JPH0626050B2 - Tracking control circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control circuit in a helical scan type magnetic recording / reproducing apparatus, and more particularly to a DAT ATF.
The present invention relates to a tracking control circuit having means for preventing an error control state when performing control.

(Prior Art) DAT tracking control is performed by ATF control, and the principle thereof will be described with reference to FIGS. 4 to 6.

FIG. 6A is a perspective view showing the relationship between the traveling path of the rotating drum 40 of the DAT device and the magnetic tape 41, and the rotating drum 40 has two heads ha and hb (not shown) facing each other on its peripheral surface. 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 41 includes guide rollers 44 and 45 that regulate the movement in the width direction, the rotating drum 40, and the tilt pin 4.
The tape is formed on the tape path formed by the cables 2, 43 in the direction of arrow K at a predetermined tape speed v.

At this time, the winding angle of the magnetic tape 41 around the peripheral surface of the rotary drum 40 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. 6 (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. 4 is a partially enlarged view of the ATF area of the track pattern recorded on the magnetic tape, and this ATF area is divided into two parts E ₁ and E ₂ near both ends in the width direction of the magnetic tape.
A portion 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 the pilot signal s ₁ is recorded and blocks A and B in which sync signals s _{2 of} different frequencies are recorded corresponding to the 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 of} the F area E ₁ part,
And each block P ₄₂ , P _{52 of} the ATF area E ₂ ,
P ₃₂ is sequentially scanned, and the pilot signal s ₁ recorded in these blocks is sequentially reproduced.

FIG. 5A is 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 the ATF area E 1 similarly. _{Even in the second} copy, the reproduction levels of the blocks P ₃₂ and P ₅₂ are the same. This is because the head hb scans the track T ₃ in each of the ATF areas E ₁ and E ₂ and the track T _5.
Shows that the widths of scanning are the same, and the width center of the track T _{4 and} the width center of the head hb coincide with each other.

FIG. 11B shows a reproduction level waveform when the head hb scans in a 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 to the left. 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 is also increased or decreased in proportion to this deviation. Further, in FIG. 7C, the head hb is moved to 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 ₄ decreases.

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

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. 11 shows a block diagram of a tracking error signal detection unit used for conventional general ATF control.

In the figure, the envelope detection circuit 1 has a reproduction frequency of 130.67kH.
The z pilot signal s ₁ is input, and the level voltage signal s ₃ corresponding to this level is output to the subtractor 2 and the sample hold circuit 4. When the control circuit 5 receives the sync signal s ₂ and confirms that this frequency corresponds to the scanning head, it outputs pulsed control signals s ₆ and s ₇ at a predetermined timing. For example, in FIG. 4, when the head hb scans the track T ₄ , it reaches the block B ₄₁ to detect the sync signal s ₂ , and this frequency is set to the head hb.
When it is confirmed that it corresponds to b, the control signal s ₆ is output at the timing of t ₁ shown in FIG. 5, and the control signal s ₇ is output at the timing of t ₂ . The sample hold circuits 4 and 3 respectively hold the input signals by these control signals. Therefore, the sample hold circuit 4 holds the level voltage of the pilot signal detected from the block P ₅₁ of the right adjacent track T ₅ , and the sample hold circuit 3 outputs this level voltage and the block P ₃₁ of the left adjacent track T _{3 from} the block P _31. The level difference signal s ₄ with respect to the level voltage of the detected pilot signal is held. These hold operations are performed by the sync signal s corresponding to each head ha, hb.
_Since it is performed every time ₂ is detected, the hold signal output from the sample hold circuit 3 becomes the tracking error voltage signal s ₅ indicating a tracking error.

(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 part moves between the tracks, and level voltage signal s ₃ Figure 7 changes trajectory of each detection level _'(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') ( a) Shown in (b).

