JPH057314A - Noise reduction device for television receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a noise eliminator that compensates for deterioration in response of a video signal and improves image quality. A video signal 24 from a tuner 23 is separated by a Y / C separation circuit 25 into a luminance signal 26 and a color difference signal 27, the luminance signal 26 is subjected to contour enhancement processing by a contour enhancement circuit 29, and further, a slicer circuit 31 and a limiter. The circuit 32 corrects to a predetermined signal level from which noise components have been removed, and a corrected contour emphasis signal 33 is obtained. In the adder 35, the luminance signal 26 is LP
The band-limited signal 34 is combined in F28, and the Y / C mixer 38 combines the combined signal 36 and the signal obtained by delaying the color difference signal 27 by the delay line 37 to output the noise-removed video signal 39. In the selection switch 40, the signal 3
9. Either the video signal 24 or the video signal 24 is selected according to the noise detection output 44 obtained by passing the detection signal 41 from the tuner 23 through the noise amount detection circuit 43 to obtain a video signal output 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise removing device for improving the SN ratio in a television receiver such as a satellite broadcast receiver.

[0002]

2. Description of the Related Art In satellite broadcasting reception, the reception level is lowered due to rain attenuation and the like, so that the CN (carrier noise) ratio is deteriorated and the SN of a demodulated video signal is reduced.
The (signal / noise) ratio also deteriorates. As a device for improving such an SN ratio, a device as shown in FIG. 5 is conventionally known.

In FIG. 5, 1 is an antenna, 2 is a received signal, 3 is a tuner, 4 is a video signal, 5 is a detection output, 6 is an HPF, 7 is a noise amount detection circuit, 8 is a variable LPF, and 9 is a noise amount. A detection signal, 10 is an SN ratio improvement signal, 11 is a selection switch, and 12 is a video output signal.

In the conventional apparatus, the reception signal 2 from the antenna 1 is input to the tuner 3, the detection output 5 from the tuner 3 is passed through the HPF 6, the noise component is extracted, and then the noise amount detection circuit 7 is supplied. , Detection output 5 to noise amount 9
To detect. Noise amount signal 9 detected by the detection circuit 7
And the video signal 4 from the tuner 3 are applied to the variable LPF 8, the band of the video signal 4 is made variable according to the amount of noise, and the band is limited, thereby outputting the signal 10 with an improved SN ratio.

The selector switch 1 selects the SN ratio improving signal 10 and the video signal 4 directly output from the tuner 3.
In addition to 1, either of the signals 4 and 10 is selected depending on the magnitude of the noise amount 9 from the noise amount detection circuit 7.
That is, when the noise amount exceeds a predetermined value, the SN ratio improvement signal 10 is selected.

FIG. 6 shows a video signal 4 having a reduced SN ratio,
It shows a comparison with the SN ratio improvement signal 10, and the video signal 4
The noise component 13 superimposed on is limited by passing through the LPF 8 and is not seen in the SN ratio improving signal 10 which is a band-limited video signal.

[0007]

However, the rise time t ₁ of the video signal 4 is reduced due to the deterioration of the response of the video signal.
The rising time t ₂ of the SN ratio improvement signal 10 becomes longer than that of the above. As a result, there is a problem that the outline of the image is blurred.

An object of the present invention is to provide a noise eliminator which compensates for the deterioration of the response of the video signal and improves the image quality.

[0009]

In order to achieve such an object, the present invention includes a video demodulation means for detecting and demodulating a reception signal and outputting a detection signal and a video signal, and a video demodulation means included in the detection signal. Noise detecting means for extracting a noise component to be output and outputting a detection signal corresponding to the noise amount, extracting means for extracting a luminance component signal and a color component signal from the video signal, and inputting this luminance component signal, a luminance component signal A contour processing signal that has undergone contour enhancement processing, and the contour processing signal that corrects this contour processing signal to a predetermined signal level from which noise components have been removed and outputs a corrected contour processing signal; and a luminance component signal that is predetermined. Luminance component correcting means for obtaining a corrected luminance component signal by synthesizing with the corrected contour processing signal limited to the frequency band, and chrominance signal delayed by a predetermined correction time and synthesized with the corrected luminance component signal. Synthesizing means for outputting's removal video signal, that consists characterized.

