JPH06187703A - Magnetic recording / reproducing device - Google Patents

Abstract

(57) [Abstract] [Purpose] Tracking is controlled so that the end of the head coincides with the boundary of the formed track. [Structure] A signal (V ₁ ) from a sample hold circuit 55 is supplied to an A / D conversion circuit 1, and a signal to turn on during normal reproduction is supplied from a terminal 2 to this conversion circuit 1. The signal from the conversion circuit 1 is supplied to the memory 3, and the signal from the memory 3 is supplied to the D / A conversion circuit 4. The signal from the conversion circuit 4 is supplied to the × 2 circuit 5, the signal from the × 2 circuit 5 is supplied to the switch 6, and the switch 6 is supplied with a signal to be turned on at the time of the lower edge tracking from the terminal 7. . The signal from the switch 6 is supplied to the adder 8 provided between the sample hold circuit 56 and the differential circuit 69 and added to the signal (V ₂ ).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus capable of controlling tracking by using a pilot signal and performing joint photographing and after-recording.

[0002]

2. Description of the Related Art In a VTR, for example, the recording density has been increased, and the narrowing of the recording track on the tape has been promoted as a means for that. Particularly, in a digital VTR for recording / reproducing a signal as digital data, since the recording is made multi-track, the width is further narrowed.

Tracking control of such a narrowed recording track is no longer possible by a method using a conventional CTL track, for example. Therefore, the applicant of the present application has previously proposed a tracking control method for such a narrowed recording track (Japanese Patent Application No.
114802).

FIG. 6 shows a recording pattern used in the prior application. In this pattern, a pilot signal (frequency f ₂ ) for tracking control is recorded for every four tracks, and a signal (frequency f ₁ ) for detection is recorded on the tracks on both sides thereof. And when playing back this recording pattern,
For example, the tracking control is performed by detecting the crosstalk of the pilot signal (f ₂ ) reproduced by the head reproducing the track A.

That is, FIG. 7 shows a tracking (ATF) error signal detection circuit. In this figure, the terminal 50
A reproduction signal from a rotary head (not shown) is supplied to a bandpass filter (BPF) 52 for extracting a signal of frequency f ₂ through a reproduction amplifier 51, and the signal from the bandpass filter 52 is supplied to an envelope detection circuit. 53. Furthermore, this envelope detection circuit 5
The signal from 3 is supplied to the sample hold circuits 55 and 56 through the low pass filter (LPF) 54.

The signal from the reproduction amplifier 51 has a frequency f.
Bandpass filter (BPF) 57 for extracting ₁ signal
The signal from the band pass filter 57 is supplied to the envelope detection circuit 58. Further, the signal from the envelope detection circuit 58 is supplied to a level comparison circuit 60 through a low pass filter (LPF) 59, and a period in which the signal level is equal to or higher than a predetermined level is taken out.

The signal from the level comparing circuit 60 is supplied to the monostable multivibrator (monomulti) 61 at time T _{6 by} the falling trigger, and the monomulti 61 is supplied.
Is supplied to a monostable multivibrator (monomulti) 62 for generating sampling pulses. The signal from the monomulti 62 is supplied to the AND circuits 63 and 64.

Further, the signal from the level comparison circuit 60 is supplied to the monostable multivibrator (monomulti) 65 at time T _{7 by} the rising trigger, and this monomulti 65 is supplied.
Is supplied to a monostable multivibrator (monomulti) 66 for generating a gate pulse. The signal from the monomulti 66 is supplied to the AND circuit 63. The sampling pulse from the AND circuit 63 is supplied to the sample hold circuit 56.

Further, the signal from the level comparison circuit 60 is
It is supplied to the monostable multivibrator (monomulti) 67 at time T _{8 by} the rising trigger, and this monomulti 6
The signal from 7 is supplied to a monostable multivibrator (monomulti) 68 for generating a gate pulse. The signal from the monomulti 68 is supplied to the AND circuit 64. The sampling pulse from the AND circuit 64 is supplied to the sample hold circuit 55.

These sample and hold circuits 5
The signals from 5, 56 are supplied to the differential circuit 69, and the signal from this differential circuit 69 is taken out to the output terminal 71 of the ATF error signal through the amplifier 70.

Therefore, in this device, for example, in FIG.
For the tracks A1 and B2 as shown in FIG. 5, the signal as shown by B in the figure is taken out from the band pass filter 57, and the signal as shown in C in the figure is taken out from the band pass filter 52. Further, a signal as shown by D in the figure is taken out from the level comparison circuit 60. Also,
A signal as shown by E in the same figure is taken out from the monomulti 62.

