JP2557038B2 - Recording / reproducing method and recording / reproducing apparatus - Google Patents

Description

The present invention relates to a video tape recorder which controls the tape running speed by detecting a crosstalk component from an adjacent track to perform tracking control of a rotary magnetic head. The present invention relates to a recording / reproducing method, and further relates to a recording / reproducing apparatus for implementing such a recording / reproducing method.

[Background technology and its problems]

Generally, in a video tape recorder, as shown in FIG. 1, a video signal is recorded on a recording track 102 inclined with respect to the running direction of the tape 101, and a control track 1 for detecting the position of the recording track 102.
03 is set along one edge of the tape 101, and a control pulse signal (so-called C
The tape running speed is controlled by the TL pulse) so that the rotary magnetic head accurately traces the recording track 102.

However, a video tape recorder of this type of recording system requires a dedicated magnetic head for recording on the control track 103, which increases the manufacturing cost due to an increase in the number of parts and the control track 103. The space occupied by the magnetic tape 101 becomes a problem, which is extremely disadvantageous in terms of increasing the recording density on the magnetic tape 101.

Therefore, conventionally, a pilot signal of a different frequency is recorded on each recording track by being superimposed on the video signal, and a crosstalk component based on the pilot signal is recorded on adjacent recording tracks on both sides of the recording track traced during reproduction. A video tape recorder has been proposed in which the tape running speed is controlled according to the CN ratio to perform tracking control of the rotary magnetic head. According to this type of recording method, it is not necessary to provide a control track for controlling tape running separately from the recording track,
Therefore, the cost increase due to the expansion of the magnetic head,
It is possible to solve the drawbacks such as a decrease in recording density due to the space of the control track on the magnetic tape.

By the way, the development of the magnetic tape used for the video tape recorder as described above is also progressing. For example, in a so-called vapor-deposited tape in which a magnetic material is vapor-deposited on a base film, the thickness of the magnetic layer is about 0.1 μm, which is larger than that of the coating tape. Since it is extremely thin, it is possible to record for a long time on a tape cassette of the same size. Further, since the uniformity of the film thickness of the magnetic layer is extremely excellent, it is known that the recording and reproducing characteristics are extremely improved.

Therefore, it is conceivable that such an evaporated tape is used for a video tape recorder of a tracking control system using the crosstalk component as described above to enhance the performance, but in this case, the property of the evaporated tape causes a problem. Is coming.

That is, in the above vapor deposition tape, since the magnetic layer is extremely thin, the recording magnetic field obtained by converting the long wavelength recording signal by the magnetic head is recorded by the magnetic head when recording / reproducing a long wavelength signal, that is, a low frequency signal. Since it penetrates through the layer, only the phase modulation component of the recording magnetic field contributes to the signal output during reproduction, and the amplitude modulation component does not contribute, which makes normal recording / reproduction impossible.
In particular, since a low frequency signal of about 100 to 160 kHz is used for the frequency of the pilot signal, it is difficult to detect the crosstalk component unless the CN ratio of the pilot signal is secured to some extent, and the above-mentioned crosstalk component causes Tracking control becomes impossible.

[Object of the Invention]

Therefore, the present invention has been proposed in view of the conventional circumstances as described above, and can secure the necessary CN ratio of the pilot signal by using the vapor-deposited magnetic tape, and can reliably perform the tracking control by the crosstalk component. An object is to provide a recording / reproducing method and a recording / reproducing apparatus.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention sequentially records pilot signals of four different frequencies on a recording track on a vapor-deposited magnetic tape inclined with respect to the tape running direction and scans the recording track for reproduction. The tape running control is performed according to the difference frequency between the crosstalk component from the adjacent recording track and the pilot signal of any one of the above four frequencies, and the recording track inclined with respect to the tape running direction is traced to the video signal. In a video tape recorder for recording / reproducing data, the residual magnetic flux density of the magnetic layer of the vapor-deposited magnetic tape is Br [Gauss], and the thickness of the magnetic layer is t mag [μm]. The width S [μm] is 6 μm ≦
Within the range of S ≦ 14 μm, the crosstalk amount C [dB] required for the tape running control is within the range of 4 dB ≦ C ≦ 12 dB, It is characterized in that the video signal is recorded and reproduced by setting so as to satisfy the following equation. Further, the recording / reproducing apparatus according to the present invention comprises pilot signal recording means for sequentially recording pilot signals of four different frequencies on recording tracks on a magnetic tape inclined with respect to the tape running direction,
The tape tape is provided with tape running control means for carrying out tape running control in accordance with a difference frequency between a crosstalk component from an adjacent recording track reproduced by scanning the recording track and a pilot signal having a certain frequency among the four tapes. Guard band width S [μm] between recording tracks on the format
Within the range of 6 μm ≦ S ≦ 14 μm, and the crosstalk amount C [dB] required for the tape running control is 4 dB ≦
Within the range of C ≦ 12 dB, the above magnetic tape It is a vapor-deposited magnetic tape having a magnetic layer having a thickness t mag [μm] formed of a magnetic material having a residual magnetic flux density Br [Gauss] satisfying the following equation.