First, the level change of the sync signal s ₂ ′ shown in FIG. 7A will be described with reference to FIG. Block B
The level Vs ₄ of the sync signal s ₂ ′ detected at ₄₁ is
The center of the head hb is at the maximum level when scanning the center of the track T ₄ , and the direction is the adjacent track T _{5 in} the right direction (+ direction).
It does not change until it reaches the position d ₁ which is deviated by ¼ track, but when it is further deviated in the same direction, the head hb moves to the block B _41.
The level Vs ₄ decreases linearly due to the decrease in the width passing over, and eventually reaches the position d ₄ which is further deviated from the center of the track T ₅ by ¼ track and becomes 0 level. On the other hand, the level Vs ₆ of the sync signal s ₂ ′ detected in the block B ₆₁ of the track T ₆ linearly increases when the head hb passes the position d ₃ and reaches the maximum level at the position d ₆ and thereafter.
Similar level changes are repeated according to the + direction movement of the head hb.

In addition, the head hb moves to the left adjacent track T ₃ direction (-direction).
It is obvious 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. 7B and 4.

At this time, the control circuit 5 detects the pilot signal level of the adjacent track at predetermined timings t ₁ and t ₂ shown in FIG. 5 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 within the range w ₂ , from the time when it passes the block B ₂₁ where the sync signal is detected, and when it is within the range w ₄ , from the time when it passes the block B ₄₁ , the range w _{6 is} further increased. 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.

Note that once the control circuit 5 detects the sync signal, 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 sync circuit shown by the dotted line in FIG. No signal is 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.
Level Vp ₂ level voltage signal _{s 3} 'incorporated in ₂
(Indicated by a dotted line) is the detection level of the pilot signal detected by the head hb in the blocks P ₅₁ and P ₃₁ , respectively, and these are at the same level as shown in FIG. 7 (b). 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. The level Vp ₂ is zero reached the position _{d 1,} level Vp ₁ is maximum reached the position _{d 3.} Further beyond the position d ₃ , the head hb starts to detect the pilot signal of the block P ₆₁ at the timing t ₂ , so that the level Vp ₂ increases linearly again. And block B
_When the detection level of the sync signal of ₆₁ exceeds the position d _{7 at} which the sync signal becomes larger than the threshold value Vf, the above range w ₆ is reached, and the level voltage of the block P is reached at predetermined timings t ₁ and t ₂ from the time when the block B ₆₁ is passed. Take in the level of the signal s ₃ ′. Therefore, the level Vp ₁ is at this position d ₇
0 to the position d ₆ where the pilot signal of the block P ₇₁ is detected, while the level Vp ₂ is at the block P _71.
It becomes the detection level of the pilot signal of ₅₁ , maintains the maximum level up to the position d ₄ , and linearly decreases when exceeding this.
Eventually, when the scanning center of the head hb reaches the center of the track T ₆ , the levels Vp ₁ and Vp ₂ become the same level again,
At this time, each level is the detection level of the pilot signal detected by the head hb in the blocks P ₅₁ and P ₇₁ . Also, when the head hb is displaced in the − direction, the levels Vp ₁ and Vp ₂ of the level voltage signal s ₃ ′ are similarly detected, and it is clear that they change as shown in FIG.

Next, regarding the change locus of the level voltage signal s ₃ ′ detected when the scanning position of the head hb moves between the tracks in the ATF area E ₂ , FIGS. 7 (a) and 7 (c), Also, description will be made with reference to FIG.

At this time, the change 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 part, but the change locus of the level voltage signal s ₃ ′ is shown in FIG. As shown in (c), it is slightly different. That is, the head h
When the scanning center of b shifts from the center of the track T _{4 in} the + direction, the levels Vp ₁ and Vp ₂ change up to the position d ₃ as in the case of the ATF area E ₁ . However, since the block P to be detected at the timing t ₂ at this time does not exist even after passing the position d ₃ , the level Vp ₂ is at the ATF area E ₁
It does not increase like the part and keeps 0 state. On the other hand, the level Vp
₁ is the block P ₄₂ from the position d ₇ where the detection block of the sync signal is changed from B ₄₂ to B ₆₂ to the position d _4.
The detection level of the pilot signal is, and as shown in the figure, linearly decreases as the head hb moves in the + direction during this period.