Further, a signal as shown by F in the same figure is taken out from the mono-multi 65, and a signal as shown by G in the same figure is taken out from the mono-multi 66. As a result, the sampling pulse as shown by H in the figure is taken out from the AND circuit 63. Further, a signal as shown by I in the figure is taken out from the monomulti 67 and the monomulti 68
A signal as indicated by J in FIG. As a result, a sampling pulse as indicated by K in the figure is taken out from the AND circuit 64.

That is, in the above-mentioned track A1, for tracking detection after a time corresponding to scanning of the rotary head by, for example, 2Dx (Dx: offset between tracks) from the fall of the first identification signal (frequency f ₁ ). The crosstalk of the signal (frequency f ₂ ) is sampled and held by the circuit 56. In the recording track A2, for example, 2 from the trailing edge of the second identification signal (frequency f ₁ ).
The crosstalk of the tracking detection signal (frequency f ₂ ) after the time corresponding to the scanning of the Dx rotary head is caused by the circuit 5
The sample is held at 5.

Therefore, by supplying these crosstalk levels to the differential circuit 69, the ATF error signal is taken out to the output terminal 71 through the amplifier 70. Then, the tracking control is performed by controlling the capstan or the like so that the ATF error signal becomes "0". Further, the operation of the recording tracks A1 and A2 is repeated for each of the above-mentioned four recording tracks. The times T _{6 to} T ₈ of the monomultis 61 to 67 are set according to the recording format on the tape.

In this apparatus, the recording tracks are formed diagonally on the tape by using a rotary head, and the width of the head is made larger than the track pitch so that the tracks are sequentially overwritten. ing. That is, the width of the recording track is formed narrower than the width of the head. On the other hand, the above tracking is A
By setting the TF error signal to “0”, for example, A in FIG.
Control is performed so that the center of the head scans the center of the track as shown in FIG. This is the best method for normal playback.

However, for example, when so-called splicing is performed on a recorded tape, recording is performed from the middle of the tape after performing the above-mentioned reproduction. For this reason, for example, as shown in B of the same figure, a part of the track just before newly recorded is rewritten, and the track width becomes narrow. As a result, the reproduction level is lowered, which may affect image quality, sound quality, and the like. Further, the fluctuation of the track pitch becomes a disturbance to the tracking servo, and the disturbance of the servo easily occurs.

Further, for example, when after-recording other signals while leaving the above-mentioned ATF error signal detection area, a part of the track just before after-recording is rewritten as shown in C of FIG. As in the case described above, the reproduction level is lowered, and the image quality and sound quality may be affected. Further, a track shift occurs in the signal area and the ATF area, and the reproduction is always performed in the track shift state during reproduction. This application is made in view of such a point.

[0018]

The problem to be solved is that in the case of joint recording or after-recording, a part of the track just before being newly recorded is rewritten, and the track width becomes narrow. Therefore, the reproduction level may be lowered, and the image quality and sound quality may be affected.

[0019]

According to a first means of the present invention, a rotary head is used to form an oblique track on a tape, and the width of the head is made larger than a track pitch so that the oblique track is formed. In a magnetic recording / reproducing apparatus configured to be sequentially overwritten, a pilot signal is recorded at a predetermined position in the track, and at the time of reproduction, crosstalk levels of the pilot signals from the adjacent tracks are compared. The tracking control is performed, and a predetermined offset voltage is added to the crosstalk level so that the tracking control can be performed so that the end portion of the head coincides with the boundary of the formed track. A characteristic magnetic recording / reproducing apparatus.

According to the second means of the present invention, when the joint recording is performed on the partially recorded tape, the tracking is performed so that the end of the head coincides with the boundary of the formed track. Is a magnetic recording / reproducing apparatus according to the first means.

According to a third means of the present invention, when the after-recording is performed on the recorded tape, the tracking control is performed so that the end of the head coincides with the boundary of the formed track. It is the magnetic recording / reproducing apparatus according to the first means.

A fourth means according to the present invention is the magnetic recording / reproducing apparatus according to the first means, characterized in that switch means 6 for turning on and off the predetermined offset voltage added to the crosstalk level is provided. is there.