〔Example〕

Hereinafter, specific examples of the present invention will be described with reference to the drawings.

First, in the recording / reproducing method of the present invention, as shown in the tape format in FIG. 2, recording tracks 2 inclined with respect to the running direction X of the tape 1 are recorded on the vapor-deposited magnetic tape 1 at a predetermined track pitch P. A pilot signal for generating a crosstalk component for tracking control of a magnetic head, which will be described later, is previously recorded on these recording tracks 2 in an overlapping manner.

The track pitch P is set so as to have a guard band width S between the recording tracks 2 so as to reduce crosstalk generated between video signals recorded on the adjacent tracks 2.

As the pilot signal, used is a low frequency signal of about 100-200k Hz, for example frequency 6.5F _H becomes f _1, the frequency 7.6F _H becomes f _2, the frequency 10.5F _H becomes f _3, the frequency 9.4F _H becomes f _Four
4 types of signals having different frequencies are used. Here, f _H indicates a reference frequency, and for example, the horizontal scanning frequency of the video signal is used. The pilot signals f _{1 to} f ₄ described above are sequentially recorded on the tracks 2 in a repeating order of f ₁ , f ₂ , f ₃ , f ₄ , f ₁ , f ₂ .

Next, when reproducing the video signal recorded on each track 2 described above, the reproduction signal is supplied to the frequency mixer 3 as shown in the block diagram of FIG. 3, and the frequency mixer 3 is sequentially supplied. that _{f 1, f 4, f 3} , a band-pass filter 4 the components of the difference frequency between the frequency signal f ₂ as the center frequency f _H
And a bandpass filter 5 having a center frequency of 3f _H are used to detect a pilot signal due to crosstalk from adjacent tracks. The tracking control is performed based on the comparison output obtained by comparing the signal levels of the pilot signals due to these crosstalks in the level comparator 6.

That is, as shown in Table 1, the difference frequency with the crosstalk component based on the pilot signal of the recording track 2 on the left side of the recording track 2 traced by the magnetic head is always 2.9 f _H , and the recording track on the right side is The difference frequency with the crosstalk component based on the 2 pilot signal is always 1.1f _H
Select the frequency of the pilot signal supplied at the time of reproduction so that the band-pass filter 4 having a center frequency of f _H
And the band pass filter 5 having a center frequency of 3f _H extracts only the signals of the respective difference frequencies, and the level comparator 6 compares the crosstalk amounts based on the pilot signals of the adjacent tracks corresponding to the outputs of the respective difference frequency components. By doing so, the running speed of the tape 1 is controlled so that the magnetic head accurately traces the center of the recording track 2.

For example, when the output of the difference frequency component of the frequency of 2.9 f _H is high, that is, when the crosstalk amount from the track 2 on the left side is large, the magnetic head is tracing close to the track 2 on the left side and the tape 1 When the output speed of the difference frequency component of frequency 1.1f _H is high, that is, when the crosstalk amount from the track 2 on the right side is large, the magnetic head moves to the track 2 on the right side. Since the traces are approaching, the running speed of the tape 1 is slightly increased to accurately trace the magnetic head.

By the way, in order to perform the above-mentioned tracking control, it is necessary to secure the difference frequency output to such an extent that it can be detected by a device using the difference frequency output. Therefore, the crosstalk component based on the pilot signal recorded in advance on the recording track 2 is eliminated. It is necessary to secure the crosstalk amount C. At this time, the crosstalk amount C depends on the guard band width S and the CN ratio of the pilot signal at the center of the recording track 2 as shown in the graph of FIG. FIG. 4 shows a change in the CN ratio of the reproduced pilot signal according to the amount of deviation when the tracking position of the magnetic head deviates from the center of the recording track 2. For example, the CN ratio of the pilot signal in the center of the recording track 2 is 50 dB, and the track width T is 16
.mu.m, the CH ratio of the reproduction pilot signal is approximately 24 .mu.m away from the center of the recording track 2, that is, at the same position as that of the tracking position of the magnetic head at the center of the adjacent track with a guard band width of 8 .mu.m. 20 dB, which corresponds to the amount of reproduced pilot crosstalk from the adjacent track. Incidentally, the guard band width S is also shown on the horizontal axis of FIG. 4, and this has a track width T of 16 μm, which is 16 from the center of the recording track 2.
It shows the guard band width when it deviates by more than μm.

