JP2615510B2 - Noise removal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise eliminator used for improving the S / N of a video signal of a video reproducing apparatus such as a video disk player.

[0002]

2. Description of the Related Art In recent years, there has been a demand for higher image quality of devices handling video signals such as video discs and VTRs, and there has been a growing demand for noise removal techniques for improving S / N.

In particular, in a video disk player, a reproduced video signal contains intermodulation noise of an audio FM signal, and therefore, a noise removing device is indispensable for removing this noise.

[0004] As a conventional noise elimination device, an optical disk and a video disk (Shokodo, edited by The Television Society,
pp. 53-54) ".

Hereinafter, a conventional noise removing device will be described. FIG. 4 is a block diagram showing the configuration of the conventional noise removing device. In FIG. 4, a video signal is input to a noise removal circuit 10 including a band-pass filter 11, a limiter 12, and a subtractor 13. The video signal in this case is a composite signal including a chrominance carrier. By the way, the sound F
It contains the intermodulation component of the M signal, and its frequency is about 2.5 MHz. Therefore, a signal near this frequency is extracted by the band pass filter 11. Next, the signal is passed by the limiter only when the level of the signal is small, and the output is subtracted from the original signal. As a result, only signals having a low level among signals near 2.5 MHz included in the video signal are removed, so that noise can be removed without deteriorating image quality. At this time, not only the noise due to the intermodulation but also the disk noise near 2.5 MHz and the noise of the laser pickup are removed at the same time.
Is improved.

In addition, as a video signal output, a component signal output is required in addition to a composite signal. Therefore, the video signal from which noise has been removed is separated by the YC separation circuit 14 into a luminance signal and a carrier chrominance signal and output.

[0007]

However, it is difficult to effectively improve the S / N of the chrominance signal in the above-mentioned conventional configuration. The reason will be described below. Since the chrominance signal is processed as a carrier chrominance signal, its center frequency is N
In the case of a TSC signal, it is 3.58 MHz. Therefore, in the conventional configuration, the center pass band of the band-pass filter 11 is set to 3.
Must be 58MHz. However, in such a configuration, the output of the band-pass filter 11 is the carrier chrominance signal itself, and this signal is passed through a limiter circuit to pass through the subtractor 13.
When subtracting from the original signal, the light color is canceled and disappears, so that it cannot be adopted as a noise removing device.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a noise eliminator capable of eliminating noise of a carrier color signal.

[0009]

SUMMARY OF THE INVENTION In order to solve this object, a noise elimination apparatus according to the present invention employs a characteristic of an input video signal .
A first noise removing circuit for removing noise in a certain band;
A YC separation circuit using a comb filter for separating the output into a carrier chrominance signal and a luminance signal, and a second noise for removing noise in a carrier chrominance signal band of the luminance signal obtained by the separation by the YC separation circuit A removing circuit; and an adding circuit for adding the output of the carrier color signal obtained by separation by the YC separating circuit and the output of the second noise removing circuit.

[0010]

According to the present invention, noise in the carrier chrominance signal band of the carrier chrominance signal band of the luminance signal output from the YC separation circuit using the comb filter is eliminated by the above-described configuration, and this luminance signal and the YC separation circuit By adding the carrier chrominance signals separated by the above, a chrominance signal with improved S / N is obtained.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a noise removing apparatus according to the present embodiment .
FIG. 9 is a block diagram illustrating a configuration around a second noise removal circuit .

The video signal including the carrier chrominance signal is separated into a luminance signal 8 and a carrier chrominance signal 9 by a YC separation circuit 2 using a comb filter. The luminance signal 8 is sent to a noise removing circuit 3 composed of a band-pass filter 4, a limiter 5, and a subtractor 6, and its output is added to a carrier chrominance signal 9 by an adding circuit 7 and output as a composite signal.

In the noise removing circuit 3, a signal in the color signal band of the input luminance signal 8 is extracted by the band pass filter 4. Next, the signal is passed by the limiter circuit 5 only when the level of the signal is low, and is subtracted from the input signal.
As a result, a signal with a small level is removed as a signal within the color signal band of the input signal as an output signal, and a signal with improved S / N is obtained.