[0010]

The luminance component signal and the color component signal are extracted from the video signal demodulated from the received signal. A contour processing signal obtained by processing the luminance component signal with a plurality of delay signals delayed for different predetermined times so as to enhance the contour is obtained, and a corrected contour processing signal in which a noise component is removed from the contour processing signal is output. The luminance component signal is limited to a predetermined frequency band and then combined with the corrected contour processing signal to obtain a contour-enhanced corrected luminance component signal. The color component signal is delayed by the correction time, combined with the corrected luminance component signal, and a noise-removed video signal is output.

[0011]

Embodiments of the present invention shown in the drawings will be described below.

FIG. 1 shows the configuration of an embodiment of a noise removing apparatus according to the present invention, in which 21 is an antenna, 22 is a received signal, 23 is a tuner as a video demodulating means, 24 is a video signal, and 25 is a luminance / luminance. Y / C separation circuit as color component extracting means, 26 a luminance signal, 27 a color difference signal, 28 LP
F and 29 are contour emphasis circuits as contour emphasis processing means, 3
0 is a contour emphasis signal, 31 is a slicer circuit, 32 is a limiter circuit, 33 is a corrected contour emphasis signal, 34 is a band-limited luminance signal, 35 is an adder, 36 is a corrected luminance signal, 37 is a delay line, 38 is luminance / Y / as a color component synthesizing means
C mixer, 39 is an SN ratio improvement signal, 40 is a selection switch, 41 is a detection signal, 42 is a noise component BPF, 43 is a noise detection circuit, 44 is a noise detection output, 45 is a video signal output, and 46 is an SN ratio improvement device. Indicates. The LPF 28 and the adder 35 constitute a luminance component correction means.

In such a configuration, the received signal 22 received by the antenna 21 is FM demodulated by the tuner 23 and a video signal 24 is output. The video signal 24 is supplied to the Y / C separation circuit 25 and the selection switch 4 of the SN ratio improving device 46.
Enter 0. In the Y / C separation circuit 25, the luminance signal 26
And the color difference signal 27, and the luminance signal 26 is
8 and the contour emphasis circuit 29.

FIG. 2 shows an example of a concrete configuration of the contour emphasizing circuit 29. Reference numerals 50, 51 and 52 denote luminance signals Y ₁ , Y ₂ and Y ₃ , 53 and 54 are delay lines for one horizontal scanning period, and 55 and 56 are subtractors, 57 and 58 are contour signals YA and YB, 59 is an adder, and 30 is a contour enhancement signal YC.

FIG. 3 shows the waveform of each part of FIG.
(A), (b) and (c) are luminance signals Y ₁ ,
Waveform of Y ₂ and Y _3, (d) and (e) respectively contour signal YA is (= Y ₂ -Y ₁₎ and the waveform of _{YB (= Y 2 -Y 3)} , (f) the contour enhancement signal YC ( = YA + YB).

The operation of FIG. 2 will be described below with reference to FIG. By passing the luminance signal from the Y / C separation circuit 25 of FIG. 1 through the delay lines 53 and 54, the luminance signal of FIG.
Three types of luminance signals 5 as shown in (b) and (c)
0, 51 and 52 are output, and those outputs are applied to the subtracter 5
5 and 56, the luminance signal 50 is subtracted from the luminance signal 51 to output the contour signal 57 shown in FIG. 3D, and the luminance signal 52 is subtracted from the luminance signal 51.
The contour signal 58 shown in (e) is output. These contour signals 57 and 58 can be added by the adder 59 to obtain the contour emphasis signal 30.

Next, in FIG. 1, the contour emphasizing signal 30 is input to the limiter circuit 32 via the slicer circuit 31.

FIG. 4 is a diagram showing the operating principle of the slicer circuit 31 and the limiter circuit 32. Reference numerals 60 and 61 respectively denote limiter levels and slicer levels of the contour enhancement signal 30, 62 denotes noise components, and 63 and 64 respectively +. Voltage levels and-voltage levels are shown.