Then, by rewriting FIG. 4, a graph shown in FIG. 5 can be obtained in which the necessary CH ratio of the pilot signal can be obtained from the crosstalk amount C and the guard band width S. That is, in FIG. 5, by measuring the guard band width S and the crosstalk amount C necessary for performing tracking control, it is determined how much the CN ratio of the pilot signal is required in the center of the track 2. To be For example, the guard band width S is 10
Assuming that the crosstalk amount C required for performing the tracking control is 6 dB, the CN ratio of the pilot signal to be recorded on the recording track 2 in advance is 38 dB.
The number in parentheses in FIG. 5 indicates the required amount of crosstalk.

This FIG. 5 shows the guard band width S in FIG.
In the range where [μm] is 0 μm ≦ S ≦ 16 μm, the required crosstalk amount C [dB] = 4 dB, 6 dB, 8 dB, 10 dB, 12 dB,
Guard band width S [μ with 14dB and 16dB as parameters
m] and the CN ratio of the pilot signal (logC / N) are shown, which shows that there is a relationship of logC / N = k × S + A1.

Here, k is a proportional constant, and for example, at C = 10 dB, the CN ratio of the pilot signal is about 32 dB at S = 5 μm, and is about 44 dB at S = 10 μm, so (44−32) /
(10-5) = 2.4, 6 μm ≦ S ≦ 14 μ
m, k = 2.1 approximately within the range of 4 dB ≦ C ≦ 12 dB. A1 is a parameter, that is, the crosstalk amount C
It is a constant that depends on [dB].

Further, the guard band width S [μm] in FIG.
Within the range of 0 μm ≦ S ≦ 16 μm, the crosstalk amount C [d
B] and the CN ratio (logC / N) of the pilot signal are shown as logC / N = 1 × C + A2.

Here, 1 is a proportional constant, and for example, at S = 10 μm, the CN ratio of the pilot signal is about 36.5 dB at C = 5 dB and about 45 dB at C = 10 dB, so (45−36.5) / (10
-5) = 1.7, 6μm ≦ S ≦ 14μm, 4dB
In the range of ≦ C ≦ 12 dB, l = 1.6 approximately. A2 is a constant that depends on the parameter, that is, the crosstalk amount C [dB].

When A1 = 1 × C + A3 and A2 = k × S + A3, the relationship between the guard band width S [μm], the crosstalk amount C [dB], and the pilot signal CN ratio (logC / N) is shown as logC / N = K x S + l x C + A3 ... The first formula is obtained.

Here, assuming that k = 2.1 and l = 1.6, for example, C in FIG.
CN ratio of pilot signal at S = 10dB, S = 10μm
Substituting dB, A3 = logC / N− (k × S + 1 × C) = 44− (2.1 × 10 + 1.6 × 10) = 7, and within the range of 6 μm ≦ S ≦ 14 μm and 4 dB ≦ C ≦ 12 dB. Approximately A3 = 7.4.

Therefore, the relationship between the guard band width S [μm] and the crosstalk amount C [dB] and the required CN ratio of the pilot signal is 6
Within the range of μm ≦ S ≦ 14 μm and 4 dB ≦ C ≦ 12 dB, it can be approximately represented by logC / N = 2.1 × S + 1.6 × C + 7.3.

On the other hand, the CN ratio of the pilot signal is the performance of the vapor-deposited magnetic tape 1 on which the recording track 2 is recorded, especially the residual magnetic flux density Br (unit Gaus) of the magnetic layer of the vapor-deposited magnetic tape 1.
s) and the magnetic layer thickness t mag (unit: μm) are closely related to each other. As shown in FIG.
It has been clarified by measurement that the maximum output Pout of the pilot signal that can be recorded in is proportional to the product of the residual magnetic flux density Br and the thickness t mag of the magnetic layer. This is a matter of course from the principle of magnetic recording.

When the pilot signal recorded on the vapor-deposited magnetic tape 1 is reproduced, the result shown in FIG. 7 is obtained, and the maximum output Pout of this pilot signal and the CN ratio of the pilot signal obtained during reproduction are in a proportional relationship. It has been found.
Note that Fig. 7 shows the CN ratio [dB] of the pilot signal as 40
To obtain dB, a reproduction output of about -107 dBm is required, and
To obtain 50 dB as the CN ratio [dB] of the pilot signal, approximately −
This indicates that a reproduction output of 93 dBm is required, and since the slope is 0.73, the CN ratio of the pilot signal ∝ (Pout) ^0.73 … the second formula, which is the second formula, was obtained.