[0023]

According to this, since the tracking control is performed so that the end of the head coincides with the boundary of the formed track, the recorded track is not rewritten, the reproduction level is lowered, and the image quality is improved. It is possible to prevent the sound quality from being affected.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the state where center tracking is performed as shown in FIG. 2A, for example, when the track width is T _{P and the} head width is T _W , ΔT = (T _W −T _P ) / 2 is the lower edge of the head. Is cutting into the previous truck. Therefore, when tracking (lower edge tracking) is performed in a state where the track is shifted upward by ΔT, a track pattern having no fluctuation in track width and track pitch before and after after-recording is obtained as a joint recording as shown in B of the figure. can get.

On the other hand, assuming that the amount of crosstalk is proportional to the amount of overlap between the head and the track, when the crosstalk amount from the upper track is V ₁ and the crosstalk amount from the lower track is V ₂ , With center tracking as shown in A,

[Equation 1] Tracking is possible in the state of.

[0026] Under the edge tracking, as shown in B _{contrast, V 1 = K (T W} -T P) V 2 = 0 So, an offset voltage V to V _{2 off} [= K (T _W -T
And V ₂ by the addition of _P)].

The offset voltage V _off is twice the value of [Equation 1]. Therefore, the value of V ₁ or V ₂ is stored during normal reproduction, and this value is doubled to V ₂
The lower edge tracking as shown in B can be realized by adding to.

That is, in general, the offset voltage V _{off is set} to V
_When added to ₁ or V ₂ , the tracking state changes. If this shift amount is e (μm),

[Equation 2]

[Equation 3] Becomes

[0029] Here, since the way across the servo becomes V ₁ = V _2, from expression (2) = Formula 3, 2Ke = V _off e = V _off / 2K, and the proportion to the offset voltage V _off The shift amount e can be changed.

A circuit for realizing such a lower edge tracking can be implemented by a structure as shown in FIG. 1, for example. That is, in the figure, the signal (V ₁ ) from the sample hold circuit 55 described above is supplied to the A / D conversion circuit 1, and the conversion circuit 1 is supplied from the terminal 2 with a signal to be turned on during normal reproduction. The signal from the conversion circuit 1 is supplied to the memory 3, and the signal from the memory 3 is supplied to the D / A conversion circuit 4.

The signal from the conversion circuit 4 is supplied to the × 2 circuit 5, the signal from the × 2 circuit 5 is supplied to the switch 6, and the switch 6 receives a signal from the terminal 7 to turn on during the lower edge tracking. Supplied. Then, the signal from the switch 6 is supplied to the adder 8 provided between the sample hold circuit 56 and the differential circuit 69,
It is added to the signal (V ₂ ).

In this circuit, during normal reproduction, A / D
The conversion circuit 1 is turned on and the value of the signal (V ₁ ) at this time is stored in the memory 3. The stored value is D / A converted, multiplied by ₂ , and supplied to the adder 8 through the switch 6 and added to the signal (V ₂ ) at the time of lower edge tracking. As a result, the lower edge tracking as shown in B of FIG. 2 can be realized.

In this way, according to the above-mentioned apparatus, since the tracking control (lower edge tracking) is performed so that the end of the head coincides with the boundary of the formed track, the recorded track is not rewritten. It is possible to prevent the reproduction level from being lowered and the influence on the image quality and the sound quality.

Further, in the above-mentioned device, since the pilot signal (f ₂ ) is actually a low frequency, an output can be obtained even if the head and the track do not overlap. Therefore, in an actual device, a correction for that is required.

That is, assuming that the actual head width T _W is T _W + ΔT _W at the pilot frequency, center tracking

[Equation 4] Tracking is possible in the state of.

[0036] This shift amount e to the lower edge tracking for _{the, e = (T W -T P} ) / 2 , and the offset voltage V _off to be applied to V _2, the

[Equation 5] Becomes

Since the term ΔT _W is unknown from the equation (4), V _off of the equation (5) cannot be obtained. Note that ΔT
_W is determined by processing accuracy and the like, and its value usually varies by about 1 to 2 μm.

On the other hand, also in the case of performing the lower edge tracking including ΔT _W , the offset voltage is twice V ₁ and V ₂ at the time of center tracking (or V ₁ +) as described above.
In _{V 2), V off = K} (T W + ΔT W -T P) shift amount, e = become _{(T W + ΔT W -T P} ) / 2. Note that these relationships are shown in FIG.