As shown in FIG. 4, the contour emphasis signal 30 includes a noise component 62. In order to remove this noise component, the + voltage level 63 and the −voltage which are not affected by the noise component 62 are included. The slicer level 61 is set as the lower limit level for each of the levels 64, and the slicer circuit 31 clips the slicer level 61.

Further, the + voltage level 6 of the contour emphasis signal 30
3 or-If the voltage level 64 is too large,
Since there is a visual disturbance, an upper limit is set for each of the + voltage level 63 and the − voltage level 64, and the limiter level 6 is set.
It is set to 0 and is clipped by the limiter circuit 32.

As a result, the corrected contour emphasis signal 33 has no noise and becomes a signal having a constant voltage level or less. This corrected contour emphasis signal 33 is supplied to the LPF 28 in the adder 35.
Then, it is combined with the luminance signal 34 whose band has been limited in step S3, and the corrected luminance signal 36 is output.

Further, the color difference signal 27 delayed by the correction time by the delay line 37 and the corrected luminance signal 36 from the adder 35 are combined by the Y / C mixer 38, and the SN ratio improving signal 39 is sent to the selection switch 40. input. The signal band of the detection signal output from the tuner 23 is about 6M.
Hz, and all components above 6 MHz become noise. This noise is triangular noise peculiar to FM, whose spectrum increases as the frequency increases. This detected signal 41 is
After a noise component of 6 MHz or higher is generated by the noise component BPF 42, envelope detection is performed by the noise amount detection circuit 43 and converted to a DC level to obtain a noise detection output 44.

When the noise level of the noise detection output 44 is high, the selection switch 40 selects the SN ratio improving signal 39, and when the noise level is low, the video output directly from the tuner 23. It operates so as to select the signal 24 and outputs it as a video signal output 45.

In the above embodiment, the luminance signal 26
The fixed LPF 28 used for band limitation is used, but a variable LPF can also be used.

[0025]

As described above, according to the noise removing device for a TV receiver of the present invention, contour enhancement is performed to compensate for the deterioration of response, so that the contour of the image is not blurred. , The image quality can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a noise removing device according to the present invention.

FIG. 2 is a diagram showing an example of a specific configuration of the contour emphasis circuit of FIG.

FIG. 3 is a diagram showing a waveform of each part of FIG.

FIG. 4 is a diagram showing an operation principle of the slicer circuit and the limiter circuit of FIG. 1.

FIG. 5 is a configuration diagram of a conventional noise removal device.

FIG. 6 is a diagram for explaining the operation of FIG.

[Explanation of symbols]

23 Tuner 24 video signals 25 Y / C separation circuit 26 Luminance signal 27 Color difference signal 29 contour enhancement circuit 31 slicer circuit 32 limiter circuit 33 Corrected contour enhancement signal 39 SN ratio improvement signal 40 selection switch 44 Noise detection output

Claims (3)

[Claims] 1. A video demodulating means for detecting and demodulating a received signal from an antenna to output a detected signal and a video signal, and a noise component included in the detected signal is extracted to obtain a detection signal corresponding to the noise amount. Noise detecting means for outputting, a luminance component signal from the video signal, an extracting means for extracting a color component signal, and the luminance component signal is input, and the contour processing signal obtained by subjecting the luminance component signal to contour enhancement processing is obtained, Contour enhancement processing means for correcting the contour processing signal to a predetermined signal level from which the noise component has been removed and outputting a corrected contour processing signal; and the corrected contour processing signal for limiting the luminance component signal to a predetermined frequency band. And a luminance component correction means for obtaining a corrected luminance component signal, and the color component signal delayed by a predetermined correction time to be synthesized with the corrected luminance component signal to output a noise-removed video signal. A noise removing device for a television receiver, comprising: luminance / color component synthesizing means. 2. A selection means for selecting and outputting one of the noise-removed video signal and the video signal from the video demodulation means in accordance with a detection signal from the noise detection means. Item 1. A noise removing device for a television receiver according to Item 1. 3. The contour enhancement processing means includes a slicer circuit that sets a slicer level as a lower limit level of the contour processed signal, and a limiter circuit that sets a limiter level as an upper limit level thereof. The noise removing device for a television receiver according to claim 1.