Therefore, from the relationship between FIG. 6 and FIG. 7 described above, the residual magnetic flux density Br of the vapor-deposited magnetic tape 1 and the thickness tm of the magnetic layer are
It is clear that the product of ag and the CN ratio of the pilot signal has the relationship shown in FIG. That is, this Br × tm
The ag also has the proportionality of the CN ratio of the pilot signal and the CN ratio of the pilot signal ∝ (Br × tmag) ^0.73 ... 3rd formula, which is, for example, 1000Gauss · to obtain the CN ratio of the pilot signal of 46dB. Br × t of μm or more
The performance of the vapor-deposited magnetic tape 1 to be used is determined from the CN ratio of the necessary pilot signal such that the vapor-deposited magnetic tape 1 having a mag value needs to be used.

Here, if the third equation is modified, logC / N = 0.73log {A4 x (Br x tmag)} (A4 is a constant) ...
It becomes an expression.

From the relationship described above, the relationship between the guard band width S and the required crosstalk amount C and the performance of the vapor-deposited magnetic tape 1 used becomes clear. That is, by combining FIG. 5 and FIG. 8, the guard band width S
Also, the graph of FIG. 9 showing the relationship between the required crosstalk amount C and the performance (Br × tmag) of the vapor-deposited magnetic tape 1 used can be obtained.

Therefore, in order to perform the above tracking control of the magnetic head in a stable manner, the guard band width S provided between the recording tracks 2 and the amount of the crosstalk amount C that can be detected by the device used, the vapor deposition magnetic tape used. 1
Performance (product of residual magnetic flux density Br and magnetic layer thickness t mag)
Should be set so as to satisfy the relationship shown in FIG.

In FIG. 9, the guard band width S is 6 μm.
Within the range of ≦ S ≦ 14 μm and the crosstalk amount C of 4 dB ≦ C ≦ 12 dB, the relationship of Br × t mag for obtaining stable tracking control is 0.73log {A4 × (Br × t mag)} ≧ k × S + l × C + A3, and by modifying the above equation, (k "× S + l" × C + A5) Br × tmag ≧ 10 (k ", l", A5 are constants) From the values in Fig. 5 and Fig. 8, the constants in the above equation are determined, The relationship of the following equation 5 is approximately established.

That is, as shown in FIGS. 6 and 7 above,
To obtain about 41 dB as the CN ratio [dB] of the pilot signal,
A reproduction output of approximately -105 dBm is required, and for that purpose approximately Br x t
It is necessary to record the pilot signal on the recording layer of mag = 500 [G · μm]. Also, in order to obtain a CN ratio [dB] of the pilot signal of about 45 dB, a reproduction output of about -100 dBm is required. For that purpose, the pilot signal is applied to the recording layer of about Br × t mag = 1000 [G · μm]. Need to record. Also, to obtain about 48.5 dB as the CN ratio [dB] of the pilot signal,
A reproduction output of about -95 dBm is required, and for that, about Br × tm
It is necessary to record the pilot signal in the recording layer of ag = 2000 [G · μm].

The CN ratio [d] at the maximum output Pout [dBm] of the pilot signal when the values of Br × t mag in FIG.
FIG. 8 shows the value of [B] obtained from the measurement results shown in FIG.

That is, FIG. 8 shows Br × t mag of vapor-deposited magnetic tape.
[G · μm] value and obtained pilot signal CN ratio [d
B], the CN ratio [dB] (about 45 dB) of the pilot signal at Br × t mag = 1000 [G · μm] and Br × t mag = 1
CN ratio [dB] of pilot signal at 00 [G · μm] (approx. 31
The difference is 14.6 dB, which means that the CN ratio [dB] = 14.6log (Br × t mag) +2.5.

Therefore, this evaporated magnetic tape Br × t mag [G ・ μ
m] value and the obtained pilot signal CN ratio [dB], and the above-mentioned guard band width S [μm] and crosstalk amount C [dB] and the necessary pilot signal CN ratio From logC / N = 2.1 × S + 1.6 × C + 7.3, 14.6log (Br × t mag) +2.5 ≧ 2.1 × S + 1.6 × C + 7.4 That is, the above conditional expression Is obtained.

Especially, since the guard band width S and the required crosstalk amount C are determined by the recording method and performance of the apparatus used, the vapor deposition magnetic tape 1 used has a residual magnetic flux that satisfies the above expression 5. A magnetic layer having a density Br and a thickness t mag may be formed.

