of the television screen shown in FIG. 7 is shown. As described above, in the case of an image in which high-frequency components are concentrated in the peripheral portion of the screen (in FIG. 7, the hatched portion is the portion where high-frequency components exist), the average amount of high-frequency components is one screen average. Since many of them operate so as to reduce the image quality, the human's viewpoint is often located in the center of the screen, so that the image is felt to be too low in image quality (that is, the outline portion is blurred).

On the contrary, when the high frequency component is concentrated in the central part of the screen and the high frequency component is small in the peripheral part as seen in the television screen example of FIG. 8, the amount of the high frequency component of one screen average is Since the number is small, the image quality is improved, but for the same reason, the image quality may be perceived as being too high.

Thirdly, the detected high frequency component has not only the information of the frequency component but also the information of the amplitude (though only the information of the frequency component causes no problem).
For example, in the case of a video signal having a low average luminance level, the detected voltage is low because the luminance level is low (the amplitude is small) even if the amount of high frequency components is large.

Therefore, in the case of a video content having a low average luminance level, the image quality is uniformly increased, and the video quality becomes too high. On the contrary, when the average brightness level is high, the detection voltage becomes high even if the amount of the high frequency component is small, and the image quality may be lowered evenly by operating to uniformly reduce the image quality.

An object of the present invention is to provide an image quality adjusting circuit which can solve the above-mentioned problems of the prior art.

[0012]

The present invention uses the following means in order to solve the above problems. That is, with respect to the first problem, the detection of the high frequency component is performed from the image signal whose image quality is adjusted (the image signal which is the output signal of the contour emphasis circuit). As a result, the high-frequency component of the actually displayed image content and the high-frequency component to be detected are reliably correlated, and the optimum image quality can always be obtained.

Regarding the second problem, when the high frequency component of the video signal is detected, the information in the central portion of the screen (the high frequency component detected from the central portion of the screen) is weighted according to the human viewpoint. To do. That is, the high frequency component of the peripheral part of the screen and the high frequency component of the central part are detected separately, and are amplified by amplifiers of different gains, respectively, and the high frequency component of the central part is compared with the gain of the amplifier for amplifying the high frequency component of the peripheral part of the screen The gain of the amplifier that amplifies is increased.

Thereafter, these two high-frequency components are added, the addition result is converted into a DC voltage by a detection circuit, and a control voltage corresponding to the detection voltage is added to a contour emphasis circuit (image quality adjustment circuit).
To the image quality control terminal of. By using this method, it is possible to detect the high-frequency component in which the center portion of the screen is weighted, that is, it is possible to detect the high-frequency component according to the human viewpoint, and it is possible to obtain the optimum image quality without causing the second problem. .

The third problem is that the average luminance level is detected from the input video signal or the video signal after image quality adjustment, and the average brightness level is calculated with the separately detected high frequency component (for example, the detected high frequency component). Is divided by the detected average brightness level to obtain a high-frequency component that is not related to the average brightness level (amplitude), and the control voltage applied to the image quality control pin is purely high frequency regardless of the average brightness level. Make the value related only to the component. Accordingly, the image quality control according to only the high frequency component can be performed instead of the image quality control according to the two information of the high frequency component and the average luminance level, and therefore the third problem does not occur.

[0016]

With the first means for solving the first problem, it is possible to always obtain an appropriate image quality in accordance with the displayed video content. Further, by the second means for solving the second problem, even in the case of a screen in which high frequency components are concentrated in the peripheral portion of the screen as shown in the screen example of FIG. 7,
Even if the high-frequency component is concentrated in the central portion as in the screen example of FIG. 8, on the contrary, it is possible to eliminate the glare of the image due to the excessive increase in the image quality without causing the blurring of the outline due to the excessive decrease in the image quality. .

By the third means for solving the third problem, it is possible to obtain an optimum image quality which is substantially unrelated to the average luminance level and purely related to the high frequency component. It is possible to prevent the image quality at the time of brightness from rising too much and the image quality at the time of high brightness to fall too much. That is, it is possible to obtain the optimum image quality for any video content.

