JP2875094B2 - Comb filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproduction Y signal processing system of a video tape recorder (VTR) for high density recording.
The present invention relates to an improved comb filter for reducing crosstalk from adjacent tracks.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a comb filter in a conventional reproduction Y signal processing system.

[0003] A reproduced Y signal Yin is supplied from an input terminal 21 for 1H.
The signals are supplied to the delay line 22, the subtractor 23, and the subtractor 26. Further, the output signal Yd of the 1H delay line is supplied to a subtractor 23, where it is subtracted from the Yin to output only a region having no correlation of the Y signal. Although noise is included in this output signal, if this signal is limited in amplitude by a limiter 24, it can be made only noise, and after being attenuated by an attenuator 25, a subtractor 26 To supply.

When the noise component is subtracted from the reproduced Y signal Yin by the subtracter 26, the output shows a comb-shaped characteristic and the SN ratio is improved. In high density recording VTR long mode or 8-mm method VHS system using a card bandless recording, FM carrier during recording in each track 1 / 2f _H
Therefore, by using the above-mentioned comb filter, the reproduced crosstalk signal from the adjacent track is removed so as to be in the valley of the original signal at the time of demodulation.

When there is no vertical correlation between the Y signals, the switch 27 outputs the signal from the subtractor 23 to the decorrelation detecting circuit 2.
9 determines this, and opens the switch 27 to prevent the deterioration of the vertical resolution.

Although the azimuth recording method removes crosstalk to some extent, it is still insufficient, so that it is necessary to use a comb filter in the reproduction Y signal processing system as described above.

[0007]

The width of the reproducing head of the VTR differs for each set. Therefore, when the comb filter is used in a reproduction Y signal processing system for high-density recording as described above, noise is always subtracted at the same limiter level regardless of the magnitude of crosstalk caused by variations in reproduction head width. Was. Therefore, the influence of crosstalk sometimes appeared on the image quality. In particular, in a recording pattern that is not H-aligned with the adjacent track, the crosstalk component has a significant effect on the image quality. In a high-resolution VTR, the reproduced C signal and the Y signal crosstalk overlap, and the image quality deteriorates. The crosstalk between the adjacent tracks appears more clearly in the reproduced image as the reproduction head width is wider and wider than the track pitch.

[0008]

SUMMARY OF THE INVENTION In a comb filter according to the present invention, a delay circuit for delaying a Y signal, a subtractor for subtracting an undelayed Y signal and a delayed Y signal,
A limiter for limiting the output of the subtractor, a comb filter for a Y signal having a subtractor for subtracting the output of the limiter and the undelayed Y signal, a delay circuit for delaying the C signal, and a delay circuit for the undelayed C signal Adder for adding the obtained C signal, a comb filter for C signal having means for extracting the crosstalk of the burst signal portion from the output of the adder, and a crosstalk signal extracted from the comb filter for C signal Means for changing the level of the limiter of the Y-signal comb filter.

[0009]

Since the present invention has the above structure, the amount of crosstalk in the burst signal is detected by the comb filter for the C signal, and the limiter level of the comb filter for the Y signal is controlled by the amount. Irrespective of variations in the reproduction head width, the characteristics of the comb filter can be optimized to remove the crosstalk component in the Y signal.

[0010]

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

The upper side of FIG. 1 is a comb filter for the Y signal, and the lower side is a comb filter for the C signal. Symbols 1 to 9 of the Y-signal comb filter are 21 to 2 in FIG.
9 corresponds.

The reproduced Y signal Yin is supplied from the input terminal 1 for 1H.
The signals are supplied to the delay line 2, the subtractor 3, and the subtractor 6. The output signal Yd of the 1H delay line 2 is supplied to a subtractor 3, where it is subtracted from the Yin to output only a region having no correlation of the Y signal. The noise component in the output signal is extracted by limiting the amplitude by the limiter 4, attenuated by the attenuator 5, and supplied to the subtractor 6 via the switch 7. When the noise component is subtracted from the reproduced Y signal Yin in the subtracter 6, the output shows a comb-shaped characteristic, and only the frequency of the energy of the Y signal component is passed, so that the SN ratio is improved. When the Y signal has no vertical correlation, the output of the subtractor 3 is supplied to a decorrelation detection circuit 9 for detecting the signal. When the decorrelation signal is detected, the output is controlled. The signal is supplied to the switch 7 to open the switch.

Next, in the comb filter for C signals, first, a reproduced C signal Cin is supplied from an input terminal 10 to a 1H delay line 11, a subtractor 12, and an adder 13. The output signal Cd of the 1H delay line 11 is supplied to the subtractor 12 and the adder 13, and subtracted from and added to Cin, respectively. The output of the subtractor 12 becomes a C signal from which the crosstalk component has been removed, and is output from the output terminal 14 as Cout. On the other hand, the output of the adder 13 becomes a crosstalk component _CT , and the change in the output level controls the characteristics of the comb filter for the reproduced Y signal of the present invention.

[0014] C _T signal is amplified in the next stage of the amplifier 15, take out the crosstalk of the burst signal portion in the gate circuit 16. This means that in the crosstalk of the entire C signal, C
This is because an accurate crosstalk amount cannot be determined because the amplitude of the signal is not constant. Next, the crosstalk of the burst signal portion is supplied to an envelope detection circuit 17, where the envelope of the crosstalk signal is detected, converted into a DC voltage, and used as a control signal to be a limiter of a Y-signal comb filter. 4 Therefore limiter 4
When the crosstalk component is large, that is, when the output voltage of the envelope detection circuit 17 is high, the limiter level is raised to sharpen the comb characteristics, and when the crosstalk component is small, the comb characteristics are reversed. Works to make it dull.

[0015]

As described above, according to the present invention, when reproducing a VTR of high-density recording, regardless of the size of the reproducing head width, a crosstalk component from an adjacent track is converted into a cross signal of the burst signal portion. Depending on the magnitude of the talk amount, the characteristics of the Y signal comb filter can be changed to be optimal and removed, so that the image quality of the reproduced Y signal can be improved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a conventional example.

[Explanation of symbols]

 2,11 1H delay line 3,6,12 Subtractor 4 Limiter 13 Adder 16 Gate circuit 17 Envelope detection circuit

Claims (1)

(57) [Claims] 1. A delay circuit for delaying a Y signal, a subtracter for subtracting an undelayed Y signal and a delayed Y signal, a limiter for limiting an output of the subtractor, and an output of the limiter and an undelayed Y signal. A comb filter for a Y signal having a subtractor for subtracting the C signal, a delay circuit for delaying the C signal, an adder for adding the undelayed C signal and the delayed C signal, and a burst from the output of the adder A comb filter for C signal having means for extracting crosstalk of the signal portion; and means for changing the level of a limiter of the comb filter for Y signal by a crosstalk signal extracted from the comb filter for C signal. A comb-type filter comprising: