JPS5816384B2 - video - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for removing noise components mixed into a video signal.

2. Description of the Related Art Conventionally, a device shown in FIG. 1 has been considered as a video signal noise removal device used in a video tape recorder.

That is, in FIG. 1, 1 is a playback video head;
2 is a head amplifier, 3 is a limiter, 14 is an FM demodulation circuit, 5 is a de-emphasis circuit, 6 is a high frequency or wave circuit, 7 is a limiter, 18 is a polarity inversion circuit, 9 is a volume for adjusting the mixing level, 10 is a mixing 11 is a video output amplifier, and 12 is a video output terminal.

In this configuration, the steps from the video head 1 to the FM demodulator 4 use a general FM demodulation method, so a description thereof will be omitted.

Since the demodulated playback video signal has high frequency components emphasized by pre-emphasis during recording, it is passed through the de-emphasis circuit 5 and converted to the original video signal waveform, and the signal a shown in Fig. 2 is output. be done.

Next, this signal a is applied to the high frequency wave circuit 6 to extract the combination of noise and the high frequency component (FIG. 2b) in the video signal.

The extracted signal C is passed through a limiter I to limit the amplitude of the upper and lower parts of the high frequency signal near the maximum level of noise, and a signal C is extracted.

Next, the waveform C is applied to the polarity inverting circuit 8 to obtain a signal d with the polarity of the signal inverted.

When this polarity-inverted signal d and the reproduced video signal a are combined in the mixing circuit 10, the noise of the reproduced signal a and the noise of the high-frequency signal d are in opposite phases to each other, so the noise is canceled out, and the output is A video signal e from which noise has been removed will be extracted.

Note that the mixing level of the signals d and a can be varied by the level adjustment volume 9 so that the noise in the output signal is minimized.

The video signal from which noise has been removed is amplified by an output amplifier 11 and applied from a terminal 12 to a monitor receiver or the like.

However, in this configuration, the level corresponding to the limiter level of the signal C whose amplitude is limited by the limiter T does not contain a noise component, so as shown in the signal e, the rising or falling portion of the video signal is There is a problem that the noise cannot be removed.

The present invention eliminates this drawback, and one embodiment thereof will be described below with reference to the drawings.

In FIG. 3, each block numbered 1 to 5 is the same as in FIG. A mixing circuit, 16 is a second high-frequency wave circuit, 17 is a polarity inversion circuit, 18 is a mixing level adjustment volume, 19 is a second mixing circuit, 11 is a video output amplifier, and 12 is a video output terminal. be.

This operation will be explained by comparing it with the waveforms shown in FIG.

Since the steps up to the de-emphasis circuit 5 are the same as in FIG. 1, their explanation will be omitted.

The de-emphasis circuit 5 receives a signal f similar to that shown in FIG.
is played back and output.

A part of this reproduced video signal f is sent to the first high-frequency r-wave circuit 13.
is applied to extract the high-frequency component g in the video signal containing noise.

A signal g is obtained by passing this signal g through a slice circuit 14.

Further, a part of the reproduced signal f from the de-emphasis circuit 5 is applied to a second high-frequency f-wave circuit 16 to extract a high-frequency video signal i containing noise components.

This high-frequency video signal i is applied to a polarity inversion circuit 1T to obtain a phase-inverted signal j.

A first mixing circuit 15 synthesizes the high frequency signal from which the low level has been sliced and noise has been removed and the high frequency signal j.

Since the high-frequency signals j and h have opposite phases to each other, the high-frequency signal components cancel each other out, and only the noise component is extracted as an output.

When the first mixing circuit 15 performs signal synthesis, the noise contained in the rising and falling parts of the high-frequency signal also cancel each other out, so the high-frequency r-wave circuit 13 is configured so that the inverted signal j side contains more noise. We need to choose a constant of .16.

That is, the first high-frequency f-wave circuit 13 has lower pass characteristics on the high-frequency side compared to the second high-frequency filter circuit 16, and the band P
Make it have wave-like characteristics.

For example, the passband of the second high ayasawa wave circuit 16 is set to 500K.
H, the passband of the first high-frequency wave circuit 13 is 500KH or more, but the characteristic is that it is sequentially attenuated compared to the second high-frequency wave circuit 16 at 2"z or more. It is good to say.

A second mixing circuit 19 combines the output signal of the first mixing circuit 15 and the reproduced video signal f.

Since the noise component of the reproduced signal f and the noise signal have opposite phases, the video signal 1 from which the noise component has been removed is output.

At this time, adjust the volume to minimize noise in the output signal.

The video signal l from which noise has been removed is amplified by an output amplifier 11, outputted to a terminal 12, and applied to a monitor receiver or the like.

In the above example, in order to extract the difference between the high frequency signal and the slice signal, the polarity inversion circuit 17 was provided after the high frequency filter circuit 16.1. It may be placed in front of the P-wave circuit 16, or even if an inverting circuit is provided on the filtering circuit 13 side and a second inverting circuit is provided in the reproduced signal to be applied to the mixing circuit 19, the same noise suppression result can be obtained. can.

As described above, according to the present invention, noise in the rising or falling portions of the video signal is also reduced, and a good reproduced image can be obtained.

[Brief explanation of drawings]

FIG. 1 is an electrical block diagram showing an example of a conventional noise removal device, FIG. 2 is a waveform diagram explaining the same operation, and FIG. 3 is an example of a conventional noise removal device.
An electrical block diagram showing the embodiment, and FIG. 4 is a waveform diagram illustrating the same operation. 1... Video head, 4... FM demodulator, 5... De-emphasis circuit, 13, 16
...High frequency f-wave device, 14...Slice circuit, 15,19...Mixing circuit, 17...
...Polarity inversion circuit.

Claims (1)

[Claims] 1. A video signal from which noise is to be removed is filtered using a second high-frequency r-wave circuit and a first high-frequency r-wave circuit that has frequency characteristics with greater attenuation in the high frequency band compared to the second high-frequency filter circuit. The signal obtained by removing the low level part of the output of the first high frequency wave circuit and the output of the second high frequency wave circuit are mixed in opposite phase, and the mixed output is applied to the first high frequency wave circuit. A video signal noise removal device characterized by mixing noise with a video signal to be removed in an opposite phase.