[0018]

1 is a block diagram showing a first embodiment of the present invention. In the figure, 1 is an edge enhancement circuit, 2 is an image quality control terminal, 3 is a detection filter, 4 is a wave detector, 5 is a DC inversion amplification circuit, and 6 is a high frequency component detection circuit. That is,
A high frequency component detection circuit 6 for detecting a high frequency component is provided at the subsequent stage of the contour enhancement circuit 1, and the detected voltage is supplied to the image quality control terminal 2
Add to. The high frequency component detection circuit 6 is composed of the detection filter 3 and the wave detector 4.

Next, the operation of the first embodiment shown in FIG. 1 will be described. A high-frequency component is detected by the detection filter 3 from the image signal whose image quality has been adjusted, which is the output signal of the contour emphasizing circuit 1, and the detector 4 obtains a DC voltage according to the amount of the high-frequency component. The DC inverting amplifier circuit 5 lowers this when there are many high-frequency components, raises it when there are few high-frequency components, and converts it into a voltage that matches the variable range of the contour emphasis circuit 1 and applies it to the image quality adjustment terminal 2.

By this circuit operation, when there are few high frequency components, the image quality is improved and the contour portion is made clear. On the other hand, when there are many high frequency components, the image quality is lowered to make the contour portion inconspicuous and the image quality is softened. Therefore, it is possible to obtain an easily viewable image quality according to the video content. Unlike the conventional example shown in FIG. 9, the present embodiment detects the high frequency component from the image signal whose image quality has been adjusted, so that the image quality adjustment that is reliably correlated with the actually displayed image content can be performed. it can.

FIG. 2 is a block diagram showing a second embodiment of the present invention. In the embodiment shown in the figure, a weighting circuit 11 is added between the detection filter 3 and the detector 4 in the first embodiment shown in FIG.

The weighting circuit 11 comprises a screen center extraction circuit 7, a peripheral extraction circuit 9, amplifiers 8 and 10 having different gains, and an adder 18. Further, a sync separation circuit 1 for separating and extracting a horizontal sync signal and a vertical sync signal from an input video signal in order to cut out a central portion or a peripheral portion of a screen as a target of the extracting operation.
A sampling unit 14 including a sampling signal generator circuit 2 for generating a sampling signal based on the synchronization signal is provided.

The operation of the second embodiment will be described with reference to FIG. The high frequency component detected by the detection filter 3 is
The sampling circuits 7 and 9 divide the screen information into information in the central portion of the screen and information in the peripheral portion of the screen. After that, the gains of the amplifiers 8 and 10 having different gains are added and added by the adder 18.
If the gain is larger than 0, that is, the amplification gain of the information in the central portion of the screen is large, it is possible to detect the high frequency component by placing weight on the central portion of the screen.

In the sampling operation, the sampling signal generating circuit obtains a sampling pulse synchronized with the central portion of the screen based on the horizontal and vertical synchronizing signals obtained by the sync separation circuit 12, and based on this, the sampling pulse of the central portion of the screen is obtained. Pull out,
The polarity of this pulse is inverted by the inverter 17, and the peripheral portion of the screen is extracted. By the above operation, the image quality control is performed with weighting on the information in the central portion of the screen, so that an easy-to-see image quality without unnaturalness can be obtained for all the video contents.

FIG. 3 is a block diagram showing a third embodiment of the present invention. In this embodiment, the high frequency component in the second embodiment of FIG. 2 is detected from the input video signal (not the output video signal), and the operation is the second embodiment of FIG. It is almost the same as, but it is effective when it is desired to control the image quality more faithfully to the input video signal than to the display content.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention. This embodiment is the same as the first embodiment of FIG.
A means 15 for detecting the average brightness level (APL) is provided,
An arithmetic circuit 16 performs an arithmetic operation between the voltage detected by the high frequency component detecting circuit 6 and the voltage detected by the average luminance level (APL) detecting means 15 to be applied to the image quality control terminal 2. Is.

