JPH0479576A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent the 'glaring' and the 'blurring' of an image from occurring by detecting the change of amplitude of the high frequency component of a video signal from which ghost is eliminated by a ghost eliminator, and adjusting the amount of amplification or that of attenuation at a picture quality correction circuit corresponding to a detection result. CONSTITUTION:A detecting means 103 detects the change of the amplification of the high frequency component of the video signal inputted to a picture quality correction means 104, for example, that of the amplification of a color burst signal included in the video signal, and outputs the detection result as a control signal. An adjusting means 106 decreases the amount of correction in the picture quality correction means 104 or increases the amount of attenuation when the amplitude of the color burst signal is increased corresponding to the control signal. Adversely, when the amplitude of the color burst signal is decreased, the amount of correction in the picture quality correction means 104 is increased or that of attenuation is decreased. In such a way, the 'glaring' or the 'blurring' of the image is prevented from occurring by performing the correction of picture quality after eliminating the ghost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing circuit used in a television receiver incorporating a ghost removal device or connected to a ghost removal device.

[Conventional technology]

In a television receiver, when a receiving antenna simultaneously receives direct waves from a broadcasting station and reflected waves from a building, etc., an unnecessary image appears on the screen, causing ghost l-interference. As a ghost removal device for removing such ghost l-interference, a reference signal for ghost removal (GCI<signal) is inserted from the broadcasting station side, and compared with the OCR signal using a transversal filter on the receiving side,
Gose 1 - The one that performs the removal is, for example, time opening ΔB 1-99
It is described in Publication No. 378.

FIG. 4 shows the body side of such a ghost removal device using a lance versal filter.

In Figure 11, 40] is the video signal input terminal, 40
2 is an A/D conversion circuit, 71 (+3 is a delay compensation circuit, 40
4 is a subtraction circuit, 405 is l)/A conversion circuit, 406
is a video output circuit, 407a to 407c are delay elements,
408a to 408c are multiplication circuits, 4(1!) is an addition circuit, 41O is a transversal filter, 41] is an OC
R is a signal extraction circuit, 4] 2 is a comparison circuit, 4]
:( is a reference signal generation circuit, and 414 is a tap gain control circuit.

Next, the operating principle of this circuit will be explained.

The radio waves (direct waves) sent from the broadcasting station include radio waves (reflected waves) from buildings, etc., and reach the receiving antenna (not shown). The received radio waves (including the Goth 1 signal) are input to the video input terminal 401 through a tuner and a detection circuit (not shown).

The input video signal is first converted into A/l) conversion times 11L.
18/l.

2, the analog signal is converted into a digital signal. Here, 1.1. for ghost removal inserted on the broadcasting station side. The quasi-signal (OCT, <signal) is also distorted due to the influence of reflected waves (including the characteristics of the intermediate transmission path). This distorted OCR signal is processed by the GCR signal extraction circuit 41.
1, the undistorted G C11<signal and comparison circuit 41 are extracted and generated from the reference waveform generation circuit 4 + 3.
2, the 1-tap gain control circuit 414 compares the output of the comparison circuit 412 with the multiplication circuits 408a to 1 of the Lance Barzal filter 410 so that the error in the received OCR multiplied signal reference waveform is minimized. Adjust the touch gain of 408c.

In this way, unnecessary reflected waves (ghost signal components) are extracted from the Calor calculation circuit 401, and the ghost is removed by subtracting the unnecessary reflected waves from the signal containing the reflected waves in the subtraction circuit 404. I can do it.

Furthermore, the digital signal is converted into an analog signal by the ]]/Δ conversion circuit 405, and a ghost-free video signal is obtained from the output terminal 40[i.

[Problems to be Solved by the Invention] Now, consider a case where a ghost removal device as shown in FIG. 4 is used and the propagation time difference between the direct wave and the reflected wave is very short (near ghost case).

FIG. 5(a) shows a case where a direct wave (solid line) and a reflected wave (dotted line) arrive with a propagation time difference Δt. This figure is an enlarged representation of the color burst signal portion and the 3.58M, Z component of the luminance signal.

When the two waves overlap in this way, the same IXI (
As shown in b), the amplitude of the color burst signal part becomes small, and the amplitude of the luminance signal near L58M, H7,
The H component also decreases. When such a signal is input to a television receiver, the automatic saturation adjustment circuit (ΔCC circuit) will keep the color density constant even if the color burst signal amplitude becomes small; ii, 58
If the components around MHz decrease, the sharpness of the image will be lost.

In order to reduce the sharpness of such signals, it is common practice to use an image quality correction circuit to amplify the high frequency components and compensate for the lost components.

