JPS59191989A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the beat disturbance due to crosstalk by using a dynamic emphasizing circuit for line sequential chrominance signal which has the nonlinear amplitude characteristics and shows the larger emphasis to a small amplitude part of an input signal. CONSTITUTION:The line sequential chrominance signals of two color difference signals R-Y and B-Y are supplied from an input terminal 11. For these chrominance signals, a large emphasis is applied to a small amplitude part by a dynamic emphasizing circuit 12 having the nonlinear amplitude characteristics. A pre- emphasizing circuit 13 applies a larger emphasis to the high band component of an input signal. The input chrominance signal is changed to its original state through de-emphasizing circuits 25 and 26 having opposite characteristics to those of the circuits 12 and 13. When a part of the adjacent track is also reproduced, the angle modulated line sequential signal has an fH (horizontal scan frequency)/2 offset. Therefore the beat due to the crosstalk of a demodulation mode is also set at the fH/2. Thus the beat disturbance due to the crosstalk is reduced with interleaving.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing device that angle-modulates a luminance signal and a chrominance signal, and records and reproduces them on the same track by frequency multiplexing them.

Conventional household magnetic recording and reproducing apparatuses employ a 2-rad diagonal scanning system, in which color video signals are recorded one field at a time diagonally on a magnetic tape using two arsenic heads. The recorded color video signal is
A color video signal of a standard method such as the Nrsc method is separated into a luminance signal and a carrier signal, and the luminance signal is angle-modulated.
The carrier color signal is frequency-converted to the lower frequency side and frequency-multiplexed.

FIG. 1 is a schematic diagram showing an example of the recording and reproducing mechanism of such a conventional magnetic recording and reproducing apparatus.

1.2 is a magnetic head, 3 is a rotating cylinder, and 4 is a magnetic tape.

In the figure, a rotating cylinder 3 rotates at a speed of 30 revolutions per second in the direction of arrow A, and two magnetic heads 1 and 2 are mounted on its outer peripheral surface at positions symmetrical to each other with respect to the rotation axis of the rotating cylinder.
There is a tail.

Further, the magnetic tape 4 travels in the direction of arrow B and contacts the outer circumferential surface of the rotary cylinder 3 obliquely over approximately 180 degrees.

Therefore, the magnetic head 1.2 alternately scans the magnetic tape every half rotation of the rotary cylinder 3, and records or reproduces color video signals one field at a time.

FIG. 2 is a pattern diagram showing the tracks on the magnetic tape 4 formed by the recording and reproducing mechanism of FIG. A), and as a result, diagonal tracks 5 are formed on the magnetic tape 4 on which color video signals are recorded one field at a time.

For magnetic fields, the directions of the gaps between tracks 1 and 2 are made different from each other with respect to the running direction (arrow A) of the magnetic heads 1 and 2 on the magnetic tape 4, and the magnetization directions are made different between adjacent tracks. Azimuth recording is being done. For this reason, there is no need to provide guard bands between adjacent tracks, and the recording density is improved, making long-time recording possible.

FIG. 3 shows an example of the frequency spectrum of the luminance signal and color signal recorded on the magnetic tape 4 of FIG.
is a carrier wave of the angle-modulated luminance signal, 7 is a sideband of the luminance signal, and 8 is a carrier color signal converted to a low band.

That is, a standard color video signal is separated into a luminance signal and a carrier color signal, and the luminance signal is converted into an angle-modulated luminance signal consisting of a carrier wave 6 and a sideband 7 by angle-modulating a carrier wave centered at about 4MEz. The carrier chrominance signal is frequency-converted to produce a carrier chrominance signal 8 on the lower frequency side as well as the angle-modulated luminance signal.

However, according to such conventional technology, during playback,
There was a drawback that the low-frequency converted carrier color signal was affected by jitter, and color unevenness was likely to occur on the screen.

In order to overcome this drawback, a technique was proposed in which the angle modulation recording method is resistant to jitter, and the color signal is recorded by angle modulation.

FIG. 4 shows the frequency spectrum of this prior art, where 9 is the carrier wave of the angle-modulated color signal, 10 is the sideband wave of the color signal, and parts corresponding to those in FIG. 3 are given the same reference numerals. I'm wearing it.

