JPH063654B2 - Tracking error detection circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tracking error detection circuit in a helical scan type magnetic recording / reproducing apparatus, and more particularly to A of DAT.
The present invention relates to a tracking error detection circuit used for TF control.

(Prior Art) The tracking control of DAT is performed by ATF control, and the principle thereof will be described with reference to FIGS. 2 to 4.

FIG. 4 (a) is a perspective view showing the relationship between the rotary drum 30 of the DAT device and the traveling path of the magnetic tape 31, and the rotary drum 30 has two heads ha and hb (not shown) on their peripheral surfaces. Are arranged at the same height position where the same movement locus is obtained, and rotated in the direction of arrow J at 2000 revolutions per minute. The magnetic tape 31 includes guide rollers 34 and 35 that regulate the movement in the width direction, the rotating drum 30, and the tilt pin 3.
The tape is formed on the tape path formed by the parts 2 and 33 in the direction of arrow K at a predetermined tape speed v.

At this time, the winding angle of the magnetic tape 31 around the peripheral surface of the rotary drum 30 is about 90 degrees (however, the outer diameter of the rotary drum is 30φ).
In this case), the angle between the tape running direction of the winding portion and the rotation axis of the rotary drum is set to be the reference angle θr.

FIG. 4 (b) is a plan view showing a relative angle θ between the tape running direction in the winding portion and the rotation axis of the rotary drum.

On the other hand, FIG. 2 is a partially enlarged view of the ATF area of the track pattern recorded on the magnetic tape. This ATF area is formed at two locations near both ends E ₁ and E _{2 in the} width direction of the magnetic tape. Part E _{3 in} the figure shows a PCM area in which a PCM signal is recorded. In this ATF area, blocks P (shown by hatched portions) in which pilot signal s ₁ is recorded and blocks A and B in which sync signals s _{2 of} different frequencies are recorded corresponding to heads ha and hb, respectively.
(Represented by a horizontal line portion and a vertical line portion, respectively) and a block D in which an IBG signal is recorded. During signal reproduction, heads ha, h having a scanning width of about 1.5 times the track width
b alternately scans adjacent tracks to reproduce the signal recorded on the magnetic tape. Now, let us show the situation of the pilot signal s ₁ reproduced when the head hb scans on the track T ₄ . It is shown in FIG. At this time, the head hb is AT
Each block P ₅₁ , P ₃₁ , P ₄₁ , and A of the F area E ₁ part
The blocks P ₄₂ , P ₅₂ , and P ₃₂ in the TF area E ₂ are sequentially scanned, and the pilot signal s ₁ recorded in these blocks is sequentially reproduced.

FIG. 3A shows a reproduction level waveform of the pilot signal s ₁ when the head hb normally scans the track T ₄ . At this time, in the ATF area E ₁ , the reproduction level of each pilot signal s ₁ of the block P ₃₁ of the left adjacent track T ₃ and the block P ₅₁ of the right adjacent track T ₅ becomes the same level, and similarly in the ATF area E 1. _{Even in the second} copy, the reproduction levels of the blocks P ₃₂ and P ₅₂ are the same. This is because, in each of the ATF areas E ₁ and E ₂ , the width in which the head hb scans the track T ₃ is equal to the width in which the head Tb scans the track T _5, and the width center of the track T ₄ is equal to the width center of the head hb. It shows that we are doing.

FIG. 11B shows a reproduction level waveform when the head hb is scanned in the state of being shifted to the right track T ₅ side. At this time, the width in which the head hb scans the track T ₅ increases and conversely the left side. The width of scanning the track T ₃ is reduced. Therefore, the reproduction level of the pilot signal s ₁ recorded on each of the tracks T ₅ and T ₃ also increases and decreases in proportion to this deviation. Further, in the same figure (c), the head hb shows the left track T ₃
A reproduction waveform when scanning is performed in a state of being shifted to the side. At this time, the reproduction level of the track T ₃ increases and the reproduction level of the track T ₅ decreases.

As described above, when the head h causes a track deviation, the reproduction level of the pilot signal s ₁ reproduced on the adjacent track increases or decreases depending on the direction and magnitude of the deviation.