As described above, in the above embodiment, the guard band width S on the tape format, the detection limit of the crosstalk amount C of the device, the residual magnetic flux density Br of the vapor deposition magnetic tape 1,
By setting the thickness t mag of the magnetic layer so as to satisfy the fifth expression, the residual magnetic flux density Br of the vapor-deposited magnetic tape 1 and the thickness t mag of the magnetic layer are increased to the necessary minimum to obtain a low frequency signal. It is possible to achieve the tracking control without fail by solving the problem of saturation of the recording magnetic head as well as the signal output of the pilot signal. Also,
At this time, the values of the residual magnetic flux density Br of the vapor-deposited magnetic tape 1 and the thickness tmag of the magnetic layer need not be increased unnecessarily and can be set to the minimum values that satisfy the fifth expression. It is possible to prevent deterioration of the ratio and the like, and an image of good quality can be obtained.

〔The invention's effect〕

As is clear from the above description of the embodiments, according to the present invention, the residual magnetic flux density of the magnetic layer of the vapor-deposited magnetic tape is set to Br.
[Gauss], the magnetic layer thickness t mag [μm], the guard band width S [μm] between recording tracks on the tape format is within the range of 6 μm ≦ S ≦ 14 μm, and the tape running control is performed. The crosstalk amount C [dB] required for is within the range of 4 dB ≦ C ≦ 12 dB, By recording and reproducing the video signal by setting the following equation, the required CN ratio of the pilot signal can be secured by using the evaporated magnetic tape, and the tracking control by the crosstalk component can be surely performed. A reproducing method and a recording / reproducing apparatus can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a tape format in a conventional recording / reproducing method. FIG. 2 is a schematic diagram showing a tape format in a recording / reproducing method to which the present invention is applied, and FIG. 3 is a block diagram showing the principle of tracking control. 4 is a graph showing the relationship between the pilot signal CN ratio and the amount of deviation from the center of the recording track, and FIG. 5 is a graph showing the relationship between the guard band width S and crosstalk amount C and the necessary pilot signal CN ratio, Fig. 6 shows evaporated magnetic tape Br × t
FIG. 7 is a graph showing the relationship between the mag value and the recordable pilot signal output, FIG. 7 is a graph showing the relationship between the recorded pilot signal output and the CN ratio of the pilot signal obtained when reproducing, and FIG. 8 is A graph showing the relationship between the value of Br × tmag of the vapor-deposited magnetic tape and the CN ratio of the obtained pilot signal. FIG. 9 shows the relationship between the guard band width S and the amount of crosstalk C and the value of Br × tmag of the vapor-deposition magnetic tape. It is a graph shown. 1 ... Evaporated magnetic tape 2 ... Recording track

Claims (2)

(57) [Claims] 1. Crosstalk from adjacent recording tracks reproduced by scanning the recording tracks on a recording track on a vapor-deposited magnetic tape inclined with respect to the tape running direction and sequentially recording four pilot signals of different frequencies. Video tape recorder for recording / reproducing a video signal by performing tape running control according to a difference frequency between a component and a pilot signal of any one of the four frequencies and tracing a recording track inclined with respect to the tape running direction. , The residual magnetic flux density of the magnetic layer of the vapor-deposited magnetic tape was measured by Br [Gauss]
And the thickness t mag [μm] of the magnetic layer is the guard band width S between recording tracks on the tape format.
[Μm] is within the range of 6 μm ≦ S ≦ 14 μm, and the crosstalk amount C [d
B] within the range of 4 dB ≦ C ≦ 12 dB, A recording / reproducing method characterized by performing recording / reproduction of a video signal by setting the following equation. 2. Pilot signal recording means for sequentially recording pilot signals of four different frequencies on recording tracks on a magnetic tape inclined with respect to the tape running direction, and adjacent recording tracks reproduced by scanning these recording tracks. A tape running control means for carrying out tape running control in accordance with a difference frequency between the crosstalk component from the tape and a pilot signal of a certain frequency among the above four, and a guard band width S [μm between recording tracks on the tape format. ] Within the range of 6 μm ≦ S ≦ 14 μm, and the crosstalk amount C necessary for the tape running control is
[DB] is within the range of 4 dB ≦ C ≦ 12 dB, and the above magnetic tape is A recording / reproducing apparatus, which is a vapor-deposited magnetic tape having a magnetic layer having a thickness t mag [μm] formed of a magnetic material having a residual magnetic flux density Br [Gauss] satisfying the following equation.