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. That is, 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 the same as that 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 tracking error voltage signal s ₅ output from the sample hold circuit 3 in FIG. 11 is obtained by synchronizing with the levels Vp ₁ and Vp obtained in synchronization with the detection of the sync signal satisfying the above-mentioned conditions.
The difference voltage from p ₂ is (Vp ₁ −Vp ₂ ). FIG. 7 (d) shows a change locus obtained by drawing a dotted line from the solid line in FIG. 7 (b), and FIG. 7 (e) shows a change locus obtained by drawing a dotted line from the solid line in FIG. 7 (c). Therefore, when the scanning position of each head ha, hb moves between tracks, the head ha
The difference voltage Va ₁ obtained by detecting the corresponding sync signal in the F area E _{1 and} the difference voltage Vb ₂ obtained by detecting the corresponding sync signal in the ATF area E _{2 by} the head hb are shown in FIG. A difference voltage Vb ₁ obtained by detecting a corresponding sync signal of the ATF area E ₁ by the head hb moving on the locus and a difference voltage Va obtained by detecting a corresponding sync signal of the ATF area E _{2 by} the head ha. ₂ is the same figure (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.
Each head ha for scanning the ATF areas E ₁ and E ₂ when reproducing the ATF signal of the tape transported at a rotation speed of 2000 rpm for r and a tape velocity vp substantially equal to that at the time of recording,
The hb scanning positions have the same positional relationship with the center of the corresponding track Tr. in this case,
The difference voltages Vb ₁ and Va ₂ and the difference voltages Va ₁ and Vb ₂ on the change loci of FIGS. 7D and 7E are on the coaxial line and move.

On the other hand, when the heads ha and hb have a height difference, 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 difference. There is an error wh, and ATF area E
_{Also in 2} , the same amount of height error wh is generated. These errors wh are the difference voltage Va ₁ in FIGS. 7 (d) and 7 (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 the corresponding track center Tr of _{1 and} the corresponding track center Tr of the ATF area E ₂ causes a tilt error ws depending on the tilt, and the head hb also 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. 7D and 7E.

It should be noted that FIG. 6B shows a case where the angle relationship shown in FIG. 6B is inclined by −Δθ with respect to the angle θr at the time of recording. In this case, since the scanning direction of the head shown in FIG. 4 shifts clockwise, the relationship shown in FIGS. 7 (d) and 7 (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, if the tape speed fluctuates and the relative positional relationship between each head and the track shifts, the sample hold circuit 3
The difference voltages Va ₁ , Va ₂ , Vb ₁ and Vb ₂ of the tracking error voltage signal s ₅ output from the change loci of FIGS. 7D and 7E while maintaining the errors wh and ws with each other. Move along. For example, the tape speed V during recording
When the relationship between r and the tape speed Vp at the time of reproduction is Vr <Vp, it moves in the + direction, and conversely, when Vr> Vp, it moves in the − direction.

Generally, in the ATF control, the tape speed v is negatively feedback-controlled so that the average level of the tracking error voltage signal s ₅ becomes 0. Therefore, the level of each differential voltage is normally shown in FIGS. 7D and 7E. Be stable in position. However, in this case, there arises an inconvenience that the respective differential voltages become stable even if they have the positional relationship shown in FIG. That is, the height error wh and the tilt error ws are shown in FIG. 9A, and the tilt error ws is shown in FIG.
And the height error wh is shown in FIG. 6C, respectively. With reference to FIG.
The control movement will be described. Now, if the average level of the figure is positive, the ATF control - are moved in the direction difference voltage Va ₁ and positive voltage value Vb _1, and the negative voltage is decreased together but Va ₂ differential voltage Vb ₂ is Keep a constant value. Therefore, in this region, the sum of the positive voltage values decreases at a rate of change twice as much as the sum of the negative voltage values, so that the average level eventually becomes negative, and the average level is moved to the right by ATF control, and the average value is eventually reached in this region. Stabilizes to a position where the level is 0. This is because the track to be scanned by the head ha (tracks T ₁ , T ₃ in FIG. 4,
This corresponds to a state in which the head hb scans in the vicinity of the center of (T ₅ and T ₇ ), and the same can occur in the cases of FIGS. 8A and 8C.

The present invention avoids such an ATF error control condition,
It always enables normal control.