In FIG. 4, the luminance signal is angularly modulated into a carrier wave 6,
The angle-modulated luminance signal is made up of sideband waves 7, and one color signal is angle-modulated in the baseband band, and the angle-modulated luminance signal is also made into an angle-modulated color signal made up of a carrier wave 9 and sideband waves 10 on the lower frequency side. These angle-modulated luminance signals and angle-modulated color signals are mixed and recorded on the same track as shown in FIG.

In this case, since the frequency range in which the frequency band of the angle-modulated color signal should be set is narrow, the two color difference signals R-Y, B-Y
Since it is difficult to angle-modulate each time, and color information is less noticeable on the screen than luminance information, color signals that are angle-modulated are line-sequential color difference signals R-Y and B-Y. Color signals are used.

In this way, the effect of jitter on the color signal can be reduced, whereas.

The drawback is that angle modulated frequency beat interference of the chrominance signal occurs due to crosstalk from adjacent tracks.

That is, as shown in FIG. 2, when the azimuth recording method is used so that no guard band is provided between adjacent tracks, the reproducing head simultaneously scans the adjacent tracks and records adjacent tracks 1 . Play back the recorded signal from the Since the angle-modulated luminance signal has a high frequency, the azimuth loss is large, and the angle-modulated luminance signal is not reproduced from adjacent tracks, but the angle-modulated color signal has a low frequency, so the azimuth recording is small, and the reproduction is delayed as crosstalk. This generates a beat with the reproduced angle modulated color signal from the track being reproduced and scanned, degrading the quality of the reproduced image.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing apparatus that eliminates the drawbacks of the prior art described above, reduces beat interference due to crosstalk, and can obtain high-quality reproduced images.

[Summary of the invention]

To achieve this objective, the present invention provides the following advantages: since the effect of beat disturbance is noticeable on small amplitude portions of color signals,
The color signal is characterized in that a larger emphasis is applied to the small amplitude portion of the color signal when it is recorded.

[Embodiments of the invention]

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

Figure 5 11. v31 is a block diagram showing an embodiment of the magnetic recording/reproducing device according to the present invention, and 11 is an input terminal;
12 is a dynamic emphasis circuit, 13 is a pre-emphasis circuit, 14 is an angle modulation circuit, 15 is an input terminal,
16 is an adder circuit, 17 is an input terminal, 18 is a signal processing circuit, 19 is an angle modulation circuit, 20 is an input terminal, 21 is a recording amplifier circuit, 22 is a preamplifier circuit, 23 is a low frequency single wave generator, 24
25 is an angle demodulation circuit, 25 is a tie-emphasis circuit, 26 is a dynamic tie-emphasis circuit, 27 is an output terminal,
28 is a band f-wave device, 29 is an angle demodulation circuit, 30 is a signal processing circuit, and 31 is an output terminal, and parts corresponding to those in FIG. 1 are given the same reference numerals.

First, regarding the recording circuit system of this embodiment, FIG. 5 (A1
Explain using.

From the input terminal 11, two color difference signals R-Y are output.

B-Y line sequential color signals are supplied. Emphasis is added to this line-sequential color signal in a dynamic emphasis circuit 12. As shown in FIG. 6, this dynamic emphasis circuit 12 has nonlinear amplitude characteristics, and a large emphasis is applied to a small amplitude portion of the input signal.

The linear next color signal to which such emphasis has been added is supplied to a pre-emphasis circuit 13. As shown in FIG. 7, the pre-emphasis circuit 13 has non-linear frequency characteristics, and a larger emphasis is applied to the high-frequency components of the input signal.

The line sequential color signal from the pre-emphasis circuit 13 is modulated by the angle modulation circuit 14 and supplied to the addition circuit 16.

Further, a control signal is supplied from the input terminal 15 to control the frequency of the angle modulation circuit 140, and the frequency of the carrier wave (hereinafter referred to as the angle modulated line sequential color signal) of the angle modulated line sequential color signal (hereinafter referred to as the angle modulated line sequential color signal). The carrier offset is set by changing the center frequency (this center frequency is a frequency corresponding to a specific level of the line-sequential color signal, for example, a horizontal blanking level) every field or every horizontal scanning period. Let it stand.

On the other hand, a luminance signal is supplied from the input terminal 17, and this luminance signal is subjected to processing such as pre-emphasis and clipping in a signal processing circuit 18, and then supplied to an angle modulation circuit 19 where it is modulated. In the angle modulation circuit 19, the angle modulation frequency is controlled by a control signal from an input terminal 20.