The relationship between the offset voltage V _off , the overlap amount, and the shift amount is as shown in FIG. 4, and if the offset voltage V _off is reduced from the state of C of FIG. 3, it becomes B of FIG. The state of is obtained. Here, in the states of B and C of FIG. 3, since the actual heads have different positions on the track where the signals are to be reproduced, the output levels of the reproduced signals (preamble, video, audio) are different.

That is, as the state of C in FIG. 3 shifts to B, the output level of the reproduced signal increases and becomes constant in the state of B in FIG. Similarly, when the offset voltage V _off is increased from the state of A of FIG. 3, the reproduction level of the signal starts to decrease from the constant state as shown in FIG. 5 and after the state of B of FIG.

Utilizing these, the above-mentioned detection of the offset voltage V _off is performed as follows.

(1) First, center tracking is performed with the offset voltage being 0, and the crosstalk amount from the upper track at this time is V ₁ and the crosstalk amount from the lower track is V ₂ which is A / D and add to obtain the initial value of the offset voltage. In addition, the reproduction level of the signal is envelope-detected and A / D processed to obtain the reference level of the reproduction level.

(2) Next, the initial value of the offset voltage is output, and the reproduction level is detected after a lapse of a predetermined time until the tracking is stabilized. When the reproduction level is equal to or lower than the reference level, the offset voltage is reduced by a predetermined value and output, and the operation is repeated until the reproduction level matches the reference level (or within its allowable range). The offset voltage thus obtained is used as the set value.

(3) In order to obtain the offset voltage V _off using the initial value and the set value of the offset voltage thus obtained, V ₁ + V ₂ is detected in the center tracking state during normal reproduction, It suffices to calculate (V ₁ + V ₂ ) × (set value / initial value).

In order to improve the reliability, the above-mentioned detections (1) and (2) may be repeated several times, and the average value thereof may be obtained and used as the set value.

Further, in the above calculation, (V ₁ + V ₂ ) changes due to changes in the reproducing system over time, differences in the characteristics of the tape, and the like.
On the other hand, (set value / initial value) is a value that does not change unless the head is replaced. Therefore, the value of (set value / initial value) is detected once and stored in a memory or the like, so that the offset voltage V _off can be obtained from the next time only by detecting (V ₁ + V ₂ ). .

The offset voltage V _off obtained in this way can be output during joint recording and after-recording for lower edge tracking.

[0048]

According to the present invention, since the tracking control is performed so that the end of the head coincides with the boundary of the formed track, the recorded track is not rewritten and the reproduction level is lowered. Also, it has become possible to prevent the effects on image quality and sound quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of an example of a magnetic recording / reproducing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a state of the tracking.

FIG. 3 is a diagram for explaining the explanation.

FIG. 4 is a diagram for explaining the explanation.

FIG. 5 is a diagram for explaining the explanation.

FIG. 6 is a diagram for explaining a recording pattern.

FIG. 7 is a configuration diagram of an ATF error signal detection circuit.

FIG. 8 is a diagram for explaining the explanation.

FIG. 9 is an explanatory diagram showing a state of each tracking.

[Explanation of symbols]

1 A / D conversion circuit 2 Terminal to which a signal to be turned on during normal reproduction is supplied 3 Memory 4 D / A conversion circuit 5 × 2 circuit 6 Switch 7 Terminal to which a signal to be turned on during lower edge tracking is supplied 8 Adder 55, 56 Sample and hold circuit 69 Differential circuit

Claims (4)

[Claims] 1. A magnetic recording wherein a rotary head is used to form diagonal tracks on a tape, and the width of the head is made larger than a track pitch so that the diagonal tracks are sequentially overwritten. In the reproducing apparatus, a pilot signal is recorded at a predetermined position in the track, and at the time of reproduction, tracking control is performed by comparing crosstalk levels of the pilot signals from the adjacent tracks, and at the same time, a predetermined crosstalk level is set. The magnetic recording / reproducing apparatus is characterized in that the tracking control can be performed so that the end portion of the head coincides with the boundary of the formed track by adding the offset voltage of. 2. When the joint recording is performed on the partially recorded tape, the tracking control is performed so that the end of the head coincides with the boundary of the formed track. The magnetic recording / reproducing apparatus according to claim 1. 3. When the after-recording is performed on the recorded tape, the tracking control is performed so that the end portion of the head coincides with the boundary of the formed tracks. The magnetic recording / reproducing apparatus described. 4. The magnetic recording / reproducing apparatus according to claim 1, further comprising switch means for turning on / off the predetermined offset voltage added to the crosstalk level.