(Means for Solving the Problems) (1) By the helical scan method, the first and second heads arranged on the peripheral surface of the rotary drum are provided with the first and second heads in the vicinity of both ends of each track of the magnetic tape. 2 is a tracking control circuit for reproducing the pilot signal recorded in the area 2 and controlling the transfer speed of the magnetic tape based on the reproduced pilot signal, wherein the first head is the first head. A first level difference signal which indicates a level difference between a pair of pilot signals of another track which is detected at different first and second timings in synchronization with the detection of the sync signal recorded in the corresponding first track in the area. And the first head is synchronized with the detection of the sync signal recorded on the corresponding first track in the second area, and is detected at the first and second timings. And a second level difference signal indicating a level difference between a pair of pilot signals of another track, and the second head is synchronized with detection of a sync signal recorded in the corresponding second track in the first area. And a third level difference signal indicating the level difference between the pair of pilot signals of the other track detected at the first and second timings, and the second head to which the second head corresponds in the second area. Each level is synchronized with the detection of the sync signal recorded on the second track and the fourth level difference signal indicating the level difference between the pair of pilot signals of the other tracks detected at the first and second timings. An abnormal condition in which two of the levels of the first to fourth level difference signals are higher than a first threshold level and the other two are lower than a second threshold level lower than the first threshold level. At this time, an abnormal state detecting unit that outputs a detection signal indicating that this is an abnormal state, and a tape transfer speed changing unit that forcibly changes the transfer speed of the magnetic tape during the abnormal state based on the detection signal. Consists of.

(2) By the helical scan method, the pilot signals recorded in the first and second areas near both ends of each track of the magnetic tape are recorded by the first and second heads arranged on the peripheral surface of the rotary drum. A tracking control circuit for reproducing and controlling the transport speed of the magnetic tape based on the reproduced pilot signal, wherein the first head records on a corresponding first track in the first area. A first level difference signal indicating a level difference between a pair of pilot signals of another track, which are detected at different first and second timings in synchronization with the detection of the generated sync signal; A pair of pyros of another track which is synchronized with the detection of the sync signal recorded on the corresponding first track in the second area and which is detected at the first and second timings. A second level difference signal indicating the level difference of the sync signal, and the second head is synchronized with the detection of the sync signal recorded on the corresponding second track in the first area, and And a third level difference signal indicating a level difference between a pair of pilot signals of another track detected at a second timing, and the second head is recorded on a corresponding second track in the second area. A tracking error information output means that sequentially outputs a fourth level difference signal that is synchronized with the detection of the sync signal and that indicates the level difference between the pair of pilot signals of the other tracks detected at the first and second timings. A level change detection means for monitoring a level change between the level difference signals appearing before and after and outputting a detection signal indicating that the level has changed over a predetermined range, Based on the detection signal, and a tape transport speed variation means for forcedly varying the transport speed of the magnetic tape.

(Operation) Tracking control is prevented in a state where the correspondence between the first and second heads and the first and second tracks is incorrect.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of the present invention, and the same parts as those in FIG.

As is clear from the above description, the voltage of the tracking error voltage signal s ₅ output from the sample hold circuit (hereinafter referred to as SH circuit) 3 is changed by each head as it scans the ATF areas E ₁ and E ₂ . According to the differential voltage shown in FIG. 7, ... Vb ₂ , Va ₁ , Va ₂ , Vb ₁ , Vb ₂ , V
a ₁ ... Is updated in this order. The smoothing circuit 6 smoothes the tracking error voltage signal s ₅ and averages the average voltage signal s ₈
Is output to the adder 7.

A resistor R ₁ connected in series between the power supply voltages Vc and −Vc,
Reference voltages Vr ₁ and Vr ₂ formed by R ₂ and R ₃
Are respectively applied to the-input terminal of the comparator 8 and the + input terminal of the comparator 9. The comparator 8 becomes “H” when the level of the tracking error voltage signal (hereinafter referred to as TE voltage signal) s ₅ input to its + input terminal is higher than the reference voltage Vr ₁ , and conversely becomes “L” state when it is low. The determination signal s ₉ is output to the D (data) input terminal of the D-type flip-flop circuit (hereinafter referred to as the DFF circuit) 10. On the other hand, in the comparator 9, the level of the TE voltage signal s ₅ input to its negative input terminal is the reference voltage V
When it is lower than r ₂ , it is in the “H” state, and when it is higher than r _{2, the} determination signal s ₁₀ is in the “L” state.
Output to the input terminal.