However, if such image quality correction is performed after ghost removal, the high-frequency components will be further emphasized and the image will become glare, since the region around 3.58 MHv will be reproduced after ghost removal. occurred. Furthermore, depending on the propagation time difference between the direct wave and the reflected wave, if a ghost appears, the area around L5gM Hz will be emphasized, causing glare or emphasizing dot interference.

Therefore, in order to solve this problem, the signal component around 3.58 MHz is generally reduced using an image quality correction circuit.

However, if such image quality correction is performed after ghost removal, the signal components around 3.58Ml-■Z will decrease after ghost removal, and high-frequency components will be further lost, causing the image to deteriorate. A problem arose in that the images were blurred.

Here, the problem in the former case will be explained in more detail using FIGS. 6 and 7.

FIG. 6 shows a typical video signal flow when a ghost removal device is added to a television receiver.

In the figure, 601 is a video signal input terminal, 602 is a ghost removal device, 603 is a Y/C separation circuit, 604 is an image quality correction circuit, 605 is a luminance signal output terminal, 60 [j is an ACC circuit, and 607 is a color demodulation circuit. , 608, 609 are color difference signal output terminals.

Let us consider a case where ghost removal is not performed in the mass/ghost removal device 602.

The video signal is separated into a luminance signal (Y) and a chrominance signal (C) by a Y/C separation circuit 60. In addition, the color signal (C) separated by the Y/C separation circuit 6 (+3) is kept constant in color density by the ACC circuit 606. and by the color demodulation circuit 607,
It is demodulated and converted into color difference signals RY and +3-Y signals.

Here, the luminance signal whose high frequency components are emphasized by the image quality correction circuit K604 becomes as shown in FIG. 7(a).

Next, consider a case where ghost removal is performed in the ghost removal device 602.

In this case, the luminance signal whose high frequency components are emphasized by the image quality correction circuit 604 becomes as shown in FIG. 7(b).

That is, around:L58MHz or further emphasized,
11" glare appears in the image.

A first object of the present invention is to provide a video signal processing circuit that does not cause ``shaky'' or ``blur'' in an image even if image quality correction is performed after removal to Goth 1. .

[Means to solve the problem]

In order to achieve the above-mentioned object, in the present invention, Gose 1
- an image quality correction means for inputting the video signal from which the ghost has been removed by the removal device, amplifying or attenuating the high frequency components of the video signal and outputting the amplified or attenuated high frequency components in order to correct the image quality; A detection means for detecting an amplitude change in a high frequency component of a video signal and outputting the detection result as a control signal, and adjusting an amount of amplification or attenuation in the image quality correction means according to the control signal from the detection means. and an adjustment means to do so.

[Effect]

The detection means detects an amplitude change in a high frequency component of the video signal input to the image quality correction means, for example, an amplitude change in a color burst signal included in the video signal, and outputs the detection result as a control signal. .

The adjusting means decreases the amount of correction or increases the amount of attenuation in the image quality correcting means when the amplitude of the color burst signal increases in accordance with the control signal, and conversely,
When the amplitude of the color burst signal decreases, the amount of correction in the image quality correction means is increased or the amount of attenuation is decreased.

By performing image quality correction in this manner after ghost removal, it is possible to obtain optimal image quality without causing "glare" or blur.

〔Example〕

An embodiment of the present invention will be described above with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing a video signal processing circuit as an embodiment of the present invention.

In the figure, 101 is a video input terminal, 102 is a ghost l-removal device, 103 is a Y/C separation circuit, 104 is an image quality correction N path, ]05 is a luminance signal output terminal, and 106 is an AC
C circuit, ]07 is a color demodulation circuit, and 108 and 109 are color difference signal output terminals.

This circuit differs from the conventional example shown in FIG.
The feature is that the gain of the l1ili quality correction circuit 104 is controlled by control signals I) and V from [0f].

FIG. 2 shows one specific side of the image quality correction circuit 104 in FIG. 1.

In the figure, 201 is a luminance signal input terminal, 202 and 203 are delay lines, 204a to 204c are multiplication circuits, and 20
5 is an adder circuit, 206 is a variable multiplier circuit, 207 is a countable circuit, and 208 is a control signal input terminal from the ACC circuit.

In this circuit, by selecting the delay lines 202 and 203 to be 70 ns, the peak frequency can be set to approximately 3.58 MHz. By changing K from -0.5 to 1, the gain around 3.58 MHz of the luminance signal output from the Y/C separation circuit 10:3 can be adjusted from -6 dB to +6.
Can be done again up to dB.

FIG. 3 shows one specific side of the ACC circuit 106 in FIG. 1.

In the figure, 301 is a color signal input terminal, 302 is a first
303 is a second band increasing circuit; 304 is a color signal output terminal; 305 is a burst signal extraction circuit; 306
is a comparison circuit, 307 is a reference burst signal generation circuit, 30
8 and 309 are gain control circuits, and 310 is a gain control signal output terminal.