The angle-modulated luminance signal (hereinafter referred to as angle-modulated luminance signal) from the angle modulation circuit 19 is supplied to the adder circuit 16 where it is frequency-multiplexed with the angle-modulated line sequential color signal, amplified by the recording amplifier circuit 21, and magnetically The tape 4 is supplied to magnetic helides 1 and 2 which scan the tape 4 alternately, and is recorded on the abrasive tape 4.

In addition, so that the frequency band of the angle-modulated line sequential color signal is set lower than the frequency band of the angle-modulated luminance signal,
The angle modulation frequency of the angle modulation circuit 14.19 is set.

Next, regarding the reproduction circuit system of this embodiment, FIG.
Explain using.

The magnetic disks 1 and 2 alternately scan the magnetic tape 4 for reproduction, thereby reproducing a frequency multiplexed signal of an angle-modulated line-sequential color signal and an angle-modulated luminance signal. This frequency multiplexed signal is amplified by a preamplifier circuit 22 and supplied to a low-band r wave generator 23 and a band wave generator 28.

The low-pass P wave generator 26 separates the angle modulation line sequential color signal from the frequency multiplexed signal. The angle-modulated line-sequential washing signal is supplied to the angle-modulation circuit 24 to demodulate the line-sequential color signal. This line sequential color signal is processed by the pre-emphasis circuit 16 (Fig. 5-1).
It is supplied to the emphasis circuit 25, which has a frequency characteristic opposite to that of the frequency characteristic (FIG. 7), and is emphasized.
An amplitude that is opposite to the amplitude characteristic of Fig. 5 (A) (Fig. 6), etc.
Dynamics having a characteristic are supplied to the output terminal 27 to be supplied to the output terminal 26 and applied to the output terminal 27.
supplied to

On the other hand, the band f-wave unit 28 separates the angle modulated luminance signal from the supplied frequency multiplexed signal. This angle-modulated luminance signal is supplied to an angle demodulation circuit 29, where the luminance amplitude is modulated. This luminance signal is supplied to the output terminal 31 without being subjected to processing such as de-emphasis in the signal processing circuit 30.

In this embodiment, line-sequential color signals are used during recording.

Emphasis is applied by the dynamic emphasis circuit 12 so that the amplitude of the small amplitude portion is further emphasized,
During playback, a dynamic emphasis circuit 26 adds emphasis so that the amplitude becomes 1 element. As mentioned earlier, if you use the azimuth recording method and do not provide a guard band between each track, the tracks that the RADs 1 and 2 are trying to play back (hereinafter referred to as the "tracks") will be played back and scanned. At this time, tracks adjacent to this track are also scanned for reproduction at the same time, and the reproduction signals from the adjacent tracks and tracks are mixed into the reproduction signal from the relevant track as a crosstalk component. Since the signal recorded on each track is angularly modulated, the reproduced signal from the track and the crosstalk component cause a beat.

By the way, the width in which the magnetic head reproduces and scans the @ contact track is small, and therefore the amplitude of the crosstalk component is also small, so the beat component is also small, but when the amplitude of the line sequential color signal is small, Even if the beat component is small, the amplitude ratio of the beat component to the line-sequential color signal becomes large, and the beat appears prominently in the reproduced image, degrading the image quality.

In this embodiment, since a larger emphasis is applied to the small amplitude portion of the line sequential color signal, the amplitude ratio of the beat component to the line sequential color signal is always sufficiently small, so that the beat in the amphibious image is not noticeable. Image quality improves.

Furthermore, if the color signal processing circuit has a narrow band, the high-frequency components of the color signal deteriorate, and as a result, beats become more noticeable near the color change point. However, in this embodiment, a pre-emphasis circuit 13 (513th (, 41)) having the frequency characteristics shown in FIG. At this time, since de-emphasis is performed by the de-emphasis circuit 25 (FIG. 5 (B1)), the above-mentioned beat becomes less noticeable.

Figure 8 shows the dynamic emphasis circuit 1 in Figure 5 (A).
2 is a block diagram showing a specific example of 2, in which 32 is Rimi;
33 is an adder circuit, and 64 is an output terminal.

In FIG. 8, the line sequential color signal from the input terminal 11 is
IJ is supplied to the emitter circuit 32 and the adder circuit 63.