The ATF control sequentially detects the level difference of the pilot signal s ₁ reproduced in the blocks P of these adjacent tracks,
The magnetic tape speed v so that these reproduction levels match
It controls the rotation speed of the capstan.

FIG. 7 shows an AT used for conventional general ATF control.
The block diagram of F control system is shown.

In the figure, the reproduction signal s ₀ amplified by the RF amplifier 17 is
A low-pass filter 18 for detecting the pilot signal s ₁ ,
And the bandpass filter 19 for detecting the sync signal s ₂
Is applied to each. The envelope detection circuit 1 inputs a pilot signal s ₁ having a reproduction frequency of 130.67 kHz, and outputs a level voltage signal s ₃ corresponding to this level to a subtractor 2 and a sample hold circuit (hereinafter referred to as SH circuit) 3. When the control circuit 4 receives the sync signal s ₂ and confirms that this frequency corresponds to the scanning head, the pulse-shaped control signal s ₆ at a predetermined timing,
Output s ₇ . For example, in FIG. 2, when the head hb scans the track T ₄ , it reaches the block B ₄₁ to detect the sync signal s ₂ , and when it is confirmed that this frequency corresponds to the head hb, t ₁ shown in FIG. The control signal s ₆ is output at the timing of, and the control signal s ₇ is output at the timing of t ₂ . The SH circuits 3 and 20 hold the input signals by these control signals. Therefore, S
The H circuit 3 holds the level voltage of the pilot signal detected from the block P ₅₁ of the adjacent track T _{5 on} the right side, and S
The H circuit 20 holds the level difference signal s ₄ between this level voltage and the level voltage of the pilot signal detected from the block P ₃₁ of the left adjacent head T ₃ . These hold operations are performed each time the sync signals s ₂ corresponding to the tracks ha and hb are detected, so that the hold signal output from the SH circuit 20 is a tracking error voltage signal (hereinafter, TE signal) indicating a tracking error. It will be referred to as a voltage signal) s ₅ .

This TE voltage signal s ₅ is averaged by the smoothing circuit 21 to become an average voltage signal s _13, and this average voltage signal s ₁₃ is
It is input to a capstan motor drive circuit 15 which drives a capstan motor 16 which is a tape transfer means. The capstan motor drive circuit 15 controls the capstan motor 16 so that the input average voltage signal s ₁₃ becomes 0 level.
Is rotationally driven, and the tape speed v is negatively feedback controlled by the ATF control system based on the average voltage signal s ₁₃ .

(Problems to be Solved by the Invention) The sync signal s ₂ ′ corresponding to the head hb detected when the scanning position of the head hb scanning the ATF area E ₁ is moved between the tracks, and level voltage signal s ₃ Figure 5 the change trajectory of the detection level of the '(to distinguish denoted by the as described later, the above-mentioned sync signal s _2, level voltage signal s ₃ and meaning slightly different order') ( It is shown in a) and (b).

First, the level change of the sync signal s ₂ ′ shown in FIG. 5 (a) will be described with reference to FIG. Block B
The level Vs ₄ of the sync signal s ₂ ′ detected at _{41 is} at the maximum level when the center of the head hb scans the center of the track T ₄ and is 1 in the right adjacent track T ₅ direction (+ direction).
It does not change until it reaches the position d ₁ which is displaced by / 4 track,
If the head hb further deviates in the same direction, the width over which the head hb passes the block B ₄₁ decreases, and the level Vs ₄ decreases linearly. Eventually, the position d ₄ further deviates from the center of the track T ₅ by 1/4 track to reach 0. It becomes a level. On the other hand, the level V of the sync signal s ₂ ′ detected in the block B ₆₁ of the track T ₆
s ₆ linearly increases when the head hb moves past the position d ₃ , reaches the maximum level at the position d ₆ , and thereafter, similar level changes are repeated in accordance with the + h movement of the head hb.

In addition, the head hb moves to the left adjacent track T ₃ direction (-direction).
It is clear that the sync signal s ₂ ′ is also detected when the shift is shifted to, and changes as shown in FIG. The level Vs ₂ is the level of the sync signal s ₂ ′ detected by the block B ₂₁ of the track T ₂ .

Next, the level change of the level voltage signal s ₃ ′ that is taken in according to the movement of the head hb will be described with reference to FIGS. 5B and 2.

At this time, the control circuit 4 detects the level of the pilot signal of the adjacent track at the predetermined timings t ₁ and t ₂ shown in FIG. 3 from the time when the sync signal s ₂ ′ of the block B higher than the threshold value Vf is detected. Therefore, the control signals s ₆ and s ₇ are output. Therefore, when the head hb is in the range w ₂ , it passes the block B ₂₁ where the sync signal is detected, and when it is in the range w ₄ , it passes the block B ₄₁ and further the range w ₆ When it is inside, the level of the level voltage signal s ₃ ′ of the block P scanned by the head hb is fetched at predetermined timings t ₁ and t ₂ from the time when the block B ₆₁ is passed.

When the control circuit 4 detects the sync signal over the entire range, it does not detect the next sync signal until the control signals s ₆ and s ₇ based on the sync signal are output. Therefore, the dotted line portion in FIG. Sync signal is not detected.

Therefore, when the scanning center of the head hb is at the center of the track T ₄ , the level Vp ₁ (shown by the solid line) of the level voltage signal s ₃ ′ captured at the timing t ₁ and the timing t _{2 are obtained.}
The level Vp ₂ (indicated by the dotted line) of the level voltage signal s ₃ ′ captured by the head h in blocks P ₅₁ and P ₃₁ respectively.
b becomes the detection level of the pilot signal detected,
These are at the same level as shown in FIG. Next, when the scanning position of the head hb shifts in the + direction, the level Vp ₁ linearly increases and the level Vp ₂ linearly decreases. Then, at the position d ₁ , the level Vp ₂ becomes 0, and the position d ₃
Thus, the level Vp ₁ becomes maximum. Further Kosu position d _3, head hb is to begin detecting the pilot signal of the block P ₆₁ at the timing t _2, the level Vp ₂ increases linearly again. Then, when the detection level of the sync signal of the block B ₆₁ exceeds the position d ₇ where it becomes larger than the threshold value Vf, the above range w ₆ is reached, and at the predetermined timing t ₁ and t ₂ from when the block B ₆₁ is passed, the block P
The level of the level voltage signal s ₃ 'of Therefore,
The level Vp ₁ is 0 from the position d ₇ to the position d ₆ where the pilot signal of the block P ₇₁ is detected, while the level Vp ₂ is the detection level of the pilot signal of the block P ₅₁ and is the maximum level to the position d _4. Keep above, and linearly decrease when this is exceeded. When the scanning center of the head hb eventually reaches the center of the track T ₆ , the levels Vp ₁ and Vp ₂ become the same level again, but at this time, each level is a pilot signal detected by the head hb in blocks P ₅₁ and P ₇₁ , respectively. Is the detection level of. Further, even when the head hb is displaced in the − direction, the levels Vp ₁ and Vp _{2 of the} level voltage signal s ₃ ′ are generated.
Are detected in the same manner, and it is clear that they change as shown in the figure.

Next, in the ATF area E ₂ , the change locus of the level voltage signal s ₃ ′ detected when the scanning position of the head hb moves between the tracks is shown in FIGS. 5 (a) and 5 (c). , And FIG. 2 will be described.

At this time, the changing locus of the sync signal s ₂ ′ that changes corresponding to the scanning position of the head hb is exactly the same as that of the ATF area E _1, but the changing locus of the level voltage signal s ₃ ′ is the fifth.
It is slightly different as shown in FIG. That is, when the scanning center of the head hb deviates in the + direction from the center of the track T ₄ ,
The levels Vp ₁ and Vp ₂ are ATF area E ₁ up to the position d _3.
It changes as in the case of the section. However, even if the position d ₃ is exceeded, there is no block P to be detected at the timing t ₂ at this time, and therefore the level Vp ₂ is increased like the ATF area E ₁ portion and the 0 state is maintained. On the other hand, the level Vp ₁ is the detection level of the pilot signal of the block P ₄₂ from the position d ₇ where the sync signal detection block is changed from B ₄₂ to B ₆₂ to the position d ₄ , and during this period, the head is detected as shown in FIG. It decreases linearly as hb moves in the + direction.