The above operation will be described in more detail with reference to FIG. FIG. 3 illustrates the spectrum of a video signal including a carrier color signal using two-dimensional frequencies. FIG.
(A) shows the spectrum of the luminance signal 8 and the carrier chrominance signal 9 separated by the YC separation circuit 2. The horizontal axis represents the horizontal frequency, and the vertical axis represents the vertical frequency. Since the noise removal circuit 3 described above removes noise in the horizontal carrier chrominance signal band out of the "luminance signal" shown in FIG. 3A, noise in the frequency domain indicated by oblique lines is removed. become.
That is, the hatched portion represents the frequency region of the “luminance signal from which noise has been removed” among the luminance signals.

Therefore, in the composite signal obtained at the output of the adder circuit 7, the noise of the signal in the frequency domain indicated by oblique lines in the entire band is reduced.

Next, the S / N of the color signal when this composite signal is viewed on a television monitor is shown in FIG.
This will be described with reference to FIG. In many monitors, a band-pass filter is used to separate a carrier chrominance signal and a luminance signal. When the carrier chrominance signal and the luminance signal are separated by the bandpass filter, they are separated into a “luminance signal” and a “carrier chrominance signal extracted by the bandpass filter” as shown in FIG. As can be seen from this figure, in this case, the “noise-removed luminance signal” area indicated by oblique lines is processed as a carrier chrominance signal. Therefore, according to the configuration of the present invention, the S / N of this area is
Are improved, the color signal S / N on the monitor is improved.

As described above, in the second noise elimination circuit ,
The noise of the luminance signal output is removed using a YC separation circuit.
Therefore , the S / N of the color signal on the monitor can be improved.

It is not always necessary to set the pass band of the band-pass filter 4 only to the color signal band. Therefore, by expanding the band to the frequency where the interference by the cross modulation exists, the cross modulation can be removed at the same time.

FIG. 2 is a block diagram of a noise removing apparatus according to the present embodiment . In this embodiment, the second noise shown in FIG.
The first noise elimination circuit is added to the elimination circuit and its peripheral circuits , and the respective configurations are the same.

In a laser disc player, an audio signal is FM-modulated and recorded on a disc while also being superimposed on an FM-modulated video signal. Therefore, interference due to cross modulation appears in a reproduced signal. Specifically, this disturbance is about 2.5 MHz
with a frequency of z. Therefore, first, the noise removal circuit 10
Remove this interference. Next, as shown in FIG.
The same circuit is used to remove noise in the color signal band. According to this configuration, both interference due to cross modulation and noise due to other causes can be effectively removed, so that a large image quality improvement effect can be obtained.

[0022]

As described above, according to the present invention, the S / N of the color signal can be improved by combining the YC separation circuit 2 using the comb filter and the noise removal circuit 3 used for outputting the luminance signal. it can.

Further, according to the present invention, by providing another noise elimination circuit 10 in the input stage , cross-modulation elimination and S / N
Both improvements can be made effectively.

[Brief description of the drawings]

The noise removal device according to an embodiment of the present invention; FIG
FIG. 2 is a block diagram showing a configuration around a noise removal circuit of FIG.

Block diagram showing the configuration of a noise removing apparatus according to an embodiment of the present invention; FIG.

FIG. 3 is a characteristic diagram showing a two-dimensional frequency characteristic of a video signal according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional noise removing device.

[Explanation of symbols]

 2 YC separation circuit 3, 10 Noise removal circuit 4, 11 Bandpass filter 5, 12 Limiter 6, 13 Subtractor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Inoue 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-2833387 (JP, A) JP-A-63-133788 (JP, A)

Claims (3)

(57) [Claims] A first noise removal circuit for removing noise in a specific band of an input video signal; a YC separation circuit using a comb filter for separating the output of the input video signal into a carrier chrominance signal and a luminance signal; A second noise removal circuit for removing noise in a carrier chrominance signal band of the luminance signal obtained by separation by the YC separation circuit; a carrier chrominance signal output obtained by separation by the YC separation circuit; And an addition circuit for adding the output of the noise removal circuit. 2. A first noise removing circuit comprising: a first band-pass filter for extracting a signal of a specific band of an input signal; a first limiter circuit for passing the signal only when its output is small; The noise eliminator according to claim 1 , comprising a first subtractor for subtracting an output of the first limiter circuit. A second band-pass filter for extracting a signal of a carrier color signal band of the input signal; a second limiter circuit for passing the signal only when the output is small; claim 1 is constituted by a second subtractor for subtracting an output of said second limiter circuit from Symbol
On-board noise eliminator.