The IJ emitter circuit 32 does not limit the amplitude of the supplied line sequential color signal when the amplitude is small, but limits the amplitude when the amplitude is large. In the adder circuit 33, the output signal of the limiting circuit 32 is added to the line sequential signal from the input terminal 11, and therefore, in the line sequential color signal obtained at the output terminal 54, the small amplitude portion is amplitude-emphasized. The large amplitude portion becomes a signal whose amplitude is hardly emphasized.

It is preferable that such a dynamic emphasis circuit 12c be provided in the preceding stage of the pre-emphasis circuit 13 (FIG. 5(, 41)).

Note that the dynamic de-emphasis circuit 26 (FIG. 5 (B1)) is the pre-emphasis circuit 25 (FIG. 5 (H)).
It is preferable to provide it at the latter stage.

The pre-emphasis circuit 25 has the frequency characteristics shown in FIG. 7, and the T value (the reciprocal of the maximum frequency at which the minimum emphasis is applied) and the X value (the ratio between the maximum emphasis amount and the minimum emphasis amount) are , NTSC system and P
In the current standard method such as the AL method, 52μ'+2
For high-definition television systems where the number of scanning lines is twice that of the current standard system (for example, 1125 lines), 2.6 ps and 2 to 4 are suitable, respectively. .

FIG. 9 is a pattern diagram showing the tracks on the magnetic tape on which the color video signal processed by the recording circuit system of FIG. 5V) is recorded. , 3 (S is a track.

In the same figure, track 35 is formed by the magnetic nod 1 (FIG. 1), and track 36 is formed by the magnetic nod 2 (FIG. 1).
1), the angle modulation circuit 14 in FIG.
However, it is assumed that a carrier offset of (fx is the horizontal scanning frequency) is applied.

Tora Ri 35. ! Frequency multiplexed signals of angle-modulated line-sequential color signals and angle-modulated luminance signals are recorded in +6 for each field, and the angle-modulated frequency of the angle-modulated line-sequential color signals recorded in track and track 65 is recorded in each field. The center frequency of the angle modulation frequency of the angle modulation line sequential color signal recorded on the track 36 is (fc
+fx/2) Now, assuming that the magnetic head is currently scanning the track 35 for reproduction, if part of the adjacent track 36 is also scanned for reproduction at the same time,
The angle-modulated line-sequential color signal from track 36, that is, the crosstalk component, has an offset of fH/2 with respect to the angle-modulated line-sequential color signal reproduced from track 35. The beat frequency is fB/2. Therefore, the beats appearing on the playback screen are interleaved and visually reduced.

FIG. 10 is a pattern diagram showing tracks when the recorded angle-modulated line-sequential color signal has a carrier offset of fH/4 between fields.

37, 38, 39, and 40 are trucks.

In the figure, each track 37, 38, 39, and 40 has one field of frequency multiplexed signals of an angle modulated line sequential color signal and an angle modulated luminance signal recorded, respectively. If the center frequency of the angle modulation frequency of the angle modulation line sequential color signal is fc, track 3
In 8 (fc+, fii/4) - track 39
The angle modulation circuit 14 in FIG. The center frequency of the angular modulation frequency of the modulation line sequential chrominance signal is fc, and the other every fourth tiger is (
fc+hr, A) and C for every other 4th track.
fc+fH/2) Furthermore, for every other four tracks, (
fc hr/4).

When a frequency multiplexed signal is reproduced from a magnetic tape on which angle-modulated line-sequential color signals are recorded, the frequency of the beat component due to crosstalk from adjacent tracks is f#/4.
On the playback screen, it becomes a diamond beat and becomes less noticeable.

As described above, when a carrier offset is applied to the angle-modulated line-sequential color signal for each field, that is, between tracks, the beats generated on the playback screen become conspicuous. is further reduced, and the quality of the reproduced image is greatly improved.

In addition, the angle modulation line sequential color signal and the angle modulation luminance signal are
When recording and reproducing by frequency multiplexing as described above, due to the third-order distortion characteristics of the magnetic tape-magnetohesode system, second-order distortion components are mixed into the reproduced signal, resulting in beat disturbance.

However, as described above, this type of beat disturbance can be suppressed by providing a carrier offset to the angle modulation line sequential color signal between the track and the track.