The Q output terminals of the DFF circuits 10, 11 and 12 are connected to the D input terminals of the subsequent DFF circuits 11, 12 and 13, respectively, and further connected to the Q output terminal of the DFF circuit 13 and the input terminal of the counter 18. There is. Similarly, the Q output terminals of the DFF circuits 14, 15 and 16 are respectively connected to the D
It is connected to the D input terminals of the FF circuits 15, 16 and 17, and further connected to the input terminal of the counter 19 together with the Q output terminal of the DFF circuit 17. In addition, these DFF circuits 1
The control signal s ₆ output from the control circuit 5 is applied to each of the CK (clock) input terminals 0 to 17.

In the above configuration, the tracking error voltage signal s ₅
The operation when the voltage is sequentially updated based on the difference voltage shown in FIG. 8A will be described.

When the TE voltage signal s ₅ is the differential voltage Va ₁ , the determination signal s ₉
Is in the "H" state, and the determination signal s ₁₀ is in the "L" state. These respective states are taken into the DFF circuits 10 and 14 immediately before the TE voltage signal s ₅ becomes the differential voltage Va ₂ , that is, at the timing when the control signal s ₆ is output, and the Q output signals sd ₁ and sd ₅ are output. The states are "H" and "L", respectively. Next, when the control signal s ₇ is output and the TE voltage signal s ₅ becomes the differential voltage Va ₂ , the determination signals s ₉ and s are generated.
₁₀ changes to the "L" and "H" states, respectively. Then, when the next control signal s ₆ is output, this state changes to DFF.
At the same time as being taken into the circuits 10 and 14, each Q output signal s
The states of d ₁ and sd ₅ are taken into the DFF circuits 11 and 15, respectively, and the Q output signals sd ₁ , sd ₂ , sd ₅ and s are output.
d ₆ becomes “L”, “H”, “H”, “L”, respectively. Similarly, each time the difference voltage of the TE voltage signal s ₅ changes, the states of the determination signals s ₉ and s ₁₀ and the Q output state of each DFF circuit move to the DFF circuit of the next stage, and the difference voltage V
When the states of the determination signals corresponding to b ₁ and Vb ₂ are captured, the Q output signal group G of the DFF circuits 10 to 13
h becomes "L", "H", "L", "H" state, respectively, while the Q output signal group G1 of the DFF circuits 14 to 17 respectively has "H", "L", "H", "H". It becomes the L "state. After that, when the differential voltage of the TE voltage signal s ₅ is sequentially updated in the order described above, each state moves to the next stage, and
The states of the Q output signals sd ₄ and sd _{8 in} the final stage appear to move to the Q output signals sd ₁ and sd ₅ in the first stage.

From the above description, when the ATF control is in the error control state shown in FIG. 8, that is, two of the four differential voltages are the reference voltage Vr ₁
Higher, the lower the abnormal state than the other two reference voltages Vr _2, the in each Q output group, it is understood that always two "H" state respectively present.

The counter 18 monitors the number of “H” states of the input Q output signal group Gh, and outputs the detection signal s ₁₁ that is in the “H” state when the number is 2 or more to one input terminal of the AND circuit 20. . Similarly, the counter 19 monitors the number of "H" states of the Q output signal group G1 to be input,
The detection signal s ₁₂ which is in the “H” state when the number of times is one or more.
It outputs to the other input terminal of the D circuit 20. Therefore AND
The circuit 20 outputs the escape signal s ₁₃ which becomes the “H” state in the abnormal state to the adder 7.

The escape signal s ₁₃ output from the AND circuit 20 is
In the "H" state, it becomes a positive voltage of a predetermined level and becomes "L".
It is assumed that the level is set to 0 level.

Synthesized signal s ₁₄ which is obtained by adding the escape signal s ₁₃ and the average voltage signal s ₈ may, capstan motor driving circuit 100 for driving the capstan motor 101 is a tape transfer means
To enter. This capstan motor drive circuit 100
Is a configuration in which the capstan motor 101 is rotationally driven so that the level of the input composite signal s ₁₄ becomes 0 level, and the tape speed v is negatively feedback controlled by the ATF control system based on the composite signal s _14. There is.