Although the level change locus of the pilot signal detected in the ATF areas E ₁ and E ₂ when the scanning position of the head hb moves between tracks has been described above, the pilot signal is the same when the head ha moves between tracks. Change. However, in this case, in the correspondence relationship between the scanning position of the head ha and the level change locus, the track position is shifted by one track as shown in () of FIG. Furthermore A
The locus of the pilot signal level change in the TF area E ₁ is shown in FIG. 7C, and the locus of the pilot signal level change in the ATF area E ₂ is shown in FIG. In other words, the relationship is opposite to that of the head hb, but this is because the arrangement relationship between the sync signal block B and the pilot signal block P corresponding to the head hb in the ATF area E ₁ is in the head ha in the ATF area E ₂ . This is because the arrangement relationship between the block A and the block P of the corresponding sync signal matches.

The TE voltage signal s ₅ output from the SH circuit 20 of FIG.
Is the difference voltage (Vp ₁ −Vp ₂ ) between the levels Vp ₁ and Vp ₂ obtained in synchronization with the detection of the sync signal satisfying the above condition.
Becomes FIG. 5 (d) shows a change locus in which a solid line in FIG. 5 (b) is drawn with a dotted line, and FIG. 5 (e) shows a change locus in which a solid line is drawn with a dotted line in FIG. 5 (c). Therefore, when the scanning position of each head ha, hb moves between tracks, the difference voltage Va ₁ obtained by detecting the sync signal corresponding to the ATF area E _{1 by} the head ta and the head hb correspond to the ATF area E ₂ . The differential voltage Vb ₂ obtained by detecting the sync signal that moves moves along the change locus in FIG.
There corresponding figure is the difference between the voltage Vb ₁ and head ta obtained by detecting the sync signal is a differential voltage Va ₂ obtained by detecting the corresponding sync signals ATF area E ₂ of the ATF area E ₁ (d) Will move on the change trajectory of.

Now, a rotary drum in which the heads ha and hb are arranged at the same height position (position where the movement loci are the same) as during recording has a reference angle θ whose angle between its axis and the tape running direction is the same as during recording.
When reproducing the ATF signal of the tape transported at a rotation speed of 2000 at a rotation speed of 2000 per minute and at a tape speed vp substantially equal to that at the time of recording, the heads ha and h for scanning the ATF areas E ₁ and E ₂ respectively.
The positional relationships of the scanning positions of b with respect to the center of the corresponding track Tr are all the same. In this case, the difference voltages Vb ₁ and Vb on the respective change loci of FIGS.
a ₂ and the differential voltages Va ₁ and Vb ₂ are on the coaxial line and move.

On the other hand, when the heads ha and hb have a height deviation, the positional relationship between the scanning position of each head and the center of the track Tr corresponding to each of the ATF areas E ₁ depends on the height deviation. There is an error wh, and ATF area E
_{Also in 2} , the same amount of height error wh occurs. These errors wh are the difference voltage Va ₁ in FIGS. 5 (d) and 5 (e).
And Vb ₁ and Va ₂ and Vb ₂ can be expressed as an error in the moving position.

It should be noted that the figure shows a case where the head hb is lower than ha (because the position corresponding to the lower head is displaced in the − direction).

If the angle formed by the axis of the rotating drum and the tape running direction has a tilt error with respect to the reference angle θr at the time of recording, the scanning direction of each head is not parallel to the recorded track direction, and therefore the head ha Scanning position is ATF area E
_The positional relationship between _{1 and} the corresponding track center Tr and the positional relationship between the ATF area E _{2 and} the corresponding track center Tr cause a tilt error wws depending on the tilt, and the head hb has the same error. A slope error ws of the quantity is generated. These errors ws can be expressed as errors in the moving positions of the difference voltages Va ₁ and Va ₂ and Vb ₁ and Vb ₂ in FIGS. 5D and 5E.

Incidentally, in the same figure, in the angular relationship shown in FIG. 4 (b), a case is shown in which the angle θr at the time of recording is inclined by −Δθ. In this case, since the scanning direction of the head shown in FIG. 2 shifts clockwise, the relationship shown in FIGS. 5 (d) and 5 (e) is obtained.