The operation of the fourth embodiment shown in FIG. 4 will be described. From the input video signal, the average luminance level detection voltage detected by the average luminance level detection means 15 and the high frequency component detection voltage detected by the high frequency component detection circuit 6 are passed through the arithmetic circuit 16 to the high frequency component and the average luminance level. A DC voltage corresponding to the above two information is obtained, and this is applied to the image quality control terminal 2.

The contents of the arithmetic operation of the arithmetic circuit 16 are as follows.
Division can be mentioned as an example. That is, the detected high frequency component is divided by the detected average brightness level,
A high frequency component that does not relate to the average brightness level (amplitude) is obtained. This will be described below.

The output of the high frequency component output from the detector 4 depends not only purely on the high frequency component but also on the level of the video signal targeted for the detection of the high frequency component. If the level of the video signal is high, a high output can be obtained. Therefore, regardless of whether the level of the video signal is high or low, there is a case where it is desired to obtain an output that depends purely on the high frequency component and apply the output to the image quality control terminal 2 regardless of the level.

In such a case, the high frequency component detected by the high frequency component detection circuit 6 is converted into the average brightness level (A
(PL) It is possible to obtain a high-frequency component that is not related to the average brightness level (amplitude) by dividing by the average brightness level detected by the detection means 15. Therefore, the arithmetic circuit 16 is caused to perform division. In this way, the optimum image quality can be obtained by incorporating the amount of high frequency components of the image and the average brightness level.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention. This embodiment is a combination of the second embodiment shown in FIG. 2 and the fourth embodiment shown in FIG. 4, and is used to control the image quality in terms of the amount of high frequency components, the average brightness level, and the human viewpoint. It can be done according to the information in the center of a screen.

FIG. 6 is a block diagram showing a sixth embodiment of the present invention. This embodiment is obtained by adding an average brightness level detecting means 15 and an arithmetic circuit 16 to the third embodiment of FIG. 3, and the operation and effect are almost the same as those of the fifth embodiment, This is effective when you want to control the image quality more faithfully to the input video signal than the display content on the screen.

In the fourth, fifth, and sixth embodiments shown in FIGS. 4, 5, and 6, the image quality-adjusted video signal (video signal which is the output signal of the contour emphasis circuit) is averaged. It is obvious that the same effect can be obtained by detecting the brightness level.

[0034]

As described above, the effects of the present invention are listed below. The first is
Since the high frequency component can be detected faithfully to the video content displayed on the screen, the optimum image quality can be obtained for the displayed video content.

Secondly, since the high frequency component can be detected by weighting the information in the central portion of the screen, which is the human's viewpoint in many cases, it is possible to detect the human appearance for all the video contents. That is, it is possible to obtain an easy-to-see image quality without unnaturalness.

Thirdly, the optimum image quality can be obtained by performing the calculation between the amount of high frequency components and the average brightness level, by incorporating two pieces of information of the amount of high frequency components and the average brightness level.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing a sixth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an example of an image in which high-frequency components are concentrated on the peripheral portion of the screen.

FIG. 8 is an explanatory diagram showing an example of an image in which high-frequency components are concentrated in the center of the screen.

FIG. 9 is a block diagram showing a conventional example of an image quality adjustment circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Edge enhancement circuit, 2 ... Image quality control terminal, 3 ... Detection filter, 4 ... Detector, 5 ... DC inversion amplification circuit, 6 ... High frequency component detection circuit, 7 ... Screen center extraction circuit 8 ... Screen center amplification circuit , 9 ... Screen peripheral extraction circuit, 10 ... Screen peripheral amplification circuit, 11 ... Weighting circuit, 12 ... Sync separation circuit, 13 ... Extraction signal generation circuit, 14 ... Extraction unit, 15
... average brightness level detection circuit, 16 ... arithmetic circuit, 17 ... inverter, 18 ... adder