Conventional ATF control generally involves the average voltage signal s ₈ described above.
Based on the tape speed v
In the above configuration, the escape signal s ₁₃ is added to the average voltage signal s ₈ . The escape signal s ₁₃ as described above, since the positive voltage of the "H" state upon an abnormal state, during which the tape speed v, each differential voltage as shown in FIG. 8 is - to forcibly moved in the direction However, the ATF control is performed by the average voltage signal s ₈ except in this abnormal state.

Therefore, according to the above configuration, it is possible to prevent the ATF control from becoming an error control state in which the ATF control becomes stable due to the positional relationship of each differential voltage shown in FIG.

FIG. 2 shows a block diagram of another embodiment of the present invention, and its operation will be described with reference to the timing chart of FIG. 9. The same parts as in FIG. Detailed description is omitted.

In the figure, 38 is a quaternary counter, and when the control signal s ₆ is input, the states of the output terminals 38 _{1 to} 38 ₄ connected to one input terminals of the AND circuits 21 to 24 are as shown in FIG. The "H" state is set in order. AND circuit 21 to
24 inputs the control signal s ₇ appearing in synchronization with the control signal s ₆ to the other input terminal, and AND signals s _{15 to} s
₁₈ are output to the control signal input terminals of the SH circuits 25 to 28, respectively. The SH circuits 25 to 28 each receive the level difference signal s ₄ and sample and hold at the timing of “H” of the AND signals s _{15 to} s ₁₈ . Therefore, each SH circuit outputs the TE voltage signals s _{51 to} s ₅₄ to the adder 29 in which the corresponding difference voltages are sequentially updated. This TE
The voltages of the voltage signals s _{51 to} s ₅₄ are shown in FIGS. 7 (d) and 7 (e).
9 (k) to 9 (n) show a state in which the voltage is sequentially updated on the basis of each stable differential voltage in the level state shown in FIG. In this case, the TE output from each SH circuit 25-28
The differential voltages Va ₁ , Va ₂ , Vb ₁ , and Vb ₂ of the voltage signals do not change, but the change in tape speed v causes a change in FIG. 7 (d).
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.

Further, the adder 29 outputs the added voltage signal s ₁₉ obtained by adding the TE voltage signals s _{51 to} s _54. The voltage level of the added voltage signal s ₁₉ is the differential voltage V that is sequentially updated.
proportional to the average level of a ₁ , Va ₂ , Vb ₁ , and Vb ₂ ,
This corresponds to the level of the average voltage signal s ₈ output from the smoothing circuit 6 shown in FIG.

On the other hand, the escape signal s ₁₃ is formed in the same process as the embodiment of FIG. 1 described above, but the configuration is slightly different. That is, the reference voltages Vr ₁ ,
The signal compared with Vr ₂ becomes the level difference signal s ₄ , and the control signal s ₇ is applied to each CK input terminal of the DFF circuits 10 to 17. In this case, the DFF circuit 10,
When the determination signals s ₉ and s ₁₀ applied to the D input terminal 14 are taken in at the rising timing of the control signal s ₇ , the level difference signal s ₄ has the difference voltages Va ₁ , Va ₂ , Vb ₁ and Vb ₂
It is in the state of. Therefore, the output timing of the escape signal s ₁₃ to be formed is substantially the same, although there is a slight difference from the configuration of the embodiment shown in FIG.

According to the embodiment shown in FIG. 2, since the smoothing circuit 6 shown in FIG. 1 is unnecessary, it is possible to perform ATF control with a quick response.

FIG. 3 shows a block diagram of still another embodiment of the present invention.
The operation will be described with reference to the timing chart of FIG. 0, but the same parts as those of FIGS. 1 and 2 are designated by the same reference numerals and detailed description thereof will be omitted.

One input terminal of the AND circuit 21 to 24 shown in the figure are respectively connected to the output terminal ₃₈ 1 to 38 ₄ of the quaternary counter 38, the other input terminal together, NOR circuits 32 and 33
Is connected to the output part of the flip-flop circuit 37 which inputs the control signals s ₆ and s ₇ to its input part. One of the fixed terminals of the switches 34, 35, 36 is connected to the output terminals of the AND circuits 21, 22, 23, respectively, and the other fixed terminals thereof are both connected to the output terminal of the AND circuit 24. The control signal input terminals of the SH circuits 25, 26 and 27 are connected to the movable terminals of the switches 34, 35 and 36, respectively, and the control signal input terminals of the SH circuit 28 are directly connected to the output terminals of the AND circuit 24. Further, a TE voltage signal s ₅ is applied to an input terminal of a Schmitt trigger circuit (hereinafter referred to as ST circuit) 30, and an output terminal thereof is a mono multivibrator (hereinafter referred to as monomulti) 3
1 is connected to each control signal input terminal of the switches 34, 35 and 36.