As described above, the movement position errors wh and ws are inevitably generated when the head height and the rotary drum inclination are different during recording and reproduction.

In this case, when the tape speed fluctuates and the relative positional relationship between each head and the track is deviated, the difference voltages Va ₁ , Va ₂ , Vb ₁ and Vb ₂ of the TE voltage signal s ₅ output from the SH circuit 20 become , While keeping the errors wh and ws from each other,
It moves along the change locus of FIGS. For example, the tape speed Vr during recording and the tape speed Vp during reproduction
When the relation of Vr <Vp, the direction is +, conversely Vr> V
When p, it moves in the-direction.

As described above, the ATF control is generally performed so that the average level of the TE voltage signal s ₅ becomes 0 level.
Is controlled by negative feedback, the level of each differential voltage is normally stabilized at the positions shown in FIGS. 5 (d) and 5 (e).

As described above, the voltage of the TE voltage signal s ₅ output from the SH circuit 20 is the same for the heads ha and hb as the ATF area E ₁ ,
Every time E ₂ is scanned, the difference voltage shown in FIG. 5 causes ... Vb ₂ ,
_{Va 1, Va 2, Vb 1} , Vb 2, is updated Va ₁ ... in the order of. Therefore, when there is a height error of the head and a tilt error of the rotating drum during recording and reproduction, the level change of each differential voltage increases substantially in proportion to this level, and this level change is always caused by the TE voltage signal. Appears in s ₅ .

Therefore, in order to obtain the information necessary for the ATF control, that is, the average voltage signal s _{13 in} which the level change component caused by the height error and the inclination error is removed from this TE voltage signal s ₅ , the head voltage fluctuations of each head are determined. There is a drawback in that a smoothing circuit that slows the response to the scanning position movement information is required.

The present invention obviates the need for smoothing circuits which produce these drawbacks.

(Means for Solving Problems) With the helical scan method, the first and second heads arranged on the peripheral surface of the rotary drum are used to form the first and second areas near both ends of each track of the magnetic tape. Is a tracking error detection circuit for reproducing the pilot signal recorded in, and performing tracking control at the time of reproduction on the basis of the reproduced pilot signal, wherein the first head corresponds to the first area. A first sample and hold circuit that sequentially samples and holds the level difference information of a pair of pilot signals of another track that is detected at different first and second timings in synchronization with the detection of the sync signal recorded on the first track. And the first head is synchronized with the detection of the sync signal recorded on the corresponding first track in the second area, and A second sample and hold circuit that sequentially samples and holds the level difference information of a pair of pilot signals of another track detected at the 1st and 2nd timings; and the second head that the second head corresponds to in the first area. A third sample-and-hold circuit that sequentially samples and holds the level difference information of the pair of pilot signals of the other track that is detected at the first and second timings, in synchronization with the detection of the sync signal recorded on the first track; A pair of pilot signals of a value track that the second head synchronizes with the detection of the sync signal recorded on the corresponding second track in the second area and that is detected at the first and second timings. A fourth sample-and-hold circuit for sequentially sampling and holding the level difference information of Comprising a summing circuit for adding the output signal.

(Operation) The four sample and hold circuits sequentially sample and hold the corresponding level difference information, and add the output signals of the respective sample and hold circuits to thereby obtain an error in the height relationship between the pair of heads at the time of reproduction from that at the time of recording, Also, it is possible to average the level fluctuation between the level difference information that is inevitably caused by the inclination error of the rotating drum during reproduction with respect to recording.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of the present invention, and its operation will be described with reference to the timing chart of FIG. 6. The same parts as in FIG. The detailed description thereof will be omitted.