Claims (6)

[Claims] 1. A contour emphasizing circuit for emphasizing and outputting a contour portion of a pattern of an input video signal, and high frequency component detecting means for detecting a high frequency component from a video signal which is an output signal of the contour emphasizing circuit. A control voltage generating means for generating an image quality control voltage according to the magnitude of the high frequency component, and a negative feedback control by applying the image quality control voltage to the control terminal of the contour emphasis circuit to adjust the image quality according to the image content. An image quality adjustment circuit comprising: a control unit that automatically adjusts and controls. 2. The image quality adjusting circuit according to claim 1, wherein the control voltage generating means detects the high frequency component depending on which position on the screen the detected position of the detected high frequency component belongs. An image quality adjusting circuit comprising means for weighting a value and creating an image quality control voltage according to the weighted value. 3. A contour emphasizing circuit for emphasizing and outputting a contour portion of a pattern of an input video signal, high frequency component detecting means for detecting a high frequency component from the input video signal which is an input signal of the contour emphasizing circuit, and detection. A control voltage generating means for generating an image quality control voltage according to the magnitude of the generated high frequency component, and the image quality control voltage is added to the control terminal of the contour emphasis circuit to automatically adjust the image quality according to the image content. In the image quality adjusting circuit, the control voltage creating means determines the detected value of the high frequency component depending on which position on the screen the detected position of the detected high frequency component belongs. An image quality adjusting circuit comprising means for performing weighting and creating an image quality control voltage according to the weighted size. 4. A contour emphasizing circuit for emphasizing and outputting a contour portion of a pattern of an input video signal, high frequency component detecting means for detecting a high frequency component from a video signal which is an output signal of the contour emphasizing circuit, and the contour emphasizing circuit. A calculation is performed between a brightness level detecting means for detecting an average brightness level on the screen from a video signal which is an input signal or an output signal of the circuit, and a detection output by the high frequency component detecting means and a detection output by the brightness level detecting means. A control voltage generating means for generating an image quality control voltage and a negative feedback control by applying the image quality control voltage to the control terminal of the contour emphasis circuit to automatically adjust and control the image quality according to the image content. And an image quality adjusting circuit comprising: 5. A contour emphasizing circuit for emphasizing and outputting a contour portion of a pattern of an input video signal, and a detection position of the detected high frequency component when a high frequency component is detected from the video signal output from the contour emphasizing circuit. A high-frequency component weighting detection means for weighting the detected value of the high-frequency component depending on which position on the screen belongs and outputting the weighted value; and an input signal of the contour enhancement circuit. Alternatively, a calculation is performed between a brightness level detecting means for detecting an average brightness level on the screen from a video signal which is an output signal, a detection output by the high frequency component weighting detecting means and a detection output by the brightness level detecting means. Depending on the video content, a control voltage generating means for generating an image quality control voltage and a negative feedback control by applying the image quality control voltage to the control terminal of the contour emphasis circuit are applied. Image quality adjustment circuit, wherein automatically adjusting image quality, and control means for controlling, in that it consists. 6. A contour emphasizing circuit for emphasizing and outputting a contour portion of a pattern of an input video signal, and detecting a high frequency component detected when a high frequency component is detected from a video signal which is an input signal of the contour emphasizing circuit. High frequency component weighting detection means for weighting the detected value of the high frequency component depending on which position the screen belongs to and outputting the weighted value; and an input to the contour emphasis circuit. A brightness level detection means for detecting an average brightness level on the screen from a video signal which is a signal or an output signal, and a detection output by the high frequency component weighting detection means and a detection output by the brightness level detection means are operated. A control voltage generating means for generating an image quality control voltage by applying the image quality control voltage to the control terminal of the contour emphasis circuit to automatically adjust the image quality according to the image content. Adjustment, the image quality adjustment circuit, wherein the control means for controlling, in that it consists.