In the above configuration, first, the circuit operation in the state where the movable terminals of the switches 34, 35 and 36 are connected to one fixed terminal as shown in the figure will be described.

In this case, the signal waveform at each portion of the circuit is as shown in the timing chart of FIG. That is, the output signal s ₂₀ of the flip-flop circuit is inverted in synchronization with the pulses of the control signals s ₆ and s ₇ , and the output signal s ₂₀ and the quaternary counter 3
S _{21 to} s ₂₄ which are AND signals with the output signal of 8 are
As shown in the figure, even though the states gradually become "H", the rising edge thereof is synchronized with the control signal s ₇ and the falling edge thereof is the control signal s _7.
Synchronize to ₆ .

On the other hand, FIG. 1A shows a state in which the voltage of the TE voltage signal s ₅ is sequentially updated based on the difference voltage in FIGS. 7D and 7E. Since the SH circuits 25 to 28 sample the TE voltage signal s ₅ during “H” of the corresponding AND signals s _{21 to} s ₂₄ , the SH circuits 25 to 28 respectively.
The voltage levels of the TE voltage signals s _{51 to} s ₅₄ output by the differential voltages Va ₁ , Va ₂ , and V are sequentially updated.
The levels become b ₁ and Vb ₂ and are output to the adder 29 in exactly the same state as the TE voltage signals s _{51 to} s ₅₄ shown in FIG.

Next, the ST circuit 30, the monomulti 31, and the switches 34 to 3
The operation of No. 6 will be described.

FIG. 10 (m) shows the state of the TE voltage signal s ₅ when each differential voltage is in the position of the abnormal state shown in FIG. 8 (a). The position where the ATF control is in the error control state, or When it is in the vicinity, the level change width of the TE voltage signal s ₅ becomes large, and as shown in the figure, the predetermined threshold voltages Vh, Vl
Change beyond. The ST circuit 30 has this threshold and T
When the E voltage signal s ₅ exceeds this threshold value at the time of level inversion, the output signal s ₂₅ whose state changes is output. Mono Multi 3
1 outputs the control signal s ₂₆ that is in the “H” state for the predetermined period T in synchronization with the change in the state of the output signal s ₂₅ . The switches 34 to 36 connect each movable terminal to the other fixed terminal during the "H" state. Therefore,
Each SH circuit 25 during the “H” state of the control signal s ₂₆
28 to 28 are both controlled by the AND signal s ₂₄ , and in synchronization with this, the difference voltage Vb ₂ is sampled and output. However, during this period, each SH circuit operates at the difference voltage Vb ₂
Must be sampled reliably, so that the period T is
As shown in the same figure, it is necessary to set the period longer than the period during which at least four types of differential voltages are output.

As described above, when the ATF control is in the error control state and the control signal s ₂₆ is once in the “H” state, each sample and hold circuit simultaneously synchronizes with the AND signal s ₂₄ and outputs the difference voltage Vb ₂ simultaneously. Therefore, the voltage level of the added voltage signal s ₁₄ output from the adder 29 is temporarily 4
・ It becomes Vb ₂ . Therefore, when the TE voltage signal s ₅ changes as shown in FIG. 10 (m), the added voltage signal s at this time is
₁₄ becomes a negative voltage, and the tape speed v is
Since each differential voltage shown in FIG. 8 (a) is controlled so as to forcibly move to the right, it is possible to prevent the ATF control from entering the error control state.

The present invention is not limited to the above embodiment,
For example, instead of the ST circuit 30 of FIG. 3, a TE voltage signal s
A circuit may be provided that outputs a detection pulse when the change width of the voltage level ₅ is equal to or larger than a predetermined value. Further, in the figure, the switches 34 to 3 are controlled by the control signal s ₂₆ .
Obviously, instead of switching 6, the predetermined pulse voltage signal based on this control signal s ₂₆ may be applied to the summed voltage signal s ₁₄ .