Reference numeral 5 in the figure is a quaternary counter, and when the control signal s ₆ is input, the states of the output terminals 5 _{1 to} 5 ₄ connected to one input terminals of the AND circuits 6 to 9 are shown in FIG. The "H" state is set in order. AND circuit 6-9, the control signal s ₇ appearing in synchronism with the control signal s ₆ to the other input terminal
, And outputs the AND signals s _{8 to} s ₁₁ shown in FIG. 6 to the control signal input terminals of the SH circuits 10 to 13, respectively.
The SH circuits 10 to 13 respectively input the level difference signal s ₄ , and sample and hold at the timing of “H” of the AND signals s _{8 to} s ₁₁ . Therefore, each SH circuit outputs the TE voltage signals s _{51 to} s _{54 in} which the corresponding difference voltages are sequentially updated to the adder 14. FIG. 6 shows a state in which the voltages of the TE voltage signals s _{51 to} s ₅₄ are sequentially updated based on the respective differential voltages which are stable in the level states shown in FIGS. 5 (d) and 5 (e). k) to (n). In this case, the difference voltages Va ₁ , Va ₂ , Vb ₁ , and Vb ₂ of the TE voltage signals output from the SH circuits 10 to 13 respectively do not change, but as shown in FIG. It is clear that when the position of the differential voltage shown in (e) moves along each locus, the level of each differential voltage changes for each sampling.

The adder 14 is to output a sum voltage signal s ₁₂ obtained by adding the TE voltage signal s ₅₁ ~s _54, the sum voltage signal s ₁₂
Of the differential voltage Va ₁ , Va ₂ , which are sequentially updated,
The average level of Vb ₁ and Vb ₂ , that is, the average position of the head center position with respect to the track center of the ATF areas E ₁ and E ₂ scanned by the heads ha and hb, respectively, is shown, and changes depending on the tape speed fluctuation.

The capstan motor drive circuit 15 and the capstan motor 16 which operate based on the added voltage signal s ₁₂ are the same as those in FIG. 7, and therefore their explanations are omitted.

Although the smoothing circuit is not provided in the subsequent stage of the adder 14 in the above embodiment, a smoothing circuit may be provided as necessary for the purpose of making the ATF control have desired characteristics.

(Effect of the invention) When reproducing a DAT tape recorded by another model, there is a height error between the head during recording and the time when reproducing,
If there is an error in the inclination of the rotary drum, each differential voltage of the TE voltage signal causes a level difference based on these errors as described above. However, according to the present invention, a smoothing circuit that slows down the response speed of control, or This level difference is averaged without using a smoothing circuit having a steep frequency characteristic that leads to instability, so that the response speed is fast and the ATF is stable.
It is possible to control.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIGS. 2 to 5 are diagrams for explaining the present invention, and FIG. 6 is a timing chart diagram showing signal waveforms of respective parts of FIG. FIG. 7 is a block diagram of an ATF control system used for conventional general ATF control. 1 ... Envelope detection circuit, 2 ... Subtractor, 3, 20,
10 to 13 ... Sample and hold circuit, 4 ... Control circuit, 5
... quaternary counter, 6-9 ... AND circuit, 14 ... adder,
15 ... Capstan motor drive circuit, 16 ... Capstan motor, 17 ... RF amplifier, 18 ... Low pass filter, 19 ... Band pass filter, 21 ... Smoothing circuit.

Claims (1)

[Claims] 1. A pilot recorded in a first and a second area near both ends of each track of a magnetic tape by a first and a second head arranged on a peripheral surface of a rotary drum by a helical scan method. A tracking error detection circuit for reproducing a signal and performing tracking control at the time of reproduction on the basis of the reproduced pilot signal, wherein the first head moves to a corresponding first track in the first area. A first sample-hold circuit that sequentially samples and holds the level difference information of a pair of pilot signals of another track that is detected at different first and second timings in synchronization with the detection of the recorded sync signal; Of the heads are synchronized with the detection of the sync signal recorded on the corresponding first track in the second area, and the first and second timing A second sample hold circuit for sequentially sampling and holding the level difference information of a pair of pilot signals of another track detected by the tracking, and the second head is recorded on the corresponding second track in the first area. A third sample-and-hold circuit that sequentially samples and holds the level difference information of the pair of pilot signals of the other tracks that are detected at the first and second timings, in synchronization with the detection of the sync signal, and the second head. In the second area is synchronized with the detection of the sync signal recorded in the corresponding second track, and the level difference information of the pair of pilot signals of the other tracks detected at the first and second timings is displayed. A fourth sample-and-hold circuit that sequentially performs sample-and-hold, and the output signals of the first to fourth sample-and-hold circuits are added And a tracking error detection circuit.