This circuit inputs the color signal output from the Y/C separation circuit [0:3] shown in FIG. 1 through an input terminal 301.

The color verse 1-signal extraction circuit 305 extracts the color verse 1 from among the color signals output from the second band amplification circuit 303.
- Extract only the signal and reference burst signal generation circuit 307
In the comparison circuit 306, the burst signal generated from
If the comparison is made and the amplitude of the colorverse 1 signal increases after ghost removal, the gain control circuit r 308 lowers the gain of the first band amplification circuit 302 to keep the color intensity constant. Further, if the amplitude of the signal to colorverse 1 decreases after ghost removal, the gain of the first band boosting circuit 302 is increased to keep the color density constant.

In addition to the original CC operation, this circuit also performs the following operations when the amplitude of the color burst signal increases after ghost removal:
The image quality correction circuit 104 adjusts the brightness signal to 3.58MHz.
In order to prevent "glare" from occurring in the image due to emphasis of nearby components, the gain control circuit 11309 functions to lower the gain of the image quality correction circuit 104.

In addition, if the amplitude of the color burst signal decreases after ghost removal, the image quality correction circuit]04
．． In order to prevent the sharpness of the image from dropping due to the loss of components around 58 MHz, the gain control circuit 309 works to increase the gain of the image quality correction circuit 104. Note that the gain control circuits I and TI can also be used in common. It is possible.

In this way, even after image quality correction is performed after ghost removal, optimal image quality without "glare" or "blur" can be obtained.

FIG. 8 shows another embodiment of the invention.

In this embodiment, in addition to the embodiment shown in FIG. 1, burst signal extraction circuit 803. Full wave rectifier circuit 804. smoothing circuit 80
5 has been added.

In this circuit, only the burst signal is extracted by the burst signal extraction circuit 803, and the full-wave rectifier circuit 804゜smoothing circuit $8
05, a control voltage proportional to the amplitude of the burst signal is obtained. This control voltage controls the gain of the image quality correction circuit]04, so after ghost removal,
When the amplitude of the color burst signal increases, the gain of the image quality correction circuit 104 is lowered, and when the amplitude of the color burst signal decreases, the gain of the image quality correction circuit 104 is lowered. In this way, the same effect as the embodiment of FIG. 1 is achieved.

〔Effect of the invention〕

According to the present invention, the ghost removal device detects the amplitude change of the high frequency component of the video signal from which the ghost has been removed, and adjusts the amplification amount or attenuation amount in the image quality correction circuit according to the detection result, so that the ghost removal device can remove the ghost. Even if the image quality is corrected after this, the optimum image quality can be obtained without causing 11'' glare or 1' blurring in the image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing one specific side of the 1lIi quality correction circuit in FIG. 1, and FIG. 3 is a block diagram showing one specific side of the ACC circuit in FIG. 1. 4 is a block diagram showing one part of a general ghost removal device, FIG. 5 is a waveform diagram showing the waveform of a video signal containing a ghost, and FIG. 6 is a conventional video signal processing circuit. FIG. 7 is a block diagram showing the image quality correction circuit shown in FIG. FIG. 8 is a waveform diagram showing a luminance signal with emphasized area components, and FIG. 8 is a block diagram showing another embodiment of the present invention. Explanation of symbols 102... Ghost removal device, 103...
・Y/C separation circuit, 104...image quality correction circuit,
106...A(, C circuit, 803...Burst signal extraction circuit, 804...Full wave rectifier circuit,
805...Smoothing circuit. fan

Claims (1)

[Claims] 1. In a video signal processing circuit used in a television receiver incorporating a ghost removal device or connected to a ghost removal device, a video signal from which ghosts have been removed by the ghost removal device is inputted. , in order to correct the image quality, an image quality correction means for amplifying or attenuating and outputting a high frequency component of the video signal; detecting a vibration change in the high frequency component of the video signal input to the image quality correction means; An image comprising: a detection means for outputting the detection result as a control signal; and an adjustment means for adjusting the amount of amplification or attenuation in the image quality correction means according to the control signal from the detection means. signal processing circuit. 2. The video signal processing circuit according to claim 1, wherein the detection means is configured from an automatic saturation adjustment circuit that inputs the video signal from which ghosts have been removed by the ghost removal device, performs saturation adjustment, and outputs the video signal. A video signal processing circuit characterized in that the detection output signal obtained by the automatic saturation adjustment circuit is output as the control signal. 3. The video signal processing circuit according to claim 1, wherein the detection means inputs the video signal from which ghosts have been removed by the ghost removal device, extracts and outputs a color burst signal included in the video signal. a full-wave rectifier circuit that full-wave rectifies the color burst signal from the color burst signal extractor circuit and outputs the full-wave rectifier; A video signal processing circuit comprising: a smoothing circuit for outputting.