Further, the tape transfer speed is forcibly changed based on the escape signal s ₁₃ in the embodiment shown in FIGS. 1 and 2 and based on the control signal s ₂₆ in the embodiment shown in FIG. Therefore, for example,
Based on these signals, various modes are obtained, such as providing a means for increasing the load of the capstan motor and temporarily changing the rotation speed.

(Effects of the Invention) When reproducing a DAT tape recorded by another model, there is a height error between the recording head and the reproducing head,
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, and as a result, ATF control may be performed in a state in which the correspondence between the head and the track is incorrect. However, according to the present invention,
Since this erroneous state or a possible state is detected to avoid this abnormal control state, normal ATF control is always possible.

[Brief description of drawings]

1 to 3 are configuration diagrams showing an embodiment of the present invention,
4 to 8 are diagrams used for explaining the present invention, FIGS. 9 and 10 are timing chart diagrams showing signal waveforms of respective parts of FIGS. 2 and 3, and FIG. 11 is a conventional diagram. A
It is a block diagram which shows the tracking error signal detection part used for TF control. 1 ... Envelope detection circuit, 2 ... Subtractor, 34,
25-28 ...... Sample hold circuit, 5 ... Control circuit, 6 ... Smoothing circuit, 7,29 ... Adder, 8,9 ...
Comparator, 10-17 ... D-type flip-flop circuit, 18, 19 ... Counter, 20-24 ... AND circuit, 30 ... Schmidt trigger circuit, 31 ... Mono multivibrator, 32, 33 ... NOR circuit, 34, 3
5, 36 ... Switch, 37 ... Flip-flop circuit, 38 ... Quaternary counter, 100 ... Capstan motor drive circuit, 101 ... Capstan motor.

Claims (2)

[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 control circuit for reproducing a signal and controlling the transfer speed of the magnetic tape based on the reproduced pilot signal, wherein the first head corresponds to the first track in the first area. A first level difference signal indicating a level difference between a pair of pilot signals of another track which are detected at different first and second timings in synchronization with the detection of the sync signal recorded on the first head; , A pair of other tracks that are synchronized with the detection of the sync signal recorded on the corresponding first track in the second area and that are detected at the first and second timings. A second level difference signal indicating the level difference of the ilot signal, and the second head is synchronized with the detection of the sync signal recorded on the corresponding second track in the first area, and And a third level difference signal indicating a level difference between a pair of pilot signals of another track detected at a second timing, and the second head is recorded on a corresponding second track in the second area. In synchronization with the detection of the sync signal, and monitoring the respective levels of the fourth level difference signal indicating the level difference between the pair of pilot signals of the other tracks detected at the first and second timings, the first level To an abnormal state in which two of the respective levels of the fourth level difference signal are higher than the first threshold level and the other two are lower than the second threshold level lower than the first threshold, this abnormal state. An abnormal state detecting means for outputting a detection signal indicating that, and a tape transfer speed changing means for forcibly changing the transfer speed of the magnetic tape in the abnormal state based on the detection signal. Tracking control circuit. 2. 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 control circuit for reproducing a signal and controlling the transfer speed of the magnetic tape based on the reproduced pilot signal, wherein the first head corresponds to the first track in the first area. A first level difference signal indicating a level difference between a pair of pilot signals of another track which are detected at different first and second timings in synchronization with the detection of the sync signal recorded on the first head; , A pair of other tracks that are synchronized with the detection of the sync signal recorded on the corresponding first track in the second area and that are detected at the first and second timings. A second level difference signal indicating the level difference of the ilot signal, and the second head is synchronized with the detection of the sync signal recorded on the corresponding second track in the first area, and And a third level difference signal indicating a level difference between a pair of pilot signals of another track detected at a second timing, and the second head is recorded on a corresponding second track in the second area. A tracking error information output means that sequentially outputs a fourth level difference signal that is synchronized with the detection of the sync signal and that indicates the level difference between the pair of pilot signals of the other tracks detected at the first and second timings. Level change detecting means for monitoring a level change between the level difference signals appearing before and after and outputting a detection signal indicating that the level has changed over a predetermined range or more, And a tape transfer speed changing means for forcibly changing the transfer speed of the magnetic tape based on the detection signal.