That is, if the carrier offset value of the angle modulation line sequential color signal between tracks is selected as hr/4, the frequency of the beat component due to the above second-order distortion component is Ypx 2×"pu
(However, YFM is the angle modulation frequency of the angle modulation luminance signal,
CFM is the angle modulation frequency of the angle modulation line sequential color signal), so this beat component is f#/
It will have an offset of 2. Therefore, the phase of this beat component is reversed for each field, making it more noticeable on the playback screen.

In the above method, the angle modulation line sequential color signal has a carrier offset for each field, but 1. It is also possible to have a carrier offset in the field, and the same effect as when the field has a carrier offset can be obtained.

That is, in every horizontal scanning period, the angle modulation line sequential color signal has a carrier off of fll/4. If you hold the
A beat component with a frequency gradient of YFM-2×CFM has a carrier offset of f#/2 per horizontal scanning period.

This means that the beat disturbance is interleaved by f#/2 for each horizontal scanning line, making it less noticeable on the playback screen. In this case, by specifying the running speed of the magnetic tape and the inclination of the rotating cylinder with respect to the magnetic tape, B alignment can be performed between adjacent tracks, and the angle modulation line sequential color signals of adjacent tracks can be aligned. A carrier offset of fB/2 or fx/a can be provided, so that beat disturbances due to crosstalk are suppressed.

In addition, in the above embodiment, FIG. 5 (, (+, (fl
, it is preferable to provide the dynamic emphasis circuit 12 before the pre-emphasis circuit 13, but of course the dynamic emphasis circuit 12 may be provided after the pre-emphasis circuit 16. In this case, the dynamic de-emphasis 26 is It is necessary to provide it before the de-emphasis circuit 25.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to suppress the influence of crosstalk components consisting of angle-modulated line-sequential color signals caused by simultaneously reproducing and scanning adjacent tracks. The interference is greatly reduced and the quality of the reproduced image is greatly improved, making it possible to provide a magnetic recording and reproducing device with excellent functionality by eliminating the drawbacks of the prior art described above.

[Brief Description of the Drawings] Fig. 1 is a schematic configuration diagram showing an example of a recording/reproducing mechanism of a conventional magnetic recording/reproducing device, and Fig. 2 shows tracks on a magnetic tape formed by the recording/reproducing mechanism of Fig. 1. 3 is a spectrum diagram showing an example of the frequency spectrum of the luminance signal and color signal recorded on the magnetic tape, and FIG. 4 is a spectrum diagram showing an example of the frequency spectrum of the luminance signal and color signal recorded on the magnetic tape. 5(A) and β) are block diagrams showing one embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIG. 6 is a spectral diagram showing another example of the spectrum. A characteristic diagram showing an example of amplitude characteristics,
FIG. 7 is a characteristic diagram showing an example of the frequency characteristics of the pre-emphasis circuit of FIG. FIG. 5(, 41, (In the embodiment of (a), a pattern diagram showing tracks formed on a magnetic tape when the carrier offset value of the angle-modulated line sequential color signal between fields is fE/2, Figure 10 is a pattern diagram showing tracks formed on the magnetic tape when the carrier offset value is fH/4. 1.2...Magnetic head 4...Magnetic tape 11
... line sequential color signal input terminal 12 ... dynamic emphasis circuit 15 ... pre-emphasis circuit 14 ... angle modulation circuit 15 ... control signal input terminal 16 ... addition circuit 17 ... Luminance signal input terminal 19...Angle modulation circuit 23...Low frequency P wave device 2
4... Angle demodulation circuit 25... De-emphasis circuit 26... Dynamic de-emphasis circuit 28...
・Band r wave device 29...Angle demodulation circuit 1st figure $2 figure 4th dark boy's brown q figure C figure 2 - cover. Figure 6 Figure 9 Figure 10

Claims (1)

[Claims] Magnetic recording in which a luminance signal and a line-sequential color signal are each angularly modulated, the frequency band of the line-sequential color signal is set lower than the frequency band of the luminance signal, and recording and reproduction are performed on the same track. In the reproducing device, a non-linear circuit having a small amplitude emphasis characteristic is provided in the front stage of the angle modulation circuit for the line sequential color signal, and the line sequential color signal is reproduced by emphasizing the small amplitude portion and then angularly modulating the line sequential color signal. A magnetic recording and reproducing apparatus characterized in that it is configured to suppress crosstalk components from adjacent tracks that are mixed into the line-sequential color signal.